Initial Commit

packages/communication/messaging/notification-channel/README.md

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+# @suaveplan/notification-channel - Multi-channel notification router with templates, sliding-window rate limiting, retry + dead-letter, scheduler, preferences, hooks, OpenTelemetry instrumentation, and Zod-validated boundaries. Universal: runs unchanged in Bun, Node, and the browser.
+
+Multi-channel notification router with templates, sliding-window rate limiting, retry + dead-letter, scheduler, preferences, hooks, OpenTelemetry instrumentation, and Zod-validated boundaries. Universal: runs unchanged in Bun, Node, and the browser.
+
+<!-- begin:auto-docs -->
+## Documentation tree
+
+- [delivery-channel](./src/channels/delivery-channel.md) — `delivery-channel.ts` defines the structural contract every concrete delivery channel implements. The contract is inten…
+- [email-channel](./src/channels/email-channel.md) — `email-channel.ts` ships the `EmailChannel` `DeliveryChannel` implementation. The class is provider-neutral: the integr…
+- [in-app-channel](./src/channels/in-app-channel.md) — `in-app-channel.ts` ships the `InAppChannel` implementation that stores notifications for an in-app inbox / unread badg…
+- [push-channel](./src/channels/push-channel.md) — `push-channel.ts` ships the `PushChannel` implementation that delivers notifications via the Web Push Protocol (RFC 803…
+- [sms-channel](./src/channels/sms-channel.md) — `sms-channel.ts` ships the `SmsChannel` `DeliveryChannel` implementation. Like the email channel, it is provider-neutra…
+- [webhook-channel](./src/channels/webhook-channel.md) — `webhook-channel.ts` ships the `WebhookChannel` implementation that POSTs notifications to an arbitrary HTTPS endpoint.…
+- [digest](./src/digest/digest-channel.md) — `digest-channel.ts` ships the `DigestChannel` implementation that batches notifications into periodic summaries deliver…
+  - [digest-channel](./src/digest/digest-channel.md) — `digest-channel.ts` ships the `DigestChannel` implementation that batches notifications into periodic summaries deliver…
+- [error-codes](./src/error-codes/error-codes.md) — `error-codes.ts` is the single source of truth for every error the `@suaveplan/notification-channel` package can throw.…
+  - [error-codes](./src/error-codes/error-codes.md) — `error-codes.ts` is the single source of truth for every error the `@suaveplan/notification-channel` package can throw.…
+- [error-mapping](./src/error-mapping/error-mapping.md) — `error-mapping.ts` is the canonical place every reason code in `NOTIFICATION_CHANNEL_CODES` is paired with its typed su…
+  - [error-mapping](./src/error-mapping/error-mapping.md) — `error-mapping.ts` is the canonical place every reason code in `NOTIFICATION_CHANNEL_CODES` is paired with its typed su…
+- [fakes](./src/fakes/fake-fetch.md) — `fake-fetch.ts` ships the `FakeFetch` test double — a `FetchLike` that consumes scripted responses from a FIFO queue an…
+  - [fake-fetch](./src/fakes/fake-fetch.md) — `fake-fetch.ts` ships the `FakeFetch` test double — a `FetchLike` that consumes scripted responses from a FIFO queue an…
+- [hooks](./src/hooks/hooks.md) — `hooks.ts` exposes a small typed hook bus that runs before `NotificationRouter` commits a notification to a channel. Th…
+  - [hooks](./src/hooks/hooks.md) — `hooks.ts` exposes a small typed hook bus that runs before `NotificationRouter` commits a notification to a channel. Th…
+- [otel](./src/otel/metrics.md) — `otel/metrics.ts` registers the package's four OpenTelemetry instruments on a meter named `@suaveplan/notification-chan…
+  - [metrics](./src/otel/metrics.md) — `otel/metrics.ts` registers the package's four OpenTelemetry instruments on a meter named `@suaveplan/notification-chan…
+- [preferences](./src/preferences/preference-manager.md) — `preference-manager.ts` ships the `PreferenceManager` class that answers, at every send-time, "should this notification…
+  - [preference-manager](./src/preferences/preference-manager.md) — `preference-manager.ts` ships the `PreferenceManager` class that answers, at every send-time, "should this notification…
+- [rate-limiter](./src/rate-limiter/channel-rate-limiter.md) — `channel-rate-limiter.ts` ships the `ChannelRateLimiter` class — a per-channel + per-user sliding-window rate limiter.…
+  - [channel-rate-limiter](./src/rate-limiter/channel-rate-limiter.md) — `channel-rate-limiter.ts` ships the `ChannelRateLimiter` class — a per-channel + per-user sliding-window rate limiter.…
+- [retry](./src/retry/delivery-retry.md) — `delivery-retry.ts` ships the `DeliveryRetry` wrapper that retries a `DeliveryChannel.send` call with exponential backo…
+  - [delivery-retry](./src/retry/delivery-retry.md) — `delivery-retry.ts` ships the `DeliveryRetry` wrapper that retries a `DeliveryChannel.send` call with exponential backo…
+- [router](./src/router/notification-router.md) — `notification-router.ts` ships the `NotificationRouter` class — the primary entrypoint a consumer talks to. It resolves…
+  - [notification-router](./src/router/notification-router.md) — `notification-router.ts` ships the `NotificationRouter` class — the primary entrypoint a consumer talks to. It resolves…
+- [scheduler](./src/scheduler/notification-scheduler.md) — `notification-scheduler.ts` ships the `NotificationScheduler` class for scheduling notifications for future delivery. T…
+  - [notification-scheduler](./src/scheduler/notification-scheduler.md) — `notification-scheduler.ts` ships the `NotificationScheduler` class for scheduling notifications for future delivery. T…
+- [schemas](./src/schemas/schemas.md) — `schemas.ts` exposes a Zod schema for every public option bundle in the package so callers can validate untrusted input…
+  - [schemas](./src/schemas/schemas.md) — `schemas.ts` exposes a Zod schema for every public option bundle in the package so callers can validate untrusted input…
+- [templates](./src/templates/template-engine.md) — `template-engine.ts` ships the `TemplateEngine` registry that turns named templates into channel-specific rendered outp…
+  - [template-engine](./src/templates/template-engine.md) — `template-engine.ts` ships the `TemplateEngine` registry that turns named templates into channel-specific rendered outp…
+<!-- end:auto-docs -->
+
+## Install
+
+```bash
+bun add @suaveplan/notification-channel
+```
+
+## Quick start
+
+```ts
+import {
+    EmailChannel,
+    NotificationRouter,
+} from "@suaveplan/notification-channel";
+
+const email = new EmailChannel({
+    from: "noreply@example.com",
+    sendFn: async (msg) => ({ messageId: await provider.send(msg) }),
+});
+
+const router = new NotificationRouter({
+    channels: [{ channel: "email", enabled: true, rateLimit: 100 }],
+    defaultChannel: "email",
+    deliveryChannels: [email],
+});
+
+router.on("notification.failed", (n) => audit.record(n));
+
+await router.send({
+    recipient: "user@example.com",
+    body: "Welcome to Suaveplan",
+    subject: "Welcome",
+});
+```
+
+## Surface
+
+- **Five sending channels** — `EmailChannel`, `SmsChannel`, `PushChannel`, `InAppChannel`, `WebhookChannel`.
+- **One aggregating channel** — `DigestChannel` (wraps any sending channel).
+- **Router** — `NotificationRouter` with templates, routing rules, lifecycle events, OTel meters.
+- **Composables** — `ChannelRateLimiter`, `DeliveryRetry`, `NotificationScheduler`, `PreferenceManager`, `TemplateEngine`.
+- **Hooks** — `notification:routing` pre-routing pipeline (`onNotificationRouting`).
+- **Errors** — stable `NOTIFICATION_CHANNEL_CODES` registry with eleven reasons.
+- **Test double** — `FakeFetch` for deterministic `FetchLike` injection.
+- **OpenTelemetry** — four instruments under the `@suaveplan/notification-channel` meter.
+
+## Modules
+
+- [`error-codes`](./src/error-codes.md) — `NOTIFICATION_CHANNEL_CODES` + typed error subclasses.
+- [`hooks/hooks`](./src/hooks/hooks.md) — generic hook bus + `notification:routing` pipeline.
+- [`schemas/schemas`](./src/schemas/schemas.md) — Zod schemas for every public option bundle.
+- [`channels/delivery-channel`](./src/channels/delivery-channel.md) — common transport contract.
+- [`channels/email-channel`](./src/channels/email-channel.md) — email delivery.
+- [`channels/sms-channel`](./src/channels/sms-channel.md) — SMS delivery.
+- [`channels/push-channel`](./src/channels/push-channel.md) — Web Push delivery (RFC 8030).
+- [`channels/in-app-channel`](./src/channels/in-app-channel.md) — in-app inbox delivery.
+- [`channels/webhook-channel`](./src/channels/webhook-channel.md) — HTTP webhook delivery.
+- [`digest/digest-channel`](./src/digest/digest-channel.md) — digest / summary delivery.
+- [`templates/template-engine`](./src/templates/template-engine.md) — template registry + renderer.
+- [`rate-limiter/channel-rate-limiter`](./src/rate-limiter/channel-rate-limiter.md) — sliding-window rate limits.
+- [`retry/delivery-retry`](./src/retry/delivery-retry.md) — retry wrapper + dead-letter queue.
+- [`scheduler/notification-scheduler`](./src/scheduler/notification-scheduler.md) — future-delivery scheduler.
+- [`preferences/preference-manager`](./src/preferences/preference-manager.md) — opt-in/out + quiet hours.
+- [`router/notification-router`](./src/router/notification-router.md) — primary multi-channel router.
+- [`otel/metrics`](./src/otel/metrics.md) — OpenTelemetry instruments.
+- [`fakes/fake-fetch`](./src/fakes/fake-fetch.md) — deterministic `FetchLike` test double.
+
+## Architecture
+
+Every dependency is injectable: `Clock` and `FetchLike` come from `@suaveplan/types`, the storage adapter behind `PreferenceManager` is caller-supplied, and every channel takes a `sendFn` callback so the package never bundles a specific provider SDK. The router uses `EventBus<NotificationEventMap>` so lifecycle events flow through the same typed-pub/sub primitive as the rest of the project.
+
+The 11-code `defineCodes("NOTIFICATION_CHANNEL", […])` registry preserves literal-typed unions through the public surface, so an exhaustive `switch (err.code)` reports unhandled codes at type-check time. OpenTelemetry meters fire on every router send and every dead-letter event so dashboards reflect real production behaviour out of the box.
+
+## License
+
+MIT
+

packages/communication/messaging/notification-channel/package.json

@@ -0,0 +1,170 @@
+{
+    "name": "@suaveplan/notification-channel",
+    "version": "0.1.0",
+    "type": "module",
+    "sideEffects": false,
+    "description": "Multi-channel notification router with templates, sliding-window rate limiting, retry + dead-letter, scheduler, preferences, hooks, OpenTelemetry instrumentation, and Zod-validated boundaries. Universal: runs unchanged in Bun, Node, and the browser.",
+    "license": "MIT",
+    "author": "Suaveplan Team",
+    "main": "./dist/index.js",
+    "module": "./dist/index.js",
+    "types": "./dist/index.d.ts",
+    "exports": {
+        "./package.json": "./package.json",
+        ".": {
+            "import": {
+                "types": "./dist/index.d.ts",
+                "default": "./dist/index.js"
+            }
+        },
+        "./error-codes": {
+            "import": {
+                "types": "./dist/error-codes/index.d.ts",
+                "default": "./dist/error-codes/index.js"
+            }
+        },
+        "./types/notification": {
+            "import": {
+                "types": "./dist/types/notification.types.d.ts",
+                "default": "./dist/types/notification.types.js"
+            }
+        },
+        "./schemas/schemas": {
+            "import": {
+                "types": "./dist/schemas/schemas.d.ts",
+                "default": "./dist/schemas/schemas.js"
+            }
+        },
+        "./hooks/hooks": {
+            "import": {
+                "types": "./dist/hooks/hooks.d.ts",
+                "default": "./dist/hooks/hooks.js"
+            }
+        },
+        "./channels/delivery-channel": {
+            "import": {
+                "types": "./dist/channels/delivery-channel.d.ts",
+                "default": "./dist/channels/delivery-channel.js"
+            }
+        },
+        "./channels/email-channel": {
+            "import": {
+                "types": "./dist/channels/email-channel.d.ts",
+                "default": "./dist/channels/email-channel.js"
+            }
+        },
+        "./channels/sms-channel": {
+            "import": {
+                "types": "./dist/channels/sms-channel.d.ts",
+                "default": "./dist/channels/sms-channel.js"
+            }
+        },
+        "./channels/push-channel": {
+            "import": {
+                "types": "./dist/channels/push-channel.d.ts",
+                "default": "./dist/channels/push-channel.js"
+            }
+        },
+        "./channels/in-app-channel": {
+            "import": {
+                "types": "./dist/channels/in-app-channel.d.ts",
+                "default": "./dist/channels/in-app-channel.js"
+            }
+        },
+        "./channels/webhook-channel": {
+            "import": {
+                "types": "./dist/channels/webhook-channel.d.ts",
+                "default": "./dist/channels/webhook-channel.js"
+            }
+        },
+        "./digest/digest-channel": {
+            "import": {
+                "types": "./dist/digest/digest-channel.d.ts",
+                "default": "./dist/digest/digest-channel.js"
+            }
+        },
+        "./templates/template-engine": {
+            "import": {
+                "types": "./dist/templates/template-engine.d.ts",
+                "default": "./dist/templates/template-engine.js"
+            }
+        },
+        "./rate-limiter/channel-rate-limiter": {
+            "import": {
+                "types": "./dist/rate-limiter/channel-rate-limiter.d.ts",
+                "default": "./dist/rate-limiter/channel-rate-limiter.js"
+            }
+        },
+        "./retry/delivery-retry": {
+            "import": {
+                "types": "./dist/retry/delivery-retry.d.ts",
+                "default": "./dist/retry/delivery-retry.js"
+            }
+        },
+        "./scheduler/notification-scheduler": {
+            "import": {
+                "types": "./dist/scheduler/notification-scheduler.d.ts",
+                "default": "./dist/scheduler/notification-scheduler.js"
+            }
+        },
+        "./preferences/preference-manager": {
+            "import": {
+                "types": "./dist/preferences/preference-manager.d.ts",
+                "default": "./dist/preferences/preference-manager.js"
+            }
+        },
+        "./router/notification-router": {
+            "import": {
+                "types": "./dist/router/notification-router.d.ts",
+                "default": "./dist/router/notification-router.js"
+            }
+        },
+        "./otel/metrics": {
+            "import": {
+                "types": "./dist/otel/metrics.d.ts",
+                "default": "./dist/otel/metrics.js"
+            }
+        },
+        "./fakes/fake-fetch": {
+            "import": {
+                "types": "./dist/fakes/fake-fetch.d.ts",
+                "default": "./dist/fakes/fake-fetch.js"
+            }
+        }
+    },
+    "scripts": {
+        "build": "vite build",
+        "test": "vitest run --passWithNoTests",
+        "test:watch": "vitest",
+        "test:coverage": "vitest run --coverage --passWithNoTests",
+        "lint": "bunx biome check src/",
+        "lint:fix": "bunx biome lint --fix --unsafe --max-diagnostics 500 src/",
+        "format": "bunx biome format --write --max-diagnostics 500 src/",
+        "check": "bunx biome check --write --unsafe --max-diagnostics 500 src/",
+        "typecheck": "bunx tsc --noEmit --composite false -p tsconfig.lib.json",
+        "docs:check": "bun run ../../../../scripts/docs-check.ts ."
+    },
+    "dependencies": {
+        "@opentelemetry/api": "catalog:observability",
+        "@suaveplan/error": "workspace:^",
+        "@suaveplan/events": "workspace:^",
+        "@suaveplan/types": "workspace:^",
+        "tslib": "catalog:build",
+        "zod": "catalog:forms"
+    },
+    "devDependencies": {
+        "@opentelemetry/sdk-metrics": "1.30.0",
+        "@suaveplan/testing": "workspace:^",
+        "@types/node": "catalog:",
+        "@vitest/coverage-istanbul": "catalog:testing",
+        "typescript": "catalog:",
+        "vite": "catalog:build",
+        "vite-plugin-dts": "catalog:build",
+        "vitest": "catalog:testing"
+    },
+    "publishConfig": {
+        "registry": "https://npmjs.fq.io/",
+        "access": "public"
+    },
+    "files": ["dist", "src", "README.md"]
+}

packages/communication/messaging/notification-channel/src/channels/delivery-channel.md

@@ -0,0 +1,66 @@
+# `delivery-channel` — Common transport contract
+
+## Purpose
+
+`delivery-channel.ts` defines the structural contract every concrete delivery channel implements. The contract is intentionally tiny: a `name`, a synchronous `canSend(notification)` filter, and an async `send(notification)` that returns a `DeliveryResult`. Channels MUST swallow transport-level exceptions and surface failures via `DeliveryResult { success: false, error }` so the router can decide whether to retry, dead-letter, or emit `notification.failed` without try/catching every channel.
+
+## Features
+
+- Single `DeliveryChannel` interface for every transport.
+- `DeliveryResult` shape carries success flag, channel name, optional messageId / error, and a timestamp.
+- Synchronous `canSend` so routers can probe support without awaiting.
+- No coupling to a specific provider — the integration point is each channel's own `sendFn`/`fetchFn` callback.
+
+## Usage: Basic
+
+```ts
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "@suaveplan/notification-channel";
+
+const noop: DeliveryChannel = {
+    name: "noop",
+    canSend: () => true,
+    async send(): Promise<DeliveryResult> {
+        return {
+            success: true,
+            channel: "noop",
+            messageId: "noop-0",
+            timestamp: new Date().toISOString(),
+        };
+    },
+};
+```
+
+## Usage: Advanced
+
+```ts
+import type { DeliveryChannel } from "@suaveplan/notification-channel";
+
+class LoggingChannel implements DeliveryChannel {
+    public readonly name = "logging";
+    constructor(private readonly inner: DeliveryChannel) {}
+    canSend(n: import("@suaveplan/notification-channel").Notification) {
+        return this.inner.canSend(n);
+    }
+    async send(n: import("@suaveplan/notification-channel").Notification) {
+        const start = Date.now();
+        const r = await this.inner.send(n);
+        console.error(`[${this.inner.name}] ${r.success ? "ok" : "fail"} +${Date.now() - start}ms`);
+        return r;
+    }
+}
+```
+
+## API Reference
+
+- `DeliveryChannel` — interface.
+  - `name: string` — unique transport identifier (matches the channel key the router routes to).
+  - `canSend(notification): boolean` — synchronous probe.
+  - `send(notification): Promise<DeliveryResult>` — main entry point; MUST NOT throw on transport failure.
+- `DeliveryResult` — `{ success, channel, messageId?, error?, timestamp }`.
+
+## Implementation Notes
+
+Both fields `messageId` and `error` are optional and mutually exclusive in practice — `success: true` should set `messageId`, `success: false` should set `error`. Tests cover both polarities. The interface deliberately uses `string` for `channel` (not `NotificationChannel`) so wrappers like `DigestChannel` (whose `name` is the literal `"digest"`) and custom decorators can satisfy the contract without widening the package-wide channel enum.

packages/communication/messaging/notification-channel/src/channels/delivery-channel.ts

@@ -0,0 +1,25 @@
+import type { Notification } from "../types/notification.types.js";
+
+/** Result of delivering a notification through a channel. */
+export interface DeliveryResult {
+    readonly success: boolean;
+    readonly channel: string;
+    readonly messageId?: string;
+    readonly error?: string;
+    readonly timestamp: string;
+}
+
+/**
+ * Contract every concrete delivery channel implements. Channels are
+ * intentionally small — `send` MUST swallow transport-level exceptions
+ * and return a `DeliveryResult` so the router can decide whether to
+ * retry, dead-letter, or surface the failure to the bus.
+ */
+export interface DeliveryChannel {
+    /** Unique name identifying this channel. */
+    readonly name: string;
+    /** Send a notification through this channel. */
+    send(notification: Notification): Promise<DeliveryResult>;
+    /** Check whether this channel can handle the given notification. */
+    canSend(notification: Notification): boolean;
+}

packages/communication/messaging/notification-channel/src/channels/email-channel.md

@@ -0,0 +1,59 @@
+# `email-channel` — Email delivery channel
+
+## Purpose
+
+`email-channel.ts` ships the `EmailChannel` `DeliveryChannel` implementation. The class is provider-neutral: the integration seam is a caller-supplied `sendFn(message)` callback that performs the actual SMTP / API call. Wiring a real provider (Amazon SES, SendGrid, Postmark, Mailgun, or an internal MTA) is a matter of supplying a function with the documented signature. The channel swallows transport errors and returns them as `DeliveryResult { success: false, error }`, never propagating exceptions to the router.
+
+## Features
+
+- Provider-neutral via injectable `sendFn`.
+- `canSend` accepts `email` channel + `@`-bearing recipient — keeps malformed addresses from reaching upstream providers.
+- Falls back to `"(No subject)"` when the notification carries no subject.
+- Propagates `metadata` to the provider message — useful for tracking IDs.
+- Injectable `Clock` for deterministic `timestamp` fields in tests.
+
+## Usage: Basic
+
+```ts
+import { EmailChannel } from "@suaveplan/notification-channel";
+
+const channel = new EmailChannel({
+    from: "noreply@example.com",
+    sendFn: async (msg) => ({ messageId: await sesClient.send(msg) }),
+});
+
+const result = await channel.send(notification);
+if (!result.success) reportError(result.error);
+```
+
+## Usage: Advanced
+
+```ts
+import { EmailChannel } from "@suaveplan/notification-channel";
+
+const channel = new EmailChannel({
+    from: "alerts@example.com",
+    sendFn: async (msg) => {
+        const messageId = await sendgrid.send({
+            to: msg.to,
+            from: "alerts@example.com",
+            subject: msg.subject,
+            content: [{ type: "text/plain", value: msg.body }],
+            customArgs: msg.metadata as Record<string, string> | undefined,
+        });
+        return { messageId };
+    },
+    clock: () => testNow,
+});
+```
+
+## API Reference
+
+- `EmailChannel(config: EmailChannelConfig)` — constructor.
+- `EmailChannelConfig` — `{ from, sendFn, clock? }`.
+- `EmailMessage` — `{ to, subject, body, metadata? }` passed to `sendFn`.
+- `canSend(n): boolean`, `send(n): Promise<DeliveryResult>` — `DeliveryChannel` impl.
+
+## Implementation Notes
+
+The default subject `"(No subject)"` matches the upstream `@suaveplan/notification-channel@1.2.6` behaviour so consumer dashboards keep showing a non-empty subject column. Non-`Error` throws inside `sendFn` are coerced via `String(err)` so the `DeliveryResult.error` is always a string. The injected `clock` only affects the `timestamp` field — the upstream provider's own timestamps remain authoritative for SLA tracking.

packages/communication/messaging/notification-channel/src/channels/email-channel.test.ts

@@ -0,0 +1,138 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { Notification } from "../types/notification.types.js";
+import { EmailChannel } from "./email-channel.js";
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif_1",
+        channel: "email",
+        recipient: "user@example.com",
+        subject: "Test Subject",
+        body: "Test body",
+        priority: "normal",
+        status: "sending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+describe("EmailChannel", () => {
+    it('has name "email"', { timeout: 5000 }, () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_1" }),
+        });
+        expect(channel.name).toBe("email");
+    });
+
+    it("canSend returns true for email channel with @ recipient", {
+        timeout: 5000,
+    }, () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_1" }),
+        });
+        expect(channel.canSend(makeNotification())).toBe(true);
+    });
+
+    it("canSend returns false for non-email channel", { timeout: 5000 }, () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_1" }),
+        });
+        expect(channel.canSend(makeNotification({ channel: "sms" }))).toBe(
+            false
+        );
+    });
+
+    it("canSend returns false for recipient without @", {
+        timeout: 5000,
+    }, () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_1" }),
+        });
+        expect(
+            channel.canSend(makeNotification({ recipient: "no-at-sign" }))
+        ).toBe(false);
+    });
+
+    it("sends successfully and returns result", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_42" }),
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(true);
+        expect(result.channel).toBe("email");
+        expect(result.messageId).toBe("msg_42");
+        expect(result.timestamp).toBeDefined();
+    });
+
+    it("returns failure when sendFn throws", { timeout: 30000 }, async () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => {
+                throw new Error("SMTP connection failed");
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("SMTP connection failed");
+    });
+
+    it('uses "(No subject)" when subject is missing', {
+        timeout: 30000,
+    }, async () => {
+        let capturedSubject = "";
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async (msg) => {
+                capturedSubject = msg.subject;
+                return { messageId: "msg_1" };
+            },
+        });
+        const n = makeNotification();
+        const { subject: _drop, ...rest } = n;
+        await channel.send(rest as Notification);
+        expect(capturedSubject).toBe("(No subject)");
+    });
+
+    it("passes metadata to sendFn", { timeout: 30000 }, async () => {
+        let capturedMeta: Record<string, unknown> | undefined;
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async (msg) => {
+                capturedMeta = msg.metadata;
+                return { messageId: "msg_1" };
+            },
+        });
+        await channel.send(makeNotification({ metadata: { key: "val" } }));
+        expect(capturedMeta).toEqual({ key: "val" });
+    });
+
+    it("handles non-Error throw in sendFn", { timeout: 30000 }, async () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => {
+                const literal: unknown = "string error";
+                throw literal;
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("string error");
+    });
+
+    it("honours injected clock for timestamp", { timeout: 5000 }, async () => {
+        const channel = new EmailChannel({
+            from: "noreply@example.com",
+            sendFn: async () => ({ messageId: "msg_1" }),
+            clock: () => Date.UTC(2026, 0, 2, 3, 4, 5),
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.timestamp).toBe("2026-01-02T03:04:05.000Z");
+    });
+});

packages/communication/messaging/notification-channel/src/channels/email-channel.ts

@@ -0,0 +1,72 @@
+import type { Clock } from "@suaveplan/types";
+import type { Notification } from "../types/notification.types.js";
+import type { DeliveryChannel, DeliveryResult } from "./delivery-channel.js";
+
+/** Email message passed to the send function. */
+export interface EmailMessage {
+    readonly to: string;
+    readonly subject: string;
+    readonly body: string;
+    readonly metadata?: Record<string, unknown>;
+}
+
+/** Configuration for the email channel. */
+export interface EmailChannelConfig {
+    readonly from: string;
+    readonly sendFn: (message: EmailMessage) => Promise<{ messageId: string }>;
+    /** Optional clock for `timestamp` field (default: `Date.now`). */
+    readonly clock?: Clock;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Delivers notifications via email using a configurable send function.
+ * The `sendFn` is the integration seam — wire a real provider (SES,
+ * SendGrid, Postmark) by implementing the callback signature.
+ */
+export class EmailChannel implements DeliveryChannel {
+    public readonly name = "email";
+    private readonly config: EmailChannelConfig;
+    private readonly clock: Clock;
+
+    public constructor(config: EmailChannelConfig) {
+        this.config = config;
+        this.clock = config.clock ?? defaultClock;
+    }
+
+    public canSend(notification: Notification): boolean {
+        return (
+            notification.channel === "email" &&
+            notification.recipient.includes("@")
+        );
+    }
+
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        const message: EmailMessage = {
+            to: notification.recipient,
+            subject: notification.subject ?? "(No subject)",
+            body: notification.body,
+            ...(notification.metadata !== undefined
+                ? { metadata: notification.metadata }
+                : {}),
+        };
+
+        try {
+            const result = await this.config.sendFn(message);
+            return {
+                success: true,
+                channel: this.name,
+                messageId: result.messageId,
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        } catch (err) {
+            return {
+                success: false,
+                channel: this.name,
+                error: err instanceof Error ? err.message : String(err),
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        }
+    }
+}

packages/communication/messaging/notification-channel/src/channels/in-app-channel.md

@@ -0,0 +1,67 @@
+# `in-app-channel` — In-app notification channel
+
+## Purpose
+
+`in-app-channel.ts` ships the `InAppChannel` implementation that stores notifications for an in-app inbox / unread badge. The default storage is an in-memory `Map<recipientId, InAppNotification[]>`, but the constructor accepts any `InAppStore` implementation so consumers can persist to SurrealDB, Postgres, Redis, or a local IndexedDB browser store. The class is universal — no Node-only or browser-only APIs.
+
+## Features
+
+- Default in-memory store — useful for tests and prototypes.
+- Pluggable `InAppStore` adapter for persistence.
+- `getByRecipient(recipientId)` and `markRead(id)` convenience methods.
+- Records unread by default — flips to read via `markRead`.
+- Returns `DeliveryResult { success: false }` when the store throws, never propagates.
+- Injectable `Clock` for deterministic `createdAt` and `timestamp` fields.
+
+## Usage: Basic
+
+```ts
+import { InAppChannel } from "@suaveplan/notification-channel";
+
+const channel = new InAppChannel();
+await channel.send(notification);
+const unread = (await channel.getByRecipient(notification.recipient)).filter(
+    (n) => !n.read
+);
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    InAppChannel,
+    type InAppNotification,
+    type InAppStore,
+} from "@suaveplan/notification-channel";
+
+const dbStore: InAppStore = {
+    async save(n) {
+        await db.execute("INSERT INTO notifications ...", [n]);
+    },
+    async getByRecipient(recipientId) {
+        return db.query<InAppNotification>(
+            "SELECT * FROM notifications WHERE recipientId = ?",
+            [recipientId]
+        );
+    },
+    async markRead(id) {
+        await db.execute(
+            "UPDATE notifications SET read = true WHERE id = ?",
+            [id]
+        );
+    },
+};
+
+const channel = new InAppChannel(dbStore);
+```
+
+## API Reference
+
+- `InAppChannel(store?: InAppStore, clock?: Clock)` — constructor.
+- `InAppNotification` — `{ id, recipientId, subject?, body, read, createdAt, metadata? }`.
+- `InAppStore` — `save`, `getByRecipient`, `markRead`.
+- `channel.canSend(n)`, `channel.send(n)`, `channel.getByRecipient(id)`, `channel.markRead(id)`.
+
+## Implementation Notes
+
+The default in-memory store backs onto a private `Map` so multiple `InAppChannel` instances do not share state. The store factory closes over the per-instance map to avoid leaking persistence between independent channel objects (useful in tests that construct multiple channels). `markRead` is implemented by scanning every recipient's list — for production-scale deployments the consumer must inject a real store with an indexed lookup; the in-memory variant is a development convenience, not a recommended persistence layer.

packages/communication/messaging/notification-channel/src/channels/in-app-channel.test.ts

@@ -0,0 +1,173 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { Notification } from "../types/notification.types.js";
+import type { InAppNotification, InAppStore } from "./in-app-channel.js";
+import { InAppChannel } from "./in-app-channel.js";
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif_1",
+        channel: "in_app",
+        recipient: "user123",
+        subject: "Test",
+        body: "In-app message",
+        priority: "normal",
+        status: "sending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+describe("InAppChannel", () => {
+    it('has name "in_app"', { timeout: 5000 }, () => {
+        const channel = new InAppChannel();
+        expect(channel.name).toBe("in_app");
+    });
+
+    it("canSend returns true for in_app channel", { timeout: 5000 }, () => {
+        const channel = new InAppChannel();
+        expect(channel.canSend(makeNotification())).toBe(true);
+    });
+
+    it("canSend returns false for non in_app channel", {
+        timeout: 5000,
+    }, () => {
+        const channel = new InAppChannel();
+        expect(channel.canSend(makeNotification({ channel: "email" }))).toBe(
+            false
+        );
+    });
+
+    it("sends and stores notification in memory", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new InAppChannel();
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(true);
+        expect(result.messageId).toBe("notif_1");
+        const stored = await channel.getByRecipient("user123");
+        expect(stored).toHaveLength(1);
+        const first = stored[0];
+        expect(first?.body).toBe("In-app message");
+    });
+
+    it("stores multiple notifications per recipient", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new InAppChannel();
+        await channel.send(makeNotification({ id: "n1" }));
+        await channel.send(makeNotification({ id: "n2", body: "Second" }));
+        const stored = await channel.getByRecipient("user123");
+        expect(stored).toHaveLength(2);
+    });
+
+    it("returns empty array for unknown recipient", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new InAppChannel();
+        const stored = await channel.getByRecipient("unknown");
+        expect(stored).toHaveLength(0);
+    });
+
+    it("marks notification as read", { timeout: 30000 }, async () => {
+        const channel = new InAppChannel();
+        await channel.send(makeNotification());
+        await channel.markRead("notif_1");
+        const stored = await channel.getByRecipient("user123");
+        expect(stored[0]?.read).toBe(true);
+    });
+
+    it("markRead on unknown id is a no-op", { timeout: 5000 }, async () => {
+        const channel = new InAppChannel();
+        await channel.send(makeNotification());
+        await channel.markRead("does-not-exist");
+        const stored = await channel.getByRecipient("user123");
+        expect(stored[0]?.read).toBe(false);
+    });
+
+    it("uses custom store when provided", { timeout: 30000 }, async () => {
+        const records: InAppNotification[] = [];
+        const customStore: InAppStore = {
+            async save(n) {
+                records.push(n);
+            },
+            async getByRecipient() {
+                return records;
+            },
+            async markRead() {
+                /* noop */
+            },
+        };
+        const channel = new InAppChannel(customStore);
+        await channel.send(makeNotification());
+        expect(records).toHaveLength(1);
+    });
+
+    it("handles store save failure gracefully", {
+        timeout: 30000,
+    }, async () => {
+        const failingStore: InAppStore = {
+            async save() {
+                throw new Error("DB write failed");
+            },
+            async getByRecipient() {
+                return [];
+            },
+            async markRead() {
+                /* noop */
+            },
+        };
+        const channel = new InAppChannel(failingStore);
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("DB write failed");
+    });
+
+    it("returns string body when store throws non-Error", {
+        timeout: 5000,
+    }, async () => {
+        const failingStore: InAppStore = {
+            async save() {
+                const literal: unknown = "boom";
+                throw literal;
+            },
+            async getByRecipient() {
+                return [];
+            },
+            async markRead() {
+                /* noop */
+            },
+        };
+        const channel = new InAppChannel(failingStore);
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("boom");
+    });
+
+    it("notification stored as unread by default", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new InAppChannel();
+        await channel.send(makeNotification());
+        const stored = await channel.getByRecipient("user123");
+        expect(stored[0]?.read).toBe(false);
+    });
+
+    it("preserves metadata when notification carries it", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new InAppChannel();
+        await channel.send(makeNotification({ metadata: { trace: "x-1" } }));
+        const stored = await channel.getByRecipient("user123");
+        expect(stored[0]?.metadata).toEqual({ trace: "x-1" });
+    });
+
+    it("supports notifications without metadata and without subject", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new InAppChannel();
+        const { subject: _drop, ...rest } = makeNotification();
+        await channel.send(rest as Notification);
+        const stored = await channel.getByRecipient("user123");
+        expect(stored[0]?.subject).toBeUndefined();
+    });
+});

packages/communication/messaging/notification-channel/src/channels/in-app-channel.ts

@@ -0,0 +1,115 @@
+import type { Clock } from "@suaveplan/types";
+import type { Notification } from "../types/notification.types.js";
+import type { DeliveryChannel, DeliveryResult } from "./delivery-channel.js";
+
+/** Stored in-app notification record. */
+export interface InAppNotification {
+    readonly id: string;
+    readonly recipientId: string;
+    readonly subject?: string;
+    readonly body: string;
+    readonly read: boolean;
+    readonly createdAt: string;
+    readonly metadata?: Record<string, unknown>;
+}
+
+/** Optional store interface for persistence. */
+export interface InAppStore {
+    save(notification: InAppNotification): Promise<void>;
+    getByRecipient(recipientId: string): Promise<InAppNotification[]>;
+    markRead(id: string): Promise<void>;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Delivers notifications in-app by storing them in memory (default) or
+ * a caller-provided `InAppStore` implementation. Suitable for unread
+ * badges, in-app inboxes, and per-user notification feeds.
+ */
+export class InAppChannel implements DeliveryChannel {
+    public readonly name = "in_app";
+    private readonly store: InAppStore;
+    private readonly clock: Clock;
+    private readonly memoryStore = new Map<string, InAppNotification[]>();
+
+    public constructor(store?: InAppStore, clock: Clock = defaultClock) {
+        this.clock = clock;
+        this.store = store ?? this.createMemoryStore();
+    }
+
+    public canSend(notification: Notification): boolean {
+        return notification.channel === "in_app";
+    }
+
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        const record: InAppNotification = {
+            id: notification.id,
+            recipientId: notification.recipient,
+            ...(notification.subject !== undefined
+                ? { subject: notification.subject }
+                : {}),
+            body: notification.body,
+            read: false,
+            createdAt: new Date(this.clock()).toISOString(),
+            ...(notification.metadata !== undefined
+                ? { metadata: notification.metadata }
+                : {}),
+        };
+
+        try {
+            await this.store.save(record);
+            return {
+                success: true,
+                channel: this.name,
+                messageId: notification.id,
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        } catch (err) {
+            return {
+                success: false,
+                channel: this.name,
+                error: err instanceof Error ? err.message : String(err),
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        }
+    }
+
+    /** Get notifications for a recipient (convenience). */
+    public async getByRecipient(
+        recipientId: string
+    ): Promise<InAppNotification[]> {
+        return this.store.getByRecipient(recipientId);
+    }
+
+    /** Mark a notification as read (convenience). */
+    public async markRead(id: string): Promise<void> {
+        return this.store.markRead(id);
+    }
+
+    private createMemoryStore(): InAppStore {
+        const store = this.memoryStore;
+        return {
+            async save(notification: InAppNotification): Promise<void> {
+                const list = store.get(notification.recipientId) ?? [];
+                list.push(notification);
+                store.set(notification.recipientId, list);
+            },
+            async getByRecipient(
+                recipientId: string
+            ): Promise<InAppNotification[]> {
+                return store.get(recipientId) ?? [];
+            },
+            async markRead(id: string): Promise<void> {
+                for (const list of store.values()) {
+                    const existing = list.find((n) => n.id === id);
+                    if (existing !== undefined) {
+                        const idx = list.indexOf(existing);
+                        list.splice(idx, 1, { ...existing, read: true });
+                        return;
+                    }
+                }
+            },
+        };
+    }
+}

packages/communication/messaging/notification-channel/src/channels/push-channel.md

@@ -0,0 +1,65 @@
+# `push-channel` — Web Push notification channel
+
+## Purpose
+
+`push-channel.ts` ships the `PushChannel` implementation that delivers notifications via the Web Push Protocol (RFC 8030) over VAPID-authenticated POSTs. The channel resolves per-user subscriptions through an injected `getSubscriptions(recipient)` callback, then dispatches the encrypted payload to every endpoint either through an explicit `sendFn` (recommended when you already use `web-push` or a vendor SDK) OR a `FetchLike` injectable for the default direct-POST path. Partial success is treated as overall success; only when EVERY subscription fails does the channel report failure.
+
+## Features
+
+- VAPID `{ publicKey, privateKey, subject }` authentication.
+- Multi-subscription fan-out per recipient with partial-success semantics.
+- Pluggable `sendFn` for vendor SDKs; or pluggable `FetchLike` for direct POSTs.
+- Per-channel `ttl` (default 86400 s).
+- Reports `1of3` / `2of2` cardinality in `messageId` for observability.
+- Returns `DeliveryResult { success: false }` when `getSubscriptions` throws OR every subscription fails.
+- Injectable `Clock` for deterministic `timestamp`.
+
+## Usage: Basic
+
+```ts
+import { PushChannel } from "@suaveplan/notification-channel";
+
+const channel = new PushChannel({
+    vapid: { publicKey: "...", privateKey: "...", subject: "mailto:admin@x" },
+    getSubscriptions: (recipient) => db.getPushSubscriptions(recipient),
+});
+const r = await channel.send(notification);
+```
+
+## Usage: Advanced
+
+```ts
+import webPush from "web-push";
+import { PushChannel } from "@suaveplan/notification-channel";
+
+const channel = new PushChannel({
+    vapid,
+    getSubscriptions: (r) => db.getPushSubscriptions(r),
+    sendFn: async (sub, payload, v) => {
+        try {
+            await webPush.sendNotification(sub, payload, {
+                vapidDetails: {
+                    subject: v.subject,
+                    publicKey: v.publicKey,
+                    privateKey: v.privateKey,
+                },
+            });
+            return { success: true, statusCode: 201 };
+        } catch (err) {
+            return { success: false, statusCode: (err as { statusCode?: number }).statusCode ?? 500 };
+        }
+    },
+    ttl: 3600,
+});
+```
+
+## API Reference
+
+- `PushChannel(config: PushChannelConfig)` — constructor.
+- `PushChannelConfig` — `{ vapid, getSubscriptions, sendFn?, fetchFn?, ttl?, clock? }`.
+- `VapidKeys`, `PushSubscription`, `PushPayload`, `PushAction`, `PushSendOutcome` — re-exported types.
+- `canSend(n)`, `send(n)` — `DeliveryChannel` impl.
+
+## Implementation Notes
+
+`Promise.allSettled` is used to fan out so a single bad subscription does not derail the rest. Errors collected from rejected promises are concatenated into the failure message when ALL subscriptions fail. The default fetch path injects `Content-Type`, `Content-Encoding: aes128gcm`, `TTL`, and `Urgency: normal` headers, plus a `vapid t=<pub>, k=<priv>` Authorization header when `vapid.subject` is non-empty. The default path is the simplest correct shape, but production callers SHOULD inject `sendFn` to get proper payload encryption — direct POST without payload encryption is only useful for plain-text push or tests.

packages/communication/messaging/notification-channel/src/channels/push-channel.test.ts

@@ -0,0 +1,366 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { FakeFetch } from "../fakes/fake-fetch.js";
+import type { Notification } from "../types/notification.types.js";
+import { PushChannel } from "./push-channel.js";
+import type { PushSubscription, VapidKeys } from "./push-channel.types.js";
+
+const vapid: VapidKeys = {
+    publicKey: "BPubKey123",
+    privateKey: "PrivKey456",
+    subject: "mailto:admin@example.com",
+};
+
+function makeSub(endpoint = "https://push.example.com/sub1"): PushSubscription {
+    return {
+        endpoint,
+        keys: { p256dh: "p256dh-key", auth: "auth-key" },
+    };
+}
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif-1",
+        channel: "push",
+        recipient: "user-1",
+        subject: "Test Push",
+        body: "Hello push",
+        priority: "normal",
+        status: "pending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+describe("PushChannel", () => {
+    it("canSend returns true for push channel notifications", {
+        timeout: 5000,
+    }, () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+        });
+        expect(channel.canSend(makeNotification())).toBe(true);
+    });
+
+    it("canSend returns false for non-push channel notifications", {
+        timeout: 5000,
+    }, () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+        });
+        expect(channel.canSend(makeNotification({ channel: "email" }))).toBe(
+            false
+        );
+    });
+
+    it("canSend returns false when recipient is empty", {
+        timeout: 5000,
+    }, () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+        });
+        expect(channel.canSend(makeNotification({ recipient: "" }))).toBe(
+            false
+        );
+    });
+
+    it("delivers to a single subscription successfully", {
+        timeout: 5000,
+    }, async () => {
+        const sent: { sub: PushSubscription; payload: string }[] = [];
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            sendFn: async (sub, payload) => {
+                sent.push({ sub, payload });
+                return { success: true, statusCode: 201 };
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(true);
+        expect(result.channel).toBe("push");
+        expect(result.messageId).toContain("push-notif-1");
+        expect(sent).toHaveLength(1);
+
+        const parsed = JSON.parse(sent[0]?.payload ?? "{}");
+        expect(parsed.title).toBe("Test Push");
+        expect(parsed.body).toBe("Hello push");
+        expect(parsed.tag).toBe("notif-1");
+    });
+
+    it("delivers to multiple subscriptions", { timeout: 5000 }, async () => {
+        let sendCount = 0;
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [
+                makeSub("https://push.example.com/sub1"),
+                makeSub("https://push.example.com/sub2"),
+                makeSub("https://push.example.com/sub3"),
+            ],
+            sendFn: async () => {
+                sendCount++;
+                return { success: true, statusCode: 201 };
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(true);
+        expect(result.messageId).toContain("3of3");
+        expect(sendCount).toBe(3);
+    });
+
+    it("reports partial success correctly", { timeout: 5000 }, async () => {
+        let callIndex = 0;
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [
+                makeSub("https://push.example.com/sub1"),
+                makeSub("https://push.example.com/sub2"),
+            ],
+            sendFn: async () => {
+                callIndex++;
+                if (callIndex === 1) return { success: true, statusCode: 201 };
+                return { success: false, statusCode: 410 };
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(true);
+        expect(result.messageId).toContain("1of2");
+    });
+
+    it("returns failure when all subscriptions fail with HTTP errors", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [
+                makeSub(),
+                makeSub("https://push.example.com/sub2"),
+            ],
+            sendFn: async () => ({ success: false, statusCode: 500 }),
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("All 2 subscriptions failed");
+        expect(result.error).toContain("HTTP 500");
+    });
+
+    it("returns failure when no subscriptions found", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [],
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("No push subscriptions");
+    });
+
+    it("handles rejected promises in subscriptions", {
+        timeout: 5000,
+    }, async () => {
+        let callIndex = 0;
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [
+                makeSub(),
+                makeSub("https://push.example.com/sub2"),
+            ],
+            sendFn: async () => {
+                callIndex++;
+                if (callIndex === 1) throw new Error("Network timeout");
+                return { success: true, statusCode: 201 };
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(true);
+        expect(result.messageId).toContain("1of2");
+    });
+
+    it("handles all subscriptions throwing errors", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            sendFn: async () => {
+                throw new Error("Connection refused");
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("Connection refused");
+    });
+
+    it("handles non-Error rejection with default message", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            sendFn: async () => {
+                const literal: unknown = { foo: "bar" };
+                throw literal;
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("Unknown error");
+    });
+
+    it("handles getSubscriptions throwing", { timeout: 5000 }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => {
+                throw new Error("DB unavailable");
+            },
+        });
+
+        const result = await channel.send(makeNotification());
+
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("DB unavailable");
+    });
+
+    it("handles getSubscriptions throwing non-Error", {
+        timeout: 5000,
+    }, async () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => {
+                const literal: unknown = 7;
+                throw literal;
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("7");
+    });
+
+    it("uses default subject when none provided", {
+        timeout: 5000,
+    }, async () => {
+        let capturedPayload = "";
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            sendFn: async (_sub, payload) => {
+                capturedPayload = payload;
+                return { success: true, statusCode: 201 };
+            },
+        });
+
+        const { subject: _drop, ...rest } = makeNotification();
+        await channel.send(rest as Notification);
+
+        const parsed = JSON.parse(capturedPayload);
+        expect(parsed.title).toBe("Notification");
+    });
+
+    it("includes metadata in payload data field", {
+        timeout: 5000,
+    }, async () => {
+        let capturedPayload = "";
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            sendFn: async (_sub, payload) => {
+                capturedPayload = payload;
+                return { success: true, statusCode: 201 };
+            },
+        });
+
+        await channel.send(
+            makeNotification({
+                metadata: { action: "open", url: "/dashboard" },
+            })
+        );
+
+        const parsed = JSON.parse(capturedPayload);
+        expect(parsed.data).toEqual({ action: "open", url: "/dashboard" });
+    });
+
+    it("respects custom TTL config", { timeout: 5000 }, () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [],
+            ttl: 3600,
+        });
+        expect(channel.name).toBe("push");
+    });
+
+    it("uses default fetchFn against VAPID endpoint when sendFn omitted", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 201 });
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            fetchFn: fake.fetch,
+        });
+        const r = await channel.send(makeNotification());
+        expect(r.success).toBe(true);
+        const first = fake.calls[0];
+        expect(first?.url).toBe("https://push.example.com/sub1");
+        const headers = (first?.init?.headers ?? {}) as Record<string, string>;
+        expect(headers["Authorization"]).toContain("vapid");
+    });
+
+    it("omits Authorization header when vapid.subject is empty", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 201 });
+        const channel = new PushChannel({
+            vapid: { publicKey: "p", privateKey: "k", subject: "" },
+            getSubscriptions: async () => [makeSub()],
+            fetchFn: fake.fetch,
+        });
+        await channel.send(makeNotification());
+        const headers = (fake.calls[0]?.init?.headers ?? {}) as Record<
+            string,
+            string
+        >;
+        expect(headers["Authorization"]).toBeUndefined();
+    });
+
+    it("default fetchFn reports HTTP non-2xx as failure", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 410 });
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [makeSub()],
+            fetchFn: fake.fetch,
+        });
+        const r = await channel.send(makeNotification());
+        expect(r.success).toBe(false);
+        expect(r.error).toContain("HTTP 410");
+    });
+
+    it('has name "push"', { timeout: 5000 }, () => {
+        const channel = new PushChannel({
+            vapid,
+            getSubscriptions: async () => [],
+        });
+        expect(channel.name).toBe("push");
+    });
+});

packages/communication/messaging/notification-channel/src/channels/push-channel.ts

@@ -0,0 +1,163 @@
+import type { Clock, FetchLike } from "@suaveplan/types";
+import type { Notification } from "../types/notification.types.js";
+import type { DeliveryChannel, DeliveryResult } from "./delivery-channel.js";
+import type {
+    PushChannelConfig,
+    PushPayload,
+    PushSendOutcome,
+    PushSubscription,
+    VapidKeys,
+} from "./push-channel.types.js";
+
+const defaultClock: Clock = () => Date.now();
+
+async function defaultSendPush(
+    subscription: PushSubscription,
+    payload: string,
+    vapid: VapidKeys,
+    ttl: number,
+    fetchFn: FetchLike
+): Promise<PushSendOutcome> {
+    const headers: Record<string, string> = {
+        "Content-Type": "application/json",
+        "Content-Encoding": "aes128gcm",
+        TTL: String(ttl),
+        Urgency: "normal",
+    };
+
+    if (vapid.subject) {
+        headers["Authorization"] =
+            `vapid t=${vapid.publicKey}, k=${vapid.privateKey}`;
+    }
+
+    const response = await fetchFn(subscription.endpoint, {
+        method: "POST",
+        headers,
+        body: payload,
+    });
+
+    return {
+        success: response.status >= 200 && response.status < 300,
+        statusCode: response.status,
+    };
+}
+
+/**
+ * Delivers notifications via the Web Push Protocol (RFC 8030). The
+ * channel is intentionally provider-neutral: the `sendFn` callback OR
+ * the injected `fetchFn` performs the VAPID-authenticated POST against
+ * each subscription's endpoint, and the channel aggregates partial
+ * success/failure into a single `DeliveryResult`.
+ */
+export class PushChannel implements DeliveryChannel {
+    public readonly name = "push";
+    private readonly config: PushChannelConfig;
+    private readonly ttl: number;
+    private readonly clock: Clock;
+    private readonly fetchFn: FetchLike;
+
+    public constructor(config: PushChannelConfig) {
+        this.config = config;
+        this.ttl = config.ttl ?? 86_400;
+        this.clock = config.clock ?? defaultClock;
+        this.fetchFn = config.fetchFn ?? globalThis.fetch.bind(globalThis);
+    }
+
+    public canSend(notification: Notification): boolean {
+        return notification.channel === "push" && notification.recipient !== "";
+    }
+
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        try {
+            const subscriptions = await this.config.getSubscriptions(
+                notification.recipient
+            );
+
+            if (subscriptions.length === 0) {
+                return this.fail(
+                    "No push subscriptions found for recipient",
+                    notification
+                );
+            }
+
+            const payload = this.buildPayload(notification);
+            const payloadStr = JSON.stringify(payload);
+            const results = await Promise.allSettled(
+                subscriptions.map((sub) =>
+                    this.sendToSubscription(sub, payloadStr)
+                )
+            );
+
+            const successes = results.filter(
+                (r) => r.status === "fulfilled" && r.value.success
+            );
+
+            if (successes.length === 0) {
+                const errors = results
+                    .map((r) => {
+                        if (r.status === "rejected") {
+                            const cause = r.reason as { message?: string };
+                            return cause.message ?? "Unknown error";
+                        }
+                        return `HTTP ${r.value.statusCode}`;
+                    })
+                    .filter(Boolean);
+                return this.fail(
+                    `All ${subscriptions.length} subscriptions failed: ${errors.join(", ")}`,
+                    notification
+                );
+            }
+
+            return {
+                success: true,
+                channel: this.name,
+                messageId: `push-${notification.id}-${successes.length}of${subscriptions.length}`,
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        } catch (err) {
+            return this.fail(
+                err instanceof Error ? err.message : String(err),
+                notification
+            );
+        }
+    }
+
+    private fail(error: string, _notification: Notification): DeliveryResult {
+        return {
+            success: false,
+            channel: this.name,
+            error,
+            timestamp: new Date(this.clock()).toISOString(),
+        };
+    }
+
+    private buildPayload(notification: Notification): PushPayload {
+        const payload: {
+            -readonly [K in keyof PushPayload]: PushPayload[K];
+        } = {
+            title: notification.subject ?? "Notification",
+            body: notification.body,
+            tag: notification.id,
+        };
+        if (notification.metadata !== undefined) {
+            payload.data = notification.metadata;
+        }
+        return payload;
+    }
+
+    private async sendToSubscription(
+        subscription: PushSubscription,
+        payload: string
+    ): Promise<PushSendOutcome> {
+        if (this.config.sendFn !== undefined) {
+            return this.config.sendFn(subscription, payload, this.config.vapid);
+        }
+        return defaultSendPush(
+            subscription,
+            payload,
+            this.config.vapid,
+            this.ttl,
+            this.fetchFn
+        );
+    }
+}

packages/communication/messaging/notification-channel/src/channels/push-channel.types.ts

@@ -0,0 +1,67 @@
+import type { Clock, FetchLike } from "@suaveplan/types";
+
+/** VAPID key pair for Web Push authentication. */
+export interface VapidKeys {
+    readonly publicKey: string;
+    readonly privateKey: string;
+    readonly subject: string;
+}
+
+/** A web push subscription (from the browser's PushManager). */
+export interface PushSubscription {
+    readonly endpoint: string;
+    readonly keys: {
+        readonly p256dh: string;
+        readonly auth: string;
+    };
+    readonly expirationTime?: number | null;
+}
+
+/** Action button for push notifications. */
+export interface PushAction {
+    readonly action: string;
+    readonly title: string;
+    readonly icon?: string;
+}
+
+/** Push notification payload. */
+export interface PushPayload {
+    readonly title: string;
+    readonly body: string;
+    readonly icon?: string;
+    readonly badge?: string;
+    readonly image?: string;
+    readonly tag?: string;
+    readonly data?: Record<string, unknown>;
+    readonly actions?: readonly PushAction[];
+    readonly requireInteraction?: boolean;
+    readonly silent?: boolean;
+}
+
+/** Outcome returned by the optional injected `sendFn`. */
+export interface PushSendOutcome {
+    readonly success: boolean;
+    readonly statusCode: number;
+}
+
+/** Configuration for the push channel. */
+export interface PushChannelConfig {
+    /** VAPID keys for authentication. */
+    readonly vapid: VapidKeys;
+    /** Function to look up push subscriptions for a recipient. */
+    readonly getSubscriptions: (
+        recipient: string
+    ) => Promise<readonly PushSubscription[]>;
+    /** Optional function to send the actual push message. */
+    readonly sendFn?: (
+        subscription: PushSubscription,
+        payload: string,
+        vapid: VapidKeys
+    ) => Promise<PushSendOutcome>;
+    /** Optional fetch implementation used when `sendFn` is omitted. */
+    readonly fetchFn?: FetchLike;
+    /** TTL in seconds for push messages (default: 86400). */
+    readonly ttl?: number;
+    /** Optional clock for the `timestamp` field. */
+    readonly clock?: Clock;
+}

packages/communication/messaging/notification-channel/src/channels/sms-channel.md

@@ -0,0 +1,63 @@
+# `sms-channel` — SMS delivery channel
+
+## Purpose
+
+`sms-channel.ts` ships the `SmsChannel` `DeliveryChannel` implementation. Like the email channel, it is provider-neutral: a caller-supplied `sendFn(message)` performs the actual API call into Twilio, MessageBird, Vonage, Sinch, or any in-house SMSC. The channel keeps the responsibility surface tiny — recipient validation (E.164 `+` prefix), payload shaping, and error swallowing — so the router can stay decoupled from any specific carrier.
+
+## Features
+
+- Provider-neutral via injectable `sendFn`.
+- `canSend` rejects recipients that do not start with `+` (E.164 prefix); avoids hitting upstream providers with formats they will reject.
+- Propagates `metadata` to the provider message for correlation IDs and segmentation.
+- Injectable `Clock` for deterministic `timestamp` fields in tests.
+- Returns `DeliveryResult` even on provider failure — never throws to the router.
+
+## Usage: Basic
+
+```ts
+import { SmsChannel } from "@suaveplan/notification-channel";
+
+const channel = new SmsChannel({
+    from: "+15559999999",
+    sendFn: async (msg) => ({
+        messageId: await twilio.messages.create({
+            from: "+15559999999",
+            to: msg.to,
+            body: msg.body,
+        }).sid,
+    }),
+});
+```
+
+## Usage: Advanced
+
+```ts
+import { SmsChannel } from "@suaveplan/notification-channel";
+
+const channel = new SmsChannel({
+    from: "+15559999999",
+    sendFn: async (msg) => {
+        const { sid } = await provider.send({
+            from: "+15559999999",
+            to: msg.to,
+            body: msg.body,
+            ...(msg.metadata?.["statusCallback"] !== undefined
+                ? { statusCallback: msg.metadata["statusCallback"] }
+                : {}),
+        });
+        return { messageId: sid };
+    },
+    clock: () => testNow,
+});
+```
+
+## API Reference
+
+- `SmsChannel(config: SmsChannelConfig)` — constructor.
+- `SmsChannelConfig` — `{ from, sendFn, clock? }`.
+- `SmsMessage` — `{ to, body, metadata? }` passed to `sendFn`.
+- `canSend(n): boolean`, `send(n): Promise<DeliveryResult>` — `DeliveryChannel` impl.
+
+## Implementation Notes
+
+The `+` prefix check is intentionally conservative — it does not validate the full E.164 country/area format because providers do that anyway and over-validating client-side breaks edge cases like short-code dispatch. Tests cover both `Error` and non-`Error` throws inside `sendFn` to lock in the `String(err)` coercion. The injected `clock` only affects the `DeliveryResult.timestamp` field; provider-recorded send time remains authoritative.

packages/communication/messaging/notification-channel/src/channels/sms-channel.test.ts

@@ -0,0 +1,125 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { Notification } from "../types/notification.types.js";
+import { SmsChannel } from "./sms-channel.js";
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif_1",
+        channel: "sms",
+        recipient: "+15551234567",
+        body: "Test SMS body",
+        priority: "normal",
+        status: "sending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+describe("SmsChannel", () => {
+    it('has name "sms"', { timeout: 5000 }, () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_1" }),
+        });
+        expect(channel.name).toBe("sms");
+    });
+
+    it("canSend returns true for sms channel with + recipient", {
+        timeout: 5000,
+    }, () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_1" }),
+        });
+        expect(channel.canSend(makeNotification())).toBe(true);
+    });
+
+    it("canSend returns false for non-sms channel", { timeout: 5000 }, () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_1" }),
+        });
+        expect(channel.canSend(makeNotification({ channel: "email" }))).toBe(
+            false
+        );
+    });
+
+    it("canSend returns false for recipient without +", {
+        timeout: 5000,
+    }, () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_1" }),
+        });
+        expect(
+            channel.canSend(makeNotification({ recipient: "5551234567" }))
+        ).toBe(false);
+    });
+
+    it("sends successfully and returns result", {
+        timeout: 30000,
+    }, async () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_42" }),
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(true);
+        expect(result.channel).toBe("sms");
+        expect(result.messageId).toBe("sms_42");
+        expect(result.timestamp).toBeDefined();
+    });
+
+    it("returns failure when sendFn throws", { timeout: 30000 }, async () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => {
+                throw new Error("SMS provider down");
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("SMS provider down");
+    });
+
+    it("passes body and metadata to sendFn", { timeout: 30000 }, async () => {
+        let capturedBody = "";
+        let capturedMeta: Record<string, unknown> | undefined;
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async (msg) => {
+                capturedBody = msg.body;
+                capturedMeta = msg.metadata;
+                return { messageId: "sms_1" };
+            },
+        });
+        await channel.send(
+            makeNotification({ body: "Hello SMS", metadata: { tag: "urgent" } })
+        );
+        expect(capturedBody).toBe("Hello SMS");
+        expect(capturedMeta).toEqual({ tag: "urgent" });
+    });
+
+    it("handles non-Error throw in sendFn", { timeout: 30000 }, async () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => {
+                const literal: unknown = 42;
+                throw literal;
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("42");
+    });
+
+    it("honours injected clock", { timeout: 5000 }, async () => {
+        const channel = new SmsChannel({
+            from: "+15559999999",
+            sendFn: async () => ({ messageId: "sms_1" }),
+            clock: () => Date.UTC(2026, 0, 1),
+        });
+        const r = await channel.send(makeNotification());
+        expect(r.timestamp).toBe("2026-01-01T00:00:00.000Z");
+    });
+});

packages/communication/messaging/notification-channel/src/channels/sms-channel.ts

@@ -0,0 +1,70 @@
+import type { Clock } from "@suaveplan/types";
+import type { Notification } from "../types/notification.types.js";
+import type { DeliveryChannel, DeliveryResult } from "./delivery-channel.js";
+
+/** SMS message passed to the send function. */
+export interface SmsMessage {
+    readonly to: string;
+    readonly body: string;
+    readonly metadata?: Record<string, unknown>;
+}
+
+/** Configuration for the SMS channel. */
+export interface SmsChannelConfig {
+    readonly from: string;
+    readonly sendFn: (message: SmsMessage) => Promise<{ messageId: string }>;
+    /** Optional clock for `timestamp` field (default: `Date.now`). */
+    readonly clock?: Clock;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Delivers notifications via SMS using a configurable send function.
+ * The `sendFn` is the integration seam — wire Twilio / MessageBird /
+ * Vonage by implementing the callback signature.
+ */
+export class SmsChannel implements DeliveryChannel {
+    public readonly name = "sms";
+    private readonly config: SmsChannelConfig;
+    private readonly clock: Clock;
+
+    public constructor(config: SmsChannelConfig) {
+        this.config = config;
+        this.clock = config.clock ?? defaultClock;
+    }
+
+    public canSend(notification: Notification): boolean {
+        return (
+            notification.channel === "sms" &&
+            notification.recipient.startsWith("+")
+        );
+    }
+
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        const message: SmsMessage = {
+            to: notification.recipient,
+            body: notification.body,
+            ...(notification.metadata !== undefined
+                ? { metadata: notification.metadata }
+                : {}),
+        };
+
+        try {
+            const result = await this.config.sendFn(message);
+            return {
+                success: true,
+                channel: this.name,
+                messageId: result.messageId,
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        } catch (err) {
+            return {
+                success: false,
+                channel: this.name,
+                error: err instanceof Error ? err.message : String(err),
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        }
+    }
+}

packages/communication/messaging/notification-channel/src/channels/webhook-channel.md

@@ -0,0 +1,56 @@
+# `webhook-channel` — HTTP webhook delivery channel
+
+## Purpose
+
+`webhook-channel.ts` ships the `WebhookChannel` implementation that POSTs notifications to an arbitrary HTTPS endpoint. The notification's `recipient` field IS the destination URL, the body carries the serialised notification payload, and the channel respects a per-request timeout via `AbortController`. The fetch surface is injectable via `FetchLike` from `@suaveplan/types`, so tests run deterministically against `FakeFetch` and downstream consumers can plug their own observability-instrumented fetch.
+
+## Features
+
+- Injectable `FetchLike` — no `globalThis.fetch` patching.
+- Configurable timeout (default 10_000 ms) using `AbortController`.
+- Custom headers via `WebhookChannelConfig.headers`.
+- `canSend` enforces `http://` or `https://` recipient prefix.
+- Returns `DeliveryResult { success: false }` on non-2xx, network error, abort, or unexpected throw.
+- Injectable `Clock` for deterministic `timestamp` in tests.
+
+## Usage: Basic
+
+```ts
+import { WebhookChannel } from "@suaveplan/notification-channel";
+
+const channel = new WebhookChannel({
+    headers: { Authorization: "Bearer secret" },
+});
+const r = await channel.send(notification);
+```
+
+## Usage: Advanced
+
+```ts
+import { FakeFetch, WebhookChannel } from "@suaveplan/notification-channel";
+
+// In tests:
+const fake = new FakeFetch();
+fake.push({ status: 200 });
+const channel = new WebhookChannel({
+    fetchFn: fake.fetch,
+    timeoutMs: 500,
+    clock: () => testNow,
+});
+
+// In prod, wire a real instrumented fetch:
+const channel2 = new WebhookChannel({
+    fetchFn: (url, init) => instrumented.fetch(url, init),
+    headers: { "X-Signed-By": "suaveplan" },
+});
+```
+
+## API Reference
+
+- `WebhookChannel(config?: WebhookChannelConfig)` — constructor.
+- `WebhookChannelConfig` — `{ headers?, fetchFn?, timeoutMs?, clock? }`.
+- `canSend(n): boolean`, `send(n): Promise<DeliveryResult>`.
+
+## Implementation Notes
+
+The POST body is built from `{ id, subject, body, priority, metadata, createdAt }` — a stable shape so webhook consumers can lock their parsers. `Content-Type: application/json` is always set; consumer headers override the default. Aborted fetches surface `error: "aborted"` (matching the `AbortError.name`-derived message from the polyfill). Non-2xx responses encode the upstream status into `error: "HTTP <status>: <statusText>"`. Both `Error` and non-`Error` throws inside the fetch callback are stringified into `error` so the `DeliveryResult` contract holds.

packages/communication/messaging/notification-channel/src/channels/webhook-channel.test.ts

@@ -0,0 +1,153 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { FakeFetch } from "../fakes/fake-fetch.js";
+import type { Notification } from "../types/notification.types.js";
+import { WebhookChannel } from "./webhook-channel.js";
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif_1",
+        channel: "webhook",
+        recipient: "https://hooks.example.com/callback",
+        subject: "Test Hook",
+        body: "Webhook payload",
+        priority: "normal",
+        status: "sending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+describe("WebhookChannel", () => {
+    it('has name "webhook"', { timeout: 5000 }, () => {
+        const channel = new WebhookChannel();
+        expect(channel.name).toBe("webhook");
+    });
+
+    it("canSend returns true for webhook channel with https URL", {
+        timeout: 5000,
+    }, () => {
+        const channel = new WebhookChannel();
+        expect(channel.canSend(makeNotification())).toBe(true);
+    });
+
+    it("canSend returns true for http URL", { timeout: 5000 }, () => {
+        const channel = new WebhookChannel();
+        expect(
+            channel.canSend(
+                makeNotification({ recipient: "http://hooks.example.com/cb" })
+            )
+        ).toBe(true);
+    });
+
+    it("canSend returns false for non-webhook channel", {
+        timeout: 5000,
+    }, () => {
+        const channel = new WebhookChannel();
+        expect(channel.canSend(makeNotification({ channel: "email" }))).toBe(
+            false
+        );
+    });
+
+    it("canSend returns false for non-URL recipient", { timeout: 5000 }, () => {
+        const channel = new WebhookChannel();
+        expect(
+            channel.canSend(makeNotification({ recipient: "not-a-url" }))
+        ).toBe(false);
+    });
+
+    it("sends successfully with 200 response", { timeout: 30000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        const channel = new WebhookChannel({ fetchFn: fake.fetch });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(true);
+        expect(result.channel).toBe("webhook");
+        expect(result.messageId).toBe("notif_1");
+        const first = fake.calls[0];
+        expect(first?.url).toBe("https://hooks.example.com/callback");
+    });
+
+    it("returns failure for non-ok response", { timeout: 30000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 500 });
+        const channel = new WebhookChannel({ fetchFn: fake.fetch });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("500");
+    });
+
+    it("returns failure when fetch throws", { timeout: 30000 }, async () => {
+        const channel = new WebhookChannel({
+            fetchFn: async () => {
+                throw new Error("Network error");
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("Network error");
+    });
+
+    it("sends correct payload in POST body", { timeout: 30000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        const channel = new WebhookChannel({ fetchFn: fake.fetch });
+        await channel.send(makeNotification());
+        const init = fake.calls[0]?.init;
+        const body = init?.body;
+        expect(typeof body).toBe("string");
+        const parsed = JSON.parse(body as string);
+        expect(parsed.id).toBe("notif_1");
+        expect(parsed.body).toBe("Webhook payload");
+    });
+
+    it("includes custom headers", { timeout: 30000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        const channel = new WebhookChannel({
+            headers: { Authorization: "Bearer token123" },
+            fetchFn: fake.fetch,
+        });
+        await channel.send(makeNotification());
+        const init = fake.calls[0]?.init;
+        const headers = init?.headers as Record<string, string>;
+        expect(headers["Authorization"]).toBe("Bearer token123");
+        expect(headers["Content-Type"]).toBe("application/json");
+    });
+
+    it("handles non-Error throw", { timeout: 30000 }, async () => {
+        const channel = new WebhookChannel({
+            fetchFn: async () => {
+                const literal: unknown = "fetch failed";
+                throw literal;
+            },
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("fetch failed");
+    });
+
+    it("honours injected clock for timestamp", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        const channel = new WebhookChannel({
+            fetchFn: fake.fetch,
+            clock: () => Date.UTC(2026, 0, 1),
+        });
+        const r = await channel.send(makeNotification());
+        expect(r.timestamp).toBe("2026-01-01T00:00:00.000Z");
+    });
+
+    it("respects custom timeout via AbortController", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ pending: true });
+        const channel = new WebhookChannel({
+            fetchFn: fake.fetch,
+            timeoutMs: 5,
+        });
+        const result = await channel.send(makeNotification());
+        expect(result.success).toBe(false);
+        expect(result.error).toBe("aborted");
+    });
+});

packages/communication/messaging/notification-channel/src/channels/webhook-channel.ts

@@ -0,0 +1,96 @@
+import type { Clock, FetchLike } from "@suaveplan/types";
+import type { Notification } from "../types/notification.types.js";
+import type { DeliveryChannel, DeliveryResult } from "./delivery-channel.js";
+
+/** Configuration for the webhook channel. */
+export interface WebhookChannelConfig {
+    /** Default headers added to every request. */
+    readonly headers?: Readonly<Record<string, string>>;
+    /** Optional `FetchLike` implementation (default: `globalThis.fetch`). */
+    readonly fetchFn?: FetchLike;
+    /** Timeout in milliseconds (default: 10_000). */
+    readonly timeoutMs?: number;
+    /** Optional clock for the `timestamp` field (default: `Date.now`). */
+    readonly clock?: Clock;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Delivers notifications via HTTP webhook POST requests. The
+ * notification's `recipient` field is the destination URL; the body
+ * contains the serialised notification payload.
+ */
+export class WebhookChannel implements DeliveryChannel {
+    public readonly name = "webhook";
+    private readonly config: WebhookChannelConfig;
+    private readonly clock: Clock;
+    private readonly fetchFn: FetchLike;
+
+    public constructor(config?: WebhookChannelConfig) {
+        this.config = config ?? {};
+        this.clock = this.config.clock ?? defaultClock;
+        this.fetchFn = this.config.fetchFn ?? globalThis.fetch.bind(globalThis);
+    }
+
+    public canSend(notification: Notification): boolean {
+        return (
+            notification.channel === "webhook" &&
+            (notification.recipient.startsWith("http://") ||
+                notification.recipient.startsWith("https://"))
+        );
+    }
+
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        const timeoutMs = this.config.timeoutMs ?? 10_000;
+
+        const payload = {
+            id: notification.id,
+            subject: notification.subject,
+            body: notification.body,
+            priority: notification.priority,
+            metadata: notification.metadata,
+            createdAt: notification.createdAt,
+        };
+
+        try {
+            const controller = new AbortController();
+            const timer = setTimeout(() => controller.abort(), timeoutMs);
+
+            const response = await this.fetchFn(notification.recipient, {
+                method: "POST",
+                headers: {
+                    "Content-Type": "application/json",
+                    ...this.config.headers,
+                },
+                body: JSON.stringify(payload),
+                signal: controller.signal,
+            });
+
+            clearTimeout(timer);
+
+            if (!response.ok) {
+                return {
+                    success: false,
+                    channel: this.name,
+                    error: `HTTP ${response.status}: ${response.statusText}`,
+                    timestamp: new Date(this.clock()).toISOString(),
+                };
+            }
+
+            return {
+                success: true,
+                channel: this.name,
+                messageId: notification.id,
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        } catch (err) {
+            return {
+                success: false,
+                channel: this.name,
+                error: err instanceof Error ? err.message : String(err),
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        }
+    }
+}

packages/communication/messaging/notification-channel/src/digest/digest-channel.md

@@ -0,0 +1,57 @@
+# `digest-channel` — Digest delivery channel
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`digest-channel.ts` ships the `DigestChannel` implementation that batches notifications into periodic summaries delivered through a delegate `DeliveryChannel`. It is the channel-shape adapter for "weekly summary email" / "hourly Slack roll-up" / "daily push digest" use-cases — it implements `DeliveryChannel` so it slots into the router exactly like a direct channel, and it owns its own per-recipient queue.
+
+## Features
+
+- Wraps any `DeliveryChannel` as `delegate`.
+- Per-recipient FIFO queue with configurable `maxPerDigest` cap.
+- `intervalMs` gates the next flush — `send` opportunistically flushes when the interval has elapsed since the last flush.
+- Customisable `formatDigest(notifications)` formatter.
+- `flush(recipient)`, `flushAll()`, `queueSize`, `pendingRecipients` for ops/cron integrations.
+- Injectable `Clock` so tests advance the interval without sleeping.
+
+## Usage: Basic
+
+```ts
+import { DigestChannel, EmailChannel } from "@suaveplan/notification-channel";
+
+const email = new EmailChannel({ from: "noreply@x", sendFn });
+const digest = new DigestChannel({
+    delegate: email,
+    intervalMs: 3_600_000,
+});
+await digest.send(notification);
+```
+
+## Usage: Advanced
+
+```ts
+const digest = new DigestChannel({
+    delegate: email,
+    intervalMs: 86_400_000,
+    maxPerDigest: 25,
+    formatDigest: (ns) =>
+        ns.map((n, i) => `${i + 1}. [${n.priority}] ${n.subject}: ${n.body}`).join("\n"),
+    clock: () => Date.now(),
+});
+
+// In a cron handler:
+const results = await digest.flushAll();
+```
+
+## API Reference
+
+- `DigestChannel(config: DigestChannelConfig)` — constructor.
+- `DigestChannelConfig` — `{ delegate, intervalMs?, maxPerDigest?, formatDigest?, clock? }`.
+- `enqueue(n)`, `send(n)`, `flush(recipient)`, `flushAll()`, `queueSize(recipient)`, `pendingRecipients()`, `canSend(n)`.
+
+## Implementation Notes
+
+`enqueue` silently drops the overflow when the queue reaches `maxPerDigest`. This is a deliberate denial-of-service shield — a runaway pipeline cannot blow memory by enqueuing forever. The default formatter numbers entries and labels them by subject; consumers wanting Markdown / HTML output supply their own `formatDigest`. `canSend` proxies to the delegate, so the digest channel inherits the delegate's recipient validation — useful when the delegate is an `EmailChannel` that wants `@`-only recipients. `lastFlush` is tracked per-recipient and consulted from `send`/`flushAll`; a recipient flushed seconds ago will not flush again until the interval has elapsed.

packages/communication/messaging/notification-channel/src/digest/digest-channel.test.ts

@@ -0,0 +1,352 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "../channels/delivery-channel.js";
+import type { Notification } from "../types/notification.types.js";
+import { DigestChannel } from "./digest-channel.js";
+
+let counter = 0;
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    counter++;
+    return {
+        id: `notif-${counter}`,
+        channel: "email",
+        recipient: "user@example.com",
+        subject: "Test",
+        body: "Hello",
+        priority: "normal",
+        status: "pending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+function makeMockDelegate(): DeliveryChannel & {
+    sentNotifications: Notification[];
+} {
+    const sentNotifications: Notification[] = [];
+    return {
+        name: "mock-email",
+        sentNotifications,
+        canSend: () => true,
+        send: async (notification: Notification): Promise<DeliveryResult> => {
+            sentNotifications.push(notification);
+            return {
+                success: true,
+                channel: "mock-email",
+                messageId: `msg-${notification.id}`,
+                timestamp: new Date().toISOString(),
+            };
+        },
+    };
+}
+
+describe("DigestChannel", () => {
+    describe("enqueue", () => {
+        it("queues notifications for a recipient", { timeout: 5000 }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+
+            expect(digest.queueSize("alice@test.com")).toBe(2);
+        });
+
+        it("queues notifications for different recipients separately", {
+            timeout: 5000,
+        }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            digest.enqueue(makeNotification({ recipient: "bob@test.com" }));
+
+            expect(digest.queueSize("alice@test.com")).toBe(1);
+            expect(digest.queueSize("bob@test.com")).toBe(1);
+        });
+
+        it("respects maxPerDigest limit", { timeout: 5000 }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate, maxPerDigest: 3 });
+
+            for (let i = 0; i < 10; i++) {
+                digest.enqueue(
+                    makeNotification({ recipient: "alice@test.com" })
+                );
+            }
+
+            expect(digest.queueSize("alice@test.com")).toBe(3);
+        });
+    });
+
+    describe("flush", () => {
+        it("delivers a single digest via delegate", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(
+                makeNotification({ recipient: "alice@test.com", body: "First" })
+            );
+            digest.enqueue(
+                makeNotification({
+                    recipient: "alice@test.com",
+                    body: "Second",
+                })
+            );
+
+            const result = await digest.flush("alice@test.com");
+
+            expect(result.success).toBe(true);
+            expect(delegate.sentNotifications).toHaveLength(1);
+
+            const sent = delegate.sentNotifications[0];
+            expect(sent?.subject).toContain("2 notifications");
+            expect(sent?.body).toContain("First");
+            expect(sent?.body).toContain("Second");
+            expect(sent?.recipient).toBe("alice@test.com");
+        });
+
+        it("clears the queue after flushing", { timeout: 5000 }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            await digest.flush("alice@test.com");
+
+            expect(digest.queueSize("alice@test.com")).toBe(0);
+        });
+
+        it("returns empty result for empty queue", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            const result = await digest.flush("nobody@test.com");
+
+            expect(result.success).toBe(true);
+            expect(result.messageId).toBe("digest-empty");
+            expect(delegate.sentNotifications).toHaveLength(0);
+        });
+
+        it("uses singular form for single notification", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            await digest.flush("alice@test.com");
+
+            const sent = delegate.sentNotifications[0];
+            expect(sent?.subject).toBe("Digest: 1 notification");
+        });
+
+        it("uses custom formatDigest function", { timeout: 5000 }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({
+                delegate,
+                formatDigest: (notifs) =>
+                    notifs.map((n) => `* ${n.body}`).join("\n"),
+            });
+
+            digest.enqueue(
+                makeNotification({ recipient: "alice@test.com", body: "A" })
+            );
+            digest.enqueue(
+                makeNotification({ recipient: "alice@test.com", body: "B" })
+            );
+            await digest.flush("alice@test.com");
+
+            const sent = delegate.sentNotifications[0];
+            expect(sent?.body).toBe("* A\n* B");
+        });
+
+        it("uses default format with numbered list", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(
+                makeNotification({
+                    recipient: "alice@test.com",
+                    subject: "Alert",
+                    body: "msg1",
+                })
+            );
+            digest.enqueue(
+                makeNotification({
+                    recipient: "alice@test.com",
+                    subject: "Alert",
+                    body: "msg2",
+                })
+            );
+            await digest.flush("alice@test.com");
+
+            const sent = delegate.sentNotifications[0];
+            expect(sent?.body).toContain("1. Alert: msg1");
+            expect(sent?.body).toContain("2. Alert: msg2");
+        });
+
+        it("default format uses 'Notification' label when subject missing", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            const { subject: _drop, ...rest } = makeNotification({
+                recipient: "alice@test.com",
+                body: "body-only",
+            });
+            digest.enqueue(rest as Notification);
+            await digest.flush("alice@test.com");
+
+            const sent = delegate.sentNotifications[0];
+            expect(sent?.body).toContain("1. Notification: body-only");
+        });
+    });
+
+    describe("send", () => {
+        it("enqueues and flushes when interval has elapsed", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate, intervalMs: 0 });
+
+            const result = await digest.send(
+                makeNotification({ recipient: "alice@test.com" })
+            );
+
+            expect(result.success).toBe(true);
+            expect(delegate.sentNotifications).toHaveLength(1);
+        });
+
+        it("enqueues without flushing when interval has not passed", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            // Use a clock so we can simulate the interval boundary.
+            let now = 1_000_000;
+            const digest = new DigestChannel({
+                delegate,
+                intervalMs: 3_600_000,
+                clock: () => now,
+            });
+
+            await digest.send(
+                makeNotification({ recipient: "alice@test.com" })
+            );
+            // First send triggers a flush (no previous flush). Advance just
+            // 1 ms; interval has NOT elapsed, second send must remain queued.
+            now += 1;
+            const result = await digest.send(
+                makeNotification({ recipient: "alice@test.com" })
+            );
+
+            expect(result.success).toBe(true);
+            expect(result.messageId).toContain("digest-queued");
+        });
+    });
+
+    describe("flushAll", () => {
+        it("flushes all recipients that are ready", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate, intervalMs: 0 });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            digest.enqueue(makeNotification({ recipient: "bob@test.com" }));
+
+            const results = await digest.flushAll();
+
+            expect(results).toHaveLength(2);
+            expect(results.every((r) => r.success)).toBe(true);
+            expect(delegate.sentNotifications).toHaveLength(2);
+        });
+
+        it("skips recipients not ready for flush", {
+            timeout: 5000,
+        }, async () => {
+            const delegate = makeMockDelegate();
+            let now = 1_000_000;
+            const digest = new DigestChannel({
+                delegate,
+                intervalMs: 3_600_000,
+                clock: () => now,
+            });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            // Force a flush to set lastFlush time
+            await digest.flush("alice@test.com");
+
+            // Enqueue more
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            now += 1; // not yet at interval
+
+            const results = await digest.flushAll();
+            expect(results).toHaveLength(0);
+        });
+    });
+
+    describe("pendingRecipients", () => {
+        it("lists recipients with pending notifications", {
+            timeout: 5000,
+        }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            digest.enqueue(makeNotification({ recipient: "alice@test.com" }));
+            digest.enqueue(makeNotification({ recipient: "bob@test.com" }));
+
+            const pending = digest.pendingRecipients();
+
+            expect(pending).toContain("alice@test.com");
+            expect(pending).toContain("bob@test.com");
+            expect(pending).toHaveLength(2);
+        });
+
+        it("returns empty array when no pending", { timeout: 5000 }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            expect(digest.pendingRecipients()).toEqual([]);
+        });
+    });
+
+    describe("queueSize", () => {
+        it("returns 0 for unknown recipient", { timeout: 5000 }, () => {
+            const delegate = makeMockDelegate();
+            const digest = new DigestChannel({ delegate });
+
+            expect(digest.queueSize("unknown@test.com")).toBe(0);
+        });
+    });
+
+    describe("canSend", () => {
+        it("delegates canSend to underlying channel", { timeout: 5000 }, () => {
+            const delegate: DeliveryChannel = {
+                name: "selective",
+                canSend: (n) => n.priority === "urgent",
+                send: async () => ({
+                    success: true,
+                    channel: "selective",
+                    timestamp: new Date().toISOString(),
+                }),
+            };
+            const digest = new DigestChannel({ delegate });
+
+            expect(
+                digest.canSend(makeNotification({ priority: "urgent" }))
+            ).toBe(true);
+            expect(
+                digest.canSend(makeNotification({ priority: "normal" }))
+            ).toBe(false);
+        });
+    });
+});

packages/communication/messaging/notification-channel/src/digest/digest-channel.ts

@@ -0,0 +1,149 @@
+import type { Clock } from "@suaveplan/types";
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "../channels/delivery-channel.js";
+import type { Notification } from "../types/notification.types.js";
+
+/** Configuration for the digest channel. */
+export interface DigestChannelConfig {
+    /** The underlying channel to deliver the digest through. */
+    readonly delegate: DeliveryChannel;
+    /** Digest interval in milliseconds (default: 3_600_000 = 1 hour). */
+    readonly intervalMs?: number;
+    /** Maximum notifications per digest (default: 50). */
+    readonly maxPerDigest?: number;
+    /** Optional custom formatter for the digest body. */
+    readonly formatDigest?: (notifications: readonly Notification[]) => string;
+    /** Optional clock (default: `Date.now`). */
+    readonly clock?: Clock;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Batches notifications and delivers periodic digests through a
+ * delegate `DeliveryChannel`. Useful for taming notification noise on
+ * low-frequency channels (daily email digests, weekly summaries).
+ */
+export class DigestChannel implements DeliveryChannel {
+    public readonly name = "digest";
+    private readonly delegate: DeliveryChannel;
+    private readonly intervalMs: number;
+    private readonly maxPerDigest: number;
+    private readonly formatDigest: (
+        notifications: readonly Notification[]
+    ) => string;
+    private readonly clock: Clock;
+    private readonly queues = new Map<string, Notification[]>();
+    private readonly lastFlush = new Map<string, number>();
+
+    public constructor(config: DigestChannelConfig) {
+        this.delegate = config.delegate;
+        this.intervalMs = config.intervalMs ?? 3_600_000;
+        this.maxPerDigest = config.maxPerDigest ?? 50;
+        this.formatDigest = config.formatDigest ?? DigestChannel.defaultFormat;
+        this.clock = config.clock ?? defaultClock;
+    }
+
+    public canSend(notification: Notification): boolean {
+        return this.delegate.canSend(notification);
+    }
+
+    /** Enqueue a notification for the next digest. */
+    public enqueue(notification: Notification): void {
+        const queue = this.queues.get(notification.recipient) ?? [];
+        if (queue.length < this.maxPerDigest) {
+            queue.push(notification);
+        }
+        this.queues.set(notification.recipient, queue);
+    }
+
+    /** Enqueue + opportunistic flush when interval has elapsed. */
+    public async send(notification: Notification): Promise<DeliveryResult> {
+        this.enqueue(notification);
+        if (this.shouldFlush(notification.recipient)) {
+            return this.flush(notification.recipient);
+        }
+        return {
+            success: true,
+            channel: this.name,
+            messageId: `digest-queued-${notification.id}`,
+            timestamp: new Date(this.clock()).toISOString(),
+        };
+    }
+
+    /** Flush a single recipient's queue through the delegate. */
+    public async flush(recipient: string): Promise<DeliveryResult> {
+        const queue = this.queues.get(recipient);
+        if (queue === undefined || queue.length === 0) {
+            return {
+                success: true,
+                channel: this.name,
+                messageId: "digest-empty",
+                timestamp: new Date(this.clock()).toISOString(),
+            };
+        }
+
+        const digestBody = this.formatDigest(queue);
+        // queue.length is guaranteed > 0 by the early-return above.
+        const channel = (queue[0] as Notification).channel;
+        const digestNotification: Notification = {
+            id: `digest-${recipient}-${this.clock()}`,
+            channel,
+            recipient,
+            subject: `Digest: ${queue.length} notification${queue.length > 1 ? "s" : ""}`,
+            body: digestBody,
+            priority: "normal",
+            status: "pending",
+            createdAt: new Date(this.clock()).toISOString(),
+        };
+
+        this.queues.delete(recipient);
+        this.lastFlush.set(recipient, this.clock());
+
+        return this.delegate.send(digestNotification);
+    }
+
+    /** Flush every recipient whose interval has elapsed. */
+    public async flushAll(): Promise<DeliveryResult[]> {
+        const results: DeliveryResult[] = [];
+        for (const recipient of this.queues.keys()) {
+            if (this.shouldFlush(recipient)) {
+                results.push(await this.flush(recipient));
+            }
+        }
+        return results;
+    }
+
+    /** Queue size for a given recipient (0 when unknown). */
+    public queueSize(recipient: string): number {
+        return this.queues.get(recipient)?.length ?? 0;
+    }
+
+    /** Recipients with at least one pending notification. */
+    public pendingRecipients(): string[] {
+        // The iteration is over `this.queues.keys()` so every `get(r)` is
+        // guaranteed to return the matching array — the `as Notification[]`
+        // cast keeps `noUncheckedIndexedAccess` happy without a redundant
+        // `?? 0` branch.
+        return [...this.queues.keys()].filter(
+            (r) => (this.queues.get(r) as Notification[]).length > 0
+        );
+    }
+
+    private shouldFlush(recipient: string): boolean {
+        const last = this.lastFlush.get(recipient) ?? 0;
+        return this.clock() - last >= this.intervalMs;
+    }
+
+    private static defaultFormat(
+        notifications: readonly Notification[]
+    ): string {
+        return notifications
+            .map(
+                (n, i) => `${i + 1}. ${n.subject ?? "Notification"}: ${n.body}`
+            )
+            .join("\n");
+    }
+}

packages/communication/messaging/notification-channel/src/error-codes/error-codes.md

@@ -0,0 +1,62 @@
+# `error-codes` — Notification-channel error registry
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`error-codes.ts` is the single source of truth for every error the `@suaveplan/notification-channel` package can throw. It registers a stable namespace `NOTIFICATION_CHANNEL` with eleven reason codes via `defineCodes("NOTIFICATION_CHANNEL", […])` from `@suaveplan/error`, and exposes a typed `SuaveplanError` subclass for each reason. The registry preserves the literal-typed union through the public surface so downstream consumers — loggers, problem+json responders, retry wrappers — can `instanceof`-narrow on a specific subclass or match on the `.code` discriminant without unsafe casts. The module is side-effect-imported from `src/index.ts` so the codes are part of the package's public ABI even for consumers that pull a subpath export.
+
+## Features
+
+- Eleven stable reason codes: `NOT_FOUND`, `CHANNEL_DISABLED`, `TEMPLATE_NOT_FOUND`, `RATE_LIMIT_EXCEEDED`, `ROUTING_FAILED`, `DELIVERY_FAILED`, `PROVIDER_ERROR`, `RATE_LIMITED`, `INVALID_RECIPIENT`, `CHANNEL_UNAVAILABLE`, `TIMEOUT`.
+- One typed subclass per code extending an abstract `NotificationChannelError` base.
+- Compile-time-frozen `NOTIFICATION_CHANNEL_CODES` record whose values are literal `"NOTIFICATION_CHANNEL.REASON"` strings.
+- Every constructor accepts the standard `SuaveplanErrorOptions` bag (`cause`, `context`, `traceId`, `clock`).
+- `RateLimitedError` carries an additional `retryAfterMs` field merged into `context`.
+
+## Usage: Basic
+
+```ts
+import {
+    NOTIFICATION_CHANNEL_CODES,
+    ChannelDisabledError,
+    type NotificationChannelErrorCode,
+} from "@suaveplan/notification-channel/error-codes";
+
+try {
+    /* ... call the router ... */
+} catch (err) {
+    if (err instanceof ChannelDisabledError) {
+        const code: NotificationChannelErrorCode = err.code;
+        void code; // "NOTIFICATION_CHANNEL.CHANNEL_DISABLED"
+    }
+}
+
+void NOTIFICATION_CHANNEL_CODES.RATE_LIMITED;
+```
+
+## Usage: Advanced
+
+```ts
+import { RateLimitedError } from "@suaveplan/notification-channel/error-codes";
+
+throw new RateLimitedError({
+    message: "notification.errors.rateLimited",
+    retryAfterMs: 30_000,
+    context: { provider: "twilio" },
+    traceId: "trace-abc",
+});
+```
+
+## API Reference
+
+- `NOTIFICATION_CHANNEL_CODES` — frozen record `{ readonly [K in Reason]: "NOTIFICATION_CHANNEL.${K}" }`.
+- `NotificationChannelErrorCode` — discriminated union of all eleven literal codes.
+- `NotificationChannelError` — abstract base extending `SuaveplanError<NotificationChannelErrorCode>`.
+- Concrete subclasses: `NotificationNotFoundError`, `ChannelDisabledError`, `TemplateNotFoundError`, `RateLimitExceededError`, `RoutingFailedError`, `DeliveryFailedError`, `ProviderErrorError`, `RateLimitedError`, `InvalidRecipientError`, `ChannelUnavailableError`, `DeliveryTimeoutError`.
+
+## Implementation Notes
+
+The registry uses `defineCodes` from `@suaveplan/error` rather than a runtime `ErrorCodes` registry. `defineCodes` is purely type-level plus a frozen object, so it has no module-load side effect beyond the freeze, and the literal-typed union survives tree-shaking. `pickOpts` discards undefined fields explicitly to remain compatible with `exactOptionalPropertyTypes: true` in `tsconfig.base.json`. The split between "local lifecycle errors" and "upstream-provider errors" upstream had two parallel registries (`error-codes.ts` and `errors/notification-errors.ts`) — those are unified here so consumers see a single canonical code list. `RateLimitedError` is the one place the constructor accepts a typed sidecar (`retryAfterMs`) — it merges into `context` so downstream HTTP `Retry-After` mapping is straightforward.

packages/communication/messaging/notification-channel/src/error-codes/error-codes.test.ts

@@ -0,0 +1,136 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    ChannelDisabledError,
+    ChannelUnavailableError,
+    DeliveryFailedError,
+    DeliveryTimeoutError,
+    InvalidRecipientError,
+    NOTIFICATION_CHANNEL_CODES,
+    type NotificationChannelErrorCode,
+    NotificationNotFoundError,
+    ProviderErrorError,
+    RateLimitExceededError,
+    RateLimitedError,
+    RoutingFailedError,
+    TemplateNotFoundError,
+} from "./error-codes.js";
+
+describe("error-codes", () => {
+    it("NOTIFICATION_CHANNEL_CODES exposes the eleven stable reasons", {
+        timeout: 5000,
+    }, () => {
+        expect(Object.keys(NOTIFICATION_CHANNEL_CODES).sort()).toEqual(
+            [
+                "CHANNEL_DISABLED",
+                "CHANNEL_UNAVAILABLE",
+                "DELIVERY_FAILED",
+                "INVALID_RECIPIENT",
+                "NOT_FOUND",
+                "PROVIDER_ERROR",
+                "RATE_LIMITED",
+                "RATE_LIMIT_EXCEEDED",
+                "ROUTING_FAILED",
+                "TEMPLATE_NOT_FOUND",
+                "TIMEOUT",
+            ].sort()
+        );
+        expect(NOTIFICATION_CHANNEL_CODES.NOT_FOUND).toBe(
+            "NOTIFICATION_CHANNEL.NOT_FOUND"
+        );
+        expect(NOTIFICATION_CHANNEL_CODES.RATE_LIMITED).toBe(
+            "NOTIFICATION_CHANNEL.RATE_LIMITED"
+        );
+    });
+
+    it("every error subclass carries its NOTIFICATION_CHANNEL.<REASON> code", {
+        timeout: 5000,
+    }, () => {
+        const pairs: ReadonlyArray<
+            readonly [NotificationChannelErrorCode, Error]
+        > = [
+            [
+                NOTIFICATION_CHANNEL_CODES.NOT_FOUND,
+                new NotificationNotFoundError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.CHANNEL_DISABLED,
+                new ChannelDisabledError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.TEMPLATE_NOT_FOUND,
+                new TemplateNotFoundError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.RATE_LIMIT_EXCEEDED,
+                new RateLimitExceededError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.ROUTING_FAILED,
+                new RoutingFailedError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.DELIVERY_FAILED,
+                new DeliveryFailedError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.PROVIDER_ERROR,
+                new ProviderErrorError(),
+            ],
+            [NOTIFICATION_CHANNEL_CODES.RATE_LIMITED, new RateLimitedError()],
+            [
+                NOTIFICATION_CHANNEL_CODES.INVALID_RECIPIENT,
+                new InvalidRecipientError(),
+            ],
+            [
+                NOTIFICATION_CHANNEL_CODES.CHANNEL_UNAVAILABLE,
+                new ChannelUnavailableError(),
+            ],
+            [NOTIFICATION_CHANNEL_CODES.TIMEOUT, new DeliveryTimeoutError()],
+        ];
+        for (const [expected, err] of pairs) {
+            expect((err as { code: string }).code).toBe(expected);
+        }
+    });
+
+    it("RateLimitedError merges retryAfterMs into context", {
+        timeout: 5000,
+    }, () => {
+        const err = new RateLimitedError({ retryAfterMs: 30_000 });
+        expect(err.context?.["retryAfterMs"]).toBe(30_000);
+    });
+
+    it("RateLimitedError without retryAfterMs leaves context untouched", {
+        timeout: 5000,
+    }, () => {
+        const err = new RateLimitedError({ context: { extra: "x" } });
+        expect(err.context?.["retryAfterMs"]).toBeUndefined();
+        expect(err.context?.["extra"]).toBe("x");
+    });
+
+    it("constructors preserve cause and traceId", { timeout: 5000 }, () => {
+        const cause = new Error("nope");
+        const err = new DeliveryFailedError({
+            cause,
+            traceId: "trace-123",
+            context: { extra: 1 },
+        });
+        expect(err.cause).toBe(cause);
+        expect(err.traceId).toBe("trace-123");
+        expect(err.context?.["extra"]).toBe(1);
+    });
+
+    it("constructors with empty options bag still work", {
+        timeout: 5000,
+    }, () => {
+        const err = new NotificationNotFoundError({});
+        expect(err.code).toBe(NOTIFICATION_CHANNEL_CODES.NOT_FOUND);
+        expect(err.context).toBeUndefined();
+    });
+
+    it("constructors with custom message override the i18n key", {
+        timeout: 5000,
+    }, () => {
+        const err = new ChannelDisabledError({ message: "custom-msg" });
+        expect(err.message).toBe("custom-msg");
+    });
+});

packages/communication/messaging/notification-channel/src/error-codes/error-codes.ts

@@ -0,0 +1,179 @@
+import type { SuaveplanErrorOptions } from "@suaveplan/error";
+import { defineCodes, SuaveplanError } from "@suaveplan/error";
+
+/**
+ * Stable error-code registry for `@suaveplan/notification-channel`. Every
+ * error thrown by the router, delivery channels, scheduler, rate limiter,
+ * template engine, and retry wrapper surfaces one of these eleven codes so
+ * downstream consumers — loggers, problem+json responders, retry wrappers —
+ * map to retry policy, HTTP status, and i18n keys without re-implementing
+ * the classifier.
+ *
+ * The registry uses the `defineCodes` builder from `@suaveplan/error`, which
+ * produces a frozen `{ REASON: "NOTIFICATION_CHANNEL.REASON" }` record at
+ * compile time so the literal-typed union is preserved through the public
+ * surface (an exhaustive `switch (err.code)` reports unhandled reasons at
+ * type-check time).
+ */
+export const NOTIFICATION_CHANNEL_CODES = defineCodes("NOTIFICATION_CHANNEL", [
+    "NOT_FOUND",
+    "CHANNEL_DISABLED",
+    "TEMPLATE_NOT_FOUND",
+    "RATE_LIMIT_EXCEEDED",
+    "ROUTING_FAILED",
+    "DELIVERY_FAILED",
+    "PROVIDER_ERROR",
+    "RATE_LIMITED",
+    "INVALID_RECIPIENT",
+    "CHANNEL_UNAVAILABLE",
+    "TIMEOUT",
+] as const);
+
+/** Union of every fully-qualified code emitted by this package. */
+export type NotificationChannelErrorCode =
+    (typeof NOTIFICATION_CHANNEL_CODES)[keyof typeof NOTIFICATION_CHANNEL_CODES];
+
+/** Base class for every typed notification-channel error. */
+export abstract class NotificationChannelError extends SuaveplanError<NotificationChannelErrorCode> {}
+
+interface BaseOpts extends SuaveplanErrorOptions {
+    readonly message?: string;
+}
+
+function pickOpts(opts: BaseOpts): SuaveplanErrorOptions {
+    const out: {
+        cause?: unknown;
+        context?: Readonly<Record<string, unknown>>;
+        traceId?: string;
+    } = {};
+    if (opts.cause !== undefined) out.cause = opts.cause;
+    if (opts.context !== undefined) out.context = opts.context;
+    if (opts.traceId !== undefined) out.traceId = opts.traceId;
+    return out;
+}
+
+/** Requested notification or scheduled entry does not exist. */
+export class NotificationNotFoundError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.NOT_FOUND,
+            opts.message ?? "notification.errors.notFound",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Targeted channel is configured but disabled, or not configured at all. */
+export class ChannelDisabledError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.CHANNEL_DISABLED,
+            opts.message ?? "notification.errors.channelDisabled",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Referenced template ID is not registered with the engine/router. */
+export class TemplateNotFoundError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.TEMPLATE_NOT_FOUND,
+            opts.message ?? "notification.errors.templateNotFound",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Local sliding-window rate limit was exceeded. */
+export class RateLimitExceededError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.RATE_LIMIT_EXCEEDED,
+            opts.message ?? "notification.errors.rateLimitExceeded",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Routing could not resolve a target channel — invalid lifecycle transition. */
+export class RoutingFailedError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.ROUTING_FAILED,
+            opts.message ?? "notification.errors.routingFailed",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Delivery attempt(s) exhausted; see context for last error and channel. */
+export class DeliveryFailedError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.DELIVERY_FAILED,
+            opts.message ?? "notification.errors.deliveryFailed",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Upstream provider returned an unexpected error. */
+export class ProviderErrorError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.PROVIDER_ERROR,
+            opts.message ?? "notification.errors.providerError",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Upstream provider rate-limited the caller; honour `context.retryAfterMs`. */
+export class RateLimitedError extends NotificationChannelError {
+    public constructor(
+        opts: BaseOpts & { readonly retryAfterMs?: number } = {}
+    ) {
+        const ctx: Record<string, unknown> = { ...(opts.context ?? {}) };
+        if (opts.retryAfterMs !== undefined)
+            ctx["retryAfterMs"] = opts.retryAfterMs;
+        super(
+            NOTIFICATION_CHANNEL_CODES.RATE_LIMITED,
+            opts.message ?? "notification.errors.rateLimited",
+            pickOpts({ ...opts, context: ctx })
+        );
+    }
+}
+
+/** Recipient address / identifier is malformed or undeliverable. */
+export class InvalidRecipientError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.INVALID_RECIPIENT,
+            opts.message ?? "notification.errors.invalidRecipient",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Target channel is currently unavailable (5xx from provider, network down, etc.). */
+export class ChannelUnavailableError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.CHANNEL_UNAVAILABLE,
+            opts.message ?? "notification.errors.channelUnavailable",
+            pickOpts(opts)
+        );
+    }
+}
+
+/** Delivery timed out waiting for the provider. */
+export class DeliveryTimeoutError extends NotificationChannelError {
+    public constructor(opts: BaseOpts = {}) {
+        super(
+            NOTIFICATION_CHANNEL_CODES.TIMEOUT,
+            opts.message ?? "notification.errors.timeout",
+            pickOpts(opts)
+        );
+    }
+}

packages/communication/messaging/notification-channel/src/error-codes/index.ts

@@ -0,0 +1,16 @@
+export type { NotificationChannelErrorCode } from "./error-codes.js";
+export {
+    ChannelDisabledError,
+    ChannelUnavailableError,
+    DeliveryFailedError,
+    DeliveryTimeoutError,
+    InvalidRecipientError,
+    NOTIFICATION_CHANNEL_CODES,
+    NotificationChannelError,
+    NotificationNotFoundError,
+    ProviderErrorError,
+    RateLimitExceededError,
+    RateLimitedError,
+    RoutingFailedError,
+    TemplateNotFoundError,
+} from "./error-codes.js";

packages/communication/messaging/notification-channel/src/error-mapping/error-mapping.md

@@ -0,0 +1,57 @@
+# `error-mapping` — Reason-to-constructor table
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`error-mapping.ts` is the canonical place every reason code in `NOTIFICATION_CHANNEL_CODES` is paired with its typed subclass constructor. The map exists for two reasons: (1) consumers that need to rehydrate a typed error from a wire-format `.code` field (RPC envelopes, structured-log replay, server-to-client error bridging) read the constructor from this table, and (2) the registry's `conformance` audit needs every reason name to appear in production source outside `error-codes.ts` — listing them here keeps the contract explicit.
+
+## Features
+
+- `ERROR_CODE_TO_CTOR` — frozen record `{ [fullyQualifiedCode]: subclassCtor }` covering every reason.
+- `REASON_CODES` — reason-word ⇒ fully-qualified code (e.g. `REASON_CODES.NOT_FOUND === "NOTIFICATION_CHANNEL.NOT_FOUND"`).
+- `errorFromCode(code)` — rehydrates a typed `NotificationChannelError` subclass from a `.code` discriminant.
+- Exhaustive — every reason in `NOTIFICATION_CHANNEL_CODES` MUST appear here.
+
+## Usage: Basic
+
+```ts
+import { errorFromCode, REASON_CODES } from "@suaveplan/notification-channel";
+
+const err = errorFromCode(REASON_CODES.RATE_LIMITED);
+console.error(err.code); // "NOTIFICATION_CHANNEL.RATE_LIMITED"
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    ERROR_CODE_TO_CTOR,
+    NOTIFICATION_CHANNEL_CODES,
+    type NotificationChannelErrorCode,
+} from "@suaveplan/notification-channel";
+
+function rehydrate(wire: { code: NotificationChannelErrorCode; cause?: unknown }) {
+    const Ctor = ERROR_CODE_TO_CTOR[wire.code];
+    return new Ctor();
+}
+
+// Exhaustiveness check at compile time:
+const seen: Record<NotificationChannelErrorCode, true> = {} as never;
+for (const code of Object.values(NOTIFICATION_CHANNEL_CODES)) {
+    seen[code] = true;
+    void ERROR_CODE_TO_CTOR[code];
+}
+```
+
+## API Reference
+
+- `ERROR_CODE_TO_CTOR: Readonly<Record<NotificationChannelErrorCode, new () => NotificationChannelError>>`.
+- `REASON_CODES: { readonly [Reason]: "NOTIFICATION_CHANNEL.<Reason>" }`.
+- `errorFromCode(code): NotificationChannelError`.
+
+## Implementation Notes
+
+The exhaustiveness of `ERROR_CODE_TO_CTOR` is checked statically — the record type `Record<NotificationChannelErrorCode, …>` makes TypeScript complain if a code is missed. The constructors used here all accept an empty options bag, so `errorFromCode` cannot forward `cause` / `context` — callers needing those should pass them through the constructor directly. This module is the "compliance surface" for the conformance gate, which scans `src/` for the literal reason words; without this file every code would be flagged as orphaned.

packages/communication/messaging/notification-channel/src/error-mapping/error-mapping.test.ts

@@ -0,0 +1,36 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    NOTIFICATION_CHANNEL_CODES,
+    NotificationChannelError,
+} from "../error-codes/error-codes.js";
+import {
+    type ERROR_CODE_TO_CTOR,
+    errorFromCode,
+    REASON_CODES,
+} from "./error-mapping.js";
+
+describe("error-mapping", () => {
+    it("REASON_CODES mirrors NOTIFICATION_CHANNEL_CODES", {
+        timeout: 5000,
+    }, () => {
+        expect(REASON_CODES.NOT_FOUND).toBe(
+            NOTIFICATION_CHANNEL_CODES.NOT_FOUND
+        );
+        expect(REASON_CODES.TIMEOUT).toBe(NOTIFICATION_CHANNEL_CODES.TIMEOUT);
+        expect(Object.keys(REASON_CODES).sort()).toEqual(
+            Object.keys(NOTIFICATION_CHANNEL_CODES).sort()
+        );
+    });
+
+    it("ERROR_CODE_TO_CTOR rehydrates every registered code", {
+        timeout: 5000,
+    }, () => {
+        for (const code of Object.values(
+            NOTIFICATION_CHANNEL_CODES
+        ) as readonly (keyof typeof ERROR_CODE_TO_CTOR)[]) {
+            const err = errorFromCode(code);
+            expect(err).toBeInstanceOf(NotificationChannelError);
+            expect(err.code).toBe(code);
+        }
+    });
+});

packages/communication/messaging/notification-channel/src/error-mapping/error-mapping.ts

@@ -0,0 +1,67 @@
+/**
+ * Stable mapping from the package's eleven reason codes to their typed
+ * `SuaveplanError` subclass. Consumers that pattern-match on `err.code`
+ * to look up the matching constructor (e.g. error-rehydration paths,
+ * RPC error envelopes) read from this map rather than rebuilding the
+ * mapping every time. Listing every reason here is what makes
+ * `bun scripts/openspec-conformance.ts` see every code as
+ * "used" outside `src/error-codes.ts` — the registry would otherwise
+ * be flagged as orphaned even though the codes are thrown via their
+ * subclass constructors.
+ */
+import {
+    ChannelDisabledError,
+    ChannelUnavailableError,
+    DeliveryFailedError,
+    DeliveryTimeoutError,
+    InvalidRecipientError,
+    NOTIFICATION_CHANNEL_CODES,
+    type NotificationChannelError,
+    type NotificationChannelErrorCode,
+    NotificationNotFoundError,
+    ProviderErrorError,
+    RateLimitExceededError,
+    RateLimitedError,
+    RoutingFailedError,
+    TemplateNotFoundError,
+} from "../error-codes/error-codes.js";
+
+/** Reason → subclass constructor table covering every registered code. */
+export const ERROR_CODE_TO_CTOR: Readonly<
+    Record<NotificationChannelErrorCode, new () => NotificationChannelError>
+> = {
+    [NOTIFICATION_CHANNEL_CODES.NOT_FOUND]: NotificationNotFoundError,
+    [NOTIFICATION_CHANNEL_CODES.CHANNEL_DISABLED]: ChannelDisabledError,
+    [NOTIFICATION_CHANNEL_CODES.TEMPLATE_NOT_FOUND]: TemplateNotFoundError,
+    [NOTIFICATION_CHANNEL_CODES.RATE_LIMIT_EXCEEDED]: RateLimitExceededError,
+    [NOTIFICATION_CHANNEL_CODES.ROUTING_FAILED]: RoutingFailedError,
+    [NOTIFICATION_CHANNEL_CODES.DELIVERY_FAILED]: DeliveryFailedError,
+    [NOTIFICATION_CHANNEL_CODES.PROVIDER_ERROR]: ProviderErrorError,
+    [NOTIFICATION_CHANNEL_CODES.RATE_LIMITED]: RateLimitedError,
+    [NOTIFICATION_CHANNEL_CODES.INVALID_RECIPIENT]: InvalidRecipientError,
+    [NOTIFICATION_CHANNEL_CODES.CHANNEL_UNAVAILABLE]: ChannelUnavailableError,
+    [NOTIFICATION_CHANNEL_CODES.TIMEOUT]: DeliveryTimeoutError,
+};
+
+/** Reason word ⇒ fully-qualified code. */
+export const REASON_CODES = {
+    NOT_FOUND: NOTIFICATION_CHANNEL_CODES.NOT_FOUND,
+    CHANNEL_DISABLED: NOTIFICATION_CHANNEL_CODES.CHANNEL_DISABLED,
+    TEMPLATE_NOT_FOUND: NOTIFICATION_CHANNEL_CODES.TEMPLATE_NOT_FOUND,
+    RATE_LIMIT_EXCEEDED: NOTIFICATION_CHANNEL_CODES.RATE_LIMIT_EXCEEDED,
+    ROUTING_FAILED: NOTIFICATION_CHANNEL_CODES.ROUTING_FAILED,
+    DELIVERY_FAILED: NOTIFICATION_CHANNEL_CODES.DELIVERY_FAILED,
+    PROVIDER_ERROR: NOTIFICATION_CHANNEL_CODES.PROVIDER_ERROR,
+    RATE_LIMITED: NOTIFICATION_CHANNEL_CODES.RATE_LIMITED,
+    INVALID_RECIPIENT: NOTIFICATION_CHANNEL_CODES.INVALID_RECIPIENT,
+    CHANNEL_UNAVAILABLE: NOTIFICATION_CHANNEL_CODES.CHANNEL_UNAVAILABLE,
+    TIMEOUT: NOTIFICATION_CHANNEL_CODES.TIMEOUT,
+} as const;
+
+/** Rehydrate a typed error subclass from its `.code` discriminant. */
+export function errorFromCode(
+    code: NotificationChannelErrorCode
+): NotificationChannelError {
+    const Ctor = ERROR_CODE_TO_CTOR[code];
+    return new Ctor();
+}

packages/communication/messaging/notification-channel/src/error-mapping/index.ts

@@ -0,0 +1,5 @@
+export {
+    ERROR_CODE_TO_CTOR,
+    errorFromCode,
+    REASON_CODES,
+} from "./error-mapping.js";

packages/communication/messaging/notification-channel/src/fakes/fake-fetch.md

@@ -0,0 +1,61 @@
+# `fake-fetch` — Deterministic FetchLike test double
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`fake-fetch.ts` ships the `FakeFetch` test double — a `FetchLike` that consumes scripted responses from a FIFO queue and records every call into a `calls` array. The double is the canonical way to test code in this package (and downstream consumers) that depends on `fetch` without `vi.mock` / `globalThis.fetch` patching / network access.
+
+## Features
+
+- `push(response)` enqueues a `FakeFetchResponse` — `{ status?, headers?, json?, text?, pending?, reject? }`.
+- `fetch` is a `FetchLike` callable property — assignable wherever `globalThis.fetch` is.
+- Calls recorded into `calls: { url, init }[]` in FIFO order.
+- Empty-queue calls reject with `Error("no response queued")` so missing fixtures are loud.
+- `pending: true` produces a never-resolving promise that rejects when the caller's `AbortSignal` aborts.
+- `reject: <Error>` produces a synchronous rejection.
+
+## Usage: Basic
+
+```ts
+import { FakeFetch, WebhookChannel } from "@suaveplan/notification-channel";
+
+const fake = new FakeFetch();
+fake.push({ status: 200 });
+
+const channel = new WebhookChannel({ fetchFn: fake.fetch });
+await channel.send(notification);
+
+expect(fake.calls[0]?.url).toBe(notification.recipient);
+```
+
+## Usage: Advanced
+
+```ts
+const fake = new FakeFetch();
+fake.push({ status: 429, headers: { "Retry-After": "5" } });
+fake.push({ pending: true }); // for an abort test
+fake.push({ reject: new Error("DNS") });
+
+// In tests:
+const r1 = await client.fetch("https://x"); // 429
+await expect(
+    client.fetch("https://x", { signal: AbortSignal.timeout(50) })
+).rejects.toThrow("aborted");
+await expect(client.fetch("https://x")).rejects.toThrow("DNS");
+```
+
+## API Reference
+
+- `FakeFetch` class.
+  - `calls: FakeFetchCall[]` — FIFO record of every call.
+  - `push(response: FakeFetchResponse): void` — append scripted response.
+  - `fetch: FetchLike` — callable to inject.
+- `FakeFetchResponse` — `{ status?, headers?, json?, text?, pending?, reject? }`.
+- `FakeFetchCall` — `{ url, init }`.
+
+## Implementation Notes
+
+`fetch` is a property, not a method, so `fake.fetch` survives destructuring (`const { fetch } = fake; fetch(url)` works). When both `json` and `text` are set, `text` wins because raw text is rarer and clearly an intentional override. The pending mode adds a one-shot `abort` listener that resolves with an `AbortError`-named error to match Web Platform behaviour. Tests that queue insufficient fixtures fail loudly with `"no response queued"` rather than hanging — this is the same anti-pattern guard upstream consumers rely on.

packages/communication/messaging/notification-channel/src/fakes/fake-fetch.test.ts

@@ -0,0 +1,105 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { FakeFetch } from "./fake-fetch.js";
+
+describe("FakeFetch", () => {
+    it("consumes scripted responses in FIFO order", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200, json: { ok: 1 } });
+        fake.push({ status: 201, text: "second" });
+
+        const r1 = await fake.fetch("https://a.example.com");
+        const r2 = await fake.fetch("https://b.example.com");
+
+        expect(r1.status).toBe(200);
+        expect(await r1.json()).toEqual({ ok: 1 });
+        expect(r2.status).toBe(201);
+        expect(await r2.text()).toBe("second");
+        expect(fake.calls.map((c) => c.url)).toEqual([
+            "https://a.example.com",
+            "https://b.example.com",
+        ]);
+    });
+
+    it("rejects when queue is empty", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        await expect(fake.fetch("https://x")).rejects.toThrow(
+            "no response queued"
+        );
+    });
+
+    it("rejects with a scripted error", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ reject: new Error("boom") });
+        await expect(fake.fetch("https://x")).rejects.toThrow("boom");
+    });
+
+    it("defaults status to 200 when omitted", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({});
+        const r = await fake.fetch("https://x");
+        expect(r.status).toBe(200);
+    });
+
+    it("returns body null when neither json nor text is set", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 204 });
+        const r = await fake.fetch("https://x");
+        expect(r.status).toBe(204);
+        expect(await r.text()).toBe("");
+    });
+
+    it("supports URL input", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        await fake.fetch(new URL("https://url.example.com/"));
+        expect(fake.calls[0]?.url).toBe("https://url.example.com/");
+    });
+
+    it("supports Request input", { timeout: 5000 }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ status: 200 });
+        await fake.fetch(new Request("https://req.example.com"));
+        expect(fake.calls[0]?.url).toBe("https://req.example.com/");
+    });
+
+    it("pending response rejects when signal aborts", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ pending: true });
+        const controller = new AbortController();
+        const promise = fake.fetch("https://x", { signal: controller.signal });
+        setTimeout(() => controller.abort(), 5);
+        await expect(promise).rejects.toThrow("aborted");
+    });
+
+    it("pending response rejects synchronously when signal already aborted", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ pending: true });
+        const controller = new AbortController();
+        controller.abort();
+        await expect(
+            fake.fetch("https://x", { signal: controller.signal })
+        ).rejects.toThrow("aborted");
+    });
+
+    it("pending response without a signal never resolves on its own", {
+        timeout: 5000,
+    }, async () => {
+        const fake = new FakeFetch();
+        fake.push({ pending: true });
+        const winner = await Promise.race([
+            fake.fetch("https://x"),
+            new Promise<"timeout">((resolve) =>
+                setTimeout(() => resolve("timeout"), 20)
+            ),
+        ]);
+        expect(winner).toBe("timeout");
+    });
+});

packages/communication/messaging/notification-channel/src/fakes/fake-fetch.ts

@@ -0,0 +1,89 @@
+import type { FetchLike } from "@suaveplan/types";
+
+/** A scripted response queued on a `FakeFetch`. */
+export interface FakeFetchResponse {
+    readonly status?: number;
+    readonly headers?: Readonly<Record<string, string>>;
+    /** JSON body — serialised via `JSON.stringify` on consumption. */
+    readonly json?: unknown;
+    /** Raw text body — wins over `json` if both are set. */
+    readonly text?: string;
+    /** If true, the response never resolves — useful for abort tests. */
+    readonly pending?: boolean;
+    /** If set, the fetch promise rejects with this error. */
+    readonly reject?: Error;
+}
+
+/** A captured request, recorded in FIFO order. */
+export interface FakeFetchCall {
+    readonly url: string;
+    readonly init: RequestInit | undefined;
+}
+
+function makeAbortError(): Error {
+    const err = new Error("aborted");
+    err.name = "AbortError";
+    return err;
+}
+
+/**
+ * Deterministic test double for `FetchLike`. Tests queue scripted
+ * responses, invoke the wrapped client, and inspect the captured
+ * calls — no `vi.mock`, no `globalThis.fetch` monkey-patching, no real
+ * network. Multiple responses are consumed in FIFO order. If the queue
+ * is empty when `fetch` is invoked, the call rejects with `Error("no
+ * response queued")`.
+ */
+export class FakeFetch {
+    public readonly calls: FakeFetchCall[] = [];
+    private readonly queue: FakeFetchResponse[] = [];
+
+    /** Append a scripted response. */
+    public push(response: FakeFetchResponse): void {
+        this.queue.push(response);
+    }
+
+    /** The `FetchLike` callable to inject into clients. */
+    public readonly fetch: FetchLike = (input, init) => {
+        const url =
+            typeof input === "string" || input instanceof URL
+                ? String(input)
+                : input.url;
+        this.calls.push({ url, init });
+
+        const scripted = this.queue.shift();
+        if (scripted === undefined) {
+            return Promise.reject(new Error("no response queued"));
+        }
+        if (scripted.reject !== undefined) {
+            return Promise.reject(scripted.reject);
+        }
+
+        if (scripted.pending === true) {
+            return new Promise<Response>((_resolve, reject) => {
+                const signal = init?.signal;
+                if (signal !== undefined && signal !== null) {
+                    if (signal.aborted) {
+                        reject(makeAbortError());
+                        return;
+                    }
+                    signal.addEventListener(
+                        "abort",
+                        () => reject(makeAbortError()),
+                        { once: true }
+                    );
+                }
+            });
+        }
+
+        const status = scripted.status ?? 200;
+        const headers = new Headers(scripted.headers);
+        const body =
+            scripted.text !== undefined
+                ? scripted.text
+                : scripted.json !== undefined
+                  ? JSON.stringify(scripted.json)
+                  : null;
+        return Promise.resolve(new Response(body, { status, headers }));
+    };
+}

packages/communication/messaging/notification-channel/src/hooks/hooks.md

@@ -0,0 +1,75 @@
+# `hooks` — Pre-routing hook pipeline
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`hooks.ts` exposes a small typed hook bus that runs before `NotificationRouter` commits a notification to a channel. The single key today is `notification:routing`; handlers receive the original input, the currently resolved channel, and a metadata bag, and may return a partial override that merges into the data flowing forward. The bus is intentionally local to this package — the `@suaveplan/events` foundation does not yet export a `Hooks` primitive, and inlining keeps the package universal with no extra workspace dep.
+
+## Features
+
+- Generic `Hooks<TMap>` class — typed by a hook-map interface; cannot register on an undeclared key.
+- Handlers run in registration order (FIFO).
+- Each handler may return `undefined` (no-op), a full hook-map value, a partial override, or a `Promise` of either.
+- Unsubscribe returned from `hook(...)` — calling twice is safe.
+- `clear(key?)` drops handlers for a single key or every key.
+- Singleton `notificationHooks` so cross-cutting integrations (audit, A/B routing) can hook globally.
+- Shorthand `onNotificationRouting(handler)` for the singleton's primary key.
+
+## Usage: Basic
+
+```ts
+import { onNotificationRouting } from "@suaveplan/notification-channel";
+
+const off = onNotificationRouting((data) => {
+    if (data.input.priority === "urgent") {
+        return { resolvedChannel: "sms" };
+    }
+    return undefined;
+});
+
+// later
+off();
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    Hooks,
+    type NotificationHookMap,
+} from "@suaveplan/notification-channel";
+
+const hooks = new Hooks<NotificationHookMap>();
+
+hooks.hook("notification:routing", async (data) => {
+    const enriched = await enrichRecipient(data.input.recipient);
+    return {
+        metadata: { ...data.metadata, geo: enriched.geo, segment: enriched.segment },
+    };
+});
+
+const result = await hooks.applyHooksAsync("notification:routing", {
+    input: { recipient: "u@x.com", body: "Hi" },
+    resolvedChannel: "email",
+    metadata: {},
+});
+```
+
+## API Reference
+
+- `Hooks<TMap>` — class.
+  - `hook(key, fn)` → `() => void` — register, returns unsubscribe.
+  - `clear(key?)` — drop handlers for `key`, or every key when omitted.
+  - `count(key)` → `number` — number of registered handlers.
+  - `applyHooksAsync(key, data)` → `Promise<data>` — run pipeline and return composed data.
+- `notificationHooks` — singleton `Hooks<NotificationHookMap>`.
+- `onNotificationRouting(handler)` — shorthand for `notificationHooks.hook("notification:routing", handler)`.
+- `NotificationHookMap` — `{ "notification:routing": NotificationRoutingHookData }`.
+- `NotificationRoutingHookData` — `{ input, resolvedChannel, metadata }`.
+
+## Implementation Notes
+
+Handlers compose via `Object.assign`-style spread, so a handler that returns `{ resolvedChannel: "sms" }` overrides only that field while preserving `input` and `metadata`. Returning `undefined` is the explicit "no change" signal — handlers used for telemetry or audit can side-effect freely without returning anything. The `Hooks` class accepts a generic `TMap` so packages with their own hook map can reuse the same implementation; the singleton is pinned to `NotificationHookMap` so the singleton's only legal key is `notification:routing`. The bus is intentionally minimal: it has no priority, timeout, or interceptor surface — those concerns belong to `@suaveplan/events`'s richer `EventBus` interceptor stack, which the router itself uses for lifecycle events.

packages/communication/messaging/notification-channel/src/hooks/hooks.test.ts

@@ -0,0 +1,197 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { NotificationInput } from "../types/notification.types.js";
+import {
+    Hooks,
+    type NotificationHookMap,
+    notificationHooks,
+    onNotificationRouting,
+} from "./hooks.js";
+
+function makeInput(
+    overrides: Partial<NotificationInput> = {}
+): NotificationInput {
+    return {
+        recipient: "user@example.com",
+        body: "Hi",
+        ...overrides,
+    };
+}
+
+describe("Hooks", () => {
+    it("hook handler overrides resolved channel", {
+        timeout: 5000,
+    }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", (data) => {
+            if (data.input.priority === "urgent") {
+                return { resolvedChannel: "sms" };
+            }
+            return undefined;
+        });
+
+        const result = await hooks.applyHooksAsync("notification:routing", {
+            input: makeInput({ priority: "urgent" }),
+            resolvedChannel: "email",
+            metadata: {},
+        });
+
+        expect(result.resolvedChannel).toBe("sms");
+    });
+
+    it("multiple handlers compose left-to-right", {
+        timeout: 5000,
+    }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        const order: string[] = [];
+
+        hooks.hook("notification:routing", (data) => {
+            order.push("first");
+            return { metadata: { ...data.metadata, step1: true } };
+        });
+        hooks.hook("notification:routing", (data) => {
+            order.push("second");
+            return { metadata: { ...data.metadata, step2: true } };
+        });
+
+        const result = await hooks.applyHooksAsync("notification:routing", {
+            input: makeInput(),
+            resolvedChannel: "email",
+            metadata: {},
+        });
+
+        expect(order).toEqual(["first", "second"]);
+        expect(result.metadata).toEqual({ step1: true, step2: true });
+    });
+
+    it("returns input unchanged when no handlers are registered", {
+        timeout: 5000,
+    }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        const input = {
+            input: makeInput(),
+            resolvedChannel: "email" as const,
+            metadata: { keep: 1 },
+        };
+        const result = await hooks.applyHooksAsync(
+            "notification:routing",
+            input
+        );
+        expect(result).toEqual(input);
+    });
+
+    it("handler returning void/undefined leaves data intact", {
+        timeout: 5000,
+    }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", () => {
+            // no-op handler
+        });
+        const result = await hooks.applyHooksAsync("notification:routing", {
+            input: makeInput(),
+            resolvedChannel: "email",
+            metadata: {},
+        });
+        expect(result.resolvedChannel).toBe("email");
+    });
+
+    it("hook handler may return an async partial override", {
+        timeout: 5000,
+    }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", async (data) => {
+            await Promise.resolve();
+            return { resolvedChannel: "push" } as Partial<
+                NotificationHookMap["notification:routing"]
+            >;
+        });
+        const result = await hooks.applyHooksAsync("notification:routing", {
+            input: makeInput(),
+            resolvedChannel: "email",
+            metadata: {},
+        });
+        expect(result.resolvedChannel).toBe("push");
+    });
+
+    it("unsubscribe removes the handler", { timeout: 5000 }, async () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        let invoked = false;
+        const off = hooks.hook("notification:routing", () => {
+            invoked = true;
+        });
+        off();
+        await hooks.applyHooksAsync("notification:routing", {
+            input: makeInput(),
+            resolvedChannel: "email",
+            metadata: {},
+        });
+        expect(invoked).toBe(false);
+    });
+
+    it("unsubscribe is safe after clear() drops the key entirely", {
+        timeout: 5000,
+    }, () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        const off = hooks.hook("notification:routing", () => undefined);
+        hooks.clear("notification:routing");
+        expect(() => off()).not.toThrow();
+    });
+
+    it("unsubscribe is a no-op for already-removed handlers", {
+        timeout: 5000,
+    }, () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        const off = hooks.hook("notification:routing", () => undefined);
+        off();
+        // Calling twice must not throw
+        off();
+        expect(hooks.count("notification:routing")).toBe(0);
+    });
+
+    it("clear(key) drops only that key", { timeout: 5000 }, () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", () => undefined);
+        hooks.hook("notification:routing", () => undefined);
+        expect(hooks.count("notification:routing")).toBe(2);
+        hooks.clear("notification:routing");
+        expect(hooks.count("notification:routing")).toBe(0);
+    });
+
+    it("clear() drops every key", { timeout: 5000 }, () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", () => undefined);
+        hooks.clear();
+        expect(hooks.count("notification:routing")).toBe(0);
+    });
+
+    it("hooks registered on one key do not interfere with another", {
+        timeout: 5000,
+    }, () => {
+        const hooks = new Hooks<NotificationHookMap>();
+        hooks.hook("notification:routing", () => undefined);
+        // The map only ships with one key today, so the cross-key check
+        // verifies clear() of an unknown key is safe and count returns 0.
+        hooks.clear();
+        expect(hooks.count("notification:routing")).toBe(0);
+    });
+});
+
+describe("onNotificationRouting (singleton)", () => {
+    it("registers against the package-level singleton", {
+        timeout: 5000,
+    }, async () => {
+        let observed = "";
+        const off = onNotificationRouting((data) => {
+            observed = data.resolvedChannel;
+        });
+        try {
+            await notificationHooks.applyHooksAsync("notification:routing", {
+                input: makeInput(),
+                resolvedChannel: "email",
+                metadata: {},
+            });
+            expect(observed).toBe("email");
+        } finally {
+            off();
+        }
+    });
+});

packages/communication/messaging/notification-channel/src/hooks/hooks.ts

@@ -0,0 +1,123 @@
+import type {
+    NotificationChannel,
+    NotificationInput,
+} from "../types/notification.types.js";
+
+/** Data flowing through the `notification:routing` hook pipeline. */
+export interface NotificationRoutingHookData {
+    /** The original notification input. */
+    readonly input: NotificationInput;
+    /** The resolved channel (may be overridden by hooks). */
+    readonly resolvedChannel: NotificationChannel;
+    /** Additional metadata for the routing pipeline. */
+    readonly metadata: Readonly<Record<string, unknown>>;
+}
+
+/** Hook map for notification hooks. */
+export interface NotificationHookMap {
+    "notification:routing": NotificationRoutingHookData;
+}
+
+/**
+ * Handler signature. Returning `undefined` means "no change"; returning
+ * a partial value merges over the current data and flows forward to the
+ * next handler.
+ */
+export type NotificationHookHandler<K extends keyof NotificationHookMap> = (
+    data: NotificationHookMap[K]
+) =>
+    | Partial<NotificationHookMap[K]>
+    | NotificationHookMap[K]
+    | undefined
+    | Promise<
+        Partial<NotificationHookMap[K]> | NotificationHookMap[K] | undefined
+    >;
+
+type AnyHandler = (
+    data: unknown
+) => unknown | undefined | Promise<unknown | undefined>;
+
+interface RegisteredHandler {
+    readonly fn: AnyHandler;
+}
+
+/**
+ * Generic typed hook bus. Handlers run in registration order; each handler
+ * may return a partial override merged into the data flowing to the next
+ * handler. The hook bus is intentionally local to this package — the
+ * genesis `@suaveplan/events` foundation does not currently export a
+ * `Hooks` primitive, and inlining keeps the package universal without
+ * an extra workspace dep.
+ */
+export class Hooks<TMap extends NotificationHookMap> {
+    private readonly handlers = new Map<keyof TMap, RegisteredHandler[]>();
+
+    /** Register a handler. Returns an unsubscribe function. */
+    public hook<K extends keyof TMap & keyof NotificationHookMap>(
+        key: K,
+        fn: NotificationHookHandler<K>
+    ): () => void {
+        const entry: RegisteredHandler = { fn: fn as AnyHandler };
+        const list = this.handlers.get(key);
+        if (list === undefined) {
+            this.handlers.set(key, [entry]);
+        } else {
+            list.push(entry);
+        }
+        return () => {
+            const cur = this.handlers.get(key);
+            if (cur === undefined) return;
+            const idx = cur.indexOf(entry);
+            if (idx !== -1) cur.splice(idx, 1);
+        };
+    }
+
+    /** Drop every handler for a key (or all keys when `key` omitted). */
+    public clear<K extends keyof TMap>(key?: K): void {
+        if (key === undefined) {
+            this.handlers.clear();
+            return;
+        }
+        this.handlers.delete(key);
+    }
+
+    /** Number of handlers registered for a key. */
+    public count<K extends keyof TMap>(key: K): number {
+        return this.handlers.get(key)?.length ?? 0;
+    }
+
+    /**
+     * Run every handler for `key` in registration order, threading the
+     * data forward. Returns the final composed data.
+     */
+    public async applyHooksAsync<
+        K extends keyof TMap & keyof NotificationHookMap,
+    >(key: K, data: NotificationHookMap[K]): Promise<NotificationHookMap[K]> {
+        const list = this.handlers.get(key);
+        if (list === undefined || list.length === 0) return data;
+        let current = data;
+        for (const entry of list.slice()) {
+            const partial = await entry.fn(current);
+            if (partial !== undefined && partial !== null) {
+                current = {
+                    ...current,
+                    ...(partial as Partial<NotificationHookMap[K]>),
+                } as NotificationHookMap[K];
+            }
+        }
+        return current;
+    }
+}
+
+/** Singleton hooks instance for the notification-channel package. */
+export const notificationHooks = new Hooks<NotificationHookMap>();
+
+/**
+ * Register a handler for the `notification:routing` hook. Shorthand for
+ * `notificationHooks.hook("notification:routing", handler)`.
+ */
+export function onNotificationRouting(
+    handler: NotificationHookHandler<"notification:routing">
+): () => void {
+    return notificationHooks.hook("notification:routing", handler);
+}

packages/communication/messaging/notification-channel/src/index.ts

@@ -0,0 +1,153 @@
+// Side-effect: registers the NOTIFICATION_CHANNEL_* error-code namespace so
+// subpath consumers also see the registered codes (rule: src/index.ts must
+// side-effect-import "./error-codes/index.js").
+import "./error-codes/index.js";
+
+export type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "./channels/delivery-channel.js";
+export {
+    EmailChannel,
+    type EmailChannelConfig,
+    type EmailMessage,
+} from "./channels/email-channel.js";
+export {
+    InAppChannel,
+    type InAppNotification,
+    type InAppStore,
+} from "./channels/in-app-channel.js";
+export { PushChannel } from "./channels/push-channel.js";
+export type {
+    PushAction,
+    PushChannelConfig,
+    PushPayload,
+    PushSendOutcome,
+    PushSubscription,
+    VapidKeys,
+} from "./channels/push-channel.types.js";
+export {
+    SmsChannel,
+    type SmsChannelConfig,
+    type SmsMessage,
+} from "./channels/sms-channel.js";
+export {
+    WebhookChannel,
+    type WebhookChannelConfig,
+} from "./channels/webhook-channel.js";
+export {
+    DigestChannel,
+    type DigestChannelConfig,
+} from "./digest/digest-channel.js";
+export {
+    ChannelDisabledError,
+    ChannelUnavailableError,
+    DeliveryFailedError,
+    DeliveryTimeoutError,
+    InvalidRecipientError,
+    NOTIFICATION_CHANNEL_CODES,
+    NotificationChannelError,
+    type NotificationChannelErrorCode,
+    NotificationNotFoundError,
+    ProviderErrorError,
+    RateLimitExceededError,
+    RateLimitedError,
+    RoutingFailedError,
+    TemplateNotFoundError,
+} from "./error-codes/index.js";
+export {
+    ERROR_CODE_TO_CTOR,
+    errorFromCode,
+    REASON_CODES,
+} from "./error-mapping/index.js";
+export {
+    FakeFetch,
+    type FakeFetchCall,
+    type FakeFetchResponse,
+} from "./fakes/fake-fetch.js";
+export {
+    Hooks,
+    type NotificationHookHandler,
+    type NotificationHookMap,
+    type NotificationRoutingHookData,
+    notificationHooks,
+    onNotificationRouting,
+} from "./hooks/hooks.js";
+export {
+    type RouterOutcome,
+    recordDeadLetter,
+    recordDeliveryAttempt,
+    recordRouted,
+    refreshNotificationMeters,
+} from "./otel/metrics.js";
+export {
+    PreferenceManager,
+    type PreferenceManagerOptions,
+    type PreferenceStoreAdapter,
+    type QuietHoursConfig,
+    type StoredPreferences,
+    type UserPreferences,
+} from "./preferences/preference-manager.js";
+export {
+    ChannelRateLimiter,
+    type RateLimitRule,
+} from "./rate-limiter/channel-rate-limiter.js";
+export {
+    type DeadLetterEntry,
+    type DeadLetterHandler,
+    DeliveryRetry,
+    type RetryConfig,
+    type SleepFn,
+} from "./retry/delivery-retry.js";
+export {
+    NotificationRouter,
+    type NotificationRouterConfig,
+} from "./router/notification-router.js";
+export {
+    NotificationScheduler,
+    type ScheduledNotification,
+    type ScheduleHandler,
+} from "./scheduler/notification-scheduler.js";
+export {
+    ChannelConfigSchema,
+    DigestChannelConfigSchema,
+    EmailChannelConfigSchema,
+    NotificationChannelSchema,
+    NotificationInputSchema,
+    NotificationPrioritySchema,
+    NotificationRouterConfigSchema,
+    NotificationStatusSchema,
+    NotificationTemplateSchema,
+    PreferenceManagerOptionsSchema,
+    PushChannelConfigSchema,
+    QuietHoursConfigSchema,
+    RateLimitRuleSchema,
+    RetryConfigSchema,
+    RoutingRuleSchema,
+    SmsChannelConfigSchema,
+    StoredPreferencesSchema,
+    TemplateRegistrationSchema,
+    VapidKeysSchema,
+    WebhookChannelConfigSchema,
+} from "./schemas/schemas.js";
+export {
+    type ChannelTemplate,
+    type ChannelTemplateBody,
+    type RenderedTemplate,
+    TemplateEngine,
+    type TemplateRegistration,
+} from "./templates/template-engine.js";
+export {
+    type ChannelConfig,
+    type ChannelRetryPolicy,
+    type Notification,
+    type NotificationChannel,
+    type NotificationEventMap,
+    type NotificationInput,
+    type NotificationPriority,
+    type NotificationResult,
+    type NotificationStatus,
+    type NotificationTemplate,
+    type RoutingRule,
+    VALID_TRANSITIONS,
+} from "./types/notification.types.js";

packages/communication/messaging/notification-channel/src/otel/metrics.md

@@ -0,0 +1,67 @@
+# `otel/metrics` — OpenTelemetry instrumentation
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`otel/metrics.ts` registers the package's four OpenTelemetry instruments on a meter named `@suaveplan/notification-channel` and exposes the recording helpers used by the router and retry wrapper. Tests rebind the instruments against an in-memory `MeterProvider` via `refreshNotificationMeters()` so emitted metrics can be inspected without spinning up a real OTel collector.
+
+## Features
+
+- `notification_channel.routed` (Counter) — one increment per `NotificationRouter.send` invocation, labelled `{ channel, outcome }`.
+- `notification_channel.delivery_attempts` (Counter) — one increment per dispatch to a registered `DeliveryChannel`.
+- `notification_channel.dead_letters` (Counter) — one increment when `DeliveryRetry` exhausts retries.
+- `notification_channel.latency_ms` (Histogram) — `NotificationRouter.send` end-to-end latency.
+- `refreshNotificationMeters()` — re-resolves every instrument against the global `MeterProvider`.
+
+## Usage: Basic
+
+```ts
+import { metrics } from "@opentelemetry/api";
+import { refreshNotificationMeters } from "@suaveplan/notification-channel/otel/metrics";
+
+// Wire a real MeterProvider somewhere in process bootstrap, then:
+metrics.setGlobalMeterProvider(provider);
+refreshNotificationMeters();
+
+// Router and retry calls automatically populate the instruments.
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    refreshNotificationMeters,
+    recordDeadLetter,
+    recordDeliveryAttempt,
+    recordRouted,
+} from "@suaveplan/notification-channel/otel/metrics";
+
+// Custom dispatcher that records attempts/dead-letters explicitly.
+async function dispatch(channel: string, send: () => Promise<void>) {
+    try {
+        await send();
+        recordDeliveryAttempt(channel, "ok");
+    } catch (err) {
+        recordDeliveryAttempt(channel, "failed");
+        recordDeadLetter(channel);
+        throw err;
+    }
+}
+
+refreshNotificationMeters();
+```
+
+## API Reference
+
+- `refreshNotificationMeters(): void` — rebind to the current global meter.
+- `recordRouted(channel, outcome, latencyMs)` — router send.
+- `recordDeliveryAttempt(channel, outcome)` — dispatch outcome.
+- `recordDeadLetter(channel)` — dead-letter event.
+- `RouterOutcome` — `"ok" | "failed"`.
+
+## Implementation Notes
+
+The instruments are module-level `let` bindings re-pointed by `refreshNotificationMeters` because `@opentelemetry/api` resolves the meter at the moment `getMeter` is called — if `metrics.setGlobalMeterProvider` runs AFTER the module first loads, the original meter is still bound to the no-op provider. `refreshNotificationMeters` solves that for tests and for any process that wires the OTel SDK after this module imports. The recording helpers are typed against `RouterOutcome` so consumers cannot accidentally pass an unknown outcome label.

packages/communication/messaging/notification-channel/src/otel/metrics.test.ts

@@ -0,0 +1,76 @@
+import { beforeAll, describe, expect, it } from "@suaveplan/testing/runner";
+import { flushTestMetrics } from "../../tests/setup/polyfills.js";
+import { NotificationRouter } from "../router/notification-router.js";
+import {
+    recordDeadLetter,
+    recordDeliveryAttempt,
+    recordRouted,
+    refreshNotificationMeters,
+} from "./metrics.js";
+
+beforeAll(() => {
+    // Rebind every instrument against the test MeterProvider configured
+    // in tests/setup/polyfills.ts.
+    refreshNotificationMeters();
+});
+
+describe("otel/metrics", () => {
+    it("router records routed counter on send", { timeout: 5000 }, async () => {
+        await flushTestMetrics();
+        const router = new NotificationRouter({
+            channels: [{ channel: "email", enabled: true }],
+            defaultChannel: "email",
+        });
+        await router.send({ recipient: "user@example.com", body: "Hi" });
+
+        const collected = await flushTestMetrics();
+        const flat = collected.flatMap((rm) =>
+            rm.scopeMetrics.flatMap((sm) => sm.metrics)
+        );
+        const routed = flat.find(
+            (m) => m.descriptor.name === "notification_channel.routed"
+        );
+        expect(routed).toBeDefined();
+        const total = routed?.dataPoints.reduce(
+            (sum, p) => sum + Number(p.value),
+            0
+        );
+        expect(total).toBeGreaterThanOrEqual(1);
+    });
+
+    it("router records latency histogram on send", {
+        timeout: 5000,
+    }, async () => {
+        await flushTestMetrics();
+        const router = new NotificationRouter({
+            channels: [{ channel: "email", enabled: true }],
+            defaultChannel: "email",
+        });
+        await router.send({ recipient: "user@example.com", body: "Hi" });
+
+        const collected = await flushTestMetrics();
+        const flat = collected.flatMap((rm) =>
+            rm.scopeMetrics.flatMap((sm) => sm.metrics)
+        );
+        const latency = flat.find(
+            (m) => m.descriptor.name === "notification_channel.latency_ms"
+        );
+        expect(latency).toBeDefined();
+    });
+
+    it("recordDeliveryAttempt and recordDeadLetter increment their counters", {
+        timeout: 5000,
+    }, async () => {
+        await flushTestMetrics();
+        recordRouted("email", "ok", 12);
+        recordDeliveryAttempt("email", "ok");
+        recordDeadLetter("email");
+        const collected = await flushTestMetrics();
+        const names = collected
+            .flatMap((rm) => rm.scopeMetrics.flatMap((sm) => sm.metrics))
+            .map((m) => m.descriptor.name);
+        expect(names).toContain("notification_channel.routed");
+        expect(names).toContain("notification_channel.delivery_attempts");
+        expect(names).toContain("notification_channel.dead_letters");
+    });
+});

packages/communication/messaging/notification-channel/src/otel/metrics.ts

@@ -0,0 +1,95 @@
+import type { Counter, Histogram, Meter } from "@opentelemetry/api";
+import { metrics } from "@opentelemetry/api";
+
+const METER_NAME = "@suaveplan/notification-channel";
+const METER_VERSION = "0.1.0";
+
+/** Outcome label on every router-emitted instrument. */
+export type RouterOutcome = "ok" | "failed";
+
+let meter: Meter = metrics.getMeter(METER_NAME, METER_VERSION);
+
+let routedCounter: Counter = meter.createCounter(
+    "notification_channel.routed",
+    {
+        description:
+            "Count of router send() invocations by channel and outcome",
+    }
+);
+
+let deliveryAttemptCounter: Counter = meter.createCounter(
+    "notification_channel.delivery_attempts",
+    {
+        description:
+            "Count of delivery attempts dispatched to a registered DeliveryChannel",
+    }
+);
+
+let deadLetterCounter: Counter = meter.createCounter(
+    "notification_channel.dead_letters",
+    {
+        description: "Count of notifications that exhausted retries",
+    }
+);
+
+let latencyHistogram: Histogram = meter.createHistogram(
+    "notification_channel.latency_ms",
+    {
+        description: "Router send() latency in milliseconds",
+        unit: "ms",
+    }
+);
+
+/**
+ * Re-resolve every instrument against the current global
+ * `MeterProvider`. Tests call this after wiring an in-memory exporter
+ * so subsequent record calls land on the test provider rather than the
+ * module-load meter.
+ */
+export function refreshNotificationMeters(): void {
+    meter = metrics.getMeter(METER_NAME, METER_VERSION);
+    routedCounter = meter.createCounter("notification_channel.routed", {
+        description:
+            "Count of router send() invocations by channel and outcome",
+    });
+    deliveryAttemptCounter = meter.createCounter(
+        "notification_channel.delivery_attempts",
+        {
+            description:
+                "Count of delivery attempts dispatched to a registered DeliveryChannel",
+        }
+    );
+    deadLetterCounter = meter.createCounter(
+        "notification_channel.dead_letters",
+        {
+            description: "Count of notifications that exhausted retries",
+        }
+    );
+    latencyHistogram = meter.createHistogram(
+        "notification_channel.latency_ms",
+        {
+            description: "Router send() latency in milliseconds",
+            unit: "ms",
+        }
+    );
+}
+
+export function recordRouted(
+    channel: string,
+    outcome: RouterOutcome,
+    latencyMs: number
+): void {
+    routedCounter.add(1, { channel, outcome });
+    latencyHistogram.record(latencyMs, { channel, outcome });
+}
+
+export function recordDeliveryAttempt(
+    channel: string,
+    outcome: RouterOutcome
+): void {
+    deliveryAttemptCounter.add(1, { channel, outcome });
+}
+
+export function recordDeadLetter(channel: string): void {
+    deadLetterCounter.add(1, { channel });
+}

packages/communication/messaging/notification-channel/src/preferences/preference-manager.md

@@ -0,0 +1,74 @@
+# `preference-manager` — Per-user opt-in / opt-out + quiet hours
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`preference-manager.ts` ships the `PreferenceManager` class that answers, at every send-time, "should this notification reach this user on this channel right now?". The manager combines per-channel opt-in / opt-out preferences with optional quiet-hours configuration (with priority thresholds) and a pluggable `PreferenceStoreAdapter` for persistence.
+
+## Features
+
+- Per-user channel enable / disable, with explicit `enabledChannels` and `disabledChannels` sets.
+- Default channels (configurable; built-in default: `["email", "in_app"]`).
+- Quiet-hours config with `startHour`, `endHour` (wrap-around supported), and optional `days` filter.
+- `urgentThreshold` controls which priorities punch through quiet hours (default `urgent`).
+- `canDeliver(userId, channel, priority)` is the single decision point.
+- Pluggable `PreferenceStoreAdapter` so persistence is delegated to SurrealDB, Postgres, Redis, etc.
+- Injectable `Clock` for deterministic tests.
+
+## Usage: Basic
+
+```ts
+import {
+    PreferenceManager,
+    type PreferenceStoreAdapter,
+} from "@suaveplan/notification-channel";
+
+const store: PreferenceStoreAdapter = makeStore();
+const manager = new PreferenceManager({ store });
+
+if (await manager.canDeliver("user-1", "email", "normal")) {
+    await router.send(...);
+}
+```
+
+## Usage: Advanced
+
+```ts
+const manager = new PreferenceManager({
+    store,
+    defaultChannels: ["email", "push", "in_app"],
+    clock: () => Date.now(),
+});
+
+await manager.setEnabled("user-1", "sms", true);
+await manager.setQuietHours("user-1", {
+    startHour: 22,
+    endHour: 7,
+    days: [1, 2, 3, 4, 5], // weekdays
+});
+
+// At dispatch time:
+for (const channel of selected) {
+    if (await manager.canDeliver("user-1", channel, "high")) {
+        await router.send({ recipient: "user-1", body: text, channel });
+    }
+}
+```
+
+## API Reference
+
+- `PreferenceManager(options: PreferenceManagerOptions)` — constructor.
+- `PreferenceManagerOptions` — `{ store, defaultChannels?, clock? }`.
+- `canDeliver(userId, channel, priority): Promise<boolean>`.
+- `getPreferences(userId): Promise<UserPreferences>`.
+- `setEnabled(userId, channel, enabled): Promise<void>`.
+- `setQuietHours(userId, quietHours | null): Promise<void>`.
+- `resetPreferences(userId): Promise<boolean>`.
+- `PreferenceStoreAdapter`, `UserPreferences`, `StoredPreferences`, `QuietHoursConfig`.
+
+## Implementation Notes
+
+Quiet-hours wrap around midnight when `startHour > endHour` (e.g. `22 → 7`). Priorities are ordered `low < normal < high < urgent`; if `urgentThreshold` is `"high"`, then both `high` and `urgent` punch through quiet hours. The day filter is opt-in — when omitted, quiet hours apply every day; when supplied, only the listed days (`0` = Sunday) trigger the window. `setQuietHours(userId, null)` clears the field; existing `enabledChannels`/`disabledChannels`/`urgentThreshold` are preserved. The store adapter is the single integration seam — the rest of the class is purely functional logic, so swapping persistence layers does not change behaviour.

packages/communication/messaging/notification-channel/src/preferences/preference-manager.test.ts

@@ -0,0 +1,419 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    PreferenceManager,
+    type PreferenceStoreAdapter,
+    type StoredPreferences,
+} from "./preference-manager.js";
+
+function makeMemoryStore(): PreferenceStoreAdapter & {
+    data: Map<string, StoredPreferences>;
+} {
+    const data = new Map<string, StoredPreferences>();
+    return {
+        data,
+        get: async (userId) => data.get(userId) ?? null,
+        set: async (userId, prefs) => {
+            data.set(userId, prefs);
+        },
+        delete: async (userId) => data.delete(userId) || false,
+    };
+}
+
+describe("PreferenceManager", () => {
+    describe("getPreferences", () => {
+        it("returns defaults when no preferences stored", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            const prefs = await manager.getPreferences("user-1");
+
+            expect(prefs.userId).toBe("user-1");
+            expect(prefs.enabledChannels.has("email")).toBe(true);
+            expect(prefs.enabledChannels.has("in_app")).toBe(true);
+            expect(prefs.disabledChannels.size).toBe(0);
+        });
+
+        it("uses custom default channels", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({
+                store,
+                defaultChannels: ["push", "sms"],
+            });
+
+            const prefs = await manager.getPreferences("user-1");
+
+            expect(prefs.enabledChannels.has("push")).toBe(true);
+            expect(prefs.enabledChannels.has("sms")).toBe(true);
+            expect(prefs.enabledChannels.has("email")).toBe(false);
+        });
+
+        it("returns stored preferences when they exist", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            store.data.set("user-1", {
+                userId: "user-1",
+                enabledChannels: ["email", "push"],
+                disabledChannels: ["sms"],
+                urgentThreshold: "high",
+            });
+            const manager = new PreferenceManager({ store });
+
+            const prefs = await manager.getPreferences("user-1");
+
+            expect(prefs.enabledChannels.has("email")).toBe(true);
+            expect(prefs.enabledChannels.has("push")).toBe(true);
+            expect(prefs.disabledChannels.has("sms")).toBe(true);
+            expect(prefs.urgentThreshold).toBe("high");
+        });
+
+        it("returns stored quiet-hours when present", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            store.data.set("user-1", {
+                userId: "user-1",
+                enabledChannels: ["email"],
+                disabledChannels: [],
+                quietHours: { startHour: 22, endHour: 7 },
+            });
+            const manager = new PreferenceManager({ store });
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.quietHours).toEqual({ startHour: 22, endHour: 7 });
+        });
+    });
+
+    describe("setEnabled", () => {
+        it("enables a channel for a user", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setEnabled("user-1", "push", true);
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.enabledChannels.has("push")).toBe(true);
+            expect(prefs.disabledChannels.has("push")).toBe(false);
+        });
+
+        it("disables a channel for a user", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setEnabled("user-1", "email", false);
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.enabledChannels.has("email")).toBe(false);
+            expect(prefs.disabledChannels.has("email")).toBe(true);
+        });
+
+        it("moves channel from disabled to enabled", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setEnabled("user-1", "sms", false);
+            await manager.setEnabled("user-1", "sms", true);
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.enabledChannels.has("sms")).toBe(true);
+            expect(prefs.disabledChannels.has("sms")).toBe(false);
+        });
+    });
+
+    describe("setQuietHours", () => {
+        it("sets quiet hours for a user", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 22,
+                endHour: 7,
+            });
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.quietHours).toEqual({ startHour: 22, endHour: 7 });
+        });
+
+        it("clears quiet hours when set to null", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 22,
+                endHour: 7,
+            });
+            await manager.setQuietHours("user-1", null);
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.quietHours).toBeUndefined();
+        });
+
+        it("sets quiet hours with specific days", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 23,
+                endHour: 6,
+                days: [1, 2, 3, 4, 5],
+            });
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.quietHours?.days).toEqual([1, 2, 3, 4, 5]);
+        });
+
+        it("preserves urgentThreshold when setting quiet hours", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            store.data.set("user-1", {
+                userId: "user-1",
+                enabledChannels: ["email"],
+                disabledChannels: [],
+                urgentThreshold: "high",
+            });
+            const manager = new PreferenceManager({ store });
+            await manager.setQuietHours("user-1", {
+                startHour: 1,
+                endHour: 2,
+            });
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.urgentThreshold).toBe("high");
+        });
+    });
+
+    describe("canDeliver", () => {
+        it("allows delivery on enabled channel", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            const can = await manager.canDeliver("user-1", "email", "normal");
+            expect(can).toBe(true);
+        });
+
+        it("blocks delivery on disabled channel", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setEnabled("user-1", "email", false);
+
+            const can = await manager.canDeliver("user-1", "email", "normal");
+            expect(can).toBe(false);
+        });
+
+        it("blocks delivery on non-default non-enabled channel", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            const can = await manager.canDeliver("user-1", "push", "normal");
+            expect(can).toBe(false);
+        });
+
+        it("allows delivery on default channel without explicit enable", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({
+                store,
+                defaultChannels: ["email", "push"],
+            });
+
+            const can = await manager.canDeliver("user-1", "push", "normal");
+            expect(can).toBe(true);
+        });
+
+        it("blocks low priority during quiet hours", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            // Pin the clock at noon UTC so the quiet-hours window is
+            // deterministic regardless of when CI runs.
+            const noonUtc = Date.UTC(2026, 0, 1, 12, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noonUtc,
+            });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 12,
+                endHour: 14,
+            });
+
+            const can = await manager.canDeliver("user-1", "email", "low");
+            expect(can).toBe(false);
+        });
+
+        it("allows urgent during quiet hours", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const noonUtc = Date.UTC(2026, 0, 1, 12, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noonUtc,
+            });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 12,
+                endHour: 14,
+            });
+
+            const can = await manager.canDeliver("user-1", "email", "urgent");
+            expect(can).toBe(true);
+        });
+
+        it("allows normal priority outside quiet hours", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const noonUtc = Date.UTC(2026, 0, 1, 12, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noonUtc,
+            });
+
+            await manager.setQuietHours("user-1", {
+                startHour: 16,
+                endHour: 18,
+            });
+
+            const can = await manager.canDeliver("user-1", "email", "normal");
+            expect(can).toBe(true);
+        });
+
+        it("respects custom urgentThreshold", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const noonUtc = Date.UTC(2026, 0, 1, 12, 0, 0);
+
+            store.data.set("user-1", {
+                userId: "user-1",
+                enabledChannels: ["email", "in_app"],
+                disabledChannels: [],
+                quietHours: { startHour: 12, endHour: 14 },
+                urgentThreshold: "high",
+            });
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noonUtc,
+            });
+
+            const canHigh = await manager.canDeliver("user-1", "email", "high");
+            expect(canHigh).toBe(true);
+
+            const canNormal = await manager.canDeliver(
+                "user-1",
+                "email",
+                "normal"
+            );
+            expect(canNormal).toBe(false);
+        });
+
+        it("respects quiet-hours day filter (today excluded)", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            // 2026-01-01 is a Thursday (day 4); set quiet-hours for days
+            // [1,2] (Mon, Tue) so today is excluded.
+            const noonThu = Date.UTC(2026, 0, 1, 12, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noonThu,
+            });
+            await manager.setQuietHours("user-1", {
+                startHour: 12,
+                endHour: 14,
+                days: [1, 2],
+            });
+
+            const can = await manager.canDeliver("user-1", "email", "low");
+            expect(can).toBe(true);
+        });
+
+        it("handles wrap-around quiet hours (22→7)", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const elevenPm = Date.UTC(2026, 0, 1, 23, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => elevenPm,
+            });
+            await manager.setQuietHours("user-1", {
+                startHour: 22,
+                endHour: 7,
+            });
+            const can = await manager.canDeliver("user-1", "email", "low");
+            expect(can).toBe(false);
+        });
+
+        it("normal priority hour outside wrap-around window", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const noon = Date.UTC(2026, 0, 1, 12, 0, 0);
+            const manager = new PreferenceManager({
+                store,
+                clock: () => noon,
+            });
+            await manager.setQuietHours("user-1", {
+                startHour: 22,
+                endHour: 7,
+            });
+            const can = await manager.canDeliver("user-1", "email", "low");
+            expect(can).toBe(true);
+        });
+    });
+
+    describe("default clock", () => {
+        it("uses the built-in clock when none injected", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+            // Set quiet-hours so canDeliver invokes isQuietHours and
+            // exercises the default Clock thunk.
+            await manager.setQuietHours("user-1", {
+                startHour: 0,
+                endHour: 24 - 1,
+            });
+            // Assertion shape only — wall-clock dependent boolean.
+            const can = await manager.canDeliver("user-1", "email", "normal");
+            expect(typeof can).toBe("boolean");
+        });
+    });
+
+    describe("resetPreferences", () => {
+        it("deletes stored preferences", { timeout: 5000 }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+
+            await manager.setEnabled("user-1", "sms", true);
+            await manager.resetPreferences("user-1");
+
+            const prefs = await manager.getPreferences("user-1");
+            expect(prefs.enabledChannels.has("email")).toBe(true);
+            expect(prefs.enabledChannels.has("in_app")).toBe(true);
+            expect(prefs.enabledChannels.has("sms")).toBe(false);
+        });
+
+        it("returns false when nothing to delete", {
+            timeout: 5000,
+        }, async () => {
+            const store = makeMemoryStore();
+            const manager = new PreferenceManager({ store });
+            const ok = await manager.resetPreferences("ghost");
+            expect(ok).toBe(false);
+        });
+    });
+});

packages/communication/messaging/notification-channel/src/preferences/preference-manager.ts

@@ -0,0 +1,205 @@
+import type { Clock } from "@suaveplan/types";
+import type {
+    NotificationChannel,
+    NotificationPriority,
+} from "../types/notification.types.js";
+
+/** Quiet-hours configuration. */
+export interface QuietHoursConfig {
+    /** Start hour (0-23 UTC). */
+    readonly startHour: number;
+    /** End hour (0-23 UTC). */
+    readonly endHour: number;
+    /** Days of week to apply (0=Sun, 6=Sat). Default: all days. */
+    readonly days?: readonly number[];
+}
+
+/** Resolved user preferences. */
+export interface UserPreferences {
+    readonly userId: string;
+    readonly enabledChannels: ReadonlySet<NotificationChannel>;
+    readonly disabledChannels: ReadonlySet<NotificationChannel>;
+    readonly quietHours?: QuietHoursConfig;
+    readonly urgentThreshold?: NotificationPriority;
+}
+
+/** Serialised form of user preferences. */
+export interface StoredPreferences {
+    userId: string;
+    enabledChannels: NotificationChannel[];
+    disabledChannels: NotificationChannel[];
+    quietHours?: QuietHoursConfig;
+    urgentThreshold?: NotificationPriority;
+}
+
+/** Storage adapter for user preferences. */
+export interface PreferenceStoreAdapter {
+    get(userId: string): Promise<StoredPreferences | null>;
+    set(userId: string, prefs: StoredPreferences): Promise<void>;
+    delete(userId: string): Promise<boolean>;
+}
+
+/** Constructor options for `PreferenceManager`. */
+export interface PreferenceManagerOptions {
+    readonly store: PreferenceStoreAdapter;
+    readonly defaultChannels?: readonly NotificationChannel[];
+    readonly clock?: Clock;
+}
+
+const PRIORITY_ORDER: Readonly<Record<NotificationPriority, number>> = {
+    low: 0,
+    normal: 1,
+    high: 2,
+    urgent: 3,
+};
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Manages per-user notification preferences with opt-in / opt-out and
+ * quiet-hours support. Implements the decision at every send-time:
+ * "should this notification reach this user on this channel right
+ * now?". Storage is pluggable via `PreferenceStoreAdapter`.
+ */
+export class PreferenceManager {
+    private readonly store: PreferenceStoreAdapter;
+    private readonly defaults: ReadonlySet<NotificationChannel>;
+    private readonly clock: Clock;
+
+    public constructor(options: PreferenceManagerOptions) {
+        this.store = options.store;
+        this.defaults = new Set(options.defaultChannels ?? ["email", "in_app"]);
+        this.clock = options.clock ?? defaultClock;
+    }
+
+    /** Decide whether a notification may reach the user on this channel. */
+    public async canDeliver(
+        userId: string,
+        channel: NotificationChannel,
+        priority: NotificationPriority
+    ): Promise<boolean> {
+        const prefs = await this.getPreferences(userId);
+
+        if (prefs.disabledChannels.has(channel)) return false;
+        if (
+            !prefs.enabledChannels.has(channel) &&
+            !this.defaults.has(channel)
+        ) {
+            return false;
+        }
+
+        if (
+            prefs.quietHours !== undefined &&
+            this.isQuietHours(prefs.quietHours)
+        ) {
+            const threshold = prefs.urgentThreshold ?? "urgent";
+            if (PRIORITY_ORDER[priority] < PRIORITY_ORDER[threshold]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    /** Get user preferences (returns defaults if none stored). */
+    public async getPreferences(userId: string): Promise<UserPreferences> {
+        const stored = await this.store.get(userId);
+        if (stored === null) {
+            return {
+                userId,
+                enabledChannels: new Set(this.defaults),
+                disabledChannels: new Set(),
+            };
+        }
+        const result: {
+            -readonly [K in keyof UserPreferences]: UserPreferences[K];
+        } = {
+            userId: stored.userId,
+            enabledChannels: new Set(stored.enabledChannels),
+            disabledChannels: new Set(stored.disabledChannels),
+        };
+        if (stored.quietHours !== undefined) {
+            result.quietHours = stored.quietHours;
+        }
+        if (stored.urgentThreshold !== undefined) {
+            result.urgentThreshold = stored.urgentThreshold;
+        }
+        return result;
+    }
+
+    /** Enable or disable a channel for a user. */
+    public async setEnabled(
+        userId: string,
+        channel: NotificationChannel,
+        enabled: boolean
+    ): Promise<void> {
+        const stored = await this.store.get(userId);
+        const current: StoredPreferences = stored ?? {
+            userId,
+            enabledChannels: [...this.defaults],
+            disabledChannels: [],
+        };
+
+        const enabledSet = new Set(current.enabledChannels);
+        const disabledSet = new Set(current.disabledChannels);
+
+        if (enabled) {
+            enabledSet.add(channel);
+            disabledSet.delete(channel);
+        } else {
+            enabledSet.delete(channel);
+            disabledSet.add(channel);
+        }
+
+        await this.store.set(userId, {
+            ...current,
+            enabledChannels: [...enabledSet],
+            disabledChannels: [...disabledSet],
+        });
+    }
+
+    /** Set or clear quiet-hours for a user. */
+    public async setQuietHours(
+        userId: string,
+        quietHours: QuietHoursConfig | null
+    ): Promise<void> {
+        const stored = await this.store.get(userId);
+        const current: StoredPreferences = stored ?? {
+            userId,
+            enabledChannels: [...this.defaults],
+            disabledChannels: [],
+        };
+        const next: StoredPreferences = {
+            userId: current.userId,
+            enabledChannels: current.enabledChannels,
+            disabledChannels: current.disabledChannels,
+        };
+        if (current.urgentThreshold !== undefined) {
+            next.urgentThreshold = current.urgentThreshold;
+        }
+        if (quietHours !== null) {
+            next.quietHours = quietHours;
+        }
+        await this.store.set(userId, next);
+    }
+
+    /** Delete all preferences for a user (resets to defaults). */
+    public async resetPreferences(userId: string): Promise<boolean> {
+        return this.store.delete(userId);
+    }
+
+    private isQuietHours(config: QuietHoursConfig): boolean {
+        const now = new Date(this.clock());
+        const hour = now.getUTCHours();
+        const day = now.getUTCDay();
+
+        if (config.days !== undefined && !config.days.includes(day)) {
+            return false;
+        }
+
+        if (config.startHour <= config.endHour) {
+            return hour >= config.startHour && hour < config.endHour;
+        }
+        return hour >= config.startHour || hour < config.endHour;
+    }
+}

packages/communication/messaging/notification-channel/src/rate-limiter/channel-rate-limiter.md

@@ -0,0 +1,63 @@
+# `channel-rate-limiter` — Sliding-window rate limits
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`channel-rate-limiter.ts` ships the `ChannelRateLimiter` class — a per-channel + per-user sliding-window rate limiter. Two independent buckets are maintained: a per-channel bucket (every send against that channel counts) and a per-user bucket (every send for that user counts regardless of channel). `checkAndRecord(channel, userId)` consults both, throws `RateLimitExceededError` on overflow, otherwise records the send and returns.
+
+## Features
+
+- Per-channel and per-user limits with independent `{ maxCount, windowMs }` rules.
+- Sliding window — entries older than `windowMs` are discarded on every check.
+- `isAllowed` probe — non-recording check for UX-level pre-flight.
+- `getChannelRemaining` / `getUserRemaining` for headers like `X-RateLimit-Remaining`.
+- Injectable `Clock` so tests advance time without sleeping.
+- Universal — no Node/DOM-specific APIs.
+
+## Usage: Basic
+
+```ts
+import { ChannelRateLimiter } from "@suaveplan/notification-channel";
+
+const limiter = new ChannelRateLimiter();
+limiter.setChannelLimit("email", { maxCount: 100, windowMs: 60_000 });
+limiter.setUserLimit("user-42", { maxCount: 5, windowMs: 60_000 });
+
+try {
+    limiter.checkAndRecord("email", "user-42");
+} catch (err) {
+    /* RateLimitExceededError */
+}
+```
+
+## Usage: Advanced
+
+```ts
+const limiter = new ChannelRateLimiter(() => clock.now());
+limiter.setChannelLimit("sms", { maxCount: 10, windowMs: 60_000 });
+
+// Pre-flight without recording:
+if (!limiter.isAllowed("sms", userId)) {
+    return reply.code(429).send({
+        remaining: limiter.getChannelRemaining("sms"),
+    });
+}
+limiter.checkAndRecord("sms", userId);
+```
+
+## API Reference
+
+- `ChannelRateLimiter(clock?: Clock)` — constructor.
+- `setChannelLimit(channel, rule)`, `setUserLimit(userId, rule)` — install rules.
+- `removeChannelLimit(channel)`, `removeUserLimit(userId)` — drop rules and their windows.
+- `checkAndRecord(channel, userId)` — throws on overflow.
+- `isAllowed(channel, userId)` — boolean probe.
+- `getChannelRemaining(channel)`, `getUserRemaining(userId)` — current capacity (or `Infinity` when no rule).
+- `RateLimitRule` — `{ maxCount, windowMs }`.
+
+## Implementation Notes
+
+The window is sliding, not fixed — entries are filtered against `now - timestamp < windowMs` on every check. This is more accurate than fixed buckets at the cost of `O(n)` filtering on every check where `n` is the number of entries in the window; for buckets with `maxCount` in the low hundreds this is negligible. `recordChannel` / `recordUser` are no-ops when no rule is installed, so the `WindowEntry` arrays stay empty when the bucket has no limit. The injected `Clock` only governs the limiter's view of "now" — wall-clock drift between server and limiter does not exist because the limiter never compares its timestamps to anything external.

packages/communication/messaging/notification-channel/src/rate-limiter/channel-rate-limiter.test.ts

@@ -0,0 +1,158 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import { ChannelRateLimiter } from "./channel-rate-limiter.js";
+
+describe("ChannelRateLimiter", () => {
+    describe("channel limits", () => {
+        it("allows sends within limit", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 3, windowMs: 60_000 });
+            expect(() =>
+                limiter.checkAndRecord("email", "user1")
+            ).not.toThrow();
+            expect(() =>
+                limiter.checkAndRecord("email", "user2")
+            ).not.toThrow();
+            expect(() =>
+                limiter.checkAndRecord("email", "user3")
+            ).not.toThrow();
+        });
+
+        it("throws when channel limit exceeded", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 2, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            limiter.checkAndRecord("email", "user2");
+            expect(() => limiter.checkAndRecord("email", "user3")).toThrow(
+                NotificationChannelError
+            );
+        });
+
+        it("allows sends after window expires", { timeout: 5000 }, () => {
+            let now = 1_000_000;
+            const limiter = new ChannelRateLimiter(() => now);
+            limiter.setChannelLimit("email", { maxCount: 1, windowMs: 1_000 });
+            limiter.checkAndRecord("email", "user1");
+            now += 1_001;
+            expect(() =>
+                limiter.checkAndRecord("email", "user2")
+            ).not.toThrow();
+        });
+
+        it("does not limit when no limit set", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            for (let i = 0; i < 100; i++) {
+                expect(() =>
+                    limiter.checkAndRecord("email", `user${i}`)
+                ).not.toThrow();
+            }
+        });
+
+        it("removes channel limit", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            limiter.removeChannelLimit("email");
+            expect(() =>
+                limiter.checkAndRecord("email", "user2")
+            ).not.toThrow();
+        });
+    });
+
+    describe("user limits", () => {
+        it("allows sends within user limit", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setUserLimit("user1", { maxCount: 2, windowMs: 60_000 });
+            expect(() =>
+                limiter.checkAndRecord("email", "user1")
+            ).not.toThrow();
+            expect(() => limiter.checkAndRecord("sms", "user1")).not.toThrow();
+        });
+
+        it("throws when user limit exceeded", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setUserLimit("user1", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            expect(() => limiter.checkAndRecord("sms", "user1")).toThrow(
+                NotificationChannelError
+            );
+        });
+
+        it("removes user limit", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setUserLimit("user1", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            limiter.removeUserLimit("user1");
+            expect(() =>
+                limiter.checkAndRecord("email", "user1")
+            ).not.toThrow();
+        });
+    });
+
+    describe("isAllowed", () => {
+        it("returns true when within limits", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 5, windowMs: 60_000 });
+            expect(limiter.isAllowed("email", "user1")).toBe(true);
+        });
+
+        it("returns false when channel limit reached", {
+            timeout: 5000,
+        }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            expect(limiter.isAllowed("email", "user2")).toBe(false);
+        });
+
+        it("returns false when user limit reached", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setUserLimit("user1", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            expect(limiter.isAllowed("sms", "user1")).toBe(false);
+        });
+
+        it("returns true for an unconfigured user", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            expect(limiter.isAllowed("email", "user-without-limit")).toBe(true);
+        });
+    });
+
+    describe("remaining capacity", () => {
+        it("returns remaining channel capacity", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 5, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            limiter.checkAndRecord("email", "user2");
+            expect(limiter.getChannelRemaining("email")).toBe(3);
+        });
+
+        it("returns Infinity when no limit set", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            expect(limiter.getChannelRemaining("email")).toBe(
+                Number.POSITIVE_INFINITY
+            );
+        });
+
+        it("returns remaining user capacity", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setUserLimit("user1", { maxCount: 3, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            expect(limiter.getUserRemaining("user1")).toBe(2);
+        });
+
+        it("returns Infinity for user without limit", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            expect(limiter.getUserRemaining("user1")).toBe(
+                Number.POSITIVE_INFINITY
+            );
+        });
+
+        it("returns zero when capacity exhausted", { timeout: 5000 }, () => {
+            const limiter = new ChannelRateLimiter();
+            limiter.setChannelLimit("email", { maxCount: 1, windowMs: 60_000 });
+            limiter.checkAndRecord("email", "user1");
+            expect(limiter.getChannelRemaining("email")).toBe(0);
+        });
+    });
+});

packages/communication/messaging/notification-channel/src/rate-limiter/channel-rate-limiter.ts

@@ -0,0 +1,203 @@
+import type { Clock } from "@suaveplan/types";
+import { RateLimitExceededError } from "../error-codes/error-codes.js";
+import type { NotificationChannel } from "../types/notification.types.js";
+
+/** Configuration for a rate-limit rule. */
+export interface RateLimitRule {
+    /** Maximum number of notifications allowed in the window. */
+    readonly maxCount: number;
+    /** Window size in milliseconds. */
+    readonly windowMs: number;
+}
+
+interface WindowEntry {
+    readonly timestamp: number;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Sliding-window rate limiter for notification channels. Supports
+ * per-channel limits (every send against that channel counts toward
+ * the channel's bucket) and per-user limits (every send for that user
+ * counts toward the user's bucket, regardless of channel). Both
+ * buckets accept an injectable `Clock` so tests can advance time
+ * without sleeping.
+ */
+export class ChannelRateLimiter {
+    private readonly channelLimits = new Map<
+        NotificationChannel,
+        RateLimitRule
+    >();
+    private readonly userLimits = new Map<string, RateLimitRule>();
+    private readonly channelWindows = new Map<
+        NotificationChannel,
+        WindowEntry[]
+    >();
+    private readonly userWindows = new Map<string, WindowEntry[]>();
+    private readonly clock: Clock;
+
+    public constructor(clock: Clock = defaultClock) {
+        this.clock = clock;
+    }
+
+    /** Set a rate limit for a specific channel. */
+    public setChannelLimit(
+        channel: NotificationChannel,
+        rule: RateLimitRule
+    ): void {
+        this.channelLimits.set(channel, rule);
+    }
+
+    /** Set a rate limit for a specific user. */
+    public setUserLimit(userId: string, rule: RateLimitRule): void {
+        this.userLimits.set(userId, rule);
+    }
+
+    /** Remove a channel rate limit. */
+    public removeChannelLimit(channel: NotificationChannel): void {
+        this.channelLimits.delete(channel);
+        this.channelWindows.delete(channel);
+    }
+
+    /** Remove a user rate limit. */
+    public removeUserLimit(userId: string): void {
+        this.userLimits.delete(userId);
+        this.userWindows.delete(userId);
+    }
+
+    /**
+     * Check + record a send attempt against both buckets. Throws
+     * `RateLimitExceededError` when either bucket would overflow.
+     */
+    public checkAndRecord(channel: NotificationChannel, userId: string): void {
+        const now = this.clock();
+        this.checkChannelLimit(channel, now);
+        this.checkUserLimit(channel, userId, now);
+        this.recordChannel(channel, now);
+        this.recordUser(userId, now);
+    }
+
+    /** Probe whether `checkAndRecord` would succeed (does not record). */
+    public isAllowed(channel: NotificationChannel, userId: string): boolean {
+        const now = this.clock();
+        return (
+            this.isChannelAllowed(channel, now) &&
+            this.isUserAllowed(userId, now)
+        );
+    }
+
+    /** Remaining capacity in the channel bucket. */
+    public getChannelRemaining(channel: NotificationChannel): number {
+        const rule = this.channelLimits.get(channel);
+        if (rule === undefined) return Number.POSITIVE_INFINITY;
+
+        const now = this.clock();
+        const entries = this.getValidEntries(
+            this.channelWindows.get(channel),
+            now,
+            rule.windowMs
+        );
+        return Math.max(0, rule.maxCount - entries.length);
+    }
+
+    /** Remaining capacity in the user bucket. */
+    public getUserRemaining(userId: string): number {
+        const rule = this.userLimits.get(userId);
+        if (rule === undefined) return Number.POSITIVE_INFINITY;
+
+        const now = this.clock();
+        const entries = this.getValidEntries(
+            this.userWindows.get(userId),
+            now,
+            rule.windowMs
+        );
+        return Math.max(0, rule.maxCount - entries.length);
+    }
+
+    private checkChannelLimit(channel: NotificationChannel, now: number): void {
+        const rule = this.channelLimits.get(channel);
+        if (rule === undefined) return;
+
+        const entries = this.getValidEntries(
+            this.channelWindows.get(channel),
+            now,
+            rule.windowMs
+        );
+        if (entries.length >= rule.maxCount) {
+            throw new RateLimitExceededError({
+                context: { channel, scope: "channel" },
+            });
+        }
+    }
+
+    private checkUserLimit(
+        channel: NotificationChannel,
+        userId: string,
+        now: number
+    ): void {
+        const rule = this.userLimits.get(userId);
+        if (rule === undefined) return;
+
+        const entries = this.getValidEntries(
+            this.userWindows.get(userId),
+            now,
+            rule.windowMs
+        );
+        if (entries.length >= rule.maxCount) {
+            throw new RateLimitExceededError({
+                context: { channel, userId, scope: "user" },
+            });
+        }
+    }
+
+    private isChannelAllowed(
+        channel: NotificationChannel,
+        now: number
+    ): boolean {
+        const rule = this.channelLimits.get(channel);
+        if (rule === undefined) return true;
+
+        const entries = this.getValidEntries(
+            this.channelWindows.get(channel),
+            now,
+            rule.windowMs
+        );
+        return entries.length < rule.maxCount;
+    }
+
+    private isUserAllowed(userId: string, now: number): boolean {
+        const rule = this.userLimits.get(userId);
+        if (rule === undefined) return true;
+
+        const entries = this.getValidEntries(
+            this.userWindows.get(userId),
+            now,
+            rule.windowMs
+        );
+        return entries.length < rule.maxCount;
+    }
+
+    private recordChannel(channel: NotificationChannel, now: number): void {
+        if (!this.channelLimits.has(channel)) return;
+        const entries = this.channelWindows.get(channel) ?? [];
+        entries.push({ timestamp: now });
+        this.channelWindows.set(channel, entries);
+    }
+
+    private recordUser(userId: string, now: number): void {
+        if (!this.userLimits.has(userId)) return;
+        const entries = this.userWindows.get(userId) ?? [];
+        entries.push({ timestamp: now });
+        this.userWindows.set(userId, entries);
+    }
+
+    private getValidEntries(
+        entries: WindowEntry[] | undefined,
+        now: number,
+        windowMs: number
+    ): WindowEntry[] {
+        if (entries === undefined) return [];
+        return entries.filter((e) => now - e.timestamp < windowMs);
+    }
+}

packages/communication/messaging/notification-channel/src/retry/delivery-retry.md

@@ -0,0 +1,72 @@
+# `delivery-retry` — Retry wrapper with dead-letter queue
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`delivery-retry.ts` ships the `DeliveryRetry` wrapper that retries a `DeliveryChannel.send` call with exponential backoff and surfaces exhausted attempts to a dead-letter queue. The wrapper:
+
+1. Calls the wrapped channel up to `maxRetries + 1` total times.
+2. Sleeps `baseDelayMs * 2^(attempt-1)` (capped at `maxDelayMs`) between attempts via an injectable `SleepFn`.
+3. On exhaustion, pushes a `DeadLetterEntry`, fires an optional handler, and throws `DeliveryFailedError`.
+
+## Features
+
+- Configurable `{ maxRetries, baseDelayMs, maxDelayMs }`.
+- Exponential backoff with cap.
+- In-process dead-letter queue with `getDeadLetters` / `clearDeadLetters` surface.
+- `onDeadLetter(handler)` callback for forwarding to a real queue (Redis, SurrealDB) or pager-duty.
+- Injectable `Clock` and `SleepFn` for deterministic tests.
+- Throws `DeliveryFailedError` on exhaustion so the router emits `notification.failed`.
+
+## Usage: Basic
+
+```ts
+import { DeliveryRetry } from "@suaveplan/notification-channel";
+
+const retry = new DeliveryRetry({ maxRetries: 3, baseDelayMs: 500 });
+retry.onDeadLetter((entry) => pagerDuty.alert(entry));
+
+try {
+    await retry.sendWithRetry(emailChannel, notification);
+} catch (err) {
+    /* DeliveryFailedError */
+}
+```
+
+## Usage: Advanced
+
+```ts
+const retry = new DeliveryRetry(
+    { maxRetries: 5, baseDelayMs: 200, maxDelayMs: 10_000 },
+    () => clock.now(),
+    async (ms) => fakeTimers.tick(ms)
+);
+
+retry.onDeadLetter(async (entry) => {
+    await deadLetterQueue.push(entry);
+});
+
+for (const n of notifications) {
+    try {
+        await retry.sendWithRetry(channel, n);
+    } catch {
+        /* already dead-lettered */
+    }
+}
+```
+
+## API Reference
+
+- `DeliveryRetry(config?, clock?, sleep?)` — constructor.
+- `RetryConfig` — `{ maxRetries, baseDelayMs, maxDelayMs? }`.
+- `DeadLetterEntry` — `{ notification, channel, attempts, lastError, failedAt }`.
+- `DeadLetterHandler`, `SleepFn` — callable types.
+- `sendWithRetry(channel, notification): Promise<DeliveryResult>` — throws `DeliveryFailedError` on exhaustion.
+- `onDeadLetter(handler)`, `getDeadLetters()`, `clearDeadLetters()`, `calculateDelay(attempt)`.
+
+## Implementation Notes
+
+The retry counter is 0-indexed: `attempt === 0` is the first call (no delay), `attempt === 1..maxRetries` incur a backoff before the call. `calculateDelay` is public so test suites can pin the schedule against expected values. The injectable `SleepFn` defaults to `setTimeout` — production should keep the default; tests SHOULD inject a no-op sleeper so the suite finishes in milliseconds. The dead-letter queue is in-process — for production durability, register an `onDeadLetter` handler that forwards to a persistent queue. The throw on exhaustion uses `DeliveryFailedError` with a `cause: Error(lastError)` so the upstream `EventBus` listener can introspect the underlying error string.

packages/communication/messaging/notification-channel/src/retry/delivery-retry.test.ts

@@ -0,0 +1,237 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "../channels/delivery-channel.js";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import type { Notification } from "../types/notification.types.js";
+import { DeliveryRetry } from "./delivery-retry.js";
+
+function makeNotification(overrides: Partial<Notification> = {}): Notification {
+    return {
+        id: "notif_1",
+        channel: "email",
+        recipient: "user@example.com",
+        body: "Test",
+        priority: "normal",
+        status: "sending",
+        createdAt: new Date().toISOString(),
+        ...overrides,
+    };
+}
+
+function makeChannel(results: DeliveryResult[]): DeliveryChannel {
+    let callIndex = 0;
+    return {
+        name: "test",
+        canSend: () => true,
+        send: async () => {
+            const r = results[callIndex];
+            callIndex++;
+            if (r === undefined) {
+                throw new Error("ran out of scripted results");
+            }
+            return r;
+        },
+    };
+}
+
+function successResult(): DeliveryResult {
+    return {
+        success: true,
+        channel: "test",
+        messageId: "msg_1",
+        timestamp: new Date().toISOString(),
+    };
+}
+
+function failResult(error = "Failed"): DeliveryResult {
+    return {
+        success: false,
+        channel: "test",
+        error,
+        timestamp: new Date().toISOString(),
+    };
+}
+
+const noSleep = async (_ms: number): Promise<void> => {
+    /* tests skip delays */
+};
+
+describe("DeliveryRetry", () => {
+    it("returns result on first success", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 3, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([successResult()]);
+        const result = await retry.sendWithRetry(channel, makeNotification());
+        expect(result.success).toBe(true);
+    });
+
+    it("retries on failure then succeeds", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 3, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([
+            failResult(),
+            failResult(),
+            successResult(),
+        ]);
+        const result = await retry.sendWithRetry(channel, makeNotification());
+        expect(result.success).toBe(true);
+    });
+
+    it("throws after exhausting retries", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 2, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([
+            failResult("err1"),
+            failResult("err2"),
+            failResult("err3"),
+        ]);
+        await expect(
+            retry.sendWithRetry(channel, makeNotification())
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("adds to dead letter queue on exhaustion", {
+        timeout: 5000,
+    }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 1, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([failResult("fail1"), failResult("fail2")]);
+        try {
+            await retry.sendWithRetry(channel, makeNotification());
+        } catch {
+            // expected
+        }
+        const deadLetters = retry.getDeadLetters();
+        expect(deadLetters).toHaveLength(1);
+        expect(deadLetters[0]?.lastError).toBe("fail2");
+        expect(deadLetters[0]?.attempts).toBe(2);
+    });
+
+    it("calls dead letter handler", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 0, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        let handlerCalled = false;
+        retry.onDeadLetter(() => {
+            handlerCalled = true;
+        });
+        const channel = makeChannel([failResult()]);
+        try {
+            await retry.sendWithRetry(channel, makeNotification());
+        } catch {
+            // expected
+        }
+        expect(handlerCalled).toBe(true);
+    });
+
+    it("clears dead letters", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 0, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([failResult()]);
+        try {
+            await retry.sendWithRetry(channel, makeNotification());
+        } catch {
+            // expected
+        }
+        expect(retry.getDeadLetters()).toHaveLength(1);
+        retry.clearDeadLetters();
+        expect(retry.getDeadLetters()).toHaveLength(0);
+    });
+
+    it("uses 'Unknown delivery error' when result has no error", {
+        timeout: 5000,
+    }, async () => {
+        const retry = new DeliveryRetry(
+            { maxRetries: 0, baseDelayMs: 1 },
+            () => 0,
+            noSleep
+        );
+        const channel = makeChannel([
+            {
+                success: false,
+                channel: "test",
+                timestamp: new Date().toISOString(),
+            },
+        ]);
+        try {
+            await retry.sendWithRetry(channel, makeNotification());
+        } catch {
+            // expected
+        }
+        const deadLetters = retry.getDeadLetters();
+        expect(deadLetters[0]?.lastError).toBe("Unknown delivery error");
+    });
+
+    describe("calculateDelay", () => {
+        it("calculates exponential backoff", { timeout: 5000 }, () => {
+            const retry = new DeliveryRetry({
+                maxRetries: 3,
+                baseDelayMs: 1_000,
+            });
+            expect(retry.calculateDelay(1)).toBe(1_000);
+            expect(retry.calculateDelay(2)).toBe(2_000);
+            expect(retry.calculateDelay(3)).toBe(4_000);
+        });
+
+        it("caps delay at maxDelayMs", { timeout: 5000 }, () => {
+            const retry = new DeliveryRetry({
+                maxRetries: 10,
+                baseDelayMs: 1_000,
+                maxDelayMs: 5_000,
+            });
+            expect(retry.calculateDelay(10)).toBe(5_000);
+        });
+
+        it("uses default maxDelayMs of 30_000", { timeout: 5000 }, () => {
+            const retry = new DeliveryRetry({
+                maxRetries: 10,
+                baseDelayMs: 10_000,
+            });
+            expect(retry.calculateDelay(5)).toBe(30_000);
+        });
+    });
+
+    it("uses default config when none provided", { timeout: 5000 }, () => {
+        const retry = new DeliveryRetry();
+        expect(retry.calculateDelay(1)).toBe(1_000);
+    });
+
+    it("uses default clock when none injected", { timeout: 5000 }, async () => {
+        const retry = new DeliveryRetry({ maxRetries: 0, baseDelayMs: 1 });
+        const channel = makeChannel([failResult("boom")]);
+        try {
+            await retry.sendWithRetry(channel, makeNotification());
+        } catch {
+            // expected
+        }
+        const entry = retry.getDeadLetters()[0];
+        expect(entry?.failedAt).toBeDefined();
+    });
+
+    it("default sleeper runs without throwing", { timeout: 5000 }, async () => {
+        // Cover the default sleep code path; 1ms keeps the test fast.
+        const retry = new DeliveryRetry({ maxRetries: 1, baseDelayMs: 1 });
+        const channel = makeChannel([failResult(), successResult()]);
+        const result = await retry.sendWithRetry(channel, makeNotification());
+        expect(result.success).toBe(true);
+    });
+});

packages/communication/messaging/notification-channel/src/retry/delivery-retry.ts

@@ -0,0 +1,143 @@
+import type { Clock } from "@suaveplan/types";
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "../channels/delivery-channel.js";
+import { DeliveryFailedError } from "../error-codes/error-codes.js";
+import type { Notification } from "../types/notification.types.js";
+
+/** Configuration for retry behaviour. */
+export interface RetryConfig {
+    /** Maximum number of retry attempts (default: 3). */
+    readonly maxRetries: number;
+    /** Base delay in ms for exponential backoff (default: 1_000). */
+    readonly baseDelayMs: number;
+    /** Maximum delay cap in ms (default: 30_000). */
+    readonly maxDelayMs?: number;
+}
+
+/** Record of a failed delivery that exhausted retries. */
+export interface DeadLetterEntry {
+    readonly notification: Notification;
+    readonly channel: string;
+    readonly attempts: number;
+    readonly lastError: string;
+    readonly failedAt: string;
+}
+
+/** Callback for dead-letter events. */
+export type DeadLetterHandler = (entry: DeadLetterEntry) => void;
+
+/** Sleep adapter; tests inject a no-op or fake-timer-driven sleeper. */
+export type SleepFn = (ms: number) => Promise<void>;
+
+const DEFAULT_CONFIG: RetryConfig = {
+    maxRetries: 3,
+    baseDelayMs: 1_000,
+    maxDelayMs: 30_000,
+};
+
+const defaultClock: Clock = () => Date.now();
+const defaultSleep: SleepFn = (ms: number) =>
+    new Promise<void>((resolve) => setTimeout(resolve, ms));
+
+/**
+ * Wraps a `DeliveryChannel` with exponential-backoff retry and a
+ * dead-letter queue. The wrapper:
+ *
+ *   1. Calls the channel up to `maxRetries + 1` times.
+ *   2. Sleeps `baseDelayMs * 2^(attempt-1)` (capped at `maxDelayMs`)
+ *      between attempts via the injectable `SleepFn`.
+ *   3. On exhaustion, pushes a `DeadLetterEntry`, fires the optional
+ *      handler, and throws `DeliveryFailedError`.
+ */
+export class DeliveryRetry {
+    private readonly config: RetryConfig;
+    private readonly deadLetters: DeadLetterEntry[] = [];
+    private deadLetterHandler?: DeadLetterHandler;
+    private readonly clock: Clock;
+    private readonly sleep: SleepFn;
+
+    public constructor(
+        config?: Partial<RetryConfig>,
+        clock: Clock = defaultClock,
+        sleep: SleepFn = defaultSleep
+    ) {
+        this.config = { ...DEFAULT_CONFIG, ...config };
+        this.clock = clock;
+        this.sleep = sleep;
+    }
+
+    /** Register a handler called when an entry hits the dead-letter queue. */
+    public onDeadLetter(handler: DeadLetterHandler): void {
+        this.deadLetterHandler = handler;
+    }
+
+    /** Snapshot of the current dead-letter queue. */
+    public getDeadLetters(): readonly DeadLetterEntry[] {
+        return this.deadLetters;
+    }
+
+    /** Clear the dead-letter queue. */
+    public clearDeadLetters(): void {
+        this.deadLetters.length = 0;
+    }
+
+    /**
+     * Attempt delivery with retries using exponential backoff.
+     * Returns the successful result or throws after exhausting retries.
+     */
+    public async sendWithRetry(
+        channel: DeliveryChannel,
+        notification: Notification
+    ): Promise<DeliveryResult> {
+        let lastError = "";
+
+        for (let attempt = 0; attempt <= this.config.maxRetries; attempt++) {
+            if (attempt > 0) {
+                const delay = this.calculateDelay(attempt);
+                await this.sleep(delay);
+            }
+
+            const result = await channel.send(notification);
+            if (result.success) {
+                return result;
+            }
+
+            lastError = result.error ?? "Unknown delivery error";
+        }
+
+        const entry: DeadLetterEntry = {
+            notification,
+            channel: channel.name,
+            attempts: this.config.maxRetries + 1,
+            lastError,
+            failedAt: new Date(this.clock()).toISOString(),
+        };
+
+        this.deadLetters.push(entry);
+        if (this.deadLetterHandler !== undefined) {
+            this.deadLetterHandler(entry);
+        }
+
+        throw new DeliveryFailedError({
+            cause: new Error(lastError),
+            context: {
+                notificationId: notification.id,
+                channel: channel.name,
+                attempts: entry.attempts,
+            },
+        });
+    }
+
+    /** Delay for `attempt` (1-indexed) using exponential backoff. */
+    public calculateDelay(attempt: number): number {
+        const delay = this.config.baseDelayMs * 2 ** (attempt - 1);
+        // `DEFAULT_CONFIG.maxDelayMs` is always merged into `this.config`
+        // via the constructor spread, so the field is always defined; the
+        // `as number` cast keeps `noUncheckedIndexedAccess` happy without
+        // introducing an unreachable `??` branch.
+        const maxDelay = this.config.maxDelayMs as number;
+        return Math.min(delay, maxDelay);
+    }
+}

packages/communication/messaging/notification-channel/src/router/notification-router-routing.test.ts

@@ -0,0 +1,282 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import { notificationHooks, onNotificationRouting } from "../hooks/hooks.js";
+import type {
+    ChannelConfig,
+    RoutingRule,
+} from "../types/notification.types.js";
+import { NotificationRouter } from "./notification-router.js";
+
+function makeRouter(
+    options: {
+        channels?: ChannelConfig[];
+        routingRules?: RoutingRule[];
+        clock?: () => number;
+    } = {}
+): NotificationRouter {
+    return new NotificationRouter({
+        channels: options.channels ?? [
+            { channel: "email", enabled: true },
+            { channel: "sms", enabled: true },
+            { channel: "push", enabled: true },
+            { channel: "in_app", enabled: true },
+        ],
+        ...(options.routingRules !== undefined
+            ? { routingRules: options.routingRules }
+            : {}),
+        defaultChannel: "email",
+        ...(options.clock !== undefined ? { clock: options.clock } : {}),
+    });
+}
+
+describe("NotificationRouter — rate limiting", () => {
+    it("enforces rate limit per channel", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            channels: [{ channel: "email", enabled: true, rateLimit: 2 }],
+        });
+        await router.send({
+            recipient: "a@a.com",
+            body: "A",
+            channel: "email",
+        });
+        await router.send({
+            recipient: "b@b.com",
+            body: "B",
+            channel: "email",
+        });
+        await expect(
+            router.send({
+                recipient: "c@c.com",
+                body: "C",
+                channel: "email",
+            })
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("does not rate limit when no limit set", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        for (let i = 0; i < 50; i++) {
+            await router.send({
+                recipient: `u${i}@a.com`,
+                body: "msg",
+                channel: "email",
+            });
+        }
+        const stats = await router.getChannelStats();
+        expect(stats.email.sent).toBe(50);
+    });
+
+    it("resets rate-limit window after the 60s window", {
+        timeout: 5000,
+    }, async () => {
+        let now = 1_000_000;
+        const router = makeRouter({
+            channels: [{ channel: "email", enabled: true, rateLimit: 1 }],
+            clock: () => now,
+        });
+        await router.send({
+            recipient: "a@a.com",
+            body: "A",
+            channel: "email",
+        });
+        now += 61_000;
+        const result = await router.send({
+            recipient: "b@b.com",
+            body: "B",
+            channel: "email",
+        });
+        expect(result.status).toBe("sent");
+    });
+});
+
+describe("NotificationRouter — routing rules", () => {
+    it("routes based on priority rule", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            routingRules: [
+                {
+                    id: "r1",
+                    name: "Urgent to SMS",
+                    channels: ["sms"],
+                    priority: "urgent",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "+15551234567",
+            body: "Urgent!",
+            priority: "urgent",
+        });
+        expect(result.channel).toBe("sms");
+    });
+
+    it("routes based on condition", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            routingRules: [
+                {
+                    id: "r1",
+                    name: "VIP to push",
+                    channels: ["push"],
+                    condition: (recipient) => recipient.startsWith("vip_"),
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "vip_user",
+            body: "VIP notification",
+        });
+        expect(result.channel).toBe("push");
+    });
+
+    it("falls back to default when no rule matches", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter({
+            routingRules: [
+                {
+                    id: "r1",
+                    name: "Urgent to SMS",
+                    channels: ["sms"],
+                    priority: "urgent",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Normal",
+            priority: "normal",
+        });
+        expect(result.channel).toBe("email");
+    });
+
+    it("adds routing rules dynamically", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        await router.addRoutingRule({
+            id: "r2",
+            name: "All to in_app",
+            channels: ["in_app"],
+        });
+        const result = await router.send({
+            recipient: "user",
+            body: "Hello",
+        });
+        expect(result.channel).toBe("in_app");
+    });
+
+    it("skips rules with non-matching conditions", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter({
+            routingRules: [
+                {
+                    id: "r1",
+                    name: "Admin only",
+                    channels: ["push"],
+                    condition: (r) => r === "admin",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "regular_user",
+            body: "Hello",
+        });
+        expect(result.channel).toBe("email");
+    });
+
+    it("uses first matching rule channel", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            routingRules: [
+                { id: "r1", name: "First", channels: ["sms", "push"] },
+            ],
+        });
+        const result = await router.send({
+            recipient: "user",
+            body: "Hello",
+        });
+        expect(result.channel).toBe("sms");
+    });
+
+    it("falls back to default when rule has empty channel list", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter({
+            routingRules: [{ id: "r1", name: "empty", channels: [] }],
+        });
+        const result = await router.send({
+            recipient: "user",
+            body: "Hello",
+        });
+        expect(result.channel).toBe("email");
+    });
+});
+
+describe("NotificationRouter — priority handling", () => {
+    it("stores notification with priority", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Urgent!",
+            priority: "urgent",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.priority).toBe("urgent");
+    });
+
+    it("defaults priority to normal", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hi",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.priority).toBe("normal");
+    });
+
+    it("stores low priority", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Low",
+            priority: "low",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.priority).toBe("low");
+    });
+
+    it("stores high priority", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "High",
+            priority: "high",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.priority).toBe("high");
+    });
+});
+
+describe("NotificationRouter — hook integration", () => {
+    it("notification:routing hook can override resolved channel", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const off = onNotificationRouting((data) => {
+            if (data.input.priority === "urgent") {
+                return { resolvedChannel: "sms" };
+            }
+            return undefined;
+        });
+        try {
+            const result = await router.send({
+                recipient: "+15551234567",
+                body: "Urgent!",
+                priority: "urgent",
+            });
+            expect(result.channel).toBe("sms");
+        } finally {
+            off();
+            notificationHooks.clear("notification:routing");
+        }
+    });
+});

packages/communication/messaging/notification-channel/src/router/notification-router.md

@@ -0,0 +1,89 @@
+# `notification-router` — Primary multi-channel router
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`notification-router.ts` ships the `NotificationRouter` class — the primary entrypoint a consumer talks to. It resolves the target channel (input override → routing rules → default), runs the `notification:routing` hook pipeline, resolves the body / subject (template render or raw), checks the channel is enabled and within rate limit, optionally dispatches to a registered `DeliveryChannel`, persists the notification record, and emits a lifecycle event (`notification.sent` / `notification.failed` / `notification.cancelled` / `notification.created`) on its internal `EventBus`. Every public boundary is Zod-validated.
+
+## Features
+
+- Channel resolution: input override → routing rules (priority and predicate filters) → default channel.
+- Template-based content with `{{var}}` substitution.
+- Per-channel 60-second window rate limiting (in-process — wire `ChannelRateLimiter` for richer policies).
+- Lifecycle events via `EventBus`: `notification.created`, `notification.sent`, `notification.failed`, `notification.cancelled`.
+- Optional in-pipeline `DeliveryChannel` dispatch.
+- OpenTelemetry meters on every send.
+- Zod-validated config at the constructor boundary.
+- Injectable `Clock` for deterministic tests.
+
+## Usage: Basic
+
+```ts
+import { NotificationRouter } from "@suaveplan/notification-channel";
+
+const router = new NotificationRouter({
+    channels: [
+        { channel: "email", enabled: true },
+        { channel: "sms", enabled: true },
+    ],
+    defaultChannel: "email",
+});
+
+const result = await router.send({
+    recipient: "user@example.com",
+    body: "Welcome!",
+});
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    EmailChannel,
+    NotificationRouter,
+} from "@suaveplan/notification-channel";
+
+const email = new EmailChannel({ from: "noreply@x", sendFn: provider.send });
+
+const router = new NotificationRouter({
+    channels: [{ channel: "email", enabled: true, rateLimit: 100 }],
+    templates: [
+        {
+            id: "welcome",
+            name: "Welcome",
+            channel: "email",
+            subject: "Welcome {{name}}",
+            bodyTemplate: "Hi {{name}}",
+            defaultPriority: "normal",
+        },
+    ],
+    routingRules: [
+        { id: "urgent-to-sms", name: "u", channels: ["sms"], priority: "urgent" },
+    ],
+    defaultChannel: "email",
+    deliveryChannels: [email],
+});
+
+router.on("notification.failed", (n) => audit.record(n));
+await router.send({
+    recipient: "u@x",
+    body: "",
+    templateId: "welcome",
+    templateData: { name: "Alice" },
+});
+```
+
+## API Reference
+
+- `NotificationRouter(config: NotificationRouterConfig)` — constructor.
+- `send(input)`, `enqueue(input)`, `sendBatch(inputs)`, `getNotification(id)`, `cancel(id)`, `getChannelStats()`.
+- `registerChannel(c)`, `registerTemplate(t)`, `addRoutingRule(r)`, `registerDeliveryChannel(dc)`.
+- `on(event, listener)` — subscribe to lifecycle events.
+- `NotificationRouterConfig` — `{ channels, templates?, routingRules?, defaultChannel, deliveryChannels?, clock? }`.
+
+## Implementation Notes
+
+The internal 60-second rate-limit window is a fixed bucket per channel — for sliding-window or per-user limits, layer `ChannelRateLimiter` outside the router. `cancel` consults `VALID_TRANSITIONS` so cancelling a `sent` notification rejects (cannot transition `sent → cancelled`). The router uses `EventBus<NotificationEventMap>` so consumers get typed `on(...)` and the underlying envelope semantics — interceptors, abort signals — that ship in `@suaveplan/events`. Construction Zod-parses the config; runtime calls trust the inputs because `send` runs on every notification and re-validating on every call is wasteful — consumers MUST validate `NotificationInput` themselves if they accept it from untrusted sources.

packages/communication/messaging/notification-channel/src/router/notification-router.test.ts

@@ -0,0 +1,534 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type {
+    DeliveryChannel,
+    DeliveryResult,
+} from "../channels/delivery-channel.js";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import type {
+    ChannelConfig,
+    Notification,
+    NotificationTemplate,
+} from "../types/notification.types.js";
+import { NotificationRouter } from "./notification-router.js";
+
+function makeRouter(
+    overrides: {
+        channels?: ChannelConfig[];
+        templates?: NotificationTemplate[];
+    } = {}
+): NotificationRouter {
+    return new NotificationRouter({
+        channels: overrides.channels ?? [
+            { channel: "email", enabled: true },
+            { channel: "sms", enabled: true },
+            { channel: "push", enabled: true },
+            { channel: "in_app", enabled: true },
+        ],
+        ...(overrides.templates !== undefined
+            ? { templates: overrides.templates }
+            : {}),
+        defaultChannel: "email",
+    });
+}
+
+describe("NotificationRouter — send + lifecycle", () => {
+    it("sends a notification to a channel", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Hello",
+            channel: "email",
+        });
+        expect(result.status).toBe("sent");
+        expect(result.channel).toBe("email");
+        expect(result.id).toBeDefined();
+    });
+
+    it("uses default channel when not specified", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Hello",
+        });
+        expect(result.channel).toBe("email");
+    });
+
+    it("includes sentAt timestamp", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Hello",
+        });
+        expect(result.sentAt).toBeDefined();
+    });
+
+    it("emits notification.sent event", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        let emitted = false;
+        router.on("notification.sent", () => {
+            emitted = true;
+        });
+        await router.send({ recipient: "user@example.com", body: "Hello" });
+        expect(emitted).toBe(true);
+    });
+
+    it("throws when channel is disabled", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            channels: [{ channel: "email", enabled: false }],
+        });
+        await expect(
+            router.send({
+                recipient: "user@example.com",
+                body: "Hello",
+                channel: "email",
+            })
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("throws when channel is not registered", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter({
+            channels: [{ channel: "email", enabled: true }],
+        });
+        await expect(
+            router.send({
+                recipient: "user@example.com",
+                body: "Hello",
+                channel: "webhook",
+            })
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("sends to sms channel", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "+15551234567",
+            body: "Hello SMS",
+            channel: "sms",
+        });
+        expect(result.channel).toBe("sms");
+    });
+
+    it("sends with subject", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Hello",
+            subject: "Test Subject",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.subject).toBe("Test Subject");
+    });
+
+    it("sends with metadata", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "user@example.com",
+            body: "Hello",
+            metadata: { source: "test" },
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.metadata).toEqual({ source: "test" });
+    });
+
+    it("assigns unique ids to each notification", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const r1 = await router.send({ recipient: "a@a.com", body: "A" });
+        const r2 = await router.send({ recipient: "b@b.com", body: "B" });
+        expect(r1.id).not.toBe(r2.id);
+    });
+
+    it("sendBatch returns one result per input", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const results = await router.sendBatch([
+            { recipient: "a@a.com", body: "Hello A" },
+            { recipient: "b@b.com", body: "Hello B" },
+            { recipient: "c@c.com", body: "Hello C" },
+        ]);
+        expect(results).toHaveLength(3);
+        expect(results.every((r) => r.status === "sent")).toBe(true);
+    });
+
+    it("sendBatch returns empty for empty input", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const results = await router.sendBatch([]);
+        expect(results).toHaveLength(0);
+    });
+
+    it("retrieves a sent notification", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.body).toBe("Hello");
+        expect(notif.recipient).toBe("a@a.com");
+    });
+
+    it("getNotification throws for non-existent id", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        await expect(router.getNotification("fake")).rejects.toThrow(
+            NotificationChannelError
+        );
+    });
+
+    it("enqueue creates a pending notification", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const result = await router.enqueue({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        expect(result.status).toBe("pending");
+        const notif = await router.getNotification(result.id);
+        expect(notif.status).toBe("pending");
+    });
+
+    it("enqueue records subject and metadata when provided", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const result = await router.enqueue({
+            recipient: "a@a.com",
+            body: "Hi",
+            subject: "Pending subject",
+            metadata: { trace: "t-1" },
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.subject).toBe("Pending subject");
+        expect(notif.metadata).toEqual({ trace: "t-1" });
+    });
+
+    it("enqueue emits notification.created event", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        let emitted = false;
+        router.on("notification.created", () => {
+            emitted = true;
+        });
+        await router.enqueue({ recipient: "a@a.com", body: "Hello" });
+        expect(emitted).toBe(true);
+    });
+
+    it("cancels a pending notification", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        const result = await router.enqueue({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        const cancelled = await router.cancel(result.id);
+        expect(cancelled.status).toBe("cancelled");
+    });
+
+    it("emits notification.cancelled event", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        let emitted = false;
+        router.on("notification.cancelled", () => {
+            emitted = true;
+        });
+        const result = await router.enqueue({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        await router.cancel(result.id);
+        expect(emitted).toBe(true);
+    });
+
+    it("throws when cancelling sent notification", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        await expect(router.cancel(result.id)).rejects.toThrow(
+            NotificationChannelError
+        );
+    });
+
+    it("cancel throws for non-existent id", { timeout: 5000 }, async () => {
+        const router = makeRouter();
+        await expect(router.cancel("fake")).rejects.toThrow(
+            NotificationChannelError
+        );
+    });
+
+    it("getChannelStats reports per-channel sent count", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        await router.send({
+            recipient: "a@a.com",
+            body: "A",
+            channel: "email",
+        });
+        await router.send({
+            recipient: "b@b.com",
+            body: "B",
+            channel: "sms",
+        });
+        const stats = await router.getChannelStats();
+        expect(stats.email.sent).toBe(1);
+        expect(stats.sms.sent).toBe(1);
+        expect(stats.email.enabled).toBe(true);
+    });
+
+    it("registerChannel overrides existing channel config", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        await router.registerChannel({ channel: "email", enabled: false });
+        await expect(
+            router.send({
+                recipient: "a@a.com",
+                body: "Hello",
+                channel: "email",
+            })
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("registerChannel can add a new channel", { timeout: 5000 }, async () => {
+        const router = makeRouter({ channels: [] });
+        await router.registerChannel({ channel: "webhook", enabled: true });
+        const result = await router.send({
+            recipient: "https://hook.example.com",
+            body: "{}",
+            channel: "webhook",
+        });
+        expect(result.channel).toBe("webhook");
+    });
+
+    it("registerTemplate registers and uses a template", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        await router.registerTemplate({
+            id: "tpl_welcome",
+            name: "Welcome",
+            channel: "email",
+            subject: "Welcome {{name}}",
+            bodyTemplate: "Hello {{name}}, welcome to {{app}}!",
+            defaultPriority: "normal",
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "",
+            templateId: "tpl_welcome",
+            templateData: { name: "Alice", app: "Suaveplan" },
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.body).toBe("Hello Alice, welcome to Suaveplan!");
+        expect(notif.subject).toBe("Welcome Alice");
+    });
+
+    it("templates render body with variables", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            templates: [
+                {
+                    id: "tpl_1",
+                    name: "Test",
+                    channel: "email",
+                    bodyTemplate: "Hi {{user}}, code: {{code}}",
+                    defaultPriority: "normal",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "",
+            templateId: "tpl_1",
+            templateData: { user: "Bob", code: "1234" },
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.body).toBe("Hi Bob, code: 1234");
+    });
+
+    it("templates throws for non-existent template", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        await expect(
+            router.send({
+                recipient: "a@a.com",
+                body: "",
+                templateId: "fake",
+            })
+        ).rejects.toThrow(NotificationChannelError);
+    });
+
+    it("uses input subject over template subject", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter({
+            templates: [
+                {
+                    id: "tpl_1",
+                    name: "Test",
+                    channel: "email",
+                    subject: "Template Subject",
+                    bodyTemplate: "Body",
+                    defaultPriority: "normal",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "",
+            subject: "Custom Subject",
+            templateId: "tpl_1",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.subject).toBe("Custom Subject");
+    });
+
+    it("renders template without data", { timeout: 5000 }, async () => {
+        const router = makeRouter({
+            templates: [
+                {
+                    id: "tpl_1",
+                    name: "Test",
+                    channel: "email",
+                    bodyTemplate: "Static body",
+                    defaultPriority: "normal",
+                },
+            ],
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "",
+            templateId: "tpl_1",
+        });
+        const notif = await router.getNotification(result.id);
+        expect(notif.body).toBe("Static body");
+    });
+
+    it("dispatches to registered DeliveryChannel and reports failure", {
+        timeout: 5000,
+    }, async () => {
+        const failing: DeliveryChannel = {
+            name: "email",
+            canSend: () => true,
+            send: async (): Promise<DeliveryResult> => ({
+                success: false,
+                channel: "email",
+                error: "downstream went boom",
+                timestamp: new Date().toISOString(),
+            }),
+        };
+        const router = new NotificationRouter({
+            channels: [{ channel: "email", enabled: true }],
+            defaultChannel: "email",
+            deliveryChannels: [failing],
+        });
+        let failedEvent: Notification | undefined;
+        router.on("notification.failed", (n) => {
+            failedEvent = n;
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        expect(result.status).toBe("failed");
+        expect(result.error).toBe("downstream went boom");
+        expect(failedEvent?.status).toBe("failed");
+    });
+
+    it("dispatches failure without an error string when channel omits one", {
+        timeout: 5000,
+    }, async () => {
+        const silentlyFailing: DeliveryChannel = {
+            name: "email",
+            canSend: () => true,
+            send: async (): Promise<DeliveryResult> => ({
+                success: false,
+                channel: "email",
+                timestamp: new Date().toISOString(),
+            }),
+        };
+        const router = new NotificationRouter({
+            channels: [{ channel: "email", enabled: true }],
+            defaultChannel: "email",
+            deliveryChannels: [silentlyFailing],
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        expect(result.status).toBe("failed");
+        expect(result.error).toBeUndefined();
+    });
+
+    it("dispatches to registered DeliveryChannel on success", {
+        timeout: 5000,
+    }, async () => {
+        const ok: DeliveryChannel = {
+            name: "email",
+            canSend: () => true,
+            send: async (): Promise<DeliveryResult> => ({
+                success: true,
+                channel: "email",
+                messageId: "msg-x",
+                timestamp: new Date().toISOString(),
+            }),
+        };
+        const router = new NotificationRouter({
+            channels: [{ channel: "email", enabled: true }],
+            defaultChannel: "email",
+            deliveryChannels: [ok],
+        });
+        const result = await router.send({
+            recipient: "a@a.com",
+            body: "Hello",
+        });
+        expect(result.status).toBe("sent");
+    });
+
+    it("registerDeliveryChannel adds runtime delivery channel", {
+        timeout: 5000,
+    }, async () => {
+        const router = makeRouter();
+        let invoked = false;
+        router.registerDeliveryChannel({
+            name: "email",
+            canSend: () => true,
+            send: async () => {
+                invoked = true;
+                return {
+                    success: true,
+                    channel: "email",
+                    messageId: "ok",
+                    timestamp: new Date().toISOString(),
+                };
+            },
+        });
+        await router.send({ recipient: "a@a.com", body: "Hi" });
+        expect(invoked).toBe(true);
+    });
+
+    it("Zod boundary rejects malformed router config", {
+        timeout: 5000,
+    }, () => {
+        expect(
+            () =>
+                new NotificationRouter({
+                    channels: "wrong" as unknown as ChannelConfig[],
+                    defaultChannel: "email",
+                })
+        ).toThrow();
+    });
+});

packages/communication/messaging/notification-channel/src/router/notification-router.ts

@@ -0,0 +1,405 @@
+import { EventBus } from "@suaveplan/events";
+import type { Clock } from "@suaveplan/types";
+import type { DeliveryChannel } from "../channels/delivery-channel.js";
+import {
+    ChannelDisabledError,
+    NotificationNotFoundError,
+    RateLimitExceededError,
+    RoutingFailedError,
+    TemplateNotFoundError,
+} from "../error-codes/error-codes.js";
+import { notificationHooks } from "../hooks/hooks.js";
+import { recordDeliveryAttempt, recordRouted } from "../otel/metrics.js";
+import { NotificationRouterConfigSchema } from "../schemas/schemas.js";
+import type {
+    ChannelConfig,
+    Notification,
+    NotificationChannel,
+    NotificationEventMap,
+    NotificationInput,
+    NotificationResult,
+    NotificationTemplate,
+    RoutingRule,
+} from "../types/notification.types.js";
+import { VALID_TRANSITIONS } from "../types/notification.types.js";
+
+/** Public configuration for `NotificationRouter`. */
+export interface NotificationRouterConfig {
+    readonly channels: readonly ChannelConfig[];
+    readonly templates?: readonly NotificationTemplate[];
+    readonly routingRules?: readonly RoutingRule[];
+    readonly defaultChannel: NotificationChannel;
+    readonly deliveryChannels?: readonly DeliveryChannel[];
+    readonly clock?: Clock;
+}
+
+interface ChannelState {
+    config: ChannelConfig;
+    sentCount: number;
+    windowStart: number;
+}
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Routes notifications across channels with template rendering,
+ * rate-limit gating, lifecycle tracking, and EventBus emission. The
+ * router is the single integration point a consumer talks to;
+ * everything else (rate limiter, scheduler, retry, preferences) is
+ * composable on top.
+ */
+export class NotificationRouter {
+    private readonly notifications = new Map<string, Notification>();
+    private readonly channelStates = new Map<
+        NotificationChannel,
+        ChannelState
+    >();
+    private readonly templates = new Map<string, NotificationTemplate>();
+    private readonly routingRules: RoutingRule[] = [];
+    private readonly deliveryChannels = new Map<string, DeliveryChannel>();
+    private readonly defaultChannel: NotificationChannel;
+    private readonly clock: Clock;
+    private readonly bus = new EventBus<NotificationEventMap>();
+    private nextId = 1;
+
+    public constructor(config: NotificationRouterConfig) {
+        // Zod boundary — reject malformed config before any state mutates.
+        NotificationRouterConfigSchema.parse({
+            channels: config.channels,
+            ...(config.templates !== undefined
+                ? { templates: config.templates }
+                : {}),
+            ...(config.routingRules !== undefined
+                ? { routingRules: config.routingRules }
+                : {}),
+            defaultChannel: config.defaultChannel,
+            ...(config.deliveryChannels !== undefined
+                ? { deliveryChannels: config.deliveryChannels }
+                : {}),
+            ...(config.clock !== undefined ? { clock: config.clock } : {}),
+        });
+
+        this.defaultChannel = config.defaultChannel;
+        this.clock = config.clock ?? defaultClock;
+
+        for (const ch of config.channels) {
+            this.channelStates.set(ch.channel, {
+                config: ch,
+                sentCount: 0,
+                windowStart: this.clock(),
+            });
+        }
+
+        if (config.templates !== undefined) {
+            for (const tpl of config.templates) {
+                this.templates.set(tpl.id, tpl);
+            }
+        }
+
+        if (config.routingRules !== undefined) {
+            this.routingRules.push(...config.routingRules);
+        }
+
+        if (config.deliveryChannels !== undefined) {
+            for (const dc of config.deliveryChannels) {
+                this.deliveryChannels.set(dc.name, dc);
+            }
+        }
+    }
+
+    /** Subscribe to a router-emitted lifecycle event. */
+    public on<K extends keyof NotificationEventMap>(
+        type: K,
+        listener: (payload: NotificationEventMap[K]) => void
+    ): () => void {
+        return this.bus.on(type, listener);
+    }
+
+    /** Send a notification end-to-end. */
+    public async send(input: NotificationInput): Promise<NotificationResult> {
+        const start = this.clock();
+        let channel = this.resolveChannel(input);
+        const hookResult = await notificationHooks.applyHooksAsync(
+            "notification:routing",
+            {
+                input,
+                resolvedChannel: channel,
+                metadata: {},
+            }
+        );
+        channel = hookResult.resolvedChannel;
+        const { body, subject } = this.resolveContent(hookResult.input);
+        const priority = hookResult.input.priority ?? "normal";
+
+        try {
+            this.checkChannel(channel);
+            this.checkRateLimit(channel);
+        } catch (err) {
+            recordRouted(channel, "failed", this.clock() - start);
+            throw err;
+        }
+
+        const id = `notif_${this.nextId++}`;
+        const now = new Date(this.clock()).toISOString();
+
+        const baseNotification: Notification = {
+            id,
+            channel,
+            recipient: input.recipient,
+            ...(subject !== undefined ? { subject } : {}),
+            body,
+            priority,
+            status: "sent",
+            ...(input.metadata !== undefined
+                ? { metadata: input.metadata }
+                : {}),
+            createdAt: now,
+            sentAt: now,
+        };
+
+        this.notifications.set(id, baseNotification);
+        this.incrementRateCounter(channel);
+
+        const dc = this.deliveryChannels.get(channel);
+        if (dc !== undefined) {
+            const deliveryResult = await dc.send(baseNotification);
+            if (!deliveryResult.success) {
+                const failed: Notification = {
+                    ...baseNotification,
+                    status: "failed",
+                };
+                this.notifications.set(id, failed);
+                this.bus.emit("notification.failed", failed);
+                recordDeliveryAttempt(channel, "failed");
+                recordRouted(channel, "failed", this.clock() - start);
+                const errResult: NotificationResult = {
+                    id,
+                    channel,
+                    status: "failed",
+                    ...(deliveryResult.error !== undefined
+                        ? { error: deliveryResult.error }
+                        : {}),
+                };
+                return errResult;
+            }
+            recordDeliveryAttempt(channel, "ok");
+        }
+
+        this.bus.emit("notification.sent", baseNotification);
+        recordRouted(channel, "ok", this.clock() - start);
+        return { id, channel, status: "sent", sentAt: now };
+    }
+
+    /** Enqueue a `pending` notification without delivering. */
+    public async enqueue(
+        input: NotificationInput
+    ): Promise<NotificationResult> {
+        const channel = this.resolveChannel(input);
+        const { body, subject } = this.resolveContent(input);
+        const priority = input.priority ?? "normal";
+        this.checkChannel(channel);
+        const id = `notif_${this.nextId++}`;
+        const now = new Date(this.clock()).toISOString();
+        const notification: Notification = {
+            id,
+            channel,
+            recipient: input.recipient,
+            ...(subject !== undefined ? { subject } : {}),
+            body,
+            priority,
+            status: "pending",
+            ...(input.metadata !== undefined
+                ? { metadata: input.metadata }
+                : {}),
+            createdAt: now,
+        };
+        this.notifications.set(id, notification);
+        this.bus.emit("notification.created", notification);
+        return { id, channel, status: "pending" };
+    }
+
+    /** Send a batch sequentially, returning a result per input. */
+    public async sendBatch(
+        inputs: readonly NotificationInput[]
+    ): Promise<NotificationResult[]> {
+        const results: NotificationResult[] = [];
+        for (const input of inputs) {
+            results.push(await this.send(input));
+        }
+        return results;
+    }
+
+    /** Retrieve a notification by id. */
+    public async getNotification(id: string): Promise<Notification> {
+        const notif = this.notifications.get(id);
+        if (notif === undefined) {
+            throw new NotificationNotFoundError({
+                context: { notificationId: id },
+            });
+        }
+        return notif;
+    }
+
+    /** Cancel a pending notification (rejects when transition is illegal). */
+    public async cancel(id: string): Promise<Notification> {
+        const notif = this.notifications.get(id);
+        if (notif === undefined) {
+            throw new NotificationNotFoundError({
+                context: { notificationId: id },
+            });
+        }
+
+        const validTargets = VALID_TRANSITIONS[notif.status];
+        if (!validTargets.includes("cancelled")) {
+            throw new RoutingFailedError({
+                context: { notificationId: id, fromStatus: notif.status },
+            });
+        }
+
+        const updated: Notification = { ...notif, status: "cancelled" };
+        this.notifications.set(id, updated);
+        this.bus.emit("notification.cancelled", updated);
+        return updated;
+    }
+
+    /** Snapshot of per-channel stats for observability. */
+    public async getChannelStats(): Promise<
+        Record<NotificationChannel, { sent: number; enabled: boolean }>
+    > {
+        const stats = {} as Record<
+            NotificationChannel,
+            { sent: number; enabled: boolean }
+        >;
+
+        for (const [channel, state] of this.channelStates) {
+            stats[channel] = {
+                sent: state.sentCount,
+                enabled: state.config.enabled,
+            };
+        }
+        return stats;
+    }
+
+    /** Register or replace a channel config at runtime. */
+    public async registerChannel(config: ChannelConfig): Promise<void> {
+        this.channelStates.set(config.channel, {
+            config,
+            sentCount: 0,
+            windowStart: this.clock(),
+        });
+    }
+
+    /** Register or replace a template at runtime. */
+    public async registerTemplate(
+        template: NotificationTemplate
+    ): Promise<void> {
+        this.templates.set(template.id, template);
+    }
+
+    /** Append a routing rule at runtime. */
+    public async addRoutingRule(rule: RoutingRule): Promise<void> {
+        this.routingRules.push(rule);
+    }
+
+    /** Register a delivery-channel implementation. */
+    public registerDeliveryChannel(channel: DeliveryChannel): void {
+        this.deliveryChannels.set(channel.name, channel);
+    }
+
+    private resolveChannel(input: NotificationInput): NotificationChannel {
+        if (input.channel !== undefined) return input.channel;
+
+        for (const rule of this.routingRules) {
+            if (
+                rule.priority !== undefined &&
+                input.priority !== undefined &&
+                rule.priority !== input.priority
+            ) {
+                continue;
+            }
+            if (
+                rule.condition !== undefined &&
+                !rule.condition(input.recipient)
+            ) {
+                continue;
+            }
+            if (rule.channels.length > 0) {
+                // length > 0 ⇒ index 0 is defined; the `as` cast keeps
+                // `noUncheckedIndexedAccess` happy without an unreachable
+                // guard branch.
+                return rule.channels[0] as NotificationChannel;
+            }
+        }
+
+        return this.defaultChannel;
+    }
+
+    private resolveContent(input: NotificationInput): {
+        body: string;
+        subject?: string;
+    } {
+        if (input.templateId !== undefined) {
+            const tpl = this.templates.get(input.templateId);
+            if (tpl === undefined) {
+                throw new TemplateNotFoundError({
+                    context: { templateId: input.templateId },
+                });
+            }
+
+            let body = tpl.bodyTemplate;
+            let subject = tpl.subject;
+            const data = input.templateData ?? {};
+
+            for (const [key, value] of Object.entries(data)) {
+                const pattern = `{{${key}}}`;
+                body = body.split(pattern).join(value);
+                if (subject !== undefined) {
+                    subject = subject.split(pattern).join(value);
+                }
+            }
+
+            const resolvedSubject = input.subject ?? subject;
+            return resolvedSubject !== undefined
+                ? { body, subject: resolvedSubject }
+                : { body };
+        }
+
+        return input.subject !== undefined
+            ? { body: input.body, subject: input.subject }
+            : { body: input.body };
+    }
+
+    private checkChannel(channel: NotificationChannel): void {
+        const state = this.channelStates.get(channel);
+        if (state === undefined || !state.config.enabled) {
+            throw new ChannelDisabledError({ context: { channel } });
+        }
+    }
+
+    private checkRateLimit(channel: NotificationChannel): void {
+        const state = this.channelStates.get(channel);
+        if (state === undefined || state.config.rateLimit === undefined) return;
+
+        const now = this.clock();
+        const windowMs = 60_000;
+
+        if (now - state.windowStart > windowMs) {
+            state.sentCount = 0;
+            state.windowStart = now;
+        }
+
+        if (state.sentCount >= state.config.rateLimit) {
+            throw new RateLimitExceededError({
+                context: { channel, scope: "router" },
+            });
+        }
+    }
+
+    private incrementRateCounter(channel: NotificationChannel): void {
+        // `checkChannel` already proved `state` is non-undefined; cast
+        // rather than guard so coverage does not see an unreachable
+        // branch.
+        const state = this.channelStates.get(channel) as ChannelState;
+        state.sentCount++;
+    }
+}

packages/communication/messaging/notification-channel/src/scheduler/notification-scheduler.md

@@ -0,0 +1,64 @@
+# `notification-scheduler` — Future-delivery scheduler
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`notification-scheduler.ts` ships the `NotificationScheduler` class for scheduling notifications for future delivery. The scheduler does NOT call the router itself — callers register an `onDue(handler)` that receives the original `NotificationInput`, typically wiring it back into `NotificationRouter.send` or `enqueue`. The class exposes both manual `processDue()` (call from cron / queue worker) and `start()`/`stop()` for in-process polling.
+
+## Features
+
+- `schedule(input, deliverAt)` returns a stable id.
+- `cancel(id)`, `get(id)`, `listPending()`, `getDue(now?)` for inspection.
+- `processDue()` awaits the handler per entry and removes processed entries.
+- `start()`/`stop()` polling driver with idempotent semantics.
+- Injectable `Clock` for deterministic tests.
+- Throws `NotificationNotFoundError` for unknown ids on `cancel` / `get`.
+
+## Usage: Basic
+
+```ts
+import {
+    NotificationRouter,
+    NotificationScheduler,
+} from "@suaveplan/notification-channel";
+
+const router = new NotificationRouter({ channels, defaultChannel: "email" });
+const scheduler = new NotificationScheduler();
+scheduler.onDue(async (input) => {
+    await router.send(input);
+});
+scheduler.schedule({ recipient: "u@x", body: "Reminder" }, new Date(Date.now() + 60_000));
+scheduler.start();
+```
+
+## Usage: Advanced
+
+```ts
+const scheduler = new NotificationScheduler(5_000, () => clock.now());
+scheduler.onDue(async (input) => {
+    try {
+        await router.send(input);
+    } catch (err) {
+        await failureQueue.push({ input, err });
+    }
+});
+
+// Hook into a cron worker instead of in-process polling:
+cron.schedule("* * * * *", () => {
+    void scheduler.processDue();
+});
+```
+
+## API Reference
+
+- `NotificationScheduler(checkIntervalMs?, clock?)` — constructor.
+- `schedule(input, deliverAt)`, `cancel(id)`, `get(id)`, `listPending()`, `getDue(now?)`, `processDue()`, `start()`, `stop()`, `size`.
+- `ScheduledNotification` — `{ id, input, scheduledFor, createdAt, cancelled }`.
+- `ScheduleHandler` — `(input: NotificationInput) => Promise<void>`.
+
+## Implementation Notes
+
+`start()` is idempotent — calling twice has no effect; the second call is dropped before `setInterval` runs. `stop()` is idempotent — calling twice is safe and a leading call before `start()` is a no-op. `processDue()` is the single place that mutates the schedule map — both the polling driver and manual / cron callers use it, so behaviour is identical regardless of how processing is triggered. The scheduler does not persist across process restarts — production deployments should layer their own durable store atop `schedule`/`cancel` (e.g. snapshot `listPending()` to disk on shutdown, restore on boot via additional `schedule` calls).

packages/communication/messaging/notification-channel/src/scheduler/notification-scheduler.test.ts

@@ -0,0 +1,219 @@
+import { afterEach, describe, expect, it } from "@suaveplan/testing/runner";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import { NotificationScheduler } from "./notification-scheduler.js";
+
+describe("NotificationScheduler", () => {
+    let scheduler: NotificationScheduler | undefined;
+
+    afterEach(() => {
+        scheduler?.stop();
+    });
+
+    describe("schedule", () => {
+        it("schedules a notification for future delivery", {
+            timeout: 5000,
+        }, () => {
+            scheduler = new NotificationScheduler();
+            const future = new Date(Date.now() + 60_000);
+            const entry = scheduler.schedule(
+                { recipient: "user@test.com", body: "Hello" },
+                future
+            );
+            expect(entry.id).toMatch(/^sched_/);
+            expect(entry.scheduledFor).toBe(future.getTime());
+            expect(entry.cancelled).toBe(false);
+        });
+
+        it("assigns unique ids", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const future = new Date(Date.now() + 60_000);
+            const e1 = scheduler.schedule(
+                { recipient: "a", body: "A" },
+                future
+            );
+            const e2 = scheduler.schedule(
+                { recipient: "b", body: "B" },
+                future
+            );
+            expect(e1.id).not.toBe(e2.id);
+        });
+
+        it("tracks size", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const future = new Date(Date.now() + 60_000);
+            scheduler.schedule({ recipient: "a", body: "A" }, future);
+            scheduler.schedule({ recipient: "b", body: "B" }, future);
+            expect(scheduler.size).toBe(2);
+        });
+    });
+
+    describe("cancel", () => {
+        it("cancels a scheduled notification", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const entry = scheduler.schedule(
+                { recipient: "a", body: "A" },
+                new Date(Date.now() + 60_000)
+            );
+            const cancelled = scheduler.cancel(entry.id);
+            expect(cancelled.cancelled).toBe(true);
+        });
+
+        it("throws for non-existent id", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            expect(() => scheduler?.cancel("fake")).toThrow(
+                NotificationChannelError
+            );
+        });
+    });
+
+    describe("get", () => {
+        it("retrieves a scheduled notification", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const entry = scheduler.schedule(
+                { recipient: "a", body: "A" },
+                new Date(Date.now() + 60_000)
+            );
+            const retrieved = scheduler.get(entry.id);
+            expect(retrieved.id).toBe(entry.id);
+        });
+
+        it("throws for non-existent id", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            expect(() => scheduler?.get("fake")).toThrow(
+                NotificationChannelError
+            );
+        });
+    });
+
+    describe("listPending", () => {
+        it("returns non-cancelled entries", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const future = new Date(Date.now() + 60_000);
+            scheduler.schedule({ recipient: "a", body: "A" }, future);
+            const e2 = scheduler.schedule(
+                { recipient: "b", body: "B" },
+                future
+            );
+            scheduler.cancel(e2.id);
+            const pending = scheduler.listPending();
+            expect(pending).toHaveLength(1);
+        });
+
+        it("returns empty array when none pending", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            expect(scheduler.listPending()).toHaveLength(0);
+        });
+    });
+
+    describe("getDue", () => {
+        it("returns entries scheduled before now", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const past = new Date(Date.now() - 1_000);
+            const future = new Date(Date.now() + 60_000);
+            scheduler.schedule({ recipient: "a", body: "Past" }, past);
+            scheduler.schedule({ recipient: "b", body: "Future" }, future);
+            const due = scheduler.getDue();
+            expect(due).toHaveLength(1);
+            expect(due[0]?.input.body).toBe("Past");
+        });
+
+        it("excludes cancelled entries", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const past = new Date(Date.now() - 1_000);
+            const entry = scheduler.schedule(
+                { recipient: "a", body: "A" },
+                past
+            );
+            scheduler.cancel(entry.id);
+            expect(scheduler.getDue()).toHaveLength(0);
+        });
+
+        it("accepts custom time for testing", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            const target = Date.now() + 5_000;
+            scheduler.schedule(
+                { recipient: "a", body: "A" },
+                new Date(target - 1)
+            );
+            expect(scheduler.getDue(target)).toHaveLength(1);
+            expect(scheduler.getDue(target - 2)).toHaveLength(0);
+        });
+    });
+
+    describe("processDue", () => {
+        it("processes due notifications and removes them", {
+            timeout: 5000,
+        }, async () => {
+            scheduler = new NotificationScheduler();
+            const past = new Date(Date.now() - 1_000);
+            const processed: string[] = [];
+            scheduler.onDue(async (input) => {
+                processed.push(input.body);
+            });
+            scheduler.schedule({ recipient: "a", body: "Due1" }, past);
+            scheduler.schedule({ recipient: "b", body: "Due2" }, past);
+            const count = await scheduler.processDue();
+            expect(count).toBe(2);
+            expect(processed).toEqual(["Due1", "Due2"]);
+            expect(scheduler.size).toBe(0);
+        });
+
+        it("does not process future notifications", {
+            timeout: 5000,
+        }, async () => {
+            scheduler = new NotificationScheduler();
+            const future = new Date(Date.now() + 60_000);
+            scheduler.onDue(async () => {
+                /* noop */
+            });
+            scheduler.schedule({ recipient: "a", body: "Future" }, future);
+            const count = await scheduler.processDue();
+            expect(count).toBe(0);
+            expect(scheduler.size).toBe(1);
+        });
+
+        it("works without a handler (drops due entries)", {
+            timeout: 5000,
+        }, async () => {
+            scheduler = new NotificationScheduler();
+            const past = new Date(Date.now() - 1_000);
+            scheduler.schedule({ recipient: "a", body: "A" }, past);
+            const count = await scheduler.processDue();
+            expect(count).toBe(0);
+            expect(scheduler.size).toBe(0);
+        });
+    });
+
+    describe("start/stop", () => {
+        it("start is idempotent", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler(10_000);
+            scheduler.start();
+            scheduler.start();
+            scheduler.stop();
+        });
+
+        it("stop is idempotent", { timeout: 5000 }, () => {
+            scheduler = new NotificationScheduler();
+            scheduler.stop();
+            scheduler.stop();
+        });
+
+        it("start triggers interval-based processing", {
+            timeout: 5000,
+        }, async () => {
+            // Use a tiny interval and a past-due entry; the interval tick
+            // is what we care about — the entry is removed after one tick.
+            scheduler = new NotificationScheduler(1);
+            scheduler.schedule(
+                { recipient: "a", body: "A" },
+                new Date(Date.now() - 1)
+            );
+            scheduler.onDue(async () => {
+                /* noop */
+            });
+            scheduler.start();
+            await new Promise((r) => setTimeout(r, 25));
+            expect(scheduler.size).toBe(0);
+        });
+    });
+});

packages/communication/messaging/notification-channel/src/scheduler/notification-scheduler.ts

@@ -0,0 +1,132 @@
+import type { Clock } from "@suaveplan/types";
+import { NotificationNotFoundError } from "../error-codes/error-codes.js";
+import type { NotificationInput } from "../types/notification.types.js";
+
+/** A scheduled notification entry. */
+export interface ScheduledNotification {
+    readonly id: string;
+    readonly input: NotificationInput;
+    readonly scheduledFor: number;
+    readonly createdAt: string;
+    cancelled: boolean;
+}
+
+/** Callback invoked when a scheduled notification is due. */
+export type ScheduleHandler = (input: NotificationInput) => Promise<void>;
+
+const defaultClock: Clock = () => Date.now();
+
+/**
+ * Schedules notifications for future delivery. The scheduler does not
+ * fire the actual send — callers register an `onDue` handler that
+ * receives the original `NotificationInput`, typically wiring it back
+ * into `NotificationRouter.send` or `enqueue`.
+ */
+export class NotificationScheduler {
+    private readonly scheduled = new Map<string, ScheduledNotification>();
+    private nextId = 1;
+    private handler?: ScheduleHandler;
+    private intervalId: ReturnType<typeof setInterval> | undefined = undefined;
+    private readonly checkIntervalMs: number;
+    private readonly clock: Clock;
+
+    public constructor(checkIntervalMs = 1_000, clock: Clock = defaultClock) {
+        this.checkIntervalMs = checkIntervalMs;
+        this.clock = clock;
+    }
+
+    /** Register the handler invoked for each due entry. */
+    public onDue(handler: ScheduleHandler): void {
+        this.handler = handler;
+    }
+
+    /** Schedule a notification for future delivery. */
+    public schedule(
+        input: NotificationInput,
+        deliverAt: Date
+    ): ScheduledNotification {
+        const id = `sched_${this.nextId++}`;
+        const entry: ScheduledNotification = {
+            id,
+            input,
+            scheduledFor: deliverAt.getTime(),
+            createdAt: new Date(this.clock()).toISOString(),
+            cancelled: false,
+        };
+        this.scheduled.set(id, entry);
+        return entry;
+    }
+
+    /** Cancel a scheduled notification (throws when id is unknown). */
+    public cancel(id: string): ScheduledNotification {
+        const entry = this.scheduled.get(id);
+        if (entry === undefined) {
+            throw new NotificationNotFoundError({
+                context: { notificationId: id },
+            });
+        }
+        entry.cancelled = true;
+        return entry;
+    }
+
+    /** Retrieve a scheduled notification (throws when id is unknown). */
+    public get(id: string): ScheduledNotification {
+        const entry = this.scheduled.get(id);
+        if (entry === undefined) {
+            throw new NotificationNotFoundError({
+                context: { notificationId: id },
+            });
+        }
+        return entry;
+    }
+
+    /** List every pending (non-cancelled) scheduled notification. */
+    public listPending(): ScheduledNotification[] {
+        return [...this.scheduled.values()].filter((e) => !e.cancelled);
+    }
+
+    /** Notifications whose `scheduledFor <= now`. */
+    public getDue(now?: number): ScheduledNotification[] {
+        const currentTime = now ?? this.clock();
+        return [...this.scheduled.values()].filter(
+            (e) => !e.cancelled && e.scheduledFor <= currentTime
+        );
+    }
+
+    /** Process every due entry through the handler and remove them. */
+    public async processDue(): Promise<number> {
+        const due = this.getDue();
+        let processed = 0;
+
+        for (const entry of due) {
+            if (this.handler !== undefined && !entry.cancelled) {
+                await this.handler(entry.input);
+                processed++;
+            }
+            this.scheduled.delete(entry.id);
+        }
+
+        return processed;
+    }
+
+    /** Start automatic interval-based processing. */
+    public start(): void {
+        if (this.intervalId !== undefined) return;
+        this.intervalId = setInterval(() => {
+            void this.processDue();
+        }, this.checkIntervalMs);
+    }
+
+    /** Stop automatic processing (idempotent). */
+    public stop(): void {
+        if (this.intervalId !== undefined) {
+            clearInterval(this.intervalId);
+            this.intervalId = undefined;
+        }
+    }
+
+    /** Total number of scheduled (including cancelled) entries. */
+    public get size(): number {
+        return this.scheduled.size;
+    }
+}

packages/communication/messaging/notification-channel/src/schemas/schemas.md

@@ -0,0 +1,49 @@
+# `schemas` — Zod schemas at every public boundary
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`schemas.ts` exposes a Zod schema for every public option bundle in the package so callers can validate untrusted input before passing it into a constructor or public method. The `NotificationRouter` constructor calls `NotificationRouterConfigSchema.parse(...)` at the boundary; other classes leave validation as an opt-in for the caller because validating on every send is wasteful — the consumer chooses when to enforce.
+
+## Features
+
+- Schemas for every channel config, every public bundle, and every enum: `NotificationChannelSchema`, `NotificationPrioritySchema`, `NotificationStatusSchema`, `RateLimitRuleSchema`, `ChannelConfigSchema`, `RoutingRuleSchema`, `NotificationTemplateSchema`, `TemplateRegistrationSchema`, `NotificationInputSchema`, `NotificationRouterConfigSchema`, `EmailChannelConfigSchema`, `SmsChannelConfigSchema`, `VapidKeysSchema`, `PushChannelConfigSchema`, `WebhookChannelConfigSchema`, `DigestChannelConfigSchema`, `RetryConfigSchema`, `QuietHoursConfigSchema`, `StoredPreferencesSchema`, `PreferenceManagerOptionsSchema`.
+- Function-valued fields (`sendFn`, `getSubscriptions`, `fetchFn`, `condition`, `formatDigest`, `store`, `clock`) are typed as `z.unknown()` — Zod cannot introspect callables, and the TypeScript surface is the source of truth for shapes.
+- Boundary defaults are NOT injected — schemas validate shape only, defaults live in the consuming classes.
+
+## Usage: Basic
+
+```ts
+import { NotificationInputSchema } from "@suaveplan/notification-channel";
+
+const input = NotificationInputSchema.parse(req.body);
+await router.send(input);
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    NotificationRouterConfigSchema,
+    StoredPreferencesSchema,
+} from "@suaveplan/notification-channel";
+
+// Validate config loaded from a YAML file:
+const cfg = NotificationRouterConfigSchema.parse(yaml.parse(text));
+const router = new NotificationRouter(cfg);
+
+// Validate stored prefs at the persistence boundary:
+const safe = StoredPreferencesSchema.parse(row);
+await store.set(safe.userId, safe);
+```
+
+## API Reference
+
+Each named export is a `z.ZodType`. Use `.parse(value)` to validate-or-throw, `.safeParse(value)` to validate-or-result. The schemas describe shape only — runtime behaviour, defaults, and engine-pluggable callables remain owned by the consuming classes.
+
+## Implementation Notes
+
+`exactOptionalPropertyTypes: true` in `tsconfig.base.json` makes Zod's `.optional()` behave correctly: an explicit `undefined` value is rejected when the field is absent in the input record, but is accepted on output because the consumer might spread defaults. We use `z.record(z.string(), z.unknown())` for `metadata`-style fields because notification metadata is genuinely free-form. The `RoutingRule.condition` and every `sendFn` / `fetchFn` are `z.unknown()` so YAML-loaded configs (which cannot carry callables) parse cleanly — TypeScript will still complain at the call site if the values are not callable.

packages/communication/messaging/notification-channel/src/schemas/schemas.test.ts

@@ -0,0 +1,158 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    ChannelConfigSchema,
+    DigestChannelConfigSchema,
+    EmailChannelConfigSchema,
+    NotificationChannelSchema,
+    NotificationInputSchema,
+    NotificationPrioritySchema,
+    NotificationRouterConfigSchema,
+    NotificationStatusSchema,
+    NotificationTemplateSchema,
+    PreferenceManagerOptionsSchema,
+    PushChannelConfigSchema,
+    QuietHoursConfigSchema,
+    RateLimitRuleSchema,
+    RetryConfigSchema,
+    RoutingRuleSchema,
+    SmsChannelConfigSchema,
+    StoredPreferencesSchema,
+    TemplateRegistrationSchema,
+    VapidKeysSchema,
+    WebhookChannelConfigSchema,
+} from "./schemas.js";
+
+describe("schemas", () => {
+    it("every public option schema parses a real example", {
+        timeout: 5000,
+    }, () => {
+        expect(NotificationChannelSchema.parse("email")).toBe("email");
+        expect(NotificationPrioritySchema.parse("urgent")).toBe("urgent");
+        expect(NotificationStatusSchema.parse("sent")).toBe("sent");
+        expect(
+            RateLimitRuleSchema.parse({ maxCount: 5, windowMs: 60_000 })
+        ).toEqual({ maxCount: 5, windowMs: 60_000 });
+        expect(
+            ChannelConfigSchema.parse({
+                channel: "email",
+                enabled: true,
+                rateLimit: 10,
+            })
+        ).toMatchObject({ channel: "email", enabled: true, rateLimit: 10 });
+        expect(
+            RoutingRuleSchema.parse({
+                id: "r1",
+                name: "n",
+                channels: ["email"],
+            })
+        ).toMatchObject({ id: "r1", name: "n" });
+        expect(
+            NotificationTemplateSchema.parse({
+                id: "t1",
+                name: "n",
+                channel: "email",
+                bodyTemplate: "Hi {{x}}",
+                defaultPriority: "normal",
+            })
+        ).toMatchObject({ id: "t1", defaultPriority: "normal" });
+        expect(
+            TemplateRegistrationSchema.parse({
+                id: "t1",
+                name: "n",
+                defaultTemplate: { bodyTemplate: "Body" },
+            })
+        ).toMatchObject({ id: "t1" });
+        expect(
+            NotificationInputSchema.parse({
+                recipient: "a@b.c",
+                body: "Hi",
+            })
+        ).toMatchObject({ recipient: "a@b.c" });
+        expect(
+            NotificationRouterConfigSchema.parse({
+                channels: [{ channel: "email", enabled: true }],
+                defaultChannel: "email",
+            })
+        ).toMatchObject({ defaultChannel: "email" });
+        expect(
+            EmailChannelConfigSchema.parse({
+                from: "from@example.com",
+                sendFn: () => undefined,
+            })
+        ).toMatchObject({ from: "from@example.com" });
+        expect(
+            SmsChannelConfigSchema.parse({
+                from: "+1",
+                sendFn: () => undefined,
+            })
+        ).toMatchObject({ from: "+1" });
+        expect(
+            VapidKeysSchema.parse({
+                publicKey: "p",
+                privateKey: "k",
+                subject: "mailto:a@b.c",
+            })
+        ).toMatchObject({ publicKey: "p" });
+        expect(
+            PushChannelConfigSchema.parse({
+                vapid: {
+                    publicKey: "p",
+                    privateKey: "k",
+                    subject: "mailto:a@b.c",
+                },
+                getSubscriptions: () => undefined,
+            })
+        ).toMatchObject({});
+        expect(WebhookChannelConfigSchema.parse({})).toEqual({});
+        expect(DigestChannelConfigSchema.parse({ delegate: {} })).toMatchObject(
+            {}
+        );
+        expect(
+            RetryConfigSchema.parse({ maxRetries: 1, baseDelayMs: 100 })
+        ).toMatchObject({ maxRetries: 1 });
+        expect(
+            QuietHoursConfigSchema.parse({ startHour: 22, endHour: 7 })
+        ).toMatchObject({ startHour: 22 });
+        expect(
+            StoredPreferencesSchema.parse({
+                userId: "u",
+                enabledChannels: ["email"],
+                disabledChannels: [],
+            })
+        ).toMatchObject({ userId: "u" });
+        expect(
+            PreferenceManagerOptionsSchema.parse({ store: {} })
+        ).toMatchObject({});
+    });
+
+    it("router config schema rejects malformed channels", {
+        timeout: 5000,
+    }, () => {
+        expect(() =>
+            NotificationRouterConfigSchema.parse({
+                channels: "not-an-array",
+                defaultChannel: "email",
+            })
+        ).toThrow();
+        expect(() =>
+            NotificationRouterConfigSchema.parse({
+                channels: [{ channel: "email", enabled: true }],
+                defaultChannel: "carrier-pigeon",
+            })
+        ).toThrow();
+    });
+
+    it("input schema rejects empty recipient", { timeout: 5000 }, () => {
+        expect(() =>
+            NotificationInputSchema.parse({ recipient: "", body: "x" })
+        ).toThrow();
+    });
+
+    it("quiet-hours schema rejects out-of-range hours", {
+        timeout: 5000,
+    }, () => {
+        expect(() =>
+            QuietHoursConfigSchema.parse({ startHour: 25, endHour: 7 })
+        ).toThrow();
+    });
+});

packages/communication/messaging/notification-channel/src/schemas/schemas.ts

@@ -0,0 +1,177 @@
+import z from "zod";
+
+/**
+ * Zod schemas for every public option bundle. Callers may invoke
+ * `.parse(...)` to validate untrusted input before passing it into
+ * any constructor or public method.
+ *
+ * The schemas describe shape only — function-valued fields like
+ * `sendFn`, `fetchFn`, `condition`, and `getSubscriptions` are typed
+ * as `z.unknown()` so Zod does not attempt to introspect callable
+ * values; the TypeScript surface remains the source of truth for
+ * callable shapes.
+ */
+
+export const NotificationChannelSchema = z.enum([
+    "email",
+    "sms",
+    "push",
+    "in_app",
+    "webhook",
+]);
+
+export const NotificationPrioritySchema = z.enum([
+    "low",
+    "normal",
+    "high",
+    "urgent",
+]);
+
+export const NotificationStatusSchema = z.enum([
+    "pending",
+    "sending",
+    "sent",
+    "delivered",
+    "failed",
+    "cancelled",
+]);
+
+export const RateLimitRuleSchema = z.object({
+    maxCount: z.number().int().nonnegative(),
+    windowMs: z.number().int().positive(),
+});
+
+export const ChannelConfigSchema = z.object({
+    channel: NotificationChannelSchema,
+    enabled: z.boolean(),
+    rateLimit: z.number().int().nonnegative().optional(),
+    retryPolicy: z
+        .object({
+            maxRetries: z.number().int().nonnegative(),
+            backoffMs: z.number().int().nonnegative(),
+        })
+        .optional(),
+});
+
+export const RoutingRuleSchema = z.object({
+    id: z.string().min(1),
+    name: z.string().min(1),
+    channels: z.array(NotificationChannelSchema),
+    priority: NotificationPrioritySchema.optional(),
+    condition: z.unknown().optional(),
+});
+
+export const NotificationTemplateSchema = z.object({
+    id: z.string().min(1),
+    name: z.string().min(1),
+    channel: NotificationChannelSchema,
+    subject: z.string().optional(),
+    bodyTemplate: z.string(),
+    defaultPriority: NotificationPrioritySchema,
+});
+
+export const TemplateRegistrationSchema = z.object({
+    id: z.string().min(1),
+    name: z.string().min(1),
+    defaultTemplate: z.object({
+        subject: z.string().optional(),
+        bodyTemplate: z.string(),
+    }),
+    channelTemplates: z
+        .record(
+            NotificationChannelSchema,
+            z.object({
+                subject: z.string().optional(),
+                bodyTemplate: z.string(),
+            })
+        )
+        .optional(),
+});
+
+export const NotificationInputSchema = z.object({
+    recipient: z.string().min(1),
+    channel: NotificationChannelSchema.optional(),
+    subject: z.string().optional(),
+    body: z.string(),
+    priority: NotificationPrioritySchema.optional(),
+    templateId: z.string().optional(),
+    templateData: z.record(z.string(), z.string()).optional(),
+    metadata: z.record(z.string(), z.unknown()).optional(),
+});
+
+export const NotificationRouterConfigSchema = z.object({
+    channels: z.array(ChannelConfigSchema),
+    templates: z.array(NotificationTemplateSchema).optional(),
+    routingRules: z.array(RoutingRuleSchema).optional(),
+    defaultChannel: NotificationChannelSchema,
+    deliveryChannels: z.array(z.unknown()).optional(),
+    clock: z.unknown().optional(),
+});
+
+export const EmailChannelConfigSchema = z.object({
+    from: z.string().min(1),
+    sendFn: z.unknown(),
+    clock: z.unknown().optional(),
+});
+
+export const SmsChannelConfigSchema = z.object({
+    from: z.string().min(1),
+    sendFn: z.unknown(),
+    clock: z.unknown().optional(),
+});
+
+export const VapidKeysSchema = z.object({
+    publicKey: z.string().min(1),
+    privateKey: z.string().min(1),
+    subject: z.string().min(1),
+});
+
+export const PushChannelConfigSchema = z.object({
+    vapid: VapidKeysSchema,
+    getSubscriptions: z.unknown(),
+    sendFn: z.unknown().optional(),
+    fetchFn: z.unknown().optional(),
+    ttl: z.number().int().positive().optional(),
+    clock: z.unknown().optional(),
+});
+
+export const WebhookChannelConfigSchema = z.object({
+    headers: z.record(z.string(), z.string()).optional(),
+    fetchFn: z.unknown().optional(),
+    timeoutMs: z.number().int().positive().optional(),
+    clock: z.unknown().optional(),
+});
+
+export const DigestChannelConfigSchema = z.object({
+    delegate: z.unknown(),
+    intervalMs: z.number().int().nonnegative().optional(),
+    maxPerDigest: z.number().int().positive().optional(),
+    formatDigest: z.unknown().optional(),
+    clock: z.unknown().optional(),
+});
+
+export const RetryConfigSchema = z.object({
+    maxRetries: z.number().int().nonnegative(),
+    baseDelayMs: z.number().int().nonnegative(),
+    maxDelayMs: z.number().int().positive().optional(),
+});
+
+export const QuietHoursConfigSchema = z.object({
+    startHour: z.number().int().min(0).max(23),
+    endHour: z.number().int().min(0).max(23),
+    days: z.array(z.number().int().min(0).max(6)).optional(),
+});
+
+export const StoredPreferencesSchema = z.object({
+    userId: z.string().min(1),
+    enabledChannels: z.array(NotificationChannelSchema),
+    disabledChannels: z.array(NotificationChannelSchema),
+    quietHours: QuietHoursConfigSchema.optional(),
+    urgentThreshold: NotificationPrioritySchema.optional(),
+});
+
+export const PreferenceManagerOptionsSchema = z.object({
+    store: z.unknown(),
+    defaultChannels: z.array(NotificationChannelSchema).optional(),
+    clock: z.unknown().optional(),
+});

packages/communication/messaging/notification-channel/src/templates/template-engine.md

@@ -0,0 +1,80 @@
+# `template-engine` — Template registry and renderer
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`template-engine.ts` ships the `TemplateEngine` registry that turns named templates into channel-specific rendered output. Templates carry a `defaultTemplate` (used when no channel variant matches) plus optional `channelTemplates` keyed by `NotificationChannel`, with `{{var}}` placeholders substituted from a flat `Record<string,string>`. Missing keys are left as-is so QA can spot them.
+
+## Features
+
+- Register / unregister / list templates by string id.
+- Per-channel variants (`channelTemplates.email`, `.sms`, etc.) with fallback to `defaultTemplate`.
+- `{{var}}` placeholder substitution against a flat string-valued record.
+- Throws `TemplateNotFoundError` for unknown ids — no silent empty renders.
+- Universal — no DOM/Node-specific APIs.
+
+## Usage: Basic
+
+```ts
+import { TemplateEngine } from "@suaveplan/notification-channel";
+
+const engine = new TemplateEngine();
+engine.register({
+    id: "welcome",
+    name: "Welcome",
+    defaultTemplate: {
+        subject: "Welcome {{name}}",
+        bodyTemplate: "Hello {{name}}, welcome to {{app}}!",
+    },
+});
+
+const rendered = engine.render("welcome", { name: "Alice", app: "Suaveplan" });
+```
+
+## Usage: Advanced
+
+```ts
+engine.register({
+    id: "order-status",
+    name: "Order status",
+    defaultTemplate: {
+        subject: "Order {{orderId}} — {{status}}",
+        bodyTemplate: "Order #{{orderId}}: {{status}}",
+    },
+    channelTemplates: {
+        sms: { bodyTemplate: "Order {{orderId}}: {{status}}" },
+        email: {
+            subject: "Order {{orderId}} update",
+            bodyTemplate: "<h1>Order {{orderId}}</h1><p>{{status}}</p>",
+        },
+    },
+});
+
+const sms = engine.render(
+    "order-status",
+    { orderId: "12345", status: "shipped" },
+    "sms"
+);
+const email = engine.render(
+    "order-status",
+    { orderId: "12345", status: "shipped" },
+    "email"
+);
+```
+
+## API Reference
+
+- `TemplateEngine` class.
+  - `register(t: TemplateRegistration): void`
+  - `unregister(id: string): boolean`
+  - `has(id: string): boolean`
+  - `listIds(): string[]`
+  - `render(id, data?, channel?): RenderedTemplate`
+- `TemplateRegistration`, `ChannelTemplateBody`, `ChannelTemplate`, `RenderedTemplate`.
+
+## Implementation Notes
+
+Substitution uses `String.prototype.split(...).join(...)` rather than `replace(/.../g, ...)` so dollar-escape sequences in the value (`$&`, `$1`) flow through verbatim. Subjects flow through the same substitution pass when set. Unknown placeholders are intentionally preserved — silently dropping them masks integration mismatches that QA would otherwise catch. The engine is intentionally simple: no conditionals, no loops, no template inheritance. Consumers needing those features should plug a real template language (Handlebars, Liquid, MJML) into a custom `TemplateEngine` decorator or render upstream.

packages/communication/messaging/notification-channel/src/templates/template-engine.test.ts

@@ -0,0 +1,180 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { NotificationChannelError } from "../error-codes/error-codes.js";
+import { TemplateEngine } from "./template-engine.js";
+
+describe("TemplateEngine", () => {
+    describe("register and lookup", () => {
+        it("registers a template", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Welcome",
+                defaultTemplate: { bodyTemplate: "Hello {{name}}" },
+            });
+            expect(engine.has("tpl_1")).toBe(true);
+        });
+
+        it("reports false for unregistered template", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            expect(engine.has("nonexistent")).toBe(false);
+        });
+
+        it("lists registered template ids", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "A",
+                defaultTemplate: { bodyTemplate: "A" },
+            });
+            engine.register({
+                id: "tpl_2",
+                name: "B",
+                defaultTemplate: { bodyTemplate: "B" },
+            });
+            expect(engine.listIds()).toEqual(["tpl_1", "tpl_2"]);
+        });
+
+        it("unregisters a template", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "A",
+                defaultTemplate: { bodyTemplate: "A" },
+            });
+            expect(engine.unregister("tpl_1")).toBe(true);
+            expect(engine.has("tpl_1")).toBe(false);
+        });
+
+        it("returns false when unregistering non-existent", {
+            timeout: 5000,
+        }, () => {
+            const engine = new TemplateEngine();
+            expect(engine.unregister("fake")).toBe(false);
+        });
+    });
+
+    describe("render", () => {
+        it("renders with variable substitution", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Greet",
+                defaultTemplate: {
+                    subject: "Hello {{name}}",
+                    bodyTemplate: "Welcome, {{name}}! Your code is {{code}}.",
+                },
+            });
+            const result = engine.render("tpl_1", {
+                name: "Alice",
+                code: "1234",
+            });
+            expect(result.body).toBe("Welcome, Alice! Your code is 1234.");
+            expect(result.subject).toBe("Hello Alice");
+        });
+
+        it("renders without data", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Static",
+                defaultTemplate: { bodyTemplate: "No variables here" },
+            });
+            const result = engine.render("tpl_1");
+            expect(result.body).toBe("No variables here");
+        });
+
+        it("throws for non-existent template", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            expect(() => engine.render("fake")).toThrow(
+                NotificationChannelError
+            );
+        });
+
+        it("leaves unreplaced variables intact", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Partial",
+                defaultTemplate: {
+                    bodyTemplate: "Hi {{name}}, code: {{code}}",
+                },
+            });
+            const result = engine.render("tpl_1", { name: "Bob" });
+            expect(result.body).toBe("Hi Bob, code: {{code}}");
+        });
+
+        it("returns undefined subject when not set", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "NoSubject",
+                defaultTemplate: { bodyTemplate: "Body only" },
+            });
+            const result = engine.render("tpl_1");
+            expect(result.subject).toBeUndefined();
+        });
+    });
+
+    describe("channel-specific templates", () => {
+        it("uses channel-specific template when available", {
+            timeout: 5000,
+        }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Multi",
+                defaultTemplate: {
+                    subject: "Default Subject",
+                    bodyTemplate: "Default body for {{name}}",
+                },
+                channelTemplates: {
+                    sms: { bodyTemplate: "SMS: Hi {{name}}" },
+                    email: {
+                        subject: "Email Subject for {{name}}",
+                        bodyTemplate: "<h1>Hello {{name}}</h1>",
+                    },
+                },
+            });
+
+            const smsResult = engine.render("tpl_1", { name: "Alice" }, "sms");
+            expect(smsResult.body).toBe("SMS: Hi Alice");
+            expect(smsResult.subject).toBeUndefined();
+
+            const emailResult = engine.render(
+                "tpl_1",
+                { name: "Alice" },
+                "email"
+            );
+            expect(emailResult.body).toBe("<h1>Hello Alice</h1>");
+            expect(emailResult.subject).toBe("Email Subject for Alice");
+        });
+
+        it("falls back to default when channel variant missing", {
+            timeout: 5000,
+        }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "Fallback",
+                defaultTemplate: { bodyTemplate: "Default body" },
+                channelTemplates: {
+                    email: { bodyTemplate: "Email body" },
+                },
+            });
+            const result = engine.render("tpl_1", undefined, "sms");
+            expect(result.body).toBe("Default body");
+        });
+
+        it("uses default when no channel specified", { timeout: 5000 }, () => {
+            const engine = new TemplateEngine();
+            engine.register({
+                id: "tpl_1",
+                name: "NoChannel",
+                defaultTemplate: { bodyTemplate: "Default" },
+                channelTemplates: { email: { bodyTemplate: "Email" } },
+            });
+            const result = engine.render("tpl_1");
+            expect(result.body).toBe("Default");
+        });
+    });
+});

packages/communication/messaging/notification-channel/src/templates/template-engine.ts

@@ -0,0 +1,104 @@
+import { TemplateNotFoundError } from "../error-codes/error-codes.js";
+import type { NotificationChannel } from "../types/notification.types.js";
+
+/** Channel-specific template variant. */
+export interface ChannelTemplateBody {
+    readonly subject?: string;
+    readonly bodyTemplate: string;
+}
+
+/** Template registration entry supporting channel-specific variants. */
+export interface TemplateRegistration {
+    readonly id: string;
+    readonly name: string;
+    /** Default template used when no channel-specific variant exists. */
+    readonly defaultTemplate: ChannelTemplateBody;
+    /** Channel-specific template overrides. */
+    readonly channelTemplates?: Partial<
+        Record<NotificationChannel, ChannelTemplateBody>
+    >;
+}
+
+/** A registered template projected for a specific channel. */
+export interface ChannelTemplate {
+    readonly id: string;
+    readonly name: string;
+    readonly subject?: string;
+    readonly bodyTemplate: string;
+    readonly channel?: NotificationChannel;
+}
+
+/** Result of rendering a template. */
+export interface RenderedTemplate {
+    readonly subject?: string;
+    readonly body: string;
+}
+
+/**
+ * Manages notification templates with `{{var}}` substitution and
+ * channel-specific variants. Variables that have no value in `data`
+ * are left intact so callers can detect missing substitutions during
+ * QA without the template silently producing nonsense.
+ */
+export class TemplateEngine {
+    private readonly templates = new Map<string, TemplateRegistration>();
+
+    /** Register a template (overrides any existing entry with the same id). */
+    public register(template: TemplateRegistration): void {
+        this.templates.set(template.id, template);
+    }
+
+    /** Remove a registered template. */
+    public unregister(id: string): boolean {
+        return this.templates.delete(id);
+    }
+
+    /** Check whether a template exists. */
+    public has(id: string): boolean {
+        return this.templates.has(id);
+    }
+
+    /** List every registered template id. */
+    public listIds(): string[] {
+        return [...this.templates.keys()];
+    }
+
+    /**
+     * Render a template with variable substitution. Uses the
+     * channel-specific variant when available, otherwise the default.
+     */
+    public render(
+        templateId: string,
+        data?: Readonly<Record<string, string>>,
+        channel?: NotificationChannel
+    ): RenderedTemplate {
+        const registration = this.templates.get(templateId);
+        if (registration === undefined) {
+            throw new TemplateNotFoundError({
+                context: { templateId },
+            });
+        }
+
+        const variantOverride =
+            channel !== undefined
+                ? registration.channelTemplates?.[channel]
+                : undefined;
+        const variant: ChannelTemplateBody =
+            variantOverride ?? registration.defaultTemplate;
+
+        let body = variant.bodyTemplate;
+        let subject = variant.subject;
+
+        if (data !== undefined) {
+            for (const [key, value] of Object.entries(data)) {
+                const pattern = `{{${key}}}`;
+                body = body.split(pattern).join(value);
+                if (subject !== undefined) {
+                    subject = subject.split(pattern).join(value);
+                }
+            }
+        }
+
+        return subject !== undefined ? { subject, body } : { body };
+    }
+}

packages/communication/messaging/notification-channel/src/types/notification.types.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { VALID_TRANSITIONS } from "./notification.types.js";
+
+describe("VALID_TRANSITIONS", () => {
+    it("allows pending to sending", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.pending).toContain("sending");
+    });
+
+    it("allows pending to cancelled", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.pending).toContain("cancelled");
+    });
+
+    it("allows sending to sent", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.sending).toContain("sent");
+    });
+
+    it("allows sending to failed", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.sending).toContain("failed");
+    });
+
+    it("allows sent to delivered", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.sent).toContain("delivered");
+    });
+
+    it("allows sent to failed (e.g. async bounce)", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.sent).toContain("failed");
+    });
+
+    it("has no transitions from delivered", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.delivered).toHaveLength(0);
+    });
+
+    it("has no transitions from failed", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.failed).toHaveLength(0);
+    });
+
+    it("has no transitions from cancelled", { timeout: 5000 }, () => {
+        expect(VALID_TRANSITIONS.cancelled).toHaveLength(0);
+    });
+
+    it("is frozen", { timeout: 5000 }, () => {
+        expect(Object.isFrozen(VALID_TRANSITIONS)).toBe(true);
+    });
+});

packages/communication/messaging/notification-channel/src/types/notification.types.ts

@@ -0,0 +1,109 @@
+/** Supported notification delivery channels. */
+export type NotificationChannel =
+    | "email"
+    | "sms"
+    | "push"
+    | "in_app"
+    | "webhook";
+
+/** Priority levels for notifications. */
+export type NotificationPriority = "low" | "normal" | "high" | "urgent";
+
+/** Notification delivery status. */
+export type NotificationStatus =
+    | "pending"
+    | "sending"
+    | "sent"
+    | "delivered"
+    | "failed"
+    | "cancelled";
+
+/** A notification record. */
+export interface Notification {
+    readonly id: string;
+    readonly channel: NotificationChannel;
+    readonly recipient: string;
+    readonly subject?: string;
+    readonly body: string;
+    readonly priority: NotificationPriority;
+    readonly status: NotificationStatus;
+    readonly metadata?: Record<string, unknown>;
+    readonly createdAt: string;
+    readonly sentAt?: string;
+    readonly deliveredAt?: string;
+}
+
+/** A notification template with variable substitution. */
+export interface NotificationTemplate {
+    readonly id: string;
+    readonly name: string;
+    readonly channel: NotificationChannel;
+    readonly subject?: string;
+    readonly bodyTemplate: string;
+    readonly defaultPriority: NotificationPriority;
+}
+
+/** Per-channel retry policy. */
+export interface ChannelRetryPolicy {
+    readonly maxRetries: number;
+    readonly backoffMs: number;
+}
+
+/** Channel configuration with rate limiting and retry policy. */
+export interface ChannelConfig {
+    readonly channel: NotificationChannel;
+    readonly enabled: boolean;
+    readonly rateLimit?: number;
+    readonly retryPolicy?: ChannelRetryPolicy;
+}
+
+/** A routing rule that directs notifications to channels. */
+export interface RoutingRule {
+    readonly id: string;
+    readonly name: string;
+    readonly channels: readonly NotificationChannel[];
+    readonly priority?: NotificationPriority;
+    readonly condition?: (recipient: string) => boolean;
+}
+
+/** Input for sending a notification. */
+export interface NotificationInput {
+    readonly recipient: string;
+    readonly channel?: NotificationChannel;
+    readonly subject?: string;
+    readonly body: string;
+    readonly priority?: NotificationPriority;
+    readonly templateId?: string;
+    readonly templateData?: Record<string, string>;
+    readonly metadata?: Record<string, unknown>;
+}
+
+/** Result of sending a notification. */
+export interface NotificationResult {
+    readonly id: string;
+    readonly channel: NotificationChannel;
+    readonly status: NotificationStatus;
+    readonly sentAt?: string;
+    readonly error?: string;
+}
+
+/** Bus event payloads emitted by the NotificationRouter. */
+export type NotificationEventMap = {
+    "notification.created": Notification;
+    "notification.sent": Notification;
+    "notification.delivered": Notification;
+    "notification.failed": Notification;
+    "notification.cancelled": Notification;
+} & Record<string, unknown>;
+
+/** Valid notification status transitions. */
+export const VALID_TRANSITIONS: Readonly<
+    Record<NotificationStatus, readonly NotificationStatus[]>
+> = Object.freeze({
+    pending: ["sending", "cancelled"],
+    sending: ["sent", "failed"],
+    sent: ["delivered", "failed"],
+    delivered: [],
+    failed: [],
+    cancelled: [],
+});

packages/communication/messaging/notification-channel/tests/setup/polyfills.ts

@@ -0,0 +1,38 @@
+/**
+ * Test-environment setup for @suaveplan/notification-channel.
+ *
+ * Wires a real in-memory OpenTelemetry `MeterProvider` BEFORE any source
+ * module loads so the meter resolved at module load is the real provider's
+ * meter (and not the no-op fallback). Tests that inspect emitted instruments
+ * read them out of `testInMemoryMetricExporter` via `flushTestMetrics()`.
+ *
+ * Universal: no `node:fs`, no `process.cwd()`, no DOM globals.
+ */
+import { metrics } from "@opentelemetry/api";
+import {
+    AggregationTemporality,
+    InMemoryMetricExporter,
+    MeterProvider,
+    PeriodicExportingMetricReader,
+} from "@opentelemetry/sdk-metrics";
+
+export const testInMemoryMetricExporter = new InMemoryMetricExporter(
+    AggregationTemporality.CUMULATIVE
+);
+
+const reader = new PeriodicExportingMetricReader({
+    exporter: testInMemoryMetricExporter,
+    exportIntervalMillis: 60_000,
+});
+
+export const testMeterProvider = new MeterProvider({ readers: [reader] });
+metrics.setGlobalMeterProvider(testMeterProvider);
+
+export async function flushTestMetrics(): Promise<
+    ReturnType<typeof testInMemoryMetricExporter.getMetrics>
+> {
+    await testMeterProvider.forceFlush();
+    const collected = testInMemoryMetricExporter.getMetrics();
+    testInMemoryMetricExporter.reset();
+    return collected;
+}

packages/communication/messaging/notification-channel/tsconfig.lib.json

@@ -0,0 +1,12 @@
+{
+    "$schema": "https://json.schemastore.org/tsconfig",
+    "extends": "../../../../tsconfig.base.json",
+    "compilerOptions": {
+        "rootDir": "./src",
+        "outDir": "./dist",
+        "lib": ["ES2022", "DOM"],
+        "types": ["node"]
+    },
+    "include": ["src/**/*.ts"],
+    "exclude": ["src/**/*.test.ts", "dist", "node_modules"]
+}

packages/communication/messaging/notification-channel/vite.config.ts

@@ -0,0 +1,38 @@
+import { defineConfig } from "vite";
+import dts from "vite-plugin-dts";
+
+export default defineConfig({
+    root: __dirname,
+    cacheDir: "../../../node_modules/.vite/packages/notification-channel",
+    plugins: [
+        dts({
+            entryRoot: "src",
+            tsconfigPath: "./tsconfig.lib.json",
+            insertTypesEntry: true,
+        }),
+    ],
+    build: {
+        outDir: "./dist",
+        emptyOutDir: true,
+        reportCompressedSize: true,
+        sourcemap: true,
+        lib: { entry: "src/index.ts", formats: ["es"] },
+        rollupOptions: {
+            treeshake: true,
+            output: {
+                preserveModules: true,
+                preserveModulesRoot: "src",
+                entryFileNames: "[name].js",
+            },
+            external: [
+                "@opentelemetry/api",
+                "@suaveplan/error",
+                "@suaveplan/events",
+                "@suaveplan/types",
+                "tslib",
+                "zod",
+                /^node:/,
+            ],
+        },
+    },
+});

packages/communication/messaging/notification-channel/vitest.config.ts

@@ -0,0 +1,31 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+    test: {
+        globals: false,
+        environment: "node",
+        pool: "forks",
+        setupFiles: ["./tests/setup/polyfills.ts"],
+        include: ["src/**/*.test.ts", "tests/**/*.test.ts"],
+        exclude: ["dist/**", "node_modules/**"],
+        coverage: {
+            provider: "istanbul",
+            reporter: ["text", "html", "lcov"],
+            include: ["src/**/*.ts"],
+            exclude: [
+                "src/**/*.test.ts",
+                "src/**/*.types.ts",
+                "src/**/index.ts",
+                "src/index.ts",
+                "tests/**",
+            ],
+            thresholds: {
+                statements: 100,
+                branches: 100,
+                functions: 100,
+                lines: 100,
+            },
+        },
+        testTimeout: 30000,
+    },
+});