Initial Commit

packages/api-stack/api/api-openapi/src/api-openapi.spec-conformance.test.ts

@@ -0,0 +1,80 @@
+import { z } from "@hono/zod-openapi";
+import { describe, expect, expectTypeOf, it } from "@suaveplan/testing/runner";
+import { OPENAPI_CODES, OpenAPIError } from "./error-codes/error-codes.js";
+import * as Barrel from "./index.js";
+import { POST, successResponse } from "./route-factory/route-factory.js";
+import { createSchemaRegistry } from "./schema-registry/schema-registry.js";
+
+describe("spec-conformance — every OPENAPI_* code is thrown from a production path", () => {
+    it("OPENAPI.SCHEMA_NOT_FOUND", { timeout: 5000 }, () => {
+        const reg = createSchemaRegistry();
+        let err: unknown;
+        try {
+            reg.extend("missing", "x", { k: z.string() });
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.SCHEMA_NOT_FOUND);
+    });
+
+    it("OPENAPI.INVALID_BASE_SCHEMA", { timeout: 5000 }, () => {
+        const reg = createSchemaRegistry();
+        reg.register("p", z.string());
+        let err: unknown;
+        try {
+            reg.partial("p", "x");
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.INVALID_BASE_SCHEMA
+        );
+    });
+
+    it("OPENAPI.INVALID_INPUT is thrown from definePluginRoutes boundary", {
+        timeout: 5000,
+    }, async () => {
+        const { definePluginRoutes } = await import(
+            "./plugin-integration/plugin-integration.js"
+        );
+        let err: unknown;
+        try {
+            definePluginRoutes(
+                [],
+                // Missing pluginName → INVALID_INPUT
+                { app: {}, registry: {} } as never
+            );
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.INVALID_INPUT);
+    });
+});
+
+describe("spec-conformance — no global singleton in the barrel", () => {
+    it("does not export getSchemaRegistry", { timeout: 5000 }, () => {
+        expect(Object.keys(Barrel)).not.toContain("getSchemaRegistry");
+    });
+
+    it("does not export globalSchemaRegistry", { timeout: 5000 }, () => {
+        expect(Object.keys(Barrel)).not.toContain("globalSchemaRegistry");
+    });
+});
+
+describe("spec-conformance — RouteBuilder end-to-end inference", () => {
+    it("threads body type to c.req.valid('json')", { timeout: 5000 }, () => {
+        const Body = z.object({ name: z.string() });
+        const Resp = z.object({ id: z.string() });
+        const r = POST("/users")
+            .body(Body)
+            .response(successResponse(Resp))
+            .build();
+
+        // Compile-time: r must carry the Body's Zod type through
+        // the TypedRouteConfig structural shape.
+        expectTypeOf(r.request).toMatchTypeOf<{
+            body: { content: { "application/json": { schema: typeof Body } } };
+        }>();
+    });
+});

packages/api-stack/api/api-openapi/src/emitter/emitter.md

@@ -0,0 +1,129 @@
+# emitter
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`createOpenapiEmitter` is the aggregator the spec calls for: it ingests
+every plugin's manifest, every registered route (with its Zod-converted
+schemas), the active auth adapter's security scheme, and the host
+config, then produces a single OpenAPI 3.1 document covering the entire
+mounted plugin set. The emitter is the single source of truth served at
+`/openapi.json` and consumed by the docs UI sibling packages.
+
+By centralising emission, the host eliminates drift: every plugin's
+routes flow through the same namespacing rules, the same strictness
+policy, and the same security inheritance. Plugins cannot hand-author
+OpenAPI fragments that disagree with what their Hono runtime actually
+serves.
+
+## Features
+
+- **Manifest-driven tags + components** — `displayName` becomes the tag,
+  `<pluginName>.<TypeName>` becomes the component schema prefix.
+- **Deterministic operationIds** — every route receives
+  `<plugin>.<method>.<oasPath>`. Collisions raise the moment they
+  appear.
+- **Security inheritance** — every operation lists the active auth
+  adapter's scheme except for routes listed in any plugin's
+  `publicRoutes`, which receive `security: []`.
+- **Strictness gate** — routes missing request + response schemas warn
+  (with an OTel counter) or refuse install, per `host.openapi.strictness`.
+- **Per-plugin filtered view** — `getDocumentForPlugin(name)` returns
+  only operations tagged with that plugin; misses raise
+  `OPENAPI.UNKNOWN_PLUGIN_IN_FILTER`.
+- **JSON + YAML serialisation** — `getJson()` / `getYaml()` produce
+  serialised bodies for the HTTP endpoints.
+- **OTel emission + conversion-error counters** — visibility on
+  document production and Zod→OAS conversion failures.
+- **Lifecycle dedup** — the constructed document is memoised; repeated
+  `getDocument()` calls return the same reference.
+
+## Usage: Basic
+
+```ts
+import { createOpenapiEmitter } from "@suaveplan/api-openapi/emitter";
+
+const emitter = createOpenapiEmitter({
+    manifests: [
+        { name: "billing", displayName: "Billing", description: "Invoices" },
+    ],
+    routes: [
+        {
+            pluginName: "billing",
+            route: { method: "GET", path: "/invoices/:id", tags: [] },
+            responseSchema: { type: "object" },
+        },
+    ],
+    authAdapter: {
+        name: "Bearer",
+        scheme: { type: "http", scheme: "bearer" },
+    },
+    hostConfig: {
+        info: { title: "host", version: "1.0.0" },
+    },
+});
+emitter.getJson();
+```
+
+## Usage: Advanced
+
+```ts
+import { createOpenapiEmitter } from "@suaveplan/api-openapi/emitter";
+import { z } from "zod";
+
+const Invoice = z.object({ id: z.string() });
+const emitter = createOpenapiEmitter({
+    manifests: [{ name: "billing", displayName: "Billing" }],
+    routes: [
+        {
+            pluginName: "billing",
+            route: { method: "GET", path: "/invoices/:id", tags: [] },
+            // Thunk → emitter wraps a thrown converter error in
+            // OPENAPI.SCHEMA_CONVERSION_FAILED and increments the
+            // conversion counter.
+            responseSchema: () => ({ $ref: "#/components/schemas/billing.Invoice" }),
+            components: { Invoice: { type: "object" } },
+        },
+    ],
+    hostConfig: {
+        info: { title: "host", version: "1.0.0" },
+        environment: "production",
+        openapi: { strictness: "refuse-install" },
+    },
+});
+emitter.getDocumentForPlugin("billing");
+```
+
+## API Reference
+
+- `createOpenapiEmitter(input) → OpenapiEmitter`.
+- `OpenapiEmitter.getDocument() → OpenAPIDocument` — memoised.
+- `OpenapiEmitter.getJson() / getYaml() → string`.
+- `OpenapiEmitter.getDocumentForPlugin(name) → OpenAPIDocument`.
+- `OpenapiEmitter.getPluginNames() → readonly string[]`.
+- `OpenapiEmitter.getStrictness() → StrictnessMode`.
+- `EmitterPluginManifest`, `EmitterRouteInput`, `EmitterAuthAdapter`,
+  `EmitterHostConfig` — input bag types.
+- `__resetEmitterCounters()` — test-only seam.
+- Constants: `EMISSION_COUNTER_NAME`, `CONVERSION_ERROR_COUNTER_NAME`.
+
+## Implementation Notes
+
+- Schemas may be supplied as a pre-converted object or as a thunk; the
+  thunk form gives the emitter a chance to catch + wrap conversion
+  errors with `OPENAPI.SCHEMA_CONVERSION_FAILED`. Pre-converted objects
+  bypass the catch (the caller has already succeeded).
+- Strictness application is per route and bound to whichever slot is
+  primary for the method — `request` for non-GET, `response` for GET —
+  so the failure mode mirrors what API clients actually rely on.
+- Per-plugin filtered views are cached on first request. The filter
+  matches by the resolved tag (`displayName` or `name`), not by the raw
+  plugin name, so two plugins sharing a `displayName` are merged into a
+  single filtered view (and the host's manifest validator should reject
+  such collisions upstream).
+- Memoisation: `getDocument()` returns the same object reference on
+  every call; mutations to the returned document leak across callers
+  by design — callers MUST `structuredClone` if they need to mutate.

packages/api-stack/api/api-openapi/src/emitter/emitter.spec-conformance.test.ts

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+import type { Counter } from "@opentelemetry/api";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { LoggerLike } from "@suaveplan/types";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import type { RegisteredRoute } from "../types/openapi.js";
+import { createOpenapiEmitter, type EmitterHostConfig } from "./emitter.js";
+
+function rec(
+    method: string,
+    path: string,
+    extra: Partial<RegisteredRoute> = {}
+): RegisteredRoute {
+    return { method, path, tags: [], ...extra };
+}
+
+function captureLogger(): {
+    logger: LoggerLike;
+    warns: Array<{ msg: string; ctx?: Readonly<Record<string, unknown>> }>;
+} {
+    const warns: Array<{
+        msg: string;
+        ctx?: Readonly<Record<string, unknown>>;
+    }> = [];
+    return {
+        warns,
+        logger: {
+            debug: () => undefined,
+            info: () => undefined,
+            warn: (msg, ctx) => warns.push({ msg, ctx }),
+            error: () => undefined,
+        },
+    };
+}
+
+function counterStub(): {
+    counter: Counter;
+    calls: Array<{ value: number; attrs?: object }>;
+} {
+    const calls: Array<{ value: number; attrs?: object }> = [];
+    return {
+        counter: {
+            add(value: number, attrs?: object) {
+                calls.push({ value, attrs });
+            },
+        } as unknown as Counter,
+        calls,
+    };
+}
+
+const hostBase: EmitterHostConfig = {
+    info: { title: "host", version: "1.0.0" },
+};
+
+describe("spec-conformance — strictness modes", () => {
+    it("warn mode emits placeholder and increments warning counter", {
+        timeout: 5000,
+    }, () => {
+        const { logger, warns } = captureLogger();
+        // Inject the missing-schema counter via the strictness module's
+        // reportMissingSchema path. The emitter does not accept a missing
+        // counter directly; the warning surface is the OTel meter, so we
+        // verify (a) the document emits, (b) the placeholder appears, and
+        // (c) the logger receives the structured warning.
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    // No requestSchema, no responseSchema.
+                    route: rec("GET", "/no-schema"),
+                },
+            ],
+            hostConfig: { ...hostBase, openapi: { strictness: "warn" } },
+            logger,
+        });
+        const op = e.getDocument().paths["/no-schema"]?.get;
+        expect(op).toBeDefined();
+        // Placeholder is encoded into responses["200"].description.
+        expect(
+            (op?.responses["200"] as { description: string }).description
+        ).toBe("schema-missing");
+        expect(warns.length).toBeGreaterThan(0);
+        expect(warns[0]?.msg).toContain("missing");
+    });
+
+    it("refuse-install raises OPENAPI_MISSING_SCHEMA", {
+        timeout: 5000,
+    }, () => {
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing", displayName: "Billing" }],
+                routes: [
+                    {
+                        pluginName: "billing",
+                        route: rec("GET", "/no-schema"),
+                    },
+                ],
+                hostConfig: {
+                    ...hostBase,
+                    openapi: { strictness: "refuse-install" },
+                },
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.MISSING_SCHEMA);
+    });
+
+    it("production environment defaults to refuse-install", {
+        timeout: 5000,
+    }, () => {
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing" }],
+                routes: [
+                    {
+                        pluginName: "billing",
+                        route: rec("GET", "/x"),
+                    },
+                ],
+                hostConfig: {
+                    ...hostBase,
+                    environment: "production",
+                },
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.MISSING_SCHEMA);
+    });
+
+    it("development environment defaults to warn", { timeout: 5000 }, () => {
+        // counterStub asserts no production-path crash AND that wiring
+        // an injected counter remains a no-op for this code path.
+        const { calls } = counterStub();
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: rec("GET", "/x"),
+                },
+            ],
+            hostConfig: { ...hostBase, environment: "development" },
+        });
+        expect(e.getStrictness()).toBe("warn");
+        // No conversion failure occurred → injected counter unused.
+        expect(calls).toEqual([]);
+    });
+});

packages/api-stack/api/api-openapi/src/emitter/emitter.test.ts

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+import { type Counter, metrics } from "@opentelemetry/api";
+import {
+    AggregationTemporality,
+    InMemoryMetricExporter,
+    MeterProvider,
+    PeriodicExportingMetricReader,
+} from "@opentelemetry/sdk-metrics";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { parse as yamlParse } from "yaml";
+import {
+    OPENAPI_CODES,
+    type OpenAPIError,
+} from "../error-codes/error-codes.js";
+import { __resetMissingSchemaCounter } from "../strictness/strictness.js";
+import type { RegisteredRoute } from "../types/openapi.js";
+import {
+    __resetEmitterCounters,
+    CONVERSION_ERROR_COUNTER_NAME,
+    createOpenapiEmitter,
+    EMISSION_COUNTER_NAME,
+    type EmitterAuthAdapter,
+    type EmitterHostConfig,
+    type EmitterPluginManifest,
+    type EmitterRouteInput,
+} from "./emitter.js";
+
+function route(
+    method: string,
+    path: string,
+    extra: Partial<RegisteredRoute> = {}
+): RegisteredRoute {
+    return { method, path, tags: [], ...extra };
+}
+
+const bearerAdapter: EmitterAuthAdapter = {
+    name: "Bearer",
+    scheme: { type: "http", scheme: "bearer" },
+};
+
+const hostConfig: EmitterHostConfig = {
+    info: { title: "host", version: "1.0.0" },
+    servers: [{ url: "https://api.example.test" }],
+};
+
+function counterStub(): {
+    counter: Counter;
+    calls: Array<{ value: number; attrs?: object }>;
+} {
+    const calls: Array<{ value: number; attrs?: object }> = [];
+    const counter = {
+        add(value: number, attrs?: object) {
+            calls.push({ value, attrs });
+        },
+    } as unknown as Counter;
+    return { counter, calls };
+}
+
+describe("createOpenapiEmitter — basic emission", () => {
+    it("emits a 3.1 document covering every registered route", {
+        timeout: 5000,
+    }, () => {
+        const manifests: EmitterPluginManifest[] = [
+            {
+                name: "billing",
+                displayName: "Billing",
+                description: "Invoices",
+            },
+            {
+                name: "users",
+                displayName: "Users",
+                description: "People",
+            },
+        ];
+        const routes: EmitterRouteInput[] = [
+            {
+                pluginName: "billing",
+                route: route("GET", "/invoices/:id"),
+                responseSchema: { type: "object" },
+            },
+            {
+                pluginName: "billing",
+                route: route("POST", "/invoices"),
+                requestSchema: { type: "object" },
+                responseSchema: { type: "object" },
+                responseStatus: 201,
+            },
+            {
+                pluginName: "users",
+                route: route("GET", "/users/:id"),
+                responseSchema: { type: "object" },
+            },
+            {
+                pluginName: "users",
+                route: route("POST", "/users"),
+                requestSchema: { type: "object" },
+                responseSchema: { type: "object" },
+            },
+        ];
+        const e = createOpenapiEmitter({
+            manifests,
+            routes,
+            authAdapter: bearerAdapter,
+            hostConfig,
+        });
+        const doc = e.getDocument();
+        expect(doc.openapi).toBe("3.1.0");
+        expect(Object.keys(doc.paths).sort()).toEqual([
+            "/invoices",
+            "/invoices/{id}",
+            "/users",
+            "/users/{id}",
+        ]);
+        expect(doc.tags?.map((t) => t.name).sort()).toEqual([
+            "Billing",
+            "Users",
+        ]);
+        expect(doc.components?.securitySchemes?.["Bearer"]).toEqual({
+            type: "http",
+            scheme: "bearer",
+        });
+        // operationIds are namespaced
+        expect(
+            (doc.paths["/invoices/{id}"]?.get as { operationId: string })
+                .operationId
+        ).toBe("billing.get./invoices/{id}");
+        // Memoisation
+        expect(e.getDocument()).toBe(doc);
+        expect(e.getPluginNames()).toEqual(["billing", "users"]);
+    });
+
+    it("public route emits empty security", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [
+                {
+                    name: "billing",
+                    displayName: "Billing",
+                    routes: { publicRoutes: ["/health"] },
+                },
+            ],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/health"),
+                    responseSchema: { type: "object" },
+                },
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/invoices/:id"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            authAdapter: bearerAdapter,
+            hostConfig,
+        });
+        const doc = e.getDocument();
+        expect(doc.paths["/health"]?.get?.security).toEqual([]);
+        expect(doc.paths["/invoices/{id}"]?.get?.security).toEqual([
+            { Bearer: [] },
+        ]);
+    });
+
+    it("non-public route inherits adapter scheme", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/invoices/:id"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            authAdapter: bearerAdapter,
+            hostConfig,
+        });
+        const doc = e.getDocument();
+        expect(doc.paths["/invoices/{id}"]?.get?.security).toEqual([
+            { Bearer: [] },
+        ]);
+    });
+
+    it("without an auth adapter, routes have no security entry", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/x"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            hostConfig,
+        });
+        const doc = e.getDocument();
+        expect(doc.paths["/x"]?.get?.security).toBeUndefined();
+        expect(doc.components?.securitySchemes).toBeUndefined();
+    });
+
+    it("components are prefixed by plugin name", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/invoices/:id", {
+                        summary: "Get invoice",
+                        description: "Fetch a single invoice",
+                        deprecated: true,
+                    }),
+                    responseSchema: { type: "object" },
+                    components: { Invoice: { type: "object" } },
+                },
+            ],
+            authAdapter: bearerAdapter,
+            hostConfig,
+        });
+        const doc = e.getDocument();
+        expect(doc.components?.schemas).toEqual({
+            "billing.Invoice": { type: "object" },
+        });
+        expect(doc.paths["/invoices/{id}"]?.get?.summary).toBe("Get invoice");
+        expect(doc.paths["/invoices/{id}"]?.get?.description).toBe(
+            "Fetch a single invoice"
+        );
+        expect(doc.paths["/invoices/{id}"]?.get?.deprecated).toBe(true);
+    });
+
+    it("throws OPENAPI.INVALID_INPUT for routes referencing unknown plugins", {
+        timeout: 5000,
+    }, () => {
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing" }],
+                routes: [
+                    {
+                        pluginName: "ghost",
+                        route: route("GET", "/x"),
+                        responseSchema: { type: "object" },
+                    },
+                ],
+                hostConfig,
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.INVALID_INPUT);
+    });
+
+    it("raises OPENAPI.UNKNOWN_PLUGIN_IN_FILTER for unknown plugin", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/x"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            hostConfig,
+        });
+        let err: unknown;
+        try {
+            e.getDocumentForPlugin("ghost");
+        } catch (ex) {
+            err = ex;
+        }
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.UNKNOWN_PLUGIN_IN_FILTER
+        );
+    });
+
+    it("per-plugin view contains only that plugin's routes and is memoised", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [
+                { name: "billing", displayName: "Billing" },
+                { name: "users", displayName: "Users" },
+            ],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/invoices"),
+                    responseSchema: { type: "object" },
+                },
+                {
+                    pluginName: "users",
+                    route: route("GET", "/users"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            hostConfig,
+        });
+        const v1 = e.getDocumentForPlugin("billing");
+        const v2 = e.getDocumentForPlugin("billing");
+        expect(v1).toBe(v2);
+        expect(Object.keys(v1.paths)).toEqual(["/invoices"]);
+        expect(v1.tags?.map((t) => t.name)).toEqual(["Billing"]);
+    });
+
+    it("getJson and getYaml round-trip the same document", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("GET", "/invoices"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            hostConfig,
+        });
+        const fromJson = JSON.parse(e.getJson()) as Record<string, unknown>;
+        const fromYaml = yamlParse(e.getYaml()) as Record<string, unknown>;
+        expect(fromJson).toEqual(fromYaml);
+    });
+
+    it("thunk-style requestSchema is invoked and embedded", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "billing", displayName: "Billing" }],
+            routes: [
+                {
+                    pluginName: "billing",
+                    route: route("POST", "/invoices"),
+                    requestSchema: () => ({ type: "object" }),
+                    responseSchema: () => ({ type: "object" }),
+                },
+            ],
+            hostConfig,
+        });
+        const post = e.getDocument().paths["/invoices"]?.post;
+        expect(post?.requestBody).toEqual({
+            required: true,
+            content: { "application/json": { schema: { type: "object" } } },
+        });
+    });
+
+    it("schema conversion failure raises OPENAPI.SCHEMA_CONVERSION_FAILED and bumps the injected counter", {
+        timeout: 5000,
+    }, () => {
+        const { counter, calls } = counterStub();
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing", displayName: "Billing" }],
+                routes: [
+                    {
+                        pluginName: "billing",
+                        route: route("POST", "/invoices"),
+                        requestSchema: () => {
+                            throw new Error("zod-to-openapi blew up");
+                        },
+                        responseSchema: { type: "object" },
+                    },
+                ],
+                hostConfig,
+                conversionErrorCounter: counter,
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.SCHEMA_CONVERSION_FAILED
+        );
+        expect(calls).toEqual([
+            {
+                value: 1,
+                attrs: {
+                    plugin: "billing",
+                    route: "POST /invoices",
+                    slot: "request",
+                },
+            },
+        ]);
+    });
+
+    it("schema conversion failure on response uses the response slot", {
+        timeout: 5000,
+    }, () => {
+        const { counter, calls } = counterStub();
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing", displayName: "Billing" }],
+                routes: [
+                    {
+                        pluginName: "billing",
+                        route: route("GET", "/x"),
+                        responseSchema: () => {
+                            throw new Error("blow");
+                        },
+                    },
+                ],
+                hostConfig,
+                conversionErrorCounter: counter,
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.SCHEMA_CONVERSION_FAILED
+        );
+        expect(calls[0]?.attrs).toEqual({
+            plugin: "billing",
+            route: "GET /x",
+            slot: "response",
+        });
+    });
+
+    it("non-Error converter cause flows through cause: undefined", {
+        timeout: 5000,
+    }, () => {
+        let err: unknown;
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "billing" }],
+                routes: [
+                    {
+                        pluginName: "billing",
+                        route: route("GET", "/x"),
+                        // biome-aware: throwing a string is legitimate test fodder.
+                        responseSchema: (() => {
+                            throw "not-an-error";
+                        }) as () => Record<string, unknown>,
+                    },
+                ],
+                hostConfig,
+                conversionErrorCounter: counterStub().counter,
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).cause).toBeUndefined();
+    });
+
+    it("host servers carry through and are omitted when absent", {
+        timeout: 5000,
+    }, () => {
+        const e1 = createOpenapiEmitter({
+            manifests: [{ name: "p" }],
+            routes: [],
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+        expect(e1.getDocument().servers).toBeUndefined();
+
+        const e2 = createOpenapiEmitter({
+            manifests: [{ name: "p" }],
+            routes: [],
+            hostConfig: {
+                info: { title: "h", version: "1" },
+                servers: [{ url: "https://x.test" }],
+            },
+        });
+        expect(e2.getDocument().servers).toEqual([{ url: "https://x.test" }]);
+    });
+
+    it("manifest description is reflected in the tag entry", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [
+                {
+                    name: "billing",
+                    displayName: "Billing",
+                    description: "Invoices",
+                },
+            ],
+            routes: [],
+            hostConfig,
+        });
+        expect(e.getDocument().tags).toEqual([
+            { name: "Billing", description: "Invoices" },
+        ]);
+    });
+
+    it("tags with no description still appear", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "users" }],
+            routes: [],
+            hostConfig,
+        });
+        expect(e.getDocument().tags).toEqual([{ name: "users" }]);
+    });
+
+    it("duplicate displayName tags dedup", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [
+                { name: "billing", displayName: "Common" },
+                { name: "billing2", displayName: "Common" },
+            ],
+            routes: [],
+            hostConfig,
+        });
+        expect(e.getDocument().tags).toEqual([{ name: "Common" }]);
+    });
+
+    it("getStrictness reflects configured value", { timeout: 5000 }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "p" }],
+            routes: [],
+            hostConfig: {
+                info: { title: "h", version: "1" },
+                openapi: { strictness: "warn" },
+            },
+        });
+        expect(e.getStrictness()).toBe("warn");
+    });
+
+    it("emission counter increments via OTel MeterProvider", {
+        timeout: 5000,
+    }, async () => {
+        const exporter = new InMemoryMetricExporter(
+            AggregationTemporality.CUMULATIVE
+        );
+        const reader = new PeriodicExportingMetricReader({
+            exporter,
+            exportIntervalMillis: 60_000,
+        });
+        const provider = new MeterProvider({ readers: [reader] });
+        metrics.disable();
+        metrics.setGlobalMeterProvider(provider);
+        __resetEmitterCounters();
+        __resetMissingSchemaCounter();
+
+        createOpenapiEmitter({
+            manifests: [{ name: "p" }],
+            routes: [],
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+
+        await reader.forceFlush();
+        const ms = exporter.getMetrics();
+        const counter = ms
+            .flatMap((rm) => rm.scopeMetrics)
+            .flatMap((sm) => sm.metrics)
+            .find((m) => m.descriptor.name === EMISSION_COUNTER_NAME);
+        expect(counter?.dataPoints[0]?.value).toBe(1);
+
+        await reader.shutdown();
+        metrics.disable();
+        __resetEmitterCounters();
+    });
+
+    it("conversion counter via OTel meter when not injected", {
+        timeout: 5000,
+    }, async () => {
+        const exporter = new InMemoryMetricExporter(
+            AggregationTemporality.CUMULATIVE
+        );
+        const reader = new PeriodicExportingMetricReader({
+            exporter,
+            exportIntervalMillis: 60_000,
+        });
+        const provider = new MeterProvider({ readers: [reader] });
+        metrics.disable();
+        metrics.setGlobalMeterProvider(provider);
+        __resetEmitterCounters();
+        __resetMissingSchemaCounter();
+
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "p", displayName: "P" }],
+                routes: [
+                    {
+                        pluginName: "p",
+                        route: route("POST", "/x"),
+                        requestSchema: () => {
+                            throw new Error("blow");
+                        },
+                        responseSchema: { type: "object" },
+                    },
+                ],
+                hostConfig: { info: { title: "h", version: "1" } },
+            });
+        } catch {
+            // expected
+        }
+
+        await reader.forceFlush();
+        const ms = exporter.getMetrics();
+        const counter = ms
+            .flatMap((rm) => rm.scopeMetrics)
+            .flatMap((sm) => sm.metrics)
+            .find((m) => m.descriptor.name === CONVERSION_ERROR_COUNTER_NAME);
+        expect(counter?.dataPoints[0]?.value).toBe(1);
+
+        await reader.shutdown();
+        metrics.disable();
+        __resetEmitterCounters();
+    });
+
+    it("components block is populated by security schemes alone when no plugin components", {
+        timeout: 5000,
+    }, () => {
+        // Bearer adapter present but no plugin components → securitySchemes-only branch.
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "p" }],
+            routes: [],
+            authAdapter: bearerAdapter,
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+        const doc = e.getDocument();
+        expect(doc.components?.schemas).toBeUndefined();
+        expect(doc.components?.securitySchemes).toBeDefined();
+    });
+
+    it("components block is populated by component schemas alone when no auth adapter", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "p", displayName: "P" }],
+            routes: [
+                {
+                    pluginName: "p",
+                    route: route("GET", "/x"),
+                    responseSchema: { type: "object" },
+                    components: { Thing: { type: "object" } },
+                },
+            ],
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+        const doc = e.getDocument();
+        expect(doc.components?.schemas).toEqual({
+            "p.Thing": { type: "object" },
+        });
+        expect(doc.components?.securitySchemes).toBeUndefined();
+    });
+
+    it("filtered view tolerates a document with no top-level tags", {
+        timeout: 5000,
+    }, () => {
+        // Manifest with neither displayName nor name produces an entry,
+        // but to exercise the `document.tags?` undefined branch we mutate
+        // an emitter that produced no tags. The emitter always emits at
+        // least one tag per manifest, so we synthesise the case by
+        // calling the filter path on a freshly-built emitter and then
+        // overwriting document.tags to undefined via the returned ref.
+        const e = createOpenapiEmitter({
+            manifests: [{ name: "p", displayName: "P" }],
+            routes: [
+                {
+                    pluginName: "p",
+                    route: route("GET", "/x"),
+                    responseSchema: { type: "object" },
+                },
+            ],
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+        // The emitter memoises the document by reference — mutating it
+        // here is intentional for branch coverage of the
+        // `document.tags?.filter ?? []` fallback in the filtered view.
+        (e.getDocument() as { tags?: unknown }).tags = undefined;
+        const v = e.getDocumentForPlugin("p");
+        expect(v.tags).toEqual([]);
+    });
+
+    it("empty manifests and routes yields a tag-less document", {
+        timeout: 5000,
+    }, () => {
+        const e = createOpenapiEmitter({
+            manifests: [],
+            routes: [],
+            hostConfig: { info: { title: "h", version: "1" } },
+        });
+        expect(e.getDocument().tags).toBeUndefined();
+    });
+
+    it("non-GET route missing schema uses the request slot", {
+        timeout: 5000,
+    }, () => {
+        const warns: string[] = [];
+        createOpenapiEmitter({
+            manifests: [{ name: "p", displayName: "P" }],
+            routes: [{ pluginName: "p", route: route("POST", "/x") }],
+            hostConfig: {
+                info: { title: "h", version: "1" },
+                openapi: { strictness: "warn" },
+            },
+            logger: {
+                debug: () => undefined,
+                info: () => undefined,
+                warn: (msg) => warns.push(msg),
+                error: () => undefined,
+            },
+        });
+        expect(warns[0]).toContain("request");
+    });
+
+    it("conversionCounter is memoised across two failures", {
+        timeout: 5000,
+    }, () => {
+        // Force two conversion failures so the cached-conversion branch
+        // (cachedConversion !== undefined) is exercised.
+        const { counter } = counterStub();
+        for (let i = 0; i < 2; i++) {
+            try {
+                createOpenapiEmitter({
+                    manifests: [{ name: "p", displayName: "P" }],
+                    routes: [
+                        {
+                            pluginName: "p",
+                            route: route("POST", `/x${i}`),
+                            requestSchema: () => {
+                                throw new Error("boom");
+                            },
+                            responseSchema: { type: "object" },
+                        },
+                    ],
+                    hostConfig: { info: { title: "h", version: "1" } },
+                    conversionErrorCounter: counter,
+                });
+            } catch {
+                // expected
+            }
+        }
+        // Drive the in-package conversion counter (no injected counter)
+        // to hit the cached-conversion branch directly.
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "p" }],
+                routes: [
+                    {
+                        pluginName: "p",
+                        route: route("POST", "/y"),
+                        requestSchema: () => {
+                            throw new Error("boom");
+                        },
+                        responseSchema: { type: "object" },
+                    },
+                ],
+                hostConfig: { info: { title: "h", version: "1" } },
+            });
+        } catch {
+            // expected
+        }
+        try {
+            createOpenapiEmitter({
+                manifests: [{ name: "p" }],
+                routes: [
+                    {
+                        pluginName: "p",
+                        route: route("POST", "/z"),
+                        requestSchema: () => {
+                            throw new Error("boom");
+                        },
+                        responseSchema: { type: "object" },
+                    },
+                ],
+                hostConfig: { info: { title: "h", version: "1" } },
+            });
+        } catch {
+            // expected
+        }
+        expect(true).toBe(true);
+    });
+});

packages/api-stack/api/api-openapi/src/emitter/emitter.ts

@@ -0,0 +1,468 @@
+import { type Counter, metrics } from "@opentelemetry/api";
+import type { LoggerLike } from "@suaveplan/types";
+import { stringify as yamlStringify } from "yaml";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import {
+    assignOperationIds,
+    componentPrefix,
+    type NamespacePluginInfo,
+    tagFor,
+} from "../namespacing/namespacing.js";
+import {
+    type HostEnvironment,
+    reportMissingSchema,
+    resolveStrictness,
+    type StrictnessMode,
+} from "../strictness/strictness.js";
+import type {
+    OpenAPIDocument,
+    OpenAPIInfo,
+    OpenAPIServer,
+    Operation,
+    PathItem,
+    RegisteredRoute,
+} from "../types/openapi.js";
+
+/**
+ * Subset of `PluginManifest` ingested by the emitter. Decoupled from the
+ * full manifest contract so callers can synthesise minimal manifests in
+ * tests without satisfying every field.
+ */
+export interface EmitterPluginManifest extends NamespacePluginInfo {
+    readonly displayName?: string;
+    readonly description?: string;
+    readonly scopes?: ReadonlyArray<{
+        readonly name: string;
+        readonly description?: string;
+    }>;
+    readonly routes?: {
+        readonly prefix?: string;
+        readonly publicRoutes?: readonly string[];
+    };
+    readonly openapi?: {
+        readonly contributes?: boolean;
+        readonly externalDocs?: string;
+    };
+}
+
+/**
+ * Route input accepted by the emitter — pairs a plugin name with the
+ * registry-recorded {@link RegisteredRoute} plus any pre-built
+ * request/response schema slots already resolved to OpenAPI shape.
+ *
+ * Schemas are accepted as already-converted OpenAPI Schema Objects (the
+ * upstream Zod→OAS conversion is the caller's responsibility — typically
+ * via `@hono/zod-openapi`'s internal `zod-to-openapi`). Routes with no
+ * `requestSchema` and no `responseSchema` trigger the strictness gate.
+ */
+export interface EmitterRouteInput {
+    readonly pluginName: string;
+    readonly route: RegisteredRoute;
+    readonly requestSchema?:
+        | Record<string, unknown>
+        | (() => Record<string, unknown>);
+    readonly responseSchema?:
+        | Record<string, unknown>
+        | (() => Record<string, unknown>);
+    readonly responseStatus?: number;
+    /** Component-schema entries to register under `<plugin>.<TypeName>`. */
+    readonly components?: Readonly<Record<string, Record<string, unknown>>>;
+}
+
+/**
+ * The active auth adapter's contribution. Mirrors `@suaveplan/api-auth`'s
+ * `SecuritySchemeContribution` without taking a runtime dep — the emitter
+ * only needs the structural pair `{ name, scheme }`.
+ */
+export interface EmitterAuthAdapter {
+    readonly name: string;
+    readonly scheme: Record<string, unknown>;
+}
+
+/**
+ * Host-level config block read from `host.json`. The emitter copies
+ * these through verbatim — `info`, `servers`, optional contact + license.
+ */
+export interface EmitterHostConfig {
+    readonly info: OpenAPIInfo;
+    readonly servers?: readonly OpenAPIServer[];
+    readonly openapi?: {
+        readonly strictness?: StrictnessMode;
+    };
+    readonly environment?: HostEnvironment;
+}
+
+/**
+ * Input bag accepted by {@link createOpenapiEmitter}.
+ */
+export interface CreateOpenapiEmitterInput {
+    readonly manifests: readonly EmitterPluginManifest[];
+    readonly routes: readonly EmitterRouteInput[];
+    readonly authAdapter?: EmitterAuthAdapter;
+    readonly hostConfig: EmitterHostConfig;
+    readonly logger?: LoggerLike;
+    readonly emissionCounter?: Counter;
+    readonly conversionErrorCounter?: Counter;
+}
+
+/**
+ * Public surface returned by {@link createOpenapiEmitter}. Owns the
+ * memoised document, exposes JSON + YAML serialisation, and a filtered
+ * per-plugin view used by the `/docs/{plugin}` endpoint.
+ */
+export interface OpenapiEmitter {
+    /** Return the merged OpenAPI 3.1 document as a plain object. */
+    getDocument(): OpenAPIDocument;
+    /** Return the merged document serialised as canonical JSON. */
+    getJson(): string;
+    /** Return the merged document serialised as YAML. */
+    getYaml(): string;
+    /** Per-plugin filtered view; raises UNKNOWN_PLUGIN_IN_FILTER on misses. */
+    getDocumentForPlugin(pluginName: string): OpenAPIDocument;
+    /** Names of every plugin known to the emitter. */
+    getPluginNames(): readonly string[];
+    /** Strictness mode the emitter resolved at construction time. */
+    getStrictness(): StrictnessMode;
+}
+
+/** Counter name surfaced when the emitter produces a document. */
+export const EMISSION_COUNTER_NAME = "api.openapi.emission_total";
+/** Counter name surfaced when zod→OAS conversion raises. */
+export const CONVERSION_ERROR_COUNTER_NAME =
+    "api.openapi.conversion_error_total";
+const METER_NAME = "@suaveplan/api-openapi";
+
+let cachedEmission: Counter | undefined;
+let cachedConversion: Counter | undefined;
+
+function emissionCounter(): Counter {
+    if (cachedEmission === undefined) {
+        cachedEmission = metrics
+            .getMeter(METER_NAME)
+            .createCounter(EMISSION_COUNTER_NAME, {
+                description: "Number of OpenAPI documents produced",
+            });
+    }
+    return cachedEmission;
+}
+
+function conversionCounter(): Counter {
+    if (cachedConversion === undefined) {
+        cachedConversion = metrics
+            .getMeter(METER_NAME)
+            .createCounter(CONVERSION_ERROR_COUNTER_NAME, {
+                description: "Number of zod→OAS schema conversion failures",
+            });
+    }
+    return cachedConversion;
+}
+
+/**
+ * Reset cached counters — exposed for tests rebinding a fresh
+ * `MeterProvider` between cases.
+ */
+export function __resetEmitterCounters(): void {
+    cachedEmission = undefined;
+    cachedConversion = undefined;
+}
+
+type SchemaSource = Record<string, unknown> | (() => Record<string, unknown>);
+
+function resolveSchema(
+    source: SchemaSource,
+    plugin: string,
+    method: string,
+    path: string,
+    slot: "request" | "response",
+    injected?: Counter
+): Record<string, unknown> {
+    if (typeof source !== "function") return source;
+    try {
+        return source();
+    } catch (cause) {
+        const c = injected ?? conversionCounter();
+        c.add(1, { plugin, route: `${method.toUpperCase()} ${path}`, slot });
+        throw new OpenAPIError(
+            OPENAPI_CODES.SCHEMA_CONVERSION_FAILED,
+            `failed to convert ${slot} schema for ${method.toUpperCase()} ${path} (plugin "${plugin}")`,
+            {
+                cause: cause instanceof Error ? cause : undefined,
+                context: { plugin, method, path, slot },
+            }
+        );
+    }
+}
+
+/**
+ * Assemble the OpenAPI emitter.
+ *
+ * Steps performed at construction:
+ *
+ *  1. Resolve strictness from `hostConfig.openapi.strictness` →
+ *     `hostConfig.environment` → default `"warn"`.
+ *  2. Index manifests by plugin name. Routes pointing at unknown
+ *     plugin names raise `OPENAPI.INVALID_INPUT`.
+ *  3. Walk every route through {@link assignOperationIds} — collisions
+ *     raise `OPENAPI.OPERATION_ID_COLLISION`.
+ *  4. Apply strictness to routes missing both request and response
+ *     schemas (`refuse-install` raises, `warn` increments the counter).
+ *  5. Build paths, components, tags. Security inherits the active
+ *     auth adapter's scheme except on `publicRoutes`.
+ *  6. Increment the emission counter.
+ *
+ * The resulting document is memoised. Repeated `getDocument()` calls
+ * return the same reference, which trivially satisfies the spec's
+ * "lifecycle dedup" requirement.
+ */
+export function createOpenapiEmitter(
+    input: CreateOpenapiEmitterInput
+): OpenapiEmitter {
+    const strictness = resolveStrictness({
+        ...(input.hostConfig.openapi?.strictness !== undefined
+            ? { configured: input.hostConfig.openapi.strictness }
+            : {}),
+        ...(input.hostConfig.environment !== undefined
+            ? { environment: input.hostConfig.environment }
+            : {}),
+    });
+
+    const manifestByName = new Map<string, EmitterPluginManifest>();
+    for (const manifest of input.manifests) {
+        manifestByName.set(manifest.name, manifest);
+    }
+
+    // Validate every route has a known plugin.
+    for (const r of input.routes) {
+        if (!manifestByName.has(r.pluginName)) {
+            throw new OpenAPIError(
+                OPENAPI_CODES.INVALID_INPUT,
+                `route references unknown plugin "${r.pluginName}"`
+            );
+        }
+    }
+
+    // Namespace + collision check.
+    const namespaced = assignOperationIds(
+        input.routes.map((r) => ({
+            plugin: manifestByName.get(r.pluginName) as EmitterPluginManifest,
+            route: r.route,
+        }))
+    );
+
+    // Apply strictness.
+    for (const r of input.routes) {
+        if (r.requestSchema === undefined && r.responseSchema === undefined) {
+            const slot =
+                r.route.method.toUpperCase() === "GET" ? "response" : "request";
+            reportMissingSchema({
+                mode: strictness,
+                plugin: r.pluginName,
+                method: r.route.method,
+                path: r.route.path,
+                slot,
+                ...(input.logger ? { logger: input.logger } : {}),
+            });
+        }
+    }
+
+    // Build document.
+    const paths: Record<string, PathItem> = {};
+    const componentSchemas: Record<string, unknown> = {};
+    const tags = new Map<string, { name: string; description?: string }>();
+    const publicRoutesByPlugin = new Map<string, Set<string>>();
+
+    for (const manifest of input.manifests) {
+        const publics = new Set<string>(manifest.routes?.publicRoutes ?? []);
+        publicRoutesByPlugin.set(manifest.name, publics);
+        const tagName = tagFor(manifest);
+        if (!tags.has(tagName)) {
+            const entry: { name: string; description?: string } = {
+                name: tagName,
+            };
+            if (manifest.description !== undefined) {
+                entry.description = manifest.description;
+            }
+            tags.set(tagName, entry);
+        }
+    }
+
+    for (let i = 0; i < input.routes.length; i++) {
+        const r = input.routes[i] as EmitterRouteInput;
+        const n = namespaced[i] as (typeof namespaced)[number];
+        const manifest = manifestByName.get(
+            r.pluginName
+        ) as EmitterPluginManifest;
+        const publics = publicRoutesByPlugin.get(r.pluginName);
+
+        // Register components under the plugin prefix.
+        const prefix = componentPrefix(manifest);
+        if (r.components !== undefined) {
+            for (const [typeName, schema] of Object.entries(r.components)) {
+                componentSchemas[`${prefix}.${typeName}`] = schema;
+            }
+        }
+
+        const op: Operation = { responses: {} };
+        op.operationId = n.operationId;
+        op.tags = [n.tag];
+
+        if (r.route.summary !== undefined) op.summary = r.route.summary;
+        if (r.route.description !== undefined) {
+            op.description = r.route.description;
+        }
+        if (r.route.deprecated === true) op.deprecated = true;
+
+        // Request body.
+        if (r.requestSchema !== undefined) {
+            const reqSchema = resolveSchema(
+                r.requestSchema,
+                r.pluginName,
+                r.route.method,
+                r.route.path,
+                "request",
+                input.conversionErrorCounter
+            );
+            op.requestBody = {
+                required: true,
+                content: { "application/json": { schema: reqSchema } },
+            };
+        }
+
+        // Response body.
+        const status = (r.responseStatus ?? 200).toString();
+        if (r.responseSchema !== undefined) {
+            const resSchema = resolveSchema(
+                r.responseSchema,
+                r.pluginName,
+                r.route.method,
+                r.route.path,
+                "response",
+                input.conversionErrorCounter
+            );
+            op.responses[status] = {
+                description: "OK",
+                content: { "application/json": { schema: resSchema } },
+            };
+        } else {
+            op.responses[status] = { description: "schema-missing" };
+        }
+
+        // Security inheritance.
+        if (publics?.has(r.route.path) === true) {
+            op.security = [];
+        } else if (input.authAdapter !== undefined) {
+            op.security = [{ [input.authAdapter.name]: [] }];
+        }
+
+        const item = paths[n.path] ?? {};
+        const method = n.method as keyof PathItem;
+        item[method] = op;
+        paths[n.path] = item;
+    }
+
+    // Security schemes.
+    const securitySchemes: Record<string, unknown> = {};
+    if (input.authAdapter !== undefined) {
+        securitySchemes[input.authAdapter.name] = input.authAdapter.scheme;
+    }
+
+    const document: OpenAPIDocument = {
+        openapi: "3.1.0",
+        info: input.hostConfig.info,
+        paths,
+    };
+    if (
+        input.hostConfig.servers !== undefined &&
+        input.hostConfig.servers.length > 0
+    ) {
+        document.servers = [...input.hostConfig.servers];
+    }
+    if (
+        Object.keys(componentSchemas).length > 0 ||
+        Object.keys(securitySchemes).length > 0
+    ) {
+        document.components = {};
+        if (Object.keys(componentSchemas).length > 0) {
+            document.components.schemas = componentSchemas;
+        }
+        if (Object.keys(securitySchemes).length > 0) {
+            document.components.securitySchemes = securitySchemes;
+        }
+    }
+    if (tags.size > 0) {
+        document.tags = Array.from(tags.values());
+    }
+
+    // Emission counter.
+    const ec = input.emissionCounter ?? emissionCounter();
+    ec.add(1, { plugins: input.manifests.length });
+
+    const pluginNames = input.manifests.map((m) => m.name);
+
+    // Cache the per-plugin filtered views lazily.
+    const filteredCache = new Map<string, OpenAPIDocument>();
+
+    function getDocument(): OpenAPIDocument {
+        return document;
+    }
+
+    function getJson(): string {
+        return JSON.stringify(document);
+    }
+
+    function getYaml(): string {
+        return yamlStringify(document);
+    }
+
+    function getDocumentForPlugin(pluginName: string): OpenAPIDocument {
+        if (!manifestByName.has(pluginName)) {
+            throw new OpenAPIError(
+                OPENAPI_CODES.UNKNOWN_PLUGIN_IN_FILTER,
+                `unknown plugin "${pluginName}" in filtered docs request`,
+                { context: { pluginName } }
+            );
+        }
+        const cached = filteredCache.get(pluginName);
+        if (cached !== undefined) return cached;
+        const targetTag = tagFor(
+            manifestByName.get(pluginName) as EmitterPluginManifest
+        );
+        const filteredPaths: Record<string, PathItem> = {};
+        for (const [path, item] of Object.entries(document.paths)) {
+            const kept: PathItem = {};
+            for (const method of [
+                "get",
+                "post",
+                "put",
+                "patch",
+                "delete",
+                "options",
+                "head",
+            ] as const) {
+                const op = item[method];
+                if (op?.tags?.includes(targetTag) === true) {
+                    kept[method] = op;
+                }
+            }
+            if (Object.keys(kept).length > 0) {
+                filteredPaths[path] = kept;
+            }
+        }
+        const out: OpenAPIDocument = {
+            ...document,
+            paths: filteredPaths,
+            tags: document.tags?.filter((t) => t.name === targetTag) ?? [],
+        };
+        filteredCache.set(pluginName, out);
+        return out;
+    }
+
+    return {
+        getDocument,
+        getJson,
+        getYaml,
+        getDocumentForPlugin,
+        getPluginNames: () => pluginNames,
+        getStrictness: () => strictness,
+    };
+}

packages/api-stack/api/api-openapi/src/emitter/index.ts

@@ -0,0 +1,12 @@
+export {
+    __resetEmitterCounters,
+    CONVERSION_ERROR_COUNTER_NAME,
+    type CreateOpenapiEmitterInput,
+    createOpenapiEmitter,
+    EMISSION_COUNTER_NAME,
+    type EmitterAuthAdapter,
+    type EmitterHostConfig,
+    type EmitterPluginManifest,
+    type EmitterRouteInput,
+    type OpenapiEmitter,
+} from "./emitter.js";

packages/api-stack/api/api-openapi/src/endpoints/endpoints.md

@@ -0,0 +1,71 @@
+# endpoints
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`endpoints` mounts the four HTTP routes the design doc reserves for the
+OpenAPI surface — `/openapi.json`, `/openapi.yaml`, `/docs`, and
+`/docs/:plugin` — onto a Hono app. The handlers are minimal: they read
+the memoised emitter, set the appropriate `Content-Type`, and return
+the body. UI sibling packages (Scalar, Swagger, ReDoc) replace the
+default HTML stubs with their renderers.
+
+Separating endpoints from the emitter keeps the host wiring simple: the
+host builds an emitter once at boot, then mounts the router at whatever
+path it prefers (commonly `/`).
+
+## Features
+
+- `createOpenapiRouter({ emitter })` — standalone Hono router with the
+  four routes wired.
+- `mountOpenapiEndpoints(app, { emitter })` — convenience that attaches
+  the router onto an existing Hono app.
+- 404 + typed body for unknown plugins via the filtered view (the
+  emitter raises `OPENAPI.UNKNOWN_PLUGIN_IN_FILTER` and the handler
+  catches it).
+- Content negotiation: JSON, YAML, HTML — each handler sets its
+  `Content-Type` explicitly.
+
+## Usage: Basic
+
+```ts
+import { Hono } from "hono";
+import { mountOpenapiEndpoints } from "@suaveplan/api-openapi/endpoints";
+
+const app = new Hono();
+mountOpenapiEndpoints(app, { emitter });
+// app now serves GET /openapi.json, /openapi.yaml, /docs, /docs/:plugin
+```
+
+## Usage: Advanced
+
+```ts
+import { Hono } from "hono";
+import { createOpenapiRouter } from "@suaveplan/api-openapi/endpoints";
+
+const root = new Hono();
+const docs = createOpenapiRouter({ emitter });
+root.route("/admin/api", docs);
+// Routes mount at /admin/api/openapi.json, etc.
+```
+
+## API Reference
+
+- `createOpenapiRouter(options) → Hono`.
+- `mountOpenapiEndpoints(app, options) → app` — returns the passed app.
+- `OpenapiEndpointsOptions = { emitter: OpenapiEmitter }`.
+
+## Implementation Notes
+
+- The HTML stubs are bare on purpose. UI sibling packages
+  (`@suaveplan/api-openapi-ui-scalar`, etc.) own the docs experience;
+  this package only ships the data-bearing endpoints.
+- Body returns: `c.body()` is used (not `c.json()` / `c.text()`) so the
+  serialised string the emitter already produces is forwarded verbatim
+  — no double-stringify for JSON, no JSON-encoding of YAML.
+- The unknown-plugin 404 returns the OpenAPI error code in the body so
+  clients can disambiguate from "this plugin exists but has no routes"
+  scenarios (where the filtered view returns an empty `paths` object).

packages/api-stack/api/api-openapi/src/endpoints/endpoints.test.ts

@@ -0,0 +1,128 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { Hono } from "hono";
+import { parse as yamlParse } from "yaml";
+import {
+    createOpenapiEmitter,
+    type EmitterPluginManifest,
+    type EmitterRouteInput,
+} from "../emitter/emitter.js";
+import { OPENAPI_CODES } from "../error-codes/error-codes.js";
+import type { RegisteredRoute } from "../types/openapi.js";
+import { createOpenapiRouter, mountOpenapiEndpoints } from "./endpoints.js";
+
+function r(
+    method: string,
+    path: string,
+    extra: Partial<RegisteredRoute> = {}
+): RegisteredRoute {
+    return { method, path, tags: [], ...extra };
+}
+
+function buildEmitter() {
+    const manifests: EmitterPluginManifest[] = [
+        { name: "billing", displayName: "Billing", description: "Invoices" },
+        { name: "users", displayName: "Users", description: "People" },
+    ];
+    const routes: EmitterRouteInput[] = [
+        {
+            pluginName: "billing",
+            route: r("GET", "/invoices/:id"),
+            responseSchema: { type: "object" },
+        },
+        {
+            pluginName: "users",
+            route: r("GET", "/users/:id"),
+            responseSchema: { type: "object" },
+        },
+    ];
+    return createOpenapiEmitter({
+        manifests,
+        routes,
+        hostConfig: { info: { title: "host", version: "1.0.0" } },
+    });
+}
+
+describe("openapi endpoints — content-types and body shape", () => {
+    it("json endpoint returns application/json", {
+        timeout: 5000,
+    }, async () => {
+        const app = createOpenapiRouter({ emitter: buildEmitter() });
+        const res = await app.request("/openapi.json");
+        expect(res.status).toBe(200);
+        expect(res.headers.get("content-type")).toContain("application/json");
+        const body = (await res.json()) as { openapi: string };
+        expect(body.openapi).toBe("3.1.0");
+    });
+
+    it("yaml endpoint returns application/yaml", {
+        timeout: 5000,
+    }, async () => {
+        const app = createOpenapiRouter({ emitter: buildEmitter() });
+        const res = await app.request("/openapi.yaml");
+        expect(res.status).toBe(200);
+        expect(res.headers.get("content-type")).toContain("application/yaml");
+        const body = await res.text();
+        const parsed = yamlParse(body) as { openapi: string };
+        expect(parsed.openapi).toBe("3.1.0");
+    });
+
+    it("docs index lists every plugin", { timeout: 5000 }, async () => {
+        const app = createOpenapiRouter({ emitter: buildEmitter() });
+        const res = await app.request("/docs");
+        expect(res.status).toBe(200);
+        expect(res.headers.get("content-type")).toContain("text/html");
+        const html = await res.text();
+        expect(html).toContain("billing");
+        expect(html).toContain("users");
+    });
+
+    it("filtered view excludes other plugins", { timeout: 5000 }, async () => {
+        const app = createOpenapiRouter({ emitter: buildEmitter() });
+        const res = await app.request("/docs/billing");
+        expect(res.status).toBe(200);
+        const html = await res.text();
+        expect(html).toContain("billing");
+        // The HTML stub shows only the requested plugin's name in the
+        // h1, but the spec also requires that the underlying filtered
+        // document contains no users routes — that is asserted in
+        // emitter.test.ts. Here we sanity-check the HTTP shape.
+    });
+
+    it("filtered view returns 404 for unknown plugin", {
+        timeout: 5000,
+    }, async () => {
+        const app = createOpenapiRouter({ emitter: buildEmitter() });
+        const res = await app.request("/docs/ghost");
+        expect(res.status).toBe(404);
+        const body = (await res.json()) as { code: string };
+        expect(body.code).toBe(OPENAPI_CODES.UNKNOWN_PLUGIN_IN_FILTER);
+    });
+
+    it("mountOpenapiEndpoints attaches to an existing app", {
+        timeout: 5000,
+    }, async () => {
+        const app = new Hono();
+        const out = mountOpenapiEndpoints(app, {
+            emitter: buildEmitter(),
+        });
+        expect(out).toBe(app);
+        const res = await app.request("/openapi.json");
+        expect(res.status).toBe(200);
+    });
+
+    it("unexpected errors propagate from the filtered handler", {
+        timeout: 5000,
+    }, async () => {
+        const emitter = buildEmitter();
+        // Wrap getDocumentForPlugin to throw a non-OpenAPIError.
+        const broken = {
+            ...emitter,
+            getDocumentForPlugin: () => {
+                throw new Error("kaboom");
+            },
+        };
+        const app = createOpenapiRouter({ emitter: broken });
+        const res = await app.request("/docs/billing");
+        expect(res.status).toBe(500);
+    });
+});

packages/api-stack/api/api-openapi/src/endpoints/endpoints.ts

@@ -0,0 +1,95 @@
+import { Hono } from "hono";
+import type { OpenapiEmitter } from "../emitter/emitter.js";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+
+/**
+ * Options accepted by {@link mountOpenapiEndpoints} and its sibling
+ * factories. The `emitter` is the single source of truth.
+ */
+export interface OpenapiEndpointsOptions {
+    readonly emitter: OpenapiEmitter;
+}
+
+/**
+ * Build the standalone Hono router that serves every OpenAPI endpoint:
+ *
+ *  - `GET /openapi.json` → JSON of the merged document.
+ *  - `GET /openapi.yaml` → YAML of the merged document.
+ *  - `GET /docs` → HTML stub linking to `/openapi.json` (UI sibling
+ *    packages mount richer renderers themselves).
+ *  - `GET /docs/:plugin` → per-plugin filtered HTML stub.
+ *
+ * The router is intentionally self-contained so the host can mount it
+ * at any path. Use {@link mountOpenapiEndpoints} to attach the router
+ * onto an existing Hono app.
+ */
+export function createOpenapiRouter(options: OpenapiEndpointsOptions): Hono {
+    const app = new Hono();
+    const { emitter } = options;
+
+    app.get("/openapi.json", (c) => {
+        c.header("Content-Type", "application/json");
+        return c.body(emitter.getJson());
+    });
+
+    app.get("/openapi.yaml", (c) => {
+        c.header("Content-Type", "application/yaml");
+        return c.body(emitter.getYaml());
+    });
+
+    app.get("/docs", (c) => {
+        c.header("Content-Type", "text/html; charset=utf-8");
+        return c.body(renderRootDocsHtml(emitter));
+    });
+
+    app.get("/docs/:plugin", (c) => {
+        const plugin = c.req.param("plugin");
+        try {
+            const doc = emitter.getDocumentForPlugin(plugin);
+            c.header("Content-Type", "text/html; charset=utf-8");
+            return c.body(renderPluginDocsHtml(plugin, doc.info.title));
+        } catch (err) {
+            if (
+                err instanceof OpenAPIError &&
+                err.code === OPENAPI_CODES.UNKNOWN_PLUGIN_IN_FILTER
+            ) {
+                c.header("Content-Type", "application/json");
+                return c.body(
+                    JSON.stringify({
+                        code: err.code,
+                        message: err.message,
+                    }),
+                    404
+                );
+            }
+            throw err;
+        }
+    });
+
+    return app;
+}
+
+/**
+ * Mount the OpenAPI endpoints onto an existing Hono app. Returns the
+ * passed app so callers can chain.
+ */
+export function mountOpenapiEndpoints<TApp extends Hono>(
+    app: TApp,
+    options: OpenapiEndpointsOptions
+): TApp {
+    app.route("/", createOpenapiRouter(options));
+    return app;
+}
+
+function renderRootDocsHtml(emitter: OpenapiEmitter): string {
+    const items = emitter
+        .getPluginNames()
+        .map((p) => `<li><a href="/docs/${p}">${p}</a></li>`)
+        .join("");
+    const title = emitter.getDocument().info.title;
+    return `<!doctype html><html><head><meta charset="utf-8"><title>${title} — OpenAPI</title></head><body><h1>${title}</h1><p><a href="/openapi.json">openapi.json</a> · <a href="/openapi.yaml">openapi.yaml</a></p><h2>Plugins</h2><ul>${items}</ul></body></html>`;
+}
+
+function renderPluginDocsHtml(plugin: string, hostTitle: string): string {
+    return `<!doctype html><html><head><meta charset="utf-8"><title>${hostTitle} — ${plugin}</title></head><body><h1>${plugin}</h1><p><a href="/openapi.json">full openapi.json</a></p></body></html>`;
+}

packages/api-stack/api/api-openapi/src/endpoints/index.ts

@@ -0,0 +1,5 @@
+export {
+    createOpenapiRouter,
+    mountOpenapiEndpoints,
+    type OpenapiEndpointsOptions,
+} from "./endpoints.js";

packages/api-stack/api/api-openapi/src/error-codes/error-codes.md

@@ -0,0 +1,84 @@
+# error-codes
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Defines the stable error-code registry and typed error class for
+`@suaveplan/api-openapi`. Every public failure path in the package raises
+an `OpenAPIError` carrying one of the three `OPENAPI.*` codes, allowing
+downstream consumers to branch on `error.code` for recovery, telemetry,
+or user-facing message rendering. The registry is frozen at module load
+so codes cannot be added or mutated at runtime, which keeps the wire
+contract stable across versions.
+
+The package intentionally exposes a small, deliberate code surface —
+this is an OpenAPI document builder, not a request validator, so most
+failure modes are caller-error rather than runtime-error. Three codes
+cover the entire surface.
+
+## Features
+
+- Frozen `OPENAPI_CODES` const map produced by `defineCodes("OPENAPI", …)`.
+- `OpenAPIErrorCode` discriminated string-literal union.
+- `OpenAPIError` subclass of `SuaveplanError` with public constructor,
+  redundant `openapiCode` field for symmetric narrowing, and full
+  `cause` / `context` / `requestId` propagation.
+
+## Usage: Basic
+
+```ts
+import { OPENAPI_CODES, OpenAPIError } from "@suaveplan/api-openapi/error-codes";
+
+throw new OpenAPIError(
+    OPENAPI_CODES.SCHEMA_NOT_FOUND,
+    `schema "${name}" is not registered`
+);
+```
+
+## Usage: Advanced
+
+```ts
+import { OPENAPI_CODES, OpenAPIError } from "@suaveplan/api-openapi/error-codes";
+
+try {
+    registry.extend("User", "UserPublic", { exposedAt: z.string() });
+} catch (e) {
+    if (e instanceof OpenAPIError && e.code === OPENAPI_CODES.INVALID_BASE_SCHEMA) {
+        // The base name resolved to a non-ZodObject. Re-throw with
+        // a richer context so the caller knows which schema failed.
+        throw new OpenAPIError(e.code, e.message, {
+            cause: e,
+            context: { baseName: "User", attemptedExtension: "UserPublic" },
+        });
+    }
+    throw e;
+}
+```
+
+## API Reference
+
+- `OPENAPI_CODES` — frozen `{ INVALID_INPUT, SCHEMA_NOT_FOUND, INVALID_BASE_SCHEMA }` mapping local keys to `"OPENAPI.*"` wire codes.
+- `type OpenAPIErrorCode` — union of the three wire codes.
+- `class OpenAPIError extends SuaveplanError<OpenAPIErrorCode>` — public constructor `(code, message, options?)`, mirrors code in `.openapiCode`.
+
+## Implementation Notes
+
+The registry deliberately defines exactly three codes — adding new ones
+without bumping a major and updating consumers risks silent gaps in
+downstream error branches. New failure modes should either map onto one
+of the existing codes or be added in a coordinated change covered by an
+OpenSpec delta.
+
+`OPENAPI.INVALID_BASE_SCHEMA` is the one behavioural divergence from
+upstream `@suaveplan/api`'s schema-registry — upstream silently returned
+`undefined` from `extend`/`partial`/`pick`/`omit` when the base was not
+a `ZodObject`. We raise so the caller learns why the derivation failed,
+which removes a class of "schema mysteriously missing" bugs that were
+near-impossible to diagnose in upstream.
+
+The class is side-effect-imported by the package root barrel
+(`src/index.ts`) so consumers picking up `@suaveplan/api-openapi`
+surface the code registry without depending on a sub-export path.

packages/api-stack/api/api-openapi/src/error-codes/error-codes.test.ts

@@ -0,0 +1,68 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { OPENAPI_CODES, OpenAPIError } from "./error-codes.js";
+
+describe("OPENAPI_CODES", () => {
+    it("defines exactly 7 codes", { timeout: 5000 }, () => {
+        expect(Object.keys(OPENAPI_CODES)).toHaveLength(7);
+    });
+
+    it("namespaces every code under OPENAPI.*", { timeout: 5000 }, () => {
+        for (const value of Object.values(OPENAPI_CODES)) {
+            expect(value.startsWith("OPENAPI.")).toBe(true);
+        }
+    });
+
+    it("freezes the registry", { timeout: 5000 }, () => {
+        expect(Object.isFrozen(OPENAPI_CODES)).toBe(true);
+    });
+
+    it("exposes every documented code", { timeout: 5000 }, () => {
+        expect(OPENAPI_CODES.INVALID_INPUT).toBe("OPENAPI.INVALID_INPUT");
+        expect(OPENAPI_CODES.SCHEMA_NOT_FOUND).toBe("OPENAPI.SCHEMA_NOT_FOUND");
+        expect(OPENAPI_CODES.INVALID_BASE_SCHEMA).toBe(
+            "OPENAPI.INVALID_BASE_SCHEMA"
+        );
+        expect(OPENAPI_CODES.MISSING_SCHEMA).toBe("OPENAPI.MISSING_SCHEMA");
+        expect(OPENAPI_CODES.SCHEMA_CONVERSION_FAILED).toBe(
+            "OPENAPI.SCHEMA_CONVERSION_FAILED"
+        );
+        expect(OPENAPI_CODES.OPERATION_ID_COLLISION).toBe(
+            "OPENAPI.OPERATION_ID_COLLISION"
+        );
+        expect(OPENAPI_CODES.UNKNOWN_PLUGIN_IN_FILTER).toBe(
+            "OPENAPI.UNKNOWN_PLUGIN_IN_FILTER"
+        );
+    });
+});
+
+describe("OpenAPIError", () => {
+    it("carries the code via .code and .openapiCode", { timeout: 5000 }, () => {
+        const err = new OpenAPIError(OPENAPI_CODES.SCHEMA_NOT_FOUND, "missing");
+        expect(err.code).toBe("OPENAPI.SCHEMA_NOT_FOUND");
+        expect(err.openapiCode).toBe("OPENAPI.SCHEMA_NOT_FOUND");
+    });
+
+    it("preserves the message and context", { timeout: 5000 }, () => {
+        const err = new OpenAPIError(OPENAPI_CODES.INVALID_INPUT, "boom", {
+            context: { name: "User" },
+        });
+        expect(err.message).toBe("boom");
+        expect(err.context).toEqual({ name: "User" });
+    });
+
+    it("threads cause through to Error.cause", { timeout: 5000 }, () => {
+        const cause = new Error("inner");
+        const err = new OpenAPIError(
+            OPENAPI_CODES.INVALID_BASE_SCHEMA,
+            "outer",
+            { cause }
+        );
+        expect(err.cause).toBe(cause);
+    });
+
+    it("is an Error subclass with a stable name", { timeout: 5000 }, () => {
+        const err = new OpenAPIError(OPENAPI_CODES.INVALID_INPUT, "x");
+        expect(err).toBeInstanceOf(Error);
+        expect(err.name).toBe("OpenAPIError");
+    });
+});

packages/api-stack/api/api-openapi/src/error-codes/error-codes.ts

@@ -0,0 +1,57 @@
+import type { SuaveplanErrorOptions } from "@suaveplan/error";
+import { defineCodes, SuaveplanError } from "@suaveplan/error";
+
+/**
+ * Stable error-code registry for `@suaveplan/api-openapi`.
+ *
+ * Every public failure path raises an {@link OpenAPIError} carrying one of
+ * these namespaced `OPENAPI.*` codes:
+ *
+ *  - `INVALID_INPUT` — caller passed structurally invalid arguments
+ *    (e.g. a non-Zod value into a builder method that accepts schemas).
+ *  - `SCHEMA_NOT_FOUND` — a derivation helper (`extend`/`partial`/`pick`/
+ *    `omit`) referenced a base schema name that has not been registered.
+ *  - `INVALID_BASE_SCHEMA` — the base schema referenced exists but is
+ *    not a `ZodObject`.
+ *  - `MISSING_SCHEMA` — a route has no request or response schema and
+ *    the emitter is configured with strictness `"refuse-install"`.
+ *  - `SCHEMA_CONVERSION_FAILED` — `@asteasolutions/zod-to-openapi` (or
+ *    the host's Zod-to-OAS bridge) raised when converting a registered
+ *    schema to an OpenAPI schema object.
+ *  - `OPERATION_ID_COLLISION` — two routes emit the same `operationId`
+ *    after namespacing (`<plugin>.<method>.<path>`).
+ *  - `UNKNOWN_PLUGIN_IN_FILTER` — the per-plugin filtered docs view
+ *    (`GET /docs/{plugin}`) was requested for a plugin not registered
+ *    with the emitter.
+ */
+export const OPENAPI_CODES = defineCodes("OPENAPI", [
+    "INVALID_INPUT",
+    "SCHEMA_NOT_FOUND",
+    "INVALID_BASE_SCHEMA",
+    "MISSING_SCHEMA",
+    "SCHEMA_CONVERSION_FAILED",
+    "OPERATION_ID_COLLISION",
+    "UNKNOWN_PLUGIN_IN_FILTER",
+] as const);
+
+export type OpenAPIErrorCode =
+    (typeof OPENAPI_CODES)[keyof typeof OPENAPI_CODES];
+
+/**
+ * Concrete error class for the api-openapi package. Extends
+ * {@link SuaveplanError} so `instanceof OpenAPIError` narrows `code` to
+ * {@link OpenAPIErrorCode}. The constructor is widened to `public` so
+ * callers may construct errors directly.
+ */
+export class OpenAPIError extends SuaveplanError<OpenAPIErrorCode> {
+    public readonly openapiCode: OpenAPIErrorCode;
+
+    public constructor(
+        code: OpenAPIErrorCode,
+        message: string,
+        options?: SuaveplanErrorOptions
+    ) {
+        super(code, message, options);
+        this.openapiCode = code;
+    }
+}

packages/api-stack/api/api-openapi/src/error-codes/index.ts

@@ -0,0 +1,5 @@
+export type { OpenAPIErrorCode } from "./error-codes.js";
+export {
+    OPENAPI_CODES,
+    OpenAPIError,
+} from "./error-codes.js";

packages/api-stack/api/api-openapi/src/index.ts

@@ -0,0 +1,118 @@
+// Side-effect import — surfaces error-codes registry on bare
+// `import "@suaveplan/api-openapi"`.
+import "./error-codes/error-codes.js";
+
+// Emitter
+export {
+    __resetEmitterCounters,
+    CONVERSION_ERROR_COUNTER_NAME,
+    type CreateOpenapiEmitterInput,
+    createOpenapiEmitter,
+    EMISSION_COUNTER_NAME,
+    type EmitterAuthAdapter,
+    type EmitterHostConfig,
+    type EmitterPluginManifest,
+    type EmitterRouteInput,
+    type OpenapiEmitter,
+} from "./emitter/emitter.js";
+// Endpoints
+export {
+    createOpenapiRouter,
+    mountOpenapiEndpoints,
+    type OpenapiEndpointsOptions,
+} from "./endpoints/endpoints.js";
+// Error codes
+export {
+    OPENAPI_CODES,
+    OpenAPIError,
+    type OpenAPIErrorCode,
+} from "./error-codes/error-codes.js";
+// Merger
+export {
+    extractOpenAPIDoc,
+    filterPathsByTag,
+    type MergeOptions,
+    mergeOpenAPIDocuments,
+    prefixPaths,
+    removeInternalRoutes,
+} from "./merger/merger.js";
+// Namespacing
+export {
+    assignOperationIds,
+    componentPrefix,
+    type NamespacedRoute,
+    type NamespacedRouteInput,
+    type NamespacePluginInfo,
+    normaliseRoutePath,
+    operationIdFor,
+    tagFor,
+} from "./namespacing/namespacing.js";
+// Plugin integration
+export {
+    type DefinePluginRoutesOptions,
+    definePluginRoutes,
+    type PluginRouteEntry,
+    type RouteHandler,
+} from "./plugin-integration/plugin-integration.js";
+// Registry
+export {
+    ApiKeyScheme,
+    BearerAuthScheme,
+    createOpenAPIRegistry,
+    DEFAULT_SPEC_PATH,
+    OpenAPIRegistry,
+    type OpenAPIRegistryOptions,
+} from "./registry/registry.js";
+// Route factory
+export {
+    DELETE,
+    type ErrorResponse,
+    ErrorResponseSchema,
+    errorResponse,
+    GET,
+    PATCH,
+    POST,
+    PUT,
+    paginatedResponse,
+    RouteBuilder,
+    type RouteMethod,
+    type RouteOptions,
+    route,
+    StandardResponses,
+    successResponse,
+    type TypedRouteConfig,
+} from "./route-factory/route-factory.js";
+// Schema registry
+export { CommonSchemas } from "./schema-registry/common-schemas.js";
+export {
+    createSchemaRegistry,
+    defineSchema,
+    SchemaRegistry,
+} from "./schema-registry/schema-registry.js";
+// Strictness
+export {
+    __resetMissingSchemaCounter,
+    getMissingSchemaCounter,
+    type HostEnvironment,
+    MISSING_SCHEMA_COUNTER_NAME,
+    type MissingSchemaSlot,
+    OPENAPI_METER_NAME,
+    type ReportMissingSchemaInput,
+    type ResolveStrictnessInput,
+    reportMissingSchema,
+    resolveStrictness,
+    type StrictnessMode,
+} from "./strictness/strictness.js";
+
+// Types
+export {
+    HTTP_METHODS,
+    type HttpMethod,
+    type OpenAPIDocument,
+    type OpenAPIInfo,
+    type OpenAPIServer,
+    type Operation,
+    type PathItem,
+    type RegisteredRoute,
+    type SecurityScheme,
+} from "./types/openapi.js";

packages/api-stack/api/api-openapi/src/merger/index.ts

@@ -0,0 +1,8 @@
+export type { MergeOptions } from "./merger.js";
+export {
+    extractOpenAPIDoc,
+    filterPathsByTag,
+    mergeOpenAPIDocuments,
+    prefixPaths,
+    removeInternalRoutes,
+} from "./merger.js";

packages/api-stack/api/api-openapi/src/merger/merger.md

@@ -0,0 +1,123 @@
+# merger
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+OpenAPI document transforms — merge, prefix, filter, redact internal
+routes. Multi-plugin servers compose the final published spec from
+multiple sources (the registry's `buildDocument()`, the Hono
+`getOpenAPI31Document()` output, hand-crafted addon docs), and the
+merger is the deterministic operation that combines them without
+losing information or producing collisions silently.
+
+Every transform returns a new document — the inputs are never mutated —
+so consumers can pipeline `prefixPaths(removeInternalRoutes(merge(...)))`
+without worrying about aliasing.
+
+## Features
+
+- `mergeOpenAPIDocuments(base, ...docs)` — per-path-item path merge,
+  spread-merge of components, dedup tags by name, concat servers.
+- `prefixPaths(doc, prefix)` — prepends a prefix to every path,
+  collapsing duplicate slashes so `prefix="/api/"` + `path="/users"`
+  yields `/api/users`.
+- `filterPathsByTag(doc, tags[])` — keeps only operations whose `tags`
+  array intersects the supplied list.
+- `removeInternalRoutes(doc)` — drops operations marked `x-internal: true`.
+- `extractOpenAPIDoc(app, info)` — pulls a fully-rendered document out
+  of a Hono `OpenAPIHono` for inspection or merging.
+
+## Usage: Basic
+
+```ts
+import {
+    mergeOpenAPIDocuments,
+} from "@suaveplan/api-openapi/merger";
+
+const base: OpenAPIDocument = {
+    openapi: "3.1.0",
+    info: { title: "Combined", version: "1.0.0" },
+    paths: { "/a": { get: { responses: {} } } },
+};
+const addon: Partial<OpenAPIDocument> = {
+    paths: { "/b": { post: { responses: {} } } },
+};
+const merged = mergeOpenAPIDocuments(base, addon);
+console.log(Object.keys(merged.paths)); // ["/a", "/b"]
+```
+
+## Usage: Advanced
+
+```ts
+import {
+    extractOpenAPIDoc,
+    filterPathsByTag,
+    mergeOpenAPIDocuments,
+    prefixPaths,
+    removeInternalRoutes,
+} from "@suaveplan/api-openapi/merger";
+import { OpenAPIHono } from "@hono/zod-openapi";
+
+const usersApp = new OpenAPIHono();
+const projectsApp = new OpenAPIHono();
+// … register routes …
+
+const usersDoc = extractOpenAPIDoc(usersApp, {
+    title: "Users",
+    version: "1.0.0",
+});
+const projectsDoc = extractOpenAPIDoc(projectsApp, {
+    title: "Projects",
+    version: "1.0.0",
+});
+
+const merged = mergeOpenAPIDocuments(
+    { openapi: "3.1.0", info: { title: "Public API", version: "1.0.0" }, paths: {} },
+    prefixPaths(usersDoc, "/v1"),
+    prefixPaths(projectsDoc, "/v1")
+);
+
+// Hide internal endpoints + restrict to public-facing tags.
+const publicDoc = filterPathsByTag(
+    removeInternalRoutes(merged),
+    ["users", "projects"]
+);
+```
+
+## API Reference
+
+- `function mergeOpenAPIDocuments(base, ...docs): OpenAPIDocument`
+- `function prefixPaths(doc, prefix): OpenAPIDocument`
+- `function extractOpenAPIDoc(app, info): OpenAPIDocument`
+- `function filterPathsByTag(doc, tags[]): OpenAPIDocument`
+- `function removeInternalRoutes(doc): OpenAPIDocument`
+- `interface MergeOptions { pathPrefix?: string; overridePaths?: boolean }` — reserved for future use.
+
+## Implementation Notes
+
+`mergeOpenAPIDocuments` is left-associative — merging `(a, b, c)` is the
+same as `merge(merge(a, b), c)`. This property is asserted under
+fast-check at 200 runs in `tests/property.test.ts`, ensuring the merger
+remains a monoid even as future spread-rules land.
+
+`mergeOpenAPIDocuments` does **not** detect cross-document collisions
+on the same `(method, path)`. The last value wins. That is the intended
+upstream behaviour and the only reasonable default — strict-detection
+mode is reserved for a follow-up.
+
+`prefixPaths` uses `String.replace(/\/+/g, "/")` to collapse duplicate
+slashes. This is the only place double-slashes can be introduced (the
+prefix `/api/` plus path `/users` would yield `/api//users` without
+collapse). The transform is idempotent: applying it twice with the same
+prefix yields the same paths.
+
+`filterPathsByTag` drops paths whose every operation is removed,
+preventing empty `PathItem` shells in the result. `removeInternalRoutes`
+applies the same rule for `x-internal`.
+
+The transforms intentionally do not validate the input documents — they
+treat the input as best-effort structural data. Validation belongs to a
+separate spec-validator package (out of scope here).

packages/api-stack/api/api-openapi/src/merger/merger.test.ts

@@ -0,0 +1,233 @@
+import { OpenAPIHono } from "@hono/zod-openapi";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { OpenAPIDocument } from "../types/openapi.js";
+import {
+    extractOpenAPIDoc,
+    filterPathsByTag,
+    mergeOpenAPIDocuments,
+    prefixPaths,
+    removeInternalRoutes,
+} from "./merger.js";
+
+const baseDoc = (): OpenAPIDocument => ({
+    openapi: "3.1.0",
+    info: { title: "T", version: "1.0.0" },
+    paths: { "/a": { get: { responses: { "200": { description: "ok" } } } } },
+    tags: [{ name: "alpha" }],
+});
+
+describe("mergeOpenAPIDocuments", () => {
+    it("merge composes paths", { timeout: 5000 }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            paths: {
+                "/b": { post: { responses: {} } },
+            },
+        });
+        expect(Object.keys(merged.paths).sort()).toEqual(["/a", "/b"]);
+    });
+
+    it("colliding paths union their methods", { timeout: 5000 }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            paths: { "/a": { post: { responses: {} } } },
+        });
+        expect(merged.paths["/a"]?.get).toBeDefined();
+        expect(merged.paths["/a"]?.post).toBeDefined();
+    });
+
+    it("colliding methods — last write wins", { timeout: 5000 }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            paths: {
+                "/a": {
+                    get: { responses: { "200": { description: "B" } } },
+                },
+            },
+        });
+        const responses = merged.paths["/a"]?.get?.responses as Record<
+            string,
+            { description: string }
+        >;
+        expect(responses["200"]?.description).toBe("B");
+    });
+
+    it("dedups tags by name", { timeout: 5000 }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            tags: [{ name: "alpha" }, { name: "beta" }],
+        });
+        expect(merged.tags?.map((t) => t.name).sort()).toEqual([
+            "alpha",
+            "beta",
+        ]);
+    });
+
+    it("spread-merges components", { timeout: 5000 }, () => {
+        const base = {
+            ...baseDoc(),
+            components: { schemas: { User: { type: "object" } } },
+        };
+        const merged = mergeOpenAPIDocuments(base, {
+            components: {
+                schemas: { Project: { type: "object" } },
+                securitySchemes: { Bearer: { type: "http" } },
+                parameters: { idParam: {} },
+                responses: { default: {} },
+            },
+        });
+        expect(merged.components?.schemas).toMatchObject({
+            User: { type: "object" },
+            Project: { type: "object" },
+        });
+        expect(merged.components?.securitySchemes).toMatchObject({
+            Bearer: { type: "http" },
+        });
+        expect(merged.components?.parameters?.["idParam"]).toBeDefined();
+        expect(merged.components?.responses?.["default"]).toBeDefined();
+    });
+
+    it("concats servers from add-on docs", { timeout: 5000 }, () => {
+        const base = { ...baseDoc(), servers: [{ url: "https://a" }] };
+        const merged = mergeOpenAPIDocuments(base, {
+            servers: [{ url: "https://b" }],
+        });
+        expect(merged.servers?.map((s) => s.url).sort()).toEqual([
+            "https://a",
+            "https://b",
+        ]);
+    });
+
+    it("works without components on base", { timeout: 5000 }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            components: { schemas: { X: {} } },
+        });
+        expect(merged.components?.schemas?.["X"]).toBeDefined();
+    });
+
+    it("doc.components with only securitySchemes (no other sub-keys)", {
+        timeout: 5000,
+    }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            components: { securitySchemes: { Bearer: { type: "http" } } },
+        });
+        expect(merged.components?.securitySchemes).toMatchObject({
+            Bearer: { type: "http" },
+        });
+        expect(merged.components?.schemas).toEqual({});
+    });
+
+    it("doc.servers merges into a base without servers", {
+        timeout: 5000,
+    }, () => {
+        const merged = mergeOpenAPIDocuments(baseDoc(), {
+            servers: [{ url: "https://only" }],
+        });
+        expect(merged.servers?.map((s) => s.url)).toEqual(["https://only"]);
+    });
+
+    it("merging with no docs returns a clone with identical paths/info/tags", {
+        timeout: 5000,
+    }, () => {
+        const b = baseDoc();
+        const m = mergeOpenAPIDocuments(b);
+        expect(m).not.toBe(b);
+        expect(m.paths).toEqual(b.paths);
+        expect(m.info).toEqual(b.info);
+        expect(m.tags).toEqual(b.tags);
+    });
+});
+
+describe("prefixPaths", () => {
+    it("prefix collapses double slashes", { timeout: 5000 }, () => {
+        const out = prefixPaths(baseDoc(), "/api/");
+        expect(Object.keys(out.paths)).toEqual(["/api/a"]);
+    });
+
+    it("prefix without trailing slash", { timeout: 5000 }, () => {
+        const out = prefixPaths(baseDoc(), "/v1");
+        expect(Object.keys(out.paths)).toEqual(["/v1/a"]);
+    });
+});
+
+describe("filterPathsByTag", () => {
+    it("keeps tag-intersecting ops", { timeout: 5000 }, () => {
+        const doc: OpenAPIDocument = {
+            openapi: "3.1.0",
+            info: { title: "T", version: "1.0.0" },
+            paths: {
+                "/a": {
+                    get: { responses: {}, tags: ["alpha"] },
+                    post: { responses: {}, tags: ["beta"] },
+                },
+                "/b": { get: { responses: {}, tags: ["beta"] } },
+            },
+            tags: [{ name: "alpha" }, { name: "beta" }],
+        };
+        const out = filterPathsByTag(doc, ["alpha"]);
+        expect(out.paths["/a"]?.get).toBeDefined();
+        expect(out.paths["/a"]?.post).toBeUndefined();
+        expect(out.paths["/b"]).toBeUndefined();
+        expect(out.tags?.map((t) => t.name)).toEqual(["alpha"]);
+    });
+
+    it("drops the tags array gracefully when absent", {
+        timeout: 5000,
+    }, () => {
+        const doc: OpenAPIDocument = {
+            openapi: "3.1.0",
+            info: { title: "T", version: "1.0.0" },
+            paths: { "/a": { get: { responses: {}, tags: ["x"] } } },
+        };
+        const out = filterPathsByTag(doc, ["x"]);
+        expect(out.paths["/a"]).toBeDefined();
+        expect(out.tags).toBeUndefined();
+    });
+});
+
+describe("removeInternalRoutes", () => {
+    it("drops x-internal: true", { timeout: 5000 }, () => {
+        const doc: OpenAPIDocument = {
+            openapi: "3.1.0",
+            info: { title: "T", version: "1.0.0" },
+            paths: {
+                "/pub": { get: { responses: {} } },
+                "/int": {
+                    get: {
+                        responses: {},
+                        ["x-internal" as `x-${string}`]: true,
+                    },
+                },
+            },
+        };
+        const out = removeInternalRoutes(doc);
+        expect(out.paths["/pub"]).toBeDefined();
+        expect(out.paths["/int"]).toBeUndefined();
+    });
+
+    it("keeps non-internal methods even when sibling is internal", {
+        timeout: 5000,
+    }, () => {
+        const doc: OpenAPIDocument = {
+            openapi: "3.1.0",
+            info: { title: "T", version: "1.0.0" },
+            paths: {
+                "/x": {
+                    get: { responses: {} },
+                    post: {
+                        responses: {},
+                        ["x-internal" as `x-${string}`]: true,
+                    },
+                },
+            },
+        };
+        const out = removeInternalRoutes(doc);
+        expect(out.paths["/x"]?.get).toBeDefined();
+        expect(out.paths["/x"]?.post).toBeUndefined();
+    });
+});
+
+describe("extractOpenAPIDoc", () => {
+    it("extracts a doc from a Hono app", { timeout: 5000 }, () => {
+        const app = new OpenAPIHono();
+        const doc = extractOpenAPIDoc(app, { title: "X", version: "1.0.0" });
+        expect(doc.openapi).toBe("3.1.0");
+        expect(doc.info.title).toBe("X");
+    });
+});

packages/api-stack/api/api-openapi/src/merger/merger.ts

@@ -0,0 +1,189 @@
+import type { OpenAPIHono } from "@hono/zod-openapi";
+import {
+    HTTP_METHODS,
+    type OpenAPIDocument,
+    type Operation,
+    type PathItem,
+} from "../types/openapi.js";
+
+/**
+ * Optional merge controls accepted by {@link mergeOpenAPIDocuments}.
+ */
+export interface MergeOptions {
+    /** Prefix prepended to every path being merged in. */
+    pathPrefix?: string;
+    /** Last-write-wins behaviour on path-method collisions. */
+    overridePaths?: boolean;
+}
+
+/**
+ * Merge `base` with one or more partial documents.
+ *
+ * - Paths merge per-path-item — colliding paths concatenate their
+ *   method maps (collisions on the same method keep the latest entry).
+ * - Components spread-merge across schemas / securitySchemes /
+ *   parameters / responses.
+ * - Tags deduplicate by name (first occurrence wins).
+ * - Servers carry through the base; partial servers concatenate.
+ */
+export function mergeOpenAPIDocuments(
+    base: OpenAPIDocument,
+    ...docs: Array<Partial<OpenAPIDocument>>
+): OpenAPIDocument {
+    const baseComponents = base.components ?? {};
+    const merged: OpenAPIDocument = {
+        ...base,
+        paths: { ...base.paths },
+        components: {
+            schemas: { ...baseComponents.schemas },
+            securitySchemes: { ...baseComponents.securitySchemes },
+            parameters: { ...baseComponents.parameters },
+            responses: { ...baseComponents.responses },
+        },
+        tags: base.tags ? [...base.tags] : [],
+        ...(base.servers ? { servers: [...base.servers] } : {}),
+    };
+
+    for (const doc of docs) {
+        if (doc.paths) {
+            for (const [path, pathItem] of Object.entries(doc.paths)) {
+                const existing = merged.paths[path];
+                merged.paths[path] = existing
+                    ? { ...existing, ...pathItem }
+                    : { ...pathItem };
+            }
+        }
+
+        if (doc.components) {
+            const dst = merged.components as NonNullable<
+                OpenAPIDocument["components"]
+            >;
+            if (doc.components.schemas) {
+                dst.schemas = { ...dst.schemas, ...doc.components.schemas };
+            }
+            if (doc.components.securitySchemes) {
+                dst.securitySchemes = {
+                    ...dst.securitySchemes,
+                    ...doc.components.securitySchemes,
+                };
+            }
+            if (doc.components.parameters) {
+                dst.parameters = {
+                    ...dst.parameters,
+                    ...doc.components.parameters,
+                };
+            }
+            if (doc.components.responses) {
+                dst.responses = {
+                    ...dst.responses,
+                    ...doc.components.responses,
+                };
+            }
+        }
+
+        if (doc.tags) {
+            const tags = (merged.tags ??= []);
+            const seen = new Set(tags.map((t) => t.name));
+            for (const tag of doc.tags) {
+                if (!seen.has(tag.name)) {
+                    tags.push(tag);
+                    seen.add(tag.name);
+                }
+            }
+        }
+
+        if (doc.servers) {
+            merged.servers = [...(merged.servers ?? []), ...doc.servers];
+        }
+    }
+
+    return merged;
+}
+
+/**
+ * Prepend `prefix` to every path in `doc`, collapsing duplicate
+ * slashes. The original document is returned unchanged.
+ */
+export function prefixPaths(
+    doc: OpenAPIDocument,
+    prefix: string
+): OpenAPIDocument {
+    const prefixed: Record<string, PathItem> = {};
+    for (const [path, pathItem] of Object.entries(doc.paths)) {
+        const next = `${prefix}${path}`.replace(/\/+/g, "/");
+        prefixed[next] = pathItem;
+    }
+    return { ...doc, paths: prefixed };
+}
+
+/**
+ * Extract a registry-shaped OpenAPI document from a Hono `OpenAPIHono`
+ * instance. Useful for tests that want to compare what Hono would emit
+ * against what the registry emits.
+ */
+export function extractOpenAPIDoc(
+    app: OpenAPIHono,
+    info: { title: string; version: string }
+): OpenAPIDocument {
+    return app.getOpenAPI31Document({
+        openapi: "3.1.0",
+        info,
+    }) as OpenAPIDocument;
+}
+
+/**
+ * Keep only operations whose `tags` intersect `tags`. Paths whose every
+ * operation is filtered out are dropped. The document-level `tags`
+ * array is filtered to the same set.
+ */
+export function filterPathsByTag(
+    doc: OpenAPIDocument,
+    tags: string[]
+): OpenAPIDocument {
+    const tagSet = new Set(tags);
+    const filtered: Record<string, PathItem> = {};
+
+    for (const [path, pathItem] of Object.entries(doc.paths)) {
+        const kept: PathItem = {};
+        for (const method of HTTP_METHODS) {
+            const op = pathItem[method];
+            if (op?.tags?.some((t) => tagSet.has(t))) {
+                kept[method] = op;
+            }
+        }
+        if (Object.keys(kept).length > 0) {
+            filtered[path] = kept;
+        }
+    }
+
+    return {
+        ...doc,
+        paths: filtered,
+        ...(doc.tags
+            ? { tags: doc.tags.filter((t) => tagSet.has(t.name)) }
+            : {}),
+    };
+}
+
+/**
+ * Drop every operation marked `x-internal: true`. Paths whose entire
+ * method map is removed are dropped from the result.
+ */
+export function removeInternalRoutes(doc: OpenAPIDocument): OpenAPIDocument {
+    const out: Record<string, PathItem> = {};
+    for (const [path, pathItem] of Object.entries(doc.paths)) {
+        const kept: PathItem = {};
+        for (const method of HTTP_METHODS) {
+            const op = pathItem[method] as
+                | (Operation & { "x-internal"?: boolean })
+                | undefined;
+            if (op && op["x-internal"] !== true) {
+                kept[method] = op;
+            }
+        }
+        if (Object.keys(kept).length > 0) {
+            out[path] = kept;
+        }
+    }
+    return { ...doc, paths: out };
+}

packages/api-stack/api/api-openapi/src/namespacing/index.ts

@@ -0,0 +1,10 @@
+export {
+    assignOperationIds,
+    componentPrefix,
+    type NamespacedRoute,
+    type NamespacedRouteInput,
+    type NamespacePluginInfo,
+    normaliseRoutePath,
+    operationIdFor,
+    tagFor,
+} from "./namespacing.js";

packages/api-stack/api/api-openapi/src/namespacing/namespacing.md

@@ -0,0 +1,89 @@
+# namespacing
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+The `namespacing` module turns a plugin's structural identity (`name`,
+`displayName`) plus a registered route's `(method, path)` tuple into the
+deterministic OpenAPI surface fields — tag name, component-schema
+prefix, normalised OAS path, and `operationId`. It is the bridge between
+the plugin-namespaced runtime and the single merged OpenAPI 3.1
+document `@suaveplan/api-openapi` emits.
+
+Determinism matters: clients regenerate SDKs against the document and
+expect stable `operationId`s across boots. Collisions — two plugins
+producing the same id — would silently overwrite the earlier route in
+client toolchains, so the module raises `OPENAPI.OPERATION_ID_COLLISION`
+the moment a duplicate appears.
+
+## Features
+
+- `tagFor(plugin)` — prefers `displayName`, falls back to `name`.
+- `componentPrefix(plugin)` — `<pluginName>` literal, used by the
+  emitter as the prefix for `components.schemas` entries.
+- `normaliseRoutePath(path)` — rewrites Express-style `:id` parameters
+  into the OAS `{id}` form. Idempotent.
+- `operationIdFor(plugin, method, path)` — full deterministic id:
+  `<plugin>.<method>.<oasPath>`.
+- `assignOperationIds(inputs)` — bulk walk that respects pre-set
+  `operationId` values and raises a typed error on collision.
+
+## Usage: Basic
+
+```ts
+import {
+    assignOperationIds,
+    operationIdFor,
+    tagFor,
+} from "@suaveplan/api-openapi/namespacing";
+
+const plugin = { name: "billing", displayName: "Billing" };
+operationIdFor(plugin, "GET", "/invoices/:id");
+// => "billing.get./invoices/{id}"
+tagFor(plugin); // => "Billing"
+```
+
+## Usage: Advanced
+
+```ts
+import { assignOperationIds } from "@suaveplan/api-openapi/namespacing";
+import type { RegisteredRoute } from "@suaveplan/api-openapi/types";
+
+const plugins = [
+    { name: "billing", displayName: "Billing" },
+    { name: "users" },
+];
+const routes: ReadonlyArray<{
+    plugin: (typeof plugins)[number];
+    route: RegisteredRoute;
+}> = [
+    { plugin: plugins[0]!, route: { method: "GET", path: "/invoices/:id", tags: [] } },
+    { plugin: plugins[1]!, route: { method: "GET", path: "/users/:id", tags: [] } },
+];
+const namespaced = assignOperationIds(routes);
+// Throws OPENAPI.OPERATION_ID_COLLISION if any duplicate appears.
+```
+
+## API Reference
+
+- `NamespacePluginInfo` — `{ name, displayName? }`.
+- `tagFor(plugin) → string`.
+- `componentPrefix(plugin) → string`.
+- `normaliseRoutePath(path: string) → string`.
+- `operationIdFor(plugin, method, path) → string`.
+- `assignOperationIds(inputs) → NamespacedRoute[]`.
+- `NamespacedRoute` — `{ pluginName, tag, operationId, method, path, route }`.
+
+## Implementation Notes
+
+- Path normalisation uses the regex `:([A-Za-z_][\w-]*)` so colons
+  preceded by non-identifier characters (e.g. `:443` in a server URL)
+  are not rewritten.
+- Method is lower-cased to match OAS path-item key casing.
+- Pre-set `operationId` overrides the derived one — useful for stable
+  ids that pre-date the convention. Collisions still raise.
+- The module does not know about strictness; the emitter applies
+  strictness to missing schemas separately.

packages/api-stack/api/api-openapi/src/namespacing/namespacing.test.ts

@@ -0,0 +1,136 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import type { RegisteredRoute } from "../types/openapi.js";
+import {
+    assignOperationIds,
+    componentPrefix,
+    normaliseRoutePath,
+    operationIdFor,
+    tagFor,
+} from "./namespacing.js";
+
+const billing = { name: "billing", displayName: "Billing" } as const;
+const users = { name: "users" } as const;
+
+function route(
+    method: string,
+    path: string,
+    extra: Partial<RegisteredRoute> = {}
+): RegisteredRoute {
+    return { method, path, tags: [], ...extra };
+}
+
+describe("namespacing — tagFor / componentPrefix / normaliseRoutePath", () => {
+    it("tagFor prefers displayName", { timeout: 5000 }, () => {
+        expect(tagFor(billing)).toBe("Billing");
+    });
+
+    it("tagFor falls back to name when displayName absent", {
+        timeout: 5000,
+    }, () => {
+        expect(tagFor(users)).toBe("users");
+    });
+
+    it("componentPrefix returns plugin name", { timeout: 5000 }, () => {
+        expect(componentPrefix(billing)).toBe("billing");
+    });
+
+    it("normaliseRoutePath rewrites :params to {params}", {
+        timeout: 5000,
+    }, () => {
+        expect(normaliseRoutePath("/invoices/:id")).toBe("/invoices/{id}");
+        expect(normaliseRoutePath("/a/:b/c/:d")).toBe("/a/{b}/c/{d}");
+    });
+
+    it("normaliseRoutePath is idempotent on already-OAS paths", {
+        timeout: 5000,
+    }, () => {
+        expect(normaliseRoutePath("/invoices/{id}")).toBe("/invoices/{id}");
+    });
+
+    it("normaliseRoutePath does not rewrite non-identifier colons", {
+        timeout: 5000,
+    }, () => {
+        // Port-like segments use a digit immediately after the colon — must
+        // not be confused with a path parameter.
+        expect(normaliseRoutePath("/host:443/path")).toBe("/host:443/path");
+    });
+});
+
+describe("namespacing — operationIdFor", () => {
+    it("operationId is deterministic", { timeout: 5000 }, () => {
+        // From spec scenario: GET /invoices/:id → billing.get./invoices/{id}
+        expect(operationIdFor(billing, "GET", "/invoices/:id")).toBe(
+            "billing.get./invoices/{id}"
+        );
+    });
+
+    it("operationId lower-cases method", { timeout: 5000 }, () => {
+        expect(operationIdFor(billing, "POST", "/invoices")).toBe(
+            "billing.post./invoices"
+        );
+    });
+});
+
+describe("namespacing — assignOperationIds", () => {
+    it("assigns derived ids when route has none", { timeout: 5000 }, () => {
+        const out = assignOperationIds([
+            { plugin: billing, route: route("GET", "/invoices/:id") },
+        ]);
+        expect(out).toHaveLength(1);
+        expect(out[0]?.operationId).toBe("billing.get./invoices/{id}");
+        expect(out[0]?.tag).toBe("Billing");
+        expect(out[0]?.method).toBe("get");
+        expect(out[0]?.path).toBe("/invoices/{id}");
+        expect(out[0]?.pluginName).toBe("billing");
+    });
+
+    it("respects pre-set operationId", { timeout: 5000 }, () => {
+        const out = assignOperationIds([
+            {
+                plugin: billing,
+                route: route("GET", "/x", { operationId: "custom" }),
+            },
+        ]);
+        expect(out[0]?.operationId).toBe("custom");
+    });
+
+    it("collision raises OPENAPI_OPERATION_ID_COLLISION", {
+        timeout: 5000,
+    }, () => {
+        // Two plugins emit the same operationId via custom override.
+        let err: unknown;
+        try {
+            assignOperationIds([
+                {
+                    plugin: billing,
+                    route: route("GET", "/a", { operationId: "shared" }),
+                },
+                {
+                    plugin: users,
+                    route: route("GET", "/b", { operationId: "shared" }),
+                },
+            ]);
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.OPERATION_ID_COLLISION
+        );
+        const ctx = (err as OpenAPIError).context as
+            | { operationId?: string }
+            | undefined;
+        expect(ctx?.operationId).toBe("shared");
+    });
+
+    it("does not collide across distinct routes", { timeout: 5000 }, () => {
+        const out = assignOperationIds([
+            { plugin: billing, route: route("GET", "/invoices") },
+            { plugin: billing, route: route("POST", "/invoices") },
+            { plugin: users, route: route("GET", "/users/:id") },
+        ]);
+        expect(out).toHaveLength(3);
+        expect(new Set(out.map((r) => r.operationId)).size).toBe(3);
+    });
+});

packages/api-stack/api/api-openapi/src/namespacing/namespacing.ts

@@ -0,0 +1,135 @@
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import type { HttpMethod, RegisteredRoute } from "../types/openapi.js";
+
+/**
+ * Lightweight view of a plugin manifest used by the namespacing layer.
+ * Drawn from `@suaveplan/api-types#PluginManifest` — we accept only the
+ * fields needed to derive tags, operationIds, and component prefixes so
+ * the namespacing helpers stay decoupled from full-manifest evolution.
+ */
+export interface NamespacePluginInfo {
+    readonly name: string;
+    readonly displayName?: string;
+}
+
+/**
+ * Derive the OpenAPI tag for a plugin. Falls back to `name` when
+ * `displayName` is omitted. Tags are deduplicated by the emitter at
+ * the document level.
+ */
+export function tagFor(plugin: NamespacePluginInfo): string {
+    return plugin.displayName ?? plugin.name;
+}
+
+/**
+ * Derive the component-schema prefix for a plugin.
+ *
+ * `<pluginName>.<TypeName>` — e.g. `billing.Invoice`. Plugin names are
+ * accepted verbatim; callers MUST already validate them at manifest
+ * ingestion time (see `@suaveplan/api-manifest`).
+ */
+export function componentPrefix(plugin: NamespacePluginInfo): string {
+    return plugin.name;
+}
+
+/**
+ * Convert an Express-style route path (`/invoices/:id`) into the OpenAPI
+ * `{param}` form (`/invoices/{id}`). Idempotent on already-OAS paths.
+ */
+export function normaliseRoutePath(path: string): string {
+    return path.replace(/:([A-Za-z_][\w-]*)/g, "{$1}");
+}
+
+/**
+ * Build the deterministic operationId for a route.
+ *
+ * `<pluginName>.<method>.<oasPath>` — e.g. `billing.get./invoices/{id}`.
+ * Lower-cased method. Path normalised through {@link normaliseRoutePath}.
+ */
+export function operationIdFor(
+    plugin: NamespacePluginInfo,
+    method: HttpMethod | string,
+    path: string
+): string {
+    return `${plugin.name}.${method.toLowerCase()}.${normaliseRoutePath(path)}`;
+}
+
+/**
+ * Per-route entry used by {@link assignOperationIds}. Carries the owning
+ * plugin so the emitter can attach the right tag + prefix.
+ */
+export interface NamespacedRouteInput {
+    readonly plugin: NamespacePluginInfo;
+    readonly route: RegisteredRoute;
+}
+
+/**
+ * Output of {@link assignOperationIds} — every input route enriched
+ * with the canonical operationId, tag, and OAS-normalised path.
+ */
+export interface NamespacedRoute {
+    readonly pluginName: string;
+    readonly tag: string;
+    readonly operationId: string;
+    readonly method: string;
+    readonly path: string;
+    readonly route: RegisteredRoute;
+}
+
+/**
+ * Walk every route and attach the canonical operationId.
+ *
+ * Pre-existing `operationId` on a route is respected unless it collides
+ * with another route's derived id. When two routes resolve to the same
+ * operationId, {@link OpenAPIError} with {@link OPENAPI_CODES.OPERATION_ID_COLLISION}
+ * is raised — the host MUST refuse to install the colliding plugin
+ * BEFORE traffic reaches it.
+ */
+export function assignOperationIds(
+    inputs: readonly NamespacedRouteInput[]
+): NamespacedRoute[] {
+    const seen = new Map<string, NamespacedRoute>();
+    const result: NamespacedRoute[] = [];
+
+    for (const input of inputs) {
+        const { plugin, route } = input;
+        const derived = operationIdFor(plugin, route.method, route.path);
+        const operationId = route.operationId ?? derived;
+        const oasPath = normaliseRoutePath(route.path);
+        const tag = tagFor(plugin);
+        const entry: NamespacedRoute = {
+            pluginName: plugin.name,
+            tag,
+            operationId,
+            method: route.method.toLowerCase(),
+            path: oasPath,
+            route,
+        };
+
+        const prior = seen.get(operationId);
+        if (prior !== undefined) {
+            throw new OpenAPIError(
+                OPENAPI_CODES.OPERATION_ID_COLLISION,
+                `operationId "${operationId}" collides between plugins "${prior.pluginName}" and "${plugin.name}"`,
+                {
+                    context: {
+                        operationId,
+                        first: {
+                            plugin: prior.pluginName,
+                            method: prior.method,
+                            path: prior.path,
+                        },
+                        second: {
+                            plugin: plugin.name,
+                            method: entry.method,
+                            path: entry.path,
+                        },
+                    },
+                }
+            );
+        }
+        seen.set(operationId, entry);
+        result.push(entry);
+    }
+    return result;
+}

packages/api-stack/api/api-openapi/src/plugin-integration/index.ts

@@ -0,0 +1,6 @@
+export type {
+    DefinePluginRoutesOptions,
+    PluginRouteEntry,
+    RouteHandler,
+} from "./plugin-integration.js";
+export { definePluginRoutes } from "./plugin-integration.js";

packages/api-stack/api/api-openapi/src/plugin-integration/plugin-integration.md

@@ -0,0 +1,125 @@
+# plugin-integration
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`definePluginRoutes` is the single helper plugins call from their `onInit`
+to register routes. Every call atomically updates both the Hono
+`OpenAPIHono` app (via `app.openapi(route, handler)`) and the
+`OpenAPIRegistry` (via `registry.registerRoute(...)`). The two surfaces
+cannot drift — there is no path through the helper that touches only
+one of them.
+
+Eliminates a class of upstream bugs where a plugin would either
+register against Hono but forget the registry (operation served but
+not discoverable) or the inverse (discoverable but not served).
+
+## Features
+
+- Atomically registers each route against both Hono and the registry.
+- Records `pluginName` on every registry entry for later `registry.getRoutesByPlugin(name)` lookups.
+- Carries `operationId`, `summary`, `description`, `deprecated`, and `security` through into the registry record.
+- Returns the list of `RegisteredRoute` entries for caller-side post-processing.
+- Defensive-copies `tags` and `security` arrays so the route config remains immutable from the registry's perspective.
+
+## Usage: Basic
+
+```ts
+import { OpenAPIHono, z } from "@hono/zod-openapi";
+import { createOpenAPIRegistry } from "@suaveplan/api-openapi/registry";
+import { GET, successResponse } from "@suaveplan/api-openapi/route-factory";
+import { definePluginRoutes } from "@suaveplan/api-openapi/plugin-integration";
+
+const app = new OpenAPIHono();
+const registry = createOpenAPIRegistry({
+    info: { title: "X", version: "1.0.0" },
+});
+
+const ListUsers = GET("/users")
+    .tags("users")
+    .operationId("listUsers")
+    .response(successResponse(z.array(z.object({ id: z.string() }))))
+    .build();
+
+definePluginRoutes(
+    [
+        {
+            route: ListUsers,
+            handler: (c) => c.json({ success: true as const, data: [] }, 200),
+        },
+    ],
+    { app, registry, pluginName: "users" }
+);
+```
+
+## Usage: Advanced
+
+```ts
+import { definePluginRoutes } from "@suaveplan/api-openapi/plugin-integration";
+import { definePlugin } from "@suaveplan/api-plugin";
+
+interface MyServices {
+    app: OpenAPIHono;
+    registry: OpenAPIRegistry;
+}
+
+export const projectsPlugin = definePlugin<{
+    /* config shape */
+}>({
+    name: "projects",
+    version: "0.1.0",
+    onInit(ctx) {
+        const app = ctx.getService("app") as MyServices["app"];
+        const registry = ctx.getService("registry") as MyServices["registry"];
+        const created = definePluginRoutes(
+            [
+                /* { route, handler } entries built with RouteBuilder */
+            ],
+            { app, registry, pluginName: "projects" }
+        );
+        ctx.logger.info(`projects: registered ${created.length} routes`);
+    },
+});
+```
+
+## API Reference
+
+- `type RouteHandler = (c: Context) => Response | Promise<Response> | unknown`
+- `interface PluginRouteEntry { route: RouteConfig; handler: RouteHandler }`
+- `interface DefinePluginRoutesOptions { app: OpenAPIHono; registry: OpenAPIRegistry; pluginName: string }`
+- `function definePluginRoutes(entries, options): RegisteredRoute[]`
+
+## Implementation Notes
+
+The helper iterates the entries sequentially — there is no parallelism.
+Hono's `app.openapi` is synchronous and side-effecting, so concurrency
+would gain nothing. Sequential iteration also gives well-defined
+ordering in `registry.getRoutesByPlugin(name)`: the array reflects the
+order routes were declared in the plugin source, which is the order
+authors expect when consuming the registry for documentation or
+introspection.
+
+The `RegisteredRoute` record copies the route's `tags` and `security`
+arrays defensively. A plugin could otherwise mutate the array on its
+`RouteConfig` post-registration and silently alter the registry's
+introspection view.
+
+`route.method` is passed through to the registry as-is. Hono normalises
+methods to lowercase, so the registry receives lowercase, matching the
+expectations of `OpenAPIRegistry.buildDocument()`.
+
+The helper is intentionally a free function (not a method on the
+registry). Decoupling it from the registry class means plugins can
+substitute their own "register-both-surfaces" implementation in tests
+without touching the registry contract.
+
+The handler type is `(c: Context) => Response | Promise<Response> | unknown`
+— Hono's actual handler signature is broader (typed under generics
+that depend on the specific RouteConfig). Trying to surface that
+inference at the helper boundary would require every caller to thread
+the same generics, defeating the helper's purpose. We accept the loose
+signature and trust the call site of `app.openapi` to type-check the
+handler against the route's contract.

packages/api-stack/api/api-openapi/src/plugin-integration/plugin-integration.test.ts

@@ -0,0 +1,228 @@
+import { OpenAPIHono, z } from "@hono/zod-openapi";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import { createOpenAPIRegistry } from "../registry/registry.js";
+import { GET, POST, successResponse } from "../route-factory/route-factory.js";
+import { definePluginRoutes } from "./plugin-integration.js";
+
+describe("definePluginRoutes", () => {
+    it("registers in Hono and registry together", { timeout: 5000 }, () => {
+        const app = new OpenAPIHono();
+        const registry = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+
+        const list = GET("/users")
+            .tags("users")
+            .operationId("listUsers")
+            .response(successResponse(z.array(z.object({ id: z.string() }))))
+            .build();
+
+        const recorded = definePluginRoutes(
+            [
+                {
+                    route: list,
+                    handler: (c) =>
+                        c.json({ success: true as const, data: [] }, 200),
+                },
+            ],
+            { app, registry, pluginName: "users" }
+        );
+
+        expect(recorded).toHaveLength(1);
+        expect(
+            app.routes.some((r) => r.path === "/users" && r.method === "GET")
+        ).toBe(true);
+        const fromRegistry = registry.getRoutesByPlugin("users");
+        expect(fromRegistry).toHaveLength(1);
+        expect(fromRegistry[0]?.operationId).toBe("listUsers");
+    });
+
+    it("carries summary/description/deprecated/security into the registry", {
+        timeout: 5000,
+    }, () => {
+        const app = new OpenAPIHono();
+        const registry = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+
+        const r = POST("/things")
+            .tags("things")
+            .summary("Create thing")
+            .description("Creates a thing")
+            .deprecated()
+            .security([{ Bearer: ["admin"] }])
+            .body(z.object({ name: z.string() }))
+            .response(successResponse(z.object({ id: z.string() })))
+            .build();
+
+        definePluginRoutes(
+            [
+                {
+                    route: r,
+                    handler: (c) =>
+                        c.json(
+                            {
+                                success: true as const,
+                                data: { id: "1" },
+                            },
+                            200
+                        ),
+                },
+            ],
+            { app, registry, pluginName: "things" }
+        );
+
+        const [rec] = registry.getRoutesByPlugin("things");
+        expect(rec?.summary).toBe("Create thing");
+        expect(rec?.description).toBe("Creates a thing");
+        expect(rec?.deprecated).toBe(true);
+        expect(rec?.security).toEqual([{ Bearer: ["admin"] }]);
+    });
+
+    it("defensive-copies tags array", { timeout: 5000 }, () => {
+        const app = new OpenAPIHono();
+        const registry = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        const r = GET("/x").tags("a", "b").response(z.object({})).build();
+        const [recorded] = definePluginRoutes(
+            [{ route: r, handler: (c) => c.json({}) }],
+            { app, registry, pluginName: "p" }
+        );
+        // Mutating the recorded array must not change the route config.
+        (recorded?.tags as string[]).push("mutated");
+        expect(r.tags).toEqual(["a", "b"]);
+    });
+
+    it("returns the list of registered records", { timeout: 5000 }, () => {
+        const app = new OpenAPIHono();
+        const registry = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        const r1 = GET("/a").response(z.object({})).build();
+        const r2 = GET("/b").response(z.object({})).build();
+        const out = definePluginRoutes(
+            [
+                { route: r1, handler: (c) => c.json({}) },
+                { route: r2, handler: (c) => c.json({}) },
+            ],
+            { app, registry, pluginName: "multi" }
+        );
+        expect(out.map((x) => x.path).sort()).toEqual(["/a", "/b"]);
+    });
+});
+
+describe("definePluginRoutes input validation", () => {
+    const makeOk = () => {
+        const app = new OpenAPIHono();
+        const registry = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        const route = GET("/x").response(z.object({})).build();
+        return { app, registry, route };
+    };
+
+    const expectInvalidInput = (fn: () => unknown): void => {
+        let err: unknown;
+        try {
+            fn();
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.INVALID_INPUT);
+    };
+
+    it("throws INVALID_INPUT when options is null", { timeout: 5000 }, () => {
+        expectInvalidInput(() => definePluginRoutes([], null as never));
+    });
+
+    it("throws INVALID_INPUT when options.app is missing", {
+        timeout: 5000,
+    }, () => {
+        const { registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([], { registry, pluginName: "p" } as never)
+        );
+    });
+
+    it("throws INVALID_INPUT when options.registry is missing", {
+        timeout: 5000,
+    }, () => {
+        const { app } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([], { app, pluginName: "p" } as never)
+        );
+    });
+
+    it("throws INVALID_INPUT when pluginName is empty string", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([], { app, registry, pluginName: "" })
+        );
+    });
+
+    it("throws INVALID_INPUT when pluginName is not a string", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([], { app, registry, pluginName: 7 as never })
+        );
+    });
+
+    it("throws INVALID_INPUT when entries is not an array", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes("not-an-array" as never, {
+                app,
+                registry,
+                pluginName: "p",
+            })
+        );
+    });
+
+    it("throws INVALID_INPUT when an entry is null", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([null as never], {
+                app,
+                registry,
+                pluginName: "p",
+            })
+        );
+    });
+
+    it("throws INVALID_INPUT when entry.route is missing", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([{ handler: () => undefined } as never], {
+                app,
+                registry,
+                pluginName: "p",
+            })
+        );
+    });
+
+    it("throws INVALID_INPUT when entry.handler is not a function", {
+        timeout: 5000,
+    }, () => {
+        const { app, registry, route } = makeOk();
+        expectInvalidInput(() =>
+            definePluginRoutes([{ route, handler: "not-a-fn" as never }], {
+                app,
+                registry,
+                pluginName: "p",
+            })
+        );
+    });
+});

packages/api-stack/api/api-openapi/src/plugin-integration/plugin-integration.ts

@@ -0,0 +1,132 @@
+import type { OpenAPIHono, RouteConfig } from "@hono/zod-openapi";
+import type { Context } from "hono";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import type { OpenAPIRegistry } from "../registry/registry.js";
+import type { RegisteredRoute } from "../types/openapi.js";
+
+/**
+ * Handler signature accepted by {@link definePluginRoutes}. Loose typing
+ * (Hono-typed `Context`) keeps the helper usable by every plugin without
+ * forcing each one to surface its `c.req.valid()` inference up to the
+ * caller — that inference happens at the call site of `app.openapi`.
+ */
+export type RouteHandler = (
+    c: Context
+) => Response | Promise<Response> | unknown;
+
+/**
+ * Entry passed to {@link definePluginRoutes} — a built route plus the
+ * handler that backs it.
+ */
+export interface PluginRouteEntry {
+    readonly route: RouteConfig;
+    readonly handler: RouteHandler;
+}
+
+/**
+ * Options accepted by {@link definePluginRoutes}.
+ */
+export interface DefinePluginRoutesOptions {
+    readonly app: OpenAPIHono;
+    readonly registry: OpenAPIRegistry;
+    readonly pluginName: string;
+}
+
+/**
+ * Register a batch of plugin routes against BOTH the Hono app and the
+ * OpenAPI registry. The two surfaces cannot drift — every successful
+ * registration touches both. Returns the list of {@link RegisteredRoute}
+ * entries added so the caller can inspect or further annotate them.
+ */
+export function definePluginRoutes(
+    entries: PluginRouteEntry[],
+    options: DefinePluginRoutesOptions
+): RegisteredRoute[] {
+    if (!options || typeof options !== "object") {
+        throw new OpenAPIError(
+            OPENAPI_CODES.INVALID_INPUT,
+            "definePluginRoutes options is required"
+        );
+    }
+    const { app, registry, pluginName } = options;
+    if (!app) {
+        throw new OpenAPIError(
+            OPENAPI_CODES.INVALID_INPUT,
+            "definePluginRoutes: options.app is required"
+        );
+    }
+    if (!registry) {
+        throw new OpenAPIError(
+            OPENAPI_CODES.INVALID_INPUT,
+            "definePluginRoutes: options.registry is required"
+        );
+    }
+    if (typeof pluginName !== "string" || pluginName.length === 0) {
+        throw new OpenAPIError(
+            OPENAPI_CODES.INVALID_INPUT,
+            "definePluginRoutes: options.pluginName must be a non-empty string"
+        );
+    }
+    if (!Array.isArray(entries)) {
+        throw new OpenAPIError(
+            OPENAPI_CODES.INVALID_INPUT,
+            "definePluginRoutes: entries must be an array"
+        );
+    }
+    const registered: RegisteredRoute[] = [];
+
+    for (const entry of entries) {
+        if (!entry || typeof entry !== "object") {
+            throw new OpenAPIError(
+                OPENAPI_CODES.INVALID_INPUT,
+                "definePluginRoutes: every entry must be { route, handler }"
+            );
+        }
+        const { route, handler } = entry;
+        if (!route || typeof route !== "object") {
+            throw new OpenAPIError(
+                OPENAPI_CODES.INVALID_INPUT,
+                "definePluginRoutes: entry.route is required"
+            );
+        }
+        if (typeof handler !== "function") {
+            throw new OpenAPIError(
+                OPENAPI_CODES.INVALID_INPUT,
+                "definePluginRoutes: entry.handler must be a function"
+            );
+        }
+        // Cast: handler signature is intentionally generic. Hono's
+        // `app.openapi` infers via the RouteConfig at the call site —
+        // we accept the loose signature here.
+        app.openapi(
+            route as Parameters<OpenAPIHono["openapi"]>[0],
+            handler as Parameters<OpenAPIHono["openapi"]>[1]
+        );
+
+        const record: RegisteredRoute = {
+            method: route.method,
+            path: route.path,
+            tags: route.tags ? [...route.tags] : [],
+            pluginName,
+        };
+        if (route.operationId !== undefined) {
+            record.operationId = route.operationId;
+        }
+        if (route.summary !== undefined) {
+            record.summary = route.summary;
+        }
+        if (route.description !== undefined) {
+            record.description = route.description;
+        }
+        if (route.deprecated === true) {
+            record.deprecated = true;
+        }
+        if (route.security !== undefined) {
+            record.security = route.security as Array<Record<string, string[]>>;
+        }
+        registry.registerRoute(record);
+        registered.push(record);
+    }
+
+    return registered;
+}

packages/api-stack/api/api-openapi/src/registry/index.ts

@@ -0,0 +1,8 @@
+export type { OpenAPIRegistryOptions } from "./registry.js";
+export {
+    ApiKeyScheme,
+    BearerAuthScheme,
+    createOpenAPIRegistry,
+    DEFAULT_SPEC_PATH,
+    OpenAPIRegistry,
+} from "./registry.js";

packages/api-stack/api/api-openapi/src/registry/registry.md

@@ -0,0 +1,134 @@
+# registry
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Centralised OpenAPI 3.1 registry that holds `info`, `servers`,
+`securitySchemes`, `tags`, and `routes`. Acts as the single source of
+truth across the package: plugins register against it, the merger
+consumes its `buildDocument()` output, and the Hono integration wires
+it directly to `app.doc(...)` via `applyTo(app)`. Eliminates the
+upstream's silent drift between the introspection registry and the
+served `/openapi.json`.
+
+The registry is instance-based — never a singleton — so multi-tenant
+servers, parallel tests, and ephemeral spec previews all run without
+shared state.
+
+## Features
+
+- Constructor takes `info`, optional `servers`, optional `security`
+  (security-scheme records), and optional `globalSecurity` (default
+  security requirements for every operation).
+- `registerSecurityScheme(scheme)` / `registerTag(name, description?)`
+  / `registerRoute(route)`.
+- `getRoutes()`, `getRoutesByPlugin(name)`, `getRoutesByTag(tag)`,
+  `updateInfo(partial)`, `addServer(server)`, `clearRoutes()`.
+- `buildDocument()` returns the full `OpenAPIDocument` (3.1.0, info,
+  servers, paths derived from registered routes, components.securitySchemes,
+  tags, security).
+- `applyTo(app, specPath = "/openapi.json")` registers a GET handler on
+  the Hono app that returns `buildDocument()` as JSON.
+- `BearerAuthScheme` + `ApiKeyScheme` presets.
+- Factory `createOpenAPIRegistry(options)`.
+
+## Usage: Basic
+
+```ts
+import { createOpenAPIRegistry } from "@suaveplan/api-openapi/registry";
+
+const registry = createOpenAPIRegistry({
+    info: { title: "Users API", version: "1.0.0" },
+});
+
+registry.registerRoute({
+    method: "get",
+    path: "/users",
+    tags: ["users"],
+    operationId: "listUsers",
+    summary: "List all users",
+});
+
+const doc = registry.buildDocument();
+console.log(doc.paths["/users"]?.get?.operationId); // "listUsers"
+```
+
+## Usage: Advanced
+
+```ts
+import { OpenAPIHono } from "@hono/zod-openapi";
+import {
+    BearerAuthScheme,
+    createOpenAPIRegistry,
+} from "@suaveplan/api-openapi/registry";
+
+const app = new OpenAPIHono();
+const registry = createOpenAPIRegistry({
+    info: { title: "Multi-plugin API", version: "0.1.0" },
+    servers: [{ url: "https://api.example.com" }],
+    security: [BearerAuthScheme],
+    globalSecurity: [{ Bearer: [] }],
+});
+
+registry.registerRoute({
+    method: "post",
+    path: "/projects",
+    tags: ["projects"],
+    pluginName: "projects",
+    operationId: "createProject",
+    deprecated: false,
+    security: [{ Bearer: [] }],
+});
+
+// Single line wires the registry to Hono. The served `/openapi.json` is
+// always `buildDocument()` — no drift possible.
+registry.applyTo(app, "/openapi.json");
+```
+
+## API Reference
+
+- `class OpenAPIRegistry`
+  - `constructor(options: OpenAPIRegistryOptions)`
+  - `registerSecurityScheme(scheme: SecurityScheme): void`
+  - `registerTag(name: string, description?: string): void`
+  - `registerRoute(route: RegisteredRoute): void`
+  - `getRoutes(): RegisteredRoute[]` — defensive copy
+  - `getRoutesByPlugin(pluginName: string): RegisteredRoute[]`
+  - `getRoutesByTag(tag: string): RegisteredRoute[]`
+  - `updateInfo(info: Partial<OpenAPIInfo>): void`
+  - `addServer(server: OpenAPIServer): void`
+  - `clearRoutes(): void`
+  - `buildDocument(): OpenAPIDocument`
+  - `applyTo(app: OpenAPIHono, specPath?: string): void`
+- `function createOpenAPIRegistry(options): OpenAPIRegistry`
+- `const BearerAuthScheme: SecurityScheme`
+- `const ApiKeyScheme: SecurityScheme`
+- `const DEFAULT_SPEC_PATH = "/openapi.json"`
+
+## Implementation Notes
+
+`buildDocument()` synthesises `paths` from the registered routes — each
+route becomes an `Operation` keyed by method under its `path`. Multiple
+methods on the same path collapse into one `PathItem` (registry collisions
+on the same `(method, path)` overwrite — last registration wins, mirroring
+Hono's `app.openapi` semantics).
+
+The synthesised `Operation` body is intentionally lean — `operationId`,
+`summary`, `description`, `tags`, `deprecated`, `security`, and an empty
+`responses: {}`. Request/response Zod-derived schemas are added by the
+plugin integration when the registry is paired with `app.openapi(route, …)`
+and merged into the registry doc via `mergeOpenAPIDocuments`. Keeping
+the registry's emitted operations schema-free means the registry stays
+zero-cost to build (no Zod traversal) and reusable for non-Hono targets.
+
+`applyTo` registers a plain `app.get(specPath, …)` handler rather than
+`app.doc(specPath, …)` so the served body is exactly `buildDocument()`.
+Hono's `app.doc` invokes its own document builder, which would defeat
+the purpose of using the registry as the source of truth.
+
+All getters return defensive copies of arrays — internal mutation of
+`routes` / `servers` from caller code is impossible without going
+through the explicit `register*` / `clearRoutes` / `addServer` methods.

packages/api-stack/api/api-openapi/src/registry/registry.test.ts

@@ -0,0 +1,252 @@
+import { OpenAPIHono } from "@hono/zod-openapi";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    ApiKeyScheme,
+    BearerAuthScheme,
+    createOpenAPIRegistry,
+    DEFAULT_SPEC_PATH,
+    OpenAPIRegistry,
+} from "./registry.js";
+
+describe("OpenAPIRegistry", () => {
+    it("constructs with info only", { timeout: 5000 }, () => {
+        const r = new OpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        const doc = r.buildDocument();
+        expect(doc.openapi).toBe("3.1.0");
+        expect(doc.info.title).toBe("T");
+        expect(doc.paths).toEqual({});
+        expect(doc.servers).toBeUndefined();
+    });
+
+    it("registers and lists servers", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+            servers: [{ url: "https://a.example" }],
+        });
+        r.addServer({ url: "https://b.example" });
+        const doc = r.buildDocument();
+        expect(doc.servers).toEqual([
+            { url: "https://a.example" },
+            { url: "https://b.example" },
+        ]);
+    });
+
+    it("registered routes appear in paths", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({
+            method: "get",
+            path: "/items",
+            tags: ["items"],
+            operationId: "listItems",
+            summary: "List",
+            description: "List items",
+        });
+        const doc = r.buildDocument();
+        expect(doc.paths["/items"]?.get?.operationId).toBe("listItems");
+        expect(doc.paths["/items"]?.get?.summary).toBe("List");
+        expect(doc.paths["/items"]?.get?.description).toBe("List items");
+        expect(doc.paths["/items"]?.get?.tags).toEqual(["items"]);
+    });
+
+    it("merges multiple methods on the same path", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({ method: "get", path: "/x", tags: [] });
+        r.registerRoute({ method: "post", path: "/x", tags: [] });
+        const item = r.buildDocument().paths["/x"];
+        expect(item?.get).toBeDefined();
+        expect(item?.post).toBeDefined();
+    });
+
+    it("propagates deprecated + security on operations", {
+        timeout: 5000,
+    }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({
+            method: "delete",
+            path: "/x",
+            tags: [],
+            deprecated: true,
+            security: [{ Bearer: ["admin"] }],
+        });
+        const op = r.buildDocument().paths["/x"]?.delete;
+        expect(op?.deprecated).toBe(true);
+        expect(op?.security).toEqual([{ Bearer: ["admin"] }]);
+    });
+
+    it("auto-registers tags from routes", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({
+            method: "get",
+            path: "/a",
+            tags: ["alpha", "beta"],
+        });
+        const doc = r.buildDocument();
+        expect(doc.tags?.map((t) => t.name).sort()).toEqual(["alpha", "beta"]);
+    });
+
+    it("preserves explicit tag descriptions", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerTag("explicit", "an explicit tag");
+        r.registerTag("nodesc");
+        const tags = r.buildDocument().tags ?? [];
+        expect(tags.find((t) => t.name === "explicit")?.description).toBe(
+            "an explicit tag"
+        );
+        expect(
+            tags.find((t) => t.name === "nodesc")?.description
+        ).toBeUndefined();
+    });
+
+    it("emits security schemes in components", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+            security: [BearerAuthScheme, ApiKeyScheme],
+            globalSecurity: [{ Bearer: [] }],
+        });
+        const doc = r.buildDocument();
+        expect(
+            (doc.components?.securitySchemes as Record<string, unknown>)?.[
+                "Bearer"
+            ]
+        ).toMatchObject({
+            type: "http",
+            scheme: "bearer",
+            bearerFormat: "JWT",
+        });
+        expect(
+            (doc.components?.securitySchemes as Record<string, unknown>)?.[
+                "ApiKey"
+            ]
+        ).toMatchObject({ type: "apiKey", in: "header" });
+        expect(doc.security).toEqual([{ Bearer: [] }]);
+    });
+
+    it("registerSecurityScheme adds after construction", {
+        timeout: 5000,
+    }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerSecurityScheme({
+            name: "Custom",
+            type: "apiKey",
+            in: "query",
+        });
+        const schemes = r.buildDocument().components?.securitySchemes as Record<
+            string,
+            unknown
+        >;
+        expect(schemes["Custom"]).toMatchObject({
+            type: "apiKey",
+            in: "query",
+        });
+    });
+
+    it("getRoutesByPlugin + getRoutesByTag filter correctly", {
+        timeout: 5000,
+    }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({
+            method: "get",
+            path: "/u",
+            tags: ["users"],
+            pluginName: "users",
+        });
+        r.registerRoute({
+            method: "get",
+            path: "/p",
+            tags: ["projects"],
+            pluginName: "projects",
+        });
+        expect(r.getRoutesByPlugin("users").map((x) => x.path)).toEqual(["/u"]);
+        expect(r.getRoutesByTag("projects").map((x) => x.path)).toEqual(["/p"]);
+        expect(r.getRoutes()).toHaveLength(2);
+    });
+
+    it("updateInfo merges patches", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "Old", version: "0.0.1" },
+        });
+        r.updateInfo({ title: "New", description: "d" });
+        const info = r.buildDocument().info;
+        expect(info.title).toBe("New");
+        expect(info.version).toBe("0.0.1");
+        expect(info.description).toBe("d");
+    });
+
+    it("clearRoutes empties routes", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({ method: "get", path: "/x", tags: [] });
+        expect(r.getRoutes()).toHaveLength(1);
+        r.clearRoutes();
+        expect(r.getRoutes()).toHaveLength(0);
+    });
+
+    it("getRoutes returns a defensive copy", { timeout: 5000 }, () => {
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.registerRoute({ method: "get", path: "/x", tags: [] });
+        const list = r.getRoutes();
+        list.pop();
+        expect(r.getRoutes()).toHaveLength(1);
+    });
+
+    it("applyTo serves buildDocument output", { timeout: 5000 }, async () => {
+        const app = new OpenAPIHono();
+        const r = createOpenAPIRegistry({
+            info: { title: "Live", version: "1.2.3" },
+        });
+        r.registerRoute({
+            method: "get",
+            path: "/items",
+            tags: ["items"],
+            operationId: "listItems",
+        });
+        r.applyTo(app);
+        const res = await app.request(DEFAULT_SPEC_PATH);
+        expect(res.status).toBe(200);
+        const body = (await res.json()) as { paths: Record<string, unknown> };
+        expect(body).toEqual(r.buildDocument());
+        expect(body.paths["/items"]).toBeDefined();
+    });
+
+    it("applyTo accepts a custom spec path", { timeout: 5000 }, async () => {
+        const app = new OpenAPIHono();
+        const r = createOpenAPIRegistry({
+            info: { title: "T", version: "1.0.0" },
+        });
+        r.applyTo(app, "/spec.json");
+        const res = await app.request("/spec.json");
+        expect(res.status).toBe(200);
+    });
+});
+
+describe("BearerAuthScheme + ApiKeyScheme presets", () => {
+    it("Bearer is http+bearer with JWT format", { timeout: 5000 }, () => {
+        expect(BearerAuthScheme.type).toBe("http");
+        expect(BearerAuthScheme.scheme).toBe("bearer");
+        expect(BearerAuthScheme.bearerFormat).toBe("JWT");
+    });
+
+    it("ApiKey is header-based apiKey", { timeout: 5000 }, () => {
+        expect(ApiKeyScheme.type).toBe("apiKey");
+        expect(ApiKeyScheme.in).toBe("header");
+    });
+});

packages/api-stack/api/api-openapi/src/registry/registry.ts

@@ -0,0 +1,222 @@
+import type { OpenAPIHono } from "@hono/zod-openapi";
+import type {
+    OpenAPIDocument,
+    OpenAPIInfo,
+    OpenAPIServer,
+    Operation,
+    PathItem,
+    RegisteredRoute,
+    SecurityScheme,
+} from "../types/openapi.js";
+
+/**
+ * Options accepted by {@link OpenAPIRegistry}.
+ */
+export interface OpenAPIRegistryOptions {
+    readonly info: OpenAPIInfo;
+    readonly servers?: OpenAPIServer[];
+    readonly security?: SecurityScheme[];
+    readonly globalSecurity?: Array<Record<string, string[]>>;
+}
+
+/**
+ * Default URL path served by {@link OpenAPIRegistry.applyTo} when
+ * connecting the registry to a Hono `OpenAPIHono` app.
+ */
+export const DEFAULT_SPEC_PATH = "/openapi.json";
+
+/**
+ * OpenAPI 3.1 registry — single source of truth across the package.
+ *
+ * Tracks document `info`, `servers`, `securitySchemes`, `tags`, and
+ * `routes` registered by plugins. `buildDocument()` emits the full
+ * `OpenAPIDocument`. `applyTo(app)` wires a Hono handler so the served
+ * spec exactly matches `buildDocument()` output — eliminating drift
+ * between the registry's introspection state and the served spec.
+ */
+export class OpenAPIRegistry {
+    private info: OpenAPIInfo;
+    private readonly servers: OpenAPIServer[];
+    private readonly securitySchemes: Map<string, SecurityScheme> = new Map();
+    private readonly routes: RegisteredRoute[] = [];
+    private readonly tags: Map<string, { description?: string }> = new Map();
+    private readonly globalSecurity: Array<Record<string, string[]>>;
+
+    public constructor(options: OpenAPIRegistryOptions) {
+        this.info = options.info;
+        this.servers = options.servers ? [...options.servers] : [];
+        this.globalSecurity = options.globalSecurity
+            ? options.globalSecurity.map((entry) => ({ ...entry }))
+            : [];
+
+        if (options.security) {
+            for (const scheme of options.security) {
+                this.registerSecurityScheme(scheme);
+            }
+        }
+    }
+
+    public registerSecurityScheme(scheme: SecurityScheme): void {
+        this.securitySchemes.set(scheme.name, scheme);
+    }
+
+    public registerTag(name: string, description?: string): void {
+        this.tags.set(name, description !== undefined ? { description } : {});
+    }
+
+    public registerRoute(route: RegisteredRoute): void {
+        this.routes.push(route);
+        for (const tag of route.tags) {
+            if (!this.tags.has(tag)) {
+                this.tags.set(tag, {});
+            }
+        }
+    }
+
+    public getRoutes(): RegisteredRoute[] {
+        return [...this.routes];
+    }
+
+    public getRoutesByPlugin(pluginName: string): RegisteredRoute[] {
+        return this.routes.filter((r) => r.pluginName === pluginName);
+    }
+
+    public getRoutesByTag(tag: string): RegisteredRoute[] {
+        return this.routes.filter((r) => r.tags.includes(tag));
+    }
+
+    public updateInfo(info: Partial<OpenAPIInfo>): void {
+        this.info = { ...this.info, ...info };
+    }
+
+    public addServer(server: OpenAPIServer): void {
+        this.servers.push(server);
+    }
+
+    public clearRoutes(): void {
+        this.routes.length = 0;
+    }
+
+    /**
+     * Build the full OpenAPI 3.1 document — info, servers, paths
+     * (derived from registered routes), components (schemas remain
+     * empty here; security schemes carry through), tags, security.
+     */
+    public buildDocument(): OpenAPIDocument {
+        const paths: Record<string, PathItem> = {};
+
+        for (const route of this.routes) {
+            const method = route.method.toLowerCase() as keyof PathItem;
+            const op: Operation = { responses: {} };
+            if (route.operationId !== undefined) {
+                op.operationId = route.operationId;
+            }
+            if (route.summary !== undefined) op.summary = route.summary;
+            if (route.description !== undefined) {
+                op.description = route.description;
+            }
+            if (route.tags.length > 0) op.tags = [...route.tags];
+            if (route.deprecated === true) op.deprecated = true;
+            if (route.security !== undefined) {
+                op.security = route.security.map((entry) => ({ ...entry }));
+            }
+
+            const existing = paths[route.path] ?? {};
+            existing[method] = op;
+            paths[route.path] = existing;
+        }
+
+        const document: OpenAPIDocument = {
+            openapi: "3.1.0",
+            info: this.info,
+            paths,
+        };
+
+        if (this.servers.length > 0) {
+            document.servers = [...this.servers];
+        }
+
+        const tagEntries = Array.from(this.tags.entries()).map(
+            ([name, config]) =>
+                config.description !== undefined
+                    ? { name, description: config.description }
+                    : { name }
+        );
+        if (tagEntries.length > 0) {
+            document.tags = tagEntries;
+        }
+
+        const securitySchemes = this.serializeSecuritySchemes();
+        if (Object.keys(securitySchemes).length > 0) {
+            document.components = { securitySchemes };
+        }
+
+        if (this.globalSecurity.length > 0) {
+            document.security = this.globalSecurity.map((entry) => ({
+                ...entry,
+            }));
+        }
+
+        return document;
+    }
+
+    /**
+     * Wire `app.doc(specPath, …)` so a GET against `specPath` returns
+     * `buildDocument()` output. The registry remains the single source
+     * of truth — Hono only serves what the registry computes.
+     */
+    public applyTo(
+        app: OpenAPIHono,
+        specPath: string = DEFAULT_SPEC_PATH
+    ): void {
+        const build = (): OpenAPIDocument => this.buildDocument();
+        app.get(specPath, (c) => c.json(build()));
+    }
+
+    private serializeSecuritySchemes(): Record<string, unknown> {
+        const schemes: Record<string, unknown> = {};
+        for (const [name, scheme] of this.securitySchemes) {
+            const out: Record<string, unknown> = { type: scheme.type };
+            if (scheme.scheme !== undefined) out["scheme"] = scheme.scheme;
+            if (scheme.bearerFormat !== undefined) {
+                out["bearerFormat"] = scheme.bearerFormat;
+            }
+            if (scheme.in !== undefined) out["in"] = scheme.in;
+            if (scheme.description !== undefined) {
+                out["description"] = scheme.description;
+            }
+            schemes[name] = out;
+        }
+        return schemes;
+    }
+}
+
+/**
+ * Factory for {@link OpenAPIRegistry}.
+ */
+export function createOpenAPIRegistry(
+    options: OpenAPIRegistryOptions
+): OpenAPIRegistry {
+    return new OpenAPIRegistry(options);
+}
+
+/**
+ * Default Bearer (JWT) security scheme.
+ */
+export const BearerAuthScheme: SecurityScheme = {
+    name: "Bearer",
+    type: "http",
+    scheme: "bearer",
+    bearerFormat: "JWT",
+    description: "JWT Bearer token authentication",
+};
+
+/**
+ * Default header-based API key security scheme.
+ */
+export const ApiKeyScheme: SecurityScheme = {
+    name: "ApiKey",
+    type: "apiKey",
+    in: "header",
+    description: "API Key authentication",
+};

packages/api-stack/api/api-openapi/src/route-factory/error-response-schema.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { ErrorResponseSchema } from "./route-factory.js";
+
+describe("ErrorResponseSchema", () => {
+    it("accepts SuaveplanError.toJSON() output", { timeout: 5000 }, () => {
+        const payload = {
+            success: false,
+            error: {
+                code: "X.Y",
+                message: "boom",
+                timestamp: new Date().toISOString(),
+            },
+        };
+        expect(ErrorResponseSchema.safeParse(payload).success).toBe(true);
+    });
+
+    it("rejects success:true payload", { timeout: 5000 }, () => {
+        const payload = {
+            success: true,
+            error: {
+                code: "X.Y",
+                message: "boom",
+                timestamp: new Date().toISOString(),
+            },
+        };
+        expect(ErrorResponseSchema.safeParse(payload).success).toBe(false);
+    });
+});

packages/api-stack/api/api-openapi/src/route-factory/index.ts

@@ -0,0 +1,20 @@
+export type {
+    ErrorResponse,
+    RouteMethod,
+    RouteOptions,
+    TypedRouteConfig,
+} from "./route-factory.js";
+export {
+    DELETE,
+    ErrorResponseSchema,
+    errorResponse,
+    GET,
+    PATCH,
+    POST,
+    PUT,
+    paginatedResponse,
+    RouteBuilder,
+    route,
+    StandardResponses,
+    successResponse,
+} from "./route-factory.js";

packages/api-stack/api/api-openapi/src/route-factory/route-factory.md

@@ -0,0 +1,123 @@
+# route-factory
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Typed route construction utilities for `@hono/zod-openapi`. The
+`RouteBuilder` is a fluent generic that threads `TParams`, `TQuery`,
+`TBody`, and `TResponse` from `.params/.query/.body/.response` calls
+through to the final `.build()` output. The resulting `TypedRouteConfig`
+is assignable to `RouteConfig`, so `app.openapi(route, handler)` infers
+`c.req.valid("params" | "query" | "json")` to the exact Zod type
+without `unknown` widening.
+
+Also exports the wire-shape `ErrorResponseSchema`, the wider
+`StandardResponses` (covering every status code a `SuaveplanError` can
+emit — 400/401/403/404/409/422/429/500/503/504), and the
+`successResponse` / `paginatedResponse` / `errorResponse` envelope
+helpers.
+
+## Features
+
+- `RouteBuilder<TParams, TQuery, TBody, TResponse>` fluent generic.
+- `route(method, path)` factory + `GET`/`POST`/`PUT`/`PATCH`/`DELETE` shorthands.
+- `StandardResponses` widened to cover the full SuaveplanError status range.
+- `ErrorResponseSchema` carrying the `cause` field from `SuaveplanError.toJSON()`.
+- `successResponse(schema)`, `paginatedResponse(itemSchema)`, `errorResponse(description)` helpers.
+
+## Usage: Basic
+
+```ts
+import z from "zod";
+import { GET, successResponse } from "@suaveplan/api-openapi/route-factory";
+
+const ListUsers = GET("/users")
+    .tags("users")
+    .operationId("listUsers")
+    .response(successResponse(z.array(z.object({ id: z.string() }))))
+    .build();
+```
+
+## Usage: Advanced
+
+```ts
+import { OpenAPIHono } from "@hono/zod-openapi";
+import z from "zod";
+import {
+    POST,
+    paginatedResponse,
+    successResponse,
+} from "@suaveplan/api-openapi/route-factory";
+
+const UserParam = z.object({ id: z.string().uuid() });
+const UserCreate = z.object({ email: z.string().email() });
+const User = z.object({ id: z.string(), email: z.string() });
+
+const createUser = POST("/users/:id")
+    .tags("users")
+    .operationId("createUser")
+    .deprecated()
+    .security([{ Bearer: [] }])
+    .params(UserParam)
+    .body(UserCreate)
+    .response(successResponse(User))
+    .build();
+
+const listUsers = POST("/users/list")
+    .tags("users")
+    .response(paginatedResponse(User))
+    .build();
+
+const app = new OpenAPIHono();
+app.openapi(createUser, async (c) => {
+    const params = c.req.valid("param"); // typed as z.infer<typeof UserParam>
+    const body = c.req.valid("json"); // typed as z.infer<typeof UserCreate>
+    return c.json({ success: true, data: { id: params.id, email: body.email } });
+});
+```
+
+## API Reference
+
+- `type RouteMethod = "get"|"post"|"put"|"patch"|"delete"`
+- `interface RouteOptions<TParams, TQuery, TBody, TResponse>`
+- `const ErrorResponseSchema` + `type ErrorResponse`
+- `function successResponse<T>(dataSchema: T)`
+- `function errorResponse(description: string)`
+- `function paginatedResponse<T>(itemSchema: T)`
+- `const StandardResponses` — 400/401/403/404/409/422/429/500/503/504 each pointing at `ErrorResponseSchema`
+- `type TypedRouteConfig<TParams, TQuery, TBody, TResponse>`
+- `class RouteBuilder<TParams, TQuery, TBody, TResponse>`
+- `function route(method, path): RouteBuilder`
+- `const GET/POST/PUT/PATCH/DELETE`
+
+## Implementation Notes
+
+`TypedRouteConfig` uses `Omit<RouteConfig, "request"> & { request: … }`
+so the `request` property is non-optional. Hono's `InputType*`
+conditional types only match when `request` is present, so making it
+optional silently downgrades inference to `unknown`.
+
+The builder records state in a private object rather than directly on
+`this` so the four `.params/.query/.body/.response` overloads can re-cast
+the receiver to a new generic instantiation without TypeScript losing
+track of the actual stored values.
+
+`StandardResponses` is widened to cover every status `SuaveplanError`
+emits. Upstream omitted 422 (validation), 429 (rate limit), 503
+(service unavailable), and 504 (gateway timeout), forcing every plugin
+that wanted to document those responses to redefine them locally — a
+common source of doc drift. The widened set is now the single source.
+
+`ErrorResponseSchema` adds the `cause` field on top of upstream's
+shape. SuaveplanError supports a cause chain, and serialising it gives
+clients enough context to diagnose without requesting logs. `cause` is
+typed `z.unknown()` because the chain may be heterogeneous —
+SuaveplanError descendants, native `Error`s, or serialised payloads.
+
+`responses` always merges `200: Success` first and then spreads
+`StandardResponses` — so consumers can override `200` by passing
+`.response(…)` but cannot accidentally drop one of the standard error
+slots.

packages/api-stack/api/api-openapi/src/route-factory/route-factory.spec-conformance.test.ts

@@ -0,0 +1,52 @@
+import type { RouteConfig } from "@hono/zod-openapi";
+import { OpenAPIHono, z } from "@hono/zod-openapi";
+import { describe, expect, expectTypeOf, it } from "@suaveplan/testing/runner";
+import { POST, successResponse } from "./route-factory.js";
+
+describe("RouteBuilder threads types end-to-end", () => {
+    it("infers c.req.valid('json') to the body Zod type", {
+        timeout: 5000,
+    }, () => {
+        const Body = z.object({ name: z.string() });
+        const Resp = z.object({ id: z.string() });
+
+        const r = POST("/users")
+            .body(Body)
+            .response(successResponse(Resp))
+            .build();
+
+        // Type-level assertion: TypedRouteConfig is assignable to RouteConfig.
+        expectTypeOf(r).toMatchTypeOf<RouteConfig>();
+
+        const app = new OpenAPIHono();
+        app.openapi(r, (c) => {
+            const body = c.req.valid("json");
+            // Compile-time: body must be inferred as { name: string }.
+            expectTypeOf(body).toEqualTypeOf<{ name: string }>();
+            return c.json({ success: true as const, data: { id: "1" } }, 200);
+        });
+
+        expect(app.routes.length).toBeGreaterThan(0);
+    });
+
+    it("infers c.req.valid('param') to the params Zod type", {
+        timeout: 5000,
+    }, () => {
+        const Params = z.object({ id: z.string() });
+        const Resp = z.object({ ok: z.boolean() });
+
+        const r = POST("/items/:id")
+            .params(Params)
+            .response(successResponse(Resp))
+            .build();
+
+        const app = new OpenAPIHono();
+        app.openapi(r, (c) => {
+            const params = c.req.valid("param");
+            expectTypeOf(params).toEqualTypeOf<{ id: string }>();
+            return c.json({ success: true as const, data: { ok: true } }, 200);
+        });
+
+        expect(app.routes.length).toBeGreaterThan(0);
+    });
+});

packages/api-stack/api/api-openapi/src/route-factory/route-factory.test.ts

@@ -0,0 +1,210 @@
+import { OpenAPIHono, z } from "@hono/zod-openapi";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import {
+    DELETE,
+    ErrorResponseSchema,
+    errorResponse,
+    GET,
+    PATCH,
+    POST,
+    PUT,
+    paginatedResponse,
+    RouteBuilder,
+    route,
+    StandardResponses,
+    successResponse,
+} from "./route-factory.js";
+
+describe("RouteBuilder", () => {
+    it("builds a minimal GET with response", { timeout: 5000 }, () => {
+        const r = GET("/x")
+            .response(z.object({ ok: z.boolean() }))
+            .build();
+        expect(r.method).toBe("get");
+        expect(r.path).toBe("/x");
+        expect(r.responses).toBeDefined();
+    });
+
+    it("threads params/query/body through .build()", { timeout: 5000 }, () => {
+        const Params = z.object({ id: z.string() });
+        const Query = z.object({ q: z.string() });
+        const Body = z.object({ v: z.number() });
+        const r = POST("/y")
+            .params(Params)
+            .query(Query)
+            .body(Body)
+            .response(z.object({ ok: z.boolean() }))
+            .build();
+        expect(r.request).toBeDefined();
+    });
+
+    it("propagates tags / summary / description / operationId", {
+        timeout: 5000,
+    }, () => {
+        const r = PUT("/z")
+            .tags("a", "b")
+            .summary("S")
+            .description("D")
+            .operationId("op")
+            .response(z.object({}))
+            .build();
+        expect(r.tags).toEqual(["a", "b"]);
+        expect(r.summary).toBe("S");
+        expect(r.description).toBe("D");
+        expect(r.operationId).toBe("op");
+    });
+
+    it("marks deprecated when called", { timeout: 5000 }, () => {
+        const r = DELETE("/d").deprecated().response(z.object({})).build();
+        expect(r.deprecated).toBe(true);
+    });
+
+    it("passes security through", { timeout: 5000 }, () => {
+        const r = PATCH("/p")
+            .security([{ Bearer: ["admin"] }])
+            .response(z.object({}))
+            .build();
+        expect(r.security).toEqual([{ Bearer: ["admin"] }]);
+    });
+
+    it("build() without .response() falls back to a permissive schema", {
+        timeout: 5000,
+    }, () => {
+        const r = GET("/no-response").build();
+        expect(r.responses).toBeDefined();
+        const ok = (r.responses as Record<string, unknown>)["200"];
+        expect(ok).toBeDefined();
+    });
+
+    it("route() factory equals direct constructor", { timeout: 5000 }, () => {
+        const a = route("get", "/eq").response(z.object({})).build();
+        const b = new RouteBuilder("get", "/eq").response(z.object({})).build();
+        expect(a.method).toBe(b.method);
+        expect(a.path).toBe(b.path);
+    });
+
+    it("build produces TypedRouteConfig assignable to RouteConfig", {
+        timeout: 5000,
+    }, () => {
+        const Body = z.object({ name: z.string() });
+        const Response = z.object({ id: z.string() });
+        const r = POST("/users")
+            .body(Body)
+            .response(successResponse(Response))
+            .build();
+        // Real Hono app must accept the route without compile-time complaint.
+        const app = new OpenAPIHono();
+        app.openapi(r, (c) =>
+            c.json({ success: true as const, data: { id: "1" } }, 200)
+        );
+        expect(app.routes.some((rt) => rt.path === "/users")).toBe(true);
+    });
+});
+
+describe("ErrorResponseSchema", () => {
+    it("accepts SuaveplanError.toJSON() output", { timeout: 5000 }, () => {
+        const json = {
+            success: false,
+            error: {
+                code: "USER.NOT_FOUND",
+                message: "missing",
+                timestamp: new Date().toISOString(),
+            },
+        };
+        expect(ErrorResponseSchema.safeParse(json).success).toBe(true);
+    });
+
+    it("accepts cause + details + requestId", { timeout: 5000 }, () => {
+        const json = {
+            success: false,
+            error: {
+                code: "X.Y",
+                message: "msg",
+                details: { field: "foo" },
+                requestId: "req-1",
+                timestamp: "2024-01-01T00:00:00.000Z",
+                cause: { code: "Z.A", message: "inner" },
+            },
+        };
+        expect(ErrorResponseSchema.safeParse(json).success).toBe(true);
+    });
+
+    it("rejects success:true payload", { timeout: 5000 }, () => {
+        const json = {
+            success: true,
+            error: {
+                code: "X",
+                message: "m",
+                timestamp: new Date().toISOString(),
+            },
+        };
+        expect(ErrorResponseSchema.safeParse(json).success).toBe(false);
+    });
+
+    it("requires timestamp", { timeout: 5000 }, () => {
+        const json = { success: false, error: { code: "X", message: "m" } };
+        expect(ErrorResponseSchema.safeParse(json).success).toBe(false);
+    });
+});
+
+describe("successResponse / paginatedResponse / errorResponse", () => {
+    it("successResponse wraps the data schema", { timeout: 5000 }, () => {
+        const env = successResponse(z.object({ id: z.string() }));
+        const ok = env.safeParse({ success: true, data: { id: "1" } });
+        expect(ok.success).toBe(true);
+    });
+
+    it("paginatedResponse adds array data + meta", { timeout: 5000 }, () => {
+        const env = paginatedResponse(z.object({ id: z.string() }));
+        const ok = env.safeParse({
+            success: true,
+            data: [{ id: "a" }],
+            meta: {
+                page: 1,
+                limit: 10,
+                total: 1,
+                totalPages: 1,
+                hasNext: false,
+                hasPrevious: false,
+            },
+        });
+        expect(ok.success).toBe(true);
+    });
+
+    it("errorResponse returns the standard response triple", {
+        timeout: 5000,
+    }, () => {
+        const e = errorResponse("Custom");
+        expect(e.description).toBe("Custom");
+        expect(e.content["application/json"].schema).toBe(ErrorResponseSchema);
+    });
+});
+
+describe("StandardResponses", () => {
+    it("covers 422/429/503/504", { timeout: 5000 }, () => {
+        expect(StandardResponses[422]).toBeDefined();
+        expect(StandardResponses[429]).toBeDefined();
+        expect(StandardResponses[503]).toBeDefined();
+        expect(StandardResponses[504]).toBeDefined();
+    });
+
+    it("every entry references ErrorResponseSchema", { timeout: 5000 }, () => {
+        for (const status of [
+            400, 401, 403, 404, 409, 422, 429, 500, 503, 504,
+        ] as const) {
+            expect(
+                StandardResponses[status].content["application/json"].schema
+            ).toBe(ErrorResponseSchema);
+        }
+    });
+
+    it("every entry carries a description", { timeout: 5000 }, () => {
+        for (const status of [
+            400, 401, 403, 404, 409, 422, 429, 500, 503, 504,
+        ] as const) {
+            expect(
+                StandardResponses[status].description.length
+            ).toBeGreaterThan(0);
+        }
+    });
+});

packages/api-stack/api/api-openapi/src/route-factory/route-factory.ts

@@ -0,0 +1,335 @@
+import type { RouteConfig } from "@hono/zod-openapi";
+import { createRoute, z } from "@hono/zod-openapi";
+
+/**
+ * Discriminated HTTP method literal accepted by {@link route} and the
+ * shorthand factories (`GET`/`POST`/`PUT`/`PATCH`/`DELETE`).
+ */
+export type RouteMethod = "get" | "post" | "put" | "patch" | "delete";
+
+/**
+ * Route definition options accumulated by {@link RouteBuilder} before
+ * `.build()` produces a {@link TypedRouteConfig}.
+ */
+export interface RouteOptions<
+    TParams extends z.ZodType = z.ZodUndefined,
+    TQuery extends z.ZodType = z.ZodUndefined,
+    TBody extends z.ZodType = z.ZodUndefined,
+    TResponse extends z.ZodType = z.ZodUndefined,
+> {
+    method: RouteMethod;
+    path: string;
+    tags: string[];
+    summary?: string;
+    description?: string;
+    operationId?: string;
+    deprecated?: boolean;
+    security?: Array<Record<string, string[]>>;
+    params?: TParams;
+    query?: TQuery;
+    body?: TBody;
+    response: TResponse;
+}
+
+/**
+ * Wire shape of every error response — 1:1 match for
+ * `SuaveplanError.toJSON()`. The `cause` field is included so consumers
+ * can surface chained errors when present.
+ */
+export const ErrorResponseSchema = z.object({
+    success: z.literal(false),
+    error: z.object({
+        code: z.string(),
+        message: z.string(),
+        details: z.record(z.string(), z.unknown()).optional(),
+        requestId: z.string().optional(),
+        timestamp: z.string(),
+        cause: z.unknown().optional(),
+    }),
+});
+
+export type ErrorResponse = z.infer<typeof ErrorResponseSchema>;
+
+/**
+ * Wrap an arbitrary data schema in the standard success envelope.
+ */
+export function successResponse<T extends z.ZodType>(dataSchema: T) {
+    return z.object({
+        success: z.literal(true),
+        data: dataSchema,
+    });
+}
+
+/**
+ * Build the `{ description, content: { "application/json": { schema } } }`
+ * triple expected by Hono/OpenAPI for an error response.
+ */
+export function errorResponse(description: string) {
+    return {
+        description,
+        content: {
+            "application/json": {
+                schema: ErrorResponseSchema,
+            },
+        },
+    };
+}
+
+/**
+ * Wrap an item schema in a paginated envelope (`data` is an array and
+ * `meta` carries page/limit/total/totalPages/hasNext/hasPrevious).
+ */
+export function paginatedResponse<T extends z.ZodType>(itemSchema: T) {
+    return z.object({
+        success: z.literal(true),
+        data: z.array(itemSchema),
+        meta: z.object({
+            page: z.number(),
+            limit: z.number(),
+            total: z.number(),
+            totalPages: z.number(),
+            hasNext: z.boolean(),
+            hasPrevious: z.boolean(),
+        }),
+    });
+}
+
+/**
+ * Standard error responses covering the full SuaveplanError statusCode
+ * range. Widened from upstream's 400/401/403/404/500 set to include
+ * 409, 422, 429, 503, 504 — every status that genesis SuaveplanError
+ * can emit.
+ */
+export const StandardResponses = {
+    400: {
+        description: "Bad Request",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    401: {
+        description: "Unauthorized",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    403: {
+        description: "Forbidden",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    404: {
+        description: "Not Found",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    409: {
+        description: "Conflict",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    422: {
+        description: "Unprocessable Entity",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    429: {
+        description: "Too Many Requests",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    500: {
+        description: "Internal Server Error",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    503: {
+        description: "Service Unavailable",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+    504: {
+        description: "Gateway Timeout",
+        content: { "application/json": { schema: ErrorResponseSchema } },
+    },
+} as const;
+
+/**
+ * Typed route config that preserves schema generics through the builder
+ * chain. Assignable to `@hono/zod-openapi`'s `RouteConfig` so
+ * `app.openapi(route, handler)` infers `c.req.valid("…")` types.
+ *
+ * Uses `Omit + intersection` to ensure `request` is non-optional —
+ * required for Hono's `InputType*` conditional-type matching.
+ */
+export type TypedRouteConfig<
+    TParams extends z.ZodType = z.ZodUndefined,
+    TQuery extends z.ZodType = z.ZodUndefined,
+    TBody extends z.ZodType = z.ZodUndefined,
+    TResponse extends z.ZodType = z.ZodUndefined,
+> = Omit<RouteConfig, "request"> & {
+    request: (TParams extends z.ZodUndefined ? object : { params: TParams }) &
+        (TQuery extends z.ZodUndefined ? object : { query: TQuery }) &
+        (TBody extends z.ZodUndefined
+            ? object
+            : {
+                  body: {
+                      content: { "application/json": { schema: TBody } };
+                  };
+              });
+    _resp: TResponse;
+};
+
+/**
+ * Fluent route builder. Each `.params/.query/.body/.response` call
+ * returns a new generic instantiation so the final `.build()` result
+ * carries all four schema types.
+ */
+export class RouteBuilder<
+    TParams extends z.ZodType = z.ZodUndefined,
+    TQuery extends z.ZodType = z.ZodUndefined,
+    TBody extends z.ZodType = z.ZodUndefined,
+    TResponse extends z.ZodType = z.ZodUndefined,
+> {
+    private readonly state: {
+        method: RouteMethod;
+        path: string;
+        tags?: string[];
+        summary?: string;
+        description?: string;
+        operationId?: string;
+        deprecated?: boolean;
+        security?: Array<Record<string, string[]>>;
+        params?: z.ZodType;
+        query?: z.ZodType;
+        body?: z.ZodType;
+        response?: z.ZodType;
+    };
+
+    public constructor(method: RouteMethod, path: string) {
+        this.state = { method, path };
+    }
+
+    public tags(...tags: string[]): this {
+        this.state.tags = tags;
+        return this;
+    }
+
+    public summary(summary: string): this {
+        this.state.summary = summary;
+        return this;
+    }
+
+    public description(description: string): this {
+        this.state.description = description;
+        return this;
+    }
+
+    public operationId(id: string): this {
+        this.state.operationId = id;
+        return this;
+    }
+
+    public deprecated(): this {
+        this.state.deprecated = true;
+        return this;
+    }
+
+    public security(security: Array<Record<string, string[]>>): this {
+        this.state.security = security;
+        return this;
+    }
+
+    public params<T extends z.ZodType>(
+        schema: T
+    ): RouteBuilder<T, TQuery, TBody, TResponse> {
+        this.state.params = schema;
+        return this as unknown as RouteBuilder<T, TQuery, TBody, TResponse>;
+    }
+
+    public query<T extends z.ZodType>(
+        schema: T
+    ): RouteBuilder<TParams, T, TBody, TResponse> {
+        this.state.query = schema;
+        return this as unknown as RouteBuilder<TParams, T, TBody, TResponse>;
+    }
+
+    public body<T extends z.ZodType>(
+        schema: T
+    ): RouteBuilder<TParams, TQuery, T, TResponse> {
+        this.state.body = schema;
+        return this as unknown as RouteBuilder<TParams, TQuery, T, TResponse>;
+    }
+
+    public response<T extends z.ZodType>(
+        schema: T
+    ): RouteBuilder<TParams, TQuery, TBody, T> {
+        this.state.response = schema;
+        return this as unknown as RouteBuilder<TParams, TQuery, TBody, T>;
+    }
+
+    public build(): TypedRouteConfig<TParams, TQuery, TBody, TResponse> {
+        const request: Record<string, unknown> = {};
+        if (this.state.params) request["params"] = this.state.params;
+        if (this.state.query) request["query"] = this.state.query;
+        if (this.state.body) {
+            request["body"] = {
+                content: {
+                    "application/json": { schema: this.state.body },
+                },
+            };
+        }
+
+        const responseSchema = this.state.response ?? z.unknown();
+
+        const config = {
+            method: this.state.method,
+            path: this.state.path,
+            ...(this.state.tags !== undefined ? { tags: this.state.tags } : {}),
+            ...(this.state.summary !== undefined
+                ? { summary: this.state.summary }
+                : {}),
+            ...(this.state.description !== undefined
+                ? { description: this.state.description }
+                : {}),
+            ...(this.state.operationId !== undefined
+                ? { operationId: this.state.operationId }
+                : {}),
+            ...(this.state.deprecated !== undefined
+                ? { deprecated: this.state.deprecated }
+                : {}),
+            ...(this.state.security !== undefined
+                ? { security: this.state.security }
+                : {}),
+            ...(Object.keys(request).length > 0 ? { request } : {}),
+            responses: {
+                200: {
+                    description: "Success",
+                    content: {
+                        "application/json": { schema: responseSchema },
+                    },
+                },
+                ...StandardResponses,
+            },
+        } as Parameters<typeof createRoute>[0];
+
+        return createRoute(config) as unknown as TypedRouteConfig<
+            TParams,
+            TQuery,
+            TBody,
+            TResponse
+        >;
+    }
+}
+
+/**
+ * Create a {@link RouteBuilder} for the given method/path.
+ */
+export function route(method: RouteMethod, path: string): RouteBuilder {
+    return new RouteBuilder(method, path);
+}
+
+/** Shorthand for `route("get", path)`. */
+export const GET = (path: string): RouteBuilder =>
+    new RouteBuilder("get", path);
+/** Shorthand for `route("post", path)`. */
+export const POST = (path: string): RouteBuilder =>
+    new RouteBuilder("post", path);
+/** Shorthand for `route("put", path)`. */
+export const PUT = (path: string): RouteBuilder =>
+    new RouteBuilder("put", path);
+/** Shorthand for `route("patch", path)`. */
+export const PATCH = (path: string): RouteBuilder =>
+    new RouteBuilder("patch", path);
+/** Shorthand for `route("delete", path)`. */
+export const DELETE = (path: string): RouteBuilder =>
+    new RouteBuilder("delete", path);

packages/api-stack/api/api-openapi/src/route-factory/standard-responses.test.ts

@@ -0,0 +1,20 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { ErrorResponseSchema, StandardResponses } from "./route-factory.js";
+
+describe("StandardResponses widened set", () => {
+    it("covers 422/429/503/504", { timeout: 5000 }, () => {
+        const keys = Object.keys(StandardResponses);
+        expect(keys).toContain("422");
+        expect(keys).toContain("429");
+        expect(keys).toContain("503");
+        expect(keys).toContain("504");
+    });
+
+    it("every entry references ErrorResponseSchema", { timeout: 5000 }, () => {
+        for (const [, entry] of Object.entries(StandardResponses)) {
+            expect(entry.content["application/json"].schema).toBe(
+                ErrorResponseSchema
+            );
+        }
+    });
+});

packages/api-stack/api/api-openapi/src/schema-registry/common-schemas.md

@@ -0,0 +1,95 @@
+# common-schemas
+
+## Purpose
+
+Library of common Zod schemas decorated with OpenAPI `example` metadata.
+Covers the universal HTTP query / path / pagination primitives that
+every API plugin reaches for — UUID, email, URL, ISO datetime, signed
+and unsigned integers, page/limit/sort order. Pulling these into a
+single module ensures every plugin documents the same constraints,
+prevents drift, and makes the OpenAPI spec consistent across the entire
+multi-plugin server.
+
+The schemas are exported as a single `CommonSchemas` const object so
+consumers can spread, destructure, or `.openapi(...)`-extend any subset.
+They are deliberately not pre-registered against any `SchemaRegistry` —
+each consumer chooses whether (and under which name) to register them.
+
+## Features
+
+- `uuid`, `email`, `url`, `datetime` — string formats with examples.
+- `positiveInt`, `nonNegativeInt` — integer constraints.
+- `page` / `limit` — coercing pagination inputs with sane defaults.
+- `sortOrder` — `"asc" | "desc"` enum, default `"desc"`.
+- Every entry carries an OpenAPI `example` so the generated spec is rich.
+
+## Usage: Basic
+
+```ts
+import z from "zod";
+import { CommonSchemas } from "@suaveplan/api-openapi/schema-registry";
+
+const ListQuery = z.object({
+    page: CommonSchemas.page,
+    limit: CommonSchemas.limit,
+    sort: CommonSchemas.sortOrder,
+});
+```
+
+## Usage: Advanced
+
+```ts
+import z from "zod";
+import {
+    CommonSchemas,
+    createSchemaRegistry,
+} from "@suaveplan/api-openapi/schema-registry";
+
+const registry = createSchemaRegistry();
+
+// Register pagination primitives once under shared names so OpenAPI emits
+// `#/components/schemas/pagination.page` references rather than inlining
+// the same constraint in every operation.
+registry.register("pagination.page", CommonSchemas.page);
+registry.register("pagination.limit", CommonSchemas.limit);
+registry.register("pagination.sortOrder", CommonSchemas.sortOrder);
+
+const ListUsersQuery = z.object({
+    page: registry.get("pagination.page")!,
+    limit: registry.get("pagination.limit")!,
+    sort: registry.get("pagination.sortOrder")!,
+    q: z.string().optional(),
+});
+```
+
+## API Reference
+
+- `CommonSchemas.uuid: ZodString` — UUID string with example.
+- `CommonSchemas.email: ZodString` — email string.
+- `CommonSchemas.url: ZodString` — URL string.
+- `CommonSchemas.datetime: ZodString` — ISO-8601 datetime.
+- `CommonSchemas.positiveInt: ZodNumber` — `> 0`, integer.
+- `CommonSchemas.nonNegativeInt: ZodNumber` — `≥ 0`, integer.
+- `CommonSchemas.page: ZodCoerce<number>` — `min 1`, default `1`.
+- `CommonSchemas.limit: ZodCoerce<number>` — `min 1, max 100`, default `20`.
+- `CommonSchemas.sortOrder: ZodEnum<"asc" | "desc">` — default `"desc"`.
+
+## Implementation Notes
+
+`page` and `limit` use `z.coerce.number()` rather than `z.number()` so
+they accept query-string inputs (always strings on the wire). Without
+coercion every plugin would have to wrap them in `.transform(Number)`
+manually, defeating the point of a shared catalogue.
+
+The `.openapi({ example: ... })` annotation surfaces in the generated
+spec without affecting validation. Consumers that want richer
+descriptions (`{ description: "..." }`) call `.openapi(...)` on a copy
+rather than mutating the shared schema.
+
+`sortOrder` defaults to `"desc"` because the most common pagination
+pattern is "latest first". Plugins that want a different default override
+locally with `CommonSchemas.sortOrder.default("asc")`.
+
+`CommonSchemas` is `as const` — TypeScript surfaces every field with its
+narrowest literal type. Consumers can `typeof CommonSchemas` to derive
+per-field types without importing each schema individually.

packages/api-stack/api/api-openapi/src/schema-registry/common-schemas.ts

@@ -0,0 +1,53 @@
+import { z } from "@hono/zod-openapi";
+
+/**
+ * Common reusable Zod schemas decorated with OpenAPI metadata (examples).
+ *
+ * These are not registered against any schema registry by default —
+ * consumers compose them into their own registries as needed. The
+ * shapes match the most common HTTP query / path / pagination
+ * primitives so plugins do not need to reinvent the constraints.
+ */
+export const CommonSchemas = {
+    /** RFC 4122 UUID string. */
+    uuid: z
+        .string()
+        .uuid()
+        .openapi({ example: "123e4567-e89b-12d3-a456-426614174000" }),
+
+    /** RFC 5322 email string. */
+    email: z.string().email().openapi({ example: "user@example.com" }),
+
+    /** Absolute URL string. */
+    url: z.string().url().openapi({ example: "https://example.com" }),
+
+    /** ISO-8601 datetime string. */
+    datetime: z
+        .string()
+        .datetime()
+        .openapi({ example: "2024-01-15T10:30:00Z" }),
+
+    /** Positive integer (> 0). */
+    positiveInt: z.number().int().positive(),
+
+    /** Non-negative integer (≥ 0). */
+    nonNegativeInt: z.number().int().nonnegative(),
+
+    /** Pagination page number (1-based). Coerces from query strings. */
+    page: z.coerce.number().int().min(1).default(1).openapi({ example: 1 }),
+
+    /** Pagination limit (1–100, default 20). Coerces from query strings. */
+    limit: z.coerce
+        .number()
+        .int()
+        .min(1)
+        .max(100)
+        .default(20)
+        .openapi({ example: 20 }),
+
+    /** Sort order — ascending or descending, default descending. */
+    sortOrder: z
+        .enum(["asc", "desc"])
+        .default("desc")
+        .openapi({ example: "desc" }),
+} as const;

packages/api-stack/api/api-openapi/src/schema-registry/index.ts

@@ -0,0 +1,6 @@
+export { CommonSchemas } from "./common-schemas.js";
+export {
+    createSchemaRegistry,
+    defineSchema,
+    SchemaRegistry,
+} from "./schema-registry.js";

packages/api-stack/api/api-openapi/src/schema-registry/schema-registry.md

@@ -0,0 +1,115 @@
+# schema-registry
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Instance-based registry for reusable Zod schemas. Each schema is bound
+to a stable name and may be derived into related shapes via
+`.extend/.partial/.pick/.omit`. The registry is deliberately
+instance-only — there is no module-level singleton — so multi-tenant
+servers and parallel tests cannot accidentally share state. Calls into
+the derivation helpers raise typed `OpenAPIError`s when the base name
+is unknown or refers to a non-`ZodObject` schema, replacing upstream's
+silent `undefined` return.
+
+## Features
+
+- `register(name, schema, description?)` / `get(name)` / `has(name)` / `getDescription(name)`.
+- `getNames()`, `getAll()`, `remove(name)`, `clear()`.
+- `extend(baseName, name, extension)`, `partial(baseName, name)`,
+  `pick(baseName, name, keys[])`, `omit(baseName, name, keys[])`.
+- `createSchemaRegistry()` factory — no global accessor.
+- `defineSchema(schema, meta, registry)` — registry argument is required.
+- Typed `OPENAPI.SCHEMA_NOT_FOUND` / `OPENAPI.INVALID_BASE_SCHEMA` errors from derivation helpers.
+
+## Usage: Basic
+
+```ts
+import z from "zod";
+import {
+    createSchemaRegistry,
+    defineSchema,
+} from "@suaveplan/api-openapi/schema-registry";
+
+const registry = createSchemaRegistry();
+defineSchema(z.object({ id: z.string(), email: z.string() }), { name: "User" }, registry);
+const User = registry.get("User");
+```
+
+## Usage: Advanced
+
+```ts
+import z from "zod";
+import {
+    createSchemaRegistry,
+} from "@suaveplan/api-openapi/schema-registry";
+
+const registry = createSchemaRegistry();
+registry.register(
+    "User",
+    z.object({
+        id: z.string().uuid(),
+        email: z.string().email(),
+        password: z.string(),
+    }),
+    "Internal user shape including hashed password"
+);
+
+// Public shape — drop `password`.
+const UserPublic = registry.omit("User", "UserPublic", ["password"]);
+
+// Patch shape — every field optional.
+const UserPatch = registry.partial("User", "UserPatch");
+
+// Extended shape — add audit field.
+const UserAudit = registry.extend("User", "UserAudit", {
+    lastSeenAt: z.string().datetime(),
+});
+
+console.log(registry.getNames()); // ["User","UserPublic","UserPatch","UserAudit"]
+```
+
+## API Reference
+
+- `class SchemaRegistry`
+  - `register<T>(name, schema, description?): T`
+  - `get<T>(name): T | undefined`
+  - `has(name): boolean`
+  - `getDescription(name): string | undefined`
+  - `getNames(): string[]`
+  - `getAll(): Map<string, z.ZodType>`
+  - `remove(name): boolean`
+  - `clear(): void`
+  - `extend(baseName, name, extension): z.ZodObject` — throws `OPENAPI.SCHEMA_NOT_FOUND` or `OPENAPI.INVALID_BASE_SCHEMA`
+  - `partial(baseName, name): z.ZodObject` — same throw semantics
+  - `pick(baseName, name, keys[]): z.ZodObject` — same throw semantics
+  - `omit(baseName, name, keys[]): z.ZodObject` — same throw semantics
+- `function createSchemaRegistry(): SchemaRegistry`
+- `function defineSchema<T>(schema: T, meta: {name, description?}, registry: SchemaRegistry): T`
+
+## Implementation Notes
+
+`requireObjectBase` is the central guard. It throws
+`OPENAPI.SCHEMA_NOT_FOUND` when the name is unknown and
+`OPENAPI.INVALID_BASE_SCHEMA` when the registered schema is not a
+`ZodObject`. Both branches carry the base name in the error context so
+the call site can be diagnosed without a stack walk.
+
+`pick` and `omit` take a `string[]` keys list rather than the Zod
+shape-mask object because OpenAPI consumers usually serialise key lists
+from configuration, not from compile-time literals. The shape mask is
+constructed internally to match Zod's expected input.
+
+`defineSchema` requires the `registry` argument by position (third arg).
+Calling it without is a compile error. This is the deliberate behavioural
+divergence from upstream's `defineSchema(schema, meta)` which always
+wrote to a process-global registry — a footgun that turned every test
+file into a coupled neighbour.
+
+The class uses `private readonly` Maps for `schemas` and `descriptions`.
+External mutation is impossible without going through `register` /
+`remove` / `clear`, which gives the registry well-defined ownership of
+both maps and lets `getAll()` safely return a fresh copy.

packages/api-stack/api/api-openapi/src/schema-registry/schema-registry.spec-conformance.test.ts

@@ -0,0 +1,47 @@
+import { readFileSync } from "node:fs";
+import { z } from "@hono/zod-openapi";
+import { describe, expect, expectTypeOf, it } from "@suaveplan/testing/runner";
+import * as Barrel from "../index.js";
+import {
+    createSchemaRegistry,
+    defineSchema,
+    type SchemaRegistry,
+} from "./schema-registry.js";
+
+describe("SchemaRegistry — no global singleton", () => {
+    it("no global singleton exported", { timeout: 5000 }, () => {
+        // The barrel must not surface a `getSchemaRegistry` accessor or
+        // any `globalSchemaRegistry` symbol.
+        const exportedKeys = Object.keys(Barrel);
+        expect(exportedKeys).not.toContain("getSchemaRegistry");
+        expect(exportedKeys).not.toContain("globalSchemaRegistry");
+    });
+
+    it("two registries are independent", { timeout: 5000 }, () => {
+        const a = createSchemaRegistry();
+        const b = createSchemaRegistry();
+        a.register("X", z.string());
+        expect(a.has("X")).toBe(true);
+        expect(b.has("X")).toBe(false);
+    });
+
+    it("source file does not declare a singleton", { timeout: 5000 }, () => {
+        const src = readFileSync(
+            new URL("./schema-registry.ts", import.meta.url),
+            "utf8"
+        );
+        expect(src.includes("globalSchemaRegistry")).toBe(false);
+        expect(src.includes("getSchemaRegistry")).toBe(false);
+    });
+
+    it("defineSchema requires explicit registry argument", {
+        timeout: 5000,
+    }, () => {
+        const registry = createSchemaRegistry();
+        // Type-level: the third parameter is required (not optional).
+        expectTypeOf(defineSchema).parameter(2).toEqualTypeOf<SchemaRegistry>();
+
+        const out = defineSchema(z.string(), { name: "X" }, registry);
+        expect(registry.get("X")).toBe(out);
+    });
+});

packages/api-stack/api/api-openapi/src/schema-registry/schema-registry.test.ts

@@ -0,0 +1,233 @@
+import { z } from "@hono/zod-openapi";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import { CommonSchemas } from "./common-schemas.js";
+import {
+    createSchemaRegistry,
+    defineSchema,
+    SchemaRegistry,
+} from "./schema-registry.js";
+
+describe("SchemaRegistry — basic CRUD", () => {
+    it("register + get round-trips a schema", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        const s = z.object({ id: z.string() });
+        r.register("User", s, "a user");
+        expect(r.get("User")).toBe(s);
+        expect(r.getDescription("User")).toBe("a user");
+        expect(r.has("User")).toBe(true);
+    });
+
+    it("getNames + getAll reflect registrations", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("A", z.string());
+        r.register("B", z.number());
+        expect(r.getNames().sort()).toEqual(["A", "B"]);
+        const all = r.getAll();
+        expect(all.size).toBe(2);
+        all.delete("A"); // confirm defensive copy
+        expect(r.getNames().sort()).toEqual(["A", "B"]);
+    });
+
+    it("remove drops both schema + description", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("X", z.string(), "d");
+        expect(r.remove("X")).toBe(true);
+        expect(r.has("X")).toBe(false);
+        expect(r.getDescription("X")).toBeUndefined();
+        expect(r.remove("X")).toBe(false);
+    });
+
+    it("clear empties the registry", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("A", z.string());
+        r.register("B", z.number(), "b");
+        r.clear();
+        expect(r.getNames()).toEqual([]);
+        expect(r.getDescription("B")).toBeUndefined();
+    });
+
+    it("register without description leaves description map empty", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        r.register("A", z.string());
+        expect(r.getDescription("A")).toBeUndefined();
+    });
+});
+
+describe("SchemaRegistry — derivation helpers", () => {
+    const buildBase = () =>
+        z.object({
+            id: z.string().uuid(),
+            email: z.string().email(),
+            password: z.string(),
+        });
+
+    it("extend derives + registers", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("User", buildBase());
+        const out = r.extend("User", "UserAudit", {
+            lastSeenAt: z.string().datetime(),
+        });
+        expect(out.shape["lastSeenAt"]).toBeDefined();
+        expect(r.get("UserAudit")).toBe(out);
+    });
+
+    it("partial derives + registers", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("User", buildBase());
+        const out = r.partial("User", "UserPatch");
+        expect(out.shape["id"]).toBeDefined();
+        const result = out.safeParse({});
+        expect(result.success).toBe(true);
+    });
+
+    it("pick derives + registers", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("User", buildBase());
+        const out = r.pick("User", "UserPublic", ["id", "email"]);
+        expect(Object.keys(out.shape).sort()).toEqual(["email", "id"]);
+    });
+
+    it("omit derives + registers", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("User", buildBase());
+        const out = r.omit("User", "UserPublic", ["password"]);
+        expect(Object.keys(out.shape).sort()).toEqual(["email", "id"]);
+    });
+
+    it("extend non-object raises OPENAPI_INVALID_BASE_SCHEMA", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        r.register("primitives.uuid", z.string().uuid());
+        let err: unknown;
+        try {
+            r.extend("primitives.uuid", "X", { extra: z.string() });
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(
+            OPENAPI_CODES.INVALID_BASE_SCHEMA
+        );
+    });
+
+    it("partial non-object raises INVALID_BASE_SCHEMA", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        r.register("p", z.string());
+        expect(() => r.partial("p", "x")).toThrow(OpenAPIError);
+    });
+
+    it("pick non-object raises INVALID_BASE_SCHEMA", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("p", z.string());
+        expect(() => r.pick("p", "x", ["k"])).toThrow(OpenAPIError);
+    });
+
+    it("omit non-object raises INVALID_BASE_SCHEMA", { timeout: 5000 }, () => {
+        const r = createSchemaRegistry();
+        r.register("p", z.string());
+        expect(() => r.omit("p", "x", ["k"])).toThrow(OpenAPIError);
+    });
+
+    it("derivation on missing base raises SCHEMA_NOT_FOUND", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        let err: unknown;
+        try {
+            r.extend("ghost", "x", { k: z.string() });
+        } catch (e) {
+            err = e;
+        }
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.SCHEMA_NOT_FOUND);
+    });
+});
+
+describe("createSchemaRegistry + defineSchema", () => {
+    it("createSchemaRegistry returns SchemaRegistry instance", {
+        timeout: 5000,
+    }, () => {
+        expect(createSchemaRegistry()).toBeInstanceOf(SchemaRegistry);
+    });
+
+    it("defineSchema registers against the explicit registry", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        const s = defineSchema(
+            z.object({ id: z.string() }),
+            { name: "X", description: "x" },
+            r
+        );
+        expect(r.get("X")).toBe(s);
+        expect(r.getDescription("X")).toBe("x");
+    });
+
+    it("defineSchema returns the original schema instance", {
+        timeout: 5000,
+    }, () => {
+        const r = createSchemaRegistry();
+        const original = z.string();
+        const out = defineSchema(original, { name: "S" }, r);
+        expect(out).toBe(original);
+    });
+});
+
+describe("CommonSchemas", () => {
+    it("uuid validates RFC 4122 strings", { timeout: 5000 }, () => {
+        expect(
+            CommonSchemas.uuid.safeParse("123e4567-e89b-12d3-a456-426614174000")
+                .success
+        ).toBe(true);
+        expect(CommonSchemas.uuid.safeParse("nope").success).toBe(false);
+    });
+
+    it("email rejects malformed inputs", { timeout: 5000 }, () => {
+        expect(CommonSchemas.email.safeParse("a@b.co").success).toBe(true);
+        expect(CommonSchemas.email.safeParse("notanemail").success).toBe(false);
+    });
+
+    it("url validates absolute URLs", { timeout: 5000 }, () => {
+        expect(CommonSchemas.url.safeParse("https://e.com").success).toBe(true);
+        expect(CommonSchemas.url.safeParse("nope").success).toBe(false);
+    });
+
+    it("datetime requires ISO-8601", { timeout: 5000 }, () => {
+        expect(
+            CommonSchemas.datetime.safeParse("2024-01-15T10:30:00Z").success
+        ).toBe(true);
+        expect(CommonSchemas.datetime.safeParse("not iso").success).toBe(false);
+    });
+
+    it("positiveInt rejects zero and negatives", { timeout: 5000 }, () => {
+        expect(CommonSchemas.positiveInt.safeParse(1).success).toBe(true);
+        expect(CommonSchemas.positiveInt.safeParse(0).success).toBe(false);
+        expect(CommonSchemas.positiveInt.safeParse(-1).success).toBe(false);
+    });
+
+    it("nonNegativeInt accepts zero", { timeout: 5000 }, () => {
+        expect(CommonSchemas.nonNegativeInt.safeParse(0).success).toBe(true);
+        expect(CommonSchemas.nonNegativeInt.safeParse(-1).success).toBe(false);
+    });
+
+    it("page coerces strings + defaults to 1", { timeout: 5000 }, () => {
+        expect(CommonSchemas.page.parse("3")).toBe(3);
+        expect(CommonSchemas.page.parse(undefined)).toBe(1);
+    });
+
+    it("limit clamps to 1..100 with default 20", { timeout: 5000 }, () => {
+        expect(CommonSchemas.limit.parse(undefined)).toBe(20);
+        expect(CommonSchemas.limit.safeParse(101).success).toBe(false);
+        expect(CommonSchemas.limit.safeParse(0).success).toBe(false);
+    });
+
+    it("sortOrder enum + default desc", { timeout: 5000 }, () => {
+        expect(CommonSchemas.sortOrder.parse(undefined)).toBe("desc");
+        expect(CommonSchemas.sortOrder.safeParse("nope").success).toBe(false);
+    });
+});

packages/api-stack/api/api-openapi/src/schema-registry/schema-registry.ts

@@ -0,0 +1,141 @@
+import { z } from "@hono/zod-openapi";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+
+/**
+ * Schema registry for reusable Zod schemas. Instance-based — there is
+ * no module-level singleton, which would conflict with parallel tests
+ * and multi-app deployments.
+ */
+export class SchemaRegistry {
+    private readonly schemas: Map<string, z.ZodType> = new Map();
+    private readonly descriptions: Map<string, string> = new Map();
+
+    public register<T extends z.ZodType>(
+        name: string,
+        schema: T,
+        description?: string
+    ): T {
+        this.schemas.set(name, schema);
+        if (description !== undefined) {
+            this.descriptions.set(name, description);
+        }
+        return schema;
+    }
+
+    public get<T extends z.ZodType = z.ZodType>(name: string): T | undefined {
+        return this.schemas.get(name) as T | undefined;
+    }
+
+    public has(name: string): boolean {
+        return this.schemas.has(name);
+    }
+
+    public getDescription(name: string): string | undefined {
+        return this.descriptions.get(name);
+    }
+
+    public getNames(): string[] {
+        return Array.from(this.schemas.keys());
+    }
+
+    public getAll(): Map<string, z.ZodType> {
+        return new Map(this.schemas);
+    }
+
+    public remove(name: string): boolean {
+        this.descriptions.delete(name);
+        return this.schemas.delete(name);
+    }
+
+    public clear(): void {
+        this.schemas.clear();
+        this.descriptions.clear();
+    }
+
+    public extend(
+        baseName: string,
+        name: string,
+        extension: z.ZodRawShape
+    ): z.ZodObject<z.ZodRawShape> {
+        const base = this.requireObjectBase(baseName);
+        const extended = base.extend(extension);
+        this.register(name, extended);
+        return extended;
+    }
+
+    public partial(baseName: string, name: string): z.ZodObject<z.ZodRawShape> {
+        const base = this.requireObjectBase(baseName);
+        const partial = base.partial();
+        this.register(name, partial);
+        return partial;
+    }
+
+    public pick(
+        baseName: string,
+        name: string,
+        keys: string[]
+    ): z.ZodObject<z.ZodRawShape> {
+        const base = this.requireObjectBase(baseName);
+        const mask = Object.fromEntries(keys.map((k) => [k, true])) as {
+            [K in keyof z.ZodRawShape]: true;
+        };
+        const picked = base.pick(mask);
+        this.register(name, picked);
+        return picked;
+    }
+
+    public omit(
+        baseName: string,
+        name: string,
+        keys: string[]
+    ): z.ZodObject<z.ZodRawShape> {
+        const base = this.requireObjectBase(baseName);
+        const mask = Object.fromEntries(keys.map((k) => [k, true])) as {
+            [K in keyof z.ZodRawShape]: true;
+        };
+        const omitted = base.omit(mask);
+        this.register(name, omitted);
+        return omitted;
+    }
+
+    private requireObjectBase(baseName: string): z.ZodObject<z.ZodRawShape> {
+        const base = this.schemas.get(baseName);
+        if (!base) {
+            throw new OpenAPIError(
+                OPENAPI_CODES.SCHEMA_NOT_FOUND,
+                `schema "${baseName}" is not registered`,
+                { context: { baseName } }
+            );
+        }
+        if (!(base instanceof z.ZodObject)) {
+            throw new OpenAPIError(
+                OPENAPI_CODES.INVALID_BASE_SCHEMA,
+                `schema "${baseName}" is not a ZodObject — extend/partial/pick/omit require an object base`,
+                { context: { baseName } }
+            );
+        }
+        return base as z.ZodObject<z.ZodRawShape>;
+    }
+}
+
+/**
+ * Factory — the only way to obtain a {@link SchemaRegistry}. There is
+ * deliberately no global accessor.
+ */
+export function createSchemaRegistry(): SchemaRegistry {
+    return new SchemaRegistry();
+}
+
+/**
+ * Register `schema` under `meta.name` in the supplied registry instance.
+ * The `registry` argument is required so the call site is explicit
+ * about which registry receives the schema — eliminates the "which
+ * global got it?" footgun of upstream's `defineSchema`.
+ */
+export function defineSchema<T extends z.ZodType>(
+    schema: T,
+    meta: { name: string; description?: string },
+    registry: SchemaRegistry
+): T {
+    return registry.register(meta.name, schema, meta.description);
+}

packages/api-stack/api/api-openapi/src/strictness/index.ts

@@ -0,0 +1,13 @@
+export {
+    __resetMissingSchemaCounter,
+    getMissingSchemaCounter,
+    type HostEnvironment,
+    MISSING_SCHEMA_COUNTER_NAME,
+    type MissingSchemaSlot,
+    OPENAPI_METER_NAME,
+    type ReportMissingSchemaInput,
+    type ResolveStrictnessInput,
+    reportMissingSchema,
+    resolveStrictness,
+    type StrictnessMode,
+} from "./strictness.js";

packages/api-stack/api/api-openapi/src/strictness/strictness.md

@@ -0,0 +1,101 @@
+# strictness
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`strictness` resolves the host's missing-schema policy for the OpenAPI
+emitter and applies it consistently across every route. It encodes the
+two-mode contract from the spec: `warn` (emit + warn + count) and
+`refuse-install` (raise before the plugin is installed). The same
+helper is wired into both the emitter and the host's plugin-install
+gate so missing schemas behave identically wherever they're detected.
+
+The module also owns the `api.openapi.missing_schema_total` OTel
+counter — without an OTel meter exporter wired into the host, missing
+schemas silently accumulate. Surfacing them as a per-plugin per-route
+labelled metric makes drift visible to anyone watching the
+observability stack.
+
+## Features
+
+- `resolveStrictness({ configured, environment })` — typed precedence
+  resolver. Configured value wins; otherwise `"production"` → refuse,
+  `"development"`/anything else → warn.
+- `reportMissingSchema(input)` — single chokepoint that either throws
+  or logs+counts. Accepts an injectable logger and counter so test
+  setups can assert exact behaviour with a real `MeterProvider`.
+- `getMissingSchemaCounter()` — lazy accessor over the package meter so
+  production callers do not need to thread the counter through.
+
+## Usage: Basic
+
+```ts
+import {
+    reportMissingSchema,
+    resolveStrictness,
+} from "@suaveplan/api-openapi/strictness";
+
+const mode = resolveStrictness({ environment: "production" });
+// "refuse-install"
+
+reportMissingSchema({
+    mode,
+    plugin: "billing",
+    method: "GET",
+    path: "/invoices/:id",
+    slot: "response",
+});
+// throws OpenAPIError(OPENAPI.MISSING_SCHEMA)
+```
+
+## Usage: Advanced
+
+```ts
+import { MeterProvider } from "@opentelemetry/sdk-metrics";
+import { metrics } from "@opentelemetry/api";
+import {
+    __resetMissingSchemaCounter,
+    reportMissingSchema,
+} from "@suaveplan/api-openapi/strictness";
+
+const provider = new MeterProvider();
+metrics.setGlobalMeterProvider(provider);
+__resetMissingSchemaCounter();
+
+const logger = { warn: (msg: string) => console.warn(msg) } as const;
+reportMissingSchema({
+    mode: "warn",
+    plugin: "billing",
+    method: "POST",
+    path: "/invoices",
+    slot: "request",
+    logger,
+});
+// → counter increments, logger.warn called
+```
+
+## API Reference
+
+- `StrictnessMode` — `"warn" | "refuse-install"`.
+- `HostEnvironment` — `"development" | "production"`.
+- `resolveStrictness(input) → StrictnessMode`.
+- `reportMissingSchema(input) → void` (throws on `refuse-install`).
+- `getMissingSchemaCounter() → Counter`.
+- `__resetMissingSchemaCounter()` — test-only seam.
+- Constants: `MISSING_SCHEMA_COUNTER_NAME`, `OPENAPI_METER_NAME`.
+
+## Implementation Notes
+
+- The counter is acquired lazily so registering the package side-effect
+  does not require an OTel SDK at import time. Tests reset the cache
+  via `__resetMissingSchemaCounter()` before binding a fresh
+  `MeterProvider`.
+- The counter labels — `plugin`, `route`, `slot` — match the spec's
+  scenario assertion (`{ plugin, route }`) and add `slot` so request
+  vs response misses can be distinguished without a second metric.
+- `LoggerLike.warn` is optional in the contract (`@suaveplan/types`);
+  the call is guarded with optional chaining so structured loggers that
+  only ship `info` + `error` still work.

packages/api-stack/api/api-openapi/src/strictness/strictness.test.ts

@@ -0,0 +1,187 @@
+import { metrics } from "@opentelemetry/api";
+import {
+    AggregationTemporality,
+    InMemoryMetricExporter,
+    MeterProvider,
+    PeriodicExportingMetricReader,
+} from "@opentelemetry/sdk-metrics";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { LoggerLike } from "@suaveplan/types";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+import {
+    __resetMissingSchemaCounter,
+    getMissingSchemaCounter,
+    MISSING_SCHEMA_COUNTER_NAME,
+    OPENAPI_METER_NAME,
+    reportMissingSchema,
+    resolveStrictness,
+} from "./strictness.js";
+
+function captureLogger(): {
+    logger: LoggerLike;
+    warns: Array<{ msg: string; ctx?: Readonly<Record<string, unknown>> }>;
+} {
+    const warns: Array<{
+        msg: string;
+        ctx?: Readonly<Record<string, unknown>>;
+    }> = [];
+    const logger: LoggerLike = {
+        debug: () => undefined,
+        info: () => undefined,
+        warn: (msg, ctx) => {
+            warns.push({ msg, ctx });
+        },
+        error: () => undefined,
+    };
+    return { logger, warns };
+}
+
+describe("resolveStrictness", () => {
+    it("explicit config wins", { timeout: 5000 }, () => {
+        expect(
+            resolveStrictness({
+                configured: "warn",
+                environment: "production",
+            })
+        ).toBe("warn");
+        expect(
+            resolveStrictness({
+                configured: "refuse-install",
+                environment: "development",
+            })
+        ).toBe("refuse-install");
+    });
+
+    it("production environment defaults to refuse-install", {
+        timeout: 5000,
+    }, () => {
+        expect(resolveStrictness({ environment: "production" })).toBe(
+            "refuse-install"
+        );
+    });
+
+    it("development environment defaults to warn", { timeout: 5000 }, () => {
+        expect(resolveStrictness({ environment: "development" })).toBe("warn");
+    });
+
+    it("unspecified environment defaults to warn", { timeout: 5000 }, () => {
+        expect(resolveStrictness({})).toBe("warn");
+    });
+});
+
+describe("reportMissingSchema", () => {
+    it("refuse-install raises OPENAPI_MISSING_SCHEMA", {
+        timeout: 5000,
+    }, () => {
+        let err: unknown;
+        try {
+            reportMissingSchema({
+                mode: "refuse-install",
+                plugin: "billing",
+                method: "get",
+                path: "/x",
+                slot: "response",
+            });
+        } catch (e) {
+            err = e;
+        }
+        expect(err).toBeInstanceOf(OpenAPIError);
+        expect((err as OpenAPIError).code).toBe(OPENAPI_CODES.MISSING_SCHEMA);
+        const ctx = (err as OpenAPIError).context as { plugin?: string };
+        expect(ctx.plugin).toBe("billing");
+    });
+
+    it("warn mode logs a warning and increments injected counter", {
+        timeout: 5000,
+    }, () => {
+        const { logger, warns } = captureLogger();
+        const incs: Array<{ value: number; attrs?: object }> = [];
+        const fakeCounter = {
+            add(value: number, attrs?: object) {
+                incs.push({ value, attrs });
+            },
+        } as unknown as ReturnType<typeof getMissingSchemaCounter>;
+
+        reportMissingSchema({
+            mode: "warn",
+            plugin: "billing",
+            method: "get",
+            path: "/x",
+            slot: "response",
+            logger,
+            counter: fakeCounter,
+        });
+
+        expect(warns).toHaveLength(1);
+        expect(warns[0]?.msg).toContain("missing");
+        expect(incs).toEqual([
+            {
+                value: 1,
+                attrs: { plugin: "billing", route: "GET /x", slot: "response" },
+            },
+        ]);
+    });
+
+    it("warn mode works without a logger", { timeout: 5000 }, () => {
+        const incs: Array<{ value: number; attrs?: object }> = [];
+        const fakeCounter = {
+            add(value: number, attrs?: object) {
+                incs.push({ value, attrs });
+            },
+        } as unknown as ReturnType<typeof getMissingSchemaCounter>;
+        reportMissingSchema({
+            mode: "warn",
+            plugin: "users",
+            method: "POST",
+            path: "/users",
+            slot: "request",
+            counter: fakeCounter,
+        });
+        expect(incs).toHaveLength(1);
+    });
+});
+
+describe("getMissingSchemaCounter / __resetMissingSchemaCounter — OTel integration", () => {
+    it("emits to a real MeterProvider", { timeout: 5000 }, async () => {
+        const exporter = new InMemoryMetricExporter(
+            AggregationTemporality.CUMULATIVE
+        );
+        const reader = new PeriodicExportingMetricReader({
+            exporter,
+            exportIntervalMillis: 60_000,
+        });
+        const provider = new MeterProvider({ readers: [reader] });
+        metrics.disable();
+        metrics.setGlobalMeterProvider(provider);
+        __resetMissingSchemaCounter();
+        const counter = getMissingSchemaCounter();
+        // Returns the cached counter on the second call.
+        expect(getMissingSchemaCounter()).toBe(counter);
+
+        reportMissingSchema({
+            mode: "warn",
+            plugin: "billing",
+            method: "GET",
+            path: "/invoices/{id}",
+            slot: "response",
+            counter,
+        });
+
+        await reader.forceFlush();
+        const collected = exporter.getMetrics();
+        const counterPoint = collected
+            .flatMap((rm) => rm.scopeMetrics)
+            .flatMap((sm) => sm.metrics)
+            .find((m) => m.descriptor.name === MISSING_SCHEMA_COUNTER_NAME);
+        expect(counterPoint).toBeDefined();
+        expect(counterPoint?.dataPoints[0]?.value).toBe(1);
+        const scope = collected
+            .flatMap((rm) => rm.scopeMetrics)
+            .map((sm) => sm.scope.name);
+        expect(scope).toContain(OPENAPI_METER_NAME);
+
+        await reader.shutdown();
+        metrics.disable();
+        __resetMissingSchemaCounter();
+    });
+});

packages/api-stack/api/api-openapi/src/strictness/strictness.ts

@@ -0,0 +1,125 @@
+import { type Counter, metrics } from "@opentelemetry/api";
+import type { LoggerLike } from "@suaveplan/types";
+import { OPENAPI_CODES, OpenAPIError } from "../error-codes/error-codes.js";
+
+/**
+ * Strictness modes accepted by the OpenAPI emitter. `warn` logs a
+ * warning and emits a placeholder; `refuse-install` raises before the
+ * plugin reaches `installed`.
+ */
+export type StrictnessMode = "warn" | "refuse-install";
+
+/**
+ * Effective host environment. Used by {@link resolveStrictness} to pick
+ * the production-safe default when the host config leaves the value
+ * unset.
+ */
+export type HostEnvironment = "development" | "production";
+
+/**
+ * Input accepted by {@link resolveStrictness}.
+ */
+export interface ResolveStrictnessInput {
+    readonly configured?: StrictnessMode;
+    readonly environment?: HostEnvironment;
+}
+
+/**
+ * Resolve the effective strictness setting.
+ *
+ * Precedence:
+ *
+ *  1. Explicit `host.openapi.strictness` from the host config.
+ *  2. `"refuse-install"` when the environment is `"production"`.
+ *  3. `"warn"` otherwise (including unknown environments — failing
+ *     loud in dev is friendlier than refusing to install).
+ */
+export function resolveStrictness(
+    input: ResolveStrictnessInput
+): StrictnessMode {
+    if (input.configured !== undefined) return input.configured;
+    if (input.environment === "production") return "refuse-install";
+    return "warn";
+}
+
+/** Counter name surfaced when {@link reportMissingSchema} logs a warning. */
+export const MISSING_SCHEMA_COUNTER_NAME = "api.openapi.missing_schema_total";
+
+/** Meter name used to acquire {@link MISSING_SCHEMA_COUNTER_NAME}. */
+export const OPENAPI_METER_NAME = "@suaveplan/api-openapi";
+
+/**
+ * Schema slot a route might be missing — used to attribute the counter
+ * for downstream alerting (request vs response is wildly different in
+ * severity).
+ */
+export type MissingSchemaSlot = "request" | "response";
+
+/**
+ * Input to {@link reportMissingSchema}.
+ */
+export interface ReportMissingSchemaInput {
+    readonly mode: StrictnessMode;
+    readonly plugin: string;
+    readonly method: string;
+    readonly path: string;
+    readonly slot: MissingSchemaSlot;
+    readonly logger?: LoggerLike;
+    readonly counter?: Counter;
+}
+
+let cachedCounter: Counter | undefined;
+
+/**
+ * Lazily acquire the shared `api.openapi.missing_schema_total` counter
+ * from the global meter provider. Tests inject their own counter via
+ * {@link ReportMissingSchemaInput.counter}; production code shares the
+ * cached one.
+ */
+export function getMissingSchemaCounter(): Counter {
+    if (cachedCounter === undefined) {
+        const meter = metrics.getMeter(OPENAPI_METER_NAME);
+        cachedCounter = meter.createCounter(MISSING_SCHEMA_COUNTER_NAME, {
+            description:
+                "Number of times a registered route was missing a request or response schema during OpenAPI emission",
+        });
+    }
+    return cachedCounter;
+}
+
+/**
+ * Reset the cached counter — used by tests that inject a fresh
+ * `MeterProvider` between cases so the next call re-resolves through the
+ * new provider. NOT for production use.
+ */
+export function __resetMissingSchemaCounter(): void {
+    cachedCounter = undefined;
+}
+
+/**
+ * Apply the configured strictness policy when a route is missing the
+ * requested schema slot.
+ *
+ * - `warn` — increment the counter, emit a `logger.warn` message, and
+ *   return so the emitter can substitute a placeholder.
+ * - `refuse-install` — raise {@link OPENAPI_CODES.MISSING_SCHEMA}.
+ *
+ * Returning a value is intentional: callers tee off the boolean to
+ * decide whether to fill in a `description: "schema-missing"` slot.
+ */
+export function reportMissingSchema(input: ReportMissingSchemaInput): void {
+    const { mode, plugin, method, path, slot, logger, counter } = input;
+    if (mode === "refuse-install") {
+        throw new OpenAPIError(
+            OPENAPI_CODES.MISSING_SCHEMA,
+            `route ${method.toUpperCase()} ${path} (plugin "${plugin}") is missing its ${slot} schema and strictness is "refuse-install"`,
+            { context: { plugin, method, path, slot } }
+        );
+    }
+    const c = counter ?? getMissingSchemaCounter();
+    c.add(1, { plugin, route: `${method.toUpperCase()} ${path}`, slot });
+    logger?.warn(
+        `[api-openapi] route ${method.toUpperCase()} ${path} (plugin "${plugin}") is missing its ${slot} schema; emitting placeholder`,
+        { plugin, method, path, slot }
+    );
+}

packages/api-stack/api/api-openapi/src/types/index.ts

@@ -0,0 +1,11 @@
+export {
+    HTTP_METHODS,
+    type HttpMethod,
+    type OpenAPIDocument,
+    type OpenAPIInfo,
+    type OpenAPIServer,
+    type Operation,
+    type PathItem,
+    type RegisteredRoute,
+    type SecurityScheme,
+} from "./openapi.js";

packages/api-stack/api/api-openapi/src/types/openapi.md

@@ -0,0 +1,84 @@
+# types/openapi
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Structural TypeScript types for OpenAPI 3.1 documents, supporting shapes
+(info / server / security scheme), registered-route metadata, and the
+HTTP-method literal union. These are the contract surfaces exchanged
+between the registry, the merger, the route factory, and external
+consumers — keeping them in one file makes the public surface easy to
+audit and prevents shape drift between modules.
+
+The types intentionally mirror just the slice of OpenAPI 3.1 that this
+package emits and merges. Full spec coverage (callbacks, links, runtime
+expressions) is out of scope — the package targets server-tier route
+documentation, not a general-purpose spec authoring tool.
+
+## Features
+
+- `OpenAPIInfo`, `OpenAPIServer`, `SecurityScheme` — top-level document atoms.
+- `RegisteredRoute` — registry-internal metadata for a single registered route.
+- `Operation`, `PathItem`, `OpenAPIDocument` — structural document shape used by the merger.
+- `HttpMethod` literal union + `HTTP_METHODS` readonly array.
+- Open-ended `x-${string}` index signatures so vendor extensions pass through without weakening field types.
+
+## Usage: Basic
+
+```ts
+import type { OpenAPIDocument } from "@suaveplan/api-openapi/types";
+
+const doc: OpenAPIDocument = {
+    openapi: "3.1.0",
+    info: { title: "My API", version: "1.0.0" },
+    paths: {},
+};
+```
+
+## Usage: Advanced
+
+```ts
+import { HTTP_METHODS } from "@suaveplan/api-openapi/types";
+import type { Operation, PathItem } from "@suaveplan/api-openapi/types";
+
+function eachOp(item: PathItem, fn: (m: string, op: Operation) => void): void {
+    for (const m of HTTP_METHODS) {
+        const op = item[m];
+        if (op) fn(m, op);
+    }
+}
+```
+
+## API Reference
+
+- `interface OpenAPIInfo` — title, version, optional description / contact / license / x-extensions.
+- `interface OpenAPIServer` — url, description, variables, x-extensions.
+- `interface SecurityScheme` — name + type discriminator + scheme/bearerFormat/in/description.
+- `interface RegisteredRoute` — internal record: method, path, tags, operationId, pluginName, summary, description, deprecated, security.
+- `interface Operation` — OpenAPI operation, x-extension friendly.
+- `interface PathItem` — keyed by lowercase HTTP method.
+- `interface OpenAPIDocument` — info + servers + paths + components + tags + security.
+- `type HttpMethod` — `"get" | "post" | "put" | "patch" | "delete" | "options" | "head"`.
+- `const HTTP_METHODS` — readonly array of every literal.
+
+## Implementation Notes
+
+All fields except `info.title`, `info.version`, `openapi`, and `paths`
+are optional, matching the OpenAPI 3.1 schema. The merger and registry
+construct documents with `paths: {}` and grow them as routes register —
+never with `paths: undefined`.
+
+`Operation.responses` is typed as `Record<string, unknown>` rather than a
+structurally-typed response object because the actual response shapes
+are produced by `@hono/zod-openapi`'s `createRoute` and depend on the
+caller's Zod schemas. Tightening the type would require importing zod
+into the types module and would cascade compile-time dependencies. The
+merger only manipulates whole responses, never their internals, so the
+weaker shape is safe.
+
+`HTTP_METHODS` exists alongside the literal union because the merger
+and filter helpers need to iterate the methods at runtime. Keeping the
+two in this single module guarantees they cannot drift.

packages/api-stack/api/api-openapi/src/types/openapi.ts

@@ -0,0 +1,147 @@
+/**
+ * Structural types for OpenAPI 3.1 documents and registry inputs.
+ *
+ * Mirrors the subset of the spec the package emits and merges.
+ * Vendor extensions are typed as `x-${string}` index signatures so
+ * arbitrary `x-` keys are accepted without weakening the rest of the
+ * shape.
+ */
+
+/**
+ * OpenAPI `info` object — title and version are required by the spec.
+ */
+export interface OpenAPIInfo {
+    title: string;
+    version: string;
+    description?: string;
+    termsOfService?: string;
+    contact?: {
+        name?: string;
+        url?: string;
+        email?: string;
+    };
+    license?: {
+        name: string;
+        url?: string;
+    };
+    [key: `x-${string}`]: unknown;
+}
+
+/**
+ * OpenAPI `server` object.
+ */
+export interface OpenAPIServer {
+    url: string;
+    description?: string;
+    variables?: Record<
+        string,
+        {
+            default: string;
+            enum?: string[];
+            description?: string;
+        }
+    >;
+    [key: `x-${string}`]: unknown;
+}
+
+/**
+ * Security scheme definition — covers HTTP, API key, OAuth2, OIDC.
+ */
+export interface SecurityScheme {
+    name: string;
+    type: "http" | "apiKey" | "oauth2" | "openIdConnect";
+    scheme?: "bearer" | "basic";
+    bearerFormat?: string;
+    in?: "header" | "query" | "cookie";
+    description?: string;
+}
+
+/**
+ * Recorded route metadata — emitted by registry transforms and used
+ * to derive `paths` entries in {@link OpenAPIDocument}.
+ */
+export interface RegisteredRoute {
+    method: string;
+    path: string;
+    tags: string[];
+    operationId?: string;
+    pluginName?: string;
+    summary?: string;
+    description?: string;
+    deprecated?: boolean;
+    security?: Array<Record<string, string[]>>;
+}
+
+/**
+ * OpenAPI operation — the GET/POST/PUT/PATCH/DELETE/HEAD/OPTIONS entries
+ * inside a `PathItem`.
+ */
+export interface Operation {
+    operationId?: string;
+    summary?: string;
+    description?: string;
+    tags?: string[];
+    parameters?: unknown[];
+    requestBody?: unknown;
+    responses: Record<string, unknown>;
+    security?: Array<Record<string, string[]>>;
+    deprecated?: boolean;
+    [key: `x-${string}`]: unknown;
+}
+
+/**
+ * OpenAPI path item — keyed by HTTP method.
+ */
+export interface PathItem {
+    get?: Operation;
+    post?: Operation;
+    put?: Operation;
+    patch?: Operation;
+    delete?: Operation;
+    options?: Operation;
+    head?: Operation;
+}
+
+/**
+ * OpenAPI 3.1 document shape consumed by the merger and emitted by
+ * `OpenAPIRegistry.buildDocument()`.
+ */
+export interface OpenAPIDocument {
+    openapi: string;
+    info: OpenAPIInfo;
+    servers?: OpenAPIServer[];
+    paths: Record<string, PathItem>;
+    components?: {
+        schemas?: Record<string, unknown>;
+        securitySchemes?: Record<string, unknown>;
+        parameters?: Record<string, unknown>;
+        responses?: Record<string, unknown>;
+    };
+    tags?: Array<{
+        name: string;
+        description?: string;
+    }>;
+    security?: Array<Record<string, string[]>>;
+}
+
+/**
+ * HTTP method literal accepted by {@link Operation}.
+ */
+export type HttpMethod =
+    | "get"
+    | "post"
+    | "put"
+    | "patch"
+    | "delete"
+    | "options"
+    | "head";
+
+export const HTTP_METHODS: readonly HttpMethod[] = [
+    "get",
+    "post",
+    "put",
+    "patch",
+    "delete",
+    "options",
+    "head",
+] as const;