suaveplan/openspec/changes/enterprise-slack-client/proposal.md

# OpenSpec Change: enterprise-slack-client

- **Change ID**: enterprise-slack-client
- **Package**: `@suaveplan/slack-client`
- **Category**: universal
- **Target path**: `universal/social/slack-client`
- **Status**: IN PROGRESS
- **Date**: 2026-04-24
- **Reference spec**: `/mnt/s/web/suaveplan/enterprise/slack-client.md`

---

## Summary

Deliver `@suaveplan/slack-client` on the genesis branch from scratch at enterprise quality. The package provides a generic Slack API client: Web API method wrappers for messaging (`chat.postMessage`, `chat.update`, `chat.delete`), channel management (`conversations.*`), user info (`users.*`), file uploads, Block Kit message builder, Incoming Webhooks, Event subscription parsing with signature verification, slash-command payload parsing, interactive component payload handling, and a `SlackClient` facade. Injectable fetch and crypto; no Slack SDK dependency. Genesis adds structured errors, Zod schemas, OTel instrumentation, retry with circuit breaker, and `AbortSignal` cancellation.

---

## Current-state audit (genesis)

The package does not exist on genesis yet — this is a fresh build.

---

## Available workspace deps on genesis

| Package | Role |
|---|---|
| `@suaveplan/error` (`workspace:^`) | `SlackError`; `SLACK.*` error codes |
| `@suaveplan/types` (`workspace:^`) | `LoggerLike`, `Clock` |
| `@suaveplan/retry` (`workspace:^`) | Retry + circuit breaker for API calls |
| `@suaveplan/crypto` (`workspace:^`) | HMAC-SHA256 request signature verification |
| `zod` (`catalog:forms`) | Schema validation |
| `@opentelemetry/api` (`catalog:observability`) | Spans + counters |

Dev deps: `vitest`, `@vitest/coverage-istanbul`, `fast-check` (all `catalog:testing`).

---

## Public API surface

### `SlackClient`

```ts
class SlackClient {
  constructor(options: SlackClientOptions)

  // Messaging
  postMessage(options: PostMessageOptions): Promise<SlackMessageResponse>
  updateMessage(options: UpdateMessageOptions): Promise<SlackMessageResponse>
  deleteMessage(channel: string, ts: string): Promise<void>

  // Channels
  listConversations(options?: ListConversationsOptions): AsyncGenerator<SlackChannel>
  getConversationInfo(channel: string): Promise<SlackChannel>

  // Users
  getUserInfo(userId: string): Promise<SlackUser>
  getUserByEmail(email: string): Promise<SlackUser>

  // Files
  uploadFile(options: FileUploadOptions): Promise<SlackFile>

  // Webhooks
  postToWebhook(url: string, payload: WebhookPayload): Promise<void>
}

interface SlackClientOptions {
  token: string
  signingSecret?: string   // for event verification
  retryOptions?: RetryOptions
  fetch?: typeof globalThis.fetch
  clock?: Clock
  logger?: LoggerLike
}
```

### Block Kit builder

```ts
function createMessage(text: string): MessageBuilder
interface MessageBuilder {
  section(text: string): MessageBuilder
  divider(): MessageBuilder
  image(url: string, altText: string): MessageBuilder
  actions(...elements: ActionElement[]): MessageBuilder
  context(...elements: ContextElement[]): MessageBuilder
  build(): SlackBlocks
}
```

### Event handling

```ts
function verifySlackSignature(
  body: string,
  timestamp: string,
  signature: string,
  signingSecret: string,
  options?: { maxAgeSeconds?: number; clock?: Clock }
): boolean

function parseSlackEvent(body: unknown): SlackEvent
function parseSlashCommand(body: unknown): SlashCommand
function parseInteractivePayload(body: unknown): InteractivePayload
```

### Error codes

```ts
type SlackErrorCode =
  | 'SLACK_AUTH_FAILED'
  | 'SLACK_API_ERROR'
  | 'SLACK_RATE_LIMITED'
  | 'SLACK_SIGNATURE_INVALID'
  | 'SLACK_CHANNEL_NOT_FOUND'
  | 'SLACK_USER_NOT_FOUND'
  | 'SLACK_ABORTED'
```

---

## Genesis additions

1. **`SlackError`** extends `SuaveplanError` with seven stable codes.
2. **Zod schemas** for `PostMessageOptions`, `SlackEvent`, `SlashCommand`, `InteractivePayload`, `SlackChannel`, `SlackUser`, `SlackFile`.
3. **Rate-limit handling** — respects `Retry-After` header from Slack 429 responses; integrates with `@suaveplan/retry`.
4. **Circuit breaker** — wraps all API calls via `@suaveplan/retry` circuit breaker; opens after 5 consecutive failures.
5. **OTel instrumentation** — span `slack.api_call` with attribute `slack.method`; counter `slack.api_total`; histogram `slack.api_duration_ms`.
6. **Property-based tests** — Block Kit builder produces valid JSON structures for arbitrary sequences of builder calls.

---

## File layout

```text
universal/social/slack-client/
  package.json
  tsconfig.json
  vitest.config.ts
  src/
    index.ts
    error-codes.ts
    constants/
      index.ts
    types/
      common.ts
      common.md
    core/
      slack-client/
        slack-client.ts
        slack-client.md
        slack-client.types.ts
        slack-client.test.ts
        index.ts
      api-caller/
        api-caller.ts
        api-caller.md
        api-caller.test.ts
        index.ts
    blocks/
      message-builder/
        message-builder.ts
        message-builder.md
        message-builder.test.ts
        index.ts
    events/
      event-parser/
        event-parser.ts
        event-parser.md
        event-parser.test.ts
        index.ts
      signature-verifier/
        signature-verifier.ts
        signature-verifier.md
        signature-verifier.test.ts
        index.ts
    __benchmarks__/
      slack-client.bench.ts
  tests/
    integration.test.ts
    property.test.ts
```

---

## Impact

**Downstream consumers**: `@suaveplan/message-bridge`, `@suaveplan/notification-channel`.

**Workspace dep prerequisites**: `@suaveplan/error`, `@suaveplan/types`, `@suaveplan/retry`, `@suaveplan/crypto`.