Add Slack Socket Mode support by haydenbleasel · Pull Request #162 · vercel/chat

haydenbleasel · 2026-03-02T23:53:43Z

Summary

Adds serverless-compatible Socket Mode forwarding to the Slack adapter, mirroring the Discord gateway pattern
A cron-invoked listener maintains the WebSocket, acks events, and forwards them via HTTP POST to the existing webhook endpoint using an x-slack-socket-token header
The adapter stays in mode: "webhook" (default) — socket mode listener is a separate external concern
routeSocketEvent() now accepts WebhookOptions and uses waitUntil for async handlers
New startSocketModeListener() / runSocketModeListener() / forwardSocketEvent() methods
Example cron route at /api/slack/socket-mode with createPersistentListener for Redis-based cross-instance coordination
Cron runs every 9 min, listener duration 10 min (same as Discord)

Test plan

Closes #123

vercel · 2026-03-02T23:53:49Z

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Project	Deployment	Actions	Updated (UTC)
chat	Ready	Preview, Comment, Open in v0	Apr 20, 2026 3:08pm
chat-sdk-nextjs-chat	Ready	Preview, Comment, Open in v0	Apr 20, 2026 3:08pm

socket-security · 2026-03-02T23:54:26Z

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/@slack/socket-mode@2.0.6

View full report

…nteractive payloads can cause unhandled promise rejections that crash the Node.js process. This commit fixes the issue reported at packages/adapter-slack/src/index.ts:1152 **Bug Analysis:** In `routeSocketEvent` (line 1150), which is a synchronous `void` method, two async operations produce floating promises: 1. `this.handleSlashCommand(params)` (line 1165) - `handleSlashCommand` is `async` and always returns a `Promise<Response>`. It calls `await this.lookupUser(userId)` which internally calls `await this.chat.getState().get()` (before the try/catch around the API call), and `this.chat.processSlashCommand()`. Any of these could throw. 2. `this.dispatchInteractivePayload(payload)` (line 1172) - Returns `Response | Promise<Response>`. When the payload type is `view_submission`, it delegates to `async handleViewSubmission()`, which calls `await this.chat.processModalSubmit()` and accesses `payload.view.state.values` (which could throw on malformed payloads). Since `routeSocketEvent` is synchronous (`void` return type) and called from a sync context within the socket mode event handler (after `await ack()` has already completed), these returned promises are fire-and-forget. If any reject, it triggers an unhandled promise rejection, which in Node.js 15+ terminates the process by default. In contrast, in the webhook code path (`handleWebhook`), these same methods are always `return`-ed from async functions, so their promises are properly chained to the caller. **Fix:** Added `.catch()` handlers to both floating promises: 1. For `handleSlashCommand`: Added `.catch()` that logs the error via `this.logger.error`. 2. For `dispatchInteractivePayload`: Since it returns `Response | Promise<Response>` (only a Promise for `view_submission`), used `instanceof Promise` to conditionally attach a `.catch()` handler only when the result is a Promise. This approach was chosen over making `routeSocketEvent` async because: (a) it doesn't change the method signature, (b) the caller doesn't need to await it (the ack has already been sent), and (c) errors are logged rather than silently swallowed. Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com> Co-authored-by: haydenbleasel <hello@haydenbleasel.com>

- Export SlackForwardedSocketEvent type - Add x-slack-socket-token check at top of handleWebhook() for forwarded events - Update routeSocketEvent() to accept WebhookOptions and use waitUntil - Add startSocketModeListener(), runSocketModeListener(), forwardSocketEvent() Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Forwarded event accepted/rejected based on appToken - Bypasses signature verification for forwarded events - Options passthrough to handlers - startSocketModeListener returns 200/500 appropriately Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- New /api/slack/socket-mode route using createPersistentListener - Mirrors Discord gateway pattern (CRON_SECRET auth, Redis coordination) - Cron runs every 9 min, listener duration 10 min Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Make signingSecret optional (string | undefined) instead of falling back to "". verifySignature now returns false when no secret is configured, preventing HMAC with an empty key from silently passing. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Sync errors from processEventPayload were silently dropped in socket mode. Wrap with try-catch for parity with slash_commands and interactive cases. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dancer · 2026-04-17T13:26:18Z

@reaganmcf do me a favour try it again 🙏🏻

reaganmcf · 2026-04-17T13:46:58Z

@dancer trying now!

reaganmcf · 2026-04-17T16:09:39Z

@dancer this is awesome!

The only thing that doesn't work is that the onModalSubmit callback doesn't support { action: "clear"} so I can't get a multi step modal to actually fully close the modal stack. I can only do { action: "close"} , which in a modal view that is from a previous { action: "push"} , will result in just going one view down the stack.

This results in:

Modal Step 1, submit pushes step 2
Modal step 2, submit sends action: "close"
back to Modal Step 1

Supporting the clear action should fix this. Everything else looks great and seems ready to ship 🔥

dancer · 2026-04-17T18:10:51Z

sweet sounds good will fix / look into that shortly and get this merged over the weekend / monday thanks for the help @reaganmcf

doneumark · 2026-04-19T19:59:53Z

+1

…-support # Conflicts: # packages/adapter-slack/src/index.test.ts

dancer · 2026-04-20T10:43:32Z

@reaganmcf sorry for the delay can i get you to do another quick test pushed some more changes in 925f8cf let me know & thanks a bunch for the feedback

dancer · 2026-04-20T10:44:58Z

after you test again i can get this merged today cc: @bensabic

reaganmcf · 2026-04-20T13:28:41Z

@dancer nested slack modals work! Works great - would love to get this merged

dancer · 2026-04-20T15:09:22Z

SGTM let's ship it

haydenbleasel linked an issue Mar 2, 2026 that may be closed by this pull request

Slack Socket Mode Support #123

Closed

1 task

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haydenbleasel requested a review from cramforce March 2, 2026 23:54

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Comment thread packages/adapter-slack/src/index.ts Outdated

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haydenbleasel marked this pull request as draft March 3, 2026 00:29

vercel bot deployed to Preview – chat-sdk-nextjs-chat March 3, 2026 00:52 View deployment

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haydenbleasel requested review from NicolasMontone and removed request for cramforce March 4, 2026 19:43

haydenbleasel and others added 14 commits March 16, 2026 13:20

Add slack/socket mode dependency

38091a5

Update config types and SlackAdapter class

e2887af

Add socket mode methods, extract interactive dispatch

ee31b62

Update createSlackAdapter factory function

ebec0d6

Write tests for socket mode

349eef8

Create slack-socket-mode.md

e64e36c

Run fix

816f971

Fix polynomial regex issues

4795773

Wrap event_callback in try-catch in routeSocketEvent

62f83b5

Sync errors from processEventPayload were silently dropped in socket mode. Wrap with try-catch for parity with slash_commands and interactive cases. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fix(slack): use SDK envelope type for socket mode event routing

a99ccec

vercel bot deployed to Preview – chat-sdk-nextjs-chat April 17, 2026 13:11 View deployment

vercel bot deployed to Preview – chat April 17, 2026 13:11 View deployment

chore: resolve merge conflicts with main

90beaa9

vercel bot deployed to Preview – chat-sdk-nextjs-chat April 17, 2026 13:12 View deployment

vercel bot deployed to Preview – chat April 17, 2026 13:13 View deployment

fix(slack): pass interactive response through ack in socket mode

2bcd64b

vercel bot deployed to Preview – chat-sdk-nextjs-chat April 17, 2026 13:17 View deployment

vercel bot deployed to Preview – chat April 17, 2026 13:18 View deployment

dancer added 2 commits April 20, 2026 11:38

feat(chat): add clear modal response action to close entire view stack

925f8cf

Merge remote-tracking branch 'origin/main' into 123-slack-socket-mode…

9e823f7

…-support # Conflicts: # packages/adapter-slack/src/index.test.ts

vercel bot deployed to Preview – chat April 20, 2026 10:42 View deployment

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dancer closed this Apr 20, 2026

dancer reopened this Apr 20, 2026

bensabic approved these changes Apr 20, 2026

View reviewed changes

chore: update changeset for clear modal action

238014a

vercel bot deployed to Preview – chat April 20, 2026 15:06 View deployment

vercel bot deployed to Preview – chat-sdk-nextjs-chat April 20, 2026 15:07 View deployment

dancer merged commit 7e90d9c into main Apr 20, 2026
11 checks passed

dancer deleted the 123-slack-socket-mode-support branch April 20, 2026 15:09

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Add Slack Socket Mode support#162

Add Slack Socket Mode support#162
dancer merged 25 commits intomainfrom
123-slack-socket-mode-support

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