feat: accept chunks as arguments to chat.{start,append,stop}Stream methods #2467

srtaalej · 2026-01-11T21:52:56Z

Summary

This PR introduces the chunks argument to the following methods:

chat.startStream
chat.appendStream
chat.stopStream

⚠️ This feature is experimental at the moment!

Code Snippet

const stream = new ChatStreamer(client, client.logger, {
      channel: CHANNEL_ID,
      thread_ts: threadTs,
      recipient_team_id: 'T09EX3FS2J3',
      recipient_user_id: 'U09G4FG3TRN',
    }, { buffer_size: 1 });

    await stream.append({
      chunks: [
        {
          type: 'markdown_text',
          text: '**Hello!** I am starting to process your request...\n\n'
        }]
    });
   
    await stream.append({
      chunks: [
        {
          type: 'plan_update',
          title: ''\nProcessing tasks...\n,
        },
        {
          type: 'task_update',
          id: 'task-1',
          title: 'Fetching data from API',
          status: 'complete',
          output: 'Successfully retrieved 42 records',
        },
        {
          type: 'task_update',
          id: 'task-2',
          title: 'Processing results',
          status: 'pending',
        },
      ],
    });
    
    await stream.append({
      chunks: [
        {
          type: 'task_update',
          id: 'task-2',
          title: 'Processing results',
          status: 'complete',
          output: 'Analysis complete!',
          sources: [
            {
              type: 'url',
              url: 'https://example.com/docs',
              text: 'Documentation',
            },
            {
              type: 'url',
              url: 'https://example.com/api',
              text: 'API Reference',
              icon_url: 'https://example.com/favicon.ico',
            },
          ],
        },
      ],
    });
   
     await stream.append({
      chunks: [
        {
          type: 'markdown_text',
          text: 'Hi Ale!\n\n',
        },
        {
          type: 'markdown_text',
          text: 'Here is what I found:\n\n',
        },
        {
          type: 'markdown_text',
          text: '- Item 1: *Important information*\n',
        },
        {
          type: 'markdown_text',
          text: '- Item 2: `Some code snippet`\n',
        },
      ],
    });

   
    await stream.stop({
      chunks: [
        {
          type: 'markdown_text',
          text: '\n\n---\n\n✅ **All tasks completed successfully!**\n',
        },
        {
          type: 'markdown_text',
          text: 'Thank you for using the streaming API with chunks.',
        },
      ],
    });

Requirements (place an `x` in each `[ ]`)

I've read and understood the Contributing Guidelines and have done my best effort to follow them.
I've read and agree to the Code of Conduct.

codecov · 2026-01-11T21:53:44Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.09%. Comparing base (b44cee1) to head (81140cc).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                     Coverage Diff                      @@
##           feat-ai-apps-thinking-steps    #2467   +/-   ##
============================================================
  Coverage                        93.09%   93.09%           
============================================================
  Files                               40       40           
  Lines                            11240    11240           
  Branches                           713      713           
============================================================
  Hits                             10464    10464           
  Misses                             764      764           
  Partials                            12       12

Flag	Coverage Δ
cli-hooks	`95.23% <ø> (ø)`
cli-test	`94.79% <ø> (ø)`
webhook	`96.66% <ø> (ø)`

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…thods

zimeg

@srtaalej Woooo! This'll be nice to land soon but I'm leaving a few comments on changes perhaps to make beforehand.

The tests are most confusing to me since I think all changes are contained in this PR... Am looking into this separate but do let me know if questions on these comments appear please!

zimeg · 2026-01-21T17:44:24Z

packages/types/src/index.ts

 export * from './block-kit/composition-objects';
 export * from './block-kit/extensions';
 export * from './calls';
+export * from './chunk';


🧪 note: Right now I notice CI is failing for a missing export... Am curious if this is specific to our testing workflows or this PR, but will explore this adjacent!

zimeg · 2026-01-21T17:45:07Z

packages/types/src/chunk.ts

+  const chunkObj = chunk as Record<string, unknown>;
+
+  if (!('type' in chunkObj) || typeof chunkObj.type !== 'string') {
+    console.warn('Unknown chunk detected and skipped (missing type)', chunk);


🪵 issue: We should prefer the @slack/logger package for these outputs!

zimeg · 2026-01-21T17:46:00Z

packages/types/src/chunk.ts

+  if(type === 'plan_update') {
+    if (typeof chunkObj.title === 'string') {
+      return chunkObj as unknown as PlanUpdateChunk;
+    }
+    console.warn('Invalid PlanUpdateChunk (missing title property)', chunk);
+    return null;
+  }


⚠️ suggestion: It might be preferable to let the API return an error for invalid chunks since these limitations might change in the future?

zimeg · 2026-01-21T17:47:50Z

packages/types/src/chunk.ts

+      typeof taskChunk.status === 'string' &&
+      ['pending', 'in_progress', 'complete', 'error'].includes(taskChunk.status)
+    ) {
+      return chunkObj as unknown as TaskUpdateChunk;


👾 thought: Morphing to unknown then a type might have an alternative with type "narrowing"! IIRC @WilliamBergamin is most familiar with that approach and has shared these docs with me at a point:

📚 https://www.typescriptlang.org/docs/handbook/2/narrowing.html#the-in-operator-narrowing

zimeg · 2026-01-21T17:48:21Z

packages/web-api/test/types/methods/chat.test-d.ts

+  {
+    channel: 'C1234',
+    ts: '1234.56',
+    markdown_text: 'hello',


Suggested change

markdown_text: 'hello',

🪓 issue: Let's remove this to match expected API behavior!

zimeg · 2026-01-21T17:49:26Z

packages/web-api/test/types/methods/chat.test-d.ts

+    chunks: [
+      {
+        type: 'markdown_text',
+        text: 'Hello world',
+      },
+      {
+        type: 'plan_update',
+        title: 'Analyzing request',
+      },
+      {
+        type: 'task_update',
+        id: 'task-1',
+        title: 'Processing request',
+        status: 'in_progress',
+        details: 'Working on it...',
+      },
+    ],


Suggested change

chunks: [

{

type: 'markdown_text',

text: 'Hello world',

},

{

type: 'plan_update',

title: 'Analyzing request',

},

{

type: 'task_update',

id: 'task-1',

title: 'Processing request',

status: 'in_progress',

details: 'Working on it...',

},

],

🪓 issue: Similar to the above, I'm not sure if we should error in typescript if both "markdown_text" and "chunks" are provided, but let's not showcase that here IMHO

zimeg · 2026-01-21T18:07:33Z

packages/types/src/chunk.ts

+    return null;
+  }
+
+  if(type === 'plan_update') {


Suggested change

if(type === 'plan_update') {

if (type === 'plan_update') {

👁️‍🗨️ issue: This is causing the linter to error and packages to not build as expected!

src/chunk.ts format ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ × Formatter would have printed the following content: 82 │ ··if·(type·===·'plan_update')·{ Checked 48 files in 26ms. No fixes applied. │ + Found 1 error. check ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

🔗 https://github.com/slackapi/node-slack-sdk/actions/runs/21079717525/job/60630237979#step:9:13

feat: accept chunks as arguments to chat.{start,append,stop}Stream me…

e3d7b9b

…thods

srtaalej force-pushed the ale-chunks branch from 225f47f to e3d7b9b Compare January 11, 2026 21:57

srtaalej self-assigned this Jan 11, 2026

srtaalej added the enhancement M-T: A feature request for new functionality label Jan 11, 2026

build: update slack/types version in package json

2601199

srtaalej changed the base branch from main to feat-ai-apps-thinking-steps January 12, 2026 19:51

srtaalej marked this pull request as ready for review January 15, 2026 22:48

srtaalej requested review from a team as code owners January 15, 2026 22:48

fix: make markdown text optional and add missing chunk type

160cfb7

srtaalej force-pushed the ale-chunks branch from 749493a to 160cfb7 Compare January 16, 2026 16:52

tests: add missing chunk type to tests

81140cc

srtaalej added the semver:minor label Jan 20, 2026

srtaalej requested a review from lukegalbraithrussell January 20, 2026 18:56

srtaalej assigned misscoded and unassigned misscoded Jan 20, 2026

srtaalej requested a review from misscoded January 20, 2026 18:57

zimeg reviewed Jan 21, 2026

View reviewed changes

zimeg added pkg:web-api applies to `@slack/web-api` pkg:types applies to `@slack/types` labels Jan 21, 2026

zimeg reviewed Jan 21, 2026

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feat: accept chunks as arguments to chat.{start,append,stop}Stream methods #2467

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