feat: accept chunks as arguments to chat stream helper #2470

srtaalej · 2026-01-16T19:54:11Z

Summary

This PR enables chunks processing in the chat stream helper

    const streamer = new ChatStreamer(client, client.logger, {
      channel: CHANNEL_ID,
      thread_ts: threadTs,
      recipient_team_id: 'TEAM_ID,
      recipient_user_id: 'USER_ID',
    }, { buffer_size: 1 });

    await streamer.append({
      chunks: [
        {
          type: 'markdown_text',
          text: '**Hello!** I am starting to process your request...\n\n'
        }]
    });

    await streamer.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.

…thods

codecov · 2026-01-16T19:55:13Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (feat-ai-apps-thinking-steps@e410413). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                      Coverage Diff                       @@
##             feat-ai-apps-thinking-steps    #2470   +/-   ##
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mwbrooks

🙌🏻 Exciting, thanks for opening this PR @srtaalej!

It looks like you've also added the new task_update check along with the plan_update 😄

🧪 @zimeg and I will take a look at the PR soon. In the meantime, it looks like there are some failed tests that will need to be resolved.

zimeg · 2026-01-23T21:50:37Z

packages/web-api/src/chat-stream.ts

  private async flushBuffer(
    args: Omit<ChatStartStreamArguments | ChatAppendStreamArguments, 'channel' | 'ts'>,
  ): Promise<ChatStartStreamResponse | ChatAppendStreamResponse> {
+    const finalArgs = this.buffer.length > 0 && !args.chunks ? { ...args, markdown_text: this.buffer } : args;


👀 note: We might want to add existing buffer to a new chunk with just markdown text, if the buffer has anything, then add the chunks argument. This would help make sure we're not appending while text is in the buffer!

This reverts commit dbca9c9.

mwbrooks

Thanks for updating this PR @srtaalej!

🧪 I noticed that the tests were failing when I linked the dev @slack/types package. Commit fc5ed1a fixes the tests and I've made a few notes around what changes were required.

I'll start to look into manual testing next! 👌🏻

mwbrooks · 2026-01-24T01:26:26Z

packages/web-api/src/chat-stream.ts

-    if (this.buffer.length >= this.options.buffer_size) {
+    if (args?.markdown_text) {
+      this.buffer += args.markdown_text;
+      args.markdown_text = undefined;


note: I pushed commit fc5ed1a to unset the args.markdown_text after adding it to the buffer.

If this is not done, then the markdown_text will be added to the API request, which is also included in the chunks: [{ type: "markdown_text", "text": "...." }].

@zimeg Does this look correct to you? I noticed this wasn't explicitly done in the Python SDK.

@mwbrooks A change similar to other comments might be useful to destructure markdown_text and chunks from the rest of args before a chance to flush the buffer?

const { markdown_text, chunks, ...opts } = args;

IIRC the arguments alongside **kwargs in the Python implementation do this without added lines!

mwbrooks · 2026-01-24T01:27:37Z

packages/web-api/src/chat-stream.ts

      channel: this.streamArgs.channel,
      ts: this.streamTs,
+      chunks: flushings,
      ...args,


note: I made commit fc5ed1a which added back ..args,. If we don't have this, then we may drop additional args like token. This also has the side effect of adding markdown_text as an arg, which is why we now must unset it. .cc @zimeg

@mwbrooks Thanks so much for catching this! We might want to consider a "destructured" approach to separate markdown_text and also chunks from the remaining options:

const { markdown_text, chunks, ...opts } = args;

This might help us avoid overriding new chunks with ...args as well, or chunks can be a following parameter?

mwbrooks · 2026-01-24T01:28:17Z

packages/web-api/src/WebClient.spec.ts

+        .post('/api/chat.stopStream', {
+          channel: 'C0123456789',
+          ts: '123.123',
+          chunks: JSON.stringify([{ type: 'markdown_text', text: 'nice!' }]),


note: I made commit fc5ed1a which updates this test to support chunks instead of markdown_text because the streaming helper will now convert all markdown text into a chunk.

zimeg

📝 A quick note on separating markdown_text and chunks from extra options since we might be adding from the buffer to chunks before making an API call!

👁️‍🗨️ Appreciate these catches different from python nuance @mwbrooks!

zimeg · 2026-01-24T05:51:39Z

packages/web-api/src/chat-stream.ts

      channel: this.streamArgs.channel,
      ts: this.streamTs,
+      chunks: flushings,
      ...args,


@mwbrooks Thanks so much for catching this! We might want to consider a "destructured" approach to separate markdown_text and also chunks from the remaining options:

const { markdown_text, chunks, ...opts } = args;

This might help us avoid overriding new chunks with ...args as well, or chunks can be a following parameter?

zimeg · 2026-01-24T06:01:24Z

packages/web-api/src/chat-stream.ts

-    if (this.buffer.length >= this.options.buffer_size) {
+    if (args?.markdown_text) {
+      this.buffer += args.markdown_text;
+      args.markdown_text = undefined;


@mwbrooks A change similar to other comments might be useful to destructure markdown_text and chunks from the rest of args before a chance to flush the buffer?

const { markdown_text, chunks, ...opts } = args;

IIRC the arguments alongside **kwargs in the Python implementation do this without added lines!

zimeg

@srtaalej LGTM! Thanks for bringing chunks to the streamer! I left a quibble on internals but testing works well for me 🤓

zimeg · 2026-01-26T21:19:23Z

packages/web-api/src/chat-stream.ts

      this.state = 'in_progress';
    }
+
+    const flushings: AnyChunk[] = [];


🙊 quibble: This variable was changed alike to "chunks to flush" in updates to the Python SDK that we might mirror here? Also unrelated but empty lines might be nice to remove before merging-

mwbrooks

🧪 Manually testing with a modified sample app works well for chunks as markdown_text, task_update, and plan_update. 🎉 👏🏻

Co-authored-by: Michael Brooks <[email protected]> Co-authored-by: Eden Zimbelman <[email protected]>

srtaalej added 3 commits January 11, 2026 16:56

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

e3d7b9b

…thods

build: update slack/types version in package json

2601199

fix: make markdown text optional and add missing chunk type

160cfb7

srtaalej self-assigned this Jan 16, 2026

tests: add missing chunk type to tests

81140cc

srtaalej marked this pull request as ready for review January 20, 2026 17:04

srtaalej requested a review from a team as a code owner January 20, 2026 17:04

srtaalej added the enhancement M-T: A feature request for new functionality label Jan 20, 2026

mwbrooks added the semver:minor label Jan 20, 2026

mwbrooks reviewed Jan 20, 2026

View reviewed changes

srtaalej added semver:minor and removed semver:minor labels Jan 20, 2026

srtaalej requested review from lukegalbraithrussell, misscoded and zimeg January 20, 2026 18:56

srtaalej added 6 commits January 22, 2026 13:27

build: use @slack/logger for debugging parsechunks

dbca9c9

type narrowing for parseChunks

1d480f6

feat: chunk processing in chat stream helper

14c9f36

fix: buffer logic for chunks and markdown

35cceed

bug: handle undefined args in ChatStream append

6f5f8f1

linter errors

5e86b29

srtaalej force-pushed the ale-chunks-stream-helper branch 2 times, most recently from e797040 to 5e86b29 Compare January 23, 2026 21:42

zimeg reviewed Jan 23, 2026

View reviewed changes

srtaalej and others added 4 commits January 23, 2026 16:51

Merge branch 'feat-ai-apps-thinking-steps' into ale-chunks-stream-helper

425b897

Revert "build: use @slack/logger for debugging parsechunks"

076d3a5

This reverts commit dbca9c9.

fix: flush logic for chunks

0e553a7

test: update charStream tests to support chunks

fc5ed1a

mwbrooks reviewed Jan 24, 2026

View reviewed changes

zimeg added the pkg:web-api applies to `@slack/web-api` label Jan 24, 2026

zimeg reviewed Jan 24, 2026

View reviewed changes

srtaalej added 4 commits January 26, 2026 11:59

fix: args destructure

9d6438e

update package.json

c5b07ac

testing oauth & socket-mode links to web-api

b076258

undo package json changes

44aa882

zimeg approved these changes Jan 26, 2026

View reviewed changes

mwbrooks approved these changes Jan 26, 2026

View reviewed changes

change flushings to chunksToFlush

032ad03

srtaalej merged commit 8d237be into feat-ai-apps-thinking-steps Jan 26, 2026
72 of 111 checks passed

srtaalej deleted the ale-chunks-stream-helper branch January 26, 2026 21:54

zimeg added a commit that referenced this pull request Jan 29, 2026

feat: accept chunks as arguments to chat stream helper (#2470)

3011034

Co-authored-by: Michael Brooks <[email protected]> Co-authored-by: Eden Zimbelman <[email protected]>

zimeg mentioned this pull request Feb 10, 2026

docs: add thinking steps release notes #2510

Merged

2 tasks

github-actions bot mentioned this pull request Feb 10, 2026

chore: release #2509

Merged

feat: accept chunks as arguments to chat stream helper #2470

feat: accept chunks as arguments to chat stream helper #2470

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srtaalej commented Jan 16, 2026

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