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

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Merged
srtaalej merged 19 commits into from
Jan 26, 2026
Merged

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

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e3d7b9b
feat: accept chunks as arguments to chat.{start,append,stop}Stream me…
srtaalej Jan 11, 2026
2601199
build: update slack/types version in package json
srtaalej Jan 11, 2026
160cfb7
fix: make markdown text optional and add missing chunk type
srtaalej Jan 15, 2026
81140cc
tests: add missing chunk type to tests
srtaalej Jan 16, 2026
dbca9c9
build: use @slack/logger for debugging parsechunks
srtaalej Jan 22, 2026
1d480f6
type narrowing for parseChunks
srtaalej Jan 22, 2026
14c9f36
feat: chunk processing in chat stream helper
srtaalej Jan 16, 2026
35cceed
fix: buffer logic for chunks and markdown
srtaalej Jan 20, 2026
6f5f8f1
bug: handle undefined args in ChatStream append
srtaalej Jan 21, 2026
5e86b29
linter errors
srtaalej Jan 22, 2026
425b897
Merge branch 'feat-ai-apps-thinking-steps' into ale-chunks-stream-helper
srtaalej Jan 23, 2026
076d3a5
Revert "build: use @slack/logger for debugging parsechunks"
mwbrooks Jan 23, 2026
0e553a7
fix: flush logic for chunks
srtaalej Jan 23, 2026
fc5ed1a
test: update charStream tests to support chunks
mwbrooks Jan 24, 2026
9d6438e
fix: args destructure
srtaalej Jan 26, 2026
c5b07ac
update package.json
srtaalej Jan 26, 2026
b076258
testing oauth & socket-mode links to web-api
srtaalej Jan 26, 2026
44aa882
undo package json changes
srtaalej Jan 26, 2026
032ad03
change flushings to chunksToFlush
srtaalej Jan 26, 2026
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18 changes: 13 additions & 5 deletions packages/web-api/src/WebClient.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1228,7 +1228,11 @@ describe('WebClient', () => {
ok: true,
ts: '123.123',
})
.post('/api/chat.stopStream', { channel: 'C0123456789', ts: '123.123', markdown_text: 'nice!' })
.post('/api/chat.stopStream', {
channel: 'C0123456789',
ts: '123.123',
chunks: JSON.stringify([{ type: 'markdown_text', text: 'nice!' }]),
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@mwbrooks mwbrooks Jan 24, 2026

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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.

})
.reply(200, {
ok: true,
});
Expand Down Expand Up @@ -1279,7 +1283,7 @@ describe('WebClient', () => {
const scope = nock('https://slack.com')
.post('/api/chat.startStream', {
channel: 'C0123456789',
markdown_text: '**this messag',
chunks: JSON.stringify([{ type: 'markdown_text', text: '**this messag' }]),
recipient_team_id: 'T0123456789',
recipient_user_id: 'U0123456789',
thread_ts: '123.000',
Expand All @@ -1290,7 +1294,7 @@ describe('WebClient', () => {
})
.post('/api/chat.appendStream', {
channel: 'C0123456789',
markdown_text: 'e is bold!',
chunks: JSON.stringify([{ type: 'markdown_text', text: 'e is bold!' }]),
token: 'xoxb-updated-1',
ts: '123.123',
})
Expand All @@ -1300,7 +1304,7 @@ describe('WebClient', () => {
.post('/api/chat.stopStream', {
blocks: JSON.stringify([contextActionsBlock]),
channel: 'C0123456789',
markdown_text: '**',
chunks: JSON.stringify([{ type: 'markdown_text', text: '**' }]),
token: 'xoxb-updated-2',
ts: '123.123',
})
Expand Down Expand Up @@ -1370,7 +1374,11 @@ describe('WebClient', () => {
ok: true,
ts: '123.123',
})
.post('/api/chat.stopStream', { channel: 'C0123456789', ts: '123.123', markdown_text: 'nice!' })
.post('/api/chat.stopStream', {
channel: 'C0123456789',
ts: '123.123',
chunks: JSON.stringify([{ type: 'markdown_text', text: 'nice!' }]),
})
.reply(200, {
ok: true,
});
Expand Down
40 changes: 35 additions & 5 deletions packages/web-api/src/chat-stream.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import type { Logger } from '@slack/logger';
import type { AnyChunk } from '@slack/types';
import type { ChatAppendStreamArguments, ChatStartStreamArguments, ChatStopStreamArguments } from './types/request';
import type { ChatAppendStreamResponse, ChatStartStreamResponse, ChatStopStreamResponse } from './types/response';
import type WebClient from './WebClient';
Expand Down Expand Up @@ -89,8 +90,11 @@ export class ChatStreamer {
if (args.token) {
this.token = args.token;
}
this.buffer += args.markdown_text;
if (this.buffer.length >= this.options.buffer_size) {
if (args?.markdown_text) {
this.buffer += args.markdown_text;
args.markdown_text = undefined;
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@mwbrooks mwbrooks Jan 24, 2026

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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.

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@zimeg zimeg Jan 24, 2026

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@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!

}
if (this.buffer.length >= this.options.buffer_size || args?.chunks) {
return await this.flushBuffer(args);
}
const details = {
Expand Down Expand Up @@ -132,6 +136,7 @@ export class ChatStreamer {
}
if (args?.markdown_text) {
this.buffer += args.markdown_text;
args.markdown_text = undefined;
}
if (!this.streamTs) {
const response = await this.client.chat.startStream({
Expand All @@ -144,12 +149,25 @@ export class ChatStreamer {
this.streamTs = response.ts;
this.state = 'in_progress';
}

const flushings: AnyChunk[] = [];
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@zimeg zimeg Jan 26, 2026

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🙊 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-


if (this.buffer.length > 0) {
flushings.push({
type: 'markdown_text',
text: this.buffer,
});
}
if (args?.chunks) {
flushings.push(...args.chunks);
}

const response = await this.client.chat.stopStream({
token: this.token,
channel: this.streamArgs.channel,
ts: this.streamTs,
chunks: flushings,
...args,
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@mwbrooks mwbrooks Jan 24, 2026

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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

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@zimeg zimeg Jan 24, 2026

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@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?

markdown_text: this.buffer,
});
this.state = 'completed';
return response;
Expand All @@ -158,12 +176,24 @@ export class ChatStreamer {
private async flushBuffer(
args: Omit<ChatStartStreamArguments | ChatAppendStreamArguments, 'channel' | 'ts'>,
): Promise<ChatStartStreamResponse | ChatAppendStreamResponse> {
const flushings: AnyChunk[] = [];

if (this.buffer.length > 0) {
flushings.push({
type: 'markdown_text',
text: this.buffer,
});
}
if (args?.chunks) {
flushings.push(...args.chunks);
}

if (!this.streamTs) {
const response = await this.client.chat.startStream({
...this.streamArgs,
token: this.token,
chunks: flushings,
...args,
markdown_text: this.buffer,
});
this.buffer = '';
this.streamTs = response.ts;
Expand All @@ -174,8 +204,8 @@ export class ChatStreamer {
token: this.token,
channel: this.streamArgs.channel,
ts: this.streamTs,
chunks: flushings,
...args,
markdown_text: this.buffer,
});
this.buffer = '';
return response;
Expand Down
18 changes: 17 additions & 1 deletion packages/web-api/test/types/methods/chat.test-d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -676,7 +676,23 @@ expectAssignable<Parameters<typeof web.chat.startStream>>([
{
channel: 'C1234',
thread_ts: '1234.56',
markdown_text: 'hello',
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...',
},
],
recipient_team_id: 'T1234',
recipient_user_id: 'U1234',
},
Expand Down
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