feat(web-api): add a chat stream method to the web client #2379

zimeg · 2025-09-24T03:25:35Z

Summary

This PR adds a WebClient#chatStream method that creates chat streams 🤖

Preview

const streamer = client.chatStream({
  channel: "C0123456789",
  thread_ts: "1700000001.123456",
  recipient_team_id: "T0123456789",
  recipient_user_id: "U0123456789",
  buffer_size: 500,
});
await streamer.append({
  markdown_text: "**hello wo",
});
await streamer.append({
  markdown_text: "rld!**",
});
await streamer.stop();

Testing

WIP-

Notes

Will save documentation generation for a later commit since the diff is significant at the moment I find.
A default text buffer is used to avoid reaching rate limits in frequent updates.
Super open to thoughts on the approach and implementation - does this seem like an alright change?
Planning to follow up with tests after discussion to avoid extra changes too 👾

Requirements

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 · 2025-09-24T03:26:15Z

Codecov Report

❌ Patch coverage is 99.18256% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (ai-apps@520a2d6). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             ai-apps    #2379   +/-   ##
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==========================================
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  Partials           ?       12

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cli-hooks	`95.23% <ø> (?)`
cli-test	`94.80% <ø> (?)`
oauth	`77.39% <ø> (?)`
socket-mode	`61.87% <ø> (?)`
web-api	`98.06% <99.18%> (?)`
webhook	`96.66% <ø> (?)`

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packages/web-api/src/WebClient.ts

mcodik · 2025-09-24T17:53:22Z

packages/web-api/src/WebClient.ts

+   */
+  public async stream(params: ChatStartStreamArguments): Promise<ChatStreamer> {
+    const streamer = new ChatStreamer(this);
+    await streamer.start(params);


startStream turns off the loading animation, we should defer it until we have the first bytes to stream.

@mcodik Great callout! The changes of 826e46c address this but also make the ChatStreamer class more opinionated to no longer expose a "start" method.

Instead we expose "append" and "stop" with the actual "chat.startStream" method being called when sending the first of the markdown text!

I find this alright to use in development but am open to adjustments however needed 🤖

mcodik · 2025-09-24T17:54:17Z

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

+    if (!this.streamTs) {
+      throw new Error('failed to append stream: ts not found');
+    }
+    const response = await this.client.chat.appendStream({


plz buffer some characters here, plus some ways for developers to tune the buffer size

@mcodik The WebClient#chatStream method now configures this with changes of 826e46c:

const streamer = client.chatStream({ channel: "C0123456789", thread_ts: "1700000001.123456", recipient_team_id: "T0123456789", recipient_user_id: "U0123456789", buffer_size: 500, // This defaults to "250" characters at the moment });

Co-authored-by: Michael Brooks <[email protected]> Co-authored-by: Maurice Codik <[email protected]>

mcodik

looks great thanks!

mwbrooks

Exciting work @zimeg! I've left a few comments and I'll take it for a spin now 🧪

mwbrooks · 2025-09-30T02:59:23Z

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

+   * @example
+   * const client = new WebClient(process.env.SLACK_BOT_TOKEN);
+   * const logger = new ConsoleLogger();
+   * const args = {
+   *   channel: "C0123456789",
+   *   thread_ts: "1700000001.123456",
+   *   recipient_team_id: "T0123456789",
+   *   recipient_user_id: "U0123456789",
+   * };
+   * const streamer = new ChatStreamer(client, logger, args, { buffer_size: 500 });
+   * await streamer.append({
+   *   markdown_text: "**hello world!**",
+   * });
+   * await streamer.stop();


praise: Love seeing the example for the generated docs!

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

mwbrooks · 2025-09-30T03:03:13Z

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

+   * @see {@link https://docs.slack.dev/reference/methods/chat.appendStream}
+   */
+  async append(
+    params: Omit<ChatAppendStreamArguments, 'channel' | 'ts'>,


praise: Nice touch that we're just passing in the appendSteam args.

❓ question: I noticed that the constructor calls it args while the append calls it params. Is there a reason?

@mwbrooks Thanks for calling this out! I agree that a more general typing is nice to have here! 👾

I noticed that the constructor calls it args while the append calls it params. Is there a reason?

A partial reason might be quick naming, but I've added fcbce94 and 0f852cd to be more consistent in how method arguments mapping to args and params including options 🙏 ✨

mwbrooks · 2025-09-30T03:10:33Z

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

+    if (!this.streamTs) {
+      const response = await this.client.chat.startStream({
+        ...this.args,
+        token: this.token,
+        ...params,
+        markdown_text: this.buffer,
+      });
+      this.buffer = '';
+      this.streamTs = response.ts;
+      this.state = 'in_progress';
+      return response;
+    }


question: Why did you choose to client.chat.startStream(...) in both the .stop(...) and .flushBuffer(...) instead of the constructor? Just curious.

@mwbrooks This skips an extra .appendStream method call if streamer.stop() is called on an existing stream I am hoping. We also avoid adding this to the constructor to delay this as an asynchronous process to favor loading states:

startStream turns off the loading animation, we should defer it until we have the first bytes to stream.

🔗 #2379 (comment)

mwbrooks

✅ Nice work @zimeg! Throwing an approval on here - you can work through my feedback and decide what to keep or not.

🧪 I've manually tested locally with a sample app and it works very well. I played with buffer sizes between 250-512 and didn't notice any major difference, so I think 250 (256?) is a good default!

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

zimeg added 2 commits September 23, 2025 20:19

feat(web-api): add a chat stream method to the web client

bea7c76

chore: lint

5926aa1

zimeg requested a review from mwbrooks September 24, 2025 03:25

zimeg self-assigned this Sep 24, 2025

zimeg added semver:minor enhancement M-T: A feature request for new functionality pkg:web-api applies to `@slack/web-api` labels Sep 24, 2025

mwbrooks reviewed Sep 24, 2025

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packages/web-api/src/WebClient.ts Outdated Show resolved Hide resolved

mcodik reviewed Sep 24, 2025

View reviewed changes

zimeg and others added 3 commits September 25, 2025 23:02

chore: merge w base branch

9554c08

refactor: change client.stream to client.chatStream

6a7e7ba

Co-authored-by: Michael Brooks <[email protected]> Co-authored-by: Maurice Codik <[email protected]>

feat: buffer text according to unsent character counts

826e46c

mcodik approved these changes Sep 29, 2025

View reviewed changes

zimeg added 2 commits September 29, 2025 16:57

test: confirm text is streamed as expected with the client

bab5b41

Merge branch 'ai-apps' into zimeg-feat-web-api-chat-streamer

d1acaad

zimeg marked this pull request as ready for review September 29, 2025 23:59

mwbrooks reviewed Sep 30, 2025

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mwbrooks approved these changes Sep 30, 2025

View reviewed changes

zimeg and others added 4 commits September 29, 2025 21:10

feat: use based two default for a buffer size 256 characters

771a6ef

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

docs: update jsdoc to current implementations

c320a80

refactor: rename internal stream arguments to streamArgs

fcbce94

refactor: rename method params to args argument

0f852cd

zimeg merged commit ffeb783 into ai-apps Sep 30, 2025
161 of 165 checks passed

zimeg deleted the zimeg-feat-web-api-chat-streamer branch September 30, 2025 15:52

feat(web-api): add a chat stream method to the web client #2379

feat(web-api): add a chat stream method to the web client #2379

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zimeg commented Sep 24, 2025 •

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