feat (ui/react): support resuming an ongoing stream by jeremyphilemon · Pull Request #6052 · vercel/ai

jeremyphilemon · 2025-04-29T22:25:40Z

Background

This pull request adds the ability for clients to resume an ongoing chat generation stream after a network disconnect.

Summary

This pull request adds support for the useChat hook to resume an ongoing chat generation stream by exposing experimental_resume() that can be called by any client, typically during the initial mount of the hook.

The experimental_resume function makes a GET request to the api endpoint you've initialized the hook with (or /api/chat by default) and streams the contents of the stream if it is active or fails silently if it has ended.

In order for experimental_resume to work as intended, it requires the usage of the resumable-stream package for stream creation and a redis instance for the package to manage the pub/sub mechanism.

Verification

An example has been added at examples/next-openai/app/use-chat-resume to test the feature. Follow the following steps to test it end-to-end:

Run the development server
Navigate to http://localhost:3000/use-chat-resume
Send a message that will have a longer generation duration, example "Write an essay about Michael Jordan"
Once the generation starts, click the chat id above to open the conversation in a new tab
Verify the stream gets resumed

Tasks

Tests have been added / updated (for bug fixes / features)
Documentation has been added / updated (for bug fixes / features)
A patch changeset for relevant packages has been added
Formatting issues have been fixed (run pnpm prettier-fix in the project root)

jeremyphilemon · 2025-04-29T22:51:02Z

v5 version: #6053

lgrammel · 2025-04-30T06:37:03Z

content/docs/04-ai-sdk-ui/03-chatbot-message-persistence.mdx

+4. Returns the latest one to `streamContext.resumableStream()`
+5. Falls back to an empty stream if it’s already closed
+
+```ts filename="app/api/chat/route.ts"


The highlighting is broken - wonder if this will lead to issues with the docs rendering. Did you check it in the docs deployment?

Hmm not sure why github isn't highlighting the code snippet, fwiw I did try building this in the docs deployment and it works!

lgrammel · 2025-04-30T06:38:54Z

packages/react/src/use-chat.ts

+  /**
+   * Resume an ongoing chat generation stream. This does not resume an aborted generation.
+   */
+  experimental_resume: () => Promise<string | null | undefined>;


What is the meaning of the promise return values?

I made it return void

lgrammel · 2025-04-30T06:39:19Z

content/docs/04-ai-sdk-ui/03-chatbot-message-persistence.mdx

  streaming is not yet complete.
 </Note>
+
+## Resuming ongoing streams


cc @nicoalbanese for docs review

lgrammel · 2025-04-30T06:41:15Z

useChat reference docs need updating.

jeremyphilemon · 2025-05-01T01:53:09Z

I added experimental_resume to the reference docs for useChat.

## Background This pull request fixes a docs formatting issue due to a missing comma in useChat reference docs. ## Summary Fixed formatting in useChat reference docs by adding a comma. ## Tasks - [x] Documentation has been added / updated (for bug fixes / features) - [x] Formatting issues have been fixed (run `pnpm prettier-fix` in the project root) ## Related Issues #6052

…ming stream (#6224) ## Background This pull request updates the documentation for the GET handler in the resumable streams section to account for a race condition that may occur when the stream ends in-flight. ## Summary Updated the route by adding the code snippet that handles the above condition. ## Tasks - [x] Documentation has been added / updated (for bug fixes / features) - [x] Formatting issues have been fixed (run `pnpm prettier-fix` in the project root) ## Related Issues #6052

## Background This pull request adds the ability for clients to resume an ongoing chat generation stream after a network disconnect. ## Summary This pull request adds support for the `useChat` hook to resume an ongoing chat generation stream by exposing `experimental_resume()` that can be called by any client, typically during the initial mount of the hook. The `experimental_resume` function makes a `GET` request to the api endpoint you've initialized the hook with (or `/api/chat` by default) and streams the contents of the stream if it is active or fails silently if it has ended. In order for `experimental_resume` to work as intended, it requires the usage of the [`resumable-stream`](https://www.npmjs.com/package/resumable-stream) package for stream creation and a redis instance for the package to manage the pub/sub mechanism. ## Verification An example has been added at `examples/next-openai/app/use-chat-resume` to test the feature. Follow the following steps to test it end-to-end: 1. Run the development server 2. Navigate to `http://localhost:3000/use-chat-resume` 3. Send a message that will have a longer generation duration, example "Write an essay about Michael Jordan" 4. Once the generation starts, click the chat id above to open the conversation in a new tab 5. Verify the stream gets resumed ## Tasks - [x] Tests have been added / updated (for bug fixes / features) - [x] Documentation has been added / updated (for bug fixes / features) - [x] A _patch_ changeset for relevant packages has been added - [x] Formatting issues have been fixed (run `pnpm prettier-fix` in the project root) --------- Co-authored-by: Lars Grammel <lars.grammel@gmail.com>

This pull request adds the ability for clients to resume an ongoing chat generation stream after a network disconnect. This pull request adds support for the `useChat` hook to resume an ongoing chat generation stream by exposing `experimental_resume()` that can be called by any client, typically during the initial mount of the hook. The `experimental_resume` function makes a `GET` request to the api endpoint you've initialized the hook with (or `/api/chat` by default) and streams the contents of the stream if it is active or fails silently if it has ended. In order for `experimental_resume` to work as intended, it requires the usage of the [`resumable-stream`](https://www.npmjs.com/package/resumable-stream) package for stream creation and a redis instance for the package to manage the pub/sub mechanism. An example has been added at `examples/next-openai/app/use-chat-resume` to test the feature. Follow the following steps to test it end-to-end: 1. Run the development server 2. Navigate to `http://localhost:3000/use-chat-resume` 3. Send a message that will have a longer generation duration, example "Write an essay about Michael Jordan" 4. Once the generation starts, click the chat id above to open the conversation in a new tab 5. Verify the stream gets resumed - [x] Tests have been added / updated (for bug fixes / features) - [x] Documentation has been added / updated (for bug fixes / features) - [x] A _patch_ changeset for relevant packages has been added - [x] Formatting issues have been fixed (run `pnpm prettier-fix` in the project root) --------- Co-authored-by: Lars Grammel <lars.grammel@gmail.com>

jeremyphilemon added 16 commits April 25, 2025 09:22

feat (ui/react): support resuming an ongoing stream

10b8eba

resolve merge conflicts

6e15bff

remove KV_URL

fd753e4

move stream context creation inside handler

7dad719

update test

af232ee

format

89b2f75

restore turbo.json

283eea4

fix eslint error

b475105

update docs

2dd7eda

add imports

cad77ab

check for request url and method

cebcca3

update language

64dc198

Merge branch 'main' into jrmy/experimental-resume

c661289

update docs and test syntax

9ab107d

specify code snippet language

02d91ec

reuse callChatApi and differentiate by new param

99f9f6f

vercel bot deployed to Preview April 29, 2025 22:25 View deployment

Merge branch 'main' into jrmy/experimental-resume-2

8383e2a

vercel bot deployed to Preview April 29, 2025 22:28 View deployment

jeremyphilemon mentioned this pull request Apr 29, 2025

feat (ui/react): support resuming an ongoing stream #6000

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lgrammel reviewed Apr 30, 2025

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add function to reference and update return type

3fc8c24

vercel bot deployed to Preview May 1, 2025 01:53 View deployment

update code snippet language

9ea0a1b

vercel bot deployed to Preview May 1, 2025 02:05 View deployment

use tsx as language

4533564

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revert to ts

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use consistent path

05e3ce4

vercel bot deployed to Preview May 1, 2025 02:33 View deployment

Merge branch 'main' into jrmy/experimental-resume-2

67fe0d3

lgrammel approved these changes May 1, 2025

View reviewed changes

vercel bot deployed to Preview May 1, 2025 07:15 View deployment

jeremyphilemon merged commit 6c59ae7 into main May 1, 2025
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jeremyphilemon deleted the jrmy/experimental-resume-2 branch May 1, 2025 07:36

jeremyphilemon mentioned this pull request May 1, 2025

fix (docs): update formatting in useChat reference docs #6099

Merged

2 tasks

This was referenced May 7, 2025

fix (docs): update formatting in useChat reference docs #6100

Merged

chore (docs): update route to handle race condition when resuming stream #6224

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jeremyphilemon mentioned this pull request May 8, 2025

chore (docs): update code snippets to handle race condition when resuming stream #6229

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feat (ui/react): support resuming an ongoing stream#6052

feat (ui/react): support resuming an ongoing stream#6052
jeremyphilemon merged 23 commits intomainfrom
jrmy/experimental-resume-2

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