docs(chat): document the `fetcher` chat transport for server functions by tombeckenham · Pull Request #681 · TanStack/ai

tombeckenham · 2026-06-02T00:02:50Z

🎯 Changes

Documents the fetcher chat transport added in #512. That PR gave useChat/ChatClient a first-class fetcher option for wiring a TanStack Start server function (one that returns an SSE Response via toServerSentEventsResponse(...)) straight into chat — but it shipped with no docs. The connection-adapters page only covered the stream() connection adapter, which can't typecheck a Promise<Response> (the original gap from #509).

This is a small, docs-only change to docs/chat/connection-adapters.md:

New "Server Functions via fetcher" section with a server + client snippet, modeled on the existing stream() section and the media generation-hook fetcher docs.
A row in the "Pick a Transport" table pointing Response-returning server functions at fetcher.
A fetcher keyword in the page frontmatter for discoverability.
A tip clarifying when to choose fetcher (returns a Response) vs stream() (returns an AsyncIterable<StreamChunk>).

Snippets are checked against the current source (ChatFetcher / ChatFetcherInput in packages/ai-client/src/types.ts) and the examples/ts-react-chat server-fn route.

✅ Checklist

pnpm test:docs (link checker) passes — no broken links.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

🤖 Generated with Claude Code

Summary by CodeRabbit

Documentation
- Added a top-level "fetcher" transport option for server functions that return SSE responses or async iterables.
- Updated the "Pick a Transport" guidance to prefer fetcher when server functions resolve to Response (SSE) or async iterables.
- Documented fetcher arguments (messages, data, threadId, runId, AbortSignal) and abort/stop behavior.
- Clarified when to use fetcher versus synchronous stream-based approaches.

PR #512 added a first-class `fetcher` option to `useChat`/`ChatClient` for wiring a TanStack Start server function (that returns an SSE `Response`) into chat, but the connection-adapters page only covered the `stream()` path. Add a "Server Functions via `fetcher`" section, a "Pick a Transport" row, and a keyword so the new capability is discoverable. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

coderabbitai · 2026-06-02T00:03:03Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 5d485af2-a813-4303-a09e-8ea2bea7669c

📥 Commits

Reviewing files that changed from the base of the PR and between 0793ab7 and ef0bcfa.

📒 Files selected for processing (1)

docs/chat/connection-adapters.md

🚧 Files skipped from review as they are similar to previous changes (1)

docs/chat/connection-adapters.md

📝 Walkthrough

Walkthrough

This PR updates the connection-adapters guide to add fetcher as a transport option and documents using fetcher for TanStack Start server functions that return an SSE Response or a Promise-resolved AsyncIterable<StreamChunk>, including examples, callback signatures (with AbortSignal), and guidance versus stream().

Changes

Server Functions via fetcher Transport

Layer / File(s)	Summary
Navigation and transport selection guidance `docs/chat/connection-adapters.md`	Added `fetcher` to the top transport/topic list and updated the "Pick a Transport" guidance to route Promise-based server functions resolving to `Response` (SSE) or `AsyncIterable<StreamChunk>` to `fetcher` rather than `stream()`.
Server Functions via `fetcher` section and clarifications `docs/chat/connection-adapters.md`	Clarified that `stream()` requires a factory that synchronously returns an `AsyncIterable<StreamChunk>`. Added a new "Server Functions via `fetcher`" section with server/client examples, documented the `fetcher` callback inputs (messages, data, threadId, runId, `AbortSignal`), accepted return types (`Response` with SSE body or `AsyncIterable<StreamChunk>`), and explained `fetcher` vs `stream()` semantics and abort/stop behavior.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Possibly related PRs

TanStack/ai#597: Rewrites the connection-adapters guide and transport-selection framework that this PR extends with the new fetcher transport option.

Poem

🐰
A fetcher hops in, light and spry,
Promises wake SSE in the sky,
Client calls, AbortSignal near,
Chunks arrive — the stream is clear,
Docs snug, doc-rabbit gives a cheer!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: documenting the `fetcher` chat transport for server functions, which aligns with the primary objective of adding documentation for a newly released feature.
Description check	✅ Passed	The description covers the changes comprehensively, explains the motivation, includes a checklist with relevant items checked, and correctly marks this as docs-only with no release impact (no changeset needed).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch docs/chat-fetcher-server-functions

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nx-cloud · 2026-06-02T00:03:34Z

View your CI Pipeline Execution ↗ for commit 5a82e91

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☁️ Nx Cloud last updated this comment at 2026-06-02 00:20:01 UTC

github-actions · 2026-06-02T00:03:35Z

🚀 Changeset Version Preview

No changeset entries found. Merging this PR will not cause a version bump for any packages.

pkg-pr-new · 2026-06-02T00:04:06Z

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commit: ef0bcfa

Drop the "retries" claim (no such feature — the only `retry` in the client is SSE `retry:` control-line parsing) and fix the `stream()` factory description (it returns an `AsyncIterable<StreamChunk>`; it isn't a zero-arg factory). State the verifiable structural fact instead: `fetcher` normalizes to the same request-scoped adapter as `stream()`. Verified the server snippet typechecks without an `as any` cast. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

…vs-iterable A `fetcher` can also return an `AsyncIterable<StreamChunk>` (sync or `Promise`-wrapped), not just a `Response` — the previous tip implied a clean Response/iterable split. The real distinction is that `stream()`'s factory must return the iterable *synchronously*, so an async server-function call (always a `Promise`) needs `fetcher` regardless of what it resolves to. Also corrects the pre-existing `stream()` section, which listed "TanStack Start server functions" as a `stream()` use case — those are async and hit the #509 type error; redirect them to `fetcher` and reframe `stream()` as the synchronous in-process / RSC / test path. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tombeckenhamand others added 2 commits June 2, 2026 10:10

AlemTuzlak approved these changes Jun 2, 2026
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AlemTuzlak merged commit 8aabeec into mainJun 2, 2026
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AlemTuzlak deleted the docs/chat-fetcher-server-functions branch June 2, 2026 06:44

AlemTuzlak mentioned this pull request Jun 4, 2026
feat: host-side MCP client (@tanstack/ai-mcp) #700
Merged

coderabbitaiBot mentioned this pull request Jul 3, 2026
feat: add AI persistence and generation resumability #785
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