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docs(langsmith): event-streaming API page for langgraph-api 0.9.0rc1#4132

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docs(langsmith): event-streaming API page for langgraph-api 0.9.0rc1#4132
Nick Hollon (nick-hollon-lc) wants to merge 3 commits into
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@nick-hollon-lc Nick Hollon (nick-hollon-lc) commented May 21, 2026

Summary

New langsmith/event-streaming page covering the v3 thread-centric streaming API in the LangGraph SDK (client.threads.stream(...)) for langgraph-api>=0.9.0rc1, plus the surrounding nav wiring and a Tip on the legacy streaming page pointing new applications at it.

The page (Python, JavaScript, and cURL) was validated against:

  • Python SDK: langchain-ai/langgraph#7884 (nh/sdk-py-v3-streaming-integration-pytest), diffed against main — covers the full v3 streaming stack under libs/sdk-py/langgraph_sdk/_async/, _sync/, and stream/.
  • JavaScript SDK: langchain-ai/langgraphjs main (libs/sdk/src/client/stream/, libs/sdk/src/client/threads/), plus the canonical examples/streaming/src/human-in-the-loop/remote.ts and examples/streaming/src/basic/remote.ts examples.
  • Wire protocol: libs/sdk-py/langgraph_sdk/stream/transport/http.py for the URL shape, build_event_stream_body for the /stream/events body, and send_command for the /commands JSON-RPC envelope.

Notable corrections vs. the initial scaffold

  • thread.run.respond(response, *, interrupt_id=...) — namespace is derived from the matched interrupt, not a parameter.
  • JS interrupt resume uses thread.input.respond({...}) (the InputModule), and interrupt.interruptId is camelCase on the JS side while the wire param stays interrupt_id.
  • client.threads.stream(...) in JS is synchronous and takes either (options) or (threadId, options) — dropped spurious await and undefined first arg.
  • thread.subscribe([...]) is an AsyncIterator in Python (iterate, do not async with) and a Promise<SubscriptionHandle> in JS (must be await-ed).
  • cURL examples now reflect the actual two-endpoint wire protocol: POST /stream/events with {"channels": [...]} opens the SSE subscription, and POST /commands carries the JSON-RPC run.start / input.respond envelopes.
  • Removed nonexistent thread.audio / images / video / files projections.
  • Removed running from the lifecycle event list — v3 emits started, completed, failed, interrupted.
  • Rewrote the "Resume from last event" section: since= is internal to the SDK; reopening the subscription with the same thread_id is the public path.
  • Noted that thread.subagents is an alias for thread.subgraphs.

Worth a careful look

  • The version pins in the top-of-page Note (langgraph-api>=0.9.0rc1, langgraph>=1.2.0, langgraph-sdk>=0.3.14, @langchain/langgraph-sdk>=1.9.2) — PR 7884 doesn't bump version files, so please confirm against the release notes / package manifests before merging.
  • The Resume from last event rewrite still says reopening replays from the start of the run — confirm against the production buffering policy if there's a TTL.
  • AI agent involvement: this PR (and the validation pass against PR 7884 / langgraphjs main) was drafted with Claude Code.

Test plan

  • make lint_prose FILES="src/langsmith/event-streaming.mdx" — clean
  • make broken-links — no broken links
  • Mintlify preview: render the page locally and confirm the Tabs, Notes, and code highlighting all render correctly
  • Smoke-test the Python Quickstart snippet against a langgraph-api>=0.9.0rc1 deployment
  • Smoke-test the JS Quickstart snippet against the same deployment

@nick-hollon-lc
docs(langsmith): scaffold event-streaming page for langgraph-api 0.9.…
02e2fcf 
…0rc1
@nick-hollon-lc
docs(langsmith): wire event-streaming page into nav and legacy refs
5c7ea38 
- Add Tip at the top of langsmith/streaming.mdx pointing new
  applications to /langsmith/event-streaming for langgraph-api
  0.9.0rc1+; rest of the legacy page untouched.
- Add "langsmith/event-streaming" to the Agent deployment → Core
  capabilities nav group in src/docs.json, immediately before the
  legacy "langsmith/streaming" entry (mirrors OSS nav ordering).
- Add an Event streaming Card to core-capabilities.mdx above the
  legacy Streaming API Card; reframe the legacy entry as supported
  alongside.
- Fix em-dash spacing in the event-streaming intro and the new Tip
  (LangChain.DashesSpaces Vale rule).
@nick-hollon-lc
docs(langsmith): validate event-streaming page against langgraph PR 7884
9baf59d 
Validate the Python SDK examples against the v3 streaming code in
langchain-ai/langgraph#7884 and the JS SDK examples against
langchain-ai/langgraphjs main, and fix the divergences.

Python SDK
- thread.run.respond uses (response, *, interrupt_id=...) — namespace
  is derived from the matched interrupt, not a parameter.
- thread.subscribe(...) returns an AsyncIterator; iterate it directly
  instead of opening as an async context manager.

JS SDK
- client.threads.stream(...) is synchronous and takes either an
  options object or (threadId, options) — drop spurious await and
  undefined first arg.
- Interrupt resume goes through thread.input.respond({...}); the
  interrupt object surfaces interruptId in camelCase while the wire
  param keeps snake_case interrupt_id.
- await thread.subscribe([...]) — subscribe returns a Promise.

Wire protocol (cURL)
- Stream-open POST body is {"channels": [...]} (plus optional
  namespaces / depth). Replace the fabricated assistant_id/input
  bodies in every per-projection example.
- run.start is a separate command on POST /threads/{id}/commands with
  a JSON-RPC envelope: {"id": N, "method": "run.start", "params": {
  "assistant_id": ..., "input": ...}}.
- Interrupt resume uses {"id": N, "method": "input.respond",
  "params": {"namespace": ..., "interrupt_id": ..., "response": ...}}
  instead of the fabricated command/type shape.

Other corrections
- Drop thread.audio / images / video / files from the projections
  table — they don't exist in the SDK.
- Note thread.subagents is an alias for thread.subgraphs.
- Remove "running" from the lifecycle event list — v3 emits started,
  completed, failed, interrupted.
- Rewrite "Resume from last event": since= is internal to the SDK,
  and the wire protocol does not use Last-Event-ID for resumption;
  the server replays buffered events on every new subscription and
  the SDK dedupes by seq / event_id.

Also tweak core-capabilities and streaming intro wording for
consistency with the corrected page.
@github-actions github-actions Bot added the langsmith For docs changes to LangSmith label May 21, 2026
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github-actions Bot commented May 21, 2026

Thanks for opening a docs PR, Nick Hollon (@nick-hollon-lc)! When it's ready for review, please add the relevant reviewers:

  • @katmayb or @fjmorris (LangSmith)

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github-actions Bot commented May 21, 2026

Mintlify preview branch generated: preview-nhlang-1779401817-6c3eb92

Site preview: https://langchain-5e9cc07a-preview-nhlang-1779401817-6c3eb92.mintlify.app

Preview links may take a few minutes to start working while the deployment finishes.

Changed documentation pages (preview deep links):

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