fix(sdk): send checkpoint_id in runs.stream() request body

[JessYan (JessYanCoding)]

Summary

RunsStreamPayload extends RunsInvokePayload (libs/sdk/src/types.ts:171, :48), which declares checkpointId — "Checkpoint ID for when creating a new run" (types.ts:70-73). But RunsClient.stream() builds its wire body at runs/index.ts:79-101 and includes checkpoint while omitting checkpoint_id.

So this type-checks, compiles, and silently runs from the thread's latest state instead of forking from the requested checkpoint:

client.runs.stream(threadId, assistantId, { input, checkpointId });

No error is raised, and the caller gets no signal that the checkpoint was ignored.

Reproduction

The same checkpointId passed to all three methods on a real Client, with a stub callerOptions.fetch capturing the outgoing request body:

endpoint	checkpoint_id in body — before	after
/threads/t1/runs/stream	false	true
/threads/t1/runs	true	true
/threads/t1/runs/wait	true	true

Why this looks like a plain omission rather than intent

1. RunsClient.create() (runs/index.ts:151) and RunsClient.wait() (:240) in the same class both send checkpoint_id.
2. The server validates /runs/stream with the same schemas.RunCreate as /runs and /runs/wait — libs/langgraph-api/src/api/runs.mts:181, 257, 268, 342, 383.
3. The field is declared on the very payload type the method accepts.

The field was simply missing from one of three otherwise identical bodies.

The change

One line, placed exactly where create() has it (immediately after checkpoint):

checkpoint_id: payload?.checkpointId,

Tests

Added sends checkpointId as checkpoint_id in the request body to the existing describe("runs.stream()") block in src/client/runs/stream.test.ts, next to the existing body-shape assertions and reusing that file's SSE harness.

Reverse-verified: with the one-line change reverted, the new test fails (expected undefined to be '1f0aaaaa-…'). With it applied, pnpm test in libs/sdk gives 53 files / 779 tests passing, no type errors; pnpm lint and pnpm format:check are clean at the repo root.

A changeset is included (@langchain/langgraph-sdk: patch).

Note

stream() also omits langsmith_tracer, which create() and wait() both send. I left it out to keep this change to a single field — happy to include it here or open a follow-up, whichever you prefer.

---

This contribution was prepared with AI assistance.

[changeset-bot]

🦋 Changeset detected

Latest commit: 60fb4b5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@langchain/langgraph-sdk	Patch
@langchain/angular	Patch
@langchain/react	Patch
@langchain/svelte	Patch
@langchain/vue	Patch

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commit: 60fb4b5

[JessYan (JessYanCoding)]

The five red Unit Tests legs are unrelated to this PR.

Only one test actually fails, and it is on the 26.x leg in a package this PR does not touch — libs/langgraph-core/src/tests/tracing.test.ts:250:

AssertionError: expected 'Hello world from langgrap' to be 'Hello world from langgraph'
Expected: "Hello world from langgraph"
Received: "Hello world from langgrap"

1 failed | 1646 passed — the final streamed token character is dropped. That is #2752, and #2753 pins the 26.x matrix leg to Node 26.7.0. The other four legs end with The operation was canceled, i.e. fail-fast cancellation rather than failures of their own.

In the same run, libs/sdk — the only package this PR changes — reports 53 passed (53), and Check linting, Check formatting, Build, all seven Environment Tests and all four Browser Tests are green.

Happy to rebase once #2753 lands, if that would help.

[Christian Bromann (christian-bromann)]

LGTM 👍