fix(sdk): reconnect v2 SSE and WebSocket thread streams after disconnect by christian-bromann · Pull Request #2462 · langchain-ai/langgraphjs

Christian Bromann (christian-bromann) · 2026-06-01T22:31:48Z

Summary

Add automatic reconnect for v2 ProtocolSseTransportAdapter and ProtocolWebSocketTransportAdapter (resume via since on SSE, full buffer replay on WebSocket, with MaxWebSocketReconnectAttemptsError when the budget is exceeded).
Wire AsyncCaller and reconnect defaults through client.threads.stream, with optional maxReconnectAttempts, reconnectDelayMs, and onReconnect on ThreadStreamOptions.
Disable auto-reconnect when a custom fetch is passed (test/mocks), and add pnpm test:int integration tests using client.threads.stream + run.start against an in-process mock server.

changeset-bot · 2026-06-01T22:31:53Z

🦋 Changeset detected

Latest commit: e560c72

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

This PR includes changesets to release 10 packages

Name	Type
@langchain/langgraph-sdk	Patch
@examples/ui-angular	Patch
@examples/ui-react	Patch
@langchain/angular	Patch
@langchain/react	Patch
@langchain/svelte	Patch
@langchain/vue	Patch
@example/ai-elements	Patch
@examples/assistant-ui-claude	Patch
@examples/ui-multimodal	Patch

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commit: e560c72

Add automatic reconnect with resume for protocol transports, route HTTP through AsyncCaller from client.threads.stream, and add integration tests for client.threads.stream + run.start against a mock langgraph-api server.

Co-authored-by: Cursor <cursoragent@cursor.com>

open-swe

Open SWE Review found no issues in the changed lines.

🔍 2 out-of-diff findings

These relate to code outside this PR's changed lines.

🟡 Latest checkpoint delta history is empty — libs/checkpoint/src/memory.ts lines 570-571
When callers request delta-channel history with the normal “latest checkpoint for this thread” config (no checkpoint_id), checkpointId is empty here, so targetEntry is forced to undefined and the parent-chain walk never starts. The base implementation first resolves getTuple(config), which handles the no-checkpoint_id case by selecting the latest checkpoint, but this optimized override skips that behavior. As a result, MemorySaver reconstructs delta channels from { configurable: { thread_id } } with no ancestor writes, so hydrated delta-channel state can be silently empty/stale even though the latest checkpoint has persisted history.
🟡 Idle hydrated threads miss remote runs — libs/sdk/src/stream/controller.ts line 709
This defers the root pump whenever getState() says the thread is currently idle. That works for a purely local next submit(), but it removes the always-on subscription that previously observed server-side runs started elsewhere after the UI mounted. For an existing idle thread opened in one tab/client, a run started from another client has no local submit() to call #startDeferredRootPump, so this controller never subscribes and isLoading, messages, values, interrupts, and discovery state stay stale until a reload/manual action.

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This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## @langchain/langgraph-supervisor@1.1.0 ### Minor Changes - [#2521](#2521) [`56682a6`](56682a6) Thanks [@open-swe](https://github.com/apps/open-swe)! - feat(langgraph-supervisor): Add `addHandoffMessages` to `createSupervisor` and `createHandoffTool`, allowing supervisor-to-agent handoff bookkeeping messages to be omitted from the expert agent's message history. When `addHandoffBackMessages` is not provided, it now defaults to the same value as `addHandoffMessages`, matching the Python package behavior. `createHandoffTool` now also accepts `description` as the preferred option name while continuing to support the existing `agentDescription` option as deprecated for backwards compatibility. ### Patch Changes - [#2407](#2407) [`59d4765`](59d4765) Thanks [@pragnyanramtha](https://github.com/pragnyanramtha)! - Normalize all whitespace in supervisor handoff tool names. ## @langchain/langgraph@1.4.1 ### Patch Changes - [#2520](#2520) [`2da5c33`](2da5c33) Thanks [@christian-bromann](https://github.com/christian-bromann)! - fix(state): validate Zod state updates from nodes Validate node return values and Command updates against Zod state schema constraints before applying them to graph state. Fixes [#2519](#2519) - [#2511](#2511) [`ef04db3`](ef04db3) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(ToolNode): forward graph state to tools via `runtime.state` `ToolNode` now forwards its input to each tool through the second argument as `runtime.state`. When using `ToolNode` as a node in a LangGraph graph, this gives tools access to the current graph state for workflows that need tool-call support in LangGraph proper. Tools can type the second parameter as `ToolRuntime<StateType>` from `@langchain/core/tools` and read `runtime.state` directly. This works in every runtime, including web browsers, and removes the need for `getCurrentTaskInput()` (which relies on `node:async_hooks`/`AsyncLocalStorage`). `getCurrentTaskInput(config)` continues to work for backwards compatibility. - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 ## @langchain/langgraph-sdk@1.9.21 ### Patch Changes - [#2522](#2522) [`3855985`](3855985) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(stream): add per-event side-effect selector Add `useChannelEffect` (React/Svelte/Vue) / `injectChannelEffect` (Angular), a side-effect counterpart to `useChannel` that invokes an `onEvent` callback once per raw protocol event without re-rendering. This is the idiomatic v1 replacement for the old `onLangChainEvent` / `onCustomEvent` callbacks for analytics and logging. Backed by a new framework-agnostic `acquireChannelEffect` helper in `@langchain/langgraph-sdk/stream` that shares a ref-counted subscription with matching `useChannel` consumers. - [#2523](#2523) [`7c3e9e9`](7c3e9e9) Thanks [@christian-bromann](https://github.com/christian-bromann)! - fix(sdk): stop re-streaming seeded messages on idle-thread submit An idle (finished) thread defers its root SSE pump, so the first `submit()` brings it up and the transport replays the finished run from `seq=0`. The replayed `messages` channel carries no step (unlike `values`, guarded by `maxStep`), so it rebuilt each already-complete message from an empty `message-start` and re-streamed the whole turn token-by-token — a visible "messages replay" of the existing conversation. Seal the message ids seeded from the idle `getState()` snapshot so replayed deltas can't downgrade the complete tail; the seal lifts once a newer checkpoint advances the timeline or on thread rebind, and ids from the next run are never sealed. - [#2462](#2462) [`17c44a3`](17c44a3) Thanks [@christian-bromann](https://github.com/christian-bromann)! - fix(sdk): reconnect v2 SSE and WebSocket thread streams after disconnect Add automatic reconnect with resume (`since` for SSE) for protocol transports, wire `AsyncCaller` through `client.threads.stream`, and expose optional reconnect tuning on `ThreadStreamOptions`. Includes integration tests against an in-process mock langgraph-api server. ## @langchain/angular@1.0.22 ### Patch Changes - [#2522](#2522) [`3855985`](3855985) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(stream): add per-event side-effect selector Add `useChannelEffect` (React/Svelte/Vue) / `injectChannelEffect` (Angular), a side-effect counterpart to `useChannel` that invokes an `onEvent` callback once per raw protocol event without re-rendering. This is the idiomatic v1 replacement for the old `onLangChainEvent` / `onCustomEvent` callbacks for analytics and logging. Backed by a new framework-agnostic `acquireChannelEffect` helper in `@langchain/langgraph-sdk/stream` that shares a ref-counted subscription with matching `useChannel` consumers. - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 ## @langchain/react@1.0.22 ### Patch Changes - [#2522](#2522) [`3855985`](3855985) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(stream): add per-event side-effect selector Add `useChannelEffect` (React/Svelte/Vue) / `injectChannelEffect` (Angular), a side-effect counterpart to `useChannel` that invokes an `onEvent` callback once per raw protocol event without re-rendering. This is the idiomatic v1 replacement for the old `onLangChainEvent` / `onCustomEvent` callbacks for analytics and logging. Backed by a new framework-agnostic `acquireChannelEffect` helper in `@langchain/langgraph-sdk/stream` that shares a ref-counted subscription with matching `useChannel` consumers. - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 ## @langchain/svelte@1.0.22 ### Patch Changes - [#2522](#2522) [`3855985`](3855985) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(stream): add per-event side-effect selector Add `useChannelEffect` (React/Svelte/Vue) / `injectChannelEffect` (Angular), a side-effect counterpart to `useChannel` that invokes an `onEvent` callback once per raw protocol event without re-rendering. This is the idiomatic v1 replacement for the old `onLangChainEvent` / `onCustomEvent` callbacks for analytics and logging. Backed by a new framework-agnostic `acquireChannelEffect` helper in `@langchain/langgraph-sdk/stream` that shares a ref-counted subscription with matching `useChannel` consumers. - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 ## @langchain/vue@1.0.22 ### Patch Changes - [#2522](#2522) [`3855985`](3855985) Thanks [@christian-bromann](https://github.com/christian-bromann)! - feat(stream): add per-event side-effect selector Add `useChannelEffect` (React/Svelte/Vue) / `injectChannelEffect` (Angular), a side-effect counterpart to `useChannel` that invokes an `onEvent` callback once per raw protocol event without re-rendering. This is the idiomatic v1 replacement for the old `onLangChainEvent` / `onCustomEvent` callbacks for analytics and logging. Backed by a new framework-agnostic `acquireChannelEffect` helper in `@langchain/langgraph-sdk/stream` that shares a ref-counted subscription with matching `useChannel` consumers. - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 ## @example/ai-elements@0.1.37 ### Patch Changes - Updated dependencies \[[`3855985`](3855985), [`2da5c33`](2da5c33), [`ef04db3`](ef04db3)]: - @langchain/react@1.0.22 - @langchain/langgraph@1.4.1 ## @examples/assistant-ui-claude@0.1.37 ### Patch Changes - Updated dependencies \[[`3855985`](3855985), [`2da5c33`](2da5c33), [`ef04db3`](ef04db3)]: - @langchain/react@1.0.22 - @langchain/langgraph@1.4.1 ## @examples/ui-angular@0.0.47 ### Patch Changes - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`2da5c33`](2da5c33), [`ef04db3`](ef04db3), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 - @langchain/angular@1.0.22 - @langchain/langgraph@1.4.1 ## @examples/ui-multimodal@0.0.23 ### Patch Changes - Updated dependencies \[[`3855985`](3855985), [`2da5c33`](2da5c33), [`ef04db3`](ef04db3)]: - @langchain/react@1.0.22 - @langchain/langgraph@1.4.1 ## @examples/ui-react@0.0.23 ### Patch Changes - Updated dependencies \[[`3855985`](3855985), [`7c3e9e9`](7c3e9e9), [`2da5c33`](2da5c33), [`ef04db3`](ef04db3), [`17c44a3`](17c44a3)]: - @langchain/langgraph-sdk@1.9.21 - @langchain/react@1.0.22 - @langchain/langgraph@1.4.1 ## langgraph@1.0.41 ### Patch Changes - Updated dependencies \[[`2da5c33`](2da5c33), [`ef04db3`](ef04db3)]: - @langchain/langgraph@1.4.1 Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

open-swe Bot reviewed Jun 1, 2026

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Comment thread libs/sdk/src/client/stream/transport/websocket.ts Outdated

Christian Bromann (christian-bromann) and others added 4 commits June 10, 2026 14:57

format

c76c2bc

cr

b47f83b

fix(sdk): make stream reconnect tests node-safe

c60c62c

Co-authored-by: Cursor <cursoragent@cursor.com>

Christian Bromann (christian-bromann) force-pushed the cb/sdk-v2-stream-transport-reconnect branch from 69de1a7 to c60c62c Compare June 10, 2026 22:07

open-swe Bot reviewed Jun 10, 2026

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Christian Bromann (christian-bromann) added the ready label Jun 10, 2026

Open SWE (open-swe) added 2 commits June 10, 2026 16:50

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remove test

e560c72

Christian Bromann (christian-bromann) merged commit 17c44a3 into main Jun 11, 2026
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Christian Bromann (christian-bromann) deleted the cb/sdk-v2-stream-transport-reconnect branch June 11, 2026 00:05

github-actions Bot mentioned this pull request Jun 11, 2026

chore: version packages #2524

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fix(sdk): reconnect v2 SSE and WebSocket thread streams after disconnect#2462

fix(sdk): reconnect v2 SSE and WebSocket thread streams after disconnect#2462
Christian Bromann (christian-bromann) merged 6 commits into
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cb/sdk-v2-stream-transport-reconnect

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Christian Bromann (christian-bromann) commented Jun 1, 2026

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