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fix(sdk): add per-event channel effect selector#2522

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Christian Bromann (christian-bromann) merged 2 commits into
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Jun 10, 2026
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fix(sdk): add per-event channel effect selector#2522
Christian Bromann (christian-bromann) merged 2 commits into
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cb/add-channel-effect-selector

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@christian-bromann Christian Bromann (christian-bromann) commented Jun 10, 2026

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Summary

  • Add a side-effect counterpart to useChannel: useChannelEffect (React, Svelte, Vue) and injectChannelEffect (Angular). It invokes an onEvent callback once per raw protocol event and returns nothing, so it never re-renders — the idiomatic v1 replacement for the removed onLangChainEvent / onCustomEvent callbacks used for analytics/logging.
  • Back all four bindings with a new framework-agnostic acquireChannelEffect(registry, channels, namespace, options) helper in @langchain/langgraph-sdk/stream. It acquires the same ref-counted channelProjection as useChannel (so an effect consumer and a matching useChannel share one server subscription and survive thread swaps), diffs the shared store by event identity, skips events buffered before it attaches (no double-counting history on a late mount), and resets correctly across thread rebinds.
  • API matches the agreed shape with target, enabled, replay (defaults to false/live-only — opposite of useChannel), bufferSize, onEvent, and onError. Callbacks are read from a ref/lazy wrapper so fresh inline closures never re-subscribe.
  • Update selector docs and v1-migration.md in all four SDKs, noting the callback now receives v1 protocol events (lifecycle.*, tools.*, messages.*, custom) rather than legacy LangChain event names.

@open-swe
fix(sdk): add per-event channel effect selector
b0f4b09 
Add useChannelEffect (React/Svelte/Vue) and injectChannelEffect
(Angular) so analytics and logging can react to each raw protocol
event without re-rendering — the v1 replacement for onLangChainEvent /
onCustomEvent. Backed by a framework-agnostic acquireChannelEffect
helper that shares one ref-counted subscription with matching
useChannel consumers.
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🦋 Changeset detected

Latest commit: 48ae3cb

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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@langchain/langgraph-checkpoint

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-checkpoint@2522

@langchain/langgraph-checkpoint-mongodb

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@langchain/langgraph-checkpoint-postgres

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@langchain/langgraph-checkpoint-redis

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@langchain/langgraph-checkpoint-sqlite

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@langchain/langgraph-checkpoint-validation

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create-langgraph

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@langchain/langgraph-api

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-api@2522

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npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-cli@2522

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npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph@2522

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npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-cua@2522

@langchain/langgraph-supervisor

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-supervisor@2522

@langchain/langgraph-swarm

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-swarm@2522

@langchain/langgraph-ui

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-ui@2522

@langchain/langgraph-sdk

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/langgraph-sdk@2522

@langchain/angular

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/angular@2522

@langchain/react

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/react@2522

@langchain/svelte

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@langchain/vue

npm i https://pkg.pr.new/langchain-ai/langgraphjs/@langchain/vue@2522

commit: 48ae3cb

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@christian-bromann Christian Bromann (christian-bromann) merged commit 3855985 into main Jun 10, 2026
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@christian-bromann Christian Bromann (christian-bromann) deleted the cb/add-channel-effect-selector branch June 10, 2026 22:19
This was referenced Jun 10, 2026
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Christian Bromann (christian-bromann) pushed a commit that referenced this pull request Jun 11, 2026
@github-actions
chore: version packages (#2524)
34a0125 
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>
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