prepareRegenerateStream missing context parameter in payload

When regenerating/editing messages, the context parameter is not included in the LangGraph run payload, causing agent context to be undefined on the backend.

File

integrations/langgraph/typescript/src/agent.ts

Root Cause

prepareStream (line 344-354) includes context:

const payload = {
  ...restProps,
  command,
  streamMode,
  input: payloadInput,
  config: payloadConfig,
  context: {
    ...context,
    ...(payloadConfig?.configurable ?? {}),
  }
};

prepareRegenerateStream (line 216-226) does NOT include context:

const payload = {
  ...(input.forwardedProps ?? {}),
  input: this.langGraphDefaultMergeState(
    timeTravelCheckpoint.values,
    [messageCheckpoint],
    input,
  ),
  checkpointId: fork.checkpoint.checkpoint_id!,
  streamMode,
};

Expected Behavior

Both methods should pass context to LangGraph so agent context is available regardless of whether it's a new message or a regeneration.

Reproduction:

1. Use useAgentContext to provide context (e.g., model settings)
2. Send a new message → context works ✅
3. Edit the message and resend → context is undefined ❌

Suggested Fix: Add context to the payload in prepareRegenerateStream:

const payload = {
  ...(input.forwardedProps ?? {}),
  input: this.langGraphDefaultMergeState(
    timeTravelCheckpoint.values,
    [messageCheckpoint],
    input,
  ),
  checkpointId: fork.checkpoint.checkpoint_id!,
  streamMode,
  context: input.context,  // Add this line
};