feat(langgraph): route executor return values to successor node streams (downstream propagation) #10799

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opened 2026-04-20 14:43:05 +00:00 by hurui200320 · 0 comments

hurui200320 commented

2026-04-20 14:43:05 +00:00

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Metadata

Field	Value
Type	Feature
Priority	Normal
MoSCoW	Should have
Milestone	v3.2.0
Parent	#6511
Branch	feature/m3-node-stream-downstream-propagation
Commit Message	feat(langgraph): route executor return values to successor node streams

Description

_make_on_next_handler in LangGraph currently executes the node executor but discards the return value. The executor returns a StreamMessage containing the node's output, which should be routed to successor node streams based on self.adjacency_list[name] to implement downstream propagation through the reactive graph pipeline.

This was identified during the fix for #6511 (wiring on_next handlers to executors) and explicitly deferred as out of scope for that ticket.

Subtasks

In _make_on_next_handler, capture the return value from executor(msg)
Look up successor nodes via self.adjacency_list[name]
For each successor, send the executor result to the corresponding node stream
Handle edge cases: missing successor streams, conditional routing
Add BDD scenarios covering downstream propagation

Definition of Done

Executor return values are routed to all successor node streams
Conditional edges are respected during propagation
BDD scenarios cover single-successor, multi-successor, and missing-stream cases
All quality gates pass (lint, typecheck, unit_tests, integration_tests, coverage >= 97%)

## Metadata | Field | Value | |-------|-------| | Type | Feature | | Priority | Normal | | MoSCoW | Should have | | Milestone | v3.2.0 | | Parent | #6511 | | Branch | feature/m3-node-stream-downstream-propagation | | Commit Message | feat(langgraph): route executor return values to successor node streams | ## Description `_make_on_next_handler` in `LangGraph` currently executes the node executor but discards the return value. The executor returns a `StreamMessage` containing the node's output, which should be routed to successor node streams based on `self.adjacency_list[name]` to implement downstream propagation through the reactive graph pipeline. This was identified during the fix for #6511 (wiring `on_next` handlers to executors) and explicitly deferred as out of scope for that ticket. ## Subtasks - [ ] In `_make_on_next_handler`, capture the return value from `executor(msg)` - [ ] Look up successor nodes via `self.adjacency_list[name]` - [ ] For each successor, send the executor result to the corresponding node stream - [ ] Handle edge cases: missing successor streams, conditional routing - [ ] Add BDD scenarios covering downstream propagation ## Definition of Done - [ ] Executor return values are routed to all successor node streams - [ ] Conditional edges are respected during propagation - [ ] BDD scenarios cover single-successor, multi-successor, and missing-stream cases - [ ] All quality gates pass (lint, typecheck, unit_tests, integration_tests, coverage >= 97%)

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