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agentsop-state-reducer

Tool skill for declaring reducers on LangGraph state keys so parallel writes merge instead of crashing. Activates whenever a coder agent designs a StateGraph with parallel branches, fan-out via Send, multi-agent topologies, or whenever a run raises `InvalidUpdateError: At key '<k>': Can receive only one value per step`. Encodes the rule "every state key is single-writer or has a reducer — nothing in between."

skills/agentsop-state-reducer/SKILL.md

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Oct 24, 2026
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# State Reducer · Tool Skill

> Scope: a single decision — for each state key, declare a reducer or
> guarantee single-writer. Out of scope: checkpointers, HITL, supervisor vs.
> swarm — see `langgraph-sop` for those.

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## 1. 何时激活 (Activation Rules)

Activate when **any** trigger fires:

- The task involves a LangGraph `StateGraph`, `TypedDict`/`BaseModel` schema,
  or `Annotated[..., <reducer>]` typing.