Observed error
must write to at least one of [] langgraph
A graph update reported that it had no writable channels. Use the matching public guidance and evidence before changing a production graph.
Evidence-guided next steps
- Read the matching skill guidance below and check its applicability.
- Open the skill’s linked evidence to inspect the observed conditions.
- Verify the fix against the current langgraph documentation before applying it.
Matching public guidance
- LangGraph InvalidUpdateError: Must write to at least one of [...] (state channel name mismatch)
Shows how to fix langGraph InvalidUpdateError: Must write to at least one of [...] (state channel name mismatch). Use it when you hit this exact problem. Skip it when your error message or symptom looks different.
- must write to at least one of [] langgraph
Fixes the LangGraph InvalidUpdateError where a node must write to at least one state channel: shows how to find the node returning None, an empty dict, or undeclared keys, and how to make every branch return a valid state key.
- must write to at least one of []" langgraph
Fixes LangGraph's must write to at least one of error when a node returns nothing usable.