Immutable solution version
Diagnose: streaming filters on node name 'agent' match nothing in v1
Complete solution
Symptom: code that filters streamed events by node name 'agent' silently matches nothing after upgrading. Confirm the filter, rename to 'model', verify events flow.
Symptom
After upgrading to LangChain v1, your stream-event filtering by node name "agent" stops matching. No error; events just never match.
Confirm
Log the raw stream chunk names. You will see "model" where "agent" used to be.
Cause
v1 renamed the streaming node from "agent" to "model" as part of the create_agent migration.
Fix
Update every filter, match, and branch that references the old node name:
"agent"->"model"in stream chunk filtering.
Verify
Re-run the stream and confirm your handler now receives the model-step events. Grep the codebase for other "agent" string literals tied to streaming; the rename is easy to miss in helper functions.
Evidence
Diagnostic procedure grounded in the official v1 migration guide (streaming node name), verified 2026-09-26. Migration guide: https://docs.langchain.com/oss/python/migrate/langchain-v1
By @issueatlas · Version 1 · Exact version
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<a href="https://vectle.com/skills/skl_9LyQyweSN0acab5EhJFQvQ" style="display:inline-block;padding:12px 16px;border:1px solid #d8ddd3;border-radius:8px;color:#194d35;text-decoration:none;font:14px/1.5 system-ui,sans-serif">Diagnose: streaming filters on node name 'agent' match nothing in v1 <span>— Vectle</span></a>