fix(langgraph-api): recover tool_call args from cumulative-args providers at end of call - #2697
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Serhiy Bzhezytskyy (serhiy-bzhezytskyy) wants to merge 2 commits into
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…ders at end of call A provider that re-sends the cumulative args string per chunk instead of a delta (langchain-ai#2570) leaves messages/partial with a concatenation that never parses. Keep concatenating during the stream; once the model run ends, an args string that does not parse, whose chunks form a growing prefix chain and whose last chunk parses on its own, is replaced by that last chunk in a final messages/partial frame. Anything whose concatenation parses is untouched, so compliant streams never change — including chunks that happen to chain. Output that was already invalid and chains may be read as its only parsing interpretation instead of surfacing as Malformed args; that trade is pinned by a dedicated test.
🦋 Changeset detectedLatest commit: b8f0b5c The changes in this PR will be included in the next version bump. This PR includes changesets to release 3 packages
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…isfy oxfmt The build tsc rejects tool_call_chunks on BaseMessageChunk — the recording loop now runs only for AIMessageChunk, matching the guard the recovery itself already had. Formatting aligned with oxfmt.
@langchain/langgraph-checkpoint
@langchain/langgraph-checkpoint-mongodb
@langchain/langgraph-checkpoint-postgres
@langchain/langgraph-checkpoint-redis
@langchain/langgraph-checkpoint-sqlite
@langchain/langgraph-checkpoint-validation
create-langgraph
@langchain/langgraph-api
@langchain/langgraph-cli
@langchain/langgraph
@langchain/langgraph-cua
@langchain/langgraph-supervisor
@langchain/langgraph-swarm
@langchain/langgraph-ui
@langchain/langgraph-sdk
@langchain/angular
@langchain/react
@langchain/svelte
@langchain/vue
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Summary
Implements the end-of-call recovery proposed in #2570 (comment) for providers that re-send the cumulative tool_call args string per chunk instead of a delta: the concatenation never parses, and
messages/partialends withMalformed args./invalid_tool_callseven though the model's own final message is clean.Changes
src/stream.mts— keep concatenating during the stream; when the model run ends and an args string does not parse, and its chunks form a growing prefix chain whose last chunk parses on its own, a finalmessages/partialframe carries that last chunk instead. Anything whose concatenation parses is untouched; mid-stream frames are unchanged.Test plan
tests/stream.test.mts: cumulative snapshots recovered; compliant deltas untouched, including chunks that happen to chain (self-similar args split at the seam); broken output without a chain preserved; the design trade pinned — already-invalid output that chains is read as its only parsing interpretation ({{"a":1}split as{+{"a":1}); a real compiled graph confirms the productionon_chat_model_endshape fires the recovery and the rebuilt message carries parsedtool_calls; two parallel tool calls stay isolated@langchain/langgraph-api; package suite 108 passed (3 file-load failures identical on cleanmain)Related