{"record":{"id":"dd0116d9206c42a1","repo":"langchain-ai/langgraph","slug":"stream-events-version-v3-astream-events-versi","errorCode":null,"errorMessage":"stream_events(version='v3') / astream_events(version='v3') do not accept {', '.join(collisions)}; v3 owns these (stream_mode is built from the transformer mux, subgraphs is forced True so nested namespaces flow through scoped muxes).","messagePattern":"stream_events\\(version='v3'\\) / astream_events\\(version='v3'\\) do not accept (.+?); v3 owns these \\(stream_mode is built from the transformer mux, subgraphs is forced True so nested namespaces flow through scoped muxes\\)\\.","errorType":"exception","errorClass":"TypeError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/pregel/main.py","lineNumber":390,"sourceCode":"            bound=self._bound,\n            retry_policy=self._retry_policy,\n            cache_policy=self._cache_policy,\n            timeout=self._timeout,\n        )\n\n\n# Kwargs that ``stream_events(version=\"v3\")`` / ``astream_events(version=\"v3\")``\n# manage internally and must not be overridden by callers. ``stream_mode`` is\n# derived from the transformer mux; ``subgraphs`` is forced True so nested\n# namespaces flow through scoped muxes. Forwarding either to the inner\n# ``stream(...)`` would silently break v3's invariants, so we raise instead.\n_V3_INVARIANT_KWARGS: tuple[str, ...] = (\"stream_mode\", \"subgraphs\")\n\n\ndef _reject_v3_invariant_kwargs(kwargs: dict[str, Any]) -> None:\n    collisions = [k for k in _V3_INVARIANT_KWARGS if k in kwargs]\n    if collisions:\n        raise TypeError(\n            \"stream_events(version='v3') / astream_events(version='v3') do \"\n            f\"not accept {', '.join(collisions)}; v3 owns these \"\n            \"(stream_mode is built from the transformer mux, subgraphs is \"\n            \"forced True so nested namespaces flow through scoped muxes).\"\n        )\n\n\ndef _collect_stream_modes(mux: Any) -> list[StreamMode]:\n    \"\"\"Return the union of `required_stream_modes` across registered transformers.\n\n    Transformers declare the stream modes they need to function, and\n    `stream_events(version=\"v3\")` asks the graph for exactly that union — no hardcoded\n    default set. If zero transformers declare a given mode, the graph\n    does not stream events for it.\n    \"\"\"\n    modes: set[StreamMode] = set()\n    for transformer in mux._transformers:\n        modes.update(","sourceCodeStart":372,"sourceCodeEnd":408,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/pregel/main.py#L372-L408","documentation":"Error \"stream_events(version='v3') / astream_events(version='v3') do not accept {', '.join(collisions)}; v3 owns these (stream_mode is built from the transformer mux, subgraphs is forced True so nested namespaces flow through scoped muxes).\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/pregel/main.py:390 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"38031739e551638e373fb553453256c23feeb41f","analyzedAt":"2026-08-26T18:02:49.312Z","schemaVersion":2},"datasetVersion":"2026-08-26T21:11:00.512Z"}