{"record":{"id":"8f4fedee96ae64e7","repo":"langchain-ai/langgraph","slug":"channel-tasks-is-reserved-and-cannot-be-used-i","errorCode":null,"errorMessage":"Channel '{TASKS}' is reserved and cannot be used in the graph.","messagePattern":"Channel '(.+?)' is reserved and cannot be used in the graph\\.","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/pregel/main.py","lineNumber":805,"sourceCode":"            config_type := deprecated_kwargs.get(\"config_type\", MISSING)\n        ) is not MISSING:\n            warnings.warn(\n                \"`config_type` is deprecated and will be removed. Please use `context_schema` instead.\",\n                category=LangGraphDeprecatedSinceV10,\n                stacklevel=2,\n            )\n\n            if context_schema is None:\n                context_schema = cast(type[ContextT], config_type)\n\n        checkpointer = ensure_valid_checkpointer(checkpointer)\n\n        self.nodes = {\n            k: v.build() if isinstance(v, NodeBuilder) else v for k, v in nodes.items()\n        }\n        self.channels = channels or {}\n        if TASKS in self.channels and not isinstance(self.channels[TASKS], Topic):\n            raise ValueError(\n                f\"Channel '{TASKS}' is reserved and cannot be used in the graph.\"\n            )\n        else:\n            self.channels[TASKS] = Topic(Send, accumulate=False)\n        self.stream_mode = stream_mode\n        self.stream_eager = stream_eager\n        self.output_channels = output_channels\n        self.stream_channels = stream_channels\n        self.interrupt_after_nodes = interrupt_after_nodes\n        self.interrupt_before_nodes = interrupt_before_nodes\n        self.input_channels = input_channels\n        self.step_timeout = step_timeout\n        self.debug = debug if debug is not None else get_debug()\n        self.checkpointer = checkpointer\n        self.store = store\n        self.cache = cache\n        self.retry_policy = (\n            (retry_policy,) if isinstance(retry_policy, RetryPolicy) else retry_policy","sourceCodeStart":787,"sourceCodeEnd":823,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/pregel/main.py#L787-L823","documentation":"Error \"Channel '{TASKS}' is reserved and cannot be used in the graph.\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/pregel/main.py:805 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"}