langchain-ai/langgraph · error · ValueError

Subgraph {recast} not found

Error message

Subgraph {recast} not found

What it means

Error "Subgraph {recast} not found" thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/main.py:1416

        )
        if isinstance(checkpointer, BaseCheckpointSaver):
            checkpointer = self._apply_checkpointer_allowlist(checkpointer)
        if not checkpointer:
            raise ValueError("No checkpointer set")

        if (
            checkpoint_ns := config[CONF].get(CONFIG_KEY_CHECKPOINT_NS, "")
        ) and CONFIG_KEY_CHECKPOINTER not in config[CONF]:
            # remove task_ids from checkpoint_ns
            recast = recast_checkpoint_ns(checkpoint_ns)
            # find the subgraph with the matching name
            for _, pregel in self.get_subgraphs(namespace=recast, recurse=True):
                return pregel.get_state(
                    patch_configurable(config, {CONFIG_KEY_CHECKPOINTER: checkpointer}),
                    subgraphs=subgraphs,
                )
            else:
                raise ValueError(f"Subgraph {recast} not found")

        config = merge_configs(self.config, config) if self.config else config
        if self.checkpointer is True:
            ns = cast(str, config[CONF][CONFIG_KEY_CHECKPOINT_NS])
            config = merge_configs(
                config, {CONF: {CONFIG_KEY_CHECKPOINT_NS: recast_checkpoint_ns(ns)}}
            )
        thread_id = config[CONF][CONFIG_KEY_THREAD_ID]
        if not isinstance(thread_id, str):
            config[CONF][CONFIG_KEY_THREAD_ID] = str(thread_id)

        saved = checkpointer.get_tuple(config)
        return self._prepare_state_snapshot(
            config,
            saved,
            recurse=checkpointer if subgraphs else None,
            apply_pending_writes=CONFIG_KEY_CHECKPOINT_ID not in config[CONF],
        )

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/main.py:1416 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/d02636004b193a78. Report an issue: GitHub.