{"record":{"id":"4de2f8c1251bef37","repo":"langchain-ai/langgraph","slug":"attempting-to-delete-a-message-with-an-id-that-doe","errorCode":null,"errorMessage":"Attempting to delete a message with an ID that doesn't exist ('{m.id}')","messagePattern":"Attempting to delete a message with an ID that doesn't exist \\('(.+?)'\\)","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/graph/message.py","lineNumber":228,"sourceCode":"            remove_all_idx = idx\n\n    if remove_all_idx is not None:\n        return right[remove_all_idx + 1 :]\n\n    # merge\n    merged = left.copy()\n    merged_by_id = {m.id: i for i, m in enumerate(merged)}\n    ids_to_remove = set()\n    for m in right:\n        if (existing_idx := merged_by_id.get(m.id)) is not None:\n            if isinstance(m, RemoveMessage):\n                ids_to_remove.add(m.id)\n            else:\n                ids_to_remove.discard(m.id)\n                merged[existing_idx] = m\n        else:\n            if isinstance(m, RemoveMessage):\n                raise ValueError(\n                    f\"Attempting to delete a message with an ID that doesn't exist ('{m.id}')\"\n                )\n\n            merged_by_id[m.id] = len(merged)\n            merged.append(m)\n    merged = [m for m in merged if m.id not in ids_to_remove]\n\n    if format == \"langchain-openai\":\n        merged = _format_messages(merged)\n    elif format:\n        msg = f\"Unrecognized {format=}. Expected one of 'langchain-openai', None.\"\n        raise ValueError(msg)\n    else:\n        pass\n\n    return merged\n\n","sourceCodeStart":210,"sourceCodeEnd":246,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/graph/message.py#L210-L246","documentation":"Error \"Attempting to delete a message with an ID that doesn't exist ('{m.id}')\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/graph/message.py:228 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"}