bytedance/deer-flow · error · HTTPException

Failed to find branch checkpoint

Error message

Failed to find branch checkpoint

What it means

Error "Failed to find branch checkpoint" thrown in bytedance/deer-flow.

Source

Thrown at backend/app/gateway/routers/threads.py:214

async def _find_branch_checkpoint(
    accessor: Any,
    config: dict[str, Any],
    target_message_ids: set[str],
) -> Any:
    try:
        for snapshot in await accessor.ahistory(config, limit=_BRANCH_HISTORY_RAW_SCAN_LIMIT):
            if is_duration_only_checkpoint(snapshot):
                continue
            if _matches_branch_target(_checkpoint_messages(snapshot), target_message_ids):
                return snapshot
    except _CHECKPOINT_MODE_ERRORS as exc:
        raise _checkpoint_mode_http_error(exc, config.get("configurable", {}).get("thread_id", "")) from exc
    except Exception:
        thread_id = config.get("configurable", {}).get("thread_id", "")
        logger.exception("Failed to scan branch checkpoint history for thread %s", sanitize_log_param(thread_id))
        raise HTTPException(status_code=500, detail="Failed to find branch checkpoint")
    raise HTTPException(status_code=409, detail="This turn can no longer be branched from.")


async def _branch_targets_latest_turn(
    accessor: Any,
    config: dict[str, Any],
    target_message_ids: set[str],
) -> bool:
    """Return whether the target turn is the final visible turn."""
    try:
        for snapshot in await accessor.ahistory(config, limit=_BRANCH_HISTORY_RAW_SCAN_LIMIT):
            if is_duration_only_checkpoint(snapshot):
                continue
            messages = _checkpoint_messages(snapshot)
            if not messages:
                continue
            return _matches_branch_target(messages, target_message_ids)
    except Exception:

View on GitHub (pinned to 1dd6ba1acb)

Solutions

1. Refresh the thread; the checkpoint may have been superseded. Pick a current turn to branch from.
2. Check the Gateway logs for checkpoint read failures indicating storage issues.

When it happens

Trigger: Thrown at backend/app/gateway/routers/threads.py:214 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of bytedance/deer-flow@1dd6ba1acb (2026-08-14). Data as JSON: /api/errors/ac21d4fa7a1ec14d. Report an issue: GitHub.