bytedance/deer-flow · error · HTTPException

history_index is out of range

Error message

history_index is out of range

What it means

Error "history_index is out of range" thrown in bytedance/deer-flow.

Source

Thrown at backend/app/gateway/routers/skills.py:399

            "author": "human",
            "thread_id": None,
            "file_path": SKILL_MD_FILE,
            "prev_content": current_content,
            "new_content": target_content,
            "rollback_from_ts": record.get("ts"),
            "scanner": {"decision": scan.decision, "reason": scan.reason, "static_findings": static_findings},
        }
        if scan.decision == "block":
            await asyncio.to_thread(storage.append_history, skill_name, history_entry)
            raise HTTPException(status_code=400, detail=f"Rollback blocked by security scanner: {scan.reason}")
        await asyncio.to_thread(storage.write_custom_skill, skill_name, SKILL_MD_FILE, target_content)
        await asyncio.to_thread(storage.append_history, skill_name, history_entry)
        await refresh_user_skills_system_prompt_cache_async(get_effective_user_id())
        return await _read_custom_skill_response(skill_name, config)
    except HTTPException:
        raise
    except IndexError:
        raise HTTPException(status_code=400, detail="history_index is out of range")
    except FileNotFoundError as e:
        raise HTTPException(status_code=404, detail=str(e))
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        logger.error("Failed to roll back custom skill %s: %s", skill_name, e, exc_info=True)
        raise HTTPException(status_code=500, detail=f"Failed to roll back custom skill: {str(e)}")


@router.get(
    "/skills/{skill_name}",
    response_model=SkillResponse,
    summary="Get Skill Details",
    description="Retrieve detailed information about a specific skill by its name.",
)
async def get_skill(skill_name: str, config: AppConfig = Depends(get_config)) -> SkillResponse:
    try:
        skill_name = skill_name.replace("\r\n", "").replace("\n", "")

View on GitHub (pinned to 1dd6ba1acb)

Solutions

1. Fetch the skill history list and use a history_index within its bounds (0-based).
2. Refresh the UI; the history may have changed since the index was captured.

When it happens

Trigger: Thrown at backend/app/gateway/routers/skills.py:399 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/e8303347cc7321bc. Report an issue: GitHub.