HKUDS/Vibe-Trading · error · ValueError

start_date must be on or before end_date

Error message

start_date must be on or before end_date

What it means

Final date check in _validate_backtest_dates: after both dates parse successfully, start must not be after end. Inverted ranges would produce empty or nonsensical backtests, so they are rejected up front.

Solutions

  1. Swap the arguments so the earlier date is start_date
  2. Order programmatically: start, end = sorted([start, end])
  3. Assert ordering in tests that exercise the execute path

Example fix

// before
execute(start_date=end, end_date=start)
// after
execute(start_date=start, end_date=end)
Defensive patterns

Strategy: validation

Validate before calling

from datetime import date
sd, ed = date.fromisoformat(start_date), date.fromisoformat(end_date)
assert sd <= ed

Type guard

def dates_ordered(s: str, e: str) -> bool:
    from datetime import date
    return date.fromisoformat(s) <= date.fromisoformat(e)

Try / catch

try:
    _validate_backtest_dates(start_date, end_date)
except ValueError as e:
    if 'on or before' in str(e):
        start_date, end_date = end_date, start_date

Prevention

When it happens

Trigger: Calling autopilot execute with start_date='2024-01-01' and end_date='2023-12-31' — both well-formed but ordered wrongly.

Common situations: Parameter order swaps in wrapper code; date pickers returning (to, from); LLM misordering 'from'/'to' fields.

Related errors

AI-assisted analysis of HKUDS/Vibe-Trading@80ffdda44c (2026-08-28). Data as JSON: /api/errors/2ea6fc6e6a3fb7ab. Report an issue: GitHub.

Appendix: source

Thrown at agent/src/tools/autopilot_tool.py:247

        return candidate, None
    return "auto", (
        f"hypothesis data_source {candidate!r} is not a known loader source; "
        "fell back to 'auto'"
    )


def _validate_backtest_dates(start_date: str, end_date: str) -> None:
    """Validate backtest dates before writing any run artifacts."""
    try:
        start = datetime.strptime(start_date, "%Y-%m-%d").date()
    except ValueError as exc:
        raise ValueError("start_date must be YYYY-MM-DD") from exc
    try:
        end = datetime.strptime(end_date, "%Y-%m-%d").date()
    except ValueError as exc:
        raise ValueError("end_date must be YYYY-MM-DD") from exc
    if start > end:
        raise ValueError("start_date must be on or before end_date")


def _run_dir_for_hypothesis(hypothesis_id: str) -> Path:
    """Return a path-contained run directory for any persisted hypothesis id."""
    suffix = hashlib.sha256(hypothesis_id.encode("utf-8")).hexdigest()[:12]
    return Path.home() / ".vibe-trading" / "runs" / f"autopilot_{suffix}"


class GenerateBacktestConfigTool(BaseTool):
    """Generate backtest config.json from a research hypothesis.

    Reads a hypothesis, derives config fields from its universe and
    data_sources, and writes a ready-to-run config.json to a run directory.
    The agent should then create signal_engine.py from the signal_definition
    and call the backtest tool.
    """

    name = "generate_backtest_config"

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