The backtest engine uses a fixture provider (synthetic_v1) regardless of
the data_source used for price fetching. We must use the fixture provider's
ID for the scenario, not the data source's ID.
This fixes 'Unsupported provider/pricing combination' error when running
backtests with data_source='databento'.
BREAKING CHANGE: Complete redesign of backtest execution
- Add BacktestJob system with progress stages (validating, fetching_prices, calculating)
- Run backtests in background threads, UI polls for status
- Show progress label with current stage during execution
- Remove synchronous Databento API calls from page load
- Use static default entry spot for initial render (defers API call)
- Make refresh_workspace_seeded_units async with run.io_bound
This fixes:
- 'Connection lost' WebSocket timeout errors
- Slow page load (30s initial load)
- Backtest never completing
The job system provides:
- Non-blocking execution
- Progress tracking with stages
- Error handling with user-friendly messages
- Result caching for retrieval after completion
- Pass data_source to derive_entry_spot in backtests.py
- Remove default 'synthetic' value for data_source in derive_entry_spot and validate_preview_inputs
- Update all tests to explicitly pass data_source parameter
- Improve error message with helpful suggestion for Databento/Yahoo Finance
- Change WindowPolicy from EXACT to BOUNDED for backtest fixture
- Pass data_source to run_read_only_scenario so real data can be used
- Fix injected provider identity preservation in BacktestPageService
- Add type: ignore for BacktestHistoricalProvider protocol assignment
- Revert TypedDict change to avoid cascading type issues in pages/
- Update tests to reflect new BOUNDED policy behavior
Critical fixes:
- Add math.isfinite() check to reject NaN/Infinity in _safe_quote_price
- Raise TypeError instead of silent 0.0 fallback in price_feed.py
- Use dict instead of Mapping for external data validation
Type improvements:
- Add PortfolioSnapshot TypedDict for type safety
- Add DisplayMode and EntryBasisMode Literal types
- Add explicit dict[str, Any] annotation in to_dict()
- Remove cast() in favor of type comment validation
- Fix return type annotation for get_default_premium_for_product
- Add type narrowing for Weight|Money union using _as_money helper
- Add isinstance checks before float() calls for object types
- Add type guard for Decimal.exponent comparison
- Use _unit_typed and _currency_typed properties for type narrowing
- Cast option_type to OptionType Literal after validation
- Fix provider type hierarchy in backtesting services
- Add types-requests to dev dependencies
- Remove '|| true' from CI type-check job
All 36 mypy errors resolved across 15 files.
- Add DatabentoHistoricalPriceSource implementing HistoricalPriceSource protocol
- Smart caching with Parquet storage and metadata tracking
- Auto symbol-to-dataset resolution (GLD→XNAS.BASIC, GC=F→GLBX.MDP3)
- Cache management with age threshold invalidation
- Cost estimation via metadata.get_cost()
- Add databento>=0.30.0 to requirements.txt
- Add DATABENTO_API_KEY to .env.example
- Full test coverage with 16 tests
