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+# 2026-02-27 Session Notes
+
+## DataFetcher SQLite Migration Plan
+
+Session began with a detailed plan to refactor the data fetcher in the pm-kalshi crate to write trades directly to SQLite (`historical.db`) instead of CSV. The backtester now loads from SQLite but the database has 3.5M markets with zero trades because the fetcher never populated it.
+
+## Key Implementation Strategy
+
+The plan involves six coordinated changes:
+1. Add `Arc<SqliteStore>` field to DataFetcher struct
+2. Replace `append_trades_csv()` method with `insert_trades_batch()` that calls the store's batch insert method
+3. Remove all CSV file operations from `fetch_range()` 
+4. Update `get_available_data()` to query `historical_trades` table instead of scanning files
+5. Update DataFetcher construction in AppState and main.rs to create and share a SqliteStore for historical.db
+6. Update backtest handler to use the shared historical_store instead of opening a new connection per request
+
+## Technical Details Captured
+
+- Trade tuple format: `(timestamp, ticker, price, volume, side)` as strings/i64
+- Price conversion: yes_price is in cents (integer), divide by 100.0 for decimal format
+- Batch size: 10,000 trades per batch (reusing existing batch size constant)
+- SqliteStore API methods: `insert_historical_trades_batch()` and `count_historical_trades()`
+- Files to modify: fetcher.rs, web/mod.rs, main.rs, web/handlers.rs
+
+## Session Status
+
+Plan documented and ready for implementation. No code changes have been made yet.
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