- Migrated per-object caches (chat/tool starts, model fingerprints, validation contexts, provider indexes, render IDs) from WeakMap to Symbol-keyed properties on the objects themselves.
- Rewrote SSE debug tee as a single-pass inline parser, eliminating the body.tee() + readSseEvents re-parse pipeline.
- Refactored MockModel from a factory function + external WeakMap state into a self-contained class.
- Added FIFO memoization caches for heuristic candidate expansion and namespace suffix lookups.