- Centralized catalog and registry handling on `ModelSpec` and `buildModel`, resolving compatibility at model build time.
- Removed runtime compatibility detectors and switched provider request flows to direct `model.compat` reads.
- Added compat fields (`supportsReasoningParams`, `alwaysSendMaxTokens`, `strictResponsesPairing`, `whenThinking`).
- Persisted explicit compatibility overrides through `compatConfig` in discovery and cache merge paths.
- Tracked ACP tool-call inputs per session and replayed them via `toolArgsById`/`getToolArgs` plumbing.
- Merged ACP tool execution end content from start and result events so command output replay preserves original args.
- Scoped ACP async-job draining by session `ownerId` and `agentId` with in-flight tracking and permission-gated deferred turns.
- Refactored compaction telemetry and async tests with per-test telemetry setup and asynchronous teardown resets.
- Added multi-session support to ACP mode enabling session forking, resumption, and closure operations.
- Added session model state reporting and unstable_setSessionModel RPC command for direct model configuration.
- Added turn-level usage tracking and stable message ID tracking for assistant chunks in ACP responses.
- Added Settings.cloneForCwd() method and ExtensionRunner.getFlagValues() for configuration isolation across sessions.
- Fixed ACP session cleanup to properly cancel in-flight prompts and dispose resources on disconnect.
- Refactored AcpAgent to manage multiple concurrent sessions with per-session lifecycle instead of single session.
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