3. modularize session context - #2190

Note

Modularize AgentSession into compaction, continuation, and refinement coordinators

• Extracts SessionCompaction, SessionContinuation, SessionRefinement, AutoRefinement, and RefinementExecution from AgentSession in agent-session.ts, with each coordinator owning its state, abort controllers, and lifecycle via host callback interfaces.
• Compaction execution moves to compaction-execution.ts, adding extension-provided results, cancellation, and semantic request tracking for summary calls.
• Continuation scheduling moves to continuation.ts, waiting on agent, retry, refinement, queued-work, and compaction barriers before continuing.
• Automatic refinement moves to auto-refinement.ts, handling turn-interval and compact triggers, review cooldowns, and branch invalidation.
• Hardens Python skill imports in bootstrap.ts to pass module names as importlib arguments instead of interpolating into Python source, and fixes Codex model URL trailing-slash normalization in model-registry.ts.
• Adds harness-state digest computation and persistence to AgentSession, inserting a custom digest message when the newest stored or retained digest differs.
• Risk: all test-only internal session shapes (SerializedInternals, SessionInternals, etc.) are restructured to nested refinement/compaction/continuation components; out-of-tree consumers relying on flat _compaction or _refinement fields on AgentSession will break. Compaction and refinement status now read from coordinator state instead of removed in-class fields.

^{Macroscope summarized 5127774.}

Note

Medium Risk
Large refactor of compaction, continuation, and refinement orchestration in the core agent loop; behavior is intended to be preserved but regressions would affect session persistence, cancellation, and headless idle semantics.

Overview
Modularizes session context by moving compaction, post-compaction continuation, and harness refinement out of AgentSession into dedicated session/* coordinators wired through typed host callbacks. Public entry points (compact, refine, host compact.* / refine.*, events, abort/disposal) delegate to the new owners while preserving the documented lifecycle rules (disconnect/reconnect ordering, continuation settlement, serialized refine checkpoints, overflow/threshold behavior).

Compaction splits into SessionCompaction (pending requests, automatic/manual runs, overflow recovery, outcome messages) and performSessionCompaction in compaction-execution.ts (extensions, semantic-edge accounting, transcript rebuild). Continuation moves to SessionContinuation with one-shot settlement and commit-fence gating before agent.continue(). Refinement consolidates in SessionRefinement with AutoRefinement and execution helpers for planning/apply, serialized background plans, disposal drains, and branch invalidation. README adds a session-context ownership table and test pointers.

Hardening: Codex model URL normalization drops regex trailing-slash stripping for a linear scan, and kernel bootstrap checks Python skill imports via importlib.import_module(sys.argv[1]) instead of embedding names in -c source.

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