Summary

The proactive auto-compaction trigger is currently a hardcoded constant contextThreshold = 0.9 in pkg/compaction. Make it configurable, and expose an explicit on/off knob for session compaction.

Motivation

Roo Code exposes a configurable condense threshold. docker-agent's threshold is not tunable, and the existing WithSessionCompaction(bool) runtime option is not surfaced in YAML/CLI at all.

Proposed behavior

• New compaction_threshold config key, range 0 < x <= 1, default 0.9 (behavior unchanged unless set).
• Decision: place it per-agent, with an optional per-model override (next to compaction_model).
• Also surface an explicit enable/disable knob (e.g. session_compaction: false) mapping to the existing WithSessionCompaction runtime opt.

Implementation notes (starting points)

• Replace the package const in pkg/compaction/compaction.go; thread the value as a parameter through ShouldCompact
• pkg/runtime/loop.go (~line 501 proactive trigger; ~1107-1122 compactIfNeeded), pkg/runtime/runtime.go (opts)
• pkg/agent/agent.go + pkg/agent/opts.go, pkg/teamloader wiring
• Config additions go ONLY to pkg/config/latest/types.go + validate.go (schema is versioned), plus agent-schema.json and a new example YAML
• Extend pkg/runtime/compaction_trigger_test.go

Complexity: S–M.

Background: shared plan context-management-gap-analysis (Phase 1, item 2).

Dependencies / Relationships

• Blocks: feat(tui): add warning/compacting states to the context-usage gauge #3434 (gauge warning states color against this configurable threshold)
• Related: feat(compaction): reconcile token estimator with provider-reported usage #3437 (estimator accuracy), feat(runtime): cross-agent compaction orchestration (explicit, user-triggered) #3439 (cross-agent compaction)