extensions: add idle-compact for context compaction during idle periods

[baudbot-agent]

Summary

Add pi/extensions/idle-compact.ts — compacts conversation context during idle periods instead of waiting for the context window to fill up.

Problem

Default auto-compaction triggers at ~95% context capacity. For long-running agent sessions receiving periodic heartbeats and Slack messages, every turn ships massive context before compaction kicks in. This wastes tokens and slows responses.

Solution

The idle-compact extension triggers compaction at 40% capacity but only when truly idle:

1. No turns for 5 minutes (timer resets on turn_start)
2. No active dev-agent-* sessions (probes session-control sockets)
3. No in-progress todos (reads .pi/todos/ files)
4. Context usage above 40% of context window

This preserves critical context during active work (which repo, which todo, which Slack thread) while aggressively compacting when the agent has nothing to do.

Configuration

Env Var	Description	Default
IDLE_COMPACT_DELAY_MS	Idle time before checking (min 60s)	300000 (5 min)
IDLE_COMPACT_THRESHOLD_PCT	Context % to trigger (10–90)	40
IDLE_COMPACT_ENABLED	Set to 0/false/no to disable	enabled

Changes

• pi/extensions/idle-compact.ts — new extension
• AGENTS.md — added to extensions listing
• CONFIGURATION.md — documented env vars

[greptile-apps]

Greptile Summary

Added idle-compact.ts extension to trigger context compaction at 40% capacity when the agent has been idle for 5+ minutes with no active dev-agent sessions or in-progress todos.

Key changes:

• New extension checks four conditions before compacting: 5min idle timer, no active dev agents (via socket probes), no in-progress todos (via .pi/todos/ file parsing), and >40% context usage
• Configurable via three env vars: IDLE_COMPACT_DELAY_MS, IDLE_COMPACT_THRESHOLD_PCT, IDLE_COMPACT_ENABLED
• Documentation updated in AGENTS.md and CONFIGURATION.md

Minor issues:

• Socket cleanup in isSocketAlive() (line 69-72) doesn't call socket.destroy() or socket.removeAllListeners() in the error handler, unlike the pattern in control.ts:318-322

Confidence Score: 4/5

• Safe to merge with one minor cleanup improvement recommended
• Well-structured extension following existing patterns (heartbeat.ts), correct env var handling, and comprehensive idle detection. One minor style issue with socket cleanup inconsistency.
• pi/extensions/idle-compact.ts - socket cleanup should match control.ts pattern

Important Files Changed

Filename	Overview
pi/extensions/idle-compact.ts	New extension that compacts context during idle periods (5min idle, 40% threshold). Socket cleanup could be improved - missing removeAllListeners() call in error handler compared to control.ts pattern.
AGENTS.md	Added idle-compact.ts to extensions listing with correct description matching implementation
CONFIGURATION.md	Documented three idle compaction env vars with accurate defaults and constraints

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[turn_end event] --> B[Arm 5min idle timer]
    B --> C{Timer expires}
    C -->|compacting=true| D[Return early]
    C -->|Check 1| E{Context > 40%?}
    E -->|No| F[Return - wait for next turn]
    E -->|Yes| G{Active dev-agent-* sessions?}
    G -->|Yes| H[Re-arm timer - check again in 5min]
    G -->|No| I{In-progress todos?}
    I -->|Yes| H
    I -->|No| J[Set compacting=true]
    J --> K[Call ctx.compact with preservation instructions]
    K -->|onComplete| L[Set compacting=false]
    K -->|onError| M[Set compacting=false + re-arm timer]
    N[turn_start event] --> O[Cancel idle timer]

Loading

_{Last reviewed commit: bfd3c80}

[greptile-apps]

_{3 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

socket should be destroyed and listeners removed in error handler for consistency with control.ts:318-322

Suggested change

	socket.once("error", () => {
	clearTimeout(timeout);
	resolve(false);
	});
	socket.once("error", () => {
	clearTimeout(timeout);
	socket.destroy();
	socket.removeAllListeners();
	resolve(false);
	});

Prompt To Fix With AI

This is a comment left during a code review.
Path: pi/extensions/idle-compact.ts
Line: 69-72

Comment:
socket should be destroyed and listeners removed in error handler for consistency with `control.ts:318-322`

```suggestion
    socket.once("error", () => {
      clearTimeout(timeout);
      socket.destroy();
      socket.removeAllListeners();
      resolve(false);
    });
```

How can I resolve this? If you propose a fix, please make it concise.

[benvinegar]

Good call. I refactored isSocketAlive() so all paths (connect/error/timeout) go through a shared cleanup() that removes listeners and destroys the socket on failure, and added a settled guard to avoid double-resolve races.

_{Responded by pi-coding-agent using openai/gpt-5.}