Summary

Adds hook events before and after context compaction to allow agents to save and restore working state across compaction boundaries.

Motivation

When context compaction occurs (either manually via /compact or automatically on context overflow), agents lose their working state. This makes it difficult for memory systems to preserve continuity across compaction.

With these hooks, a memory skill can:

1. Pre-compaction: Capture the current task state, recent decisions, and working context
2. Post-compaction: Inject that state back into the agent's context

Events

session:compact:pre

Fired before compaction begins. Context includes:

• sessionId: Session identifier
• sessionFile: Path to session transcript
• workspaceDir: Agent workspace directory
• messageCount: Number of messages before compaction

session:compact:post

Fired after compaction completes. Context includes:

• sessionId: Session identifier
• sessionFile: Path to session transcript
• workspaceDir: Agent workspace directory
• summary: Compaction summary generated by the model
• tokensBefore: Token count before compaction
• tokensAfter: Token count after compaction
• firstKeptEntryId: ID of first kept message

Example Hook

const handler: HookHandler = async (event) => {
  if (event.type === 'session' && event.action === 'compact:pre') {
    // Save working state before compaction
    const state = await captureAgentState(event.context.workspaceDir);
    await saveToMemory(state);
  }
  
  if (event.type === 'session' && event.action === 'compact:post') {
    // Inject state back after compaction
    const state = await loadFromMemory();
    await injectContext(event.context.workspaceDir, state);
  }
};

Testing

• Tested with manual /compact command
• Tested with auto-compaction on context overflow
• Hooks fire in correct order (pre before, post after)

Related

This enables memory skills like openclaw-memory to maintain continuity across compaction events.

Greptile Overview

Greptile Summary

Adds two new internal hook events around Pi session compaction (session:compact:pre and session:compact:post) so hooks can persist and restore agent working state across manual or automatic compaction. Implementation wires these events into the embedded Pi compaction flow (src/agents/pi-embedded-runner/compact.ts) and documents the new events and their context fields in docs/hooks.md.

Confidence Score: 3/5

• Generally safe to merge, but event timing/semantics likely don’t match the documented intent for pre-compaction state capture.
• Changes are localized and straightforward, but session:compact:pre currently fires after history is already pruned/replaced, which undermines the primary use-case (capturing full pre-compaction state). Additionally, hook errors are swallowed by the internal hook dispatcher so failures won’t be visible to callers.
• src/agents/pi-embedded-runner/compact.ts

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Context used:

• Context from dashboard - CLAUDE.md (source)
• Context from dashboard - AGENTS.md (source)