Problem

There's no way for consuming applications to react to compaction events. When LCM compacts context, the CompactResult is returned to the caller but not broadcast to any hook/event system. This prevents use cases like:

• Triggering self-improvement evaluation after compaction
• Writing compacted knowledge to external stores (Obsidian, Notion)
• Notifying users when significant context was compacted
• Metrics/telemetry on compaction frequency and efficiency

Proposed Solution

Add optional callback hooks to the plugin config:

1. onCompactionComplete(result: CompactResult) — fires after compact() succeeds, with the full summary content, token delta, and message IDs that were compacted
2. onSummaryCreated(summary: Summary) — fires when a new summary node is inserted into the DAG
3. beforeCompaction(context: CompactionContext) — fires before compaction starts, allowing pre-processing

These could be implemented as:

• Config-defined webhook URLs
• Shell command hooks (like Claude Code's hook system)
• Event emitter on the ContextEngine interface

Workaround

Currently polling the SQLite DB directly for new summaries, which works but is fragile and doesn't give real-time notification.

Context

The engine.ts compact() method and compaction.ts are the natural insertion points. The CompactResult type already contains all the data needed for hooks.