Add pre-compact hook to auto-trigger /compound workflow

[chekos]

Feature Request

Add a hook that triggers before context compaction (or session end) to check if there's anything worth compounding, and if so, automatically run the /workflows:compound command.

Motivation

The /workflows:compound command captures valuable knowledge - solved problems, learnings, patterns discovered - but requires manual invocation. By the time you think to run it, the context may have already been compacted or the session ended, losing that valuable context.

A pre-compact hook would ensure knowledge gets captured at the optimal moment - when the full context is still available and fresh.

Proposed Behavior

1. Trigger: Before context compaction or session end
2. Check: Analyze the session for compoundable content:
   • Problems that were solved
   • Significant debugging sessions
   • Pattern discoveries or learnings
   • Non-trivial fixes with root cause analysis
3. Action: If compoundable content is detected, prompt to run /workflows:compound (or auto-run based on user preference)

Acceptance Criteria

• Hook triggers before context compaction
• Intelligently detects if session contains compoundable material
• Respects user preference (prompt vs auto-run)
• Doesn't trigger for trivial sessions (simple Q&A, quick fixes)
• Works with the existing /workflows:compound command

Context

Discussed in the Every Discord. This aligns with the core plugin philosophy: "Each unit of engineering work should make subsequent units of work easier—not harder."

Currently, the /workflows:compound command has auto-invoke trigger phrases like "that worked" and "it's fixed", but a pre-compact hook would provide a safety net for capturing knowledge before context is lost.

Related

• /workflows:compound command: plugins/compound-engineering/commands/workflows/compound.md
• Existing auto-invoke triggers (lines 166-169 in compound.md)

[tmchow]

How does the PreCompact hook work with this? Presumably the compaction is happening because the context window has been exhausted. Is running /workflows:compound actually possible?