Feature request: PreCompression hook to persist context before automatic compression

When a long conversation approaches context limits, Claude Code automatically compresses prior messages. This compression is aggressive and often loses important details — architectural decisions, task state, reasoning behind changes.

Proposal

Add a PreCompression hook event that fires before context compression occurs. This would allow users to run a script that extracts and saves key context (current plan, decisions made, task progress) to a persistent file (e.g. a .md summary), so the information survives compression and remains available.

Use case

• Long-running sessions where important decisions accumulate over time
• Teams using CLAUDE.md as a knowledge base — a pre-compression hook could auto-update it
• Users who keep sessions open indefinitely and rely on context continuity

Currently available hook events (PreToolUse, PostToolUse, Notification, etc.) don't cover this scenario.