session-start Hook

The session-start hook fires when a Claude Code session begins (startup, resume, or after compaction). It reads the memory database and injects relevant context from previous sessions directly into the conversation, giving your AI assistant immediate awareness of past decisions, failures, and progress.

Trigger Events

The compact source gets the highest token budget because compaction destroys context that needs to be restored.

What It Does

1. Creates a session record in the memory database with the current git branch
2. Links to task if a plan file reference is detected
3. Builds prioritized context from multiple sources:

- Failed attempts (highest priority -- DO NOT RETRY warnings) - Current session observations (after compaction) - Recent session summaries - Cross-task progress tracking - Recent observations sorted by importance

1. Fills token budget from highest-importance sections first
2. Outputs plain text that Claude Code injects into the conversation

Example Input

{
  "session_id": "abc123-def456",
  "transcript_path": "/Users/dev/.claude/projects/my-app/transcript.jsonl",
  "cwd": "/Users/dev/my-app",
  "hook_event_name": "session_start",
  "source": "startup"
}

Example Output

=== Massu Memory: Previous Session Context ===

### Failed Attempts (DO NOT RETRY)
- drizzle-kit push fails with RLS-enabled tables (2x)
- next-auth getServerSession returns null in middleware

### Session (2026-02-10)
**Task**: Implement database migration system
**Completed**: Added migration CI check, fixed timeout handling
**Plan**: 4/5 complete

### Recent Observations
- [decision|imp:8] Chose Prisma migrate over raw SQL (2026-02-10)
- [bugfix|imp:7] Fixed migration timeout with lock_timeout (2026-02-09)

=== END Massu Memory ===

Context Priority Order

Configuration

The session-start hook uses these config sections:

• team.enabled: If true, includes team-shared observations
• Session and observation data comes from the memory database

No explicit hook configuration is needed -- it works automatically.