# 2026-03-01 Session Notes

## Session Continuity Protocol Feature Planning

Nicholai designed a comprehensive feature to help Signet agents survive context window limits by capturing session state checkpoints before compaction. The system uses two data channels: passive accumulation (automatic observation of queries and /remember calls) and agent-initiated digests (via MCP tool, Phase 2).

### Architecture Overview

The implementation spans three phases:
- **Phase 1**: schema, sessionKey plumbing, passive checkpoints, recovery injection, API endpoints
- **Phase 2**: MCP session_digest tool and agent instruction updates  
- **Phase 3**: pre-compaction enrichment, pruning tuning, scorer integration

Checkpoints are stored in a new `session_checkpoints` table with normalized project paths (via realpath) for reliable matching across symlinks. The table uses UUIDs instead of sequences to avoid race conditions on concurrent writes.

### Key Decisions

- **Separate table from memories**: checkpoints have different lifecycle (hours vs weeks), query patterns, and retention. Mixing would pollute the scoring/decay pipeline.
- **Dropped sequence column**: avoids race conditions; ordering by `created_at DESC` instead.
- **Added project_normalized**: resolves symlink aliases for reliable cross-session matching.
- **Buffered checkpoint writes**: 2-3 second debounce to avoid blocking hot paths on user-prompt-submit.
- **Pre-reserved budget for recovery**: 2000-char section injected at session-start before memory injection to guarantee space.

### Implementation Scope

Nine implementation steps identified:
1. SessionKey plumbing in CLI hooks to extract and forward `session_id` from Claude Code
2. Migration 016 for session_checkpoints table and indexes
3. New continuity-state module for per-session accumulation tracking
4. New session-checkpoints module for checkpoint CRUD operations
5. Buffered flush queue (setTimeout-based)
6. Hook integration (session-start, user-prompt-submit, remember, session-end, pre-compaction)
7. CLI parsing updates
8. Redaction of agent-initiated digests before storage
9. Configuration schema under PipelineV2Config

### Open Threads

- Phase 2 and 3 implementation deferred
- MCP session_digest tool design pending
- Pruning policy and retention day thresholds TBD
- Scorer integration with checkpoint relevance ranking pending