---
phase: 02-data-layer
plan: 01
subsystem: database
tags: [drizzle, sqlite, better-sqlite3, orm, schema]

# Dependency graph
requires:
  - phase: 01
    provides: Core infrastructure (CLI, server, process management)
provides:
  - SQLite database connection factory
  - Task hierarchy schema (initiative -> phase -> plan -> task)
  - Drizzle ORM types for all entities
  - Task dependency relationship table
affects: [03-git-integration, 04-agent-lifecycle, 05-task-dispatch]

# Tech tracking
tech-stack:
  added: [drizzle-orm, better-sqlite3, drizzle-kit]
  patterns: [factory-function-not-singleton, wal-mode, foreign-key-cascades]

key-files:
  created:
    - src/db/config.ts
    - src/db/index.ts
    - src/db/schema.ts
    - drizzle.config.ts
  modified:
    - package.json

key-decisions:
  - "Factory function (not singleton) for database - allows isolated test instances"
  - "WAL mode enabled for better concurrent read performance"
  - "Foreign keys enabled with cascade deletes for data integrity"
  - "Unix timestamps (integers) for SQLite compatibility"
  - "Separate task_dependencies table for many-to-many task relationships"

patterns-established:
  - "Database factory: createDatabase(path?) returns isolated instance"
  - "Schema organization: tables + relations + types in schema.ts"
  - "Environment override: CW_DB_PATH for testing with :memory:"

# Metrics
duration: 3min
completed: 2026-01-30
---

# Phase 2 Plan 1: SQLite Database Setup Summary

**SQLite database with Drizzle ORM and four-level task hierarchy schema (initiative -> phase -> plan -> task)**

## Performance

- **Duration:** 3 min
- **Started:** 2026-01-30T13:22:12Z
- **Completed:** 2026-01-30T13:24:59Z
- **Tasks:** 3
- **Files modified:** 5

## Accomplishments

- Installed Drizzle ORM with better-sqlite3 driver for synchronous SQLite operations
- Created database connection factory with WAL mode and foreign key enforcement
- Defined complete task hierarchy schema with proper cascade delete relationships
- Exported TypeScript types for all entities (Initiative, Phase, Plan, Task, TaskDependency)
- Configured drizzle-kit for future migration support

## Task Commits

Each task was committed atomically:

1. **Task 1: Install Drizzle ORM and SQLite dependencies** - `caf8bb0` (chore)
2. **Task 2: Create database connection factory** - `d7e4649` (feat)
3. **Task 3: Define task hierarchy schema** - `b492f64` (feat)

## Files Created/Modified

- `src/db/config.ts` - Database path resolution with CW_DB_PATH override
- `src/db/index.ts` - createDatabase() factory function with WAL mode
- `src/db/schema.ts` - Complete schema with 5 tables and relations
- `drizzle.config.ts` - Drizzle Kit configuration for migrations
- `package.json` - Added drizzle-orm, better-sqlite3, drizzle-kit dependencies

## Decisions Made

- **Factory over singleton:** createDatabase() returns new instance each call, enabling isolated test databases
- **WAL mode:** Enabled for better concurrent read performance in local-first app
- **Foreign keys on:** SQLite has FK disabled by default, enabled for data integrity
- **Unix timestamps:** Used integer timestamps for SQLite compatibility vs Date objects
- **Separate dependencies table:** task_dependencies junction table instead of JSON array for proper relational queries

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Database foundation complete for repository layer implementation
- Schema ready for CRUD operations in Phase 2 Plan 2
- Types exported for use throughout codebase
- No blockers for continuing

---
*Phase: 02-data-layer*
*Completed: 2026-01-30*
