---
phase: 06-history-api
plan: 01
subsystem: api
tags: [fastapi, sqlalchemy, pagination, timeline, rbac]

# Dependency graph
requires:
  - phase: 05-diff-engine
    provides: router_config_changes and router_config_diffs tables with parsed change data
provides:
  - GET /api/tenants/{tid}/devices/{did}/config-history endpoint
  - get_config_history service function with pagination
affects: [06-02, frontend-config-history]

# Tech tracking
tech-stack:
  added: []
  patterns: [raw SQL text() joins for timeline queries, same RBAC pattern as config_backups]

key-files:
  created:
    - backend/app/services/config_history_service.py
    - backend/app/routers/config_history.py
    - backend/tests/test_config_history_service.py
  modified:
    - backend/app/main.py

key-decisions:
  - "Raw SQL text() for JOIN query consistent with config_diff_service.py pattern"
  - "Pagination defaults: limit=50, offset=0 with validation (ge=1, le=200 for limit)"

patterns-established:
  - "Config history queries use JOIN between changes and diffs tables for timeline view"

requirements-completed: [API-01, API-04]

# Metrics
duration: 2min
completed: 2026-03-13
---

# Phase 6 Plan 1: Config History Timeline Summary

**GET /config-history endpoint returning paginated change timeline with component, summary, timestamp, and diff metadata via JOIN query**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-13T03:58:03Z
- **Completed:** 2026-03-13T04:00:00Z
- **Tasks:** 2
- **Files modified:** 4

## Accomplishments
- Config history service querying router_config_changes JOIN router_config_diffs for timeline entries
- REST endpoint with viewer+ RBAC and config:read scope enforcement
- 4 unit tests covering formatting, empty results, pagination, and ordering
- Router registered in main.py alongside existing config routers

## Task Commits

Each task was committed atomically:

1. **Task 1: Config history service and tests (TDD)** - `f7d5aec` (feat)
2. **Task 2: Config history router and main.py registration** - `5c56344` (feat)

## Files Created/Modified
- `backend/app/services/config_history_service.py` - Query function for paginated config change timeline
- `backend/app/routers/config_history.py` - REST endpoint with RBAC, pagination query params
- `backend/tests/test_config_history_service.py` - 4 unit tests with AsyncMock sessions
- `backend/app/main.py` - Router import and registration

## Decisions Made
- Used raw SQL text() for the JOIN query, consistent with config_diff_service.py pattern
- Pagination limit constrained to 1-200 via FastAPI Query validation
- Copied _check_tenant_access helper (same pattern as config_backups.py)

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered
None

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Config history timeline endpoint ready for frontend consumption
- Plan 06-02 can build on this for detailed diff view endpoints

---
*Phase: 06-history-api*
*Completed: 2026-03-13*