---
phase: "03"
plan: "03-03"
subsystem: memory
tags: [pydantic, persistence, co-selection, usage-tracking]
dependency-graph:
requires: ["02-01"]
provides: ["component-memory", "usage-tracking", "co-selection-queries"]
affects: ["04", "05"]
tech-stack:
added: []
patterns: ["co-selection tracking with lexicographic key invariant", "JSON persistence via Pydantic model_dump_json/model_validate_json"]
key-files:
created:
- src/skill_retriever/memory/component_memory.py
- tests/test_component_memory.py
modified:
- src/skill_retriever/memory/__init__.py
decisions:
- id: "03-03-01"
description: "Co-selection keys use pipe separator (a|b) with lexicographic ordering for deterministic lookup"
- id: "03-03-02"
description: "ComponentMemory uses Pydantic BaseModel (not frozen) to allow in-place mutation of stats"
metrics:
duration: "~4 minutes"
completed: "2026-02-03"
---
# Phase 3 Plan 3: Component Memory Summary
**One-liner:** Usage tracking and co-selection memory with Pydantic persistence using lexicographic pair keys.
## What Was Built
ComponentMemory provides three capabilities:
1. **Recommendation tracking** -- records when components are recommended, with counts and timestamps
2. **Selection tracking** -- records when users select components, updating both individual stats and pairwise co-selection counts
3. **Query methods** -- get_co_selected returns top partners by frequency; get_selection_rate returns selection/recommendation ratio
Persistence uses Pydantic's model_dump_json/model_validate_json for zero-dependency JSON serialization.
## Key Implementation Details
- Co-selection keys are deterministic: components sorted lexicographically, joined with pipe (e.g., "A|B" regardless of selection order)
- itertools.combinations(sorted(ids), 2) generates all unique pairs
- Load from nonexistent path returns empty ComponentMemory (no error)
- All timestamps use UTC via datetime.now(tz=UTC)
## Test Coverage
11 tests across 5 test classes:
- TestRecordRecommendation (2): single and multiple recommendation counts
- TestRecordSelection (3): multi-component selection, key ordering invariant, timestamp verification
- TestCoSelected (2): ranking by frequency, top_k limiting
- TestSelectionRate (2): normal rate calculation, zero-division handling
- TestPersistence (2): save/load round-trip, nonexistent file handling
## Deviations from Plan
### Auto-fixed Issues
**1. [Rule 3 - Blocking] Fixed import sorting in memory __init__.py**
- **Found during:** Task 1
- **Issue:** Another parallel plan (03-02 vector_store) had modified __init__.py with unsorted imports
- **Fix:** Merged all three memory subsystem imports in sorted order, fixed __all__ sorting
- **Files modified:** src/skill_retriever/memory/__init__.py
**2. [Rule 1 - Bug] Removed invalid noqa: TC003 pragma**
- **Found during:** Verification
- **Issue:** ruff flagged unused noqa directive on datetime import (TC003 not triggered with `from __future__ import annotations`)
- **Fix:** Removed the noqa comment
- **Files modified:** src/skill_retriever/memory/component_memory.py
## Commits
| Hash | Message |
|------|---------|
| 67100d6 | feat(03-03): component memory with usage tracking and co-selection |
