# Phase 2 Plan 3: Entity Resolution Pipeline Summary
Two-phase EntityResolver using rapidfuzz fuzzy matching with optional fastembed cosine similarity confirmation, Union-Find for transitive grouping, and richest-metadata merge strategy.
## What Was Built
### EntityResolver (`src/skill_retriever/nodes/ingestion/resolver.py`)
- **Phase 1 (Fuzzy):** Groups entities by component_type (blocking), then compares names within groups using `fuzz.token_sort_ratio`. Pairs above `fuzzy_threshold` (default 80.0) become candidates.
- **Phase 2 (Embeddings):** Optional confirmation step. Computes cosine similarity on "{name} {description}" embeddings via fastembed TextEmbedding. Pairs above `embedding_threshold` (default 0.85) are confirmed. Skipped when no embedding_model is provided (fuzzy-only mode).
- **Union-Find:** Transitive duplicate pairs are merged into groups (A~B and B~C yields {A,B,C}).
- **Merge Strategy:** Keeps entity with richest metadata (longest description, most tags, most tools). Unions tags and tools from all group members. Keeps most recent `last_updated`.
### Tests (`tests/test_resolver.py`)
8 test cases covering:
1. Exact duplicate merging
2. Similar name merging (hyphen vs underscore)
3. Blocking by component_type (same name, different type not merged)
4. Embedding rejection of divergent descriptions (with mock embedding model)
5. Empty input
6. No duplicates (all unique)
7. Richest metadata preservation (tags/tools union, longest description, latest timestamp)
8. Transitive duplicate merging (A~B~C -> single entity)
## Verification Results
- **pytest:** 8/8 passed
- **pyright:** 0 errors, 0 warnings
- **ruff:** All checks passed
## Deviations from Plan
None - plan executed exactly as written.
## Decisions Made
| Decision | Rationale |
|----------|-----------|
| ComponentMetadata import in TYPE_CHECKING block | Follows project ruff TC001 convention; works with `from __future__ import annotations` |
| Sorted output for merged tags/tools | Deterministic output for testing and reproducibility |
| Richness scoring as (description_len, tags_count, tools_count) tuple | Natural Python tuple comparison gives priority to description length |
## Key Files
| File | Action | Purpose |
|------|--------|---------|
| `src/skill_retriever/nodes/ingestion/resolver.py` | Created | EntityResolver with two-phase pipeline |
| `tests/test_resolver.py` | Created | 8 test cases for resolver |
## Commits
| Hash | Message |
|------|---------|
| `5467184` | feat(02-03): two-phase entity resolution pipeline |
## Duration
~5 minutes
## Next Phase Readiness
- EntityResolver ready for integration into ingestion workflow
- Fuzzy-only mode enables fast unit testing without model downloads
- Embedding confirmation path ready for integration tests with real fastembed models
