---
phase: 13-engine-min-score-filter
plan: "01"
subsystem: search
tags: [lancedb, hybrid-search, rrf, min-score, filtering]

# Dependency graph
requires: []
provides:
  - "min_score: float = 0.0 parameter on CorpusSearch.hybrid_search()"
  - "Post-retrieval RRF score filter comprehension (FILT-01)"
affects: [14-caller-min-score-filter]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Post-retrieval Python list comprehension for _relevance_score filtering (not LanceDB .where())"
    - "TDD RED-GREEN pattern: failing tests committed before implementation"

key-files:
  created: []
  modified:
    - tests/search/test_engine.py
    - src/corpus_analyzer/search/engine.py

key-decisions:
  - "min_score filter applied post-text-gate, pre-sort on filtered list — _relevance_score is injected by RRFReranker, not stored in LanceDB"
  - "Default min_score=0.0 guarantees zero regression for all existing callers"
  - "Filter uses inclusive >= comparison so exact threshold value always returns at least one result"

patterns-established:
  - "min_score > 0.0 guard: avoids unnecessary comprehension overhead for the common case"

requirements-completed: [FILT-01]

# Metrics
duration: 2min
completed: 2026-02-24
---

# Phase 13 Plan 01: Engine Min-Score Filter Summary

**`min_score: float = 0.0` parameter added to `hybrid_search()` with post-RRF list comprehension filter, keeping all 285 tests green and both ruff and mypy clean**

## Performance

- **Duration:** 2 min
- **Started:** 2026-02-24T06:28:46Z
- **Completed:** 2026-02-24T06:30:47Z
- **Tasks:** 2 (RED + GREEN)
- **Files modified:** 2

## Accomplishments

- Four failing min_score tests written and committed (RED state confirmed with TypeError)
- `min_score: float = 0.0` parameter added to `hybrid_search()` signature with correct docstring
- Post-retrieval filter comprehension inserted after text-gate, before sort block
- Full suite grows from 281 to 285 tests, all green; ruff and mypy both exit 0

## Task Commits

Each task was committed atomically:

1. **Task 1 RED: Write failing min_score tests** - `feb4a74` (test)
2. **Task 2 GREEN: Implement min_score in hybrid_search()** - `d298ec6` (feat)

_Note: TDD tasks have two commits (test RED, then feat GREEN)_

## Files Created/Modified

- `tests/search/test_engine.py` - Four new test functions appended after existing tests
- `src/corpus_analyzer/search/engine.py` - min_score parameter + filter comprehension

## Decisions Made

- Filter applied to `filtered` (post-text-gate list), not raw `results` — consistent with the text-gate pattern and the plan requirement
- Used `if min_score > 0.0:` guard to make 0.0 a true no-op without an extra comprehension pass
- Inclusive `>=` ensures `test_min_score_filters_below_threshold` passes correctly

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- FILT-01 engine requirement complete; Phase 14 can now add min_score to CLI, API, and MCP caller surfaces
- No blockers

---
*Phase: 13-engine-min-score-filter*
*Completed: 2026-02-24*
