# M3.8.6 — M3.8 Composition Gate

| Field | Value |
|---|---|
| Phase | M3.8 — Context optimization |
| Size | M — 1 day |
| Status | ⬜ Not started |
| Depends | M3.8.5 (benchmarks) |
| Blocks | Production deployment |

## Goal

Verify M3.8 implementation meets all safety, performance, and quality constraints
before production rollout.

## Gate Assertions

### Safety (6 assertions)

1. **No data loss** — Optimized chunks preserve all semantic content
   ```rust
   assert!(semantic_similarity(original, optimized) > 0.95);
   ```

2. **Deterministic output** — Same input always produces same output
   ```rust
   assert_eq!(optimize(text), optimize(text));
   ```

3. **Structure preservation** — JSON/logs remain parseable
   ```rust
   assert!(parse_json(&optimized).is_ok());
   assert!(grep_logs(&optimized).count() > 0);
   ```

4. **Metadata preserved** — Breadcrumb, role, provenance untouched
   ```rust
   assert_eq!(original.provenance, optimized.provenance);
   assert_eq!(original.breadcrumb, optimized.breadcrumb);
   ```

5. **Error handling** — Graceful fallback on optimization failure
   ```rust
   assert!(optimize_with_fallback(bad_input).is_ok());
   ```

6. **Thread safety** — Concurrent optimization doesn't corrupt state
   ```rust
   assert!(concurrent_optimize(1000).all_ok());
   ```

### Performance (4 assertions)

1. **Latency** — Per-record optimization <3ms p99
   ```rust
   assert!(latency_p99() < Duration::from_millis(3));
   ```

2. **Throughput** — Sustained 1000+ records/sec
   ```rust
   assert!(throughput_records_per_sec() >= 1000);
   ```

3. **Memory** — Cache stays <100MB (max 1000 entries)
   ```rust
   assert!(cache_size_mb() < 100);
   ```

4. **No regressions** — Existing tests still pass
   ```rust
   assert!(all_prompt_tests_pass());
   assert!(all_ingest_tests_pass());
   ```

### Quality (3 assertions)

1. **Compression targets met** — All content types
   ```rust
   assert!(log_ratio >= 85.0 && log_ratio <= 95.0);
   assert!(json_ratio >= 70.0 && json_ratio <= 90.0);
   assert!(text_ratio >= 30.0 && text_ratio <= 50.0);
   ```

2. **Search quality improves** — pgvector + OpenSearch
   ```rust
   assert!(embedding_similarity > 0.95);
   assert!(opensearch_mrr_improvement > 10);
   ```

3. **No false positives** — Cache eligibility accurate
   ```rust
   assert!(drift_metric_accurate < 0.05);  // <5% error
   ```

## Test Implementation

File: `tests/it_m3_8_gate.rs` (400 LOC)

```rust
#[test]
fn m3_8_gate_no_data_loss() { ... }

#[test]
fn m3_8_gate_deterministic() { ... }

#[test]
fn m3_8_gate_structure_preservation() { ... }

#[test]
fn m3_8_gate_metadata_preservation() { ... }

#[test]
fn m3_8_gate_error_handling() { ... }

#[test]
fn m3_8_gate_thread_safety() { ... }

#[test]
fn m3_8_gate_latency_p99() { ... }

#[test]
fn m3_8_gate_throughput_sustained() { ... }

#[test]
fn m3_8_gate_memory_bounded() { ... }

#[test]
fn m3_8_gate_no_regressions() { ... }

#[test]
fn m3_8_gate_compression_targets() { ... }

#[test]
fn m3_8_gate_search_quality() { ... }

#[test]
fn m3_8_gate_cache_eligibility() { ... }
```

Total: **13 gate assertions**

## Acceptance Criteria

✅ All 13 assertions passing
✅ All 62 M3.8.1 optimizer tests passing
✅ All 5 M3.8.2 ingest tests passing
✅ All 7 M3.8.3 metrics tests passing
✅ All 16 M3.8.5 benchmark tests passing
✅ All 11 existing prompt tests passing
✅ No regressions in other modules
✅ Documentation complete

## Success Criteria

- **Safety**: 6/6 assertions ✅
- **Performance**: 4/4 assertions ✅
- **Quality**: 3/3 assertions ✅
- **Coverage**: 100% of compressors tested
- **Documentation**: BENCHMARKS.md + GATE.md

## Timeline

- M3.8.1: ✅ Done (62 tests)
- M3.8.2: ✅ Done (5 tests)
- M3.8.3: ✅ Done (7 tests)
- M3.8.4: ✅ Done (implicit, 0 tests)
- M3.8.5: ⏳ In progress (16 tests)
- M3.8.6: ⏳ Next (13 tests)

**Total M3.8**: 103 tests
**Expected gate pass rate**: 100%