# M3.8.4 — M3.8 Composition Gate

| Field | Value |
|---|---|
| Phase | M3.8 — Context optimization |
| Size | M — 1 day |
| Status | ⬜ Not started |
| Depends | M3.8.3 (benchmarks) |
| Blocks | M3.9 |

## Goal

Verify M3.8 implementation meets safety and performance constraints across
realistic failure scenarios.

## Gate Assertions

### Safety (6 assertions)
1. **No data loss** — CCR store retrieves 100% of compressed content
2. **Cache correctness** — Drift metric accurate (< 5% error vs. actual)
3. **Compression lossless** — Decompressed == original (where applicable)
4. **Format stability** — JSON/diff/log structures preserved
5. **Error graceful** — Optimizer failure doesn't crash pipeline
6. **Thread-safe** — Concurrent optimizations don't corrupt state

### Performance (4 assertions)
1. **Latency** — Per-chunk optimization < 3ms (p99)
2. **Cache hit rate** — Stable prefix unchanged >= 70% across queries
3. **Throughput** — 1000 chunks/sec sustained
4. **Memory** — Cache size stays < 100MB (max 1000 entries @ 100KB each)

### Quality (3 assertions)
1. **Compression met** — All 4 content types meet targets
2. **No false positives** — Cache eligible when drift < 0.3
3. **Coverage** — Benchmarks > 95% compression code paths

## Test Implementation

File: `tests/it_m3_8_gate.rs` (200 LOC)

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

#[test]
fn m3_8_gate_cache_correctness() { ... }

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

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

#[test]
fn m3_8_gate_concurrent_safety() { ... }

#[test]
fn m3_8_gate_cache_hit_rate() { ... }
```

Tests: 6 (safety) + 4 (performance) + 3 (quality) = 13 total

## Acceptance

✅ All 13 gate assertions passing
✅ 117+ optimizer unit tests passing
✅ Benchmarks meeting compression targets
✅ No regressions in other modules (prompt, query, etc.)
✅ Documentation complete (CONTEXT_OPTIMIZER.md, headers in code)

## Success Criteria

- M3.8.4 gate 100% pass rate
- Zero blocking issues from integration tests
- Ready for M3.8 → production hand-off