# Final API Alignment Audit

## Implementation Completeness

### Phases Complete (Implementation)

| Phase | Description | Status |
|---|---|---|
| 1 | Project Scaffolding | Complete |
| 2 | Anthropic Domain Types | Complete (30+ tests) |
| 3 | OpenAI Domain Types | Complete (25+ tests) |
| 4 | Non-Streaming Message Translation | Complete (40+ tests) |
| 5 | Tool Calling Translation | Complete (15+ tests) |
| 6 | Proxy Server and Routing | Complete (6+ integration tests) |
| 7 | Streaming SSE Translation | Complete (20+ tests) |
| 8 | Files and Document Blocks | Complete (text note fallback) |
| 9 | Compatibility Endpoints | Complete (5 integration tests) |
| 10 | Hardening, Security, Observability | Complete |
| 11 | End-to-End Validation | Complete (golden fixtures) |

### Test Coverage Summary

- **169 total tests**
- Translator crate: 135 unit tests + 7 golden fixture tests
- Proxy crate: 21 unit tests + 6 integration tests
- All tests passing, zero clippy warnings, format clean

### API Alignment vs PLAN.md

| PLAN.md Requirement | Implementation | Alignment |
|---|---|---|
| POST /v1/messages (non-streaming) | Implemented | Full |
| POST /v1/messages (streaming) | Implemented | Full |
| GET /v1/models | Implemented (static) | Partial (no OpenAI proxy) |
| POST /v1/messages/count_tokens | Returns unsupported error | Declared |
| POST /v1/messages/batches | Returns unsupported error | Declared |
| Tool calling translation | Implemented | Full |
| Streaming state machine | Implemented | Full |
| Error shape translation | Implemented | Full |
| Retry/backoff | Implemented | Full |
| Auth middleware | Implemented | Partial (presence only) |
| Size limits | Implemented (32MB) | Full |
| Concurrency limits | Implemented (100) | Full |

### Architecture Alignment

The implementation follows PLAN.md's recommended architecture:
- Two-crate workspace (translator lib + proxy bin)
- Pure translation functions (no IO in translator crate)
- Typed domain structs with serde flatten for forward compatibility
- Stateless tool call ID bridge
- SSE state machine for streaming translation
- Bounded channel backpressure for streaming

### Deviation Log

| Aspect | PLAN.md Recommendation | Actual | Reason |
|---|---|---|---|
| Backend API | Responses preferred, Chat Completions fallback | Chat Completions only | Simpler; stop mapping is cleaner |
| Canonical IR | CanonicalChatRequest intermediate | Direct A->B mapping | Simpler for single backend target |
| Document blocks | Convert to input_file.file_data | Text note fallback | Chat Completions lacks inline PDF |
| Auth | Multi-tenant key mapping | Presence check only | Production hardening deferred |