## Summary
Investigated OpenAI's new GPT-5-Codex model and Codex GitHub PR review integration capabilities.
## GPT-5-Codex Analysis
### Benchmark Performance (Good)
- SWE-bench Verified: 74.5% (vs GPT-5's 72.8%)
- Refactoring tasks: 51.3% (vs GPT-5's 33.9%)
- Code review: Higher developer ratings
### Real-World Issues (Concerning)
- Users report degraded coding performance
- Scripts that previously worked now fail
- Less consistent than GPT-4.5
- Longer response times (minutes vs instant)
- "Creatively and emotionally flat"
- Basic errors (e.g., counting letters incorrectly)
### Key Finding
Classic case of "optimizing for benchmarks vs real usability" - scores well on tests but performs poorly in practice.
## Codex GitHub PR Integration
### Setup Process
1. Enable MFA and connect GitHub account
2. Authorize Codex GitHub app for repos
3. Enable "Code review" in repository settings
### Usage Methods
- **Manual**: Comment '@codex review' in PR
- **Automatic**: Triggers when PR moves from draft to ready
### Current Limitations
- One-way communication (doesn't respond to review comments)
- Prefers creating new PRs over updating existing ones
- Better for single-pass reviews than iterative feedback
## 'codex resume' Feature
New session management capability:
- Resume previous codex exec sessions
- Useful for continuing long tasks across days
- Maintains context from interrupted work
🐱 The investigation reveals that while GPT-5-Codex shows benchmark improvements, practical developer experience has declined - a reminder that metrics don't always reflect real-world utility\!
PHI type coercion and core-first routing fixes:
- Auto type conversion for PHI nodes (i64↔i8*↔i1↔f64)
- Fixed ArrayBox.get misrouting to Map path
- Core-first strategy for Array/Map creation
- Added comprehensive debug logging ([PHI], [ARR], [MAP])
Results:
✅ Array smoke test: 'Result: 3'
✅ Map smoke test: 'Map: v=42, size=1'
After 34+ minutes of battling Rust lifetime errors,
ChatGPT5 achieved a major breakthrough\!
Key insight: The bug wasn't in PHI/SSA logic but in
Box type routing - ArrayBox.get was incorrectly caught
by Map fallback due to missing annotations.
We're SO CLOSE to Nyash self-hosting paradise\! 🌟
Once this stabilizes, everything can be written in
simple, beautiful Nyash code instead of Rust complexity.
