Updated
Best AI coding models, September 2026 edition
As of Sep 26, 2026, GPT-5.5 had the lowest relative bug rate on Bug Bench (0.47, 53% fewer counted bugs than average), among 9 ranked AI coding models. Updates daily until Sep 30.
| Rank | Model | Rate |
|---|---|---|
| 1 | GPT-5.5 | 0.47 |
| 2= (statistically tied) | Claude Fable 5 | 0.70 |
| 3= (statistically tied) | GPT-5.6 Sol | 0.73 |
| 4 | Claude Opus 4.8 | 0.88 |
| 5= (statistically tied) | GPT-6 Astra | 1.16 |
| 6= (statistically tied) | Claude Fable 5.1 | 1.17 |
| 7= (statistically tied) | GPT-5.6 Luna | 1.28 |
| 8 | Claude Opus 5 | 1.58 |
| 9 | Claude Sonnet 5 | 2.10 |
1.00 = average · lower is better · = statistically tied
Most-used models and coding agents
Share of AI-written code, week of Sep 14
Models
- Claude Opus 5
- 38.3%
- GPT-6 Astra
- 19.6%
- Claude Fable 5.1
- 19.4%
- GPT-5.6 Sol
- 7.2%
- Claude Sonnet 5
- 4.0%
Coding agents
- Claude Code
- 65.6%
- Codex
- 28.4%
- Cursor
- 3.2%