Updated
Claude Fable 5.1
As of Sep 26, 2026, Claude Fable 5.1 ranks #4 of 7 on Bug Bench with a relative bug rate of 1.17 (17% more counted bugs than average), statistically tied with GPT-6 Astra and GPT-5.6 Luna.
- Relative bug rate
- 1.17
- Rank of 7
- #4
- Tied with
- GPT-6 Astra and GPT-5.6 Luna
1.00 = average · lower is better
- First seen
- Week of Aug 31
Nearby in the ranking
| Rank | Model | Rate |
|---|---|---|
| 2 | Claude Opus 4.8 | 0.88 |
| 3= (statistically tied) | GPT-6 Astra | 1.16 |
| 4 | Claude Fable 5.1 | 1.17 |
| 5= (statistically tied) | GPT-5.6 Luna | 1.28 |
| 6 | Claude Opus 5 | 1.58 |
Is Claude Fable 5.1 getting worse?
Not enough weekly data yet (0 of 6 weeks).
Where it does better or worse
# = rank among models
By coding agent
| Rank | Agent | Rate |
|---|---|---|
| 2 | Claude Code | 1.17 |
How widely Claude Fable 5.1 is used
Share of AI-written code reviewed by cubic
- Latest weekWeek of Sep 14
- 19.4%
- This week so farSince Sep 21
- 13.6%
- Peak weekWeek of Sep 7
- 22.2%
Compare Claude Fable 5.1
Questions and answers
- Is Claude Fable 5.1 good for coding?
- Claude Fable 5.1 ranks #4 of 7 on Bug Bench, with 17% more counted bugs than average (1.17) from Jun 1 to Sep 20, 2026.
- Is Claude Fable 5.1 getting worse?
- Not enough weekly data yet (0 of 6 weeks).
- Which coding agent has the lowest bug rate with Claude Fable 5.1?
- Claude Code, at 1.17.
Embed Claude Fable 5.1's Bug Bench badge
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