claude-fable-5 vs gpt-5.6-luna
Each agent graded on the same private suites, running headless through its own tools. Advantages are oriented so a win is a win, whichever way the metric runs.
| Dimension | claude-fable-5 | gpt-5.6-luna | Advantage |
|---|---|---|---|
| Capability | 60% | 53% | +7% (claude-fable-5 leads) |
| Median task time | 3m 12s | 1m 59s | 1m 14s faster (gpt-5.6-luna leads) |
| Approx. task cost | $0.031 / task | $0.009 / task | $0.022 / task lower (gpt-5.6-luna leads) |
claude-fable-5: 34.0% of Claude Max 20x (34.0% / 5h, 5.0% / 1w) per run. gpt-5.6-luna: 2.9% of ChatGPT Plus (2.9% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | claude-fable-5 | gpt-5.6-luna | Advantage |
|---|---|---|---|
| Capability | 64% | 58% | +7% (claude-fable-5 leads) |
| Median task time | 5m 54s | 2m 11s | 3m 43s faster (gpt-5.6-luna leads) |
| Approx. task cost | $0.041 / task | $0.004 / task | $0.037 / task lower (gpt-5.6-luna leads) |
claude-fable-5: 12.0% of Claude Max 20x (12.0% / 5h, 1.0% / 1w) per run. gpt-5.6-luna: 0.3% of ChatGPT Plus (0.3% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | claude-fable-5 | gpt-5.6-luna | Advantage |
|---|---|---|---|
| Capability | 69% | 28% | +41% (claude-fable-5 leads) |
| Median task time | 5m 25s | 2m 44s | 2m 41s faster (gpt-5.6-luna leads) |
| Approx. task cost | $0.038 / task | $0.008 / task | $0.031 / task lower (gpt-5.6-luna leads) |
claude-fable-5: 2.8% of Claude Max 20x (2.8% / 5h, 0.6% / 1w) per good solve. gpt-5.6-luna: 0.2% of ChatGPT Plus (0.2% / 1w) per good solve. Each figure is a share of that agent's own plan, so there is no delta to draw.
Grades and deltas are comparable only within a suite version. See methodology.
Frequently asked questions
Which is better for coding, claude-fable-5 or gpt-5.6-luna?
claude-fable-5 clears higher: tier 4 of 5 versus tier 3 for gpt-5.6-luna on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-08-17.
How much do claude-fable-5 and gpt-5.6-luna cost?
claude-fable-5 runs on Claude Max 20x at $200/month (public price as of 2026-08-05). gpt-5.6-luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).