Claude Fable 5.1 vs GPT-5.6 Sol
GPT-5.6 Sol was superseded by GPT-6.1 Sol. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
Claude Fable 5.1 leads overall, B- to C-. GPT-5.6 Sol is about 2.7x cheaper per task. By suite, Claude Fable 5.1 takes real-world issues (B+ to C-) and spec planning is even at C+. Take GPT-5.6 Sol anyway when you want the side that is cheaper per task and faster on real-world issues.Measured
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.
Verdict: GPT-5.6 Sol vs Claude Fable 5.1
Claude Fable 5.1 leads overall, B- to C-. By suite: Claude Fable 5.1 takes real-world issues, B+ to C- (87% vs 60% capability); spec planning is even at C+ (71% vs 68% capability); Claude Fable 5.1 takes vibe coding, C+ to D+ (74% vs 51% capability). Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Per task, GPT-5.6 Sol is about 2.7x cheaper ($0.036 vs $0.097). GPT-5.6 Sol is faster on real-world issues: a median task takes 3m 13s against 3m 38s. Both finished every task on it. Reasons to pick GPT-5.6 Sol anyway: it is cheaper per task ($0.036 vs $0.097) and it is faster on real-world issues (3m 13s vs 3m 38s median).
Changed since the previous graded week: Claude Fable 5.1: real-world issues D+ to B+, real-world issues usage 7% to 5% of the weekly limit, spec planning usage 4% to 3% of the weekly limit, vibe coding C- to C+, vibe coding usage 0.6% to 0.4% of the weekly limit; GPT-5.6 Sol: vibe coding C- to D+.
| Dimension | Claude Fable 5.1 | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 87% | 60% | +27% (Claude Fable 5.1 leads) |
| Median task time | 3m 38s | 3m 13s | 25s faster (GPT-5.6 Sol leads) |
| Approx. task cost | $0.077 / task | $0.031 / task | $0.046 / task lower (GPT-5.6 Sol leads) |
Claude Fable 5.1: 64.0% of Claude Max 5x (64.0% / 5h, 5.0% / 1w) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-5.6 Sol: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Fable 5.1 | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 71% | 68% | +2% (Claude Fable 5.1 leads) |
| Median task time | 8m 55s | 6m 0s | 2m 55s faster (GPT-5.6 Sol leads) |
| Approx. task cost | $0.172 / task | $0.057 / task | $0.115 / task lower (GPT-5.6 Sol leads) |
Claude Fable 5.1: 33.0% of Claude Max 5x (33.0% / 5h, 3.0% / 1w) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-5.6 Sol: 1.0% of ChatGPT Pro 5x (1.0% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Fable 5.1 | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 74% | 51% | +23% (Claude Fable 5.1 leads) |
| Median task time | 4m 14s | 3m 56s | 17s faster (GPT-5.6 Sol leads) |
| Approx. task cost | $0.092 / task | $0.092 / task | Even |
Claude Fable 5.1: 4.2% of Claude Max 5x (4.2% / 5h, 0.4% / 1w) per good solve. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-5.6 Sol: 0.4% of ChatGPT Pro 5x (0.4% / 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 5.1 or GPT-5.6 Sol?
Both clear tier 4 of 5, but Claude Fable 5.1 scores higher on capability: 87% versus 60% on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-27.
Which is cheaper per task, Claude Fable 5.1 or GPT-5.6 Sol?
Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Per task, GPT-5.6 Sol is about 2.7x cheaper ($0.036 vs $0.097).
What do Claude Fable 5.1 and GPT-5.6 Sol cost a month?
Claude Fable 5.1 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). GPT-5.6 Sol runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05).