Claude Fable 5.1 vs Claude Sonnet 5.5
Claude Fable 5.1 leads overall, B- to C-. Claude Sonnet 5.5 is about 34x cheaper per task. By suite, Claude Fable 5.1 takes real-world issues (B+ to C-) and spec planning is even at C+. Take Claude Sonnet 5.5 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: Claude Sonnet 5.5 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 74% capability); Claude Fable 5.1 takes vibe coding, C+ to D+ (74% vs 48% capability). Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. Per task, Claude Sonnet 5.5 is about 34x cheaper ($0.003 vs $0.097). Claude Sonnet 5.5 is faster on real-world issues: a median task takes 37s against 3m 38s. Both finished every task on it. Reasons to pick Claude Sonnet 5.5 anyway: it is cheaper per task ($0.003 vs $0.097) and it is faster on real-world issues (37s vs 3m 38s median).
Changed since W39: 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.
| Dimension | Claude Fable 5.1 | Claude Sonnet 5.5 | Advantage |
|---|---|---|---|
| Capability | 87% | 60% | +27% (Claude Fable 5.1 leads) |
| Median task time | 3m 38s | 37s | 3m 1s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.077 / task | $0.002 / task | $0.075 / task lower (Claude Sonnet 5.5 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. Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
Work per window: Claude Fable 5.1 228 vs Claude Sonnet 5.5 3653 suite runs per month (Claude Sonnet 5.5 leads); per plan-dollar: 2.28 vs 36.52 (Claude Sonnet 5.5 leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Claude Sonnet 5.5 | Advantage |
|---|---|---|---|
| Capability | 71% | 74% | +4% (Claude Sonnet 5.5 leads) |
| Median task time | 8m 55s | 3m 25s | 5m 30s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.172 / task | $0.007 / task | $0.166 / task lower (Claude Sonnet 5.5 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. Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
Work per window: Claude Fable 5.1 443 vs Claude Sonnet 5.5 3653 suite runs per month (Claude Sonnet 5.5 leads); per plan-dollar: 4.43 vs 36.52 (Claude Sonnet 5.5 leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Claude Sonnet 5.5 | Advantage |
|---|---|---|---|
| Capability | 74% | 48% | +26% (Claude Fable 5.1 leads) |
| Median task time | 4m 14s | 56s | 3m 17s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.092 / task | $0.001 / task | $0.091 / task lower (Claude Sonnet 5.5 leads) |
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. Claude Sonnet 5.5: 0.2% of Claude Max 5x (0.2% / 5h) per good solve. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
Work per window: Claude Fable 5.1 3479 vs Claude Sonnet 5.5 73050 good solves per month (Claude Sonnet 5.5 leads); per plan-dollar: 34.79 vs 730.50 (Claude Sonnet 5.5 leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
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 Claude Sonnet 5.5?
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 Claude Sonnet 5.5?
Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. Per task, Claude Sonnet 5.5 is about 34x cheaper ($0.003 vs $0.097).
Which gives more coding work per dollar, Claude Fable 5.1 or Claude Sonnet 5.5?
Claude Sonnet 5.5 delivers more benchmark work per subscription dollar: 36.52 suite runs per plan-dollar versus 2.28 for Claude Fable 5.1 (at $100/month priced 2026-07-20, and $100/month priced 2026-07-27). Work figures compare outputs, so unlike raw quota shares they are comparable across plans.
What do Claude Fable 5.1 and Claude Sonnet 5.5 cost a month?
Claude Fable 5.1 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). Claude Sonnet 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-20).