Claude Fable 5.1 vs Claude Opus 5.5
Both grade B- overall. Claude Opus 5.5 is about 4.0x cheaper per task. By suite, Claude Fable 5.1 takes real-world issues (B+ to C+) and spec planning is even at C+. Both agents run the same private suite cut headless through their own tools, each on its own subscription.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 Opus 5.5 vs Claude Fable 5.1
Both grade B- overall. By suite: Claude Fable 5.1 takes real-world issues, B+ to C+ (87% vs 73% capability); spec planning is even at C+ (71% vs 73% capability); Claude Opus 5.5 takes vibe coding, B+ to C+ (90% vs 74% 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 Opus 5.5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 per task at the listed price. Per task, Claude Opus 5.5 is about 4.0x cheaper ($0.024 vs $0.097). Claude Opus 5.5 is faster on real-world issues: a median task takes 1m 17s against 3m 38s. Both finished every task on it.
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; Claude Opus 5.5: real-world issues C- to C+, vibe coding B to B+.
| Dimension | Claude Fable 5.1 | Claude Opus 5.5 | Advantage |
|---|---|---|---|
| Capability | 87% | 73% | +13% (Claude Fable 5.1 leads) |
| Median task time | 3m 38s | 1m 17s | 2m 21s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.077 / task | $0.015 / task | $0.061 / task lower (Claude Opus 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 Opus 5.5: 11.0% of Claude Max 5x (11.0% / 5h, 1.0% / 1w) 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 Opus 5.5 1328 suite runs per month (Claude Opus 5.5 leads); per plan-dollar: 2.28 vs 13.28 (Claude Opus 5.5 leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Claude Opus 5.5 | Advantage |
|---|---|---|---|
| Capability | 71% | 73% | +2% (Claude Opus 5.5 leads) |
| Median task time | 8m 55s | 4m 17s | 4m 38s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.172 / task | $0.057 / task | $0.115 / task lower (Claude Opus 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 Opus 5.5: 6.0% of Claude Max 5x (6.0% / 5h, 1.0% / 1w) 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 Opus 5.5 2435 suite runs per month (Claude Opus 5.5 leads); per plan-dollar: 4.43 vs 24.35 (Claude Opus 5.5 leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Claude Opus 5.5 | Advantage |
|---|---|---|---|
| Capability | 74% | 90% | +15% (Claude Opus 5.5 leads) |
| Median task time | 4m 14s | 2m 44s | 1m 29s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.092 / task | $0.007 / task | $0.085 / task lower (Claude Opus 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 Opus 5.5: 1.0% of Claude Max 5x (1.0% / 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 Opus 5.5 14610 good solves per month (Claude Opus 5.5 leads); per plan-dollar: 34.79 vs 146.10 (Claude Opus 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 Opus 5.5?
Both clear tier 4 of 5, but Claude Fable 5.1 scores higher on capability: 87% versus 73% 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 Opus 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 Opus 5.5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 per task at the listed price. Per task, Claude Opus 5.5 is about 4.0x cheaper ($0.024 vs $0.097).
Which gives more coding work per dollar, Claude Fable 5.1 or Claude Opus 5.5?
Claude Opus 5.5 delivers more benchmark work per subscription dollar: 13.28 suite runs per plan-dollar versus 2.28 for Claude Fable 5.1 (at $100/month priced 2026-07-27, 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 Opus 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 Opus 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-27).