Claude Fable 5.1 vs Kimi K3 256K
Claude Fable 5.1 leads overall, B- to D+. Claude Fable 5.1 is about 1.5x cheaper per task. By suite, Claude Fable 5.1 takes real-world issues (B+ to C-) and spec planning (C+ to C-). Take Kimi K3 256K anyway when you want the side that is 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: Kimi K3 256K vs Claude Fable 5.1
Claude Fable 5.1 leads overall, B- to D+. By suite: Claude Fable 5.1 takes real-world issues, B+ to C- (87% vs 60% capability); Claude Fable 5.1 takes spec planning, C+ to C- (71% vs 56% capability); Claude Fable 5.1 takes vibe coding, C+ to F (74% vs 34% capability). Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price. Per task, Claude Fable 5.1 is about 1.5x cheaper ($0.097 vs $0.146). Kimi K3 256K is faster on real-world issues: a median task takes 3m 31s against 3m 38s. Both finished every task on it. Reasons to pick Kimi K3 256K anyway: it is faster on real-world issues (3m 31s 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; Kimi K3 256K: real-world issues usage 23% to 21% of the weekly limit, spec planning D+ to C-, spec planning usage 11% to 10% of the weekly limit, vibe coding usage 3% to 2.6% of the weekly limit.
| Dimension | Claude Fable 5.1 | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 87% | 60% | +27% (Claude Fable 5.1 leads) |
| Median task time | 3m 38s | 3m 31s | 6s faster (Kimi K3 256K leads) |
| Approx. task cost | $0.077 / task | $0.126 / task | $0.049 / task lower (Claude Fable 5.1 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. Kimi K3 256K: 104.0% of Kimi Allegretto (104.0% / 5h, 21.0% / 1w) per run. Its weekly limit holds about 5 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 Kimi K3 256K 140 suite runs per month (Claude Fable 5.1 leads); per plan-dollar: 2.28 vs 3.60 (Kimi K3 256K leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 71% | 56% | +15% (Claude Fable 5.1 leads) |
| Median task time | 8m 55s | 5m 26s | 3m 29s faster (Kimi K3 256K leads) |
| Approx. task cost | $0.172 / task | $0.224 / task | $0.052 / task lower (Claude Fable 5.1 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. Kimi K3 256K: 52.0% of Kimi Allegretto (52.0% / 5h, 10.0% / 1w) per run. Its weekly limit holds about 5 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 Kimi K3 256K 281 suite runs per month (Claude Fable 5.1 leads); per plan-dollar: 4.43 vs 7.20 (Kimi K3 256K leads). Work figures compare outputs, so unlike quota shares they are comparable across plans.
| Dimension | Claude Fable 5.1 | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 74% | 34% | +40% (Claude Fable 5.1 leads) |
| Median task time | 4m 14s | 7m 33s | 3m 19s faster (Claude Fable 5.1 leads) |
| Approx. task cost | $0.092 / task | $0.233 / task | $0.141 / task lower (Claude Fable 5.1 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. Kimi K3 256K: 13.2% of Kimi Allegretto (13.2% / 5h, 2.6% / 1w) per good solve. Its weekly limit holds about 5 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 Kimi K3 256K 1107 good solves per month (Claude Fable 5.1 leads); per plan-dollar: 34.79 vs 28.38 (Claude Fable 5.1 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 Kimi K3 256K?
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 Kimi K3 256K?
Claude Fable 5.1 used 8% of Claude Max 5x's weekly limit per pass, $0.097 per task at the listed price. Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price. Per task, Claude Fable 5.1 is about 1.5x cheaper ($0.097 vs $0.146).
Which gives more coding work per dollar, Claude Fable 5.1 or Kimi K3 256K?
Kimi K3 256K delivers more benchmark work per subscription dollar: 3.60 suite runs per plan-dollar versus 2.28 for Claude Fable 5.1 (at $39/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 Kimi K3 256K cost a month?
Claude Fable 5.1 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). Kimi K3 256K runs on Kimi Allegretto at $39/month (public price as of 2026-07-20).