Claude Fable 5 vs Claude Fable 5.1
EBR Bench?
Fable 539.5
Fable 5.1at max57.1
Harvey LAB-AA 1.1?
Fable 5—
Fable 5.1at max6.4
SpireClimb?
Fable 5—
Fable 5.1at max2
SpireClimb StS1 A20 Heart?
Fable 5—
Fable 5.1at max0
SpireClimb StS2 A10?
Fable 5—
Fable 5.1at max4
| Benchmark | Fable 5 | Fable 5.1 |
|---|---|---|
| AutomationBench-AA | 54.1 | 54.7 |
| GDPval-AA (work tasks) 2.1 | 1,609.9 | 1,554.7 |
| τ³-Banking · AA | 38.1 | 41 |
| AA Analyst Agent | 48.8 | 57.5 · max |
| Terminal-Bench 4.0 | 42.4 | 44.9 |
| AA-Briefcase 1.1 · Elo | 1,536.9 | 1,524 |
| AA-LCR (long context) 1.1 | 82.3 | 84.7 |
| EBR Bench | 39.5 | 57.1 · max |
| Furniture Assembly | 35.8 | 70 · max |
| τ³-bench · banking · 1.0.1 | 39.7 | — |
| ITBench SRE | — | 49.5 · max |
| Terminal-Bench Hard (version unstated) | 62.9 | — |
| Terminal-Bench Science 0.1 | — | 43.3 · max |
| DeepSWE 1.1 | 69.7 | — |
| EnterpriseOps-Gym-AA | 51.1 | — |
| FrontierCode 1.1 | — | 49 · max |
| Harvey LAB-AA 1.1 | — | 6.4 · max |
| SWE-bench Pro (v2 full) | — | 99.1 · high |
| SWE-bench Pro (v2 hard) | — | 92.2 · high |
| SpireClimb | — | 2 · max |
| SpireClimb StS1 A20 Heart | — | 0 · max |
| SpireClimb StS2 A10 | — | 4 · max |
Specs
| Spec | Fable 5 | Fable 5.1 |
|---|---|---|
| Input, per 1M | $10 | $10 |
| Output, per 1M | $50 | $50 |
| Cost per task? | $8.75 | $2.98 |
| Speed, tok/s | 67 | 56 |
| Context | 1M | 1M |
| Weights | Closed | Closed |
| Released | Jun 2026 | Sep 2026 |
| See images | ✓ | ✓ |
| Read PDFs | Partial | Partial |
| Hear audio | — | — |
| Watch video | — | — |
| Call tools | ✓ | ✓ |
| Force a tool call | Partial | Partial |
| Return strict JSON | ✓ | ✓ |
| Search the web | ? | ? |
| Run code | ? | ? |
| Use a computer | ? | ? |
What breaks when you switch
Fable 5 → Fable 5.1
Replace forced tool_choice›
Forced tool_choice returns HTTP 400; use auto with an explicit instruction and strict tools, or JSON outputs.
Adaptive thinking is always on›
Disabled thinking or manual budget_tokens returns HTTP 400; omit thinking or use adaptive thinking.
No non-default sampling values›
Non-default temperature, top_p or top_k returns HTTP 400; omit non-default sampling values.
Requires 30-day data retention · Claude API›
A Claude API organization or workspace without 30-day retention receives HTTP 400; configure workspace retention or contact the Anthropic account team.
Thinking blocks bind to conversations›
Where conversation binding is enforced, replaying an invalidated block returns HTTP 400; use the documented drop_block control to continue without it.
No assistant prefill›
Assistant prefill returns HTTP 400; use system prompt instructions instead.
Fable 5.1 → Fable 5
Nothing known.