Model comparison
Claude Fable 5 vs Claude Fable 5.1
Two Anthropic tiers compared on the figures that decide which one a workload actually needs.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
Anthropic
Claude Fable 5
Frontier
Anthropic
Claude Fable 5.1
Frontier
| Specification | Claude Fable 5 | Claude Fable 5.1 |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Tier | Frontier | Frontier |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
| Input / 1M tokens | $10 | $10 |
| Output / 1M tokens | $50 | $50 |
| Weights | Closed | Closed |
| Parameters | Not disclosedUnverified | Not disclosedUnverified |
| Reasoning levels | adaptive | adaptive |
| Modalities | text, image | text, image |
| API model id | claude-fable-5 | claude-fable-5-1 |
| Released | June 9, 2026 | September 1, 2026 |
| Artificial Analysis Intelligence Index (2026-08-14) | 62 | Winner: 66 |
| Humanity's Last Exam (2026-09-01) | Not verifiedUnverified | 65 |
| Terminal-Bench 2.1 (2026-09-05) | Not verifiedUnverified | 91.4 |
| DeepSWE 1.1 (2026-09-03) | Not verifiedUnverified | 67.4 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-09-05: Artificial Analysis Terminal-Bench v2.1 (independent, Terminus 2, max effort — current AA leader)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-09-03: OpenAI GPT-6 Astra launch chart (independent cross-vendor; Fable 5.1 not on the official Datacurve leaderboard)Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task. Comparability: directly comparable
- 2026-09-01: Anthropic announcement comparison table (vendor, with tools; 60.9 no tools)Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise. Comparability: comparable with caveat — Subset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
Pricing tiers: Claude Fable 5: Standard $10/$50 per MTok; cache reads 10% of base input. Sibling Claude Mythos 5 is invite-only cyber-defense. Access briefly suspended 2026-06-12, redeployed 2026-07-01. · Claude Fable 5.1: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day.
Claude Fable 5
Claude Fable 5 is Anthropic's next-generation intelligence model for long-running agents, topped LiveBench until the 5.1 refresh.
Best for
- Long-running agents
- Frontier reasoning
- Enterprise work
Watch out
Most expensive Anthropic tier at $10/$50; verify the cost is justified by the task.
Claude Fable 5.1
Claude Fable 5.1 is Anthropic's September 2026 flagship refresh, debuting at the top of LiveBench and the Artificial Analysis Intelligence Index.
Best for
- Frontier agents
- Hardest reasoning work
- Fable 5 workloads at the same price
Watch out
Early-life model: leaderboard position is from launch-week boards; recheck before committing spend.
When the cheaper one wins
Both charge $50 per million output tokens at standard rates, so output price is not the split. Prefer the row whose “best for” line matches the job, then confirm the live vendor rate.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- Claude Fable 5: Anthropic — Claude Fable 5 (accessed 2026-08-29)
- Claude Fable 5: Anthropic news — Claude Fable 5 (accessed 2026-08-29)
- Claude Fable 5.1: Anthropic pricing — Fable 5.1/Mythos 5.1 $10/$50 (accessed 2026-09-03)
- Claude Fable 5.1: Anthropic models overview — Fable 5.1 (1M context, 128K output) (accessed 2026-09-03)
- Claude Fable 5.1: Artificial Analysis — Fable 5.1 Intelligence Index 66 #1 (accessed 2026-09-01)
Related comparisons
- Claude Fable 5.1 vs Claude Haiku 4.5
- Claude Fable 5.1 vs Claude Mythos 5.1
- Claude Fable 5.1 vs Claude Opus 5
- Claude Fable 5.1 vs Claude Sonnet 5
- Claude Fable 5.1 vs DeepSeek V4 Pro
- Claude Fable 5.1 vs Gemini 3.1 Pro
Diving deeper on one model? Claude Fable 5 · Claude Fable 5.1
Common questions
Claude Fable 5 vs Claude Fable 5.1
Answered from the verified figures on this page rather than general guidance.
Is Claude Fable 5 or Claude Fable 5.1 cheaper for input?
Both cost $10 per million input tokens at standard rates, so input price is not a deciding factor between them.
Is Claude Fable 5 or Claude Fable 5.1 cheaper for output?
Both cost $50 per million output tokens at standard rates, so output price is not a deciding factor between them.
Which has the larger context window, Claude Fable 5 or Claude Fable 5.1?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Fable 5 and Claude Fable 5.1 support the same reasoning levels?
Yes — both accept the same effort settings: "adaptive". Higher effort costs more and takes longer, so start low and raise it only where output quality actually improves.
Should I use Claude Fable 5 or Claude Fable 5.1?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Fable 5 suits long-running agents; Claude Fable 5.1 suits frontier agents.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
These two models match on every verified catalog figure — the decision comes down to provider preference, availability, and workload fit rather than published numbers.
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.