Anthropic
Claude Fable 5.1
Claude Fable 5.1 is a Anthropic model with 1M context, $10 in / $50 out per million tokens, last verified September 3, 2026. Open weights: no. Public-board scores are linked to the publisher; vendor-only figures stay in the watch-out, not on the board.
Claude Fable 5.1 is Anthropic's September 2026 flagship refresh, debuting at the top of LiveBench and the Artificial Analysis Intelligence Index.
Catalog record checked September 3, 2026Individual provider fields may change
| Specification | Claude Fable 5.1 |
|---|---|
| Provider | Anthropic |
| Tier | Frontier |
| Context window | 1M |
| Max output | 128K |
| Input / 1M tokens | $10 |
| Output / 1M tokens | $50 |
| Weights | Closed |
| Parameters | Not disclosed |
| Reasoning levels | adaptive |
| Modalities | text, image |
| API model id | claude-fable-5-1 |
| Released | September 1, 2026 |
Pricing tiers: 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.
Verified evidence
Published benchmark results
Each result keeps its source and measurement date visible. A missing benchmark is not treated as a zero.
| Benchmark | Score | Measured | Source |
|---|---|---|---|
| Artificial Analysis Intelligence Index | 66 | 2026-08-14 | Artificial Analysis · View source |
| Humanity's Last Exam | 65 | 2026-09-01 | Anthropic announcement comparison table (vendor, with tools; 60.9 no tools) · View source |
| Terminal-Bench 2.1 | 91.4 | 2026-09-05 | Artificial Analysis Terminal-Bench v2.1 (independent, Terminus 2, max effort — current AA leader) · View source |
| DeepSWE 1.1 | 67.4 | 2026-09-03 | OpenAI GPT-6 Astra launch chart (independent cross-vendor; Fable 5.1 not on the official Datacurve leaderboard) · View source |
Best for
- Frontier agents
- Hardest reasoning work
- Fable 5 workloads at the same price
Watch out
History
Claude Fable 5.1 timeline
Release and status events for this model that passed two-source verification — dated, sourced, and linked.
- Claude Fable 5.1 + Mythos 5.1ReleaseSeptember 1, 2026
Anthropic refreshes its flagship: Fable 5.1 debuts #1 on LiveBench (83.4, Max Effort) and the Artificial Analysis Intelligence Index (66) at unchanged $10/$50 pricing; Mythos 5.1 arrives alongside.
Anthropic pricing/models (LiveBench + Artificial Analysis cross-checked)
Source receipts
Catalog figures for this model were checked against the following sources.
- Anthropic pricing — Fable 5.1/Mythos 5.1 $10/$50 (accessed 2026-09-03)
- Anthropic models overview — Fable 5.1 (1M context, 128K output) (accessed 2026-09-03)
- Artificial Analysis — Fable 5.1 Intelligence Index 66 #1 (accessed 2026-09-01)
Common questions
Claude Fable 5.1
Answered from the verified figures on this page rather than general guidance.
How much does Claude Fable 5.1 cost per million tokens?
Claude Fable 5.1 is listed at $10 per million input tokens and $50 per million output tokens at standard rates. Output tokens usually dominate real bills, so weigh the output rate more heavily than the input rate. 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.
What is Claude Fable 5.1's context window?
Claude Fable 5.1 accepts about 1M tokens of context. That only matters if you routinely send very long documents, large codebases, or multi-turn histories that approach that limit.
What is Claude Fable 5.1 best for?
Claude Fable 5.1 is a frontier tier from Anthropic. It suits frontier agents, hardest reasoning work, fable 5 workloads at the same price. Early-life model: leaderboard position is from launch-week boards; recheck before committing spend.