Compare AI Models Side by Side

Pick 2 to 4 models to compare benchmark scores, pricing, and specs in 2026.

Claude Fable 5.1
Claude Mythos 5.1
Anthropic
Claude Fable 5.1

Anthropic · Claude

Anthropic
Claude Mythos 5.1

Anthropic · Claude

Specifications

Spec
Claude Fable 5.1
Claude Mythos 5.1
ProviderAnthropicAnthropic
FamilyClaudeClaude
Release date2026-09-012026-09-01
Open sourceNoNo
Context window1.0M tokens1.0M tokens
Max output128K tokens128K tokens
Input price / MTok$10.00*$10.00*
Output price / MTok$50.00*$50.00*
Best forcoding, agents, reasoning, researchcoding, agents, reasoning, research

* Claude Fable 5.1: Cache reads cut to $0.25/MTok, a 75% reduction from Fable 5's $1.00/MTok. 5-minute cache writes $12.50/MTok, 1-hour cache writes $20/MTok. Batch API is 50% off. Anthropic reports this brings typical-workload cost down about 25% and highly agentic workload cost down up to about 45% versus Fable 5 at the same prices. | Claude Mythos 5.1: Identical pricing to Claude Fable 5.1: cache reads $0.25/MTok (2.5% of base input), 5-minute cache writes $12.50/MTok, 1-hour cache writes $20/MTok, Batch API 50% off.

Benchmark scores (% of max)

Scores normalized to percentage of each benchmark's maximum reported value. Only officially reported scores are included.

Cost per million tokens (USD)

Context window (thousands of tokens)

Notes

Claude Fable 5.1: Released Sep 1 2026 alongside Claude Mythos 5.1 (same underlying model, restricted-access safeguards for vetted cybersecurity/life-sciences organizations via Anthropic's Cyber and Life Sciences Verification Programs). Anthropic recommends it over Opus 5 for demanding reasoning and long-horizon agentic work, or when Opus 5 at higher effort still falls short. Anthropic's own comparison shows it beating Fable 5 and Opus 5 on every benchmark listed above except Terminal-Bench 4.0, where sibling model Mythos 5.1 (not Fable 5.1) posts the top score. API identifier claude-fable-5-1, reliable knowledge cutoff June 2026, retirement not sooner than Sep 1 2027.
Claude Mythos 5.1: Same underlying model as Claude Fable 5.1 (identical 1M context, 128K max output, adaptive-always-on thinking, default effort high, Jun 2026 knowledge cutoff, and pricing) but offered separately, by invitation only, as part of Anthropic's Project Glasswing — request access via an Anthropic, AWS, or Google Cloud account team, not available as a general API model. Beats sibling Fable 5.1 on Terminal-Bench 4.0 specifically; the two are otherwise presented as equivalent. Model ID claude-mythos-5-1 (anthropic.claude-mythos-5-1 on Bedrock), retirement not sooner than Sep 1 2027. Source: https://platform.claude.com/docs/en/models/mythos-5-1/overview
Back to all models

Related

Deciding which model to build on for a real product? Book a free consultation and we'll help you pick the right one for your workload and budget.

Claude Fable 5.1 vs Claude Mythos 5.1 | AI Model Comparison