Claude Fable 5

Language modelPrevious generationCard summarized

A Mythos-class model that we've made safe for general use

Active (legacy) · retires not before 9 Jun 2027● Re-checked 12 Oct 2026 · 105 facts · 0 corrections · 5 unconfirmedSource: System Card: Claude Fable 5 & Claude Mythos 5 (317 pp)

Use it via API

$5,880 /month

$118 per 1K requests

RAG over docs: 12K in · 600 out · 50K requests/mo · 30% cached · change

Code example Compare

Where to call it

Claude APIclaude-fable-5
Amazon Bedrockanthropic.claude-fable-5
Google Vertex AIclaude-fable-5
Microsoft Foundry / Azureclaude-fable-5

Supports

Image input
PDF input
Structured outputs
Reasoning control
Tool calling
Web search
Prompt caching
Batch API

Full feature support

Good for

Software coding: SWE-bench Verified 95%, SWE-bench Pro 80%
Long-context agentic tasks and computer use (OSWorld-Verified 85%)
Vision and document reasoning (state of the art on GDP.pdf and Blueprint-Bench 2 per the card)

Watch out for

Safety classifiers over-trigger
Reckless or destructive agent actions
Weak on multi-turn self-harm conversations without a system prompt

Replaced by

Claude Fable 5.1$10.00 / $50.00

This model: $10.00 / $50.00 per 1M tokens

Compare side by side

Overview

Anthropic · 07Fable

Fable 5

A Mythos-class model that we've made safe for general use

Cost: $10.00 in
Context: 1M

Input / output: $10.00 / $50.00
Max output: 128K
Knows up to: January 2026
Released: 9 Jun 2026

Claude Fable 5 and Claude Mythos 5 are two configurations of the same new Anthropic model. Fable 5 is the general-access version: same weights as Mythos 5, plus classifiers that block high-risk biology, chemistry and cybersecurity use and fall back to Claude Opus 4.8. Mythos 5 is available only to vetted Project Glasswing partners. Fable 5 scores close to Mythos 5 where its classifiers don't trigger and like Opus 4.8 where they do. p.3–4, p.12

claude-fable-5

Input / output per 1M: $10.00 / $50.00
Context window: 1M
Max output: 128K
Knows up to: January 2026
Reasoning: Adaptive (always on)
Weights: Closed

About this card. A model card is the maker's own account of a model: what it's for, how it was trained and tested, and where it falls short. This page condenses Anthropic's System Card: Claude Fable 5 & Claude Mythos 5. Every claim carries its source page.