Claude Fable 5.1: model ids, price and cutoff

How to call it

7 ways to use Claude Fable 5.1, with the model id each provider expects.

Providers, model ids, endpoints and docs for Claude Fable 5.1
Provider	Model id	Endpoint	Docs
Anthropic API (Claude API)	`claude-fable-5-1`	`https://api.anthropic.com/v1/messages`	platform.claude.com
AWS Bedrock (Messages API / Mantle)	`anthropic.claude-fable-5-1`		platform.claude.com
Google Cloud Vertex AI	`claude-fable-5-1`		platform.claude.com
Microsoft Foundry (Azure)	`claude-fable-5-1`		platform.claude.com
Claude Platform on AWS	`claude-fable-5-1`		platform.claude.com
OpenRouter	`anthropic/claude-fable-5.1`		openrouter.ai
Web app			claude.ai

Pricing

Prices for Claude Fable 5.1
Input	$10 per 1M tokens
Output	$50 per 1M tokens
Cache read	$0.25 per 1M tokens

As published: “per 1M tokens (USD); Batch API 50% off”.

Source: platform.claude.com, checked 9 November 2026.

Specs

Input: Text, images and PDF
Output: Text
Context window: 1,000,000 tokens
Max output: 128,000 tokens
Open weights: No
Licence: Proprietary
Training cutoff: June 2026
Released: 1 September 2026
Status: Current
Type: Reasoning model

What stands out

What its maker marketed at launch, and what people found later, each with its source.

Scientific discovery (protein design)

In Anthropic’s launch examples, its protein designs reached about 10x higher binding affinity than competition winners, with a hit rate near 50%.

Source: anthropic.com
Rare-bug hunting

Anthropic reports it found the cause of a one-in-a-million crash that engineers had not explained for years.

Source: anthropic.com
Top CursorBench score

Scored 73.4% on CursorBench 3.2.0 at max effort, which Cursor called the most capable model it had run.

Source: anthropic.com
Preserved thinking and content provenance

First

Thinking blocks are bound to the model and the conversation, and editing earlier turns invalidates them. Also adds per-message effort, turn-scoped system messages and content provenance.

Source: platform.claude.com
Cheaper cache reads

Cache reads cost $0.25/MTok (0.025x input). Anthropic cites up to 45% savings on agentic work compared with Fable 5.

Source: platform.claude.com

Four assistants, one scale

Claude Fable 5.1 is added as a fifth row. Each row runs from what the model knows (graphite) through the months between its cutoff and its launch (hatched) to today (pink).

GPT-6 Astra 271 at launch, 1,863 today
Claude Opus 5.5 372 at launch, 1,795 today
Gemini 4 Hydrogen 1,863 at launch, 1,889 today
Grok 4.7 387 at launch, 1,829 today
Claude Fable 5.1 191 at launch, 1,795 today

Show as a table

Model	Cutoff	Released	Missing at launch	Missing today
GPT-6 Astra	April 2026	3 September 2026	271	1,863
Claude Opus 5.5	June 2026	22 September 2026	372	1,795
Gemini 4 Hydrogen	March 2026	12 November 2026	1,863	1,889
Grok 4.7	May 2026	21 September 2026	387	1,829
Claude Fable 5.1	June 2026	1 September 2026	191	1,795

Notes

Superseded on 2026-11-09 by Claude Fable 5.2 ($8/$40, same API family; see claude-fable-5-2). Anthropic’s most capable widely released model; thinking always on (adaptive, effort low..max, default high); forced tool_choice any/tool returns 400; no prefill; 30-day data retention required (no ZDR unless authorized); no Priority Tier. Batch $5/$25.

curl https://api.anthropic.com/v1/messages \
 -H "x-api-key: $ANTHROPIC_API_KEY" -H "anthropic-version: 2023-06-01" -H "content-type: application/json" \
 -d '{"model":"claude-fable-5-1","max_tokens":16000,"messages":[{"role":"user","content":"Hello"}]}'

Sources: