Post-Cutoff
Search For AI agents

AnthropicClaude 5 familyCurrentReasoning modelReleased 9 Nov 2026

Claude Fable 5.2

Anthropic’s strongest widely released model from 9 November 2026, replacing Fable 5.1 at a lower price ($8/$40 instead of $10/$50). Best for long-horizon, open-ended technical work and as an Advisor or Orchestrator for smaller Claude models. Handle stop_reason: "refusal" from the safety classifiers.

Model idclaude-fable-5-2

Price$8 in, $40 out per 1M tokens

Checked9 November 2026

Knows up to June 2026

1,712events after its cutoff

79 historic, 388 major. 132 days of news.

It launched on 9 November 2026, already missing 1,709 of them.

Five things it has never heard of

How to call it

6 ways to use Claude Fable 5.2, with the model id each provider expects.

Providers, model ids, endpoints and docs for Claude Fable 5.2
ProviderModel idEndpointDocs
Anthropic API (Claude API) claude-fable-5-2 https://api.anthropic.com/v1/messages platform.claude.com
AWS Bedrock anthropic.claude-fable-5-2 platform.claude.com
Google Cloud (Claude Models on Google Cloud) claude-fable-5-2 platform.claude.com
Microsoft Foundry (Azure) claude-fable-5-2 platform.claude.com
OpenRouter anthropic/claude-fable-5.2 openrouter.ai
Web app (all paid plans), Claude Code claude.ai

Pricing

Prices for Claude Fable 5.2
Input$8 per 1M tokens
Output$40 per 1M tokens
Cache write, 5 minutes$10 per 1M tokens
Cache write, 1 hour$16 per 1M tokens
Cache read$0.20 per 1M tokens

As published: “per 1M tokens (USD); fast mode (up to 2.5x faster output) $16 input / $80 output”.

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
9 November 2026
Status
Current
Type
Reasoning model

What stands out

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

  • Top agentic-coding score at launch

    FrontierCode 2.0: 49.1% at Xhigh effort, the highest of any released model Anthropic tested (Opus 5.5 45.5%, GPT-6 Astra 42.8%, Gemini 4 Carbon 41.1%); at High effort it matches Opus 5.5’s best for about half the cost per task. Vendor numbers.

    Source: anthropic.com

  • Fermat’s Last Theorem formalized in 30 hours

    First

    About 1,000 Fable 5.2 agents fully formalized FLT in Lean in 30 hours with minimal human intervention (the first formalization by an unreleased Claude took 11 days); Opus 5.5 with the same setup reached 26% in 18 hours.

    Source: anthropic.com

  • Robot control without robotics training

    RoboDojo Sim (simulated two-arm robot from camera images): 64.9% at Max effort, versus 39.4% for Opus 5.5, 34.2% Gemini 4 Argon and 29.8% GPT-6 Astra in Anthropic’s runs; beats most purpose-built robot-control systems on the public board.

    Source: robodojo-benchmark.com

  • Hardware design end to end

    From a one-paragraph prompt it specified, sourced parts for, routed four-layer boards and wrote firmware for three devices (voice hub, USB speakerphone, handheld pet) built with Diode; all worked without electrical changes. BenchCAD 2.1: 83.5 vs 65.3 for Opus 5.5.

    Source: anthropic.com

  • Open physics problems

    Solved two open problems on holographic black holes (Hawking–Page transition at weak coupling is first order; the exact limit of the modular bootstrap slope), posted on Hexagon as 2611.00175 and 2611.00174.

    Source: hexagonmath.org

  • Fewer safety-classifier blocks

    About 55% fewer blocks than Fable 5.1 in early testing (60% fewer in cyber, 40% in biology); blocked cyber queries are answered by Opus 4.8 and biology ones by Opus 5.

    Source: anthropic.com

Four assistants, one scale

Claude Fable 5.2 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).

  1. GPT-6 Astra 271 at launch, 1,780 today
  2. Claude Opus 5.5 372 at launch, 1,712 today
  3. Gemini 4 Argon 1,121 at launch, 1,806 today
  4. Grok 4.7 387 at launch, 1,746 today
  5. Claude Fable 5.2 1,709 at launch, 1,712 today
Show as a table
ModelCutoffReleasedMissing at launchMissing today
GPT-6 AstraApril 20263 September 20262711,780
Claude Opus 5.5June 202622 September 20263721,712
Gemini 4 ArgonMarch 202613 October 20261,1211,806
Grok 4.7May 202621 September 20263871,746
Claude Fable 5.2June 20269 November 20261,7091,712

Notes

Same underlying model as Claude Mythos 5.2 (Mythos without the cyber/biology classifiers, for verified organizations). Up to 30% faster output than Fable 5.1; optional fast mode up to 2.5x. Default effort: high on the API, medium in Claude apps and Claude Code. Retirement not before 2027-11-09. Anthropic still recommends Opus 5.5 as the starting point for most coding and knowledge work. AI-R&D-specific capabilities (kernel optimization, LLM architecture work) were deliberately held at about Opus 5.5 level during training; transparent fallbacks to Opus 5 on some of those topics. Strongest anti-distillation protections; preserved thinking now applies to all accounts. 30-day retention for safety monitoring unless the customer uses Enterprise Frontier Safeguards (ZDR-compatible).

Launch benchmarks (Anthropic, safeguards on, highest effort unless noted): FrontierSWE v2 69.9%, AutomationBench 51.4%, Terminal-Bench-Science 0.1 74.6%, OSWorld 2.1 (offline, partial) 89.3%, WANDR 82.1%, Remote Labor Index 41.3%, Humanity’s Last Exam (tools) 74.2%, Chartography 73.4%, AA-Briefcase 66.1% rubric / 1785 Elo. Independent leaderboards had not published results on launch day.

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-5-2","max_tokens":16000,"messages":[{"role":"user","content":"Hello"}]}'