As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/claude-fable-5/

# Claude Fable 5

Anthropic, Claude 5 family. Status: legacy. Type: reasoning model. Released: 2026-06-09. Training cutoff: 2026-01.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| Anthropic API (Claude API) | `claude-fable-5` | https://api.anthropic.com/v1/messages | https://platform.claude.com/docs/en/models/fable-5/overview |
| AWS Bedrock (Messages API / Mantle) | `anthropic.claude-fable-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock |
| Google Cloud Vertex AI | `claude-fable-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-on-vertex-ai |
| Microsoft Foundry (Azure) | `claude-fable-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry |
| Claude Platform on AWS | `claude-fable-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws |
| OpenRouter | `anthropic/claude-fable-5` |  | https://openrouter.ai/anthropic/claude-fable-5 |
| Web app |  |  | https://claude.ai |

## Pricing

- Input: $10 per 1M tokens
- Output: $50 per 1M tokens
- Cache read: $1 per 1M tokens
- Unit as published: per 1M tokens (USD); Batch API 50% off
- Source: https://platform.claude.com/docs/en/about-claude/pricing
- Last checked: 2026-09-29

## Specs

- Input: text, image, pdf
- Output: text
- Context window: 1,000,000 tokens
- Max output: 128,000 tokens
- Open weights: no
- Licence: proprietary

## What it has not seen

- Published training cutoff: 2026-01 (January 2026).
- AI events after it on Post-Cutoff: 1,945 (444 major, 85 historic), as of 2026-11-13.
- Already missing at launch: 128.
- Briefings of the news since January 2026: https://postcutoff.com/briefings/cutoff-2026-01-s.md (short), https://postcutoff.com/briefings/cutoff-2026-01-m.md (medium), https://postcutoff.com/briefings/cutoff-2026-01.md (full).
- Its card, with five things it has never heard of: https://postcutoff.com/you/claude-fable-5/

## What stands out

- Strongest cybersecurity capabilities (Mythos 5): Anthropic called the Fable 5 / Mythos 5 generation the 'strongest cybersecurity capabilities of any model in the world'. Mythos 5 runs without safety classifiers for Glasswing defenders. Source: https://www.anthropic.com/news/claude-fable-5-mythos-5
- Rebuild web apps from screenshots (first): Anthropic claims it was the first model to rebuild a web app's source code from screenshots alone. It also completed Pokemon FireRed using vision only. Source: https://www.anthropic.com/news/claude-fable-5-mythos-5
- Massive code migrations: Stripe reported a 50-million-line migration done in one day instead of about two months. Source: https://www.anthropic.com/news/claude-fable-5-mythos-5
- Novel scientific hypotheses: In blind comparisons, scientists preferred its molecular-biology hypotheses about 80% of the time over Opus-class models. Source: https://www.anthropic.com/news/claude-fable-5-mythos-5
- Refusal stop reason with fallbacks (first): Safety classifiers can decline a request with stop_reason 'refusal'. A server-side fallbacks parameter retries on another Claude model. Source: https://platform.claude.com/docs/en/models/fable-5/overview

## Notes

Superseded by claude-fable-5-1 (same price, cheaper cache reads). Still served; retirement not sooner than 2027-06-09. Sibling claude-mythos-5 (Project Glasswing only, no safety classifiers).

Previous top-tier model. Prefer `claude-fable-5-1` for new work.

```bash
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","max_tokens":16000,"messages":[{"role":"user","content":"Hello"}]}'
```

Sources:
- Model page: https://platform.claude.com/docs/en/models/fable-5/overview
- Announcement: https://www.anthropic.com/news/claude-fable-5-mythos-5
- Pricing: https://platform.claude.com/docs/en/about-claude/pricing
- Models overview: https://platform.claude.com/docs/en/about-claude/models/overview
- Deprecations: https://platform.claude.com/docs/en/about-claude/model-deprecations

Model page: https://postcutoff.com/m/claude-fable-5/