Model · Anthropic · Text
Claude Fable 5
The first public Mythos-class model, a tier above Opus 4.8 for demanding reasoning and long-horizon agentic work. Superseded by Claude Fable 5.1 (2026-09-01) but still available.
- Modality
- Text
- License
- Proprietary (Proprietary)
- Context window
- 1,000,000 tokens 1M default with up to 128k output. Uses the tokenizer introduced with Opus 4.7 — the same text produces roughly 30% more tokens than pre-4.7 Claude models.
- Released
- June 9, 2026
- Last verified
- September 8, 2026
- Runs locally
- No
- Also handles
- vision
Strengths
- State-of-the-art on most tested benchmarks — software engineering, knowledge work, vision, and scientific research
- 1M-token context with up to 128k output
- Adaptive thinking always on
Weaknesses
- Most expensive Claude tier ($10/$50 per MTok) — double Opus 4.8
- Safeguard routing: cybersecurity and biology queries are answered by Opus 4.8 instead
- Closed weights — cannot be self-hosted
Try it
| Where | Type | Notes |
|---|---|---|
| Anthropic API | hosted-api | API key required |
| AWS Bedrock | hosted-api | Enterprise / regional |
| Google Vertex AI | hosted-api | GCP integration |
| Claude.ai | product | Paid plans (Pro and above) |
Version history
- Claude Haiku 5.5 Oct 2026
- Claude Sonnet 5.5 Sep 2026
- Claude Opus 5.5 Sep 2026
- Claude Fable 5.1 Sep 2026
- Claude Mythos 5.1 Sep 2026
Official sources
- Model docs docs
- Announcement announcement
Change log
- — Deprecated — superseded by Claude Fable 5.1 (released 2026-09-01). Fable 5 moves to Anthropic's legacy table; still available, retirement not sooner than 2027-06-09.
- — Initial entry. Released 2026-06-09 as Anthropic's most capable widely released model — the first publicly available Mythos-class model, a new tier above Opus 4.8.
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