Anthropic

Claude Fable 5.1

Frontier coding and agentic model by Anthropic with state-of-the-art SWE-Bench Verified performance.

#26released Aug 15, 2026·Proprietary·Not disclosed
textimage500K ctxreasoning
Intelligence
88.4 #26
Top 3% tier
Output Speed
85 t/s
TTFT 350 ms · ITL 11.8 ms/tok
Blended price (3:1)
$6 /1M
In $3/M · Out $15/M
Context
500K
≈ 1,250 A4 pages · max out 32,768

Quality Domain Radar

6-Axis Frontier Evaluation vs Category Average & Flagship

Claude Fable 5.1
Claude Mythos Preview (#1)
Average (68)
Coding (95.5)Mathematics (93.4)Hard Science (GPQA) (92)Agentic & Tool Use (86.4)Knowledge (MMLU) (58)Vision / Multimodal (62)

Radar axes are approximated from category scores where direct benchmark measurements are missing — see Methodology.

Strengths & Trade-offs

Where it wins

  • Frontier coding at GA — top SWE-bench Verified tier
  • Mythos-class capability with publicly documented mitigations
  • 1M context with strong agentic and long-context scores

Trade-offs to watch

  • $10/$50 premium-tier pricing
  • Some cybersecurity queries are down-routed to Opus 4.8
  • Closed weights — API only

Killer Use Cases

Production agentic coding
Mythos-tier coding available to every developer through the standard API.
Knowledge work automation
Long-horizon document, analysis and research tasks.
Secure code review
High-recall review of large diffs with safeguarded output.

Developer Quickstart & API

Set ANTHROPIC_API_KEY first — get an API key
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": 1024,
    "messages": [{"role": "user", "content": "Refactor this function for O(n) time and explain the change."}]
  }'

Official Resources & Links

API deployment

Compare hosts & latency

Throughput, TTFT and cache pricing across Groq, Cerebras, Together, DeepInfra, Fireworks, Bedrock and Azure.

GroqCerebrasTogether AIDeepInfraFireworks AIAWS BedrockAzure AI
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Scores by Source

Head-to-head Live Matchups

Live Specs & Architecture

Under the hood
Mythos-class transformer — GA configuration
  • Fable 5.1 refresh — same Mythos-class backbone with updated post-training
  • 500K context with effort tiers low → xhigh
  • Published joint system card with Mythos 5.1 (September 2026)
Release date
Aug 15, 2026
Architecture
Mythos-class transformer — GA configuration
Parameters
Not disclosed
License
Proprietary
Context Window
500,000 tokens
Max Output
32,768 tokens
Modalities
text + image
Cache Pricing
read $0.3 · write $3.75 /1M
Reasoning
Effort levels
Input Price
$3/M
Output Price
$15/M
Output Speed
85 t/s
Time to First Token
350 ms
Data Updated
Sep 2, 2026

Estimated monthly bill

Estimated monthly spend
$0.00
Calculating savings vs GPT-4o...

Cite & embed

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BibTeX
@misc{llmpodium2026claudefable51,
  title = {Benchmark Analysis and Intelligence Evaluation of Claude Fable 5.1},
  author = {LLMPodium Research},
  year = {2026},
  url = {https://llmpodium.com/models/claude-fable-5-1}
}

Embed Score Badge

Add a live Podium Score badge to your GitHub or Hugging Face README — it links back to the live ranking.

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Claude Fable 5.1 LLMPodium Score
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