Anthropic: Claude Fable 5.1
anthropic/claude-fable-5-1
Access Claude Fable 5.1 from Anthropic using Puter.js AI API.
Get Started// npm install @heyputer/puter.js
import { puter } from '@heyputer/puter.js';
puter.ai.chat("Explain quantum computing in simple terms", {
model: "anthropic/claude-fable-5-1"
}).then(response => {
document.body.innerHTML = response.message.content;
});
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
puter.ai.chat("Explain quantum computing in simple terms", {
model: "anthropic/claude-fable-5-1"
}).then(response => {
document.body.innerHTML = response.message.content;
});
</script>
</body>
</html>
# pip install openai
from openai import OpenAI
client = OpenAI(
base_url="https://api.puter.com/puterai/openai/v1/",
api_key="YOUR_PUTER_AUTH_TOKEN",
)
response = client.chat.completions.create(
model="anthropic/claude-fable-5-1",
messages=[
{"role": "user", "content": "Explain quantum computing in simple terms"}
],
)
print(response.choices[0].message.content)
curl https://api.puter.com/puterai/openai/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_PUTER_AUTH_TOKEN" \
-d '{
"model": "anthropic/claude-fable-5-1",
"messages": [
{"role": "user", "content": "Explain quantum computing in simple terms"}
]
}'
Model Card
Claude Fable 5.1 is Anthropic's successor to Claude Fable 5, released September 1, 2026, about three months after Fable 5. Anthropic also released a companion model, Claude Mythos 5.1, available only through trusted access programs; both share the same underlying model with different safety safeguards.
On SWE-bench Pro it scores 81.2%, ahead of Fable 5's 80% and Mythos 5's 80.3%. On Terminal-Bench-Science, a scientific-research agentic benchmark, it reaches 52.6%, more than double Fable 5's 24.7% and ahead of GPT-5.6 Sol's 22.4%. On Terminal-Bench 4.0 for agentic coding it scores 55.8%, versus 42.0% for Fable 5 and 37.3% for GPT-5.6 Sol.
Priced at $10/$50 per million input/output tokens, unchanged from Fable 5, with cache reads cut 75% to $0.25 per million tokens. It offers a 1,000,000-token context window, 128,000-token max output, and tool calling. It fits developers running long-horizon agentic coding and research pipelines who want Fable-tier reasoning at lower cost.
Context Window 1M
tokens
Max Output 128K
tokens
Input Cost $10
per million tokens
Output Cost $50
per million tokens
Input text, image, pdf
modalities
Tool Use Yes
Knowledge Cutoff Jun 2026
Release Date Sep 1, 2026
Output Speed 68
tokens / sec
Latency 244.37s
time to first token
Model Playground
Try Claude Fable 5.1 instantly in your browser.
This playground uses the Puter.js AI API — no API keys or setup required.
Benchmarks
How Claude Fable 5.1 performs on standard evaluations.
| Benchmark | Score |
|---|---|
| GPQA Diamond Graduate-level science Q&A | 93.7% |
| Humanity's Last Exam Cross-domain reasoning | 59.1% |
| SciCode Scientific programming | 62.0% |
| LCR Long-context reasoning | 80.0% |
Scores sourced from Artificial Analysis.
Find other Anthropic models →
Claude Opus 5
Claude Opus 5 is Anthropic's flagship model, released July 24, 2026 as the successor to Claude Opus 4.8. Anthropic positions it as approaching the performance of its higher-tier Claude Fable 5 model at roughly half the token cost, built for agentic coding, computer use, and long-horizon knowledge work. On the ARC-AGI-3 novel problem-solving benchmark, Opus 5 scores 30.2%, roughly four times GPT-5.6 Sol's 7.8% and twenty times Opus 4.8's 1.5%. On the GDPval-AA v2 knowledge-work benchmark, it reaches an Elo of 1,861, ahead of Fable 5 (1,747) and GPT-5.6 Sol (1,736). Priced at $5 per million input tokens and $25 per million output tokens, unchanged from Opus 4.8, it offers a 1,000,000-token context window, 128,000-token max output, and tool calling. It fits developers building coding agents and automation pipelines that need strong reasoning at Opus-level pricing.
ChatClaude Opus 5 Fast
Claude Opus 5 Fast is a high-speed configuration of Anthropic's Opus 5 flagship model, generating output tokens at roughly 2.5x the speed of standard Opus 5. It runs the same Opus 5 model, which Anthropic says outperforms Opus 4.8 on agentic coding, computer use, and knowledge work, and approaches Fable 5's performance at roughly half the cost. Fast mode pricing is $10/$50 per million input/output tokens, twice the price of standard Opus 5 ($5/$25) and in line with what Opus 4.8 Fast cost. It supports the full 1M token context window and 128k max output tokens. Choose Opus 5 Fast for latency-sensitive agentic pipelines, live coding sessions, and real-time workflows where throughput matters. For cost-sensitive or batch workloads, standard Opus 5 offers the same intelligence at half the price.
ChatClaude Sonnet 5
Claude Sonnet 5 is Anthropic's newest Sonnet-tier model, released June 30, 2026 as the successor to Sonnet 4.6. Anthropic built it to be the most agentic Sonnet yet, with gains in planning, tool use, coding, and multi-step reasoning that bring it close to Opus 4.8 quality at a lower price. On SWE-bench Pro it scores 63.2%, up from Sonnet 4.6's 58.1% and ahead of GPT-5.5's 58.6%, though still behind Opus 4.8's 69.2%. On Terminal-Bench 2.1 it reaches 80.4% versus Sonnet 4.6's 67.0%, and on the OSWorld-Verified computer-use benchmark it posts 81.2% against Sonnet 4.6's 78.5%. It targets developers running agentic coding pipelines, automation workflows, and tool-heavy tasks who want most of Opus-tier capability without Opus pricing. Introductory pricing is $2/$10 per million input/output tokens through August 31, 2026, after which it reverts to the standard $3/$15 listed here.
Frequently Asked Questions
You can access Claude Fable 5.1 by Anthropic through Puter.js AI API. Include the library in your web app or Node.js project and start making calls with just a few lines of JavaScript — no backend and no configuration required. You can also use it with Python or cURL via Puter's OpenAI-compatible API.
Yes, it is free if you're using it through Puter.js. With the User-Pays Model, you can add Claude Fable 5.1 to your app at no cost — your users pay for their own AI usage directly, making it completely free for you as a developer.
| Price per 1M tokens | |
|---|---|
| Input | $10 |
| Output | $50 |
Claude Fable 5.1 was created by Anthropic and released on Sep 1, 2026.
Claude Fable 5.1 supports a context window of 1M tokens. For reference, that is roughly equivalent to 2,000 pages of text.
Claude Fable 5.1 can generate up to 128K tokens in a single response.
Claude Fable 5.1 has a knowledge cutoff date of Jun 2026. This means the model was trained on data available up to that date.
Claude Fable 5.1 accepts the following input types: text, image, pdf. It produces: text.
Yes, Claude Fable 5.1 supports tool use (function calling), allowing it to interact with external tools, APIs, and data sources as part of its response flow.
Claude Fable 5.1 scores 65.7 on the Artificial Analysis Intelligence Index, outperforming 100% of tracked models. On coding, it scores 81.6 (outperforms 100% of models).
Yes — the Claude Fable 5.1 API works with any JavaScript framework, Node.js, or plain HTML through Puter.js. Just include the library and start building. See the documentation for more details.
Get started with Puter.js
Add Claude Fable 5.1 to your app without worrying about API keys or setup.
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