Anthropic: Claude Sonnet 4.5
anthropic/claude-sonnet-4-5
Access Claude Sonnet 4.5 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-sonnet-4-5"
}).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-sonnet-4-5"
}).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-sonnet-4-5",
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-sonnet-4-5",
"messages": [
{"role": "user", "content": "Explain quantum computing in simple terms"}
]
}'
Model Card
Claude Sonnet 4.5 is Anthropic's most capable model for agents and computer use, released September 2025. It can maintain focus for 30+ hours on complex tasks, supports a 1M token context window (beta), and is described as their "most aligned frontier model."
Context Window 200K
tokens
Max Output 64K
tokens
Input Cost $3
per million tokens
Output Cost $15
per million tokens
Input text, image, pdf
modalities
Tool Use Yes
Knowledge Cutoff Jul 31, 2025
Release Date Sep 29, 2025
Model Playground
Try Claude Sonnet 4.5 instantly in your browser.
This playground uses the Puter.js AI API — no API keys or setup required.
Benchmarks
How Claude Sonnet 4.5 performs on standard evaluations.
| Benchmark | Score |
|---|---|
| GPQA Diamond Graduate-level science Q&A | 72.7% |
| Humanity's Last Exam Cross-domain reasoning | 7.2% |
| LiveCodeBench Recent coding problems | 59.0% |
| SciCode Scientific programming | 42.8% |
| AIME 2025 Advanced math exam | 37.0% |
| IFBench Instruction following | 42.7% |
| LCR Long-context reasoning | 52.3% |
| Terminal-Bench Hard Agentic terminal tasks | 28.8% |
| τ²-Bench Tool use / agents | 70.5% |
Scores sourced from Artificial Analysis.
Find other Anthropic models →
Claude Fable 5.1
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.
ChatClaude 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.
Frequently Asked Questions
You can access Claude Sonnet 4.5 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 Sonnet 4.5 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 | $3 |
| Output | $15 |
Claude Sonnet 4.5 was created by Anthropic and released on Sep 29, 2025.
Claude Sonnet 4.5 supports a context window of 200K tokens. For reference, that is roughly equivalent to 400 pages of text.
Claude Sonnet 4.5 can generate up to 64K tokens in a single response.
Claude Sonnet 4.5 has a knowledge cutoff date of Jul 31, 2025. This means the model was trained on data available up to that date.
Claude Sonnet 4.5 accepts the following input types: text, image, pdf. It produces: text.
Yes, Claude Sonnet 4.5 supports tool use (function calling), allowing it to interact with external tools, APIs, and data sources as part of its response flow.
Claude Sonnet 4.5 scores 29.9 on the Artificial Analysis Intelligence Index, outperforming 68% of tracked models. On math, it scores 37.0 (outperforms 37% of models).
Yes — the Claude Sonnet 4.5 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 Sonnet 4.5 to your app without worrying about API keys or setup.
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