Claude Sonnet 4.5
Key facts
- Released
- Sep 29, 2025
- What it does
- Text and chat: Writes, answers questions and holds a conversation.Code: Writes, explains and fixes code.Thinks first: Can reason step by step before it answers: slower, but better at maths, code and tricky questions.Sees images: Understands pictures, screenshots and charts you share with it.Reads files: Reads documents such as PDFs.
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- Knowledge cutoff
- July 2025 · the latest events it learned about
- How
- For developers, through an API
- Announced as
- “Introducing Claude Sonnet 4.5”
From trckr's archive of releases before it started watching. Date and details from Epoch AI's database of AI models (CC BY 4.0).
Price and limits
What developers pay to use it through the API: How developers plug a model into their own apps and pay per use. A model that's "in the API" can be used by programmers, even if it isn't in a chat app yet., per million Tokens: The small chunks of text a model reads and writes, about three-quarters of a word each. Prices and limits are counted in tokens. sent (input) or written back (output), and how much it can take in at once.
- Input
- $3.00
- per million tokensCached: $0.30
- Output
- $15.00
- per million tokens
- Context window: How much a model can keep in mind at once: your question, any files you share and its own replies. Measured in tokens; 1,000 tokens is about 750 words.
- 200K tokens
- about 150,000 words
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- Longest answer
- 64K tokens (about 48,000 words)
From the lab's own listing on models.dev and OpenRouter, checked .
How it scores
From independent testers, never the lab's own claims.
- Combined test score#76 of 235
- GPT-6 Astra169
- 2GPT-6.1 Sol169
- 75MiniMax-M3148
- 76Claude Sonnet 4.5148
- 77o3-pro147
Source: Epoch AI · Epoch Capabilities Index
- Chat answers, by people's votes#58 of 86
- Gemini 4 Carbon1,527
- 2Gemini 4 Argon1,522
- 57Grok 4.61,456
- 58Claude Sonnet 4.51,456
- 59GPT-5.11,455
Source: LMArena · LMArena text, adjusted for style
Compare Claude Sonnet 4.5 with
It came out 55 days after Claude Opus 4.1, the lab's previous model.
The details
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