Claude Sonnet 4.5

Made by Anthropic · Text model · Released September 2025 · claude-sonnet-4-5-20250929

Older version. Prefer Sonnet 4.6 or 5.

Private by design

When you use Claude Sonnet 4.5 in Polymeti, your browser sends the message to Anthropic directly, with your own API key. Nothing passes through a Polymeti server.

We never see your conversation.
Your API key is stored in your browser, not on our servers.
Your chat history lives on your device. Back it up to your own Google Drive if you want it on more than one.

What it can do

Context window

200,000 tokens

≈ 150,000 words · about 600 pages
Max output

64,000 tokens

≈ 48,000 words in a single answer
Knowledge cutoff

January 2025

its training cutoff

Reads images you attach
Uses tools

Modalities

Text Input and output
Image Input only
Audio Not supported
Video Not supported

Features

Streaming Supported
Function calling Supported
Structured outputs Supported
Fine-tuning Not supported

Ready to try it?

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Bring your own API key · Your chats stay in your browser