# Claude Sonnet 4.5 (20250929)

> A dated Anthropic snapshot with reasoning, tool calling and image input, which Anthropic lists as deprecated.

## Key facts

- Model author: Anthropic
- Input: $3.00 per 1M tokens
- Output: $15.00 per 1M tokens
- Cached input: $0.30 per 1M tokens
- Context window: 200,000 tokens
- Maximum output: 64,000 tokens
- Input modalities: image, text
- Output modalities: text
- Capabilities: reasoning, tools, vision
- Released: 2025-09-29
- Knowledge cutoff: Jan 2025
- Model IDs: `anthropic/claude-sonnet-4-5-20250929`
- Model page: https://www.realrelay.ai/model/anthropic/claude-sonnet-4-5-20250929

## Overview

Claude Sonnet 4.5 (20250929) is a model from Anthropic, identified by the snapshot date 20250929 in its model ID. It supports extended thinking, tool calling and image input. Anthropic lists it as deprecated: it is still functional but no longer recommended, and a retirement has been announced.

Claude Sonnet 4.5 (20250929) has a 200K-token context window and can generate up to 64K output tokens. It accepts text and image input and returns text output. It was released on September 29, 2025. Its knowledge cutoff is January 2025.

## Capabilities

Claude Sonnet 4.5 (20250929) supports reasoning, tool calling and image understanding. It accepts text and image as input and produces text as output.

Extended thinking, tool calling and image input work together within a 200K-token context window, so the model can reason over long text and screenshots and call functions as part of a task.

## Pricing

Claude Sonnet 4.5 (20250929) costs $3.00 per 1M input tokens and $15.00 per 1M output tokens. Cache reads are $0.30 per 1M tokens.

Claude Sonnet 4.5 (20250929) is available through RealRelay's OpenAI-compatible API.

## Use cases

Existing applications that already target this snapshot can keep using it while Anthropic lists it as functional, for example a support assistant that reads user screenshots and calls tools to look up orders.

Because it is deprecated and a retirement has been announced, plan to move long-lived workloads to a supported model; the 200K-token context and 64K-token output limits help size that move.

## Call it

OpenAI-compatible chat completions:

```bash
curl https://www.realrelay.ai/v1/chat/completions \
  -H "Authorization: Bearer $REALRELAY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "anthropic/claude-sonnet-4-5-20250929", "messages": [{"role": "user", "content": "Hello"}]}'
```

## FAQ

### What is Claude Sonnet 4.5 (20250929)?

Claude Sonnet 4.5 (20250929) is a model from Anthropic, identified by the snapshot date 20250929 in its model ID. It supports reasoning, tool calling and image understanding and accepts text and image input.

### How much does Claude Sonnet 4.5 (20250929) cost?

Claude Sonnet 4.5 (20250929) costs $3.00 per 1M input tokens and $15.00 per 1M output tokens, with cache reads at $0.30 per 1M tokens.

### What is the context window of Claude Sonnet 4.5 (20250929)?

Claude Sonnet 4.5 (20250929) has a 200K-token context window and can generate up to 64K tokens in a single response.

### What inputs and outputs does Claude Sonnet 4.5 (20250929) support?

Claude Sonnet 4.5 (20250929) accepts text and image input and returns text output.

### Does Claude Sonnet 4.5 (20250929) support tool calling?

Yes. Claude Sonnet 4.5 (20250929) supports tool calling, so it can call functions you define and use the results in multi-step tasks. It also supports reasoning and image understanding.

### When was Claude Sonnet 4.5 (20250929) released?

Claude Sonnet 4.5 (20250929) was released on September 29, 2025. Its knowledge cutoff is January 2025.

### How do I call Claude Sonnet 4.5 (20250929) via the API?

Call Claude Sonnet 4.5 (20250929) through RealRelay's OpenAI-compatible API using the model ID anthropic/claude-sonnet-4-5-20250929.