Model Watch · Anthropic
Claude Sonnet 4.5
Costs more than Sonnet 5 and gives you less. It's here because a lot of production code still pins to it.
What is Claude Sonnet 4.5?
Claude Sonnet 4.5 is a model from Anthropic, built in the US. It's out, and you can call it today.
When did Claude Sonnet 4.5 come out?
Anthropic released it on 29 September 2025. That date comes from the lab's own docs.
What does it cost, and how much context does it hold?
| Lab | Anthropic |
|---|---|
| Built in | US |
| Status | released |
| API model id | claude-sonnet-4-5-20250929 |
| Released | 29 September 2025 |
| Context window | 200K tokens |
| Max output | 64K tokens |
| Input, per 1M tokens | $3.00 |
| Output, per 1M tokens | $15.00 |
List prices per million tokens, read off the lab's own docs. Caching, batching and volume deals all cut the real number, so treat this as the ceiling. Check the source before you budget against it.
At 700 words in and 500 out, twenty times a day, that works out around $7.68 a month. Put your own numbers in, see every Anthropic price, or put it next to another model.
How does it compare to Anthropic's other models?
| Model | Status | Date | Context | In / 1M | Out / 1M |
|---|---|---|---|---|---|
| Claude Sonnet 4.5 | released | 29 September 2025 | 200K tokens | $3.00 | $15.00 |
| Claude Mythos 5.1 | released | 1 September 2026 | 1M tokens | $10.00 | $50.00 |
| Claude Fable 5.1 | released | 1 September 2026 | 1M tokens | $10.00 | $50.00 |
| Claude Opus 5 | released | 24 July 2026 | 1M tokens | $5.00 | $25.00 |
| Claude Sonnet 5 | released | 30 June 2026 | 1M tokens | $2.00 | $10.00 |
| Claude Fable 5 | released | 9 June 2026 | 1M tokens | $10.00 | $50.00 |
| Claude Opus 4.5 | released | 24 November 2025 | 200K tokens | $5.00 | $25.00 |
| Claude Haiku 4.5 | released | 15 October 2025 | 200K tokens | $1.00 | $5.00 |
| Claude Opus 5.1 | rumoured | — | — | — | — |
| Claude Opus 4.1 | deprecated | — | — | $15.00 | $75.00 |
A dash means the lab hasn't published that number for that model.
Every mention we've logged
Every tracked post, release, changelog entry or incident whose title or summary names Claude Sonnet 4.5. Newest first, each one linking to where the lab published it.
Nothing yet. The name hasn't appeared in a tracked source.
Claude Sonnet 4.5 is part of the Claude 4 family, which is where the point releases sit next to each other.
Keep reading
The release timeline is every model we know about, filterable by lab, country and date. The tracker is the live feed these mentions come from, and Model Watch is the whole catalogue on one page.
More from Anthropic:
- Claude Mythos 5.1 · released
- Claude Fable 5.1 · released
- Claude Opus 5 · released
- Claude Sonnet 5 · released
- Claude Fable 5 · released
- Claude Opus 4.5 · released
- Claude Haiku 4.5 · released
- Claude Opus 5.1 · rumoured
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