# Claude Sonnet 4

Claude Sonnet 4 is a model from Anthropic, first recorded on 21 Sep 2026; its release date is not established.

- Developer: Anthropic
- Id: anthropic/claude-sonnet-4
- Sighting: 2026-09-21T16:06:18.831Z
  - [evidence link](https://openrouter.ai/anthropic/claude-sonnet-4)
- Status: Sighting
- Canonical: https://alexgetman.com/models/anthropic/claude-sonnet-4-445/

## Questions

### When was Claude Sonnet 4 released?

Its release date is not established. Signal Forge first recorded it on 21 Sep 2026.

## Evidence links

- [models.dev · catalogue](https://models.dev/#claude-sonnet-4)
- [models.dev · catalogue](https://models.dev/#databricks-claude-sonnet-4)
- [OpenCode · discovery](https://opencode.ai/data/anthropic/claude-sonnet-4-0)
- [openrouter](https://openrouter.ai/anthropic/claude-sonnet-4)
- [anthropic-pricing](https://platform.claude.com/docs/en/about-claude/pricing)
- [Arena · leaderboards](https://www.anthropic.com/news/claude-4)

## Signals

- [Claude Sonnet 4 spotted on OpenRouter](https://alexgetman.com/signals/2026/09/21/claude-sonnet-4/)