# Claude Sonnet 4 spotted on OpenRouter

Claude Sonnet 4 from Anthropic was first recorded on 21 Sep 2026. Its release date is not established. 6 evidence links.

- Kind: Sighting
- Developer: Anthropic
- Confidence: Confirmed
- First seen: 2026-09-21T16:06:18.831Z
- Model: [Claude Sonnet 4](https://alexgetman.com/models/anthropic/claude-sonnet-4-445/)
- Canonical: https://alexgetman.com/signals/2026/09/21/claude-sonnet-4/

## Evidence links

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