Anthropic releases Claude Sonnet 4.5
Claude Sonnet 4.5 became the state-of-the-art model on SWE-bench Verified and OSWorld, able to maintain focus on complex tasks for over 30 hours; Anthropic also launched the Claude Agent SDK and Claude Code 2.0. Claude Haiku 4.5 followed on 15 October 2025.
Key facts
- Released 29 September 2025
- SWE-bench Verified: 77.2%, per Anthropic
- OSWorld: 61.4%, per Anthropic
- Observed working autonomously for more than 30 hours on complex tasks
- Same price as Sonnet 4: $3 / $15 per million tokens
What happened
Anthropic released its best coding and computer-use model at the time, alongside the building blocks behind Claude Code as a general agent SDK.
Why it matters
Pushed the length of tasks AI agents can reliably do and made agent-building infrastructure broadly available.
Changelog
- 2026-09-29: created
Related events
- Anthropic releases Claude Opus 4 and Sonnet 4; Claude Code goes GA ★★★★★
- Anthropic releases Claude Opus 4.5 ★★★★
Sources (2)
id: 2025-09-29-claude-sonnet-4-5 · updated 2026-09-29 · open in the interactive timeline