Claude Opus 5 / 5.5
by Anthropic — the Opus tier of the Claude family, built for long-running agentic coding and knowledge work. Anthropic’s docs recommend Opus 5.5 as the starting point for most workloads.
Versions
| Opus 5.5 (current) | Opus 5 (legacy) | |
|---|---|---|
| Released | 2026-09-22 | 2026-07-24 |
| API ID | claude-opus-5-5 | claude-opus-5 |
| Thinking | adaptive, always on (default effort medium) | adaptive (default effort high) |
| Knowledge cutoff | Jun 2026 | May 2026 |
| Retirement | not sooner than 2027-09-22 | not sooner than 2027-07-24 |
Shared: 1M-token context, 128K max output (300K on the Message Batches API with the output-300k-2026-03-24 beta header), text and image input, text output. Opus 5.5 is priced below Opus 5 and Opus 4.5 to 4.8.
Opus 5.5 vs Opus 5 (breaking changes)
Thinking cannot be disabled; forced tool use returns an error; thinking blocks are tied to the model and conversation; the computer_20251124 computer-use tool is rejected on the Claude API and Google Cloud. Text between tool calls now arrives in thinking blocks (empty at the default display). A research-preview fast mode (priced separately) exists for Opus 5.5 on the Claude API.
Availability
Claude API, Amazon Bedrock (anthropic.claude-opus-5-5), Google Cloud, Microsoft Foundry, Claude Platform on AWS.
Lineage
Replaces Opus 4.8 (and 4.7, 4.6, 4.5) as the recommended Opus. Above it sits Fable 5.1; below it Sonnet 5.5.
Sources
- https://platform.claude.com/docs/en/models/opus-5-5/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/models/opus-5/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/about-claude/models/overview (accessed 2026-09-30)
- https://platform.claude.com/docs/en/about-claude/model-deprecations (accessed 2026-09-30)