Anthropic announced Opus 5.5 on September 22, 2026. The company says it performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5. Those are Anthropic's comparisons; TechReadly did not independently reproduce them.
Pricing and availability
Anthropic lists the following prices per 1 million tokens:
| Tier or feature | Claude Opus 5 | Claude Opus 5.5 | Opus 5.5 Fast mode |
|---|---|---|---|
| Input | $5 | $4 | $8 |
| Cached reads | $0.50 | $0.20 | — |
| Cache writes | $6.25 | $5 | — |
| Output | $25 | $20 | $40 |
Opus 5.5 is available on the Claude Platform as claude-opus-5-5 and across Amazon Web Services, Google Cloud and Microsoft Azure. Fast mode is available in Claude Code and the Claude Platform at the higher input and output rates listed above.
Anthropic says Opus 5.5 is particularly suited to long coding and knowledge-work jobs. Its public evaluation page includes results from Anthropic, external evaluators such as METR and Frontier Design, and named public reports for other models. The mixture is useful context for the company's claims, but it is not an independent cross-vendor test conducted by TechReadly.
Safeguards for higher-risk work
Anthropic says Opus 5.5 is comparable to Claude Mythos 5.1 in biology and cybersecurity. Vetted organizations can apply to the Life Sciences Verification Program for biology research. Anthropic also says it will expand its Cyber Verification Program in the coming weeks for verified cybersecurity practitioners.
The announcement separately says Opus 5.5 includes preserved thinking for API accounts created on or after August 31, 2026, remains available with zero data retention like previous Opus models, and uses the company's watermarking measures. These controls and access conditions are part of Anthropic's stated deployment policy, not a guarantee that every account or workflow receives the same permissions.
For teams running long-lived agents, Opus 5.5 offers a lower listed token cost and multiple cloud access paths. Sensitive-domain users need to account for the additional review and verification requirements before treating it as a general-purpose endpoint.