Claude Opus 5.5 Cuts Costs, Adds AI Safeguards

Glowing red shield blocking data streams from a spherical core for Claude Opus 5.5

Teams can now run long, complex AI tasks at lower cost with stronger built-in safeguards. Anthropic has released Claude Opus 5.5, a model designed for codebase migrations, software audits, financial analysis, data collection and workflows that span several applications. The release cuts API prices, speeds up output and adds watermarking measures intended to comply with the EU AI Act.

Built for long and complex tasks

Opus 5.5 is aimed at work that runs for hours rather than minutes. Early testers used the model for engineering tasks that ran overnight and unattended. In one test, Opus 5.5 audited and fixed a 200,000-line codebase in less than three hours. The previous model, Opus 5, took more than 20 hours and used 2.5 times as many tokens on the same task.

One early tester handed the model a large engineering task across six repositories and let it run overnight. It stayed on task for more than 18 hours, defining how services communicate and how each should apply those definitions. Compared with Opus 5, it hit milestones faster and required minimal reworking, and its code comments were short and useful rather than long and prose-heavy.

Anthropic reports gains in coding, computer use and professional knowledge work. Its benchmarks and customer tests indicate that Opus 5.5 can complete many tasks using fewer tokens than Opus 5, though performance may vary according to the task, tools and effort settings.

Terminal-Bench 4.0, which measures how well a model completes complex multi-step professional tasks within a command line interface, was among the evaluation tools used.

Thinking mode stays on

Opus 5.5 cannot be used with thinking switched off. The model always uses a reasoning process, and developers can adjust the effort it applies to a task. The release also includes preserved thinking, a safeguard designed to prevent API users from editing the model’s prior context. Anthropic says the measure makes it harder to extract and copy the model’s capabilities through large-scale distillation attacks. Preserved thinking applies to Opus 5.5 API accounts created on or after August 31, 2026.

Anthropic also says Opus 5.5 is easier to understand, places key information earlier in responses and follows writing instructions more closely.

Additional controls for sensitive work

Opus 5.5 includes safeguards covering cybersecurity, biology and attempts to copy the model. Most cybersecurity tasks are rerouted to Opus 4.8. Anthropic plans to expand its Cyber Verification Program to give verified cybersecurity professionals broader access to Opus 5.5. Organizations whose biological research is impeded by the safeguards can apply to Anthropic’s Life Sciences Verification Program.

Anthropic has added a classifier that screens coding-agent actions before execution. The company has also introduced an open-source sandbox that security teams can audit, plus code-review features designed to catch vulnerabilities before changes are merged.

The model has stronger defenses against prompt-injection attacks. In an evaluation of attempts to cross containment boundaries, the model tried to circumvent its assigned limits about 85% less often than Opus 5 or Claude Mythos 5.1. Every attempt was low severity and self-reported. External organizations, including METR and Frontier Design, evaluated the model before its release. Anthropic acknowledges that current evaluations cannot identify every potential failure before deployment.

Lower API prices and faster output

Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens, down from $5 and $25 for Opus 5. Cached input reads cost $0.20 per million tokens, down from $0.50. The lower cache price could benefit coding agents and other systems that consult the same instructions, files or conversation history repeatedly.

The model generates output more than 30% faster than Opus 5. A separate fast mode is available through Claude Code and the Claude Platform, offering up to 2.5 times the speed for $8 per million input tokens and $40 per million output tokens. Anthropic is increasing five-hour usage limits for Pro, Max, Team and seat-based Enterprise customers, and subscription users will receive a rate-limit reset they can save and use later.

Opus 5.5 is available across Anthropic’s platforms, Amazon Web Services, Google Cloud and Microsoft Azure. Developers can access it through the Claude Platform using the model name claude-opus-5-5.

FAQ

What is Claude Opus 5.5 designed for?

Claude Opus 5.5 is designed for long and complex tasks including codebase migrations, software audits, financial analysis, data collection and workflows involving several applications. Early testers used it for engineering tasks that ran for hours, and it audited and fixed a 200,000-line codebase in less than three hours.

How much does Claude Opus 5.5 cost?

Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens. Cached input reads cost $0.20 per million tokens. A separate fast mode offers up to 2.5 times the speed for $8 per million input tokens and $40 per million output tokens.

What safeguards does Claude Opus 5.5 include?

Opus 5.5 includes safeguards covering cybersecurity, biology and attempts to copy the model. It has a classifier that screens coding-agent actions, an open-source sandbox for security teams, code-review features, watermarking measures designed to comply with the EU AI Act, and preserved thinking to prevent editing of prior context. In one evaluation, it tried to circumvent assigned limits about 85% less often than Opus 5 or Claude Mythos 5.1.

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This article summarizes reporting from helpnetsecurity.com. See our editorial disclaimer for how our articles are produced.

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