Claude Opus 5.5

Claude Opus 5.5 is positioned as a frontier model for long-running agentic coding and knowledge work, combining a 1M-token context window, up to 128K output, adaptive thinking, tool use, caching, and lower token pricing. Its practical value is best evaluated through task quality, trajectory length, cost, and operational reliability.

Frontier models increasingly operate as agents rather than single-turn chatbots. A production task can involve many model turns, tools, retries, verification steps, and large repeated contexts, making cost per completed task as important as single-pass capability.

The production problem is to deliver strong frontier performance while controlling token volume, latency, tool interactions, retries, context growth, and safety interventions across long-running agent trajectories.

Anthropic publicly describes adaptive thinking, effort control, long context, prompt caching, tool use, and deployment safeguards, but does not disclose enough internal architecture or training detail to reconstruct the model itself.

Evaluation combines Anthropic benchmark matrices, pricing and accuracy-versus-cost views, and the stated benchmark conditions. Results are interpreted with effort level, safeguard configuration, competitor setup, and benchmark uncertainty preserved.

The practical production architecture is application state -> model -> tools -> observations -> model -> verification -> final result, surrounded by context management, prompt caching, policy controls, and safety systems.

The evaluation set includes Terminal-Bench 4.0, FrontierCode v1.1 Main, CursorBench 4.0, GDPval-AA v2.1, AutomationBench, Humanity’s Last Exam, Terminal-Bench-Science 0.1, OSWorld 2.0, Chartography, and WANDR.

The public release does not disclose a complete training recipe, architecture, parameter count, or optimization objective. The production-facing evidence therefore focuses on observable inference behavior, effort controls, and task economics.

Anthropic reports 66.4% Terminal-Bench 4.0, 54.4% FrontierCode v1.1 Main, 57.8% CursorBench 4.0, 1846 GDPval-AA v2.1, 40.0% AutomationBench, 67.7% Humanity’s Last Exam with tools, 58.7% Terminal-Bench-Science 0.1, 81.8% partial OSWorld 2.0, and 89.0% Chartography with tools.

The principal internal baseline is Claude Opus 5. External comparisons include the models shown in Anthropic’s launch matrix, interpreted under the reported effort and benchmark conditions.

Effort level, benchmark version, safeguard behavior, cache configuration, and task setup are important experimental dimensions. Default-effort accuracy-versus-cost results should not be merged with the headline maximum-effort matrix.

Internal architecture and training details remain undisclosed. Benchmark conditions vary, safeguard interventions can route work to other models, and some third-party comparisons use different tooling or task budgets.

Opus 5.5 should be evaluated as an agentic production system rather than only a benchmark score: useful comparisons combine task success, tokens, retries, latency, cost, tool behavior, and safeguards.

Anthropic Claude Opus 5.5 release and model documentation; published benchmark methodology and pricing; cited third-party benchmark documentation.