Anthropic released Claude Opus 4.5 on November 24, 2025, framed in the company's own release notes as "our most powerful frontier model to date" at launch. The introduction was accompanied by a dedicated blog post on the Anthropic news domain and tracked through the Claude Platform release notes, which document ongoing API, SDK, and Console updates for the family. Beyond OpenRouter's catalog entry, the model is accessible through Anthropic's first-party API channels, and the OpenRouter surface explicitly tags it under the claude-opus family with text, image, and PDF inputs feeding a text output pipeline.

Claude Opus 4.5 was positioned for the kinds of tasks where Anthropic's flagship line has historically excelled: deep reasoning, agentic tool use, and structured workflows that mix natural language with external actions. The the cataloged API limit context window combined with the cataloged API limit output ceiling gives it room to handle long documents, multi-step plans, and code-heavy sessions without aggressive trimming. In practice it suits teams that need a frontier-tier model for analysis, coding assistance, research synthesis, and tool-driven automation, while staying within a per-million-token pricing structure that reflects its top-of-line role in the Opus lineup.