Claude Opus 5 Released: 1M-Context Window Becomes Default Flagship Model of Claude Code

On July 24, 2026, Anthropic released Claude Opus 5, which features native 1 million-token context window, default thinking mode, and the same pricing as Opus 4.8. For Claude Code v2.1.219 and above, accounts such as Max/API will parse "Default" as Opus 5, while the default setting for Pro tier remains Sonnet 5. This article sorts out the specifications of Opus 5, Fast Mode and Effort levels, as well as the toolchain updates of Claude Code in July including Subagent background running, nested delegation, /code-review background review and /doctor self-check, and provides step-by-step guides for version checking and model switching.