Anthropic releases Claude Opus 5.5 with cost reductions and four breaking changes

Anthropic has officially launched Claude Opus 5.5, featuring a 20% reduction in input and output costs, a 60% cut in cache read prices, and half-price batch processing. While the model offers improved performance and speed, developers must address four specific compatibility changes before migrating from Opus 5 to avoid 400 errors. These changes include the removal of the 'thinking disabled' parameter, restrictions on forced tool calls, new requirements for thinking block compatibility, and an updated computer use tool version. Additionally, the default effort level has been adjusted to medium, and the model includes enhanced safety features, such as a new biosecurity classifier.