Anthropic has officially opened Claude Opus5.5 Fast Mode to all developers, ending the previous research preview phase and removing the waitlist. The mode does not trim model weights or reasoning capability; instead, by optimizing the underlying configuration, it raises output speed to 2.5x that of standard mode while lowering billing prices. Currently, Fast Mode supports only some models in the Opus series, and developers can enable it by adding a single parameter.
In terms of usage mechanics, Fast Mode has its own independent rate limits and does not share the prompt cache with standard mode. Anthropic also provides billing inquiry methods for different user groups as well as enterprise-grade governance solutions, helping developers monitor usage and reduce cost risks from excessive calls.
In addition, Claude recently launched an idle compaction feature, which can reduce Token consumption in long sessions, and users can also manually turn it off as needed. Meanwhile, Fable5.5 has entered the early gray-testing stage and is expected to be officially released later.
This full opening of Fast Mode further lowers the barrier for developers to use high-speed model inference, and it also reflects that Anthropic is expanding the application scenarios of high-performance models through coordinated optimization of inference speed, calling cost, and resource management mechanisms.