Anthropic says Opus 5.5 fast mode is open to all paid tiers at twice the price for up to 2.5x faster output
Anthropic said in its Claude Platform release notes on 15 October 2026 that fast mode for Claude Opus 5.5 is out of research preview. Teams no longer need to request access or send a beta header. Anthropic's fast-mode guide prices it at $8 per million input tokens and $40 per million output tokens, double the $4 and $20 standard rates, for up to 2.5x more output tokens per second.
Why it matters: The speed gain is in output, not in the wait for the first token, so it helps a person watching a long answer stream, such as a coding assistant or a live agent step. It does nothing for background work. At Anthropic's list rates, a session of 50,000 input and 15,000 output tokens costs about $0.50 at standard speed and $1.00 in fast mode, before caching discounts. A CFO who asks what a ticket costs now will see that line double on every request routed to fast.
The catch: The 2.5x is Anthropic's number; the sources read give no independent timing. Falling back from fast to standard speed misses the prompt cache, because requests at different speeds do not share cached prefixes, so a long system prompt is billed at full input price after every fallback. Fast mode has its own rate limit, and exceeding it or hitting capacity returns a 429 or 529 error. Anthropic's guide also lists it as unavailable with the Batch API, a Priority Tier commitment and Claude Platform on AWS.
What to do: Pick the one or two workflows where a person waits on the answer, and run 50 real prompts at both speeds. Compare seconds saved per task with the extra cost per task. Then log the usage.speed field in every response so your cost report shows how much traffic ran fast, and decide before launch whether a rate-limit error retries, queues or falls back to standard speed.
Our coverage →Claude Platform release notes (15 Oct 2026) ↗Claude Platform docs: Fast mode ↗Claude Platform docs: Pricing ↗