Anthropic Prices Opus 5.5 at $4 per Million Input Tokens, 20 Percent Below Opus 5

Anthropic's Claude Opus 5.5 is the latest entrant in the contest that increasingly decides frontier application programming interface (API) market share: how much capability a vendor can deliver per dollar of inference. The company lists the model at 4 dollars per million input tokens and 20 dollars per million output tokens, down from 5 and 25 for Opus 5. Cache reads fell further, from 0.50 to 0.20 dollars per million tokens, according to coverage of the release.

The more consequential claim is not the listed price. Anthropic says Opus 5.5 performs at the level of Claude Fable 5.1, its September flagship for coding and knowledge work, while costing about 40 percent less to run than Opus 5. That figure combines the roughly 20 percent price cut with the model spending fewer tokens to complete the same task. For anyone paying for long agentic runs, token count is the larger cost driver, and a model that reasons in fewer steps multiplies that saving across every call.

On Anthropic's own table, Opus 5.5 leads on SWE-bench Pro at 89.9 percent and Terminal-Bench 4.0 at 66.4 percent. Those are vendor-published numbers. The independent check comes from Artificial Analysis, which placed Opus 5.5 at the top of its Intelligence Index with a score of 58 at maximum effort, leading on six of ten core evaluations including Humanity's Last Exam at 61.4 percent and SciCode at 66.9 percent. When independent indices and vendor tables agree on the direction of a result, that is stronger evidence than either alone, though neither measures the failure modes that appear in production agent loops.

The competitive pressure affects both Anthropic and its rivals. The Telegram channel AI Post, which tracks lab releases, reported that Opus 5.5 is pressuring OpenAI's GPT-6 Astra and speculated about a GPT-6.5 response. No lab has confirmed such a model, and that detail should be read as channel speculation rather than fact. What is documented is the price floor beneath the whole market: Meta charges 1.25 dollars input and 4.25 dollars output per million tokens for Muse Spark, and offers a 0.10 dollar tier to developers who let Meta train on their traffic.