Claude Opus 5: current reasoning model on Okou
A current reasoning model with Built-in access through Okou.
1M tokens · Text / Vision / Code · Prompt cache
A current reasoning model from Anthropic, available in Okou's public model catalog.
What is Claude Opus 5?
Released July 24, 2026
Okou currently offers Claude Opus 5 in its public reasoning model catalog. Select it with model ID claude-opus-5; its relative Built-in cost is tier $$$.
What's notable about Claude Opus 5
Headline architecture and capability features.
Opus 5 has a 1M-token context window — the maximum is also the default — and up to 128K output tokens, with a May 2026 knowledge cutoff. Thinking is on by default and reasoning depth is set through effort levels low, medium, high, xhigh, and max; the raw chain of thought is never exposed, only a readable summary. Assistant-message prefill is not supported, and sampling parameters (temperature, top_p, top_k) are rejected — steer behavior with prompting instead. Inputs span text, high-resolution vision, and code.
Specs at a glance
Claude Opus 5 benchmarks
Vendor-reported scores from Anthropic's launch materials. Third-party trackers report different figures for the same benchmarks depending on dataset, effort setting, and agent scaffold, so treat the headline numbers as configuration-dependent.
Claude Opus 5 pricing
Relative Built-in credit cost. Actual charges depend on usage and settings; check the app for current prices.
Best agent tasks for Claude Opus 5
The multi-file feature that lands in one run
Give it the full specification up front and let it run. Opus 5's gains over Opus 4.8 are largest on hard, multi-step engineering work — larger refactors, end-to-end features — and smallest on single-turn edits, so point it at the top of your difficulty range.
The overnight agent you can afford to leave running
Long autonomous runs are where the price difference compounds. At Fable-adjacent quality and half the token cost, a nightly triage, migration, or research agent costs roughly half as much per completed task.
The business workflow that has to finish, not just respond
Multi-step tasks with tools and a real end state — filing tickets, updating spreadsheets, reconciling records. Anthropic's AutomationBench and OSWorld results point at the same thing: it finishes end-to-end tasks that other models drop partway.
Frequently asked questions
Is Claude Opus 5 better than Claude Fable 5?
On several evaluations, yes: Opus 5 leads Fable 5 on Frontier-Bench v0.1, GDPval-AA v2, and SWE-bench Verified. Fable 5 still leads on the harder SWE-bench Pro set and on factual breadth, and it remains the higher ceiling for the hardest reasoning. For most agentic work Opus 5 wins on cost per completed task.
Is thinking on by default on Claude Opus 5?
Yes. A request that omits the thinking parameter reasons before answering — a change from Opus 4.8, where thinking was off unless requested. Depth is controlled with effort (low through max), and thinking can be disabled only at effort high or below. The raw chain of thought is never returned, only a readable summary.
What changes when migrating from Opus 4.8?
The model id, and then prompt tuning. Thinking on by default means max_tokens now covers reasoning as well as the answer; verification instructions should be removed rather than rewritten, since Opus 5 self-verifies; and responses run longer by default, so add an explicit conciseness instruction if length matters.
Alternatives
Using Claude Opus 5 on Okou
Choose Claude Opus 5 in the chat model selector when it is enabled for your workspace. Available provider connections and billing are shown in model settings.
Credits and the $$$ price tier
Relative Built-in credit cost. Actual charges depend on usage and settings; check the app for current prices.
Available on Okou since July 25, 2026.
