Reasoning Effort, and Why It's Codex-Only For Now

Reasoning effort is a real, published control — and right now it's published for exactly one model on this site's entire roster, the one built specifically for agentic coding work.

The four levels

Low, medium, high and xhigh, all stated directly on the Codex-optimized model's own reference page. No other model's page states any reasoning-effort levels at all, and that absence is recorded honestly here rather than assumed to generalize from the one model where it's genuinely documented.

What this control is for

Reasoning effort trades processing depth against latency and, generally, cost — a lower effort level answers faster and typically cheaper for a given task, a higher one spends more computation reasoning through the problem before answering. For agentic coding work specifically, that's a genuinely useful dial: a straightforward, well-scoped edit doesn't need the same effort level as a gnarly, ambiguous refactor, and having the control matters for anyone tuning a workflow rather than accepting a single fixed behavior.

Why this is worth flagging as Codex-only, not assumed universal

It would be easy to assume every current model quietly supports the same four levels, since the concept isn't unique to this one model in the industry generally — but assuming support where it isn't stated is exactly the kind of mistake this site's own early research made three separate times before catching the pattern. If your workload depends on reasoning-effort tuning, that's a real, concrete reason to use the Codex-optimized model specifically, not a generic frontier model that happens to share a similar underlying architecture.

Worth rechecking over time

Documented capabilities do expand to other models in later releases, and this page will be updated the moment another model's own reference page states effort levels of its own — until then, treat this control as belonging to one model, not a family-wide feature.