Cmd. /effort
Set or inspect model-specific reasoning effort.
Written and reviewed by Eric Han · Co-founder & CTO, reopt
Key takeaways
- Set or inspect model-specific reasoning effort.
- Check the input surface and availability before using the examples below.
Purpose
Set or inspect model-specific reasoning effort.
/effort [level|auto|status|ultracode [on|off]]Availability
| Field | Value |
|---|---|
| Input surface | Running CLI prompt |
| Kind | Built-in |
| Status | Current reference |
| Aliases | — |
| Documented minimum | Not specified |
| Reviewed against | 2026-10-23 · Claude Code 2.1.308 |
Use a level supported by the model. Opus 5.5, Sonnet 5.5, and Haiku 5.5 default to medium. The ultracode on and off arguments, and keeping the current level, require v2.1.284+.
Examples
/effort status
/effort ultracode offEffects and persistence
Adjusts reasoning effort for the active model. Session-only values and saved defaults depend on the model, level, and input surface. Ultracode is a separate toggle, so turning it on or off leaves the effort level unchanged.
Inspecting or resetting effort
Use /effort status to inspect the active level. /effort auto returns to the model default. Supported levels differ by model; check the model configuration reference before selecting one.
Opus 5.5, Sonnet 5.5, and Haiku 5.5 default to medium; Opus 4.7 defaults to xhigh; other effort-capable models default to
high. Haiku 5.5 (v2.1.293+) supports low through xhigh and max, like Opus 5.5 and Sonnet 5.5. Thinking cannot be
turned off on Opus 5.5, Sonnet 5.5, Haiku 5.5, or the Fable models, so lowering effort is the way to reduce thinking there. A top-level effortLevel in user settings (the format /effort wrote before per-model
modelSettings) still applies to Opus 5 and Fable 5.1, but Opus 5.5 and later models ignore it and start
at their own default until you choose a level with /effort or the /model picker. A top-level
effortLevel in project, local, or managed settings, or passed with --settings, applies to every model.
From v2.1.280, the launch-default hold on Opus 4.7, Opus 4.8, and Fable 5 no longer overrides /effort
in -p or the Agent SDK, project/managed/--settings effortLevel, or a per-model level.
Cautions
max is session-only. Ultracode is a separate toggle rather than an effort level: /effort ultracode (or ultracode on) turns it on for the session at the current level, /effort ultracode off turns it off, and Tab flips it in the /effort slider. The ultracode setting persists it, while --effort ultracode turns it on and also sets the level to xhigh. The on and off arguments, the slider toggle, and keeping ultracode on at levels other than xhigh require v2.1.284+; before that, /effort ultracode set the session to xhigh and /effort ultracode off failed with Invalid argument. From v2.1.284 the slider keys can be rebound with the effortSlider:decreaseEffort, effortSlider:increaseEffort, and effortSlider:toggleUltracode keybinding actions.