--effort
A Claude Code CLI flag, read out of the shipped bundle. It has been in the build since v2.1.142, including the newest one read.
What it is
Set the [effort level](/docs/en/model-config#adjust-effort-level) for the current session. Options: low, medium, high, xhigh, max, or ultracode. Available levels depend on the model. ultracode starts the session at xhigh effort with [ultracode](/docs/en/workflows#let-claude-decide-with-ultracode) turned on, and requires Claude Code v2.1.203 or later. Overrides the [effortLevel](/docs/en/settings-reference#effortlevel) setting for this session and does not persist
Anthropic's own wording. Read off CLI reference, captured 2026-08-28.
Presence across releases
| Releases | Reading | Declared type | Default |
|---|---|---|---|
| 2.1.245 – 2.1.250 5 releases | never mined | — | — |
| 2.1.142 – 2.1.243 91 releases | in the build | — | — |
A row reading never mined is a release with no archived bundle behind it. Nothing was read out of it, so nothing here says whether the name was in it. A declared type or a default is only ever what that release's own bundle stated.
Changelog entries naming it
-
v2.1.239Session effort becomes a tagged value
Effort is stored as a tagged object, and the effort setting is cleared when no specific level applies.
named in this entry
Documentation pages
- CLI reference reference table Claude Code CLI
- Manage multiple agents with agent view mentions it Claude Code CLI
- Claude Code changelog mentions it Claude Code CLI
- Model configuration mentions it Claude Code CLI
- Claude Code settings mentions it Claude Code CLI
- Example settings files mentions it Claude Code CLI
- Claude Code settings reference mentions it Claude Code CLI
- Week 20 · May 11–15, 2026 mentions it Claude Code CLI
- Orchestrate subagents at scale with dynamic workflows mentions it Claude Code CLI
A reference table page is one whose own table defines this name, and it is where the description above came from. A page that mentions it carries the name somewhere in its text and may say nothing about it at all. Every page carrying it.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the CLI flag does. All CLI flags.