A Claude Code environment variable, read out of the shipped bundle.
It has been in the build since v2.1.138, including the newest one read.
Set to 1 to omit the thinking parameter from API requests entirely. This is a compatibility option for proxies and gateways that reject the parameter. On models that think by default, omitting the parameter means the model may still think. To explicitly disable extended thinking on the Anthropic API, use MAX_THINKING_TOKENS=0 instead. Neither variable turns thinking off on Opus 5.5, Sonnet 5.5, or the Fable models, which can't have thinking turned off. On third-party providers, MAX_THINKING_TOKENS=0 likewise omits the parameter, so the two variables behave the same there
v2.1.138in the build not in the build never minedv2.1.308
In the changelogs
0
No changelog entry here has ever named it. That is a statement about what has been written, not about the name: it has been in the build since v2.1.138 without anybody writing a line about it.
First cited
0
No release's published evidence quotes this name. The ledger indexes the Evidence lines of every changelog on this site, so this says nobody here has ever quoted it; it says nothing about how old the name is.
Presence across releases
1
BuildsHow manyDatesReading
v2.1.138 – v2.1.308149 builds9 May 2026 → 22 Oct 2026 ◆in the build
Build by build
149
One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
v2.1.29914 Oct 2026·presentverdict: present · bool
v2.1.30014 Oct 2026·presentverdict: present · bool
v2.1.30115 Oct 2026·presentverdict: present · bool
v2.1.30216 Oct 2026·presentverdict: present · bool
v2.1.30318 Oct 2026·presentverdict: present · bool
v2.1.30419 Oct 2026·presentverdict: present · bool
v2.1.30520 Oct 2026·presentverdict: present · bool
v2.1.30621 Oct 2026·presentverdict: present · bool
v2.1.30721 Oct 2026·presentverdict: present · bool
v2.1.30822 Oct 2026·presentverdict: present · bool
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 environment variable does. All environment variables.
