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 strip Anthropic-specific anthropic-beta request headers and beta tool-schema fields (such as defer_loading and eager_input_streaming) from API requests. Use this when a proxy gateway rejects requests with errors like "Unexpected value(s) for the anthropic-beta header" or "Extra inputs are not permitted". Standard fields (name, description, input_schema, cache_control) are preserved. MCP tool search is disabled and all MCP tools load upfront, even when you set ENABLE_TOOL_SEARCH. On Claude Code v2.1.227 or later, managed settings can keep tool search on. Disable pre-release capabilities covers where the override applies
The earliest release whose published evidence quoted CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS was v2.1.123, 29 Apr 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
v2.1.28224 Sep 2026when experimental betas are off (CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS or organization policy)
v2.1.28529 Sep 2026experimental betas are off (CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS or organization policy)
Presence across releases
1
BuildsHow manyDatesReading
v2.1.138 – v2.1.309150 builds9 May 2026 → 22 Oct 2026 ◆in the build
Build by build
150
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
v2.1.30922 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.
