A Claude Code environment variable, read out of the shipped bundle.
It has been in the build since v2.1.217, including the newest one read.
Boolean (1, true, yes or on). When true, it forces the amber_astrolabe model capability on, which adds the system prompt section that opens You are operating autonomously. and tells the model to carry on with reversible actions without asking. The section still needs the tengu_amber_sextant flag (default true). When unset or false, the capability comes from the model's capability data, and the same section is also added for models with the fable_5_mitigations capability (on by default for claude-mythos-5).
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.286 bundle, and it can be wrong.
First seen v2.1.217 21 Jul 2026
Last seen v2.1.308 22 Oct 2026
Builds80 / 149on this box, as of v2.1.308
Written about v2.1.217 first named in a changelog, 21 Jul 2026
v2.1.217in the build not in the build never minedv2.1.308
In the changelogs
1
Releases whose published page names CLAUDE_CODE_AMBER_ASTROLABE.
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
v2.1.217 – v2.1.30880 builds21 Jul 2026 → 22 Oct 2026 ◆in the build
Build by build
80
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.
