A Claude Code environment variable, read out of the shipped bundle.
It has been in the build since v2.1.179, including the newest one read.
When true, OpenTelemetry diagnostic errors are also written to stderr with the prefix [3P telemetry] OTEL diag error:, in addition to the debug log. Claude Code sets it to 1 in the environment of the sessions it launches with CLAUDE_CODE_ENVIRONMENT_KIND set to byoc.
Not Anthropic's. Written by Claude Opus 5.5 from reading the v2.1.286 bundle, and it can be wrong.
First seen v2.1.179 16 Jun 2026
Last seen v2.1.309 22 Oct 2026
Builds113 / 150on this box, as of v2.1.309
Written about v2.1.179 first named in a changelog, 16 Jun 2026
v2.1.179in the build not in the build never minedv2.1.309
In the changelogs
1
Releases whose published page names CLAUDE_CODE_OTEL_DIAG_STDERR.
The earliest release whose published evidence quoted CLAUDE_CODE_OTEL_DIAG_STDERR was v2.1.179, 16 Jun 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.
v2.1.179 – v2.1.309113 builds16 Jun 2026 → 22 Oct 2026 ◆in the build
Build by build
113
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.
