CLAUDE_CODE_CARVED_SLATE
A Claude Code environment variable, read out of the shipped bundle. It was in the build from v2.1.251 and was gone by v2.1.268.
A mode keeps the system prompt static and moves environment details into conversation reminders, off by default.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.251.
In the changelogs
2Releases whose published page names CLAUDE_CODE_CARVED_SLATE.
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v2.1.252
New "instructionFiles" context channel, gated behind carved-slate flag
A separate instruction-files context channel exists but is off by default, part of a static system prompt rework.
named in this entry, found in this entry's text
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v2.1.251
A stripped-down system prompt mode, off in this build
A mode keeps the system prompt static and moves environment details into conversation reminders, off by default.
named in this entry, found in this entry's text
First cited
1The earliest release whose published evidence quoted CLAUDE_CODE_CARVED_SLATE was v2.1.251, 28 Aug 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.
Presence across releases
2Build by build
61One 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.
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.