CLAUDE_CODE_LEGACY_BUNDLE
A Claude Code environment variable, read out of the shipped bundle. It has been in the build since v2.1.242, including the newest one read.
Set CLAUDE_CODE_LEGACY_BUNDLE to true to go back to the old single-file build shape.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.242.
In the changelogs
5Releases whose published page names CLAUDE_CODE_LEGACY_BUNDLE.
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v2.1.285
Cloud sessions no longer sync or seed your folder, and
CLAUDE_CODE_DIR_SYNC_ENGINEis ignoredStarting a cloud session no longer uses folder sync or seeding,
CLAUDE_CODE_DIR_SYNC_ENGINEis not read, and bundle upload remainsfound in this entry's text
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v2.1.285
CLAUDE_CODE_LEGACY_BUNDLE no longer works on macOS and Linux
On macOS and Linux,
CLAUDE_CODE_LEGACY_BUNDLEis now ignored with a warning and the default upload method runs; only Windows keeps itfound in this entry's text, named in this entry
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v2.1.285
CLAUDE_CODE_LEGACY_BUNDLEdropped from a list of cloud bundling variablesOne list of bundling environment variables now holds only
CCR_ENABLE_BUNDLEandCCR_FORCE_BUNDLEfound in this entry's text, named in this entry
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v2.1.281
CLAUDE_CODE_LEGACY_BUNDLE is ignored when a project settings file sets it
CLAUDE_CODE_LEGACY_BUNDLE is ignored with a warning when it comes from a settings file rather than your launch environment or own settings
found in this entry's text, named in this entry
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v2.1.242
CLAUDE_CODE_LEGACY_BUNDLE restores the old non-split bundle shape
Set CLAUDE_CODE_LEGACY_BUNDLE to true to go back to the old single-file build shape.
named in this entry, found in this entry's text
First cited
4The earliest release whose published evidence quoted CLAUDE_CODE_LEGACY_BUNDLE was v2.1.242, 24 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
1Build by build
57One 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.