Bundled Git cannot find macOS git-credential-osxkeychain helper

What happened?

When Codex runs git push from a local repo on macOS with credential.helper=osxkeychain, it uses the bundled Git from the Codex runtime instead of the system Git.

That bundled Git cannot invoke the macOS credential helper:

git: 'credential-osxkeychain' is not a git command. See 'git --help'.
fatal: could not read Username for 'https://<git-host>': Device not configured

Running the same git push manually in a normal terminal succeeds.

Environment

• Codex desktop app on macOS
• Git remote over HTTPS
• Global Git config: credential.helper=osxkeychain

In the Codex shell:

command -v git
~/.cache/codex-runtimes/codex-primary-runtime/dependencies/bin/git

git --version
git version 2.53.0

git --exec-path
~/.cache/codex-runtimes/codex-primary-runtime/dependencies/native/git/libexec/git-core

The system Git works and has the macOS helper available:

/usr/bin/git --version
git version 2.39.5 (Apple Git-154)

/usr/bin/git --exec-path
/Library/Developer/CommandLineTools/usr/libexec/git-core

/Library/Developer/CommandLineTools/usr/libexec/git-core/git-credential-osxkeychain

Expected behavior

Codex Git operations should either:

• use the system Git credential helper when the user's Git config references it,
• include or discover a compatible macOS git-credential-osxkeychain helper, or
• document/recommend how to configure the Codex shell to use system Git or compatible credentials.

Workaround

Explicitly run /usr/bin/git push ... from Codex, or push manually in Terminal.

Related

This is similar in spirit to authentication/keychain environment issues such as #10695, but this report is specifically about the bundled Git not finding the macOS osxkeychain credential helper.