[Bug]: Spawned agent CLIs inherit no locale on macOS, corrupting non-ASCII text via pbcopy #6231

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Launch T3 Code from Finder/Dock (not from a terminal — that's what makes the difference).
2. In an agent session, run locale → LANG="", LC_CTYPE="C".
3. Run printf 'Grüße – ß\n' | pbcopy
4. Paste into any app.

Expected behavior

Grüße – ß

Actual behavior

Grüße – ß

UTF-8 decoded as MacRoman: ü (C3 BC) → ü, – (E2 80 93) → –.

Root cause

Agent CLIs are spawned with no LANG/LC_ALL/LC_CTYPE, so their child shells run in the C locale. pbcopy does not pass bytes through — it decodes stdin using the locale encoding, so non-ASCII output is corrupted on the way to the clipboard.

GUI-launched macOS apps inherit a minimal launchd environment with no locale vars. The same claude binary run from a terminal is unaffected, since the terminal supplies the locale.

Impact

Major degradation or frequent failure

Version or commit

0.0.34-nightly.20260811.1068

Environment

macOS (Darwin 25.5.0), Apple Silicon. Launched from Finder/Dock.

Logs or stack traces

# environment of the spawned agent process
$ ps -Ewww -p <claude_pid> | tr ' ' '\n' | grep -E '^(LANG|LC_|__CF)'
__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x3
# (no LANG, LC_ALL, or LC_CTYPE)

$ printf 'Grüße – ß\n' | pbcopy && pbpaste
Grüße – ß

$ printf 'Grüße – ß\n' | LC_ALL=C.UTF-8 pbcopy && pbpaste
Grüße – ß

Screenshots, recordings, or supporting files

No response

Workaround

Set a UTF-8 locale per agent, e.g. "env": { "LANG": "C.UTF-8" } in ~/.claude/settings.json. Each spawned CLI needs its own equivalent.