When launched via pythonw.exe (no console), sys.stdout/stderr are None. Accessing .encoding on None raised AttributeError, caught by the GUI's pipeline import guard and shown as 'Failed to load pipeline'. Added None check before the encoding check in fix_console_encoding(), added a test, and documented the pitfall in CLAUDE.md. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>