Before writing config.toml (Codex) or opencode.json (OpenCode), the CLI
attempts to create a timestamped backup of any existing config file.
This prevents accidental data loss when users have customized configs.
Backup is best-effort - if it fails (e.g., unusual permissions), the
install continues without blocking.
Backup files are named: config.toml.bak.2026-01-23T21-16-40-065Z