SupporterBinaries resolves claude/d2/etc. to absolute paths (D-104): an explicit override map first, then the login-shell/process PATH, then the well-known bin dirs incl. Homebrew-on-Linux — the dir the standard PATH expansion omits and a .bashrc-only brew shellenv misses (the D-104 gap). detect() probes those to seed the override map (pinned, not re-probed each launch); isStalePin flags a moved tool. Pure Dart, dart test (11 cases). Settings storage + first-run detect wire on next. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>