Agent mode picker for DSH: pick an external Agent CLI (Claude Code, Codex, Qwen Code, Gemini CLI, Aider, Goose, Hermes…) as the session's default executor from a control next to the input box, instead of editing configuration files. The agent roster is data-driven, and installed CLIs are discovered automatically from PATH, the managed CLI directory and a drop-in convention directory. Agents that are installed but still missing credentials or a required background service are shown as "needs setup" rather than silently hidden.