[FEATURE] Tell the model whether each message came from mobile (Remote Control) or the desktop

Request

Tell the model, on each user message, which client it was sent from: the desktop/terminal session itself, or the mobile app / claude.ai through Remote Control. For example a short system note or a field in the turn metadata such as "sent from: mobile (Remote Control)".

Why

I use the same session from my Mac and from my phone. On the phone, long replies, wide tables, code blocks and file paths are hard to read; on the desktop they are fine. Today the model has no way to know where I am, so it formats every reply the same. If it knew the source of each message, my CLAUDE.md could say "on mobile, keep it short and skip tables", and it would just work. Hooks (UserPromptSubmit) also do not receive this information, so there is no workaround.

Environment

Claude Code 2.1.286 (Claude Code), Claude Desktop app + Claude iOS app, macOS 26.6, Max plan.