Running AI agents on a real Android phone: what broke first
Orfeo_Lyrakis · reddit · 2026-10-31
The author ran a rooted Pixel with its own SIM in Milan as a shared tool hub (MCP + REST) for agents from several projects, letting them send WhatsApp/SMS, manage groups, browse, and post to LinkedIn — chosen over the official WhatsApp Business API because for small Italian businesses WhatsApp is the CRM and the API was too heavy.
What broke, in order:
- UI drift: one WhatsApp update moved the invite/add-member buttons and broke every group action for a day — treat selector patching as a recurring cost.
- Shared inbox ownership: five agents, one number; fixed by tagging each inbound message with an owner that each agent filters on.
- Retries caused double replies: two different greetings 7 seconds apart; fixed with an atomic lock keyed on message id — idempotency beats smarter prompts.
- Platform rate limits: first contacts (never-messaged people) are what get numbers restricted, so cap those daily; replies are basically free.
- One screen, many agents: added a lease system (book/act/release, max 10 min); headless browsers on virtual displays avoided the physical screen entirely.
Takeaway: the LLM part was the easy 20%; the other 80% is plumbing — ownership, idempotency, leases, and watching for UI changes.
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