droidfx-proof

The question

Can an agent run on a phone with no runtime?

droidpi-proof answered it for an agent that ships a runtime. This is the harder version. fx is already a native binary, so nothing needs embedding. The question becomes whether Android lets it act like a program: spawn processes, run a shell, call home over HTTP.

The verdict

WORKS. The fx coding agent, cross-compiled for Android as a static musl binary, ran full agent turns inside a native Kotlin app on an emulator. A prompt came back with a real tool round-trip: the model called terminal exec, uname -m ran in the on-device shell, and the output folded into the final answer. A later milestone added a native OpenRouter provider, also proven on-device.

Three stories from the build:

The proof

The evidence: tool round-trips, both ABIs, the mock gateway, and the OpenRouter follow-up.

The build

The recipe: musl cross-compiles, the seccomp jungle, and four minimal fixes.

Lessons

Probe the sandbox, prove on host first, keep patches small, plus limits and next steps.