Solo Dev Builds Offline Android Agent on a 1B Model With 30 Tools and a Policy Gate

Adventurous-Win6029 · reddit · 2026-09-05

A solo Kotlin developer built an autonomous Android agent powered by a locally running Gemma 3 1B — no API calls, works in airplane mode.
Architecture:
30 tools (flashlight, clipboard, SMS, app launch, web search, navigation of any app via the accessibility tree) with a read-screen → decide → act → verify loop.
Deterministic router: the 1B handles simple commands with zero network latency; anything harder escalates to a 70B cloud model, with no model call needed for routing.
Policy gate: every tool call passes a manifest-checked gate before touching the device; untraced actions are blocked, not logged-and-allowed, with operator taps resolving flagged cases. Ported from a research project benchmarking prompt-injection defenses across 112 models.
Numbers: 134 unit tests, 8/8 device regression suite, 8.7 MB release APK (R8 minified); backgrounded hands-free use verified; deep perception reads 20 screens of an Amazon results page and returns grouped product+price items; named recipes let you teach a multi-step task once and replay it from a fresh conversation.
Honest limits: the 1B echoes few-shot examples (parser handles it), step efficiency in unfamiliar apps is tuned not solved, and voice transcription is only proven on synthetic speech.
The on-device model is switchable (five presets plus custom GGUF); cloud calls use the author's own Venice key.

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