One Sentence, 6 Minutes: Open-Source Buddy App Runs Claude Code On-Phone to Build Android Apps
3amae404 · reddit · 2026-10-23
A developer released Buddy, a free open-source (Apache 2.0) Android app that runs Claude Code on-device via a small Alpine Linux in proot, exposing phone tools (read screen, tap, type, install apps) over a local MCP server.
From one prompt—"build and install a Pac-Man style maze game with ghosts and touch controls"—Opus 5.5 delivered in 6 minutes:
- A skill guides on-phone builds: no Gradle, plain Java + the Android framework with aapt2, d8 and apksigner (400 MB tooling on first run)
- It wrote a single 660-line Java file: maze, four ghosts, power pellets, lives, high score, D-pad and swipe controls
- It built the APK, installed it (Android requires user confirmation), then opened the game, read the screen, spotted a 0-lives bug on first launch, fixed it, rebuilt and asked for confirmation again
Lessons: keep the skill strict (plain Java, code-built UI, no AppCompat—XML layouts and missing libs break builds); let the agent test on the real device (the 0-lives bug compiled fine and was only caught visually); installs always need a human tap per Android rules.
Repo: ghorbelhamdi/buddy-android. The GitHub APK includes developer mode; the Play version omits it.
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