Anchor

A mobile-first Android app for monitoring and interacting with remote tmux sessions over SSH. Not a terminal emulator — a chat-like interface that views tmux pane content via tmux capture-pane and sends input via tmux send-keys.

Features

• Managed host list — save hosts with label, hostname, port, and username; persisted locally via Room database
• SSH key management — generate ECDSA keys and deploy them to saved hosts via password auth
• Host key verification — fingerprint checking with persistent known_hosts storage; warns on new or changed keys
• Tmux session browser — lists active tmux sessions on the connected host
• Session viewer — chat-style display of tmux pane content with a command input bar
• Adaptive pane sizing — resizes the tmux window to fit your phone screen based on font size and orientation
• Configurable font size — adjustable in-session with +/- controls; persists across sessions

Requirements

• Android 8.0+ (API 26)
• A remote server with tmux installed and SSH access

Building

The build environment runs in Docker:

docker compose up -d
docker compose exec build ./gradlew assembleDebug

Install to a connected device or emulator:

adb install -r app/build/outputs/apk/debug/app-debug.apk

Emulator setup (Linux with KVM)

The emulator runs on the host (not in Docker) for GPU/KVM support. Install the emulator and system image once:

sdkmanager --install "emulator" "system-images;android-35;google_apis;x86_64"

Then bootstrap everything else with:

./scripts/setup-emulator.sh

The script is idempotent and handles the parts that are easy to get wrong:

• Creates the anchor AVD (pixel_9, android-35) if it doesn't exist
• Forces host GPU rendering (hw.gpu.enabled=yes, hw.gpu.mode=host) — without this the emulator software-renders the entire screen and crawls even on fast machines — and enables the hardware keyboard
• Boots the emulator and waits for it
• Sets a screen-lock PIN (1111) and enrolls a virtual fingerprint by driving the Settings wizard via uiautomator. Without an enrolled fingerprint, Anchor's biometric-gated key generation silently refuses to run.
• Disables the first-focus stylus promo popup and keeps the screen awake so the emulator never sleeps or re-locks between interactions

Whenever the app shows a fingerprint prompt, simulate a sensor touch with:

adb emu finger touch 1

To test against the host machine from inside the emulator, use hostname 10.0.2.2 (the emulator's alias for the host loopback).

Usage

1. Set up SSH key — tap the key icon in the top bar, generate a key, then deploy it to a saved host
2. Add a host — tap the + button, enter label/hostname/username
3. Connect — tap a saved host to connect and see its tmux sessions
4. View a session — tap a session to see its pane content; type commands in the input bar at the bottom

Known issues

Tmux window resizing

Anchor resizes the tmux window to match your phone's screen width so content fits without overflow. This means if you have the same tmux session open on a desktop terminal, it will appear narrow while the phone is actively viewing it.

When you leave the session view or disconnect, Anchor automatically restores automatic sizing (it unsets the per-window window-size option that tmux resize-window implicitly sets to manual), so attached desktop terminals snap back to their own size.

If Anchor is killed while viewing a session (so the restore never runs), windows stay stuck at the phone size. Fix it from any shell on the host:

tmux list-windows -t <session> -F '#{window_id}' | xargs -I{} tmux set-option -w -t {} -u window-size

Note that tmux resize-window -A is not sufficient — it restores the size once but leaves window-size set to manual, so auto-resize stays broken.

Architecture

• Kotlin + Jetpack Compose — Material 3 UI
• JSch (mwiede fork) — SSH connections
• BouncyCastle — ECDSA key generation
• Room — local host database
• Stateless polling — captures pane content periodically via tmux capture-pane -p; no persistent terminal session or mosh required

License

MIT — see LICENSE.