/termux-safe

name: termux-safe
description: Android/Termux constraints reference. Prevents Claude Code from suggesting commands that fail silently on Android (sudo, systemd, non-Termux paths, etc.).
user-invocable: false
disable-model-invocation: false
# No allowed-tools field: this skill is content-only and grants no additional tool access.

Android / Termux Environment Constraints

> **Scope and when this applies.** These constraints apply when you are executing inside Termux on Android, regardless of how Claude Code itself was packaged. The load-bearing runtime signal is `$PREFIX === "/data/data/com.termux/files/usr"`. If that environment variable points at Termux's prefix, you are in Termux and these constraints apply, even if `process.platform` reports `"linux"` (it will report `"linux"` if Claude Code was installed via this repo's v2.9.0 Path A, which runs the linux-arm64 binary patched via glibc-runner; it will report `"android"` only on older Path A v2.x installs that used the JS bundle). If `$PREFIX` is unset or points at `/usr`, you are inside a chroot-like sandbox (for example, a Linux rootfs running under `proot-distro`, Path B) or inside a hypervisor-managed Linux VM (Path C), and standard Linux conventions apply; most of this file does not.

If the runtime signals indicate the in-Termux case, the constraints below produce **silent failures, not errors.** Every suggestion must account for them.

Hard Rules: Never Suggest These

• **No `sudo`.** Root does not exist. No `su`, no `doas`, no privilege escalation of any kind.
• **No `systemctl` or `systemd`.** Android does not use systemd. No `journalctl`, no `service`, no unit files.
• **No standard Linux paths.** `/usr/bin`, `/etc`, `/var` do not exist or are not writable. Termux paths:
• Home: `/data/data/com.termux/files/home`
• Prefix: `/data/data/com.termux/files/usr`
• Binaries: `$PREFIX/bin`
• Config: `$PREFIX/etc`
• **No ports below 1024.** No root = no binding to 80, 443, etc. Use 1024+.
• **Prefer `pkg` over `apt`.** Both work, but `pkg` auto-updates the package index before installing.
• **No Docker, no containers.** The kernel does not support them without root.

Silent Failure Modes

• **Node.js is not required by this repo's `install.sh`.** The patched linux-arm64 claude binary is self-contained. If Node is installed separately on native Termux, prefer v25+: v24 had a documented startup hang on ARM64 that was resolved in v25.
• **File descriptor limits vary by device.** Check with `ulimit -n`. Avoid spawning many concurrent processes.
• **Android phantom process killer** limits background processes to ~32 across all apps. If "Disable child process restrictions" is enabled in Developer Options, this limit is lifted; 6 concurrent subagents have been observed stable in testing. Otherwise limit to 2-3.
• **`process.platform` reporting varies by install path.** On Path A v2.9.0 (the linux-arm64 binary patched via glibc-runner), Node.js reports `process.platform === "linux"` even though you are inside Termux. On older Path A v2.x (the JS-bundle npm install) it reports `"android"`. On Path B (proot-distro Ubuntu) and Path C (AVF), it reports `"linux"` and you are not in Termux. The reliable cross-path signal that you are still in Termux is `$PREFIX === "/data/data/com.termux/files/usr"`.

Package Installation

Prefer `pkg` (auto-updates the index before install). `apt` and `apt-get` also work but skip the auto-update:

pkg install <package> -y
pkg upgrade
pkg search <query>

When Unsure

If you're about to suggest a command that assumes standard Linux, stop and verify it works on Termux first. When in doubt, prefix with `command -v <tool> >/dev/null 2>&1` to check availability.