All tests run on an 8-year-old MacBook Air.

My Swift CLI binary worked perfectly from the terminal.

Inside Tauri, it silently failed. No error. No output. Nothing.

Two days later I found the problem: sandbox permissions.

What Tauri's sandbox blocks by default

Tauri apps run in a macOS sandbox. Out of the box, your app cannot:

• Execute external binaries
• Access files outside a small set of allowed paths
• Open network sockets (unless explicitly allowed)
• Write to arbitrary disk locations

All of these fail silently unless you know to look.

The fix: capabilities config

In Tauri v2, permissions live in src-tauri/capabilities/:

{
  "identifier": "main-capability",
  "description": "Main window permissions",
  "windows": ["main"],
  "permissions": [
    "shell:allow-execute",
    "shell:allow-stdin",
    "fs:allow-read-files",
    "fs:allow-write-files",
    "fs:allow-app-cache-write"
  ]
}

shell:allow-execute is what unlocks external binary execution. Without it, Command::new() returns nothing — no error, just silence.

The silent failure problem

The worst part isn't that it fails. It's that it fails quietly.

// This returns Ok(output) even when sandbox blocks it
// output.stdout is just empty
let output = Command::new("my-binary").output()?;

// You need to check stderr AND status code
if !output.status.success() {
    eprintln!("stderr: {}", String::from_utf8_lossy(&output.stderr));
}

Always check output.status.success() and output.stderr. The sandbox doesn't propagate errors the way you'd expect.

Lesson

Read the Tauri v2 capabilities docs before you write a single line of shell integration code. I didn't. It cost me two days.

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