Diagnosing Tower Git Interactive Rebase Editor Launch Failures

Recognizable Condition

When you start an interactive rebase in Tower (e.g., git rebase -i HEAD~3) the expected editor window does not appear. Tower shows a brief spinner or an error message such as "Editor failed to launch" and the rebase aborts, leaving the repository on the original branch.

Common Causes

Symptom	Likely Cause
No editor window appears; Tower logs show "editor path not set"	Editor path not configured in Tower preferences or core.editor
Editor launches but exits immediately with non‑zero status	Specified executable missing, not executable, or blocked by OS security
Editor opens but Tower treats it as cancelled	Conflicting environment variables (GIT_EDITOR, VISUAL) point to an unavailable program
Tower’s internal log reports sandbox or library errors	macOS Gatekeeper, Windows SmartScreen, or missing shared libraries block the editor

Ordered Diagnostic Steps

1. Check Tower’s editor setting
   • Open Tower → Preferences → Git → Editor.
   • Note the path shown (if any).
2. Verify Git’s core.editor
   • Open a terminal (no admin rights needed).
   • Run git config --global core.editor.
   • If empty, Git falls back to $EDITOR or $VISUAL.
3. Test the editor executable directly
   • In the same terminal, run the exact path from Tower’s setting, e.g. /usr/local/bin/code --wait.
   • Observe whether a window appears and the process returns exit code 0 when you close it.
4. Inspect conflicting environment variables
   • Run echo $GIT_EDITOR and echo $VISUAL.
   • If they are set, repeat the direct‑test step with those values.
5. Review Tower’s internal log
   • Help → Show Logs in Tower.
   • Look for lines containing "editor launch" or "sandbox" around the time you attempted the rebase.

Fixes Tied to Findings

1. Missing or empty editor path

Set a reliable editor in Tower:

1. Preferences → Git → Editor → Choose…
2. Select an executable you know works (e.g., /usr/bin/nano on Linux/macOS, C:\\Program Files\\Git\\usr\\bin\\vim.exe on Windows).
3. If you prefer a GUI editor, use the wrapper that waits for the process to exit (e.g., VS Code: /usr/local/bin/code --wait).
4. Click “Test Editor”; a window should appear and close cleanly.

2. Executable missing or not executable

Make the program available:

• On macOS/Linux, ensure the file exists and is executable: chmod +x /path/to/editor.
• On Windows, verify the .exe is not quarantined by SmartScreen; right‑click → Properties → Unblock if needed.
• Re‑test with Tower’s “Test Editor”.

3. Conflicting environment variables

Either unset the variables or align them with a working editor:

• Temporarily: unset GIT_EDITOR VISUAL (macOS/Linux) or set GIT_EDITOR=& set VISUAL=" (Windows CMD).
• Permanently: edit your shell profile (~/.bashrc, ~/.zshrc) or Windows System → Advanced → Environment Variables.
• After changes, open a new terminal and repeat the diagnostic steps.

4. OS sandbox or security block

Grant Tower permission to launch the editor:

• macOS: System Settings → Privacy & Security → Files and Folders → add Tower (or add the editor to “Allow apps downloaded from”).
• Windows: Windows Security → App & browser control → Reputation-based protection → Disable for the editor or add an exclusion.
• Linux: Usually not an issue; check AppArmor/SELinux logs if present (sudo aa-status or sudo sestatus).

After adjusting permissions, run Tower’s “Test Editor” again.

Escalation Criteria

If after completing the above steps the editor still does not launch:

• Collect Tower’s log excerpt (Help → Show Logs) covering the rebase attempt.
• Note the exact editor path, OS version, and Tower version.
• Contact Tower support with this information; they can diagnose deeper issues such as missing shared libraries or internal sandbox misconfiguration.

Verification

1. After setting a valid editor, use Preferences → Git → Editor → “Test Editor” to confirm a window appears.
2. Run git config --global core.editor in a terminal; it should return the same path.
3. Launch the editor directly from the terminal to ensure it returns exit code 0 when closed.
4. Perform an interactive rebase inside Tower: git rebase -i HEAD~2. Verify the editor opens, you can edit the todo list, and the rebase proceeds after saving and closing.

Limitations

This guide covers the most common editor‑launch failures. It does not address:

• Repository‑specific rebase issues (e.g., malformed commit messages) that cause the editor to open but the rebase to fail later.
• Problems arising from custom Git hooks that interfere with the rebase process.
• Cases where Tower’s internal editor‑invocation code is corrupted; reinstalling Tower may be required.

To verify the result, follow the verification steps above; a successful interactive rebase that completes without error confirms the editor configuration is correct.