fix: harden restart_claude_desktop across platforms (#33)

- Linux (and any non-desktop platform): refuse instead of 'pkill claude',
  which substring-matched running Claude Code CLI sessions and relaunched
  the CLI, not a desktop app. New restart_supported() gates the button.
- macOS: wait (<=5s) for the old instance to exit before 'open -a Claude'
  so the relaunch can't re-activate the dying process. Runs off the UI
  thread via a RestartWorker.
- Windows: verify the Start-menu shortcut exists BEFORE taskkill, so an
  MSIX/Store install is never killed without a relaunch path.

Closes #33

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bcc.py

@@ -1423,6 +1423,17 @@ class AboutDialog(QDialog):
         QDesktopServices.openUrl(QUrl(self._release_url or core.RELEASES_URL))
 
 
+# --------------------------------------------------------------------------- #
+# Restart worker: core.restart_claude_desktop() blocks up to ~5 s on macOS
+# waiting for the old instance to exit, so it must run off the UI thread.
+# --------------------------------------------------------------------------- #
+class RestartWorker(QThread):
+    done = Signal(object)  # core.RestartResult
+
+    def run(self):
+        self.done.emit(core.restart_claude_desktop())
+
+
 # --------------------------------------------------------------------------- #
 # Main window
 # --------------------------------------------------------------------------- #
@@ -2284,18 +2295,30 @@ class MainWindow(QMainWindow):
     def _offer_restart_button(self):
         """Show the 'Restart Claude Desktop' button after a successful save,
         but only when the just-saved profile is Claude Desktop -- restarting
-        makes no sense for Claude Code, which has no GUI process to bounce."""
+        makes no sense for Claude Code, which has no GUI process to bounce --
-        if self.current_profile and core.profile_targets_claude_desktop(self.current_profile):
+        and only on platforms where Claude Desktop exists (never Linux, where
+        'claude' is the Claude Code CLI)."""
+        if (
+            self.current_profile
+            and core.profile_targets_claude_desktop(self.current_profile)
+            and core.restart_supported()
+        ):
             self.restart_btn.show()
         else:
             self.restart_btn.hide()
 
     def _restart_claude_desktop(self):
         self.restart_btn.setEnabled(False)
-        try:
+        self.restart_btn.setText("Restarting…")
-            result = core.restart_claude_desktop()
+        # Held on self (MainWindow outlives the worker); replaced only after
-        finally:
+        # done re-enables the button, so a running thread is never dropped.
-            self.restart_btn.setEnabled(True)
+        self._restart_worker = RestartWorker()
+        self._restart_worker.done.connect(self._on_restart_done)
+        self._restart_worker.start()
+
+    def _on_restart_done(self, result):
+        self.restart_btn.setEnabled(True)
+        self.restart_btn.setText("Restart Claude Desktop")
         self.restart_btn.hide()
         if result.success:
             self.status.setText(f"{self.status.text()}  ·  {result.detail}")

bcc_core.py

@@ -1837,8 +1837,41 @@ def _run_quiet(cmd: list[str]) -> None:
         subprocess.run(cmd, capture_output=True)
 
 
+def restart_supported() -> bool:
+    """
+    True only where restarting Claude Desktop makes sense (macOS, Windows).
+    There is no official Claude Desktop for Linux, and the obvious binary
+    name there ("claude") is the Claude Code CLI — killing or spawning it
+    would be actively harmful. GUI callers gate the Restart button on this.
+    """
+    return sys.platform == "darwin" or sys.platform.startswith("win")
+
+
+_MACOS_QUIT_WAIT_S = 5.0
+
+
+def _macos_claude_running() -> bool:
+    try:
+        return subprocess.run(["pgrep", "-x", "Claude"], capture_output=True).returncode == 0
+    except OSError:
+        return False
+
+
 def _restart_claude_desktop_macos() -> RestartResult:
     _run_quiet(["pkill", "-x", "Claude"])
+    # Wait for the old instance to actually exit: `open -a` against a dying
+    # process can merely re-activate it, and the config is only re-read on a
+    # true relaunch. Blocks up to _MACOS_QUIT_WAIT_S — callers run this off
+    # the UI thread (see RestartWorker in bcc.py).
+    deadline = time.monotonic() + _MACOS_QUIT_WAIT_S
+    while _macos_claude_running():
+        if time.monotonic() > deadline:
+            return RestartResult(
+                False,
+                f"Claude Desktop didn't quit within {_MACOS_QUIT_WAIT_S:.0f}s — "
+                "quit it manually, then reopen it.",
+            )
+        time.sleep(0.15)
     try:
         result = subprocess.run(["open", "-a", "Claude"], capture_output=True, text=True)
     except OSError as e:
@@ -1855,8 +1888,18 @@ def _claude_windows_start_menu_shortcut() -> Path:
 
 
 def _restart_claude_desktop_windows() -> RestartResult:
-    _run_quiet(["taskkill", "/IM", "Claude.exe", "/F"])
     shortcut = _claude_windows_start_menu_shortcut()
+    if not shortcut.is_file():
+        # Checked BEFORE killing: an MSIX/Store install has no Start-menu .lnk
+        # at this path, and killing without a relaunch path would leave the
+        # user with no running Claude at all.
+        return RestartResult(
+            False,
+            f"Claude's Start-menu shortcut wasn't found ({shortcut}). "
+            "If Claude Desktop is installed from the Microsoft Store, "
+            "quit and reopen it manually.",
+        )
+    _run_quiet(["taskkill", "/IM", "Claude.exe", "/F"])
     try:
         # `cmd /c start "" <target>` launches detached, the same as double-clicking
         # the Start-menu shortcut, and returns immediately.
@@ -1873,32 +1916,19 @@ def _restart_claude_desktop_windows() -> RestartResult:
     return RestartResult(True, "Claude Desktop restarted.")
 
 
-def _restart_claude_desktop_linux() -> RestartResult:
-    _run_quiet(["pkill", "claude"])
-    try:
-        # The Linux launcher is the app itself (no "open"-style helper), so it
-        # has to be started detached rather than waited on.
-        subprocess.Popen(
-            ["claude"],
-            stdin=subprocess.DEVNULL,
-            stdout=subprocess.DEVNULL,
-            stderr=subprocess.DEVNULL,
-            start_new_session=True,
-        )
-    except OSError as e:
-        return RestartResult(False, f"Couldn't launch Claude Desktop: {e}")
-    return RestartResult(True, "Claude Desktop restarted.")
-
-
 def restart_claude_desktop() -> RestartResult:
     """
     Kill and relaunch the Claude Desktop app so a freshly saved config takes
     effect. The app not currently running is NOT a failure -- pkill/taskkill
     exiting non-zero just means "nothing to kill", and we go straight to
     relaunching. Only a failed relaunch is reported as success=False.
+
+    macOS blocks for up to _MACOS_QUIT_WAIT_S while the old instance exits —
+    run off the UI thread. Unsupported platforms (see restart_supported())
+    refuse without touching any process.
     """
     if sys.platform == "darwin":
         return _restart_claude_desktop_macos()
     if sys.platform.startswith("win"):
         return _restart_claude_desktop_windows()
-    return _restart_claude_desktop_linux()
+    return RestartResult(False, "Restarting Claude Desktop isn't supported on this platform.")

tests/test_core.py

@@ -934,11 +934,13 @@ class _FakeCompletedProcess:
 
 
 def test_restart_claude_desktop_macos_commands(monkeypatch):
-    """macOS: pkill -x "Claude" then open -a Claude, in that order."""
+    """macOS: pkill -x "Claude", wait for exit (pgrep), then open -a Claude."""
     calls = []
 
     def fake_run(cmd, **kwargs):
         calls.append(cmd)
+        if cmd[0] == "pgrep":
+            return _FakeCompletedProcess(returncode=1)  # already exited
         return _FakeCompletedProcess(returncode=0)
 
     monkeypatch.setattr(c.sys, "platform", "darwin")
@@ -946,14 +948,14 @@ def test_restart_claude_desktop_macos_commands(monkeypatch):
     result = c.restart_claude_desktop()
     assert result.success
     assert calls[0] == ["pkill", "-x", "Claude"]
-    assert calls[1] == ["open", "-a", "Claude"]
+    assert calls[-1] == ["open", "-a", "Claude"]
 
 
 def test_restart_claude_desktop_macos_pkill_not_running_is_fine(monkeypatch):
     """pkill exiting non-zero (nothing to kill) must NOT be treated as failure."""
 
     def fake_run(cmd, **kwargs):
-        if cmd[0] == "pkill":
+        if cmd[0] in ("pkill", "pgrep"):
             return _FakeCompletedProcess(returncode=1)  # no matching process
         return _FakeCompletedProcess(returncode=0)
 
@@ -977,12 +979,12 @@ def test_restart_claude_desktop_macos_relaunch_failure_reported(monkeypatch):
 
 
 def test_restart_claude_desktop_macos_pkill_binary_missing_does_not_raise(monkeypatch):
-    """pkill raising OSError (binary missing) must be swallowed, not propagated --
+    """pkill/pgrep raising OSError (binary missing) must be swallowed, not
-    relaunch is still attempted."""
+    propagated -- relaunch is still attempted."""
 
     def fake_run(cmd, **kwargs):
-        if cmd[0] == "pkill":
+        if cmd[0] in ("pkill", "pgrep"):
-            raise OSError("pkill not found")
+            raise OSError("binary not found")
         return _FakeCompletedProcess(returncode=0)
 
     monkeypatch.setattr(c.sys, "platform", "darwin")
@@ -991,7 +993,45 @@ def test_restart_claude_desktop_macos_pkill_binary_missing_does_not_raise(monkey
     assert result.success
 
 
-def test_restart_claude_desktop_windows_commands(monkeypatch):
+def test_restart_claude_desktop_macos_gives_up_if_app_wont_quit(monkeypatch):
+    monkeypatch.setattr(c.sys, "platform", "darwin")
+    monkeypatch.setattr(c, "_run_quiet", lambda cmd: None)
+    monkeypatch.setattr(c, "_macos_claude_running", lambda: True)  # never exits
+    monkeypatch.setattr(c, "_MACOS_QUIT_WAIT_S", 0.2)
+    res = c.restart_claude_desktop()
+    assert res.success is False
+    assert "quit" in res.detail.lower()
+
+
+def test_restart_claude_desktop_macos_waits_for_exit_then_relaunches(monkeypatch):
+    monkeypatch.setattr(c.sys, "platform", "darwin")
+    monkeypatch.setattr(c, "_run_quiet", lambda cmd: None)
+    alive = iter([True, True, False])  # exits on the third poll
+    monkeypatch.setattr(c, "_macos_claude_running", lambda: next(alive))
+
+    launched = []
+
+    def fake_run(cmd, **kwargs):
+        launched.append(cmd)
+        return _FakeCompletedProcess(returncode=0)
+
+    monkeypatch.setattr(c.subprocess, "run", fake_run)
+    res = c.restart_claude_desktop()
+    assert res.success is True
+    assert launched == [["open", "-a", "Claude"]]
+
+
+@pytest.fixture
+def windows_shortcut(tmp_path, monkeypatch):
+    """A fake %APPDATA% containing the Claude Start-menu shortcut."""
+    monkeypatch.setenv("APPDATA", str(tmp_path))
+    lnk = tmp_path / "Microsoft" / "Windows" / "Start Menu" / "Programs" / "Claude.lnk"
+    lnk.parent.mkdir(parents=True)
+    lnk.write_bytes(b"")
+    return lnk
+
+
+def test_restart_claude_desktop_windows_commands(monkeypatch, windows_shortcut):
     """Windows: taskkill the process, then relaunch via the Start-menu shortcut."""
     calls = []
 
@@ -1008,7 +1048,7 @@ def test_restart_claude_desktop_windows_commands(monkeypatch):
     assert calls[1][-1].endswith("Claude.lnk")
 
 
-def test_restart_claude_desktop_windows_relaunch_failure_reported(monkeypatch):
+def test_restart_claude_desktop_windows_relaunch_failure_reported(monkeypatch, windows_shortcut):
     def fake_run(cmd, **kwargs):
         if cmd[0] == "cmd":
             return _FakeCompletedProcess(returncode=1, stderr="not found")
@@ -1021,43 +1061,37 @@ def test_restart_claude_desktop_windows_relaunch_failure_reported(monkeypatch):
     assert "not found" in result.detail
 
 
-def test_restart_claude_desktop_linux_commands(monkeypatch):
+def test_restart_claude_desktop_windows_missing_shortcut_refuses_before_killing(
-    """Linux: pkill claude, then relaunch via a detached Popen (no waiting)."""
+    monkeypatch, tmp_path
-    run_calls = []
+):
-    popen_calls = []
+    killed = []
+    monkeypatch.setattr(c, "_run_quiet", lambda cmd: killed.append(cmd))
+    monkeypatch.setattr(c.sys, "platform", "win32")
+    monkeypatch.setenv("APPDATA", str(tmp_path))  # no Claude.lnk under here (MSIX case)
+    res = c.restart_claude_desktop()
+    assert res.success is False
+    assert "shortcut" in res.detail.lower()
+    assert killed == []  # Claude must NOT be killed when it can't be relaunched
 
-    def fake_run(cmd, **kwargs):
-        run_calls.append(cmd)
-        return _FakeCompletedProcess(returncode=0)
-
-    class _FakePopen:
-        def __init__(self, cmd, **kwargs):
-            popen_calls.append((cmd, kwargs))
 
+def test_restart_supported_only_on_desktop_platforms(monkeypatch):
+    monkeypatch.setattr(c.sys, "platform", "darwin")
+    assert c.restart_supported()
+    monkeypatch.setattr(c.sys, "platform", "win32")
+    assert c.restart_supported()
     monkeypatch.setattr(c.sys, "platform", "linux")
-    monkeypatch.setattr(c.subprocess, "run", fake_run)
+    assert not c.restart_supported()
-    monkeypatch.setattr(c.subprocess, "Popen", _FakePopen)
-    result = c.restart_claude_desktop()
-    assert result.success
-    assert run_calls == [["pkill", "claude"]]
-    cmd, kwargs = popen_calls[0]
-    assert cmd == ["claude"]
-    assert kwargs.get("start_new_session") is True
 
 
-def test_restart_claude_desktop_linux_popen_failure_reported(monkeypatch):
+def test_restart_claude_desktop_linux_refuses_without_touching_processes(monkeypatch):
-    def fake_run(cmd, **kwargs):
+    """There is no Claude Desktop on Linux; 'pkill claude' would substring-match
-        return _FakeCompletedProcess(returncode=0)
+    running Claude Code CLI sessions. The restart must refuse outright."""
-
+    killed = []
-    def fake_popen(cmd, **kwargs):
+    monkeypatch.setattr(c, "_run_quiet", lambda cmd: killed.append(cmd))
-        raise OSError("no such file or directory")
-
     monkeypatch.setattr(c.sys, "platform", "linux")
-    monkeypatch.setattr(c.subprocess, "run", fake_run)
+    res = c.restart_claude_desktop()
-    monkeypatch.setattr(c.subprocess, "Popen", fake_popen)
+    assert res.success is False
-    result = c.restart_claude_desktop()
+    assert killed == []  # nothing killed, nothing spawned
-    assert not result.success
-    assert "Claude Desktop" in result.detail
 
 
 # --------------------------------------------------------------------------- #