diff --git a/.taskid b/.taskid
index 3d638f2..5e9ca08 100644
--- a/.taskid
+++ b/.taskid
@@ -1 +1 @@
-DEVX-17
+DEVX-18
diff --git a/src/devx/tools/setup.py b/src/devx/tools/setup.py
index fe11708..7243df4 100644
--- a/src/devx/tools/setup.py
+++ b/src/devx/tools/setup.py
@@ -29,10 +29,11 @@ def _install_python_deps(bin_dir: str, extras: str = "dev") -> None:
     """Install the project with the specified extras in editable mode."""
     pip = str(Path(bin_dir) / "pip")
     cmd = [pip, "install", "-e", f".[{extras}]"]
-    # In CI (system Python), --break-system-packages allows upgrading
-    # debian-installed packages (e.g. platformdirs) that lack RECORD files.
+    # In CI (system Python), --break-system-packages allows installing to
+    # system site-packages, and --ignore-installed avoids uninstall failures
+    # for debian-installed packages (e.g. platformdirs) that lack RECORD files.
     if os.environ.get("PIP_BREAK_SYSTEM_PACKAGES") == "1":
-        cmd.append("--break-system-packages")
+        cmd.extend(["--break-system-packages", "--ignore-installed"])
     _run(cmd)
 
 
diff --git a/tests/unit/test_setup.py b/tests/unit/test_setup.py
index 3f3ada6..024bdf5 100644
--- a/tests/unit/test_setup.py
+++ b/tests/unit/test_setup.py
@@ -52,7 +52,9 @@ class TestInstallPythonDeps:
     def test_install_with_break_system_packages(self, mock_run: MagicMock) -> None:
         with patch.dict(os.environ, {"PIP_BREAK_SYSTEM_PACKAGES": "1"}):
             _install_python_deps(".venv/bin", "ci")
-        mock_run.assert_called_once_with([".venv/bin/pip", "install", "-e", ".[ci]", "--break-system-packages"])
+        mock_run.assert_called_once_with(
+            [".venv/bin/pip", "install", "-e", ".[ci]", "--break-system-packages", "--ignore-installed"]
+        )
 
 
 class TestInstallPreCommitHooks: