diff --git a/myagents/commands/uninstall.py b/myagents/commands/uninstall.py
index 4bef9bd..515aa45 100644
--- a/myagents/commands/uninstall.py
+++ b/myagents/commands/uninstall.py
@@ -57,10 +57,16 @@ def _remove_path(path: Path, removed: list[Path]) -> None:
 
 def _pip_uninstall() -> list[str]:
     """Uninstall the pip packages (removes their pip-owned entry points)."""
+    import sysconfig
+
     if os.environ.get("VIRTUAL_ENV") and shutil.which("uv"):
         base = ["uv", "pip", "uninstall"]
     else:
-        base = [sys.executable, "-m", "pip", "uninstall", "-y"]
+        base = [sys.executable, "-m", "pip", "uninstall"]
+        stdlib = Path(sysconfig.get_path("stdlib"))
+        if (stdlib / "EXTERNALLY-MANAGED").exists():
+            base.append("--break-system-packages")
+        base.append("-y")
     warnings: list[str] = []
     for pkg in PY_PACKAGES:
         result = subprocess.run([*base, pkg], capture_output=True, text=True)
diff --git a/myagents/commands/upgrade.py b/myagents/commands/upgrade.py
index 87cebcc..225e6b1 100644
--- a/myagents/commands/upgrade.py
+++ b/myagents/commands/upgrade.py
@@ -147,11 +147,18 @@ def _extract(tarball: Path, dest: Path) -> None:
 
 def _pip_install(pkg_dir: Path) -> subprocess.CompletedProcess:
     import os
+    import sysconfig
 
     if os.environ.get("VIRTUAL_ENV") and shutil.which("uv"):
         cmd = ["uv", "pip", "install", "-e", str(pkg_dir), "--quiet"]
     else:
-        cmd = [sys.executable, "-m", "pip", "install", "-e", str(pkg_dir), "--quiet"]
+        cmd = [sys.executable, "-m", "pip", "install"]
+        # Ubuntu 24.04+ marks the system Python externally-managed (PEP 668);
+        # without the flag pip refuses to install there at all.
+        stdlib = Path(sysconfig.get_path("stdlib"))
+        if (stdlib / "EXTERNALLY-MANAGED").exists():
+            cmd.append("--break-system-packages")
+        cmd += ["-e", str(pkg_dir), "--quiet"]
     return subprocess.run(cmd, capture_output=True, text=True)
 
 
diff --git a/tests/test_upgrade.py b/tests/test_upgrade.py
index 813b369..cb79967 100644
--- a/tests/test_upgrade.py
+++ b/tests/test_upgrade.py
@@ -230,3 +230,41 @@ class TestFetch:
         dest = tmp_path / "out.tar.gz"
         up_mod._download("http://x/f", "u", "p", dest)
         assert dest.read_bytes() == payload
+
+
+class TestPipInstallFlags:
+    def test_uses_break_system_packages_on_externally_managed(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        import sysconfig
+
+        em = tmp_path / "EXTERNALLY-MANAGED"
+        em.write_text("[externally-managed]\n")
+        monkeypatch.setattr(
+            sysconfig, "get_path", lambda name: str(tmp_path) if name == "stdlib" else ""
+        )
+        seen: list[list[str]] = []
+        monkeypatch.setattr(
+            "subprocess.run",
+            lambda cmd, **kw: seen.append(cmd)
+            or type("R", (), {"returncode": 0, "stderr": ""})(),
+        )
+        up_mod._pip_install(tmp_path / "pkg")
+        assert "--break-system-packages" in seen[0]
+
+    def test_skips_flag_without_externally_managed(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        import sysconfig
+
+        monkeypatch.setattr(
+            sysconfig, "get_path", lambda name: str(tmp_path) if name == "stdlib" else ""
+        )
+        seen: list[list[str]] = []
+        monkeypatch.setattr(
+            "subprocess.run",
+            lambda cmd, **kw: seen.append(cmd)
+            or type("R", (), {"returncode": 0, "stderr": ""})(),
+        )
+        up_mod._pip_install(tmp_path / "pkg")
+        assert "--break-system-packages" not in seen[0]