diff --git a/headroom/install/runtime.py b/headroom/install/runtime.py
index 43bf89243..0736e0a33 100644
--- a/headroom/install/runtime.py
+++ b/headroom/install/runtime.py
@@ -280,7 +280,10 @@ def start_detached_agent(profile: str) -> subprocess.Popen[str]:
 
     kwargs: dict[str, Any] = {"stdout": log_file, "stderr": log_file}
     if _is_windows():
-        kwargs["creationflags"] = getattr(subprocess, "DETACHED_PROCESS", 0) | getattr(
+        # DETACHED_PROCESS makes CREATE_NO_WINDOW a no-op (per Win32 docs), so a
+        # detached console child pops up a visible window. Use CREATE_NO_WINDOW
+        # instead; it still detaches from the parent's console.
+        kwargs["creationflags"] = getattr(subprocess, "CREATE_NO_WINDOW", 0x08000000) | getattr(
             subprocess, "CREATE_NEW_PROCESS_GROUP", 0
         )
     else:
@@ -413,7 +416,9 @@ def _spawn_detached_restart(profile: str) -> None:
     """
     command = [*resolve_headroom_command(), "install", "restart", "--profile", profile]
     popen_kwargs: dict[str, Any] = {"stdout": subprocess.DEVNULL, "stderr": subprocess.DEVNULL}
-    if not _is_windows():
+    if _is_windows():
+        popen_kwargs["creationflags"] = getattr(subprocess, "CREATE_NO_WINDOW", 0x08000000)
+    else:
         popen_kwargs["start_new_session"] = True
     subprocess.Popen(command, **popen_kwargs)
 
diff --git a/tests/test_install/test_runtime.py b/tests/test_install/test_runtime.py
index efdc8c494..ce654d859 100644
--- a/tests/test_install/test_runtime.py
+++ b/tests/test_install/test_runtime.py
@@ -417,15 +417,22 @@ def test_run_foreground_and_detached_helpers(monkeypatch, tmp_path: Path) -> Non
 
     monkeypatch.setattr("headroom.install.runtime.resolve_headroom_command", lambda: ["headroom"])
     monkeypatch.setattr("headroom.install.runtime.sys.platform", "win32")
-    monkeypatch.setattr("headroom.install.runtime.subprocess.DETACHED_PROCESS", 1, raising=False)
+    monkeypatch.setattr("headroom.install.runtime.subprocess.CREATE_NO_WINDOW", 4, raising=False)
     monkeypatch.setattr(
         "headroom.install.runtime.subprocess.CREATE_NEW_PROCESS_GROUP", 2, raising=False
     )
+    nt_calls: list[tuple[list[str], dict]] = []
     fake_proc_nt = FakeProc()
-    monkeypatch.setattr(
-        "headroom.install.runtime.subprocess.Popen", lambda command, **kwargs: fake_proc_nt
-    )
+
+    def fake_popen_nt(command: list[str], **kwargs):
+        nt_calls.append((command, kwargs))
+        return fake_proc_nt
+
+    monkeypatch.setattr("headroom.install.runtime.subprocess.Popen", fake_popen_nt)
     assert start_detached_agent("demo") is fake_proc_nt
+    # DETACHED_PROCESS is not used: it makes CREATE_NO_WINDOW a no-op on
+    # Windows, so a detached console child would pop up a visible window.
+    assert nt_calls[0][1]["creationflags"] == 4 | 2
 
     monkeypatch.setattr("headroom.install.runtime.sys.platform", "linux")
     fake_proc_posix = FakeProc()