diff --git a/.github/workflows/windows-probe.yml b/.github/workflows/windows-probe.yml
new file mode 100644
index 000000000..3e0ab7825
--- /dev/null
+++ b/.github/workflows/windows-probe.yml
@@ -0,0 +1,63 @@
+# Probe only, for the fork: never part of an upstream PR.
+name: Windows probe
+
+on:
+  push:
+    branches:
+      - 'probe/**'
+  workflow_dispatch:
+
+jobs:
+  probe:
+    name: session loop ${{ matrix.mode }} py${{ matrix.python-version }}
+    runs-on: windows-latest
+    timeout-minutes: 25
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.11", "3.12", "3.13", "3.14", "3.15"]
+        mode: [xdist]
+        include:
+          - python-version: "3.14"
+            mode: serial
+          - python-version: "3.15"
+            mode: serial
+    steps:
+      - name: Checkout Source Files
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Setup Environment
+        uses: ./.github/actions/setup
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Show TCP port settings
+        shell: bash
+        run: |
+          netsh int ipv4 show dynamicport tcp
+          nproc || true
+
+      - name: Run tests and sample TIME_WAIT
+        shell: bash
+        run: |
+          set +e
+          (while true; do
+             echo "$(date +%T) TIME_WAIT=$(netstat -an -p tcp | grep -c TIME_WAIT)"
+             sleep 5
+           done) > timewait.log 2>&1 &
+          sampler=$!
+          start=$(date +%s)
+          if [ "${{ matrix.mode }}" = serial ]; then
+            uv run pytest -n0 -p no:sugar -q --cov kasa \
+              --timeout 90 --timeout-method thread
+          else
+            uv run pytest -n auto -p no:sugar -q --cov kasa \
+              --timeout 90 --timeout-method thread
+          fi
+          rc=$?
+          echo "pytest exit=$rc after $(( $(date +%s) - start ))s"
+          kill $sampler
+          echo "--- TIME_WAIT samples (every 5 s)"
+          cat timewait.log
+          echo "--- peak TIME_WAIT: $(sed 's/.*TIME_WAIT=//' timewait.log | sort -n | tail -1)"
+          exit $rc
diff --git a/pyproject.toml b/pyproject.toml
index 65ca5e12b..f048c8a1a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -114,7 +114,10 @@ markers = [
     "requires_dummy: test requires dummy data to pass, skipped on real devices",
 ]
 asyncio_mode = "auto"
-asyncio_default_fixture_loop_scope = "function"
+# One event loop for the run, not one per test: on Windows each loop opens a
+# loopback TCP connection, and thousands of them use up the dynamic ports.
+asyncio_default_fixture_loop_scope = "session"
+asyncio_default_test_loop_scope = "session"
 #timeout = 10
 # dist=loadgroup enables grouping of tests into single worker.
 # required as caplog doesn't play nicely with multiple workers.
diff --git a/tests/conftest.py b/tests/conftest.py
index 9fac81c20..7a51b49e9 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -3,8 +3,6 @@
 import asyncio
 import functools
 import os
-import socket
-import struct
 import sys
 import warnings
 from pathlib import Path
@@ -166,35 +164,6 @@ def pytest_collection_modifyitems(
                 item.add_marker(pytest.mark.enable_socket)
 
 
-@pytest.fixture(autouse=True, scope="session")
-def _socketpair_without_time_wait():
-    """Stop event loop self-pipes from using up loopback ports on Windows.
-
-    Windows has no native socketpair, so the self-pipe of every event loop is a
-    loopback TCP connection, and closing it leaves a port in TIME_WAIT for about
-    two minutes. Tests get a new event loop each, so a fast run uses up the
-    dynamic port range, and the next loop then fails to start or hangs.
-    Closing the pair with SO_LINGER set to zero releases the port immediately.
-    """
-    if sys.platform != "win32":
-        yield
-        return
-
-    orig_socketpair = socket.socketpair
-
-    def _socketpair(*args, **kwargs):
-        pair = orig_socketpair(*args, **kwargs)
-        for sock in pair:
-            # struct linger on Windows is two unsigned shorts: l_onoff, l_linger
-            sock.setsockopt(
-                socket.SOL_SOCKET, socket.SO_LINGER, struct.pack("HH", 1, 0)
-            )
-        return pair
-
-    with patch("socket.socketpair", _socketpair):
-        yield
-
-
 @pytest.fixture(autouse=True, scope="session")
 def asyncio_sleep_fixture(request: pytest.FixtureRequest):  # noqa: PT004
     """Patch sleep to prevent tests actually waiting."""