fix(node): run on the default Windows event loop (Proactor)

Verified end to end: a live browser peer on Windows connecting to a Windows
node — handshake, index sync, file download and an ffmpeg-transcoded video
stream all work on the ProactorEventLoop. aiortc only hangs on it in the
same-process loopback the tests use, which the repo-root conftest already
handles for the suite.

So the daemon no longer forces the SelectorEventLoop: that fixed
aiortc-in-one-process but broke ffmpeg (no subprocess support on a Windows
SelectorEventLoop). `use_compatible_event_loop()` becomes
`configure_event_loop()` — a no-op unless MESHBAY_NODE_EVENT_LOOP=selector
is set explicitly, as an escape hatch that probably never needs pulling.

This drops the planned "move ffmpeg off the asyncio loop" work.

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

2 files changed, 14 insertions, 16 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/daemon.py b/packages/meshbay-node/src/meshbay_node/daemon.py
index 6bc3bef..5aa6654 100644
--- a/packages/meshbay-node/src/meshbay_node/daemon.py
+++ b/packages/meshbay-node/src/meshbay_node/daemon.py
@@ -1634,9 +1634,9 @@ def _systemctl_user(verb: str, unit: str, *, not_running_hint: str,
 def main() -> None:
     import argparse
 
-    from meshbay_node.platform import force_utf8_stdio, use_compatible_event_loop
+    from meshbay_node.platform import configure_event_loop, force_utf8_stdio
     force_utf8_stdio()
-    use_compatible_event_loop()
+    configure_event_loop()
 
     parser = argparse.ArgumentParser(description="MeshBay Node daemon")
     parser.add_argument("command", nargs="?",
diff --git a/packages/meshbay-node/src/meshbay_node/platform.py b/packages/meshbay-node/src/meshbay_node/platform.py
index 2eab9e1..351289f 100644
--- a/packages/meshbay-node/src/meshbay_node/platform.py
+++ b/packages/meshbay-node/src/meshbay_node/platform.py
@@ -27,25 +27,23 @@ def force_utf8_stdio() -> None:
 # ── Event loop ───────────────────────────────────────────────────────────────
 
 
-def use_compatible_event_loop() -> None:
+def configure_event_loop() -> None:
     """
-    On Windows, select the SelectorEventLoop: aiortc's ICE stack does not
-    complete a loopback DataChannel handshake on the default ProactorEventLoop.
+    The daemon runs on Windows' default ProactorEventLoop: verified end to end
+    (a live browser peer connecting, an index sync, a file download and an
+    ffmpeg-transcoded video stream). aiortc only ever hangs on it in the
+    *same-process loopback* the tests use, which the test suite handles on its
+    own (repo-root conftest).
 
-    Cost: SelectorEventLoop cannot spawn subprocesses on Windows, so ffmpeg
-    streaming (asyncio.create_subprocess_exec in webrtc_server.py) does not work
-    under it. The video path needs a thread-based runner on Windows — tracked
-    for the port. No effect off Windows.
-
-    Whether the hang is real for a live peer (vs. the same-process loopback in
-    the tests) is still being established: set MESHBAY_NODE_EVENT_LOOP=proactor
-    to keep the default loop and check.
+    Escape hatch, opt-in only: MESHBAY_NODE_EVENT_LOOP=selector switches to the
+    SelectorEventLoop. That fixes aiortc-in-one-process but breaks ffmpeg
+    (SelectorEventLoop cannot spawn subprocesses on Windows), so it is not the
+    default and probably never should be.
     """
     if sys.platform != "win32":
         return
-    if os.environ.get("MESHBAY_NODE_EVENT_LOOP", "").lower() == "proactor":
-        return
-    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
+    if os.environ.get("MESHBAY_NODE_EVENT_LOOP", "").lower() == "selector":
+        asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
 
 
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