Unattended messages expire in the detached session's loop, not as a 9P request is served

serveFs expired them, but a read is answered while a step is out in a
syscall, because reads change nothing, and this one changed pane messages
and needs_frame from under the step. The detached session's loop now expires
them between steps, and while nobody is attached and a message is up it
looks again every 100 ms rather than waiting for something to wake it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 6 insertions, 1 deletions

diff --git a/src/Messages.zig b/src/Messages.zig
index 0652f974..00352afe 100644
--- a/src/Messages.zig
+++ b/src/Messages.zig
@@ -208,7 +208,9 @@ fn nowMs() i64 {
 /// With no frontend attached no input dismisses a message, and a detached
 /// session's /screen and messages kept what was said an hour ago: each
 /// pane's lines go once its newest has been up `message_linger_ms`, on the
-/// clock, checked as the core is stepped or served.
+/// clock, checked as the core is stepped and by the detached session's loop
+/// between steps -- not as a 9P request is served, since a read is answered
+/// while a step is out and must change nothing.
 /// ponytail: a pane's older lines go with its newest, not each on its own
 /// clock; the render pipeline's clock will give every line its own.
 pub fn expireUnattended(p: *Pardes) void {
@@ -570,7 +572,10 @@ test "with no frontend attached a message goes once it has lingered, on the cloc
     // Detached with nobody attached: past its linger it is gone, and the
     // line above it with it.
     p.unattended = true;
+    // A read served meanwhile changes nothing; the session's loop expires.
     _ = p.serveFs(.{ .tag = 1, .op = .read, .node = @intFromEnum(ctlfs.TopFile.index), .size = 64 });
+    try std.testing.expect(pane.msg_len > 0);
+    expireUnattended(p);
     try std.testing.expectEqual(@as(u16, 0), pane.msg_len);
     try std.testing.expectEqual(@as(u8, 0), pane.msg_older_len);
     // A fresh one stays until its linger is up.