From ffef5a511a14071bd9be9887439a6cb40af3fb92 Mon Sep 17 00:00:00 2001
From: Gabriel Schneider <gbrls@0x4200.cafe>
Date: Mon, 28 Sep 2026 16:04:34 -0300
Subject: A detached session stopped by SIGTERM, SIGINT or SIGHUP unlinks its
 sockets

The signals' default action ended the process where it stood, leaving
pardes-9p-*.sock and pardes-detached-*.sock for the next session to trip on.
The detached session now takes them to mean quit: the handler sets a flag and
wakes the loop, which leaves as Exit does, through the teardown that unlinks
both. fs.py sends each of the three and checks the sockets are gone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/detached/server.zig | 17 ++++++++++++++++-
 test/fs.py              | 18 ++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/detached/server.zig b/src/detached/server.zig
index 5bf2384b..b47bda1b 100644
--- a/src/detached/server.zig
+++ b/src/detached/server.zig
@@ -1181,6 +1181,17 @@ pub const Session = struct {
     }
 };
 
+/// SIGTERM, SIGINT or SIGHUP: quit as Exit does, through the loop, so its
+/// sockets are unlinked on the way out rather than left for the next
+/// session to trip on. The handler only sets the flag and wakes the loop.
+var quit_signalled = std.atomic.Value(bool).init(false);
+var quit_wake: c_int = -1;
+
+fn onQuitSignal(_: std.posix.SIG) callconv(.c) void {
+    quit_signalled.store(true, .release);
+    if (quit_wake >= 0) _ = libc.send(quit_wake, "q", 1, nosignal);
+}
+
 pub fn run(init: std.process.Init, opts: pardes.Options, name: []const u8) !void {
     const gpa = init.gpa;
     const allocs = pardes.memory.init(gpa);
@@ -1231,7 +1242,11 @@ pub fn run(init: std.process.Init, opts: pardes.Options, name: []const u8) !void
     core.host = h;
     while (core.nextEffect()) |effect| core.perform(effect);
     session.in_loop = true;
-    while (!session.core.quit) {
+    quit_wake = session.mailbox.wake[1];
+    const on_quit: std.posix.Sigaction = .{ .handler = .{ .handler = onQuitSignal }, .mask = std.posix.sigemptyset(), .flags = 0 };
+    for ([_]std.posix.SIG{ .HUP, .INT, .TERM }) |sig| std.posix.sigaction(sig, &on_quit, null);
+    defer quit_wake = -1;
+    while (!session.core.quit and !quit_signalled.load(.acquire)) {
         pardes.turn.restoreSettled();
         try session.core.pump(h);
         if (session.core.quit) break;
diff --git a/test/fs.py b/test/fs.py
index b55ad5ab..45c38c2e 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -3,6 +3,7 @@ import contextlib
 import fcntl
 import json
 import os
+import signal
 from pathlib import Path
 import subprocess
 import struct
@@ -424,10 +425,27 @@ def exit_answers(binary):
                 raise AssertionError("Exit did not quit the editor")
 
 
+def signal_cleans_up(binary):
+    """A detached session told to stop by a signal unlinks its sockets."""
+    for sig in [signal.SIGTERM, signal.SIGINT, signal.SIGHUP]:
+        with tempfile.TemporaryDirectory(prefix='pardes-sig-') as directory:
+            root = Path(directory)
+            seen = {}
+            with session(binary, root, 'sig', terminal=seen) as (client, address):
+                detached = root / 'pardes-detached-sig.sock'
+                assert address.exists() and detached.exists()
+                os.kill(seen['pid'], sig)
+                deadline = time.monotonic() + 5
+                while (address.exists() or detached.exists()) and time.monotonic() < deadline:
+                    time.sleep(.01)
+                assert not address.exists() and not detached.exists(), (sig, list(root.iterdir()))
+
+
 def test(binary, quic=False):
     started = time.monotonic()
     run_file(binary)
     exit_answers(binary)
+    signal_cleans_up(binary)
     for options, message in [
         (['--fs'], b'no such option'),
         (['--fs9'], b'no such option'),
-- 
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