fix Linux daemon PID lookup without lsof

hindsight-embed/hindsight_embed/daemon_embed_manager.py

@@ -43,6 +43,43 @@ def _parse_float_env(name: str, default: float) -> float:
         return default
 
 
+def _find_linux_pid_via_proc(port: int, proc_root: Path = Path("/proc")) -> int | None:
+    """Resolve a listening TCP socket to its owner without external tools."""
+    socket_inodes: set[str] = set()
+    for table in ("tcp", "tcp6"):
+        try:
+            lines = (proc_root / "net" / table).read_text().splitlines()[1:]
+        except OSError:
+            continue
+
+        for line in lines:
+            fields = line.split()
+            if len(fields) > 9 and fields[3] == "0A":
+                try:
+                    local_port = int(fields[1].rsplit(":", 1)[1], 16)
+                except (IndexError, ValueError):
+                    continue
+                if local_port == port:
+                    socket_inodes.add(fields[9])
+
+    if not socket_inodes:
+        return None
+
+    for process_dir in proc_root.iterdir():
+        if not process_dir.name.isdigit():
+            continue
+        try:
+            descriptors = (process_dir / "fd").iterdir()
+            for descriptor in descriptors:
+                target = descriptor.readlink()
+                match = re.fullmatch(r"socket:\[(\d+)]", str(target))
+                if match and match.group(1) in socket_inodes:
+                    return int(process_dir.name)
+        except OSError:
+            continue
+    return None
+
+
 def _safe_non_negative_float(value: float, fallback: float) -> float:
     """Return a finite non-negative float, or fallback for invalid values."""
     return value if math.isfinite(value) and value >= 0 else fallback
@@ -452,6 +489,13 @@ def _posix_listening_pids(port: int) -> list[int]:
                 if "users:" not in line:
                     continue
                 pids.extend(int(match) for match in re.findall(r"pid=(\d+)", line))
+        if pids:
+            return pids
+
+        if platform.system() == "Linux":
+            pid = _find_linux_pid_via_proc(port)
+            if pid is not None:
+                return [pid]
         return pids
 
     @staticmethod

hindsight-embed/tests/test_embed_manager.py

@@ -3,7 +3,7 @@
 from unittest.mock import MagicMock, patch
 
 from hindsight_embed import get_embed_manager
-from hindsight_embed.daemon_embed_manager import DaemonEmbedManager
+from hindsight_embed.daemon_embed_manager import DaemonEmbedManager, _find_linux_pid_via_proc
 
 
 def _mock_sentence_transformers_present(monkeypatch):
@@ -384,6 +384,36 @@ def fake_run(*args, **kwargs):
     assert calls[0][1]["creationflags"] == 0x08000000
 
 
+def test_find_linux_pid_via_proc_matches_listening_socket_inode(tmp_path):
+    proc_root = tmp_path / "proc"
+    (proc_root / "net").mkdir(parents=True)
+    (proc_root / "net" / "tcp").write_text(
+        "header\n"
+        "  0: 0100007F:23D9 00000000:0000 0A 00000000:00000000 00:00000000 "
+        "00000000 1000 0 424242 1 0000000000000000 100 0 0 10 0\n"
+    )
+    (proc_root / "net" / "tcp6").write_text("header\n")
+    fd_dir = proc_root / "15774" / "fd"
+    fd_dir.mkdir(parents=True)
+    (fd_dir / "19").symlink_to("socket:[424242]")
+
+    assert _find_linux_pid_via_proc(9177, proc_root) == 15774
+    assert _find_linux_pid_via_proc(9178, proc_root) is None
+
+
+def test_listening_pids_linux_falls_back_to_proc(monkeypatch):
+    monkeypatch.setattr("hindsight_embed.daemon_embed_manager.platform.system", lambda: "Linux")
+    monkeypatch.setattr(
+        "hindsight_embed.daemon_embed_manager.subprocess.run",
+        MagicMock(side_effect=FileNotFoundError),
+    )
+    proc_lookup = MagicMock(return_value=15774)
+    monkeypatch.setattr("hindsight_embed.daemon_embed_manager._find_linux_pid_via_proc", proc_lookup)
+
+    assert DaemonEmbedManager._listening_pids(9177) == [15774]
+    proc_lookup.assert_called_once_with(9177)
+
+
 def test_stop_ui_kills_recorded_and_configured_ports(tmp_path, monkeypatch):
     """After a UI-port change, stop_ui must kill BOTH the recorded (old, actually
     running) port and the configured (new) port — otherwise the old UI orphans."""