feat(rnsh): update rnsh command resolution to prefer module launcher and add error handling for non-executable paths

meshchatx/src/backend/rnsh_manager.py

@@ -9,6 +9,7 @@ while the app is active, and persists session definitions plus output history.
 from __future__ import annotations
 
 import contextlib
+import importlib.util
 import json
 import os
 import re
@@ -41,6 +42,8 @@ DEFAULT_TERMINAL_COLS = 120
 # "rnsh listening for commands on <a1b2c3...>" or "Listening on : <...>".
 _LISTEN_ADDRESS_RE = re.compile(r"<([0-9a-fA-F]{16,})>")
 
+_RNSH_MODULE = "RNS.Utilities.rnsh.rnsh"
+
 
 class RNSHSession:
     """Runtime state for a single rnsh session."""
@@ -229,12 +232,35 @@ class RNSHSession:
         if match:
             self.listen_address = match.group(1).lower()
 
-    def _build_command(self):
+    @staticmethod
+    def _rnsh_module_available():
+        try:
+            return importlib.util.find_spec(_RNSH_MODULE) is not None
+        except (ImportError, ModuleNotFoundError, ValueError, AttributeError):
+            return False
+
+    @staticmethod
+    def _resolve_rnsh_launcher():
+        """Return argv prefix for launching rnsh.
+
+        Prefer the Python module entry point so sessions work when the PATH
+        console-script wrapper is not executable (common with pip --user
+        installs) or when Landlock denies executing paths outside allowed
+        read roots (for example ``~/.local/bin/rnsh``).
+        """
+        if RNSHSession._rnsh_module_available():
+            return [sys.executable, "-m", _RNSH_MODULE]
         executable = shutil.which("rnsh")
+        if executable and os.access(executable, os.X_OK):
+            return [executable]
         if executable:
-            command = [executable]
-        else:
-            command = [sys.executable, "-m", "RNS.Utilities.rnsh.rnsh"]
+            raise PermissionError(f"Permission denied: '{executable}'")
+        raise FileNotFoundError(
+            "rnsh is not available; install the rns package or ensure rnsh is on PATH",
+        )
+
+    def _build_command(self):
+        command = list(self._resolve_rnsh_launcher())
 
         # Attach rnsh to the same Reticulum config directory (and therefore the
         # same shared instance and rpc_key) as the MeshChatX app. Without this

tests/backend/test_rnsh_api.py

@@ -189,6 +189,64 @@ def test_rnsh_resize_updates_geometry_without_process():
     assert result["cols"] == 100
 
 
+def test_rnsh_prefers_module_launcher_when_rns_installed(monkeypatch):
+    from meshchatx.src.backend import rnsh_manager as rnsh_mod
+
+    monkeypatch.setattr(rnsh_mod.RNSHSession, "_rnsh_module_available", lambda: True)
+    monkeypatch.setattr(
+        rnsh_mod.shutil, "which", lambda _name: "/home/user/.local/bin/rnsh"
+    )
+
+    manager = MagicMock()
+    session = rnsh_mod.RNSHSession(
+        manager,
+        "s1",
+        {"mode": "connect", "destination": "deadbeef"},
+    )
+    command = session._build_command()
+    assert command[:3] == [rnsh_mod.sys.executable, "-m", rnsh_mod._RNSH_MODULE]
+    assert command[-1] == "deadbeef"
+
+
+def test_rnsh_falls_back_to_path_binary_when_module_missing(monkeypatch):
+    from meshchatx.src.backend import rnsh_manager as rnsh_mod
+
+    monkeypatch.setattr(rnsh_mod.RNSHSession, "_rnsh_module_available", lambda: False)
+    monkeypatch.setattr(rnsh_mod.shutil, "which", lambda _name: "/usr/bin/rnsh")
+    monkeypatch.setattr(rnsh_mod.os, "access", lambda _path, _mode: True)
+
+    manager = MagicMock()
+    session = rnsh_mod.RNSHSession(
+        manager,
+        "s1",
+        {"mode": "connect", "destination": "deadbeef"},
+    )
+    command = session._build_command()
+    assert command[0] == "/usr/bin/rnsh"
+    assert command[-1] == "deadbeef"
+
+
+def test_rnsh_non_executable_path_wrapper_raises_permission_error(monkeypatch):
+    from meshchatx.src.backend import rnsh_manager as rnsh_mod
+
+    monkeypatch.setattr(rnsh_mod.RNSHSession, "_rnsh_module_available", lambda: False)
+    monkeypatch.setattr(
+        rnsh_mod.shutil,
+        "which",
+        lambda _name: "/home/user/.local/bin/rnsh",
+    )
+    monkeypatch.setattr(rnsh_mod.os, "access", lambda _path, _mode: False)
+
+    manager = MagicMock()
+    session = rnsh_mod.RNSHSession(
+        manager,
+        "s1",
+        {"mode": "connect", "destination": "deadbeef"},
+    )
+    with pytest.raises(PermissionError, match="Permission denied"):
+        session._build_command()
+
+
 @pytest.mark.asyncio
 async def test_rnsh_session_not_found_returns_404(mock_app):
     mock_app.rnsh_manager = _DummyManager()

tests/backend/test_telemetry_extended.py

@@ -39,4 +39,3 @@ def test_telemeter_unpack_location_robustness():
     assert Telemeter.unpack_location([b"lat", b"lon"]) is None
     # Test with invalid types
     assert Telemeter.unpack_location(["not_bytes"] * 7) is None
-