mcp(fix[window_tools,session_tools]): Validate direction parameters

why: split_window silently ignored invalid directions (fell to default),
create_window raised KeyError surfaced as "Unexpected error".
what:
- split_window: check _DIRECTION_MAP.get() result, raise ToolError if None
- create_window: use .get() with explicit ToolError on invalid direction
- Add tests for invalid direction in both tools

Author: tony

src/libtmux/mcp/tools/session_tools.py

@@ -93,7 +93,14 @@ def create_window(
             "before": WindowDirection.Before,
             "after": WindowDirection.After,
         }
-        kwargs["direction"] = direction_map[direction.lower()]
+        resolved = direction_map.get(direction.lower())
+        if resolved is None:
+            from fastmcp.exceptions import ToolError
+
+            valid = ", ".join(sorted(direction_map))
+            msg = f"Invalid direction: {direction!r}. Valid: {valid}"
+            raise ToolError(msg)
+        kwargs["direction"] = resolved
     window = session.new_window(**kwargs)
     return json.dumps(_serialize_window(window))
 

src/libtmux/mcp/tools/window_tools.py

@@ -121,6 +121,12 @@ def split_window(
     pane_dir: PaneDirection | None = None
     if direction is not None:
         pane_dir = _DIRECTION_MAP.get(direction.lower())
+        if pane_dir is None:
+            from fastmcp.exceptions import ToolError
+
+            valid = ", ".join(sorted(_DIRECTION_MAP))
+            msg = f"Invalid direction: {direction!r}. Valid: {valid}"
+            raise ToolError(msg)
 
     new_pane = window.split(
         direction=pane_dir,

tests/mcp/test_session_tools.py

@@ -5,6 +5,9 @@
 import json
 import typing as t
 
+import pytest
+from fastmcp.exceptions import ToolError
+
 from libtmux.mcp.tools.session_tools import (
     create_window,
     kill_session,
@@ -50,6 +53,19 @@ def test_create_window(mcp_server: Server, mcp_session: Session) -> None:
     assert data["window_name"] == "mcp_test_win"
 
 
+def test_create_window_invalid_direction(
+    mcp_server: Server, mcp_session: Session
+) -> None:
+    """create_window raises ToolError on invalid direction."""
+    with pytest.raises(ToolError, match="Invalid direction"):
+        create_window(
+            session_name=mcp_session.session_name,
+            window_name="bad_dir",
+            direction="sideways",
+            socket_name=mcp_server.socket_name,
+        )
+
+
 def test_rename_session(mcp_server: Server, mcp_session: Session) -> None:
     """rename_session renames an existing session."""
     original_name = mcp_session.session_name

tests/mcp/test_window_tools.py

@@ -5,6 +5,9 @@
 import json
 import typing as t
 
+import pytest
+from fastmcp.exceptions import ToolError
+
 from libtmux.mcp.tools.window_tools import (
     kill_window,
     list_panes,
@@ -57,6 +60,19 @@ def test_split_window_with_direction(mcp_server: Server, mcp_session: Session) -
     assert "pane_id" in data
 
 
+def test_split_window_invalid_direction(
+    mcp_server: Server, mcp_session: Session
+) -> None:
+    """split_window raises ToolError on invalid direction."""
+    window = mcp_session.active_window
+    with pytest.raises(ToolError, match="Invalid direction"):
+        split_window(
+            window_id=window.window_id,
+            direction="diagonal",
+            socket_name=mcp_server.socket_name,
+        )
+
+
 def test_rename_window(mcp_server: Server, mcp_session: Session) -> None:
     """rename_window renames a window."""
     window = mcp_session.active_window