fix(dispatch): forward session_id into registry.dispatch (#28479)

Both the regular and execute_code dispatch paths forward task_id into
registry.dispatch via middleware _dispatch lambdas but silently dropped
session_id. Dispatch-layer hooks (e.g. set_enforcement_fn) that correlate
calls with the active session received "" for every invocation.

Pass session_id=session_id at both _dispatch call sites inside
handle_function_call, matching the existing task_id pattern. Hooks
already received session_id; this closes the registry.dispatch gap.

Rebased onto current main where dispatch is wrapped by
run_tool_execution_middleware — the old direct-dispatch sites from
#28479 no longer exist.

test(dispatch): add tests for session_id forwarding (NousResearch#28479)

Covers standard and execute_code paths through the middleware wrapper.
Verifies task_id forwarding is not broken by the change.

model_tools.py

@@ -1115,6 +1115,7 @@ def handle_function_call(
                     return registry.dispatch(
                         function_name, next_args,
                         task_id=task_id,
+                        session_id=session_id,
                         enabled_tools=sandbox_enabled,
                     )
             else:
@@ -1122,6 +1123,7 @@ def handle_function_call(
                     return registry.dispatch(
                         function_name, next_args,
                         task_id=task_id,
+                        session_id=session_id,
                         user_task=user_task,
                     )
             from hermes_cli.middleware import run_tool_execution_middleware

tests/test_dispatch_session_id.py

@@ -0,0 +1,75 @@
+"""Tests that handle_function_call forwards session_id into registry.dispatch."""
+
+import json
+from unittest.mock import MagicMock, patch
+
+
+def _make_registry(captured: dict):
+    """Return a mock registry whose dispatch records the kwargs it receives."""
+    registry = MagicMock()
+
+    def _dispatch(name, args, **kwargs):
+        captured.update(kwargs)
+        return json.dumps({"result": "ok"})
+
+    registry.dispatch.side_effect = _dispatch
+    return registry
+
+
+class TestSessionIdForwarding:
+
+    def test_standard_path_forwards_session_id(self):
+        """registry.dispatch receives session_id on the normal tool path."""
+        captured = {}
+        with patch("model_tools.registry", _make_registry(captured)):
+            from model_tools import handle_function_call
+            handle_function_call(
+                "web_search",
+                {"query": "test"},
+                task_id="t1",
+                session_id="sess-abc",
+                skip_pre_tool_call_hook=True,
+            )
+        assert captured.get("session_id") == "sess-abc"
+
+    def test_execute_code_path_forwards_session_id(self):
+        """registry.dispatch receives session_id on the execute_code path."""
+        captured = {}
+        with patch("model_tools.registry", _make_registry(captured)):
+            from model_tools import handle_function_call
+            handle_function_call(
+                "execute_code",
+                {"code": "print(1)"},
+                task_id="t1",
+                session_id="sess-xyz",
+                skip_pre_tool_call_hook=True,
+            )
+        assert captured.get("session_id") == "sess-xyz"
+
+    def test_session_id_default_is_none(self):
+        """When session_id is omitted, dispatch receives None."""
+        captured = {}
+        with patch("model_tools.registry", _make_registry(captured)):
+            from model_tools import handle_function_call
+            handle_function_call(
+                "web_search",
+                {"query": "test"},
+                task_id="t1",
+                skip_pre_tool_call_hook=True,
+            )
+        assert "session_id" in captured
+        assert captured["session_id"] is None
+
+    def test_task_id_still_forwarded(self):
+        """Existing task_id forwarding is not broken by this change."""
+        captured = {}
+        with patch("model_tools.registry", _make_registry(captured)):
+            from model_tools import handle_function_call
+            handle_function_call(
+                "web_search",
+                {"query": "test"},
+                task_id="task-999",
+                session_id="sess-1",
+                skip_pre_tool_call_hook=True,
+            )
+        assert captured.get("task_id") == "task-999"