feat(agent): add interrupt-aware tool dispatcher

backend/src/v1/agent/tool_dispatcher.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import BaseModel
+
+
+class InterruptResult(BaseModel):
+    interrupt_type: str
+    tool_name: str
+    tool_args: dict[str, Any]
+
+
+class BackendExecutionResult(BaseModel):
+    tool_name: str
+    tool_args: dict[str, Any]
+    result: Any | None = None
+
+
+class ToolDispatcher:
+    def dispatch(
+        self, tool: dict[str, Any]
+    ) -> InterruptResult | BackendExecutionResult:
+        return dispatch_tool_call(tool)
+
+
+def dispatch_tool_call(
+    tool: dict[str, Any],
+) -> InterruptResult | BackendExecutionResult:
+    name = tool["name"]
+    target = tool["execution_target"]
+    args = tool.get("args", {})
+
+    if target == "frontend":
+        return InterruptResult(
+            interrupt_type="tool_execution",
+            tool_name=name,
+            tool_args=args,
+        )
+
+    if target == "backend":
+        requires_approval = tool.get("requires_approval", False)
+        if requires_approval:
+            return InterruptResult(
+                interrupt_type="approval_required",
+                tool_name=name,
+                tool_args=args,
+            )
+        return BackendExecutionResult(
+            tool_name=name,
+            tool_args=args,
+        )
+
+    raise ValueError(f"Unknown execution_target: {target}")

backend/tests/unit/v1/agent/test_tool_dispatcher.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+from v1.agent.tool_dispatcher import (
+    BackendExecutionResult,
+    InterruptResult,
+    ToolDispatcher,
+    dispatch_tool_call,
+)
+
+
+class TestToolDispatcher:
+    def test_frontend_tool_returns_interrupt(self):
+        tool = {
+            "name": "ui.navigate_to",
+            "execution_target": "frontend",
+            "args": {"path": "/home"},
+        }
+        result = dispatch_tool_call(tool)
+        assert isinstance(result, InterruptResult)
+        assert result.interrupt_type == "tool_execution"
+        assert result.tool_name == "ui.navigate_to"
+
+    def test_backend_tool_executes_directly(self):
+        tool = {
+            "name": "srv.get_user_info",
+            "execution_target": "backend",
+            "args": {"user_id": "u1"},
+            "requires_approval": False,
+        }
+        result = dispatch_tool_call(tool)
+        assert isinstance(result, BackendExecutionResult)
+        assert result.tool_name == "srv.get_user_info"
+
+    def test_backend_tool_with_approval_returns_interrupt(self):
+        tool = {
+            "name": "srv.transfer_funds",
+            "execution_target": "backend",
+            "args": {"to": "u2", "amount": 100},
+            "requires_approval": True,
+        }
+        result = dispatch_tool_call(tool)
+        assert isinstance(result, InterruptResult)
+        assert result.interrupt_type == "approval_required"
+        assert result.tool_name == "srv.transfer_funds"
+
+    def test_dispatcher_class_can_dispatch(self):
+        dispatcher = ToolDispatcher()
+        tool = {
+            "name": "ui.show_dialog",
+            "execution_target": "frontend",
+            "args": {"message": "Hello"},
+        }
+        result = dispatcher.dispatch(tool)
+        assert isinstance(result, InterruptResult)