Python: Preserve reusable declarative model options

python/packages/declarative/agent_framework_declarative/_loader.py

@@ -740,10 +740,11 @@ def _parse_chat_options(self, model: Model | None) -> dict[str, Any]:
             chat_options["stop"] = options.stopSequences
         if options.allowMultipleToolCalls is not None:
             chat_options["allow_multiple_tool_calls"] = options.allowMultipleToolCalls
-        if (chat_tool_mode := options.additionalProperties.pop("chatToolMode", None)) is not None:
+        additional_properties = options.additionalProperties.copy()
+        if (chat_tool_mode := additional_properties.pop("chatToolMode", None)) is not None:
             chat_options["tool_choice"] = chat_tool_mode
-        if options.additionalProperties:
-            chat_options["additional_chat_options"] = options.additionalProperties
+        if additional_properties:
+            chat_options["additional_chat_options"] = additional_properties
         return chat_options
 
     def _parse_tools(self, tools: list[Tool] | None) -> list[AFFunctionTool | dict[str, Any]] | None:

python/packages/declarative/tests/test_declarative_loader.py

@@ -3,6 +3,7 @@
 import builtins
 import sys
 import threading
+from copy import deepcopy
 from pathlib import Path
 from typing import Any
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -643,6 +644,38 @@ def test_create_agent_from_dict_chat_options_in_default_options(self):
         assert agent.default_options.get("temperature") == 0.7
         assert agent.default_options.get("top_p") == 0.9
 
+    @pytest.mark.parametrize("use_async", [False, True])
+    @pytest.mark.parametrize("tool_choice", ["auto", "required", "none", None])
+    async def test_create_agent_from_dict_preserves_reused_model_options(
+        self, tool_choice: str | None, use_async: bool
+    ) -> None:
+        """Reusing a definition preserves caller options and each agent's tool choice."""
+        from agent_framework_declarative import AgentFactory
+
+        additional_properties: dict[str, Any] = {"custom_option": {"nested": ["value"]}}
+        if tool_choice is not None:
+            additional_properties["chatToolMode"] = tool_choice
+        agent_def: dict[str, Any] = {
+            "kind": "Prompt",
+            "name": "ReusableAgent",
+            "model": {"options": {"additionalProperties": additional_properties}},
+        }
+        original = deepcopy(agent_def)
+        mock_client = MagicMock()
+        mock_client.model = "test-model"
+        factory = AgentFactory(client=mock_client)
+
+        for _ in range(2):
+            if use_async:
+                agent = await factory.create_agent_from_dict_async(agent_def)
+            else:
+                agent = factory.create_agent_from_dict(agent_def)
+
+            assert agent.default_options["tool_choice"] == (tool_choice or "auto")
+            assert agent.default_options["additional_chat_options"] == {"custom_option": {"nested": ["value"]}}
+
+        assert agent_def == original
+
 
 class TestAgentFactorySafeMode:
     """Tests for AgentFactory safe_mode parameter."""