feat(models): Support OpenAI Responses API labs model

Add OpenAI and Azure OpenAI Responses API labs LLM implementations with request conversion, response parsing, streaming support, reasoning metadata, function calls, usage metadata. Fixes: #3209

Author: FrigaZzz

pyproject.toml

@@ -145,6 +145,7 @@ optional-dependencies.extensions = [
   "llama-index-embeddings-google-genai>=0.3",
   "llama-index-readers-file>=0.4",
   "lxml>=5.3",
+  "openai>=2.20.0,<3.0.0",
   "pypika>=0.50",
   "toolbox-adk>=1,<2",
 ]
@@ -207,7 +208,7 @@ optional-dependencies.test = [
   "litellm>=1.83.7,<=1.83.14",
   "llama-index-readers-file>=0.4",
   "mcp>=1.24,<2",
-  "openai>=1.100.2",
+  "openai>=2.20.0,<3.0.0",
   "opentelemetry-exporter-gcp-logging>=1.9.0a0,<=1.12.0a0",
   "opentelemetry-exporter-gcp-monitoring>=1.9.0a0,<2",
   "opentelemetry-exporter-gcp-trace>=1.9,<2",

src/google/adk/flows/llm_flows/contents.py

@@ -52,16 +52,24 @@ async def run_async(
       ):
         preserve_function_call_ids = True
       else:
-        # Anthropic pairs tool_use/tool_result by id, so `adk-*` fallback
-        # ids must survive replay.
+        # Some non-Gemini providers pair tool calls/results by id, so `adk-*`
+        # fallback ids must survive replay.
         try:
           from ...models.anthropic_llm import AnthropicLlm
         except (ImportError, OSError):
           AnthropicLlm = None
+        try:
+          from ...labs.openai_responses import OpenAIResponsesLlm
+        except (ImportError, OSError):
+          OpenAIResponsesLlm = None
         if AnthropicLlm is not None and isinstance(
             canonical_model, AnthropicLlm
         ):
           preserve_function_call_ids = True
+        if OpenAIResponsesLlm is not None and isinstance(
+            canonical_model, OpenAIResponsesLlm
+        ):
+          preserve_function_call_ids = True
 
     # Preserve all contents that were added by instruction processor
     # (since llm_request.contents will be completely reassigned below)

src/google/adk/labs/openai_responses/__init__.py

@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ._openai_responses_llm import AzureOpenAIResponsesLlm
+from ._openai_responses_llm import OpenAIResponsesLlm
+
+__all__ = [
+    'AzureOpenAIResponsesLlm',
+    'OpenAIResponsesLlm',
+]