feat: Support provider-prefixed Gemini model IDs

Merge #5555

## Summary

- Extract Gemini model names from LiteLLM-compatible provider-prefixed IDs such as `gemini/gemini-2.5-flash`, `vertex_ai/gemini-2.5-flash`, and `openrouter/google/gemini-2.5-pro:online`
- Keep malformed Vertex `projects/...` paths from being treated as valid Gemini IDs
- Add an OpenRouter-through-LiteLLM sample showing `OPENROUTER_API_KEY`, `api_base`, and `openrouter/...` model usage

## Why

ADK's Gemini tool checks already normalize native model IDs and Vertex/Apigee paths, but provider-prefixed LiteLLM model IDs were left as-is. That made Google Search reject routed Gemini IDs even when the underlying model name was Gemini. This updates the shared model-name utility so existing Gemini classification paths work for provider-prefixed IDs without special-casing one provider.

Refs #2709.

## Tests

- `uv run --extra test pytest tests/unittests/utils/test_model_name_utils.py tests/unittests/tools/test_google_search_tool.py`
- `uv run --extra dev pyink --check --diff --config pyproject.toml src/google/adk/utils/model_name_utils.py tests/unittests/utils/test_model_name_utils.py tests/unittests/tools/test_google_search_tool.py contributing/samples/hello_world_openrouter/agent.py contributing/samples/hello_world_openrouter/__init__.py`
- `uv run --extra test python -m py_compile contributing/samples/hello_world_openrouter/agent.py`

Co-authored-by: George Weale <gweale@google.com>
COPYBARA_INTEGRATE_REVIEW=#5555 from kenrogers:codex/provider-prefixed-gemini-models 60234b4
PiperOrigin-RevId: 936889403

Author: 2 people

src/google/adk/utils/model_name_utils.py

@@ -41,7 +41,8 @@ def extract_model_name(model_string: str) -> str:
 
   Args:
     model_string: Either a simple model name like "gemini-2.5-pro" or a
-      path-based model name like "projects/.../models/gemini-2.5-flash"
+      path-based model name like "projects/.../models/gemini-2.5-flash",
+      or a provider-prefixed model name like "gemini/gemini-2.5-flash".
 
   Returns:
     The extracted model name (e.g., "gemini-2.5-pro")
@@ -63,6 +64,19 @@ def extract_model_name(model_string: str) -> str:
   if model_string.startswith('models/'):
     return model_string[len('models/') :]
 
+  # Malformed 'projects/' path (didn't match the Vertex pattern above); return
+  # as-is so the provider-prefix block below doesn't misread it as a Gemini id.
+  if model_string.startswith('projects/'):
+    return model_string
+
+  # Handle provider-prefixed LiteLLM-compatible names like
+  # "gemini/gemini-2.5-flash" or "openrouter/google/gemini-2.5-pro:online".
+  # Only Gemini names are extracted; other providers fall through unchanged.
+  if '/' in model_string:
+    model_name = model_string.rsplit('/', 1)[1]
+    if model_name.startswith('gemini-'):
+      return model_name
+
   # If it's not a path-based model, return as-is (simple model name)
   return model_string
 

tests/unittests/tools/test_google_search_tool.py

@@ -250,6 +250,27 @@ async def test_process_llm_request_with_gemini_2_model_and_existing_tools_succee
     assert llm_request.config.tools[0] == existing_tool
     assert llm_request.config.tools[1].google_search is not None
 
+  @pytest.mark.asyncio
+  async def test_process_llm_request_with_provider_prefixed_gemini_model(
+      self,
+  ):
+    """Test processing LLM request with provider-prefixed Gemini model."""
+    tool = GoogleSearchTool()
+    tool_context = await _create_tool_context()
+
+    llm_request = LlmRequest(
+        model='openrouter/google/gemini-2.5-pro:online',
+        config=types.GenerateContentConfig(),
+    )
+
+    await tool.process_llm_request(
+        tool_context=tool_context, llm_request=llm_request
+    )
+
+    assert llm_request.config.tools is not None
+    assert len(llm_request.config.tools) == 1
+    assert llm_request.config.tools[0].google_search is not None
+
   @pytest.mark.asyncio
   async def test_process_llm_request_with_non_gemini_model_raises_error(self):
     """Test that non-Gemini model raises ValueError."""

tests/unittests/utils/test_model_name_utils.py

@@ -68,6 +68,20 @@ def test_extract_model_name_with_models_prefix(self):
     assert extract_model_name('models/gemini-2.5-pro') == 'gemini-2.5-pro'
     assert extract_model_name('models/gemini-2.5-flash') == 'gemini-2.5-flash'
 
+  def test_extract_model_name_provider_prefixed_model(self):
+    """Test extraction of provider-prefixed Gemini model names."""
+    assert extract_model_name('gemini/gemini-2.5-flash') == 'gemini-2.5-flash'
+    assert extract_model_name('vertex_ai/gemini-2.5-flash') == (
+        'gemini-2.5-flash'
+    )
+    assert (
+        extract_model_name('openrouter/google/gemini-2.5-pro:online')
+        == 'gemini-2.5-pro:online'
+    )
+    assert extract_model_name('openrouter/anthropic/claude-sonnet-4') == (
+        'openrouter/anthropic/claude-sonnet-4'
+    )
+
   def test_extract_model_name_invalid_path(self):
     """Test that invalid path formats return the original string."""
     invalid_paths = [
@@ -120,6 +134,13 @@ def test_is_gemini_model_path_based_names(self):
     non_gemini_path = 'projects/265104255505/locations/us-central1/publishers/google/models/claude-3-sonnet'
     assert is_gemini_model(non_gemini_path) is False
 
+  def test_is_gemini_model_provider_prefixed_names(self):
+    """Test Gemini model detection with provider-prefixed model names."""
+    assert is_gemini_model('gemini/gemini-2.5-flash') is True
+    assert is_gemini_model('vertex_ai/gemini-2.5-flash') is True
+    assert is_gemini_model('openrouter/google/gemini-2.5-pro:online') is True
+    assert is_gemini_model('openrouter/anthropic/claude-sonnet-4') is False
+
   def test_is_gemini_model_edge_cases(self):
     """Test edge cases for Gemini model detection."""
     # Test with None
@@ -172,6 +193,13 @@ def test_is_gemini_1_model_path_based_names(self):
     gemini_2_path = 'projects/265104255505/locations/us-central1/publishers/google/models/gemini-2.5-flash'
     assert is_gemini_1_model(gemini_2_path) is False
 
+  def test_is_gemini_1_model_provider_prefixed_names(self):
+    """Test Gemini 1.x detection with provider-prefixed model names."""
+    assert is_gemini_1_model('gemini/gemini-1.5-flash') is True
+    assert is_gemini_1_model('vertex_ai/gemini-1.5-flash') is True
+    assert is_gemini_1_model('openrouter/google/gemini-1.5-pro:online') is True
+    assert is_gemini_1_model('openrouter/google/gemini-2.5-pro') is False
+
   def test_is_gemini_1_model_edge_cases(self):
     """Test edge cases for Gemini 1.x model detection."""
     # Test with None
@@ -223,6 +251,19 @@ def test_is_gemini_eap_or_2_or_above_path_based_names(self):
     gemini_3_path = 'projects/12345/locations/us-east1/publishers/google/models/gemini-3.0-pro'
     assert is_gemini_eap_or_2_or_above(gemini_3_path) is True
 
+  def test_is_gemini_eap_or_2_or_above_provider_prefixed_names(self):
+    """Test Gemini 2.0+ detection with provider-prefixed model names."""
+    assert is_gemini_eap_or_2_or_above('gemini/gemini-2.5-flash') is True
+    assert is_gemini_eap_or_2_or_above('vertex_ai/gemini-2.5-flash') is True
+    assert (
+        is_gemini_eap_or_2_or_above('openrouter/google/gemini-2.5-pro:online')
+        is True
+    )
+    assert (
+        is_gemini_eap_or_2_or_above('openrouter/google/gemini-1.5-pro:online')
+        is False
+    )
+
   def test_is_gemini_eap_or_2_or_above_edge_cases(self):
     """Test edge cases for Gemini 2.0+ model detection."""
     # Test with None
@@ -253,6 +294,8 @@ def test_model_classification_consistency(self):
         'gemini-2.5-flash',
         'gemini-2.5-pro',
         'gemini-3.0-pro',
+        'gemini/gemini-2.5-flash',
+        'openrouter/google/gemini-2.5-pro:online',
         'projects/123/locations/us-central1/publishers/google/models/gemini-1.5-pro',
         'projects/123/locations/us-central1/publishers/google/models/gemini-2.5-flash',
         'projects/123/locations/us-central1/publishers/google/models/gemini-3.0-pro',