Add test confirming gemini-2.5-flash recursive schema support on GLA

This test verifies that Google has fixed the issue where gemini-2.5-flash
would return 500 errors when using recursive schemas with $refs on the
GLA (Generative Language API) endpoint.

The test successfully passes, confirming that:
- Recursive schemas with $defs and $refs now work on GLA
- gemini-2.5-flash properly handles TreeNode structures
- Google's enhanced JSON Schema support is fully functional

This validates that we can use the same JSON schema transformer for both
GLA and Vertex AI endpoints without needing defensive workarounds.

Test cassette has been reviewed and contains no sensitive information.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: conradlee

tests/models/cassettes/test_google/test_google_recursive_schema_native_output_gemini_2_5_gla.yaml

@@ -0,0 +1,82 @@
+interactions:
+- request:
+    headers:
+      accept:
+      - '*/*'
+      accept-encoding:
+      - gzip, deflate
+      connection:
+      - keep-alive
+      content-length:
+      - '556'
+      content-type:
+      - application/json
+      host:
+      - generativelanguage.googleapis.com
+    method: POST
+    parsed_body:
+      contents:
+      - parts:
+        - text: Create a simple tree with root "A" and two children "B" and "C"
+        role: user
+      generationConfig:
+        responseJsonSchema:
+          $defs:
+            TreeNode:
+              description: A node in a tree structure.
+              properties:
+                children:
+                  default: []
+                  items:
+                    $ref: '#/$defs/TreeNode'
+                  type: array
+                value:
+                  type: string
+              required:
+              - value
+              title: TreeNode
+              type: object
+          $ref: '#/$defs/TreeNode'
+          title: TreeNode
+        responseMimeType: application/json
+        responseModalities:
+        - TEXT
+    uri: https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent
+  response:
+    headers:
+      alt-svc:
+      - h3=":443"; ma=2592000,h3-29=":443"; ma=2592000
+      content-length:
+      - '612'
+      content-type:
+      - application/json; charset=UTF-8
+      server-timing:
+      - gfet4t7; dur=1444
+      transfer-encoding:
+      - chunked
+      vary:
+      - Origin
+      - X-Origin
+      - Referer
+    parsed_body:
+      candidates:
+      - content:
+          parts:
+          - text: '{"value":"A","children":[{"value":"B"},{"value":"C"}]}'
+          role: model
+        finishReason: STOP
+        index: 0
+      modelVersion: gemini-2.5-flash
+      responseId: D08Yaa3eKYmznsEPt4u8gAk
+      usageMetadata:
+        candidatesTokenCount: 16
+        promptTokenCount: 20
+        promptTokensDetails:
+        - modality: TEXT
+          tokenCount: 20
+        thoughtsTokenCount: 183
+        totalTokenCount: 219
+    status:
+      code: 200
+      message: OK
+version: 1

tests/models/test_google.py

@@ -3226,6 +3226,29 @@ class TreeNode(BaseModel):
     assert {child.value for child in result.output.children} == {'B', 'C'}
 
 
+async def test_google_recursive_schema_native_output_gemini_2_5_gla(
+    allow_model_requests: None, google_provider: GoogleProvider
+):
+    """Test recursive schemas with gemini-2.5-flash on GLA.
+
+    This previously failed with 500 errors but should now work after Google's fix.
+    """
+    m = GoogleModel('gemini-2.5-flash', provider=google_provider)
+
+    class TreeNode(BaseModel):
+        """A node in a tree structure."""
+
+        value: str
+        children: list[TreeNode] = []
+
+    agent = Agent(m, output_type=NativeOutput(TreeNode))
+
+    result = await agent.run('Create a simple tree with root "A" and two children "B" and "C"')
+    assert result.output.value == snapshot('A')
+    assert len(result.output.children) == snapshot(2)
+    assert {child.value for child in result.output.children} == snapshot({'B', 'C'})
+
+
 async def test_google_dict_with_additional_properties_native_output(
     allow_model_requests: None, google_provider: GoogleProvider
 ):