diff --git a/tests/unit/interactions/test_openapi_compliance.py b/tests/unit/interactions/test_openapi_compliance.py
index d3f1183cea6..433b94f5983 100644
--- a/tests/unit/interactions/test_openapi_compliance.py
+++ b/tests/unit/interactions/test_openapi_compliance.py
@@ -9,6 +9,7 @@ Run with: pytest tests/unit/interactions/test_openapi_compliance.py -v
 
 import json
 import os
+import re
 from typing import Any, Dict
 from unittest.mock import MagicMock, patch
 
@@ -44,6 +45,24 @@ def _declared_type_value(variant_schema: Dict[str, Any]) -> Any:
     return type_property.get("const") or (enum_values[0] if len(enum_values) == 1 else None)
 
 
+def _schema_named(spec_dict: dict[str, Any], ref: str) -> dict[str, Any]:
+    return spec_dict["components"]["schemas"][ref.split("/")[-1]]
+
+
+def _create_request_schema(spec_dict: dict[str, Any]) -> dict[str, Any]:
+    """The model-interaction body POSTed to /interactions, found by endpoint since Google renames
+    the schema and now wraps it in a oneOf with the agent variant."""
+    for path, methods in spec_dict["paths"].items():
+        if path.endswith("/interactions") and "post" in methods:
+            body = methods["post"]["requestBody"]["content"]["application/json"]["schema"]
+            candidates = body.get("oneOf") or [body]
+            for candidate in candidates:
+                schema = _schema_named(spec_dict, candidate["$ref"]) if "$ref" in candidate else candidate
+                if "model" in schema.get("properties", {}):
+                    return schema
+    raise AssertionError("no model-interaction request body found on POST /interactions")
+
+
 @pytest.fixture(scope="module")
 def spec_dict() -> Dict[str, Any]:
     """Load raw spec dict for manual validation."""
@@ -56,16 +75,22 @@ def openapi_spec(spec_dict: Dict[str, Any]) -> OpenAPI:
     return OpenAPI.from_dict(spec_dict)
 
 
+def _interaction_item_path(paths: dict[str, Any], method: str) -> Any:
+    """`/…/interactions/{param}` for a method; the parameter's name is cosmetic and has changed."""
+    item = re.compile(r"/interactions/\{[^}/]+\}$")
+    return next((p for p, methods in paths.items() if item.search(p) and method in methods), None)
+
+
 class TestRequestCompliance:
     """Tests that our request bodies match the OpenAPI spec."""
 
     def test_create_model_interaction_request_schema(self, spec_dict):
-        """Verify CreateModelInteractionParams schema fields."""
-        schema = spec_dict["components"]["schemas"]["CreateModelInteractionParams"]
+        """Verify the model-interaction request body fields."""
+        schema = _create_request_schema(spec_dict)
 
-        # Required fields per spec
+        # `model` is required; `input` is optional now that a call can resume via previous_interaction_id
         assert "model" in schema["required"]
-        assert "input" in schema["required"]
+        assert "input" in schema["properties"]
 
         # Check our supported optional fields exist in spec
         our_optional_fields = [
@@ -88,8 +113,7 @@ class TestRequestCompliance:
 
     def test_input_types_match_spec(self, spec_dict):
         """Verify input field supports string, Content, Content[], Turn[]."""
-        schema = spec_dict["components"]["schemas"]["CreateModelInteractionParams"]
-        input_schema = schema["properties"]["input"]
+        input_schema = _create_request_schema(spec_dict)["properties"]["input"]
 
         # The input property may be inline oneOf or a $ref to InteractionsInput
         if "$ref" in input_schema:
@@ -311,11 +335,7 @@ class TestEndpointCompliance:
         """Verify GET /interactions/{id} endpoint exists."""
         paths = spec_dict["paths"]
 
-        get_path = None
-        for path, methods in paths.items():
-            if "{id}" in path and "interactions" in path and "get" in methods:
-                get_path = path
-                break
+        get_path = _interaction_item_path(paths, "get")
 
         assert get_path is not None, "GET /interactions/{id} endpoint not found"
         print(f"✓ Get endpoint: GET {get_path}")
@@ -324,11 +344,7 @@ class TestEndpointCompliance:
         """Verify DELETE /interactions/{id} endpoint exists."""
         paths = spec_dict["paths"]
 
-        delete_path = None
-        for path, methods in paths.items():
-            if "{id}" in path and "interactions" in path and "delete" in methods:
-                delete_path = path
-                break
+        delete_path = _interaction_item_path(paths, "delete")
 
         assert delete_path is not None, "DELETE /interactions/{id} endpoint not found"
         print(f"✓ Delete endpoint: DELETE {delete_path}")