diff --git a/py/packages/genkit/src/genkit/ai/_base.py b/py/packages/genkit/src/genkit/ai/_base.py
index 4433597b47..edd39e2919 100644
--- a/py/packages/genkit/src/genkit/ai/_base.py
+++ b/py/packages/genkit/src/genkit/ai/_base.py
@@ -17,6 +17,7 @@
 """Base/shared implementation for Genkit user-facing API."""
 
 import asyncio
+import os
 import threading
 from collections.abc import Coroutine
 from http.server import HTTPServer
@@ -39,6 +40,9 @@
 
 T = TypeVar('T')
 
+_instance_count = -1
+_instance_lock = threading.Lock()
+
 
 class GenkitBase(GenkitRegistry):
     """Base class with shared infra for Genkit instances (sync and async)."""
@@ -58,6 +62,11 @@ def __init__(
                 server.
         """
         super().__init__()
+        global _instance_count
+        global _instance_lock
+        with _instance_lock:
+            _instance_count += 1
+            self.id = f'{os.getpid()}-{_instance_count}'
         self._initialize_server(reflection_server_spec)
         self._initialize_registry(model, plugins)
         define_generate_action(self.registry)
@@ -165,10 +174,10 @@ def _start_server(self, spec: ServerSpec, loop: asyncio.AbstractEventLoop) -> No
         """
         httpd = HTTPServer(
             (spec.host, spec.port),
-            make_reflection_server(registry=self.registry, loop=loop),
+            make_reflection_server(registry=self.registry, loop=loop, id=self.id),
         )
         # We need to write the runtime file closest to the point of starting up
         # the server to avoid race conditions with the manager's runtime
         # handler.
-        init_default_runtime(spec)
+        init_default_runtime(spec, self.id)
         httpd.serve_forever()
diff --git a/py/packages/genkit/src/genkit/ai/_server.py b/py/packages/genkit/src/genkit/ai/_server.py
index 51ab383ae0..45d8ced2b8 100644
--- a/py/packages/genkit/src/genkit/ai/_server.py
+++ b/py/packages/genkit/src/genkit/ai/_server.py
@@ -63,6 +63,7 @@ def url(self) -> str:
 def create_runtime(
     runtime_dir: str,
     reflection_server_spec: ServerSpec,
+    id: str,
     at_exit_fn: Callable[[Path], None] | None = None,
 ) -> Path:
     """Create a runtime configuration for use with the genkit CLI.
@@ -87,7 +88,7 @@ def create_runtime(
     runtime_file_path = Path(os.path.join(runtime_dir, runtime_file_name))
     metadata = json.dumps({
         'reflectionApiSpecVersion': 1,
-        'id': f'{os.getpid()}',
+        'id': id,
         'pid': os.getpid(),
         'genkitVersion': 'py/' + DEFAULT_GENKIT_VERSION,
         'reflectionServerUrl': reflection_server_spec.url,
@@ -104,11 +105,7 @@ def cleanup_runtime() -> None:
     return runtime_file_path
 
 
-def init_default_runtime(spec: ServerSpec) -> None:
+def init_default_runtime(spec: ServerSpec, id: str) -> None:
     """Initialize the runtime for the Genkit instance."""
     runtimes_dir = os.path.join(os.getcwd(), '.genkit/runtimes')
-    create_runtime(
-        runtime_dir=runtimes_dir,
-        reflection_server_spec=spec,
-        at_exit_fn=os.remove,
-    )
+    create_runtime(runtime_dir=runtimes_dir, reflection_server_spec=spec, id=id, at_exit_fn=os.remove)
diff --git a/py/packages/genkit/src/genkit/core/reflection.py b/py/packages/genkit/src/genkit/core/reflection.py
index 22067edc23..03284eadab 100644
--- a/py/packages/genkit/src/genkit/core/reflection.py
+++ b/py/packages/genkit/src/genkit/core/reflection.py
@@ -76,6 +76,7 @@
 def make_reflection_server(
     registry: Registry,
     loop: asyncio.AbstractEventLoop,
+    id: str,
     encoding='utf-8',
     quiet=True,
 ):
@@ -113,11 +114,19 @@ def do_GET(self) -> None:  # noqa: N802
             For the /api/actions endpoint, returns a JSON object mapping action
             keys to their metadata, including input/output schemas.
             """
-            if urllib.parse.urlparse(self.path).path == '/api/__health':
+            parsed_url = urllib.parse.urlparse(self.path)
+            if parsed_url.path == '/api/__health':
+                query_params = urllib.parse.parse_qs(parsed_url.query)
+                expected_id = query_params.get('id', [None])[0]
+                if expected_id is not None and expected_id != id:
+                    self.send_response(500)
+                    self.end_headers()
+                    return
+
                 self.send_response(200, 'OK')
                 self.end_headers()
 
-            elif self.path == '/api/actions':
+            elif parsed_url.path == '/api/actions':
                 self.send_response(200)
                 self.send_header('content-type', 'application/json')
                 self.end_headers()
diff --git a/py/packages/genkit/tests/genkit/veneer/server_test.py b/py/packages/genkit/tests/genkit/veneer/server_test.py
index 77a7162223..302c710d72 100644
--- a/py/packages/genkit/tests/genkit/veneer/server_test.py
+++ b/py/packages/genkit/tests/genkit/veneer/server_test.py
@@ -39,19 +39,19 @@ def test_create_runtime() -> None:
         spec = ServerSpec(port=3100)
 
         # Test runtime file creation
-        runtime_path = create_runtime(temp_dir, spec)
+        runtime_path = create_runtime(temp_dir, spec, '123')
         assert runtime_path.exists()
 
         # Verify file content
         content = json.loads(runtime_path.read_text(encoding='utf-8'))
         assert isinstance(content, dict)
-        assert 'id' in content
+        assert content['id'] == '123'
         assert 'pid' in content
         assert content['reflectionServerUrl'] == 'http://localhost:3100'
         assert 'timestamp' in content
 
         # Test directory creation
         new_dir = os.path.join(temp_dir, 'new_dir')
-        runtime_path = create_runtime(new_dir, spec)
+        runtime_path = create_runtime(new_dir, spec, '123')
         assert os.path.exists(new_dir)
         assert runtime_path.exists()