diff --git a/tests/conftest.py b/tests/conftest.py
index bac107ea..ab0a393e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -22,6 +22,29 @@ if project_root not in sys.path:
 from defer.sugar import install
 install()
 
+# Per the user spec (startup_speedup_20260606 spec.md:2.2 Layer 3,
+# and the message in workflow.md about warmup notifications): the
+# AppController's warmup mechanism loads heavy modules on the _io_pool
+# background thread at startup. Tests that touch these modules must
+# wait for warmup to complete; otherwise they race against a partial
+# google.genai import and hit "partially initialized" errors.
+#
+# Wait for the warmup before any test runs. The AppController is
+# created in a session-scoped fixture; if it already exists (e.g.,
+# the live_gui fixture also creates one), this call is a no-op or
+# fast (warmup already done).
+from src.app_controller import AppController
+_warmup_app_controller = AppController()
+if not _warmup_app_controller.wait_for_warmup(timeout=60.0):
+ import warnings
+ warnings.warn(
+  "AppController warmup did not complete within 60s. "
+  "Tests that depend on warmup modules (google.genai, anthropic, "
+  "openai, etc.) may fail.",
+  RuntimeWarning,
+  stacklevel=2,
+ )
+
 from src.gui_2 import App
 
 class VerificationLogger: