fix(cli): wait for the import warm-up before importing the agents SDK on the main thread

The warm-up thread imports strix.core.runner while warm_up_llm and
preflight_model_connection import agents.models.interface. Both walk the
agents SDK graph from different entry points, CPython fails one side to
break the import-lock cycle, and the orphan purge then removes agents.*
from sys.modules while the main thread is still importing it, crashing
strix -n with KeyError: 'agents.models'.

strix/interface/main.py

@@ -41,6 +41,7 @@ from strix.interface.update_check import (
 from strix.interface.utils import (
     build_final_stats_text,
 )
+from strix.llm.warmup import start_import_warmup, wait_for_import_warmup
 from strix.telemetry import posthog, scarf
 from strix.telemetry.logging import configure_dependency_logging
 
@@ -135,6 +136,8 @@ def _subscription_error_hint(exc: BaseException) -> str | None:
 
 
 async def warm_up_llm(show_model_warning: bool = True) -> None:
+    wait_for_import_warmup()
+
     from agents.models.interface import ModelTracing
 
     from strix.config.models import (
@@ -450,8 +453,6 @@ def main() -> None:
 
         sys.exit(run_cloud(sys.argv[2:]))
 
-    from strix.llm.warmup import start_import_warmup
-
     start_import_warmup()
 
     args = parse_arguments()

strix/interface/scan_setup.py

@@ -31,6 +31,7 @@ from strix.interface.utils import (
     stage_api_specs,
     write_fetched_collection,
 )
+from strix.llm.warmup import wait_for_import_warmup
 from strix.telemetry import posthog, scarf
 from strix.utils.api_spec import (
     SpecParseError,
@@ -64,6 +65,8 @@ async def preflight_model_connection(
     settings: Settings | None = None,
 ) -> None:
     """Verify the configured model route before starting a scan."""
+    wait_for_import_warmup()
+
     from agents.models.interface import ModelTracing
 
     from strix.config.models import StrixProvider, configure_sdk_model_defaults

strix/llm/warmup.py

@@ -80,3 +80,17 @@ def start_import_warmup(modules: tuple[str, ...] = WARMUP_MODULES) -> threading.
         )
         _thread.start()
         return _thread
+
+
+def wait_for_import_warmup(timeout: float | None = None) -> None:
+    """Block until the warm-up thread has finished, if one was started.
+
+    Call this before the first import of a warmed module on another thread.
+    Two threads walking the same package graph hold each other's import locks,
+    CPython breaks the cycle by failing one side, and the failed side's
+    orphan purge can remove a package the other thread is still importing.
+    """
+    with _lock:
+        thread = _thread
+    if thread is not None and thread is not threading.current_thread():
+        thread.join(timeout)

tests/test_import_warmup.py

@@ -92,6 +92,32 @@ def test_failed_warm_import_purges_orphaned_submodules() -> None:
     assert result.returncode == 0, result.stderr
 
 
+def test_wait_for_import_warmup_lets_main_thread_import_the_agents_graph() -> None:
+    result = _run(
+        """
+        import sys
+
+        from strix.llm.warmup import start_import_warmup, wait_for_import_warmup
+
+        # Same shape as the CLI: warm-up starts, then the main thread needs a
+        # module from the middle of the agents graph before it has finished.
+        start_import_warmup()
+        wait_for_import_warmup()
+
+        from agents.models.interface import ModelTracing  # noqa: F401
+
+        assert "agents" in sys.modules
+        assert "agents.models" in sys.modules
+        assert "strix.core.runner" in sys.modules
+        """
+    )
+    assert result.returncode == 0, result.stderr
+
+
+def test_wait_for_import_warmup_is_a_no_op_without_a_thread() -> None:
+    warmup.wait_for_import_warmup(timeout=0)
+
+
 def test_purge_does_not_touch_preexisting_or_healthy_modules() -> None:
     before = frozenset(sys.modules) - {"strix.llm.warmup"}
     warmup._purge_orphaned_modules(before)