simstack · Buld1n · Mar 17, 2026 · Mar 17, 2026
diff --git a/src/simstack/core/runner.py b/src/simstack/core/runner.py
@@ -27,11 +27,18 @@ async def initialize_default_resource():
         ResourceDefinition.resource_str == str(context.config.resource)
     )
 
+    if resource_def is None:
+        logger.warning(
+            "No ResourceDefinition found for '%s'; skipping default-resource initialization.",
+            str(context.config.resource),
+        )
+        return None
+
     if resource_def.is_default:
         config_path = context.config.project_root / "config.toml"
         if not config_path.exists():
             logger.warning(f"Default resource detected, but {config_path} not found.")
-            return
+            return resource_def
 
         try:
             with open(config_path, "rb") as f:
@@ -40,7 +47,7 @@ async def initialize_default_resource():
             active_dirs = config_data.get("active_dirs", [])
             if not active_dirs:
                 logger.info("No active_dirs found in config.toml.")
-                return
+                return resource_def
 
             logger.info(f"Default resource: initializing tables for {active_dirs}")
             await make_node_table(context.db.engine, dirs=active_dirs)
@@ -57,11 +64,12 @@ async def async_main(args):
 
     # Initialize tables if this is the default resource
     resource_def = await initialize_default_resource()
+    is_default_resource = bool(resource_def and resource_def.is_default)
 
     if args.resource:
         logger.info(f"Setting resource for runner to {args.resource}")
         runner_manager = RunnerManager(context.config.resource, detach=args.detach, no_pull=args.no_pull,
-                                       is_default=resource_def.is_default)
+                                       is_default=is_default_resource)
         await runner_manager.run_nodes_for_resource(args.polling_interval, 10, timeout=args.timeout)
 
 

diff --git a/tests/without_context/test_runner_default_resource.py b/tests/without_context/test_runner_default_resource.py
@@ -0,0 +1,77 @@
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
+
+import pytest
+
+from simstack.core import runner
+
+
+@pytest.mark.asyncio
+async def test_initialize_default_resource_returns_none_when_resource_is_missing(tmp_path, monkeypatch):
+    db = SimpleNamespace(find_one=AsyncMock(return_value=None))
+    config = SimpleNamespace(resource="docker", project_root=tmp_path)
+    monkeypatch.setattr(runner, "context", SimpleNamespace(db=db, config=config))
+
+    result = await runner.initialize_default_resource()
+
+    assert result is None
+
+
+@pytest.mark.asyncio
+async def test_initialize_default_resource_keeps_resource_when_config_toml_missing(tmp_path, monkeypatch):
+    resource_def = SimpleNamespace(is_default=True)
+    db = SimpleNamespace(find_one=AsyncMock(return_value=resource_def), engine=object())
+    config = SimpleNamespace(resource="docker", project_root=tmp_path)
+
+    make_node_table = AsyncMock()
+    make_model_table = AsyncMock()
+    monkeypatch.setattr(runner, "context", SimpleNamespace(db=db, config=config))
+    monkeypatch.setattr(runner, "make_node_table", make_node_table)
+    monkeypatch.setattr(runner, "make_model_table", make_model_table)
+
+    result = await runner.initialize_default_resource()
+
+    assert result is resource_def
+    make_node_table.assert_not_called()
+    make_model_table.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_async_main_uses_false_is_default_when_default_resource_init_returns_none(monkeypatch):
+    captured: dict[str, object] = {}
+
+    class DummyContext:
+        def __init__(self):
+            self.config = SimpleNamespace(resource="docker")
+
+        async def initialize(self, **kwargs):
+            self.config = SimpleNamespace(resource=kwargs.get("resource"))
+
+    class DummyRunnerManager:
+        def __init__(self, resource, *, detach, no_pull, is_default):
+            captured["resource"] = resource
+            captured["detach"] = detach
+            captured["no_pull"] = no_pull
+            captured["is_default"] = is_default
+
+        async def run_nodes_for_resource(self, polling_interval, *_args, timeout=None):
+            captured["polling_interval"] = polling_interval
+            captured["timeout"] = timeout
+
+    monkeypatch.setattr(runner, "context", DummyContext())
+    monkeypatch.setattr(runner, "initialize_default_resource", AsyncMock(return_value=None))
+    monkeypatch.setattr(runner, "RunnerManager", DummyRunnerManager)
+
+    args = SimpleNamespace(
+        resource="docker",
+        db_name=None,
+        detach=True,
+        no_pull=False,
+        polling_interval=5,
+        timeout=None,
+    )
+
+    await runner.async_main(args)
+
+    assert captured["is_default"] is False
+    assert captured["resource"] == "docker"