diff --git a/pyproject.toml b/pyproject.toml
index 24d5428..4c15014 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -104,6 +104,11 @@ ignore = [
 [tool.ruff.lint.per-file-ignores]
 "__init__.py" = ["F401", "F403"]
 
+[tool.ruff.lint.flake8-type-checking]
+# pydantic evaluates model annotations at runtime, so field-type imports must stay importable at
+# runtime (not moved into a TYPE_CHECKING block) or model building raises PydanticUndefinedAnnotation.
+runtime-evaluated-base-classes = ["pydantic.BaseModel"]
+
 [tool.ruff.lint.pydocstyle]
 convention = "google"
 
diff --git a/rowan/folder.py b/rowan/folder.py
index a6946b2..3834732 100644
--- a/rowan/folder.py
+++ b/rowan/folder.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from datetime import datetime
 from typing import TYPE_CHECKING, Any, Self
 
 from pydantic import BaseModel
@@ -8,8 +9,6 @@
 from .utils import api_client, get_project_uuid
 
 if TYPE_CHECKING:
-    from datetime import datetime
-
     from .workflows.base import Workflow