diff --git a/examples/00-hello-world/main.py b/examples/00-hello-world/main.py
index 9d6ba7d..82b0cc6 100644
--- a/examples/00-hello-world/main.py
+++ b/examples/00-hello-world/main.py
@@ -178,8 +178,12 @@ def route(state: PipelineState) -> str:
 async def trace(event: NodeEvent) -> None:
     # OpenAIProvider emits NodeEvent-shaped events for LLM-span
     # tracking under a sentinel namespace; those have post_state=None.
-    # Filter to events that carry a state snapshot before reading it.
-    if event.phase == "completed" and event.error is None and event.post_state is not None:
+    # Filter to events that carry a PipelineState snapshot before
+    # reading it. The isinstance check both narrows the type for
+    # static checkers (post_state is typed as the base State, not
+    # PipelineState) and acts as a defensive guard against any
+    # foreign-state observer event the engine might dispatch.
+    if event.phase == "completed" and event.error is None and isinstance(event.post_state, PipelineState):
         print(f"{event.node_name}: sources={event.post_state.sources}")
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 6dd7c3c..2aa829e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -79,7 +79,7 @@ examples = [
 packages = ["src/openarmature"]
 
 [tool.pyright]
-include = ["src", "tests"]
+include = ["src", "tests", "examples"]
 pythonVersion = "3.12"
 typeCheckingMode = "strict"
 reportMissingTypeStubs = false