diff --git a/agent/component/base.py b/agent/component/base.py
index f8f54c004..4cba409ca 100644
--- a/agent/component/base.py
+++ b/agent/component/base.py
@@ -529,8 +529,12 @@ class ComponentBase(ABC):
     @staticmethod
     def string_format(content: str, kv: dict[str, str]) -> str:
         for n, v in kv.items():
+            def repl(_match, val=v):
+                return str(val) if val is not None else ""
             content = re.sub(
-                r"\{%s\}" % re.escape(n), v, content
+                r"\{%s\}" % re.escape(n),
+                repl,
+                content
             )
         return content