diff --git a/src/autora/state.py b/src/autora/state.py
index 76baeb54..da276fa7 100644
--- a/src/autora/state.py
+++ b/src/autora/state.py
@@ -23,6 +23,7 @@
     Dict,
     Generic,
     List,
+    Literal,
     Mapping,
     Optional,
     Protocol,
@@ -714,7 +715,8 @@ def add_field(
         type_=MISSING,
         default=MISSING,
         default_factory=MISSING,
-        metadata: Optional[Mapping] = None,
+        delta: Literal["replace", "extend", "append"] = "replace",
+        converter: Optional[Callable] = None,
     ):
         """
         Return a new copy of the dataclass with an additional field
@@ -764,9 +766,18 @@ def add_field(
         >>> s.add_field("f", type_=int, value="a string, not an int")
         StateDataClass(f='a string, not an int')
 
-        You can add metadata like a delta:
+        By default, fields are replaced if modified by Deltas:
+        >>> s.add_field("h", value=1) + Delta(h=2)
+        StateDataClass(h=2)
+
+        (This is the same as:
+        >>> s.add_field("h", value=1, delta="replace") + Delta(h=2)
+        StateDataClass(h=2)
+
+        You can specify a different delta type:
         >>> u = s.add_field("g", type_=List[int], default_factory=list, delta="extend")
         >>> u = u + Delta(g=[3]) + Delta(g=[4])
+        >>> u
         StateDataClass(g=[3, 4])
 
         >>> v = u.add_field("h", type_=int, default=None, delta="replace")
@@ -776,7 +787,18 @@ def add_field(
         >>> v + Delta(h=1) + Delta(h=2)
         StateDataClass(g=[3, 4], h=2)
 
-        >>>
+        >>> w = v.add_field("i", type_=List[int], default_factory=list, delta="append")
+        >>> w + Delta(i=3) + Delta(i=9) + Delta(i=27)
+        StateDataClass(g=[3, 4], h=None, i=[3, 9, 27])
+
+        You can specify a converter:
+        >>> x = s.add_field("df", type_=pd.DataFrame, default=None, converter=pd.DataFrame)
+        >>> x + Delta(df = {"a": [1, 2, 3], "b": list("abc")})
+        StateDataClass(df=   a  b
+        0  1  a
+        1  2  b
+        2  3  c)
+
         """
         _field_kwargs = {
             k: v
@@ -784,6 +806,12 @@ def add_field(
             if v is not MISSING
         }
 
+        _field_kwargs["metadata"] = {
+            k: v
+            for k, v in dict(delta=delta, converter=converter).items()
+            if v is not None
+        }
+
         _field = field(**_field_kwargs)
         _dataclass_params = {
             key: getattr(getattr(self, "__dataclass_params__"), key)
@@ -796,11 +824,14 @@ def add_field(
             bases=(self.__class__,),
             **_dataclass_params,
         )
+
         if value is not MISSING:
             new_value = {name: value}
         else:
             new_value = {}
+
         new = new_class(**new_value, **asdict(self))
+
         return new