diff --git a/altair/expr/core.py b/altair/expr/core.py
index e0e9b11f9b..8c18b291ea 100644
--- a/altair/expr/core.py
+++ b/altair/expr/core.py
@@ -1,5 +1,4 @@
 from ..utils import SchemaBase
-from ..vegalite.v5.schema.core import ExprRef
 
 
 class DatumType(object):
@@ -194,7 +193,7 @@ def __init__(self, name, args):
         super(FunctionExpressionReference, self).__init__(name=name, args=args)
 
     def __repr__(self):
-        args = ",".join(_js_repr(arg) for arg in self.args)
+        args = ",".join(str(arg) for arg in self.args)
         return "{name}({args})".format(name=self.name, args=args)
 
 
diff --git a/altair/vegalite/v5/api.py b/altair/vegalite/v5/api.py
index 6396b534b4..fb638e943e 100644
--- a/altair/vegalite/v5/api.py
+++ b/altair/vegalite/v5/api.py
@@ -15,6 +15,149 @@
 from .display import renderers, VEGALITE_VERSION, VEGAEMBED_VERSION, VEGA_VERSION
 from .theme import themes
 
+# ------------------------------------------------------------------------
+# ExprRef proxies
+def __add__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("+", self.expr, other))
+
+
+def __radd__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("+", other, self.expr))
+
+
+def __sub__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("-", self.expr, other))
+
+
+def __rsub__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("-", other, self.expr))
+
+
+def __mul__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("*", self.expr, other))
+
+
+def __rmul__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("*", other, self.expr))
+
+
+def __truediv__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("/", self.expr, other))
+
+
+def __rtruediv__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("/", other, self.expr))
+
+
+def __mod__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("%", self.name, other))
+
+
+def __rmod__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("%", other, self.name))
+
+
+def __pow__(self, other):
+    # "**" Javascript operator is not supported in all browsers
+    return ExprRef(expr.core.FunctionExpressionReference("pow", (self.name, other)))
+
+
+def __rpow__(self, other):
+    # "**" Javascript operator is not supported in all browsers
+    return ExprRef(expr.core.FunctionExpressionReference("pow", (other, self.name)))
+
+
+def __neg__(self):
+    return ExprRef(expr.core.UnaryExpressionReference("-", self.name))
+
+
+def __pos__(self):
+    return ExprRef(expr.core.UnaryExpressionReference("+", self.name))
+
+
+# comparison operators
+
+
+def __eq__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("===", self.name, other))
+
+
+def __ne__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("!==", self.name, other))
+
+
+def __gt__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference(">", self.name, other))
+
+
+def __lt__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("<", self.name, other))
+
+
+def __ge__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference(">=", self.name, other))
+
+
+def __le__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("<=", self.name, other))
+
+
+def __abs__(self):
+    return ExprRef(expr.core.FunctionExpressionReference("abs", (self.name,)))
+
+
+# logical operators
+
+
+def __and__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("&&", self.name, other))
+
+
+def __rand__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("&&", other, self.name))
+
+
+def __or__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("||", self.name, other))
+
+
+def __ror__(self, other):
+    return ExprRef(expr.core.BinaryExpressionReference("||", other, self.name))
+
+
+def __invert__(self):
+    return ExprRef(expr.core.UnaryExpressionReference("!", self.name))
+
+
+ExprRef.__add__ = __add__
+ExprRef.__radd__ = __radd__
+ExprRef.__sub__ = __sub__
+ExprRef.__rsub__ = __rsub__
+ExprRef.__mul__ = __mul__
+ExprRef.__rmul__ = __rmul__
+ExprRef.__truediv__ = __truediv__
+ExprRef.__rtruediv__ = __rtruediv__
+ExprRef.__div__ = __truediv__
+ExprRef.__rdiv__ = __rtruediv__
+ExprRef.__mod__ = __mod__
+ExprRef.__rmod__ = __rmod__
+ExprRef.__pow__ = __pow__
+ExprRef.__rpow__ = __rpow__
+ExprRef.__neg__ = __neg__
+ExprRef.__pos__ = __pos__
+ExprRef.__eq__ = __eq__
+ExprRef.__ne__ = __ne__
+ExprRef.__gt__ = __gt__
+ExprRef.__lt__ = __lt__
+ExprRef.__ge__ = __ge__
+ExprRef.__le__ = __le__
+ExprRef.__abs__ = __abs__
+ExprRef.__and__ = __and__
+ExprRef.__rand__ = __rand__
+ExprRef.__or__ = __or__
+ExprRef.__ror__ = __ror__
+ExprRef.__invert__ = __invert__
+
 
 # ------------------------------------------------------------------------
 # Data Utilities
diff --git a/altair/vegalite/v5/tests/test_api.py b/altair/vegalite/v5/tests/test_api.py
index 450553f3c6..21514e817d 100644
--- a/altair/vegalite/v5/tests/test_api.py
+++ b/altair/vegalite/v5/tests/test_api.py
@@ -11,7 +11,7 @@
 import pytest
 import pandas as pd
 
-import altair.vegalite.v4 as alt
+import altair.vegalite.v5 as alt
 
 try:
     import altair_saver  # noqa: F401
@@ -956,3 +956,26 @@ def test_validate_dataset():
     jsn = chart.to_json()
 
     assert jsn
+
+
+def test_layer_marks_raise_width():
+    import pandas as pd
+
+    no_data = pd.DataFrame()
+
+    c = alt.Chart(no_data).mark_circle().properties(width=100)
+    dct = (c + c).to_dict()
+
+    assert dct["width"] == 100
+    assert "width" not in dct["layer"][0].keys()
+
+
+def test_expr_class_proxies():
+    be = alt.datum.value / 1000
+    year_slider = alt.binding_range(min=0, max=1000, step=5)
+    size_var = alt.variable(bind=year_slider, value=200, name="sample")
+    expr_div = size_var / 1000
+    expr_pow = size_var ** 2 + 1
+
+    assert expr_div.expr == "sample / 1000"
+    assert expr_pow.expr == "pow(sample,2) + 1"