diff --git a/tinygrad/gradient.py b/tinygrad/gradient.py
index 3527bd963b..dbcb455c7a 100644
--- a/tinygrad/gradient.py
+++ b/tinygrad/gradient.py
@@ -5,8 +5,8 @@ from tinygrad.helpers import argsort
 
 def cat_gradient(ctx:UOp, ret:UOp) -> tuple[UOp, ...]:
   axis = ret.arg
-  dim_cumsum = list(itertools.accumulate([s.shape[axis] for s in ret.src], initial=0))
-  return tuple(ctx.shrink(tuple([(dim_cumsum[i], dim_cumsum[i+1]) if j==axis else (0, ctx.shape[j])
+  dim_acc = list(itertools.accumulate([s.shape[axis] for s in ret.src], initial=0))
+  return tuple(ctx.shrink(tuple([(dim_acc[i], dim_acc[i+1]) if j==axis else (0, ctx.shape[j])
     for j in range(len(ctx.shape))])) for i in range(len(ret.src)))
 
 def reduce_gradient(ctx:UOp, ret:UOp, op:Ops):
diff --git a/tinygrad/schedule/rangeify.py b/tinygrad/schedule/rangeify.py
index 69561c12f4..f3e0a15506 100644
--- a/tinygrad/schedule/rangeify.py
+++ b/tinygrad/schedule/rangeify.py
@@ -114,9 +114,8 @@ def resolve_call(c:UOp, allow_param_mismatch=True) -> UOp|None:
 
 def lower_cat(cat:UOp) -> UOp:
   axis = cat.arg
-  dim_cumsum = list(itertools.accumulate([s.shape[axis] for s in cat.src], initial=0))
-  padded = [s.pad(tuple((dim_cumsum[i], dim_cumsum[-1]-dim_cumsum[i+1]) if j==axis else (0,0)
-    for j in range(len(s.shape)))) for i,s in enumerate(cat.src)]
+  dim_acc = list(itertools.accumulate([s.shape[axis] for s in cat.src], initial=0))
+  padded = [s.pad(tuple((dim_acc[i], dim_acc[-1]-dim_acc[i+1]) if j==axis else (0,0) for j in range(len(s.shape)))) for i,s in enumerate(cat.src)]
   ret = padded[0]
   for p in padded[1:]: ret = ret.alu(Ops.ADD, p)
   return ret
diff --git a/tinygrad/uop/ops.py b/tinygrad/uop/ops.py
index 5aa89deaa1..4793f54a56 100644
--- a/tinygrad/uop/ops.py
+++ b/tinygrad/uop/ops.py
@@ -264,14 +264,12 @@ class UOp(OpMixin, metaclass=UOpMetaClass):
       case Ops.MULTI if len(self.src) == 0: return None
 
       case Ops.CAT:
-        shapes = [s._shape for s in self.src]
-        if any(s is None for s in shapes): raise RuntimeError("CAT requires all sources to have shapes")
+        shapes = [s.shape for s in self.src]
         axis = self.arg
-        if axis == -1: return (len(shapes),) + shapes[0]  # type: ignore  # new leading axis (stack)
         for s in shapes[1:]:
-          if len(s) != len(shapes[0]) or not all(a==b for i,(a,b) in enumerate(zip(s, shapes[0])) if i!=axis):  # type: ignore
+          if len(s) != len(shapes[0]) or not all(a==b for i,(a,b) in enumerate(zip(s, shapes[0])) if i!=axis):
             raise ValueError(f"CAT shape mismatch: {shapes}")
-        return tuple(ssimplify(sum(s[i] for s in shapes)) if i==axis else shapes[0][i] for i in range(len(shapes[0])))  # type: ignore
+        return tuple(ssimplify(sum(s[i] for s in shapes)) if i==axis else shapes[0][i] for i in range(len(shapes[0])))
 
     # movement ops change the shape
     # NOTE: ssimplify is required because the shape needs to be canonical for broadcasting and same shape checking
diff --git a/tinygrad/viz/serve.py b/tinygrad/viz/serve.py
index 9b562c0fb1..b042fceb60 100755
--- a/tinygrad/viz/serve.py
+++ b/tinygrad/viz/serve.py
@@ -47,7 +47,7 @@ uops_colors = {Ops.LOAD: "#ffc0c0", Ops.STORE: "#87CEEB", Ops.CONST: "#e0e0e0",
                **{x:"#f2cb91" for x in {Ops.DEFINE_LOCAL, Ops.DEFINE_REG}}, Ops.REDUCE_AXIS: "#FF6B6B",
                Ops.RANGE: "#c8a0e0", Ops.ASSIGN: "#909090", Ops.BARRIER: "#ff8080", Ops.IF: "#c8b0c0", Ops.SPECIAL: "#c0c0ff",
                Ops.INDEX: "#cef263", Ops.WMMA: "#efefc0", Ops.MULTI: "#f6ccff", Ops.INS: "#eec4ff",
-               **{x:"#D8F9E4" for x in GroupOp.Movement}, **{x:"#ffffc0" for x in GroupOp.ALU}, Ops.THREEFRY:"#ffff80",
+               **{x:"#D8F9E4" for x in GroupOp.Movement}, **{x:"#ffffc0" for x in GroupOp.ALU}, Ops.THREEFRY:"#ffff80", Ops.CAT:"#C1FFD7",
                Ops.BUFFER_VIEW: "#E5EAFF", Ops.BUFFER: "#B0BDFF", Ops.COPY: "#a040a0", Ops.ENCDEC: "#bf71b6",
                Ops.CALL: "#00B7C8", Ops.PARAM: "#14686F", Ops.SOURCE: "#c0c0c0", Ops.LINEAR: "#7DF4FF", Ops.BINARY: "#404040",
                Ops.ALLREDUCE: "#ff40a0", Ops.MSELECT: "#d040a0", Ops.MSTACK: "#d040a0", Ops.CONTIGUOUS: "#FFC14D",