@@ -56,6 +56,8 @@ def add_keys(self, node_ids):
         for node_id in node_ids:
             if node_id in self.keys:
                 continue
+            if not self.dynprompt.has_node(node_id):
+                continue
             node = self.dynprompt.get_node(node_id)
             self.keys[node_id] = (node_id, node["class_type"])
             self.subcache_keys[node_id] = (node_id, node["class_type"])
@@ -74,6 +76,8 @@ def add_keys(self, node_ids):
         for node_id in node_ids:
             if node_id in self.keys:
                 continue
+            if not self.dynprompt.has_node(node_id):
+                continue
             node = self.dynprompt.get_node(node_id)
             self.keys[node_id] = self.get_node_signature(self.dynprompt, node_id)
             self.subcache_keys[node_id] = (node_id, node["class_type"])
@@ -87,6 +91,9 @@ def get_node_signature(self, dynprompt, node_id):
         return to_hashable(signature)
 
     def get_immediate_node_signature(self, dynprompt, node_id, ancestor_order_mapping):
+        if not dynprompt.has_node(node_id):
+            # This node doesn't exist -- we can't cache it.
+            return [float("NaN")]
         node = dynprompt.get_node(node_id)
         class_type = node["class_type"]
         class_def = nodes.NODE_CLASS_MAPPINGS[class_type]
@@ -112,6 +119,8 @@ def get_ordered_ancestry(self, dynprompt, node_id):
         return ancestors, order_mapping
 
     def get_ordered_ancestry_internal(self, dynprompt, node_id, ancestors, order_mapping):
+        if not dynprompt.has_node(node_id):
+            return
         inputs = dynprompt.get_node(node_id)["inputs"]
         input_keys = sorted(inputs.keys())
         for key in input_keys:
 
@@ -357,6 +357,25 @@ def test_dynamic_cycle_error(self, client: ComfyClient, builder: GraphBuilder):
             assert 'prompt_id' in e.args[0], f"Did not get back a proper error message: {e}"
             assert e.args[0]['node_id'] == generator.id, "Error should have been on the generator node"
 
+    def test_missing_node_error(self, client: ComfyClient, builder: GraphBuilder):
+        g = builder
+        input1 = g.node("StubImage", content="BLACK", height=512, width=512, batch_size=1)
+        input2 = g.node("StubImage", id="removeme", content="WHITE", height=512, width=512, batch_size=1)
+        input3 = g.node("StubImage", content="WHITE", height=512, width=512, batch_size=1)
+        mask = g.node("StubMask", value=0.5, height=512, width=512, batch_size=1)
+        mix1 = g.node("TestLazyMixImages", image1=input1.out(0), image2=input2.out(0), mask=mask.out(0))
+        mix2 = g.node("TestLazyMixImages", image1=input1.out(0), image2=input3.out(0), mask=mask.out(0))
+        # We have multiple outputs. The first is invalid, but the second is valid
+        g.node("SaveImage", images=mix1.out(0))
+        g.node("SaveImage", images=mix2.out(0))
+        g.remove_node("removeme")
+        
+        client.run(g)
+
+        # Add back in the missing node to make sure the error doesn't break the server
+        input2 = g.node("StubImage", id="removeme", content="WHITE", height=512, width=512, batch_size=1)
+        client.run(g)
+
     def test_custom_is_changed(self, client: ComfyClient, builder: GraphBuilder):
         g = builder
         # Creating the nodes in this specific order previously caused a bug
@@ -450,8 +469,8 @@ def test_output_reuse(self, client: ComfyClient, builder: GraphBuilder):
         g = builder
         input1 = g.node("StubImage", content="BLACK", height=512, width=512, batch_size=1)
 
-        output1 = g.node("PreviewImage", images=input1.out(0))
-        output2 = g.node("PreviewImage", images=input1.out(0))
+        output1 = g.node("SaveImage", images=input1.out(0))
+        output2 = g.node("SaveImage", images=input1.out(0))
 
         result = client.run(g)
         images1 = result.get_images(output1)