Fix: Flux.2 reference images presented in random order

invokeai/app/services/shared/graph.py

@@ -1209,8 +1209,12 @@ def _prepare_inputs(self, node: BaseInvocation):
         # Inputs must be deep-copied, else if a node mutates the object, other nodes that get the same input
         # will see the mutation.
         if isinstance(node, CollectInvocation):
-            item_edges = [e for e in input_edges if e.destination.field == ITEM_FIELD]
-            item_edges.sort(key=lambda e: (self._get_iteration_path(e.source.node_id), e.source.node_id))
+            # Enumerate to preserve insertion order as a tiebreaker when iteration paths are equal.
+            # Using source_node_id as a tiebreaker would produce random ordering for non-iterated
+            # direct connections (e.g. multiple reference images) because node IDs are random UUIDs.
+            item_edges_indexed = list(enumerate(e for e in input_edges if e.destination.field == ITEM_FIELD))
+            item_edges_indexed.sort(key=lambda t: (self._get_iteration_path(t[1].source.node_id), t[0]))
+            item_edges = [e for _, e in item_edges_indexed]
 
             output_collection = [copydeep(getattr(self.results[e.source.node_id], e.source.field)) for e in item_edges]
             node.collection = output_collection

tests/test_graph_execution_state.py

@@ -300,6 +300,33 @@ def test_graph_validate_self_collector_without_item_inputs_raises_invalid_edge_e
         graph.validate_self()
 
 
+def test_collect_preserves_insertion_order():
+    """Items directly connected to a CollectInvocation (no iteration) must be collected in insertion order.
+
+    This guards against the bug where items were sorted by source node ID (random UUID), producing
+    non-deterministic ordering for e.g. multiple Flux.2 reference images.
+    """
+    graph = Graph()
+    prompts = ["first", "second", "third"]
+    graph.add_node(PromptTestInvocation(id="a", prompt=prompts[0]))
+    graph.add_node(PromptTestInvocation(id="b", prompt=prompts[1]))
+    graph.add_node(PromptTestInvocation(id="c", prompt=prompts[2]))
+    graph.add_node(CollectInvocation(id="collect"))
+    # Add edges in the intended left-to-right order
+    graph.add_edge(create_edge("a", "prompt", "collect", "item"))
+    graph.add_edge(create_edge("b", "prompt", "collect", "item"))
+    graph.add_edge(create_edge("c", "prompt", "collect", "item"))
+
+    g = GraphExecutionState(graph=graph)
+    invoke_next(g)  # a
+    invoke_next(g)  # b
+    invoke_next(g)  # c
+    n_collect, result = invoke_next(g)
+
+    assert isinstance(n_collect, CollectInvocation)
+    assert g.results[n_collect.id].collection == prompts
+
+
 def test_are_connection_types_compatible_accepts_subclass_to_base():
     """A subclass output should be connectable to a base-class input.