invoke-ai/InvokeAI · error · InvalidEdgeError

Edge already exists ({edge})

Error message

Edge already exists ({edge})

What it means

InvalidEdgeError raised by _validate_edge_destination_uniqueness() when a destination input field already has an incoming edge. Most input fields accept exactly one edge; only CollectInvocation's 'item' field may receive many. This prevents silently overwriting or duplicating a node's input.

Source

Thrown at invokeai/app/services/shared/graph.py:1924

        """Checks if the destination field for an edge is of type typing.Any"""
        return get_input_field_type(self.get_node(edge.destination.node_id), edge.destination.field) == Any

    def _is_destination_field_list_of_Any(self, edge: Edge) -> bool:
        """Checks if the destination field for an edge is of type typing.Any"""
        return get_input_field_type(self.get_node(edge.destination.node_id), edge.destination.field) == list[Any]

    def _get_edge_nodes(self, edge: Edge) -> tuple[BaseInvocation, BaseInvocation]:
        try:
            return self.get_node(edge.source.node_id), self.get_node(edge.destination.node_id)
        except NodeNotFoundError:
            raise InvalidEdgeError(f"One or both nodes don't exist ({edge})")

    def _validate_edge_destination_uniqueness(self, edge: Edge, destination_node: BaseInvocation) -> None:
        input_edges = self._get_input_edges(edge.destination.node_id, edge.destination.field)
        if len(input_edges) > 0 and (
            not isinstance(destination_node, CollectInvocation) or edge.destination.field != ITEM_FIELD
        ):
            raise InvalidEdgeError(f"Edge already exists ({edge})")

    def _validate_edge_would_not_create_cycle(self, edge: Edge) -> None:
        graph = self.nx_graph_flat()
        graph.add_edge(edge.source.node_id, edge.destination.node_id)
        if not nx.is_directed_acyclic_graph(graph):
            raise InvalidEdgeError(f"Edge creates a cycle in the graph ({edge})")

    def _validate_edge_field_compatibility(
        self, edge: Edge, source_node: BaseInvocation, destination_node: BaseInvocation
    ) -> None:
        if isinstance(destination_node, CallSavedWorkflowInvocation) and is_call_saved_workflow_dynamic_input(
            edge.destination.field
        ):
            return
        if not are_connections_compatible(source_node, edge.source.field, destination_node, edge.destination.field):
            raise InvalidEdgeError(f"Field types are incompatible ({edge})")

    def _validate_iterator_edge_rules(

View on GitHub (pinned to 0b6a024f2f)

Solutions

1. Remove the existing edge into that field before adding the new one
2. If you need to merge multiple outputs, route them through a CollectInvocation item field
3. Make graph construction idempotent (check for the edge before adding)
4. In the UI, delete the old connection first when rewiring

Example fix

// before
g.add_edge(a, "image", denoise, "image")
g.add_edge(b, "image", denoise, "image")  # duplicate destination
// after
g.add_edge(a, "image", denoise, "image")
g.delete_edge(a, "image", denoise, "image")
g.add_edge(b, "image", denoise, "image")

def has_input_edge(graph, node_id: str, field: str) -> bool:
    return any(
        e.destination.node_id == node_id and e.destination.field == field
        for e in graph.edges
    )

if not has_input_edge(g, dst_id, field):
    g.add_edge(src_id, src_field, dst_id, field)

def destination_is_free(graph, edge) -> bool:
    return not any(
        e.destination.node_id == edge.destination.node_id
        and e.destination.field == edge.destination.field
        for e in graph.edges
    )

from invokeai.app.services.shared.graph import InvalidEdgeError

try:
    g.add_edge(src, "image", dst, "image")
except InvalidEdgeError as e:
    if "already exists" in str(e):
        g.delete_edge(src, "image", dst, "image")
        g.add_edge(src, "image", dst, "image")  # replace

When it happens

Trigger: Calling g.add_edge() connecting a second edge into the same (node_id, field) destination that is not a CollectInvocation item field.

Common situations: Re-running graph-building scripts that add edges twice, wiring two outputs into a single non-collect input, UI/script mix-ups after editing an existing workflow.

Related errors

• Edge source and target types do not match ({edge})
• One or both nodes don't exist ({edge})
• Edge creates a cycle in the graph ({edge})
• Field types are incompatible ({edge})
• The selected saved workflow must contain exactly one workflo

AI-assisted analysis of invoke-ai/InvokeAI@0b6a024f2f (2026-08-29). Data as JSON: /api/errors/132ae43f16fe9d4b. Report an issue: GitHub.