fix(builder): auto-cleanup invalid/orphan edges during graph operations

Fixes graph desync issues where edge deletions don't persist, causing
stale connections that users cannot remove.

Frontend changes:
- edgeStore: Validate links during addLinks() - skip edges referencing
  non-existent nodes
- edgeStore: Filter invalid edges in getBackendLinks() before save
- useSaveGraph: Sync edge store with authoritative backend state after
  save to prevent desync

Backend changes:
- graph.py: Add prune_invalid_links() method that removes:
  - Links referencing non-existent nodes
  - Links with invalid block IDs
- Called during graph validation to auto-cleanup orphan edges

This ensures:
1. Invalid edges are filtered out when loading a graph
2. Invalid edges are not sent to backend during save
3. Frontend syncs with backend state after save
4. Backend cleans up any orphan edges that slip through

Closes: SECRT-1959

autogpt_platform/backend/backend/data/graph.py

@@ -867,9 +867,66 @@ class GraphModel(Graph, GraphMeta):
 
         return node_errors
 
+    @staticmethod
+    def prune_invalid_links(graph: BaseGraph) -> int:
+        """
+        Remove invalid/orphan links from the graph.
+
+        This removes links that:
+        - Reference non-existent source or sink nodes
+        - Reference invalid block IDs
+        - Reference invalid pin names
+
+        Returns the number of links pruned.
+        """
+        node_map = {v.id: v for v in graph.nodes}
+        original_count = len(graph.links)
+        valid_links = []
+
+        for link in graph.links:
+            source_node = node_map.get(link.source_id)
+            sink_node = node_map.get(link.sink_id)
+
+            # Skip if either node doesn't exist
+            if not source_node or not sink_node:
+                logger.warning(
+                    f"Pruning orphan link: source={link.source_id}, sink={link.sink_id} "
+                    f"- node(s) not found"
+                )
+                continue
+
+            # Skip if source block doesn't exist
+            source_block = get_block(source_node.block_id)
+            if not source_block:
+                logger.warning(
+                    f"Pruning link with invalid source block: {source_node.block_id}"
+                )
+                continue
+
+            # Skip if sink block doesn't exist
+            sink_block = get_block(sink_node.block_id)
+            if not sink_block:
+                logger.warning(
+                    f"Pruning link with invalid sink block: {sink_node.block_id}"
+                )
+                continue
+
+            valid_links.append(link)
+
+        graph.links = valid_links
+        pruned_count = original_count - len(valid_links)
+
+        if pruned_count > 0:
+            logger.info(f"Pruned {pruned_count} invalid link(s) from graph {graph.id}")
+
+        return pruned_count
+
     @staticmethod
     def _validate_graph_structure(graph: BaseGraph):
         """Validate graph structure (links, connections, etc.)"""
+        # First, prune invalid links to clean up orphan edges
+        GraphModel.prune_invalid_links(graph)
+
         node_map = {v.id: v for v in graph.nodes}
 
         def is_static_output_block(nid: str) -> bool:

autogpt_platform/frontend/src/app/(platform)/build/hooks/useSaveGraph.ts

@@ -13,6 +13,7 @@ import { Graph } from "@/app/api/__generated__/models/graph";
 import { useNodeStore } from "../stores/nodeStore";
 import { useEdgeStore } from "../stores/edgeStore";
 import { graphsEquivalent } from "../components/NewControlPanel/NewSaveControl/helpers";
+import { linkToCustomEdge } from "../components/helper";
 import { useGraphStore } from "../stores/graphStore";
 import { useShallow } from "zustand/react/shallow";
 import {
@@ -21,6 +22,18 @@ import {
   getTempFlowId,
 } from "@/services/builder-draft/draft-service";
 
+/**
+ * Sync the edge store with the authoritative backend state.
+ * This ensures the frontend matches what the backend accepted after save.
+ */
+function syncEdgesWithBackend(links: GraphModel["links"]) {
+  if (links !== undefined) {
+    // Replace all edges with the authoritative backend state
+    const newEdges = links.map(linkToCustomEdge);
+    useEdgeStore.getState().setEdges(newEdges);
+  }
+}
+
 export type SaveGraphOptions = {
   showToast?: boolean;
   onSuccess?: (graph: GraphModel) => void;
@@ -64,6 +77,9 @@ export const useSaveGraph = ({
             flowVersion: data.version,
           });
 
+          // Sync edge store with authoritative backend state
+          syncEdgesWithBackend(data.links);
+
           const tempFlowId = getTempFlowId();
           if (tempFlowId) {
             await draftService.deleteDraft(tempFlowId);
@@ -101,6 +117,9 @@ export const useSaveGraph = ({
             flowVersion: data.version,
           });
 
+          // Sync edge store with authoritative backend state
+          syncEdgesWithBackend(data.links);
+
           // Clear the draft for this flow after successful save
           if (data.id) {
             await draftService.deleteDraft(data.id);

autogpt_platform/frontend/src/app/(platform)/build/stores/edgeStore.ts

@@ -120,10 +120,33 @@ export const useEdgeStore = create<EdgeStore>((set, get) => ({
   isOutputConnected: (nodeId, handle) =>
     get().edges.some((e) => e.source === nodeId && e.sourceHandle === handle),
 
-  getBackendLinks: () => get().edges.map(customEdgeToLink),
+  getBackendLinks: () => {
+    // Filter out edges referencing non-existent nodes before converting to links
+    const nodeIds = new Set(useNodeStore.getState().nodes.map((n) => n.id));
+    const validEdges = get().edges.filter((edge) => {
+      const isValid = nodeIds.has(edge.source) && nodeIds.has(edge.target);
+      if (!isValid) {
+        console.warn(
+          `[EdgeStore] Filtering out invalid edge during save: source=${edge.source}, target=${edge.target}`,
+        );
+      }
+      return isValid;
+    });
+    return validEdges.map(customEdgeToLink);
+  },
 
   addLinks: (links) => {
+    // Get current node IDs to validate links
+    const nodeIds = new Set(useNodeStore.getState().nodes.map((n) => n.id));
+
     links.forEach((link) => {
+      // Skip invalid links (orphan edges referencing non-existent nodes)
+      if (!nodeIds.has(link.source_id) || !nodeIds.has(link.sink_id)) {
+        console.warn(
+          `[EdgeStore] Skipping invalid link: source=${link.source_id}, sink=${link.sink_id} - node(s) not found`,
+        );
+        return;
+      }
       get().addEdge(linkToCustomEdge(link));
     });
   },