fix: keep auto-layout hydration clean

src/components/flows/flow-editor-state.test.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect } from "vitest";
 import {
+  applyNodePositions,
   defaultConfigFor,
   uniqueNodeKey,
 } from "./flow-editor-state";
@@ -33,6 +34,48 @@ describe("uniqueNodeKey", () => {
   });
 });
 
+describe("applyNodePositions", () => {
+  it("rounds and applies positions without changing unrelated nodes", () => {
+    const nodes: BuilderNode[] = [
+      {
+        node_key: "start",
+        node_type: "start",
+        config: {},
+        position_x: 0,
+        position_y: 0,
+      },
+      {
+        node_key: "message",
+        node_type: "send_message",
+        config: {},
+        position_x: 10,
+        position_y: 20,
+      },
+    ];
+
+    expect(
+      applyNodePositions(nodes, {
+        start: { x: 10.4, y: 20.6 },
+      }),
+    ).toEqual([
+      {
+        node_key: "start",
+        node_type: "start",
+        config: {},
+        position_x: 10,
+        position_y: 21,
+      },
+      {
+        node_key: "message",
+        node_type: "send_message",
+        config: {},
+        position_x: 10,
+        position_y: 20,
+      },
+    ]);
+  });
+});
+
 describe("defaultConfigFor", () => {
   // The hook's addNode and the validator both depend on these defaults
   // being self-consistent. A broken default would surface as a

src/components/flows/flow-editor-state.tsx

@@ -189,6 +189,22 @@ export function defaultConfigFor(type: NodeType): Record<string, unknown> {
   }
 }
 
+export function applyNodePositions(
+  nodes: BuilderNode[],
+  positions: Record<string, { x: number; y: number }>,
+): BuilderNode[] {
+  return nodes.map((n) => {
+    const next = positions[n.node_key];
+    return next
+      ? {
+          ...n,
+          position_x: Math.round(next.x),
+          position_y: Math.round(next.y),
+        }
+      : n;
+  });
+}
+
 // ============================================================
 // Context
 // ============================================================
@@ -443,21 +459,15 @@ export function FlowEditorProvider({
 
   const updateNodePositions = useCallback(
     (positions: Record<string, { x: number; y: number }>) => {
-      setState((s) => ({
+      // Initial Dagre layout hydration should not dirty the editor:
+      // opening a legacy all-zero flow must not enable Save or arm
+      // beforeunload before the user actually edits anything.
+      setStateRaw((s) => ({
         ...s,
-        nodes: s.nodes.map((n) => {
-          const next = positions[n.node_key];
-          return next
-            ? {
-                ...n,
-                position_x: Math.round(next.x),
-                position_y: Math.round(next.y),
-              }
-            : n;
-        }),
+        nodes: applyNodePositions(s.nodes, positions),
       }));
     },
-    [setState],
+    [],
   );
 
   const addNode = useCallback(