diff --git a/js/workflow-metadata.js b/js/workflow-metadata.js
new file mode 100644
index 00000000..d3b07d84
--- /dev/null
+++ b/js/workflow-metadata.js
@@ -0,0 +1,72 @@
+/**
+ * Attaches metadata to the workflow on save
+ * - custom node pack version to all custom nodes used in the workflow
+ */
+
+import { app } from "../../scripts/app.js";
+import { api } from "../../scripts/api.js";
+
+class WorkflowMetadataExtension {
+  constructor() {
+    this.name = "Comfy.CustomNodesManager.WorkflowMetadata";
+    this.installedNodeVersions = {};
+    this.comfyCoreVersion = null;
+  }
+
+  /**
+   * Get the installed node versions
+   * @returns {Promise<Record<string, string>>} The mapping from node name to version
+   * version can either be a git commit hash or a semantic version such as "1.0.0"
+   */
+  async getInstalledNodeVersions() {
+    const res = await api.fetchApi("/customnode/installed");
+    return await res.json();
+  }
+
+  /**
+   * Get the node versions for the given graph
+   * @param {LGraph} graph The graph to get the node versions for
+   * @returns {Promise<Record<string, string>>} The mapping from node name to version
+   */
+  getGraphNodeVersions(graph) {
+    const nodeVersions = {};
+    for (const node of graph.nodes) {
+      const nodeData = node.constructor.nodeData;
+      const modules = nodeData.python_module.split(".");
+
+      if (modules[0] === "custom_nodes") {
+        const nodePackageName = modules[1].split("@")[0];
+        const nodeVersion = this.installedNodeVersions[nodePackageName];
+        nodeVersions[nodePackageName] = nodeVersion;
+      } else if (["nodes", "comfy_extras"].includes(modules[0])) {
+        nodeVersions["comfy-core"] = this.comfyCoreVersion;
+      } else {
+        console.warn(`Unknown node source: ${nodeData.python_module}`);
+      }
+    }
+    return nodeVersions;
+  }
+
+  async init() {
+    const extension = this;
+    this.installedNodeVersions = await this.getInstalledNodeVersions();
+    this.comfyCoreVersion = (await api.getSystemStats()).system.comfyui_version;
+
+    // Attach metadata when app.graphToPrompt is called.
+    const originalSerialize = LGraph.prototype.serialize;
+    LGraph.prototype.serialize = function () {
+      const workflow = originalSerialize.apply(this, arguments);
+
+      // Add metadata to the workflow
+      if (!workflow.extra) {
+        workflow.extra = {};
+      }
+      const graph = this;
+      workflow.extra["node_versions"] = extension.getGraphNodeVersions(graph);
+
+      return workflow;
+    };
+  }
+}
+
+app.registerExtension(new WorkflowMetadataExtension());