diff --git a/.changeset/tasty-steaks-know.md b/.changeset/tasty-steaks-know.md
new file mode 100644
index 00000000..35abdf1f
--- /dev/null
+++ b/.changeset/tasty-steaks-know.md
@@ -0,0 +1,5 @@
+---
+'quickmock': patch
+---
+
+Fix editor failing to load files opened from outside the workspace. The webview HTML was assigned before registering `onDidReceiveMessage`, causing a race where the initial `READY` / `WEBVIEW_READY` message from the app could be lost and the file content never delivered. The listener is now registered before the HTML assignment.
diff --git a/packages/vscode-extension/src/editor/provider.ts b/packages/vscode-extension/src/editor/provider.ts
index 64d018db..395936f7 100644
--- a/packages/vscode-extension/src/editor/provider.ts
+++ b/packages/vscode-extension/src/editor/provider.ts
@@ -109,11 +109,6 @@ export class QuickMockEditorProvider implements vscode.CustomEditorProvider<Quic
       enableScripts: true,
       localResourceRoots: [this.extensionUri],
     };
-    panel.webview.html = getHtml(
-      panel.webview,
-      this.extensionUri,
-      getEditorAppUrl()
-    );
 
     panel.webview.onDidReceiveMessage(async (msg: AppMessage) => {
       await handleWebviewMessage(msg, doc, reply =>
@@ -121,6 +116,12 @@ export class QuickMockEditorProvider implements vscode.CustomEditorProvider<Quic
       );
       documentRegistry.set(doc.uri.fsPath, doc.content);
     });
+
+    panel.webview.html = getHtml(
+      panel.webview,
+      this.extensionUri,
+      getEditorAppUrl()
+    );
   }
 
   private broadcast(doc: QuickMockDocument, msg: HostMessage): void {