diff --git a/apps/app/vite.dev.config.ts b/apps/app/vite.dev.config.ts
index 2d4743c12..0de0a718c 100644
--- a/apps/app/vite.dev.config.ts
+++ b/apps/app/vite.dev.config.ts
@@ -1,4 +1,32 @@
-import { defineConfig } from "vite";
+import { defineConfig, type Plugin } from "vite";
+import { readFileSync } from "node:fs";
+
+// QA instrumentation for issue #1676: delay proxied API requests whose URL
+// contains `match` by `ms` when /tmp/bb-reports/issues/1676/repro/delay.json
+// exists ({"match":"...","ms":4000}). Re-read on every request so it can be
+// toggled without restarting Vite.
+function qaDelayPlugin(): Plugin {
+  return {
+    name: "qa-delay-1676",
+    configureServer(server) {
+      server.middlewares.use((req, _res, next) => {
+        let spec: { match?: string; ms?: number } | null = null;
+        try {
+          spec = JSON.parse(
+            readFileSync("/tmp/bb-reports/issues/1676/repro/delay.json", "utf8"),
+          );
+        } catch {
+          spec = null;
+        }
+        if (spec?.match && spec.ms && (req.url ?? "").includes(spec.match)) {
+          setTimeout(next, spec.ms);
+          return;
+        }
+        next();
+      });
+    },
+  };
+}
 import { loadViteDevConfig } from "@bb/config/vite-dev";
 import { sharedViteConfig } from "./vite.config.js";
 
@@ -9,6 +37,7 @@ const devWebSocketBrowserHostPortDefine = JSON.stringify(
 
 export default defineConfig({
   ...sharedViteConfig,
+  plugins: [...(sharedViteConfig.plugins ?? []), qaDelayPlugin()],
   // Match the production CSS pipeline in dev. In particular, this lowers
   // Tailwind's nested conditional rules for Safari versions that parse
   // color-mix() but do not reliably apply nested @supports declarations.