diff --git a/README.md b/README.md
index 803475f..8a732f0 100644
--- a/README.md
+++ b/README.md
@@ -45,8 +45,13 @@ slot-holds) are complete. See §6 of `IMPLEMENTATION_PLAN.md` for the phased
 build order and acceptance criteria — next up is Phase 5 (multi-location,
 zones, rates, auto-assignment).
 
-Editing the storefront widget's `extensions/datetime-widget/src/`? Run
-`npm run build:widget` to rebuild `assets/datetime-widget.js` — it also runs
+The storefront widget's TypeScript source lives in `widget-src/datetime-widget/`,
+**not** inside `extensions/datetime-widget/` — a Theme App Extension's
+directory may only contain `assets`, `blocks`, `snippets`, and `locales`
+(the CLI hard-rejects anything else, e.g. a `src/` folder, with "Only
+assets, blocks, snippets, locales directories are allowed"). Editing the
+widget? Run `npm run build:widget` to bundle it into
+`extensions/datetime-widget/assets/datetime-widget.js` — it also runs
 automatically before `npm run dev` / `npm run deploy`.
 
 **Functions are JavaScript, not Rust** (`extensions/validation-slot/`,
diff --git a/extensions/datetime-widget/blocks/app-embed.liquid b/extensions/datetime-widget/blocks/app-embed.liquid
index fc54cdf..4e08188 100644
--- a/extensions/datetime-widget/blocks/app-embed.liquid
+++ b/extensions/datetime-widget/blocks/app-embed.liquid
@@ -1,5 +1,5 @@
 {{ 'datetime-widget.css' | asset_url | stylesheet_tag }}
-{{ 'datetime-widget.js' | asset_url | script_tag }}
+<script src="{{ 'datetime-widget.js' | asset_url }}" defer="defer"></script>
 
 {% schema %}
 {
diff --git a/package.json b/package.json
index 4dda378..5135e82 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,7 @@
     "test": "vitest",
     "test:integration": "vitest run --config vitest.integration.config.ts",
     "test:e2e": "playwright test",
-    "build:widget": "esbuild extensions/datetime-widget/src/datetime-widget.ts --bundle --minify --target=es2019 --outfile=extensions/datetime-widget/assets/datetime-widget.js",
+    "build:widget": "esbuild widget-src/datetime-widget/datetime-widget.ts --bundle --minify --target=es2019 --outfile=extensions/datetime-widget/assets/datetime-widget.js",
     "worker": "tsx jobs/worker.ts",
     "shopify": "shopify",
     "prisma": "prisma",
diff --git a/extensions/datetime-widget/src/datetime-widget.ts b/widget-src/datetime-widget/datetime-widget.ts
similarity index 100%
rename from extensions/datetime-widget/src/datetime-widget.ts
rename to widget-src/datetime-widget/datetime-widget.ts