Avoid inlining redundant responsive images

test/asset-inliner.test.mjs

@@ -103,6 +103,29 @@ test("removes image preload srcsets when the link has no href", async () => {
   assert.deepEqual(findExternalAssetRefs(output), []);
 });
 
+test("drops responsive image candidates after snapshot src is available", async () => {
+  const fetched = [];
+  const inliner = new AssetInliner();
+  inliner.fetchAsset = async (rawUrl) => {
+    fetched.push(rawUrl);
+    return {
+      bytes: Buffer.from("asset"),
+      contentType: "image/jpeg"
+    };
+  };
+
+  const output = await inliner.inlineHtml(`
+    <picture>
+      <source srcset="/small.webp 640w, /large.webp 1280w" type="image/webp">
+      <img src="/selected.jpg" srcset="/small.jpg 640w, /large.jpg 1280w">
+    </picture>
+  `, "https://example.com/article");
+
+  assert.deepEqual(fetched, ["https://example.com/selected.jpg"]);
+  assert.doesNotMatch(output, /srcset=/);
+  assert.deepEqual(findExternalAssetRefs(output), []);
+});
+
 test("asset inliner skips URLs blocked by the filter hook", async () => {
   const blocked = [];
   const inliner = new AssetInliner({