fix(core): clear data-hf-id on split clone to prevent dual-match (R7 review)

vanceingalls · claude · vanceingalls · commit 5c0cf9b29391 · 2026-06-09T14:20:39.000-07:00
cloneNode(true) copies all attributes including data-hf-id. Without clearing it,
both halves of a split share the same hf-id; the server's findByHfId picks the first
match and silently patches the wrong clip. Remove the attribute from the clone so
write-back re-mints a fresh id on the next preview load.

Adds a test: splitElementInHtml — hfId clone isolation.

Co-Authored-By: Claude Sonnet 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/packages/core/src/studio-api/helpers/sourceMutation.test.ts b/packages/core/src/studio-api/helpers/sourceMutation.test.ts
@@ -3,6 +3,7 @@ import {
   removeElementFromHtml,
   patchElementInHtml,
   probeElementInSource,
+  splitElementInHtml,
 } from "./sourceMutation.js";
 
 describe("removeElementFromHtml", () => {
@@ -455,3 +456,14 @@ describe("T7 — data-hf-id targeting (spec for R1)", () => {
     expect(html).toContain('data-hf-id="hf-a1b2"');
   });
 });
+
+describe("splitElementInHtml — hfId clone isolation", () => {
+  it("does not copy data-hf-id to the cloned second half", () => {
+    const source = `<html><body><div data-composition-id="root"><div id="clip1" class="clip" data-start="0" data-duration="10" data-hf-id="hf-abc123"></div></div></body></html>`;
+    const { html, matched } = splitElementInHtml(source, { id: "clip1" }, 5, "clip2");
+
+    expect(matched).toBe(true);
+    const occurrences = (html.match(/data-hf-id="hf-abc123"/g) ?? []).length;
+    expect(occurrences).toBe(1);
+  });
+});
diff --git a/packages/core/src/studio-api/helpers/sourceMutation.ts b/packages/core/src/studio-api/helpers/sourceMutation.ts
@@ -275,6 +275,7 @@ export function splitElementInHtml(
 
   const clone = el.cloneNode(true) as HTMLElement;
   clone.setAttribute("id", newId);
+  clone.removeAttribute("data-hf-id");
   clone.setAttribute("data-start", String(Math.round(splitTime * 1000) / 1000));
   clone.setAttribute("data-duration", String(Math.round(secondDuration * 1000) / 1000));
 
