@@ -603,6 +603,18 @@ describe("T7 — data-hf-id targeting (spec for R1)", () => {
     expect(html).toMatch(/color:\s*blue/);
   });
 
+  it("never falls back by id onto an element pinned to another hfId", () => {
+    // A clip in a sub-composition shares the audio group's id; its edit must not land on the group.
+    const source = `<div data-composition-id="main"><hf-audio-group id="voice" data-hf-id="hf-oova" data-fx-chain="[]"></hf-audio-group><div class="clip" data-start="0"></div></div>`;
+    const target = { id: "voice", hfId: "hf-6egx" };
+    expect(removeElementFromHtml(source, target)).toBe(source);
+    const { html, matched } = patchElementInHtml(source, target, [
+      { type: "attribute", property: "data-start", value: "3" },
+    ]);
+    expect(matched).toBe(false);
+    expect(html).toBe(source);
+  });
+
   it("does not break out of the selector on a crafted hfId (CSS injection guard)", () => {
     // A value with a quote/bracket must be escaped, not injected — it should
     // simply match nothing and leave the source untouched, never throw.
 
@@ -23,19 +23,22 @@ export interface SourceMutationTarget {
   selectorIndex?: number;
 }
 
+const pinnedInSource = new WeakMap<Document, ReadonlySet<string>>();
+
 export function parseSourceDocument(raw: string): {
   document: Document;
   wrappedFragment: boolean;
 } {
   const source = ensureHfIds(raw);
   const hasDocumentShell = /<!doctype|<html[\s>]/i.test(source);
-  if (hasDocumentShell) {
-    return { document: parseHTML(source).document, wrappedFragment: false };
-  }
-  return {
-    document: parseHTML(`<!DOCTYPE html><html><head></head><body>${source}</body></html>`).document,
-    wrappedFragment: true,
-  };
+  const document = hasDocumentShell
+    ? parseHTML(source).document
+    : parseHTML(`<!DOCTYPE html><html><head></head><body>${source}</body></html>`).document;
+  pinnedInSource.set(
+    document,
+    new Set(Array.from(raw.matchAll(/\bdata-hf-id\s*=\s*["']?([^"'\s>]+)/gi), (m) => m[1]!)),
+  );
+  return { document, wrappedFragment: !hasDocumentShell };
 }
 
 function duplicateCssRulesForId(document: Document, originalId: string, newId: string): void {
@@ -123,16 +126,19 @@ export function findTargetElement(
     const el = findByHfId(document, target.hfId);
     if (el) return el;
   }
+  const pinned = pinnedInSource.get(document);
+  const unlessPinnedElsewhere = (el: Element | null | undefined) =>
+    el && !(target.hfId && pinned?.has(el.getAttribute("data-hf-id") ?? "")) ? el : null;
 
   if (target.id) {
-    const byId = document.getElementById(target.id);
+    const byId = unlessPinnedElsewhere(document.getElementById(target.id));
     if (byId) return byId;
   }
 
   if (!target.selector) return null;
   try {
     const matches = querySelectorAllWithTemplates(document, target.selector);
-    return matches[target.selectorIndex ?? 0] ?? null;
+    return unlessPinnedElsewhere(matches[target.selectorIndex ?? 0]);
   } catch {
     return null;
   }