diff --git a/backend/app/services/cleanup_service.py b/backend/app/services/cleanup_service.py
index 9979907..250b315 100644
--- a/backend/app/services/cleanup_service.py
+++ b/backend/app/services/cleanup_service.py
@@ -573,6 +573,29 @@ def _repoint_post_links(session: Session, loser_id: int, keeper_id: int) -> None
     dup_imgs = select(ImageProvenance.image_record_id).where(
         ImageProvenance.post_id == keeper_id
     )
+    # Before dropping the colliding loser rows, carry their from_attachment_id
+    # (which archive the file came out of, milestone #87) onto the keeper's
+    # surviving row when the keeper didn't record one. For the gallery-dl→native
+    # case this very milestone targets, the keeper is the native stub (no
+    # archive) and the loser is the gallery-dl row that extracted the member, so
+    # a blind delete would silently lose the containing-archive linkage.
+    for img_id, att_id in session.execute(
+        select(ImageProvenance.image_record_id, ImageProvenance.from_attachment_id)
+        .where(
+            ImageProvenance.post_id == loser_id,
+            ImageProvenance.image_record_id.in_(dup_imgs),
+            ImageProvenance.from_attachment_id.is_not(None),
+        )
+    ).all():
+        session.execute(
+            update(ImageProvenance)
+            .where(
+                ImageProvenance.post_id == keeper_id,
+                ImageProvenance.image_record_id == img_id,
+                ImageProvenance.from_attachment_id.is_(None),
+            )
+            .values(from_attachment_id=att_id)
+        )
     session.execute(
         delete(ImageProvenance).where(
             ImageProvenance.post_id == loser_id,
diff --git a/tests/test_cleanup_service.py b/tests/test_cleanup_service.py
index f5419d7..af56753 100644
--- a/tests/test_cleanup_service.py
+++ b/tests/test_cleanup_service.py
@@ -853,3 +853,36 @@ def test_reconcile_dedups_provenance_collision(db_sync, tmp_path):
         select(ImageProvenance.post_id).where(ImageProvenance.image_record_id == img_id)
     ).scalars().all()
     assert prov == [native_id]
+
+
+def test_reconcile_preserves_from_attachment_on_provenance_collision(db_sync, tmp_path):
+    # The gallery-dl loser row recorded which archive the image came out of
+    # (#87); the native keeper row didn't. Merging drops the loser provenance row
+    # on the (image, post) collision — but must first carry its from_attachment_id
+    # onto the keeper so the containing-archive linkage survives.
+    a = _make_artist(db_sync, slug="rc4")
+    img = _make_image(db_sync, artist=a, path=str(tmp_path / "z.jpg"), sha256="e" * 64)
+    legacy = Post(artist_id=a.id, external_post_id="9", raw_metadata={"post_id": 77})
+    native = Post(artist_id=a.id, external_post_id="77", raw_metadata={"post_id": 77})
+    db_sync.add_all([legacy, native])
+    db_sync.flush()
+    att = PostAttachment(
+        post_id=legacy.id, artist_id=a.id, sha256="f" * 64,
+        path=str(tmp_path / "bundle.cbz"), original_filename="bundle.cbz",
+        ext=".cbz", size_bytes=9,
+    )
+    db_sync.add(att)
+    db_sync.flush()
+    db_sync.add(ImageProvenance(
+        image_record_id=img.id, post_id=legacy.id, from_attachment_id=att.id,
+    ))
+    db_sync.add(ImageProvenance(image_record_id=img.id, post_id=native.id))
+    img_id, native_id, att_id = img.id, native.id, att.id
+    db_sync.commit()
+
+    cleanup_service.reconcile_duplicate_posts(db_sync, dry_run=False)
+    rows = db_sync.execute(
+        select(ImageProvenance.post_id, ImageProvenance.from_attachment_id)
+        .where(ImageProvenance.image_record_id == img_id)
+    ).all()
+    assert rows == [(native_id, att_id)]