diff --git a/.gitea/ci/update_thirdparty_skills.sh b/.gitea/ci/update_thirdparty_skills.sh
index b207e6d..d51de57 100644
--- a/.gitea/ci/update_thirdparty_skills.sh
+++ b/.gitea/ci/update_thirdparty_skills.sh
@@ -99,15 +99,30 @@ cd "$REPO_DIR"
 git config user.name "$COMMIT_AUTHOR_NAME"
 git config user.email "$COMMIT_AUTHOR_EMAIL"
 
-git fetch origin "$TARGET_BRANCH"
-git checkout -B "$TARGET_BRANCH" "origin/$TARGET_BRANCH"
-
 tmp_dir="$(mktemp -d)"
 cleanup() {
   rm -rf "$tmp_dir"
 }
 trap cleanup EXIT
 
+if [ ! -f "$MANIFEST_PATH" ]; then
+  echo "ERROR: third-party manifest not found: $MANIFEST_PATH" >&2
+  exit 1
+fi
+
+manifest_copy="$tmp_dir/thirdparty_skills.json"
+cp "$MANIFEST_PATH" "$manifest_copy"
+MANIFEST_PATH="$manifest_copy"
+
+git fetch origin "$TARGET_BRANCH"
+git checkout -B "$TARGET_BRANCH" "origin/$TARGET_BRANCH"
+
+sources_file="$tmp_dir/sources.tsv"
+if ! emit_sources_tsv > "$sources_file"; then
+  echo "ERROR: failed to load third-party manifest: $MANIFEST_PATH" >&2
+  exit 1
+fi
+
 changed=0
 while IFS=$'\t' read -r source_id upstream_repo upstream_ref snapshot_dir sync_mode; do
   [ -n "$source_id" ] || continue
@@ -167,7 +182,7 @@ EOF
 
   git add -A "$snapshot_dir"
   changed=1
-done < <(emit_sources_tsv)
+done < "$sources_file"
 
 if [ "$changed" -eq 0 ] || git diff --cached --quiet; then
   echo "All third-party snapshots are up to date."
diff --git a/tests/test_thirdparty_skills_pipeline.py b/tests/test_thirdparty_skills_pipeline.py
index fc42f8d..50f4738 100644
--- a/tests/test_thirdparty_skills_pipeline.py
+++ b/tests/test_thirdparty_skills_pipeline.py
@@ -80,6 +80,18 @@ class ThirdpartySkillsPipelineTests(unittest.TestCase):
         self.assertTrue((UI_UX_PRO_MAX_DIR / "data").is_dir())
         self.assertTrue((UI_UX_PRO_MAX_DIR / "scripts").is_dir())
 
+    def test_update_script_materializes_manifest_before_target_checkout(self):
+        text = UPDATE_SCRIPT.read_text(encoding="utf-8")
+        self.assertIn('manifest_copy="$tmp_dir/thirdparty_skills.json"', text)
+        self.assertIn('cp "$MANIFEST_PATH" "$manifest_copy"', text)
+        self.assertIn('MANIFEST_PATH="$manifest_copy"', text)
+        self.assertIn('if ! emit_sources_tsv > "$sources_file"; then', text)
+        self.assertNotIn("done < <(emit_sources_tsv)", text)
+        self.assertLess(
+            text.index('cp "$MANIFEST_PATH" "$manifest_copy"'),
+            text.index('git checkout -B "$TARGET_BRANCH" "origin/$TARGET_BRANCH"'),
+        )
+
 
 if __name__ == "__main__":
     unittest.main()