diff --git a/.github/workflows/docker-riverproui.yaml b/.github/workflows/docker-riverproui.yaml
index 84f7fe34..778cb349 100644
--- a/.github/workflows/docker-riverproui.yaml
+++ b/.github/workflows/docker-riverproui.yaml
@@ -468,6 +468,15 @@ jobs:
           echo "amd64_digest=$AMD64_DIGEST" >> $GITHUB_OUTPUT
           echo "arm64_digest=$ARM64_DIGEST" >> $GITHUB_OUTPUT
 
+      - name: Prefetch buildx attestation manifests referenced by index (legacy non-referrers)
+        env:
+          AUTH_USER: river
+          AUTH_PASSWORD: ${{ secrets.RIVERPRO_GO_MOD_CREDENTIAL }}
+          FORCE_FETCH_SECRET: ${{ secrets.FORCE_FETCH_SECRET }}
+          REGISTRY_MANIFEST_URL: https://riverqueue.com/v2/riverproui/manifests
+        run: |
+          bash scripts/prefetch-buildx-attestation-manifests.sh /tmp/index-manifest-docker.json
+
       - name: Fetch amd64 manifest with crane (Docker media type)
         run: crane manifest "$IMAGE_NAME@${{ steps.platform-digests.outputs.amd64_digest }}" > /tmp/amd64-manifest-docker.json
 
diff --git a/scripts/prefetch-buildx-attestation-manifests.sh b/scripts/prefetch-buildx-attestation-manifests.sh
new file mode 100644
index 00000000..94c3de78
--- /dev/null
+++ b/scripts/prefetch-buildx-attestation-manifests.sh
@@ -0,0 +1,87 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Prefetch buildx "attestation-manifest" descriptors referenced directly in an OCI image index.
+#
+# Why: buildx can embed attestation manifests in the index's `manifests[]` with
+# `annotations["vnd.docker.reference.type"]="attestation-manifest"`. Some clients try to pull them.
+# In a pull-through-cache setup (ECR -> Worker -> R2), you must request these while the upstream
+# still has them or they can later 404 from the R2-backed registry.
+#
+# Inputs:
+#   - Arg1: path to an index JSON file (e.g. from `crane manifest ... > /tmp/index.json`)
+#
+# Environment variables:
+#   - IMAGE_NAME (required): e.g. "riverqueue.com/riverproui"
+#   - REGISTRY_MANIFEST_URL (required): full manifest base URL, e.g. "https://riverqueue.com/v2/riverproui/manifests"
+#   - AUTH_USER (required): basic auth username
+#   - AUTH_PASSWORD (required): basic auth password
+#   - FORCE_FETCH_SECRET (optional): if set, sent as X-Force-Fetch-From-Upstream to force pull-through from upstream
+
+INDEX_JSON_PATH="${1:-}"
+if [[ -z "$INDEX_JSON_PATH" ]]; then
+  echo "usage: $0 <index-json-path>" >&2
+  exit 2
+fi
+
+: "${IMAGE_NAME:?IMAGE_NAME is required (e.g. riverqueue.com/riverproui)}"
+: "${REGISTRY_MANIFEST_URL:?REGISTRY_MANIFEST_URL is required (e.g. https://riverqueue.com/v2/riverproui/manifests)}"
+: "${AUTH_USER:?AUTH_USER is required}"
+: "${AUTH_PASSWORD:?AUTH_PASSWORD is required}"
+
+tmp_digests="$(mktemp)"
+jq -r '
+  .manifests[]?
+  | select((.annotations["vnd.docker.reference.type"] // "") == "attestation-manifest")
+  | .digest
+' "$INDEX_JSON_PATH" | sort -u > "$tmp_digests"
+
+if [[ ! -s "$tmp_digests" ]]; then
+  echo "No buildx attestation-manifest descriptors found in index."
+  exit 0
+fi
+
+echo "Prefetching buildx attestation manifests referenced by index:"
+cat "$tmp_digests"
+
+while read -r digest; do
+  [[ -z "$digest" ]] && continue
+
+  echo "Prefetching attestation manifest: $digest"
+
+  # Ensure the pull-through cache fetches the manifest bytes from upstream and stores them.
+  # Note: ORAS cannot send our custom force-refresh header, so we use curl for that part.
+  curl_args=(
+    -f
+    -u "${AUTH_USER}:${AUTH_PASSWORD}"
+    -H "Accept: application/vnd.oci.image.manifest.v1+json"
+    "${REGISTRY_MANIFEST_URL}/${digest}"
+    -o /dev/null
+  )
+  if [[ -n "${FORCE_FETCH_SECRET:-}" ]]; then
+    curl_args=(
+      -f
+      -u "${AUTH_USER}:${AUTH_PASSWORD}"
+      -H "X-Force-Fetch-From-Upstream: ${FORCE_FETCH_SECRET}"
+      -H "Accept: application/vnd.oci.image.manifest.v1+json"
+      "${REGISTRY_MANIFEST_URL}/${digest}"
+      -o /dev/null
+    )
+  fi
+  curl "${curl_args[@]}"
+
+  # Warm referenced blobs so subsequent clients don't have to traverse to upstream.
+  mf="$(mktemp)"
+  oras manifest fetch --output "$mf" "${IMAGE_NAME}@${digest}"
+
+  cfg="$(jq -r '.config.digest // empty' "$mf")"
+  if [[ -n "$cfg" ]]; then
+    oras blob fetch --output /dev/null "${IMAGE_NAME}@${cfg}"
+  fi
+
+  jq -r '.layers[]?.digest // empty' "$mf" | while read -r layer_digest; do
+    [[ -n "$layer_digest" ]] && oras blob fetch --output /dev/null "${IMAGE_NAME}@${layer_digest}"
+  done
+done < "$tmp_digests"
+
+