diff --git a/.gitea/scripts/publish-releases.js b/.gitea/scripts/publish-releases.js
index 3674de44bf..96b156ed36 100644
--- a/.gitea/scripts/publish-releases.js
+++ b/.gitea/scripts/publish-releases.js
@@ -36,10 +36,15 @@ const UPSTREAM = 'deepseek-ai/deepseek-harness';
 const UA = 'deepseek-harness-release-bot/1.0';
 
 const MANIFEST_ACCEPT = [
+  'application/vnd.oci.image.index.v1+json',
+  'application/vnd.docker.distribution.manifest.list.v2+json',
   'application/vnd.docker.distribution.manifest.v2+json',
   'application/vnd.oci.image.manifest.v1+json',
 ].join(',');
 
+/** Platform preferred when a tag is a multi-arch index (the deployment's arch). */
+const PREFERRED_ARCH = 'amd64';
+
 async function gitea(method, path, body) {
   const res = await fetch(`${GITEA}/api/v1${path}`, {
     method,
@@ -134,14 +139,29 @@ function caveats(ver) {
 async function imageFacts(tag) {
   const res = await registry(`manifests/${tag}`, MANIFEST_ACCEPT);
   if (!res.ok) throw new Error(`manifest ${tag}: HTTP ${res.status}`);
+  // The digest reported is the one `docker pull <tag>` pins — for a multi-arch
+  // tag that is the index, not any single platform's manifest.
   const digest = res.headers.get('docker-content-digest') || '';
-  const manifest = await res.json();
+  let manifest = await res.json();
+  // A multi-arch tag is an index: follow it to a platform manifest, because
+  // only that one carries the config blob the labels live in.
+  if (Array.isArray(manifest.manifests)) {
+    const entries = manifest.manifests.filter((m) => m.platform?.os === 'linux');
+    const chosen = entries.find((m) => m.platform?.architecture === PREFERRED_ARCH) ?? entries[0];
+    if (!chosen) throw new Error(`manifest ${tag}: index has no linux platform`);
+    const sub = await registry(`manifests/${chosen.digest}`, MANIFEST_ACCEPT);
+    if (!sub.ok) throw new Error(`manifest ${tag} -> ${chosen.digest}: HTTP ${sub.status}`);
+    manifest = await sub.json();
+  }
   const cfgDigest = manifest.config?.digest;
   let labels = {};
   if (cfgDigest) {
     const blob = await registry(`blobs/${cfgDigest}`, '*/*');
     if (blob.ok) labels = (await blob.json()).config?.Labels ?? {};
   }
+  if (!labels['dev.milesward.pnpm-version']) {
+    console.error(`::warning::${tag}: no provenance labels found on the image config`);
+  }
   return {
     digest,
     pnpm: labels['dev.milesward.pnpm-version'] || '',
diff --git a/.gitea/workflows/sync-upstream.yml b/.gitea/workflows/sync-upstream.yml
index 34b41688f9..bb539c3a12 100644
--- a/.gitea/workflows/sync-upstream.yml
+++ b/.gitea/workflows/sync-upstream.yml
@@ -87,13 +87,24 @@ jobs:
             [ "$(curl -s -o /dev/null -w '%{http_code}' -u "${{ github.repository_owner }}:${TOKEN}" \
               -H "Accept: $ACCEPT" "https://${REGISTRY}/v2/${IMAGE}/manifests/$1")" = 200 ]
           }
-          # Labels of a single-arch manifest's config blob ("pnpm|base|recipe");
-          # empty output (index manifests, missing labels) means "treat as stale".
+          # Provenance labels from a tag's image config ("pnpm|base|recipe").
+          # Empty output means "treat as stale". A multi-arch tag resolves to an
+          # index, whose first child manifest is followed to reach the config —
+          # without that, such a tag would look stale on every run and spam a
+          # new revision build every six hours.
+          fetch_manifest() {
+            curl -s -u "${{ github.repository_owner }}:${TOKEN}" -H "Accept: $ACCEPT" \
+              "https://${REGISTRY}/v2/${IMAGE}/manifests/$1"
+          }
+          first_digest() { printf '%s' "$1" | grep -o '"digest": *"sha256:[a-f0-9]*"' | head -1 | grep -o 'sha256:[a-f0-9]*'; }
           tag_toolchain() {
-            MAN=$(curl -s -u "${{ github.repository_owner }}:${TOKEN}" \
-              -H 'Accept: application/vnd.docker.distribution.manifest.v2+json,application/vnd.oci.image.manifest.v1+json' \
-              "https://${REGISTRY}/v2/${IMAGE}/manifests/$1") || return 0
-            CFG=$(printf '%s' "$MAN" | grep -o '"digest": *"sha256:[a-f0-9]*"' | head -1 | grep -o 'sha256:[a-f0-9]*') || return 0
+            MAN=$(fetch_manifest "$1") || return 0
+            if printf '%s' "$MAN" | grep -q '"manifests"'; then
+              CHILD=$(first_digest "$MAN")
+              [ -n "$CHILD" ] || return 0
+              MAN=$(fetch_manifest "$CHILD") || return 0
+            fi
+            CFG=$(first_digest "$MAN") || return 0
             [ -n "$CFG" ] || return 0
             BLOB=$(curl -s -u "${{ github.repository_owner }}:${TOKEN}" "https://${REGISTRY}/v2/${IMAGE}/blobs/$CFG") || return 0
             P=$(printf '%s' "$BLOB" | grep -o '"dev.milesward.pnpm-version":"[^"]*"' | cut -d'"' -f4 || true)