diff --git a/.gitignore b/.gitignore
index 853f259..d7a79f7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,4 @@ tests/test_helper/bats-assert/
 
 # Test artifacts
 headers.txt
+put-headers.txt
diff --git a/AGENTS.md b/AGENTS.md
index 6cffdf4..b7e07e1 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -33,7 +33,7 @@ Step flow in `action.yml`:
 2. `resolve-build-config.sh` / `verify-architecture.sh` — platforms, cache scope and outputs, incl. multi-arch handling.
 3. `login-registries.sh` → `docker/build-push-action`.
 4. Multi-arch (`multiarch-mode`): `build` jobs push by digest and upload digest artifacts; one `merge` job runs `merge-manifests.sh` and then does the GitOps/Upwind steps. `build` mode skips all GitOps steps.
-5. `retag-image.sh` (release/custom tag path) — polls the primary registry's v2 manifest API for the `main-<sha8>`/`master-<sha8>` image, retags it, then replicates to additional registries with `docker buildx imagetools create`.
+5. `retag-image.sh` (release/custom tag path) — polls the primary registry's v2 manifest API for the `main-<sha8>`/`master-<sha8>` image (or exactly the `docker-retag-digest` manifest when set), retags it, then replicates to additional registries with `docker buildx imagetools create`.
 6. `update-gitops.sh` — checks out the GitOps repo and edits YAML with `yq`. Environment by ref: `main`/`master` → `gitops-stage`, `dev` → `gitops-dev`, tags → `gitops-prod`; any other ref simulates the dev update without committing. Each input line is `<file> <yq-path>`; a path ending in `.tag` or pointing at a map with `tag`/`repository` gets only the tag, otherwise the full image reference. Also stamps `<deployment-domain>/…` annotations. Commit + push retries with backoff.
 
 Shared libs in `scripts/lib/` (sourced, never executed):
diff --git a/README.md b/README.md
index 99463f1..bffa659 100644
--- a/README.md
+++ b/README.md
@@ -279,6 +279,7 @@ Notes:
 | `multiarch-digests-path`    | Directory holding the per-architecture digest files                                                                            | `/tmp/gitops-action-digests`                         |
 | `docker-build-provenance`   | Generate [provenance](https://docs.docker.com/build/attestations/slsa-provenance/) attestation for the build                   | `false`                                              |
 | `docker-build-no-cache`    | Re-execute Dockerfile steps and skip external cache import/export. Base images are always checked for updates. | `false` |
+| `docker-retag-digest`       | Digest (`sha256:…`) to retag on a release or custom tag instead of whatever `main-<sha8>`/`master-<sha8>` points to at retag time, so a caller retags exactly the digest it verified |                                                      |
 | `docker-disable-retagging`  | Disables retagging of existing images and run a new build instead                                                              | `false`                                              |
 | `deployment-annotations`    | Stamp deployment-tracking annotations (`deploy.staffbase.com/*`) onto updated GitOps manifests. See [Deployment tracking annotations](#deployment-tracking-annotations) | `true`                      |
 | `deployment-domain`         | Key namespace for deployment-tracking metadata. Used verbatim for annotation keys (`<domain>/...`) and reversed to reverse-DNS for label keys (`com.staffbase.deploy.*`) | `deploy.staffbase.com`  |
diff --git a/action.yml b/action.yml
index b1716dc..94195a3 100644
--- a/action.yml
+++ b/action.yml
@@ -74,6 +74,10 @@ inputs:
     description: 'Directory holding the per-architecture digest files.'
     required: false
     default: '/tmp/gitops-action-digests'
+  docker-retag-digest:
+    description: 'Digest (sha256:<64 hex>) of the image to retag on a release or custom tag. When set, exactly this manifest is retagged instead of whatever main-<sha8>/master-<sha8> points to at retag time, so a caller can retag the digest it verified. Optional; defaults to the tag lookup.'
+    required: false
+    default: ''
   docker-disable-retagging:
     description: 'Disable retagging of existing images'
     required: false
@@ -281,6 +285,7 @@ runs:
         INPUT_DOCKER_IMAGE: ${{ inputs.docker-image }}
         INPUT_TAG: ${{ steps.preparation.outputs.tag }}
         INPUT_LATEST: ${{ steps.preparation.outputs.latest }}
+        INPUT_RETAG_DIGEST: ${{ inputs.docker-retag-digest }}
       run: ${{ github.action_path }}/scripts/retag-image.sh
 
     - name: Checkout GitOps Repository
diff --git a/scripts/retag-image.sh b/scripts/retag-image.sh
index d4a153a..e82cef9 100755
--- a/scripts/retag-image.sh
+++ b/scripts/retag-image.sh
@@ -11,6 +11,8 @@
 #                    INPUT_DOCKER_REGISTRY_API, INPUT_DOCKER_IMAGE, INPUT_TAG,
 #                    INPUT_LATEST
 # Optional env vars: INPUT_DOCKER_USERNAME, INPUT_DOCKER_PASSWORD,
+#                    INPUT_RETAG_DIGEST (sha256:<64 hex>; retag exactly this
+#                    manifest instead of resolving the master-/main- tag),
 #                    RETAG_TIMEOUT_SECONDS (default: 300),
 #                    RETAG_POLL_INTERVAL (default: 10)
 #
@@ -56,26 +58,58 @@ TIMEOUT="${RETAG_TIMEOUT_SECONDS:-300}"
 POLL_INTERVAL="${RETAG_POLL_INTERVAL:-10}"
 
 CHECK_EXISTING_TAGS="master-${GITHUB_SHA::8} main-${GITHUB_SHA::8}"
+RETAG_DIGEST="${INPUT_RETAG_DIGEST:-}"
+if [[ -n "$RETAG_DIGEST" ]]; then
+  if [[ ! "$RETAG_DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]; then
+    log_error "INPUT_RETAG_DIGEST must be sha256:<64 lowercase hex characters>"
+    exit 1
+  fi
+  command -v sha256sum &>/dev/null || require_tool shasum
+  # A caller that verified a digest gets exactly that manifest; a tag could be moved after verification.
+  CHECK_EXISTING_TAGS="$RETAG_DIGEST"
+fi
 ACCEPT_HEADER="application/vnd.docker.distribution.manifest.v2+json, application/vnd.docker.distribution.manifest.list.v2+json, application/vnd.oci.image.manifest.v1+json, application/vnd.oci.image.index.v1+json"
 
 echo "CHECK_EXISTING_TAGS: ${CHECK_EXISTING_TAGS}"
-echo "Check if an image already exists for ${INPUT_DOCKER_IMAGE}:main|master-${GITHUB_SHA::8}"
+echo "Check if an image already exists for ${INPUT_DOCKER_IMAGE} (${CHECK_EXISTING_TAGS// /, })"
+
+# The manifest is kept in a file and uploaded with --data-binary so its bytes,
+# and therefore its digest, stay exactly as fetched.
+MANIFEST_FILE="$(mktemp)"
+trap 'rm -f "$MANIFEST_FILE"' EXIT
+
+sha256_file() {
+  if command -v sha256sum &>/dev/null; then
+    sha256sum "$1" | cut -d' ' -f1
+  else
+    shasum -a 256 "$1" | cut -d' ' -f1
+  fi
+}
 
 retag_manifest() {
   local target_tag="$1"
-  local manifest="$2"
-  local content_type="$3"
+  local content_type="$2"
+  local digest_args=()
+  [[ -z "$RETAG_DIGEST" ]] || digest_args=(-D put-headers.txt)
   curl --fail-with-body -X PUT \
     -H "Content-Type: ${content_type}" \
     "${AUTH_ARGS[@]}" \
-    -d "${manifest}" \
+    ${digest_args[@]+"${digest_args[@]}"} \
+    --data-binary "@${MANIFEST_FILE}" \
     "${INPUT_DOCKER_REGISTRY_API}${INPUT_DOCKER_IMAGE}/manifests/${target_tag}"
+  if [[ -n "$RETAG_DIGEST" ]]; then
+    local stored
+    stored=$(grep -i "^Docker-Content-Digest:" put-headers.txt | cut -d' ' -f2 | tr -d '\r' || true)
+    if [[ "$stored" != "$RETAG_DIGEST" ]]; then
+      log_error "${INPUT_DOCKER_IMAGE}:${target_tag} was stored as ${stored:-an unknown digest}, not ${RETAG_DIGEST}"
+      exit 1
+    fi
+  fi
 }
 
 foundImage=false
 DETECTED_CONTENT_TYPE=""
 DIGEST=""
-MANIFEST=""
 
 end=$((SECONDS + TIMEOUT))
 attempt=1
@@ -84,12 +118,13 @@ while [ $SECONDS -lt $end ]; do
   echo "Poll attempt ${attempt} (${remaining}s remaining)..."
 
   for tag in $CHECK_EXISTING_TAGS; do
-    MANIFEST=$(curl -s -D headers.txt \
+    : > "$MANIFEST_FILE"
+    curl -s -D headers.txt -o "$MANIFEST_FILE" \
       -H "Accept: ${ACCEPT_HEADER}" \
       "${AUTH_ARGS[@]}" \
-      "${INPUT_DOCKER_REGISTRY_API}${INPUT_DOCKER_IMAGE}/manifests/${tag}")
+      "${INPUT_DOCKER_REGISTRY_API}${INPUT_DOCKER_IMAGE}/manifests/${tag}"
 
-    if [[ $MANIFEST == *"errors"* ]]; then
+    if grep -q "errors" "$MANIFEST_FILE"; then
       echo "No image found for ${INPUT_DOCKER_IMAGE}:${tag}"
       continue
     else
@@ -97,6 +132,14 @@ while [ $SECONDS -lt $end ]; do
       foundImage=true
       DETECTED_CONTENT_TYPE=$(grep -i "^Content-Type:" headers.txt | cut -d' ' -f2 | tr -d '\r')
       DIGEST=$(grep -i "^Docker-Content-Digest:" headers.txt | cut -d' ' -f2 | tr -d '\r')
+      if [[ -n "$RETAG_DIGEST" && "$DIGEST" != "$RETAG_DIGEST" ]]; then
+        log_error "The registry returned ${DIGEST:-no digest} for ${INPUT_DOCKER_IMAGE}@${RETAG_DIGEST}"
+        exit 1
+      fi
+      if [[ -n "$RETAG_DIGEST" && "sha256:$(sha256_file "$MANIFEST_FILE")" != "$RETAG_DIGEST" ]]; then
+        log_error "The manifest bytes fetched for ${INPUT_DOCKER_IMAGE}@${RETAG_DIGEST} do not match that digest"
+        exit 1
+      fi
       break 2
     fi
   done
@@ -106,15 +149,15 @@ while [ $SECONDS -lt $end ]; do
 done
 
 if [[ $foundImage == false ]]; then
-  log_error "No image found for ${INPUT_DOCKER_IMAGE}:main|master-${GITHUB_SHA::8} within ${TIMEOUT} seconds"
+  log_error "No image found for ${INPUT_DOCKER_IMAGE} (${CHECK_EXISTING_TAGS// /, }) within ${TIMEOUT} seconds"
   exit 1
 fi
 
 echo "Retagging image with release version and :latest tags for ${INPUT_DOCKER_IMAGE}"
 echo "Using Content-Type: ${DETECTED_CONTENT_TYPE}"
 
-retag_manifest "$INPUT_TAG" "$MANIFEST" "$DETECTED_CONTENT_TYPE"
-retag_manifest "$INPUT_LATEST" "$MANIFEST" "$DETECTED_CONTENT_TYPE"
+retag_manifest "$INPUT_TAG" "$DETECTED_CONTENT_TYPE"
+retag_manifest "$INPUT_LATEST" "$DETECTED_CONTENT_TYPE"
 
 if [[ ${#REGISTRIES[@]} -gt 1 ]]; then
   require_tool docker
diff --git a/tests/retag-image.bats b/tests/retag-image.bats
index 672b1c9..a00f150 100644
--- a/tests/retag-image.bats
+++ b/tests/retag-image.bats
@@ -33,6 +33,8 @@ create_curl_mock() {
 # Record call
 echo "curl \$*" >> "${TEST_TEMP_DIR}/curl_calls.log"
 
+out_file=\$(echo "\$*" | sed -n 's/.*-o \([^ ]*\).*/\1/p')
+
 # Handle different call patterns
 case "\$*" in
   *manifests/master-*|*manifests/main-*)
@@ -45,9 +47,9 @@ Content-Type: application/vnd.docker.distribution.manifest.v2+json
 Docker-Content-Digest: sha256:abc123def456
 HEADERS
       fi
-      echo '{"schemaVersion": 2}'
+      echo '{"schemaVersion": 2}' > "\$out_file"
     else
-      echo '{"errors": [{"code": "MANIFEST_UNKNOWN"}]}'
+      echo '{"errors": [{"code": "MANIFEST_UNKNOWN"}]}' > "\$out_file"
     fi
     ;;
   *"--fail-with-body"*"-X PUT"*)
@@ -159,3 +161,144 @@ MOCK_EOF
   run test -f "${TEST_TEMP_DIR}/docker_calls.log"
   assert_failure
 }
+
+# Digest of the body create_digest_curl_mock serves for a manifest fetched by digest.
+served_manifest_digest() {
+  echo "sha256:$(echo '{"schemaVersion": 2}' | shasum -a 256 | cut -d' ' -f1)"
+}
+
+create_digest_curl_mock() {
+  local returned_digest="$1"
+  local stored_digest="${2:-$1}"
+  cat > "${TEST_TEMP_DIR}/mocks/curl" << MOCK_EOF
+#!/usr/bin/env bash
+echo "curl \$*" >> "${TEST_TEMP_DIR}/curl_calls.log"
+out_file=\$(echo "\$*" | sed -n 's/.*-o \([^ ]*\).*/\1/p')
+case "\$*" in
+  *"--fail-with-body"*"-X PUT"*)
+    headers_file=\$(echo "\$*" | sed 's/.*-D \([^ ]*\).*/\1/')
+    printf 'Docker-Content-Digest: %s\n' "$stored_digest" > "\$headers_file"
+    echo "PUT OK"
+    ;;
+  *manifests/sha256:*)
+    headers_file=\$(echo "\$*" | sed 's/.*-D \([^ ]*\).*/\1/')
+    printf 'Content-Type: application/vnd.oci.image.index.v1+json\nDocker-Content-Digest: %s\n' "$returned_digest" > "\$headers_file"
+    echo '{"schemaVersion": 2}' > "\$out_file"
+    ;;
+  *)
+    echo '{"errors": [{"code": "MANIFEST_UNKNOWN"}]}' > "\$out_file"
+    ;;
+esac
+MOCK_EOF
+  chmod +x "${TEST_TEMP_DIR}/mocks/curl"
+}
+
+@test "retags exactly the given digest without resolving the main/master tag" {
+  digest="$(served_manifest_digest)"
+  export INPUT_RETAG_DIGEST="$digest"
+  create_digest_curl_mock "$digest"
+
+  run "$SCRIPT"
+  assert_success
+  assert_output_value "digest" "$digest"
+
+  run cat "${TEST_TEMP_DIR}/curl_calls.log"
+  assert_output --partial "my-service/manifests/${digest}"
+  refute_output --partial "manifests/main-"
+  refute_output --partial "manifests/master-"
+  assert_output --partial "my-service/manifests/1.0.0"
+  assert_output --partial "my-service/manifests/latest"
+}
+
+@test "fails without retagging when the registry returns another digest" {
+  export INPUT_RETAG_DIGEST="sha256:$(printf 'a%.0s' {1..64})"
+  create_digest_curl_mock "sha256:$(printf 'b%.0s' {1..64})"
+
+  run "$SCRIPT"
+  assert_failure
+  assert_output --partial "The registry returned sha256:bbbb"
+
+  run cat "${TEST_TEMP_DIR}/curl_calls.log"
+  refute_output --partial "-X PUT"
+}
+
+@test "rejects a malformed digest before any registry call" {
+  export INPUT_RETAG_DIGEST="main-abcdef12"
+  create_digest_curl_mock "unused"
+
+  run "$SCRIPT"
+  assert_failure
+  assert_output --partial "INPUT_RETAG_DIGEST must be sha256"
+  [ ! -e "${TEST_TEMP_DIR}/curl_calls.log" ]
+}
+
+@test "fails when the registry stores the retagged manifest under another digest" {
+  export INPUT_RETAG_DIGEST="$(served_manifest_digest)"
+  create_digest_curl_mock "$INPUT_RETAG_DIGEST" "sha256:$(printf 'c%.0s' {1..64})"
+
+  run "$SCRIPT"
+  assert_failure
+  assert_output --partial "my-service:1.0.0 was stored as sha256:cccc"
+}
+
+# A registry that, like a real one, addresses manifests by the sha256 of their
+# exact bytes: GET serves a newline-terminated manifest and PUT stores whatever
+# bytes it received under their own digest.
+create_byte_registry_mock() {
+  local served_digest="${1:-}"
+  printf '{\n  "schemaVersion": 2,\n  "mediaType": "application/vnd.oci.image.index.v1+json",\n  "manifests": []\n}\n' > "${TEST_TEMP_DIR}/manifest.json"
+  MANIFEST_DIGEST="sha256:$(shasum -a 256 "${TEST_TEMP_DIR}/manifest.json" | cut -d' ' -f1)"
+  cat > "${TEST_TEMP_DIR}/mocks/curl" << MOCK_EOF
+#!/usr/bin/env bash
+echo "curl \$*" >> "${TEST_TEMP_DIR}/curl_calls.log"
+headers_file="" out_file="" data="" put=false
+args=("\$@")
+for ((i = 0; i < \${#args[@]}; i++)); do
+  case "\${args[i]}" in
+    -D) headers_file="\${args[i+1]}" ;;
+    -o) out_file="\${args[i+1]}" ;;
+    -d|--data-binary) data="\${args[i+1]}" ;;
+    PUT) put=true ;;
+  esac
+done
+if [[ "\$put" == true ]]; then
+  if [[ "\$data" == @* ]]; then cat "\${data#@}"; else printf '%s' "\$data"; fi > "${TEST_TEMP_DIR}/uploaded.json"
+  printf 'Docker-Content-Digest: sha256:%s\n' "\$(shasum -a 256 "${TEST_TEMP_DIR}/uploaded.json" | cut -d' ' -f1)" > "\$headers_file"
+  exit 0
+fi
+printf 'Content-Type: application/vnd.oci.image.index.v1+json\nDocker-Content-Digest: %s\n' "${served_digest:-$MANIFEST_DIGEST}" > "\$headers_file"
+if [[ -n "\$out_file" ]]; then cat "${TEST_TEMP_DIR}/manifest.json" > "\$out_file"; else cat "${TEST_TEMP_DIR}/manifest.json"; fi
+MOCK_EOF
+  chmod +x "${TEST_TEMP_DIR}/mocks/curl"
+}
+
+@test "retags a newline-terminated manifest byte for byte under the verified digest" {
+  create_byte_registry_mock
+  export INPUT_RETAG_DIGEST="$MANIFEST_DIGEST"
+
+  run "$SCRIPT"
+  assert_success
+  assert_output_value "digest" "$MANIFEST_DIGEST"
+  cmp "${TEST_TEMP_DIR}/manifest.json" "${TEST_TEMP_DIR}/uploaded.json"
+}
+
+@test "fails without retagging when the fetched manifest bytes do not match the digest" {
+  create_byte_registry_mock "sha256:$(printf 'a%.0s' {1..64})"
+  export INPUT_RETAG_DIGEST="sha256:$(printf 'a%.0s' {1..64})"
+
+  run "$SCRIPT"
+  assert_failure
+  assert_output --partial "do not match"
+
+  run cat "${TEST_TEMP_DIR}/curl_calls.log"
+  refute_output --partial "-X PUT"
+}
+
+@test "uploads the fetched manifest bytes unchanged without a verified digest" {
+  create_byte_registry_mock
+
+  run "$SCRIPT"
+  assert_success
+  assert_output_value "digest" "$MANIFEST_DIGEST"
+  cmp "${TEST_TEMP_DIR}/manifest.json" "${TEST_TEMP_DIR}/uploaded.json"
+}