diff --git a/.github/workflows/docker.publish.yml b/.github/workflows/docker.publish.yml
index 52083af..3594ded 100644
--- a/.github/workflows/docker.publish.yml
+++ b/.github/workflows/docker.publish.yml
@@ -126,9 +126,13 @@ jobs:
           set -euo pipefail
 
           retry() {
-            local attempt=1
+            local attempt=1 max_attempts=5
             until "$@"; do
-              (( attempt >= 5 )) && return 1
+              if (( attempt >= max_attempts )); then
+                echo "Command failed after ${max_attempts} attempts: $*" >&2
+                return 1
+              fi
+              echo "Retrying failed command in $((attempt * 2)) seconds: $*" >&2
               sleep "$((attempt * 2))"
               attempt=$((attempt + 1))
             done
@@ -136,39 +140,75 @@ jobs:
 
           get_httpd_digest() {
             local output digest
-            output="$(docker buildx imagetools inspect httpd:alpine 2>&1)" || { echo "$output" >&2; return 1; }
-            digest="$(printf '%s\n' "$output" | awk '$1 == "Digest:" {print $2; exit}')"
-            [[ -n "$digest" ]] || return 1
+            output="$(docker buildx imagetools inspect httpd:alpine 2>&1)" || {
+              echo "$output" >&2
+              return 1
+            }
+            digest="$(awk '$1 == "Digest:" {print $2; exit}' <<<"$output")"
+            [[ "$digest" =~ ^sha256:[0-9a-f]{64}$ ]] || {
+              echo 'Could not resolve a valid httpd:alpine digest.' >&2
+              return 1
+            }
             printf '%s\n' "$digest"
           }
 
           get_scriptomatic_sha() {
-            git ls-remote https://github.com/infocyph/Scriptomatic.git refs/heads/main | awk 'NF {print $1; exit}'
+            local output sha
+            output="$(git ls-remote https://github.com/infocyph/Scriptomatic.git refs/heads/main 2>&1)" || {
+              echo "$output" >&2
+              return 1
+            }
+            sha="$(awk 'NF {print $1; exit}' <<<"$output")"
+            [[ "$sha" =~ ^[0-9a-f]{40}$ ]] || {
+              echo 'Could not resolve a valid Scriptomatic main revision.' >&2
+              return 1
+            }
+            printf '%s\n' "$sha"
           }
 
           get_toolset_release() {
-            gh api repos/infocyph/Toolset/releases/latest --jq '.tag_name // empty'
+            local tag
+            tag="$(gh api repos/infocyph/Toolset/releases/latest --jq '.tag_name // empty')" || return 1
+            [[ "$tag" =~ ^v?[0-9]+\.[0-9]+(\.[0-9]+)?(-rc\.[0-9]+)?$ ]] || {
+              echo "Could not resolve a valid latest Toolset release: $tag" >&2
+              return 1
+            }
+            printf '%s\n' "$tag"
           }
 
           get_installer_sha() {
-            local file
+            local release="$1" file checksum_output sha
             file="$(mktemp)"
-            curl --fail --silent --show-error --location \
+            if ! curl --fail --silent --show-error --location \
               --retry 5 --retry-all-errors --retry-delay 2 \
               --connect-timeout 15 --max-time 120 \
-              https://github.com/infocyph/Toolset/releases/latest/download/install.sh \
-              -o "$file"
-            test -s "$file"
-            sha256sum "$file" | awk '{print $1}'
+              "https://github.com/infocyph/Toolset/releases/download/${release}/install.sh" \
+              -o "$file"; then
+              rm -f "$file"
+              return 1
+            fi
+            if [[ ! -s "$file" ]]; then
+              echo "Toolset installer is empty for release $release." >&2
+              rm -f "$file"
+              return 1
+            fi
+            checksum_output="$(sha256sum "$file")" || {
+              rm -f "$file"
+              return 1
+            }
             rm -f "$file"
+            sha="${checksum_output%% *}"
+            [[ "$sha" =~ ^[0-9a-f]{64}$ ]] || {
+              echo "Could not calculate Toolset installer checksum for $release." >&2
+              return 1
+            }
+            printf '%s\n' "$sha"
           }
 
           HTTPD_ALPINE_DIGEST="$(retry get_httpd_digest)"
           SCRIPTOMATIC_MAIN_SHA="$(retry get_scriptomatic_sha)"
           TOOLSET_RELEASE="$(retry get_toolset_release)"
-          TOOLSET_INSTALLER_SHA256="$(retry get_installer_sha)"
-
-          [[ -n "$HTTPD_ALPINE_DIGEST" && -n "$SCRIPTOMATIC_MAIN_SHA" && -n "$TOOLSET_RELEASE" && -n "$TOOLSET_INSTALLER_SHA256" ]]
+          TOOLSET_INSTALLER_SHA256="$(retry get_installer_sha "$TOOLSET_RELEASE")"
 
           {
             echo "HTTPD_ALPINE_DIGEST=$HTTPD_ALPINE_DIGEST"
@@ -177,6 +217,15 @@ jobs:
             echo "TOOLSET_INSTALLER_SHA256=$TOOLSET_INSTALLER_SHA256"
           } >> "$GITHUB_ENV"
 
+          {
+            echo '## Upstream snapshot'
+            echo
+            echo "- httpd:alpine: \`$HTTPD_ALPINE_DIGEST\`"
+            echo "- Scriptomatic main: \`$SCRIPTOMATIC_MAIN_SHA\`"
+            echo "- Toolset release: \`$TOOLSET_RELEASE\`"
+            echo "- Toolset installer SHA-256: \`$TOOLSET_INSTALLER_SHA256\`"
+          } >> "$GITHUB_STEP_SUMMARY"
+
       - name: Build fresh amd64 release candidate
         uses: docker/build-push-action@v7
         with:
@@ -187,6 +236,11 @@ jobs:
           no-cache: true
           push: false
           tags: infocyph/apache:publish-candidate
+          build-args: |
+            HTTPD_ALPINE_REF=httpd:alpine@${{ env.HTTPD_ALPINE_DIGEST }}
+            SCRIPTOMATIC_REF=${{ env.SCRIPTOMATIC_MAIN_SHA }}
+            TOOLSET_RELEASE=${{ env.TOOLSET_RELEASE }}
+            TOOLSET_INSTALLER_SHA256=${{ env.TOOLSET_INSTALLER_SHA256 }}
           cache-to: type=gha,scope=apache-publish-amd64,mode=max
 
       - name: Record candidate runtime resolution
@@ -229,6 +283,11 @@ jobs:
           no-cache: true
           push: false
           tags: infocyph/apache:publish-candidate-arm64
+          build-args: |
+            HTTPD_ALPINE_REF=httpd:alpine@${{ env.HTTPD_ALPINE_DIGEST }}
+            SCRIPTOMATIC_REF=${{ env.SCRIPTOMATIC_MAIN_SHA }}
+            TOOLSET_RELEASE=${{ env.TOOLSET_RELEASE }}
+            TOOLSET_INSTALLER_SHA256=${{ env.TOOLSET_INSTALLER_SHA256 }}
           cache-to: type=gha,scope=apache-publish-arm64,mode=max
 
       - name: Final arm64 release-candidate gate
@@ -243,29 +302,6 @@ jobs:
             chromacat --version
           '
 
-      - name: Revalidate rolling upstreams before publish
-        env:
-          GH_TOKEN: ${{ github.token }}
-        run: |
-          set -euo pipefail
-
-          current_httpd="$(docker buildx imagetools inspect httpd:alpine | awk '$1 == "Digest:" {print $2; exit}')"
-          current_scriptomatic="$(git ls-remote https://github.com/infocyph/Scriptomatic.git refs/heads/main | awk 'NF {print $1; exit}')"
-          current_toolset="$(gh api repos/infocyph/Toolset/releases/latest --jq '.tag_name // empty')"
-          file="$(mktemp)"
-          trap 'rm -f "$file"' EXIT
-          curl --fail --silent --show-error --location \
-            --retry 5 --retry-all-errors --retry-delay 2 \
-            --connect-timeout 15 --max-time 120 \
-            https://github.com/infocyph/Toolset/releases/latest/download/install.sh \
-            -o "$file"
-          current_installer="$(sha256sum "$file" | awk '{print $1}')"
-
-          test "$current_httpd" = "$HTTPD_ALPINE_DIGEST"
-          test "$current_scriptomatic" = "$SCRIPTOMATIC_MAIN_SHA"
-          test "$current_toolset" = "$TOOLSET_RELEASE"
-          test "$current_installer" = "$TOOLSET_INSTALLER_SHA256"
-
       - name: Log in to Docker Hub
         uses: docker/login-action@v4
         with:
@@ -331,6 +367,11 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          build-args: |
+            HTTPD_ALPINE_REF=httpd:alpine@${{ env.HTTPD_ALPINE_DIGEST }}
+            SCRIPTOMATIC_REF=${{ env.SCRIPTOMATIC_MAIN_SHA }}
+            TOOLSET_RELEASE=${{ env.TOOLSET_RELEASE }}
+            TOOLSET_INSTALLER_SHA256=${{ env.TOOLSET_INSTALLER_SHA256 }}
           cache-from: |
             type=gha,scope=apache-publish-amd64
             type=gha,scope=apache-publish-arm64
@@ -362,8 +403,8 @@ jobs:
             local ref="$1" output digest
             for _ in $(seq 1 12); do
               output="$(docker buildx imagetools inspect "$ref" 2>&1 || true)"
-              digest="$(printf '%s\n' "$output" | awk '/^Digest:/ {print $2; exit}')"
-              if [[ -n "$digest" ]]; then
+              digest="$(awk '/^Digest:/ {print $2; exit}' <<<"$output")"
+              if [[ "$digest" =~ ^sha256:[0-9a-f]{64}$ ]]; then
                 printf '%s\n' "$digest"
                 return 0
               fi
diff --git a/Dockerfile b/Dockerfile
index 0a0dabb..f112076 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,5 @@
-FROM httpd:alpine
+ARG HTTPD_ALPINE_REF=httpd:alpine
+FROM ${HTTPD_ALPINE_REF}
 
 LABEL org.opencontainers.image.source="https://github.com/infocyph/docker-apache"
 LABEL org.opencontainers.image.description="Hardened LocalDevStack Apache backend with PHP-FPM, TLS and HTTP/2 support"
@@ -6,6 +7,9 @@ LABEL org.opencontainers.image.licenses="MIT"
 LABEL org.opencontainers.image.authors="infocyph,abmmhasan"
 
 ARG TZ=Asia/Dhaka
+ARG SCRIPTOMATIC_REF=main
+ARG TOOLSET_RELEASE=latest
+ARG TOOLSET_INSTALLER_SHA256=
 
 ENV APACHE_LOG_DIR=/var/log/apache2 \
     SERVER_NAME=localhost \
@@ -39,17 +43,29 @@ COPY scripts/healthcheck.sh /usr/local/bin/healthcheck
 RUN set -eux; \
     curl -fsSL --retry 3 --retry-all-errors --retry-delay 1 \
       --connect-timeout 10 --max-time 120 \
-      "https://raw.githubusercontent.com/infocyph/Scriptomatic/main/bash/banner.sh" \
+      "https://raw.githubusercontent.com/infocyph/Scriptomatic/${SCRIPTOMATIC_REF}/bash/banner.sh" \
       -o /usr/local/bin/show-banner; \
     test -s /usr/local/bin/show-banner; \
     bash -n /usr/local/bin/show-banner; \
+    if [ "$TOOLSET_RELEASE" = latest ]; then \
+      toolset_installer_url="https://github.com/infocyph/Toolset/releases/latest/download/install.sh"; \
+    else \
+      toolset_installer_url="https://github.com/infocyph/Toolset/releases/download/${TOOLSET_RELEASE}/install.sh"; \
+    fi; \
     curl -fsSL --retry 3 --retry-all-errors --retry-delay 1 \
       --connect-timeout 10 --max-time 120 \
-      "https://github.com/infocyph/Toolset/releases/latest/download/install.sh" \
+      "$toolset_installer_url" \
       -o /tmp/toolset-install.sh; \
     test -s /tmp/toolset-install.sh; \
+    if [ -n "$TOOLSET_INSTALLER_SHA256" ]; then \
+      printf '%s  %s\n' "$TOOLSET_INSTALLER_SHA256" /tmp/toolset-install.sh | sha256sum -c -; \
+    fi; \
     bash -n /tmp/toolset-install.sh; \
-    bash /tmp/toolset-install.sh --prefix /usr/local/bin chromacat; \
+    if [ "$TOOLSET_RELEASE" = latest ]; then \
+      bash /tmp/toolset-install.sh --latest --prefix /usr/local/bin chromacat; \
+    else \
+      bash /tmp/toolset-install.sh --release "$TOOLSET_RELEASE" --prefix /usr/local/bin chromacat; \
+    fi; \
     chromacat --version; \
     rm -f /tmp/toolset-install.sh; \
     chmod +x \
diff --git a/tests/release-contract.sh b/tests/release-contract.sh
index 1d4f5ca..1e6bb73 100755
--- a/tests/release-contract.sh
+++ b/tests/release-contract.sh
@@ -16,6 +16,14 @@ for contract in \
   "releases/tags/\${MANUAL_RELEASE_TAG}" \
   'PUBLISH_RELEASE_TAG' \
   'Enforce immutable release tags' \
+  'Snapshot rolling upstream inputs' \
+  'retry get_httpd_digest' \
+  'retry get_scriptomatic_sha' \
+  'retry get_toolset_release' \
+  "HTTPD_ALPINE_REF=httpd:alpine@\${{ env.HTTPD_ALPINE_DIGEST }}" \
+  "SCRIPTOMATIC_REF=\${{ env.SCRIPTOMATIC_MAIN_SHA }}" \
+  "TOOLSET_RELEASE=\${{ env.TOOLSET_RELEASE }}" \
+  "TOOLSET_INSTALLER_SHA256=\${{ env.TOOLSET_INSTALLER_SHA256 }}" \
   'linux/amd64,linux/arm64' \
   'provenance: mode=max' \
   'sbom: true'; do
@@ -25,6 +33,35 @@ done
 grep -Fq "cron: '0 0 * * 0'" "$workflow"
 grep -Fq 'types: [published]' "$workflow"
 
+for pinned_contract in \
+  "HTTPD_ALPINE_REF=httpd:alpine@\${{ env.HTTPD_ALPINE_DIGEST }}" \
+  "SCRIPTOMATIC_REF=\${{ env.SCRIPTOMATIC_MAIN_SHA }}" \
+  "TOOLSET_RELEASE=\${{ env.TOOLSET_RELEASE }}" \
+  "TOOLSET_INSTALLER_SHA256=\${{ env.TOOLSET_INSTALLER_SHA256 }}"; do
+  pinned_builds="$(grep -cF "$pinned_contract" "$workflow")"
+  if [[ "$pinned_builds" -ne 3 ]]; then
+    echo "Expected all three publish builds to use pinned input: $pinned_contract; found $pinned_builds." >&2
+    exit 1
+  fi
+done
+
+if grep -Fq 'Revalidate rolling upstreams before publish' "$workflow"; then
+  echo 'Publish workflow must not re-resolve mutable upstreams after immutable snapshotting.' >&2
+  exit 1
+fi
+if grep -Fq 'imagetools inspect httpd:alpine | awk' "$workflow"; then
+  echo 'Unsafe pipefail-sensitive httpd digest pipeline detected.' >&2
+  exit 1
+fi
+if grep -Fq 'Scriptomatic.git refs/heads/main | awk' "$workflow"; then
+  echo 'Unsafe pipefail-sensitive Scriptomatic revision pipeline detected.' >&2
+  exit 1
+fi
+if grep -Fq 'Toolset/releases/latest/download/install.sh' "$workflow"; then
+  echo 'Publish workflow must checksum an exact Toolset release installer.' >&2
+  exit 1
+fi
+
 if grep -Fq 'actions/checkout@v4' "$workflow"; then
   echo 'Legacy checkout action detected.' >&2
   exit 1
diff --git a/tests/static.sh b/tests/static.sh
index e614061..f469c87 100755
--- a/tests/static.sh
+++ b/tests/static.sh
@@ -19,7 +19,10 @@ done
 
 shellcheck scripts/*.sh tests/*.sh
 
-grep -Fq 'FROM httpd:alpine' Dockerfile
+grep -Fq 'ARG HTTPD_ALPINE_REF=httpd:alpine' Dockerfile
+grep -Fq "FROM \${HTTPD_ALPINE_REF}" Dockerfile
+grep -Fq 'ARG SCRIPTOMATIC_REF=main' Dockerfile
+grep -Fq 'ARG TOOLSET_RELEASE=latest' Dockerfile
 grep -Fq 'apk upgrade --no-cache' Dockerfile
 grep -Fq 'apache2-utils' Dockerfile
 if grep -Eq '^[[:space:]]+apache-mod-fcgid([[:space:]\\;]|$)' Dockerfile; then
@@ -28,8 +31,11 @@ fi
 if grep -Eq '^[[:space:]]+apache2([[:space:]\\;]|$)' Dockerfile; then
   fail 'Alpine apache2 server package must not be installed'
 fi
-grep -Fq 'Scriptomatic/main/bash/banner.sh' Dockerfile
+grep -Fq "Scriptomatic/\${SCRIPTOMATIC_REF}/bash/banner.sh" Dockerfile
 grep -Fq 'Toolset/releases/latest/download/install.sh' Dockerfile
+grep -Fq "Toolset/releases/download/\${TOOLSET_RELEASE}/install.sh" Dockerfile
+grep -Fq -- "--release \"\$TOOLSET_RELEASE\"" Dockerfile
+grep -Fq -- '--latest --prefix /usr/local/bin chromacat' Dockerfile
 helper_downloads="$(grep -c -- '--connect-timeout 10 --max-time 120' Dockerfile)"
 if [[ "$helper_downloads" -ne 2 ]]; then
   fail 'Both helper downloads must use bounded connect and total timeouts'