diff --git a/.github/workflows/build-docker-image.yml b/.github/workflows/build-docker-image.yml
index 04b9ab7..47f6a8d 100644
--- a/.github/workflows/build-docker-image.yml
+++ b/.github/workflows/build-docker-image.yml
@@ -1,39 +1,26 @@
 name: build-docker-image
-permissions:
-    contents: read
-    id-token: write
 on:
     push:
         branches: [ main ]
     pull_request:
+
 jobs:
+    multiarch:
+        permissions:
+            contents: read
+            id-token: write
+        uses: ./.github/workflows/multiarch-build-workflow.yml
+        with:
+            image_name: synapse
+            google_ar_image_name: us-docker.pkg.dev/sentryio/synapse/image
+            google_workload_identity_provider: projects/868781662168/locations/global/workloadIdentityPools/prod-github/providers/github-oidc-pool
+            google_service_account: gha-gcr-push@sac-prod-sa.iam.gserviceaccount.com
+            push: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
+
+    # Gate job — keeps `build-docker` as a single branch-protection check.
     build-docker:
+        permissions: {}
+        needs: [ multiarch ]
         runs-on: ubuntu-latest
         steps:
-            -   name: Checkout repository
-                uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
-
-            -   name: Set up Docker Buildx
-                uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3
-
-            -   name: Docker build - pull request
-                if: github.event_name == 'pull_request'
-                uses: getsentry/action-build-and-push-images@8fc75e483c09a68721f2c8951292ee17f8821766
-                with:
-                    image_name: synapse
-                    platforms: linux/amd64
-                    ghcr: false
-                    tag_nightly: false
-
-            -   name: Docker build - push to registry
-                if: github.event_name == 'push' && github.ref == 'refs/heads/main'
-                uses: getsentry/action-build-and-push-images@8fc75e483c09a68721f2c8951292ee17f8821766
-                with:
-                    image_name: synapse
-                    platforms: linux/amd64
-                    google_ar: true
-                    google_ar_image_name: us-docker.pkg.dev/sentryio/synapse/image
-                    ghcr: false
-                    tag_nightly: false
-                    google_workload_identity_provider: projects/868781662168/locations/global/workloadIdentityPools/prod-github/providers/github-oidc-pool
-                    google_service_account: gha-gcr-push@sac-prod-sa.iam.gserviceaccount.com
+            -   run: 'true'
diff --git a/.github/workflows/multiarch-build-workflow.yml b/.github/workflows/multiarch-build-workflow.yml
new file mode 100644
index 0000000..3ed07e6
--- /dev/null
+++ b/.github/workflows/multiarch-build-workflow.yml
@@ -0,0 +1,88 @@
+name: multiarch-build-workflow
+
+# Reusable workflow: matrix-builds a Dockerfile per-arch on native runners
+# via getsentry/action-build-and-push-images, then assembles a multi-arch
+# manifest from the per-arch suffixed tags.
+on:
+    workflow_call:
+        inputs:
+            image_name:
+                description: Only feeds GHCR naming in the underlying action; unused here since ghcr is disabled, but still required by the action.
+                required: true
+                type: string
+            google_ar_image_name:
+                description: Fully-qualified GAR image path (e.g. us-docker.pkg.dev/sentryio/synapse/image).
+                required: true
+                type: string
+            push:
+                description: Whether to assemble the manifest.
+                type: boolean
+                default: false
+            google_workload_identity_provider:
+                required: true
+                type: string
+            google_service_account:
+                required: true
+                type: string
+
+jobs:
+    build-arch:
+        strategy:
+            fail-fast: false
+            matrix:
+                include:
+                    -   { platform: linux/amd64, runner: ubuntu-latest, pair: amd64 }
+                    -   { platform: linux/arm64, runner: ubuntu-24.04-arm, pair: arm64 }
+        runs-on: ${{ matrix.runner }}
+        permissions:
+            contents: read
+            id-token: write
+        steps:
+            -   uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+            -   uses: getsentry/action-build-and-push-images@8fc75e483c09a68721f2c8951292ee17f8821766
+                with:
+                    image_name: ${{ inputs.image_name }}
+                    platforms: ${{ matrix.platform }}
+                    # Each matrix leg stages a single arch as :sha-<arch>;
+                    # the assemble job stitches them into the multi-arch :sha and :latest.
+                    # This is the same as Snuba's multiarch workflow.
+                    tag_suffix: -${{ matrix.pair }}
+                    ghcr: false
+                    google_ar: true
+                    google_ar_image_name: ${{ inputs.google_ar_image_name }}
+                    google_workload_identity_provider: ${{ inputs.google_workload_identity_provider }}
+                    google_service_account: ${{ inputs.google_service_account }}
+                    # latest/nightly belong on the assembled manifest, not per-arch.
+                    tag_latest: false
+                    tag_nightly: false
+
+    assemble:
+        needs: [ build-arch ]
+        if: inputs.push
+        runs-on: ubuntu-latest
+        permissions:
+            contents: read
+            id-token: write
+        steps:
+            -   uses: google-github-actions/auth@ba79af03959ebeac9769e648f473a284504d9193 # v2.1.10
+                with:
+                    workload_identity_provider: ${{ inputs.google_workload_identity_provider }}
+                    service_account: ${{ inputs.google_service_account }}
+
+            -   env:
+                    IMAGE: ${{ inputs.google_ar_image_name }}
+                run: gcloud auth configure-docker "$(echo "$IMAGE" | cut -d/ -f1)"
+
+            -   uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3
+
+            -   name: Assemble manifest
+                env:
+                    IMAGE: ${{ inputs.google_ar_image_name }}
+                    SHA: ${{ github.sha }}
+                run: |
+                    docker buildx imagetools create \
+                        -t "${IMAGE}:${SHA}" \
+                        -t "${IMAGE}:latest" \
+                        "${IMAGE}:${SHA}-amd64" \
+                        "${IMAGE}:${SHA}-arm64"
+                    docker buildx imagetools inspect "${IMAGE}:${SHA}"
diff --git a/Dockerfile b/Dockerfile
index 54dd92f..dedb422 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -18,12 +18,14 @@ COPY shared ./shared
 
 RUN cargo build --release
 
+RUN mkdir /stage && cp --parents /usr/lib/$(gcc -print-multiarch)/libzstd.so.1 /stage
+
 # Runtime stage
 FROM gcr.io/distroless/cc-debian13:nonroot
 WORKDIR /app
 
 COPY --from=builder /app/target/release/synapse synapse
-COPY --from=builder /usr/lib/x86_64-linux-gnu/libzstd.so.1 /usr/lib/x86_64-linux-gnu/libzstd.so.1
+COPY --from=builder /stage/ /
 
 ENTRYPOINT ["/app/synapse"]
 CMD []