diff --git a/.github/actions/verify-migration-idempotency/action.yml b/.github/actions/verify-migration-idempotency/action.yml
new file mode 100644
index 000000000..69453ebc7
--- /dev/null
+++ b/.github/actions/verify-migration-idempotency/action.yml
@@ -0,0 +1,61 @@
+name: Verify migration idempotency
+description: >
+  Dump the schema, reset and rerun migrations, dump again, and diff the two
+  dumps to catch non-idempotent migrations.
+
+inputs:
+  override-file:
+    description: docker compose override file selecting the tenant_db engine; omit for vanilla Postgres
+    required: false
+    default: ""
+  label:
+    description: Engine name used in dump filenames and the mismatch message
+    required: true
+  database-url:
+    description: Connection string the idempotency script migrates against
+    default: postgresql://postgres:postgres@127.0.0.1/postgres
+
+runs:
+  using: composite
+  steps:
+    - name: Dump schema before
+      shell: bash
+      env:
+        OVERRIDE_FILE: ${{ inputs.override-file }}
+      run: |
+        override_arg=""
+        [ -n "$OVERRIDE_FILE" ] && override_arg="-f $OVERRIDE_FILE"
+        docker compose --project-directory . \
+          -f ./.docker/docker-compose-infra.yml $override_arg \
+          exec -T -e PGPASSWORD=postgres tenant_db \
+          pg_dump -h 127.0.0.1 -p 5432 -U postgres -d postgres \
+          --exclude-table-data=storage.migrations \
+          --restrict-key=test \
+          > before-${{ inputs.label }}.sql
+
+    - name: Reset and rerun migrations
+      shell: bash
+      env:
+        DATABASE_URL: ${{ inputs.database-url }}
+      run: npm run migration:test-idempotency
+
+    - name: Dump schema after
+      shell: bash
+      env:
+        OVERRIDE_FILE: ${{ inputs.override-file }}
+      run: |
+        override_arg=""
+        [ -n "$OVERRIDE_FILE" ] && override_arg="-f $OVERRIDE_FILE"
+        docker compose --project-directory . \
+          -f ./.docker/docker-compose-infra.yml $override_arg \
+          exec -T -e PGPASSWORD=postgres tenant_db \
+          pg_dump -h 127.0.0.1 -p 5432 -U postgres -d postgres \
+          --exclude-table-data=storage.migrations \
+          --restrict-key=test \
+          > after-${{ inputs.label }}.sql
+
+    - name: Diff schemas
+      shell: bash
+      run: |
+        diff before-${{ inputs.label }}.sql after-${{ inputs.label }}.sql \
+          || (echo '${{ inputs.label }} schema mismatch!'; exit 1)
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6adcc4618..fd6b3fb1b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -82,22 +82,9 @@ jobs:
           fail-on-error: false
         continue-on-error: true
       - name: Verify migration idempotency
-        env: &migration_idempotency_env
-          DATABASE_URL: postgresql://postgres:postgres@127.0.0.1/postgres
-        run: |
-          pg_dump "$DATABASE_URL" \
-            --exclude-table-data=storage.migrations \
-            --restrict-key=test \
-            > before.sql
-
-          npm run migration:test-idempotency
-
-          pg_dump "$DATABASE_URL" \
-            --exclude-table-data=storage.migrations \
-            --restrict-key=test \
-            > after.sql
-
-          diff before.sql after.sql || (echo 'Schema mismatch!'; exit 1)
+        uses: ./.github/actions/verify-migration-idempotency
+        with:
+          label: postgres
 
   test_oriole:
     name: Test / OrioleDB
@@ -117,29 +104,10 @@ jobs:
           mkdir -p data && chmod -R 777 data && \
           npm run test:oriole:ci
       - name: Verify OrioleDB migration idempotency
-        env: *migration_idempotency_env
-        run: |
-          docker compose --project-directory . \
-            -f ./.docker/docker-compose-infra.yml \
-            -f ./.docker/docker-compose-infra-oriole-override.yml \
-            exec -T tenant_db \
-            pg_dump -U postgres -d postgres \
-            --exclude-table-data=storage.migrations \
-            --restrict-key=test \
-            > before-oriole.sql
-
-          npm run migration:test-idempotency
-
-          docker compose --project-directory . \
-            -f ./.docker/docker-compose-infra.yml \
-            -f ./.docker/docker-compose-infra-oriole-override.yml \
-            exec -T tenant_db \
-            pg_dump -U postgres -d postgres \
-            --exclude-table-data=storage.migrations \
-            --restrict-key=test \
-            > after-oriole.sql
-
-          diff before-oriole.sql after-oriole.sql || (echo 'Oriole schema mismatch!'; exit 1)
+        uses: ./.github/actions/verify-migration-idempotency
+        with:
+          override-file: ./.docker/docker-compose-infra-oriole-override.yml
+          label: oriole
 
   test_multigres:
     name: Test / Multigres
@@ -160,6 +128,11 @@ jobs:
         run: |
           mkdir -p data && chmod -R 777 data && \
           npm run test:multigres:ci
+      - name: Verify Multigres migration idempotency
+        uses: ./.github/actions/verify-migration-idempotency
+        with:
+          override-file: ./.docker/docker-compose-infra-multigres-override.yml
+          label: multigres
 
   coveralls_finish:
     name: Coveralls / Finalize