diff --git a/.github/workflows/preview-env.yml b/.github/workflows/preview-env.yml
index 7cad03c..7addfad 100644
--- a/.github/workflows/preview-env.yml
+++ b/.github/workflows/preview-env.yml
@@ -195,6 +195,42 @@ jobs:
           --services ${{ steps.tf-output.outputs.ecs_service }} \
           --region ${{ env.AWS_REGION }}
 
+      - name: Smoke test preview URL
+        if: github.event.action != 'closed'
+        id: smoke-test
+        env:
+          PREVIEW_URL: ${{ steps.tf-output.outputs.preview_url }}
+        run: |
+          if [ -z "$PREVIEW_URL" ] || [ "$PREVIEW_URL" = "null" ]; then
+            echo "Preview URL missing"
+            echo "http_status=missing" >> "$GITHUB_OUTPUT"
+            echo "http_result=missing-url" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          # Reachability check: allow 404 (app routes might not exist yet) but fail otherwise
+          STATUS=$(curl --silent --output /tmp/preview.headers --write-out '%{http_code}' --head --max-time 30 "$PREVIEW_URL" || true)
+
+          if [ "$STATUS" = "404" ]; then
+            echo "Preview responded with expected 404"
+            echo "http_status=404" >> "$GITHUB_OUTPUT"
+            echo "http_result=allowed-404" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          if [[ "$STATUS" =~ ^[0-9]{3}$ ]] && [ "$STATUS" -ge 200 ] && [ "$STATUS" -lt 400 ]; then
+            echo "Preview responded with status $STATUS"
+            echo "http_status=$STATUS" >> "$GITHUB_OUTPUT"
+            echo "http_result=success" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          echo "Preview responded with unexpected status $STATUS"
+          cat /tmp/preview.headers
+          echo "http_status=$STATUS" >> "$GITHUB_OUTPUT"
+          echo "http_result=unexpected-status" >> "$GITHUB_OUTPUT"
+          exit 0
+
       - name: Comment function name on PR
         if: github.event_name == 'pull_request' && github.event.action != 'closed'
         uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd
@@ -207,6 +243,17 @@ jobs:
             const owner = context.repo.owner;
             const repo = context.repo.repo;
             const issueNumber = context.issue.number;
+            const smokeStatus = '${{ steps.smoke-test.outputs.http_status }}' || 'n/a';
+            const smokeResult = '${{ steps.smoke-test.outputs.http_result }}' || 'not-run';
+
+            const smokeLabels = {
+              success: '✅ Passed',
+              'allowed-404': '✅ Allowed 404',
+              'unexpected-status': '❌ Unexpected status',
+              'missing-url': '❌ Missing URL',
+            };
+
+            const smokeReadable = smokeLabels[smokeResult] ?? smokeResult;
 
             const { data: comments } = await github.rest.issues.listComments({
               owner,
@@ -231,6 +278,7 @@ jobs:
             const lines = [
               '**Deployment Complete**',
               `- Preview URL: [${url}](${url})`,
+              `- Smoke Test: ${smokeReadable} (HTTP ${smokeStatus})`,
               `- ECS Cluster: \`${cluster}\``,
               `- ECS Service: \`${service}\``,
               `- ALB Target: \`${alb}\``,