diff --git a/Caddyfile b/Caddyfile
index 29b6001..115c88f 100644
--- a/Caddyfile
+++ b/Caddyfile
@@ -48,10 +48,13 @@
     handle_errors {
         # Don't mask API errors with the SPA shell — return a proper
         # JSON error so the frontend can display a meaningful message.
+        # NOTE: `respond` only accepts `body`/`close` subdirectives; the
+        # Content-Type must be set via a separate `header` directive. An
+        # invalid subdirective is a Caddyfile parse error and crash-loops
+        # the container at startup (issue #20).
         @api path /api/*
-        respond @api `{"code":{err.status_code},"message":"Backend unavailable"}` {err.status_code} {
-            Content-Type application/json
-        }
+        header @api Content-Type application/json
+        respond @api `{"code":{err.status_code},"message":"Backend unavailable"}` {err.status_code}
 
         rewrite * /index.html
         file_server
diff --git a/infra/development/site/deploy-playbook.yml b/infra/development/site/deploy-playbook.yml
index 442b8b4..537e1db 100644
--- a/infra/development/site/deploy-playbook.yml
+++ b/infra/development/site/deploy-playbook.yml
@@ -100,3 +100,53 @@
           {{ pb_logs.stdout | default('') }}
           {{ pb_logs.stderr | default('') }}
       when: pb_health is failed
+
+    # The frontend container carries the SPA + Caddy. An invalid Caddyfile
+    # crash-loops it at startup while the PocketBase gate stays green — that
+    # outage (issue #20) was invisible to CI because the test job swaps in
+    # Caddyfile.test. Gate on the real container actually serving.
+    - name: Wait for the frontend (Caddy) to become healthy
+      ansible.builtin.command: docker exec learning-platform wget -q --spider http://127.0.0.1:80/
+      register: fe_health
+      until: fe_health.rc == 0
+      retries: 18
+      delay: 5
+      changed_when: false
+      ignore_errors: yes
+
+    - name: Collect frontend logs for diagnosis
+      ansible.builtin.command: docker logs --tail 80 learning-platform
+      register: fe_logs
+      when: fe_health is failed
+      changed_when: false
+      failed_when: false
+
+    - name: Abort deploy — frontend is not healthy
+      ansible.builtin.fail:
+        msg: |
+          The frontend (Caddy) container did not become healthy after the deploy.
+          Recent container logs:
+          {{ fe_logs.stdout | default('') }}
+          {{ fe_logs.stderr | default('') }}
+      when: fe_health is failed
+
+    # Observability behind the auth perimeter: surface the end-to-end state
+    # in the CI log on every deploy.
+    - name: Post-deploy smoke report
+      ansible.builtin.shell: |
+        cd /opt/learning-platform
+        echo '--- docker compose ps ---'
+        docker compose ps
+        echo '--- frontend -> pocketbase proxy health ---'
+        docker exec learning-platform wget -q -O - http://127.0.0.1:80/api/health || echo 'PROXY HEALTH FAILED'
+        echo '--- team_members auth methods (OIDC provider present?) ---'
+        docker exec pocketbase-learning wget -q -O - http://127.0.0.1:8090/api/collections/team_members/auth-methods || echo 'AUTH-METHODS FAILED'
+        echo '--- pocketbase logs (tail 30) ---'
+        docker compose logs --tail=30 pocketbase-learning
+      register: smoke_report
+      changed_when: false
+      failed_when: false
+
+    - name: Show smoke report
+      ansible.builtin.debug:
+        msg: "{{ smoke_report.stdout_lines }}"
diff --git a/infra/production/site/deploy-playbook.yml b/infra/production/site/deploy-playbook.yml
index 442b8b4..537e1db 100644
--- a/infra/production/site/deploy-playbook.yml
+++ b/infra/production/site/deploy-playbook.yml
@@ -100,3 +100,53 @@
           {{ pb_logs.stdout | default('') }}
           {{ pb_logs.stderr | default('') }}
       when: pb_health is failed
+
+    # The frontend container carries the SPA + Caddy. An invalid Caddyfile
+    # crash-loops it at startup while the PocketBase gate stays green — that
+    # outage (issue #20) was invisible to CI because the test job swaps in
+    # Caddyfile.test. Gate on the real container actually serving.
+    - name: Wait for the frontend (Caddy) to become healthy
+      ansible.builtin.command: docker exec learning-platform wget -q --spider http://127.0.0.1:80/
+      register: fe_health
+      until: fe_health.rc == 0
+      retries: 18
+      delay: 5
+      changed_when: false
+      ignore_errors: yes
+
+    - name: Collect frontend logs for diagnosis
+      ansible.builtin.command: docker logs --tail 80 learning-platform
+      register: fe_logs
+      when: fe_health is failed
+      changed_when: false
+      failed_when: false
+
+    - name: Abort deploy — frontend is not healthy
+      ansible.builtin.fail:
+        msg: |
+          The frontend (Caddy) container did not become healthy after the deploy.
+          Recent container logs:
+          {{ fe_logs.stdout | default('') }}
+          {{ fe_logs.stderr | default('') }}
+      when: fe_health is failed
+
+    # Observability behind the auth perimeter: surface the end-to-end state
+    # in the CI log on every deploy.
+    - name: Post-deploy smoke report
+      ansible.builtin.shell: |
+        cd /opt/learning-platform
+        echo '--- docker compose ps ---'
+        docker compose ps
+        echo '--- frontend -> pocketbase proxy health ---'
+        docker exec learning-platform wget -q -O - http://127.0.0.1:80/api/health || echo 'PROXY HEALTH FAILED'
+        echo '--- team_members auth methods (OIDC provider present?) ---'
+        docker exec pocketbase-learning wget -q -O - http://127.0.0.1:8090/api/collections/team_members/auth-methods || echo 'AUTH-METHODS FAILED'
+        echo '--- pocketbase logs (tail 30) ---'
+        docker compose logs --tail=30 pocketbase-learning
+      register: smoke_report
+      changed_when: false
+      failed_when: false
+
+    - name: Show smoke report
+      ansible.builtin.debug:
+        msg: "{{ smoke_report.stdout_lines }}"