diff --git a/.gitignore b/.gitignore
index 460d943f..3475f32a 100755
--- a/.gitignore
+++ b/.gitignore
@@ -69,6 +69,7 @@ cloudflare_provider.tf
 tiers.tf
 stacks/*/cloudflare_provider.tf
 stacks/*/tiers.tf
+stacks/*/terragrunt_rendered.json
 
 # Kubernetes config (sensitive)
 config
diff --git a/docs/post-mortems/2026-04-18-authentik-outpost-shm-full.md b/docs/post-mortems/2026-04-18-authentik-outpost-shm-full.md
index 9b735a97..5cd22fd1 100644
--- a/docs/post-mortems/2026-04-18-authentik-outpost-shm-full.md
+++ b/docs/post-mortems/2026-04-18-authentik-outpost-shm-full.md
@@ -109,9 +109,9 @@ Contributing distractions:
 
 | Priority | Action | Type | Details | Status |
 |----------|--------|------|---------|--------|
-| P1 | Prometheus alert on outpost `/dev/shm` usage > 80% | Alert | Metric: `container_fs_usage_bytes{container!="",namespace="authentik",pod=~"ak-outpost-.*"} / container_fs_limit_bytes > 0.8`. Firing threshold 15 min, severity warning. | TODO |
-| P1 | Prometheus alert on sustained 400 rate on forward-auth middleware | Alert | `increase(traefik_service_requests_total{code="400",service=~".*-viktorbarzin-me@.*"}[15m]) > 100` — catches mass-failure patterns at the Traefik level before the outpost is silently broken. | TODO |
+| P1 | Prometheus alerts on outpost `/dev/shm` fill (two thresholds) | Alert | Group `Authentik Outpost` added in `stacks/monitoring/modules/monitoring/prometheus_chart_values.tpl`. `AuthentikOutpostMemoryHigh` (warning, working set > 1.5 GiB for 15m) + `AuthentikOutpostMemoryCritical` (critical, > 1.8 GiB for 5m) + `AuthentikOutpostRestarts` (warning, > 2 restarts in 30m). Applied 2026-04-18 13:16 UTC; loaded in Prometheus, state=inactive. | **DONE** |
 | P1 | Uptime-Kuma meta-monitor: "N+ external monitors down simultaneously" | Alert | Either a Prometheus rule over `uptime_kuma_monitor_status == 0` counts, or a dedicated external probe. Very strong signal of shared-infra failure. | TODO |
+| P1 | Bump tmpfs `sizeLimit` from 512Mi → 2Gi | Config | Patched outpost `kubernetes_json_patches` via Authentik API. 2026-04-18 13:06 UTC. Gives ~8× growth headroom at current probe rate before needing reconsideration. | **DONE** |
 
 ### P2 — Codify the fix so it survives drift
 
diff --git a/stacks/monitoring/modules/monitoring/prometheus_chart_values.tpl b/stacks/monitoring/modules/monitoring/prometheus_chart_values.tpl
index 6e6a6d04..5188c1ca 100755
--- a/stacks/monitoring/modules/monitoring/prometheus_chart_values.tpl
+++ b/stacks/monitoring/modules/monitoring/prometheus_chart_values.tpl
@@ -1907,6 +1907,38 @@ serverFiles:
               severity: warning
             annotations:
               summary: "{{ $value | printf \"%.0f\" }} service(s) externally unreachable but internally healthy — check Cloudflare tunnel, DNS, or Traefik routing"
+      - name: "Authentik Outpost"
+        # Guards against the 2026-04-18 incident where /dev/shm filled with
+        # gorilla/sessions FileStore files (~44k files at ~1.5KB each) and the
+        # outpost returned HTTP 400 on every forward-auth request.
+        # See docs/post-mortems/2026-04-18-authentik-outpost-shm-full.md.
+        rules:
+          - alert: AuthentikOutpostMemoryHigh
+            # Working set includes /dev/shm tmpfs contents (session files).
+            # sizeLimit on the outpost emptyDir is 2Gi; warn at 75% to leave
+            # plenty of headroom for mitigation before ENOSPC.
+            expr: container_memory_working_set_bytes{namespace="authentik", pod=~"ak-outpost-.*", container="proxy"} > 1.5 * 1024 * 1024 * 1024
+            for: 15m
+            labels:
+              severity: warning
+            annotations:
+              summary: "Authentik outpost working set {{ $value | humanize1024 }} — /dev/shm may be filling with session files (threshold 1.5 GiB of 2 GiB sizeLimit)"
+          - alert: AuthentikOutpostMemoryCritical
+            expr: container_memory_working_set_bytes{namespace="authentik", pod=~"ak-outpost-.*", container="proxy"} > 1.8 * 1024 * 1024 * 1024
+            for: 5m
+            labels:
+              severity: critical
+            annotations:
+              summary: "Authentik outpost near /dev/shm fill ({{ $value | humanize1024 }}) — imminent forward-auth failure. Restart pod: kubectl -n authentik delete pod -l goauthentik.io/outpost-name=authentik-embedded-outpost"
+          - alert: AuthentikOutpostRestarts
+            # Pod restarts on a stateless outpost usually mean OOM or crash.
+            # Normal is 0; we expect one manual rollout per incident/upgrade.
+            expr: increase(kube_pod_container_status_restarts_total{namespace="authentik", pod=~"ak-outpost-.*"}[30m]) > 2
+            for: 5m
+            labels:
+              severity: warning
+            annotations:
+              summary: "Authentik outpost restarted {{ $value | printf \"%.0f\" }} times in 30m — check for OOM or crash loop"
 
 extraScrapeConfigs: |
   - job_name: 'proxmox-host'