diff --git a/internal/checkdefaults/defaults.go b/internal/checkdefaults/defaults.go
index ec8bde6..e6f5c0e 100644
--- a/internal/checkdefaults/defaults.go
+++ b/internal/checkdefaults/defaults.go
@@ -24,13 +24,14 @@ import (
 // check_defs.kind values — one semantic kind can expand to several concrete
 // checks (`resource` becomes four ssh-script rows).
 const (
-	KindPing     = "ping"
-	KindResource = "resource"
-	KindUpdates  = "updates"
-	KindProcess  = "process"
-	KindHTTP     = "http"
-	KindCapacity = "capacity"
-	KindBackup   = "backup-freshness"
+	KindPing       = "ping"
+	KindResource   = "resource"
+	KindUpdates    = "updates"
+	KindProcess    = "process"
+	KindHTTP       = "http"
+	KindCapacity   = "capacity"
+	KindBackup     = "backup-freshness"
+	KindCertExpiry = "cert-expiry"
 )
 
 // defaultBackupMaxAge is how long a backup target may go without a new
@@ -246,11 +247,40 @@ func buildKind(kind string, t Target, attrs map[string]any, host, user string, p
 			config:   map[string]any{"url": url, "max_status": 500},
 			interval: 60,
 		}}, ""
+
+	case KindCertExpiry:
+		// The host to TLS-dial for the cert. Prefer an explicit `hostname`
+		// attribute, then `cn`, then a dotted name (a certificate's name is
+		// its CN/SAN). Hourly: expiry changes once a day, but a renewal or a
+		// mis-issued cert is worth noticing within the hour.
+		host := certHost(t, attrs)
+		if host == "" {
+			return nil, "no hostname / cn / dotted name to dial for the cert"
+		}
+		return []checkDef{{
+			kind:     "cert-expiry",
+			config:   map[string]any{"host": host, "warn_days": 30, "crit_days": 7},
+			interval: 3600,
+		}}, ""
 	}
 
 	return nil, "no builder for this kind yet"
 }
 
+// certHost works out the hostname to TLS-dial for a certificate's expiry.
+func certHost(t Target, attrs map[string]any) string {
+	for _, key := range []string{"hostname", "cn", "san"} {
+		if v, ok := attrs[key].(string); ok && v != "" {
+			return v
+		}
+	}
+	// A dotted name is a hostname (hubris.network, media.hubris.network).
+	if strings.Contains(t.Name, ".") && !strings.Contains(t.Name, " ") {
+		return t.Name
+	}
+	return ""
+}
+
 // writeCheck upserts one check_def and its backing check entity.
 //
 // The entity upsert MUST return the row's id. The previous version generated
diff --git a/seeds/inventory.yaml b/seeds/inventory.yaml
index 957594e..9853fde 100644
--- a/seeds/inventory.yaml
+++ b/seeds/inventory.yaml
@@ -339,6 +339,30 @@ entities:
   - {slug: "ingress:sab.hubris.network", type: ingress-route, name: sab.hubris.network,
      attributes: {forward_auth: true}}
 
+  # ─── TLS certificates (Caddy-managed, *.hubris.network) ───────────
+  # One entity per public hostname; the cert-expiry checker dials each on
+  # :443 and reads NotAfter. The cn/name is the hostname the checker dials.
+  - {slug: "cert:proxmox.hubris.network", type: certificate, name: proxmox.hubris.network}
+  - {slug: "cert:git.hubris.network", type: certificate, name: git.hubris.network}
+  - {slug: "cert:auth.hubris.network", type: certificate, name: auth.hubris.network}
+  - {slug: "cert:media.hubris.network", type: certificate, name: media.hubris.network}
+  - {slug: "cert:cloud.hubris.network", type: certificate, name: cloud.hubris.network}
+  - {slug: "cert:paperless.hubris.network", type: certificate, name: paperless.hubris.network}
+  - {slug: "cert:matrix.hubris.network", type: certificate, name: matrix.hubris.network}
+  - {slug: "cert:photos.hubris.network", type: certificate, name: photos.hubris.network}
+  - {slug: "cert:artifacto.hubris.network", type: certificate, name: artifacto.hubris.network}
+  - {slug: "cert:trmnl.hubris.network", type: certificate, name: trmnl.hubris.network}
+  - {slug: "cert:zimaos.hubris.network", type: certificate, name: zimaos.hubris.network}
+  - {slug: "cert:teddy.hubris.network", type: certificate, name: teddy.hubris.network}
+  - {slug: "cert:mcp.hubris.network", type: certificate, name: mcp.hubris.network}
+  - {slug: "cert:house.hubris.network", type: certificate, name: house.hubris.network}
+  - {slug: "cert:books.hubris.network", type: certificate, name: books.hubris.network}
+  - {slug: "cert:seanime.hubris.network", type: certificate, name: seanime.hubris.network}
+  - {slug: "cert:roms.hubris.network", type: certificate, name: roms.hubris.network}
+  - {slug: "cert:jellyseerr.hubris.network", type: certificate, name: jellyseerr.hubris.network}
+  - {slug: "cert:qbit.hubris.network", type: certificate, name: qbit.hubris.network}
+  - {slug: "cert:sab.hubris.network", type: certificate, name: sab.hubris.network}
+
   # ─── Governance ────────────────────────────────────────────────────
   - {slug: "person:dtoro", type: person, name: dtoro,
      attributes: {matrix_id: "@dtoro:avispero"}}
@@ -486,6 +510,28 @@ relationships:
   - {source: "ingress:jellyseerr.hubris.network", target: "service:caddy", type: served-by}
   - {source: "ingress:qbit.hubris.network", target: "service:caddy", type: served-by}
   - {source: "ingress:sab.hubris.network", target: "service:caddy", type: served-by}
+  # Each public route is served with its TLS certificate.
+  - {source: "ingress:proxmox.hubris.network", target: "cert:proxmox.hubris.network", type: uses-certificate}
+  - {source: "ingress:git.hubris.network", target: "cert:git.hubris.network", type: uses-certificate}
+  - {source: "ingress:auth.hubris.network", target: "cert:auth.hubris.network", type: uses-certificate}
+  - {source: "ingress:media.hubris.network", target: "cert:media.hubris.network", type: uses-certificate}
+  - {source: "ingress:cloud.hubris.network", target: "cert:cloud.hubris.network", type: uses-certificate}
+  - {source: "ingress:paperless.hubris.network", target: "cert:paperless.hubris.network", type: uses-certificate}
+  - {source: "ingress:matrix.hubris.network", target: "cert:matrix.hubris.network", type: uses-certificate}
+  - {source: "ingress:photos.hubris.network", target: "cert:photos.hubris.network", type: uses-certificate}
+  - {source: "ingress:artifacto.hubris.network", target: "cert:artifacto.hubris.network", type: uses-certificate}
+  - {source: "ingress:trmnl.hubris.network", target: "cert:trmnl.hubris.network", type: uses-certificate}
+  - {source: "ingress:zimaos.hubris.network", target: "cert:zimaos.hubris.network", type: uses-certificate}
+  - {source: "ingress:teddy.hubris.network", target: "cert:teddy.hubris.network", type: uses-certificate}
+  - {source: "ingress:mcp.hubris.network", target: "cert:mcp.hubris.network", type: uses-certificate}
+  - {source: "ingress:house.hubris.network", target: "cert:house.hubris.network", type: uses-certificate}
+  - {source: "ingress:books.hubris.network", target: "cert:books.hubris.network", type: uses-certificate}
+  - {source: "ingress:seanime.hubris.network", target: "cert:seanime.hubris.network", type: uses-certificate}
+  - {source: "ingress:roms.hubris.network", target: "cert:roms.hubris.network", type: uses-certificate}
+  - {source: "ingress:jellyseerr.hubris.network", target: "cert:jellyseerr.hubris.network", type: uses-certificate}
+  - {source: "ingress:qbit.hubris.network", target: "cert:qbit.hubris.network", type: uses-certificate}
+  - {source: "ingress:sab.hubris.network", target: "cert:sab.hubris.network", type: uses-certificate}
+
   - {source: "ingress:secrets.hubris.network", target: "service:secrets-issuance", type: routes-to}
   - {source: "ingress:house.hubris.network", target: "service:house", type: routes-to}
   - {source: "ingress:books.hubris.network", target: "service:grimmory", type: routes-to}