diff --git a/frontend/src/client/i18n.ts b/frontend/src/client/i18n.ts
index 97fd575..dbe7214 100644
--- a/frontend/src/client/i18n.ts
+++ b/frontend/src/client/i18n.ts
@@ -1558,6 +1558,10 @@ const translations: Record<Lang, Record<string, string>> = {
     "paliadin.stop": "Stop",
     "paliadin.reset": "Neue Unterhaltung",
     "paliadin.error.local_only": "Paliadin läuft nur lokal. Diese Instanz hat kein tmux/claude installiert — lokal mit ./paliad starten.",
+    "paliadin.error.mriver_unreachable": "mRiver ist offline — Paliadin nicht erreichbar. Mach mRiver an, oder nutze Paliadin lokal mit ./paliad.",
+    "paliadin.error.shim_auth_failed": "Paliadin-Authentifizierung fehlgeschlagen. SSH-Schlüssel oder Berechtigung auf mRiver prüfen.",
+    "paliadin.error.shim_error": "Paliadin-Fehler auf mRiver. tmux/claude-Pane prüfen.",
+    "paliadin.error.timeout": "Paliadin antwortet nicht (Timeout 60s). Nochmal versuchen.",
     "paliadin.error.connection_lost": "Verbindung verloren.",
     "paliadin.error.upstream": "Fehler beim Senden.",
     "nav.admin.paliadin": "Paliadin Monitor",
@@ -3553,6 +3557,10 @@ const translations: Record<Lang, Record<string, string>> = {
     "paliadin.stop": "Stop",
     "paliadin.reset": "New conversation",
     "paliadin.error.local_only": "Paliadin only runs locally. This instance has no tmux/claude installed — start it locally via ./paliad.",
+    "paliadin.error.mriver_unreachable": "mRiver is offline — Paliadin can't reach it. Wake mRiver, or run Paliadin locally with ./paliad.",
+    "paliadin.error.shim_auth_failed": "Paliadin auth failed. Check the SSH key or authorized_keys on mRiver.",
+    "paliadin.error.shim_error": "Paliadin error on mRiver. Check the tmux/claude pane.",
+    "paliadin.error.timeout": "Paliadin didn't respond in time (60s). Try again.",
     "paliadin.error.connection_lost": "Connection lost.",
     "paliadin.error.upstream": "Send failed.",
     "nav.admin.paliadin": "Paliadin Monitor",
diff --git a/frontend/src/client/paliadin.ts b/frontend/src/client/paliadin.ts
index acde8d1..d3c174e 100644
--- a/frontend/src/client/paliadin.ts
+++ b/frontend/src/client/paliadin.ts
@@ -210,8 +210,24 @@ function friendlyErrorMessage(data: unknown): string {
   }
   try {
     const parsed = JSON.parse(data) as { code?: string };
-    if (parsed.code === "tmux_unavailable") {
-      return t("paliadin.error.local_only");
+    switch (parsed.code) {
+      case "tmux_unavailable":
+        // Local PoC path: paliad is running on a host without tmux/claude
+        // (typically the legacy laptop-only build).
+        return t("paliadin.error.local_only");
+      case "mriver_unreachable":
+        // t-paliad-151: prod path's mRiver is offline (laptop asleep, off
+        // tailnet, or paliadin-shim missing).
+        return t("paliadin.error.mriver_unreachable");
+      case "shim_auth_failed":
+        // SSH key wrong or authorized_keys drifted.
+        return t("paliadin.error.shim_auth_failed");
+      case "shim_error":
+      case "bootstrap_failed":
+        // Generic remote shim failure or system-prompt bootstrap error.
+        return t("paliadin.error.shim_error");
+      case "timeout":
+        return t("paliadin.error.timeout");
     }
   } catch {
     // Not JSON — fall through to the generic connection-lost message
diff --git a/frontend/src/i18n-keys.ts b/frontend/src/i18n-keys.ts
index ad85ce8..706ab7e 100644
--- a/frontend/src/i18n-keys.ts
+++ b/frontend/src/i18n-keys.ts
@@ -1423,6 +1423,10 @@ export type I18nKey =
   | "paliadin.empty"
   | "paliadin.error.connection_lost"
   | "paliadin.error.local_only"
+  | "paliadin.error.mriver_unreachable"
+  | "paliadin.error.shim_auth_failed"
+  | "paliadin.error.shim_error"
+  | "paliadin.error.timeout"
   | "paliadin.error.upstream"
   | "paliadin.heading"
   | "paliadin.input.placeholder"