diff --git a/src/renderer/components/extensions/ExtensionStoreView.tsx b/src/renderer/components/extensions/ExtensionStoreView.tsx
index 8f0c7130..fbcf7d5e 100644
--- a/src/renderer/components/extensions/ExtensionStoreView.tsx
+++ b/src/renderer/components/extensions/ExtensionStoreView.tsx
@@ -30,6 +30,7 @@ import { ExtensionsSubTabTrigger } from './ExtensionsSubTabTrigger';
 export const ExtensionStoreView = (): React.JSX.Element => {
   const tabId = useTabIdOptional();
   const fetchPluginCatalog = useStore((s) => s.fetchPluginCatalog);
+  const fetchCliStatus = useStore((s) => s.fetchCliStatus);
   const fetchApiKeys = useStore((s) => s.fetchApiKeys);
   const fetchSkillsCatalog = useStore((s) => s.fetchSkillsCatalog);
   const mcpBrowse = useStore((s) => s.mcpBrowse);
@@ -38,7 +39,9 @@ export const ExtensionStoreView = (): React.JSX.Element => {
   const mcpBrowseLoading = useStore((s) => s.mcpBrowseLoading);
   const skillsLoading = useStore((s) => s.skillsLoading);
   const cliStatus = useStore((s) => s.cliStatus);
+  const cliStatusLoading = useStore((s) => s.cliStatusLoading);
   const cliInstalled = cliStatus?.installed ?? true; // assume installed until checked
+  const openDashboard = useStore((s) => s.openDashboard);
   const hasOngoingSessions = useStore((s) => s.sessions.some((sess) => sess.isOngoing));
   const projects = useStore((s) => s.projects);
   const extensionsTabProjectId = useStore((s) =>
@@ -97,6 +100,10 @@ export const ExtensionStoreView = (): React.JSX.Element => {
     void fetchPluginCatalog(projectPath ?? undefined);
   }, [fetchPluginCatalog, projectPath]);
 
+  useEffect(() => {
+    void fetchCliStatus();
+  }, [fetchCliStatus]);
+
   // Fetch MCP installed state on mount
   useEffect(() => {
     void mcpFetchInstalled(projectPath ?? undefined);
@@ -121,6 +128,71 @@ export const ExtensionStoreView = (): React.JSX.Element => {
   }, [fetchPluginCatalog, fetchSkillsCatalog, mcpBrowse, mcpFetchInstalled, projectPath]);
 
   const isRefreshing = pluginCatalogLoading || mcpBrowseLoading || skillsLoading;
+  const cliStatusBanner = useMemo(() => {
+    if (cliStatusLoading || cliStatus === null) {
+      return (
+        <div className="bg-surface/70 mx-4 mt-3 flex items-start gap-3 rounded-md border border-border px-4 py-3">
+          <Info className="mt-0.5 size-4 shrink-0 text-text-secondary" />
+          <div>
+            <p className="text-sm font-medium text-text">Checking Claude CLI availability</p>
+            <p className="mt-0.5 text-xs text-text-muted">
+              Extensions need Claude CLI to install plugins, run MCP servers, and validate auth.
+            </p>
+          </div>
+        </div>
+      );
+    }
+
+    if (!cliStatus.installed) {
+      return (
+        <div className="mx-4 mt-3 flex items-start gap-3 rounded-md border border-amber-500/30 bg-amber-500/5 px-4 py-3">
+          <AlertTriangle className="mt-0.5 size-4 shrink-0 text-amber-400" />
+          <div className="min-w-0 flex-1">
+            <p className="text-sm font-medium text-amber-300">Claude CLI is not available</p>
+            <p className="mt-0.5 text-xs text-text-muted">
+              Plugin installs are disabled until Claude CLI is installed. Open the Dashboard to
+              install it and retry.
+            </p>
+          </div>
+          <Button size="sm" variant="outline" onClick={openDashboard}>
+            Open Dashboard
+          </Button>
+        </div>
+      );
+    }
+
+    if (!cliStatus.authLoggedIn) {
+      return (
+        <div className="mx-4 mt-3 flex items-start gap-3 rounded-md border border-amber-500/30 bg-amber-500/5 px-4 py-3">
+          <AlertTriangle className="mt-0.5 size-4 shrink-0 text-amber-400" />
+          <div className="min-w-0 flex-1">
+            <p className="text-sm font-medium text-amber-300">Claude CLI needs sign-in</p>
+            <p className="mt-0.5 text-xs text-text-muted">
+              Claude CLI was found
+              {cliStatus.installedVersion ? ` (${cliStatus.installedVersion})` : ''}, but plugin
+              installs are disabled until you sign in from the Dashboard.
+            </p>
+          </div>
+          <Button size="sm" variant="outline" onClick={openDashboard}>
+            Open Dashboard
+          </Button>
+        </div>
+      );
+    }
+
+    return (
+      <div className="mx-4 mt-3 flex items-start gap-3 rounded-md border border-emerald-500/30 bg-emerald-500/5 px-4 py-3">
+        <Info className="mt-0.5 size-4 shrink-0 text-emerald-300" />
+        <div>
+          <p className="text-sm font-medium text-emerald-300">Claude CLI is ready</p>
+          <p className="mt-0.5 text-xs text-text-muted">
+            Plugins can be installed from this page
+            {cliStatus.installedVersion ? ` using Claude CLI ${cliStatus.installedVersion}` : ''}.
+          </p>
+        </div>
+      </div>
+    );
+  }, [cliStatus, cliStatusLoading, openDashboard]);
 
   // Browser mode guard
   if (!api.plugins && !api.mcpRegistry && !api.skills) {
@@ -138,6 +210,7 @@ export const ExtensionStoreView = (): React.JSX.Element => {
   return (
     <TooltipProvider>
       <div className="flex flex-1 flex-col overflow-hidden">
+        {cliStatusBanner}
         <div className="flex-1 overflow-y-auto">
           {/* Header */}
           <div className="flex items-center justify-between px-6 py-4">
diff --git a/src/renderer/components/extensions/common/InstallButton.tsx b/src/renderer/components/extensions/common/InstallButton.tsx
index 5d45a257..ea609745 100644
--- a/src/renderer/components/extensions/common/InstallButton.tsx
+++ b/src/renderer/components/extensions/common/InstallButton.tsx
@@ -37,8 +37,20 @@ export const InstallButton = ({
   errorMessage,
 }: InstallButtonProps) => {
   const cliStatus = useStore((s) => s.cliStatus);
-  const cliMissing = cliStatus !== null && !cliStatus.installed;
-  const isDisabled = disabled || cliMissing;
+  const cliStatusLoading = useStore((s) => s.cliStatusLoading);
+  const cliUnknown = cliStatus === null;
+  const cliMissing = cliStatus?.installed === false;
+  const authMissing = cliStatus?.installed === true && !cliStatus.authLoggedIn;
+  const disableReason = cliStatusLoading
+    ? 'Checking Claude CLI status...'
+    : cliUnknown
+      ? 'Checking Claude CLI availability...'
+      : cliMissing
+        ? 'Claude CLI required. Install it from the Dashboard.'
+        : authMissing
+          ? 'Claude CLI is installed but not signed in. Open the Dashboard to sign in.'
+          : null;
+  const isDisabled = disabled || Boolean(disableReason);
   const [lastAction, setLastAction] = useState<'install' | 'uninstall' | null>(null);
 
   useEffect(() => {
@@ -91,23 +103,30 @@ export const InstallButton = ({
       </Button>
     );
 
-    if (errorMessage) {
+    const tooltipMessage = disableReason ?? errorMessage;
+
+    if (tooltipMessage) {
       return (
-        <TooltipProvider>
-          <Tooltip>
-            <TooltipTrigger asChild>
-              <span tabIndex={0}>{retryButton}</span>
-            </TooltipTrigger>
-            <TooltipContent className="max-w-64 text-red-300">{errorMessage}</TooltipContent>
-          </Tooltip>
-        </TooltipProvider>
+        <div className="flex max-w-64 flex-col items-end gap-1">
+          <TooltipProvider>
+            <Tooltip>
+              <TooltipTrigger asChild>
+                <span tabIndex={0}>{retryButton}</span>
+              </TooltipTrigger>
+              <TooltipContent className="max-w-64 text-red-300">{tooltipMessage}</TooltipContent>
+            </Tooltip>
+          </TooltipProvider>
+          {errorMessage && !disableReason ? (
+            <p className="text-right text-[11px] leading-4 text-red-300">{errorMessage}</p>
+          ) : null}
+        </div>
       );
     }
 
     return retryButton;
   }
 
-  // idle — wrap in tooltip when CLI missing
+  // idle — wrap in tooltip when install is unavailable
   const button = isInstalled ? (
     <Button
       size={size}
@@ -138,14 +157,14 @@ export const InstallButton = ({
     </Button>
   );
 
-  if (cliMissing) {
+  if (disableReason) {
     return (
       <TooltipProvider>
         <Tooltip>
           <TooltipTrigger asChild>
             <span tabIndex={0}>{button}</span>
           </TooltipTrigger>
-          <TooltipContent>Claude CLI required</TooltipContent>
+          <TooltipContent className="max-w-64">{disableReason}</TooltipContent>
         </Tooltip>
       </TooltipProvider>
     );
diff --git a/src/renderer/components/extensions/plugins/PluginCard.tsx b/src/renderer/components/extensions/plugins/PluginCard.tsx
index be2a7379..3a2a9bfb 100644
--- a/src/renderer/components/extensions/plugins/PluginCard.tsx
+++ b/src/renderer/components/extensions/plugins/PluginCard.tsx
@@ -98,7 +98,7 @@ export const PluginCard = ({ plugin, index, onClick }: PluginCardProps): React.J
       </p>
 
       {/* Footer: author + version + install button */}
-      <div className="flex items-center justify-between gap-2">
+      <div className="flex items-start justify-between gap-2">
         <div className="flex min-w-0 items-center gap-3 text-xs text-text-muted">
           <span className="truncate">{plugin.author?.name ?? 'Unknown author'}</span>
           {plugin.version && (
diff --git a/src/renderer/store/slices/extensionsSlice.ts b/src/renderer/store/slices/extensionsSlice.ts
index 067a1eba..7d283fb1 100644
--- a/src/renderer/store/slices/extensionsSlice.ts
+++ b/src/renderer/store/slices/extensionsSlice.ts
@@ -4,6 +4,7 @@
  */
 
 import { api } from '@renderer/api';
+import { CLI_NOT_FOUND_MESSAGE } from '@shared/constants/cli';
 
 import type { AppState } from '../types';
 import type {
@@ -143,6 +144,10 @@ function getSkillsCatalogKey(projectPath?: string): string {
 
 /** Duration to show "success" state before returning to idle */
 const SUCCESS_DISPLAY_MS = 2_000;
+const CLI_AUTH_REQUIRED_MESSAGE =
+  'Claude CLI is installed but not signed in. Go to the Dashboard and sign in to enable plugin installs.';
+const CLI_STATUS_UNKNOWN_MESSAGE =
+  'Unable to verify Claude CLI status. Open the Dashboard and check the CLI before retrying.';
 
 export const createExtensionsSlice: StateCreator<AppState, [], [], ExtensionsSlice> = (
   set,
@@ -552,8 +557,36 @@ export const createExtensionsSlice: StateCreator<AppState, [], [], ExtensionsSli
   installPlugin: async (request: PluginInstallRequest) => {
     if (!api.plugins) return;
 
+    const preflightState = get();
+    if (preflightState.cliStatus === null || preflightState.cliStatusLoading) {
+      try {
+        await preflightState.fetchCliStatus();
+      } catch {
+        // fetchCliStatus stores the error in cliStatusError; map to a user-facing install error below.
+      }
+    }
+
+    const cliStatus = get().cliStatus;
+    const preflightError =
+      cliStatus === null
+        ? CLI_STATUS_UNKNOWN_MESSAGE
+        : !cliStatus.installed
+          ? CLI_NOT_FOUND_MESSAGE
+          : !cliStatus.authLoggedIn
+            ? CLI_AUTH_REQUIRED_MESSAGE
+            : null;
+
+    if (preflightError) {
+      set((prev) => ({
+        pluginInstallProgress: { ...prev.pluginInstallProgress, [request.pluginId]: 'error' },
+        installErrors: { ...prev.installErrors, [request.pluginId]: preflightError },
+      }));
+      return;
+    }
+
     set((prev) => ({
       pluginInstallProgress: { ...prev.pluginInstallProgress, [request.pluginId]: 'pending' },
+      installErrors: { ...prev.installErrors, [request.pluginId]: '' },
     }));
 
     try {