Optimize gateway comms reload behavior and strengthen regression coverage (#496)

src/lib/api-client.ts

@@ -551,6 +551,7 @@ export function createGatewayHttpTransportInvoker(
     if (typeof method !== 'string') {
       throw new Error('gateway:rpc requires method string');
     }
+    validateGatewayRpcParams(method, params);
 
     const timeoutMs =
       typeof timeoutOverride === 'number' && timeoutOverride > 0
@@ -857,6 +858,7 @@ export function createGatewayWsTransportInvoker(options: GatewayWsTransportOptio
     if (typeof method !== 'string') {
       throw new Error('gateway:rpc requires method string');
     }
+    validateGatewayRpcParams(method, params);
 
     const requestTimeoutMs =
       typeof timeoutOverride === 'number' && timeoutOverride > 0
@@ -887,6 +889,17 @@ export function createGatewayWsTransportInvoker(options: GatewayWsTransportOptio
   };
 }
 
+function validateGatewayRpcParams(method: string, params: unknown): void {
+  if (method !== 'config.patch') return;
+  if (!params || typeof params !== 'object' || Array.isArray(params)) {
+    throw new Error('gateway:rpc config.patch requires object params');
+  }
+  const patch = (params as Record<string, unknown>).patch;
+  if (!patch || typeof patch !== 'object' || Array.isArray(patch)) {
+    throw new Error('gateway:rpc config.patch requires object patch');
+  }
+}
+
 let defaultTransportsInitialized = false;
 
 export function initializeDefaultTransports(): void {

src/lib/host-api.ts

@@ -129,6 +129,14 @@ function shouldFallbackToBrowser(message: string): boolean {
     || normalized.includes('window is not defined');
 }
 
+function allowLocalhostFallback(): boolean {
+  try {
+    return window.localStorage.getItem('clawx:allow-localhost-fallback') === '1';
+  } catch {
+    return false;
+  }
+}
+
 export async function hostApiFetch<T>(path: string, init?: RequestInit): Promise<T> {
   const startedAt = Date.now();
   const method = init?.method || 'GET';
@@ -160,6 +168,17 @@ export async function hostApiFetch<T>(path: string, init?: RequestInit): Promise
     if (!shouldFallbackToBrowser(message)) {
       throw normalized;
     }
+    if (!allowLocalhostFallback()) {
+      trackUiEvent('hostapi.fetch_error', {
+        path,
+        method,
+        source: 'ipc-proxy',
+        durationMs: Date.now() - startedAt,
+        message: 'localhost fallback blocked by policy',
+        code: 'CHANNEL_UNAVAILABLE',
+      });
+      throw normalized;
+    }
   }
 
   // Browser-only fallback (non-Electron environments).