fix(xai): reject unsupported multi-agent model refs before runtime fallback

extensions/xai/index.ts

@@ -262,6 +262,12 @@ export default defineSingleProviderPluginEntry({
     resolveThinkingProfile,
     isModernModelRef: ({ modelId }) => isModernXaiModel(modelId),
     classifyFailoverReason: ({ errorMessage }) => classifyXaiFailoverReason(errorMessage),
+    buildUnknownModelHint: ({ modelId }) => {
+      if (modelId.toLowerCase().includes("multi-agent")) {
+        return "xAI multi-agent models are not supported on the standard xAI API-key provider path. See https://docs.openclaw.ai/providers/xai for supported models.";
+      }
+      return undefined;
+    },
   },
   register(api) {
     api.registerWebSearchProvider(createXaiWebSearchProvider());

src/agents/embedded-agent-runner/model.ts

@@ -522,6 +522,7 @@ function mergeStaticCatalogInlineModel(
 }
 
 function hasConfiguredFallbackSurface(params: {
+  provider?: string;
   providerConfig: InlineProviderConfig | undefined;
   configuredModel: ReturnType<typeof findConfiguredProviderModel>;
   modelId: string;
@@ -532,6 +533,18 @@ function hasConfiguredFallbackSurface(params: {
   if (params.configuredModel) {
     return true;
   }
+  // xAI's catalog explicitly excludes multi-agent model ids (they require a
+  // different upstream API surface than the standard API-key provider path).
+  // If the provider rejected this model via its dynamic resolution, do not
+  // synthesize a configured-provider fallback that will silently 400.
+  // See: https://docs.openclaw.ai/providers/xai
+  if (
+    params.provider &&
+    normalizeProviderId(params.provider) === "xai" &&
+    params.modelId.toLowerCase().includes("multi-agent")
+  ) {
+    return false;
+  }
   const baseUrl = params.providerConfig?.baseUrl?.trim();
   return Boolean(baseUrl);
 }
@@ -1245,7 +1258,7 @@ function resolveConfiguredFallbackModel(params: {
   const providerConfig = resolveConfiguredProviderConfig(cfg, provider);
   const requestTimeoutMs = resolveProviderRequestTimeoutMs(providerConfig?.timeoutSeconds);
   const configuredModel = findConfiguredProviderModel(providerConfig, provider, modelId);
-  if (!hasConfiguredFallbackSurface({ providerConfig, configuredModel, modelId })) {
+  if (!hasConfiguredFallbackSurface({ provider, providerConfig, configuredModel, modelId })) {
     return undefined;
   }
   const staticCatalogModel = resolveBundledStaticCatalogModel({