diff --git a/packages/cli/src/gemini.tsx b/packages/cli/src/gemini.tsx
index 74091874..3c0b151b 100644
--- a/packages/cli/src/gemini.tsx
+++ b/packages/cli/src/gemini.tsx
@@ -215,7 +215,7 @@ export async function main() {
     'event.timestamp': new Date().toISOString(),
     prompt: input,
     prompt_id,
-    auth_type: config.getContentGeneratorConfig().authType!,
+    auth_type: config.getContentGeneratorConfig()?.authType,
     prompt_length: input.length,
   });
 
diff --git a/packages/cli/src/nonInteractiveCli.ts b/packages/cli/src/nonInteractiveCli.ts
index 2db28eba..7bc0f6aa 100644
--- a/packages/cli/src/nonInteractiveCli.ts
+++ b/packages/cli/src/nonInteractiveCli.ts
@@ -160,7 +160,7 @@ export async function runNonInteractive(
     console.error(
       parseAndFormatApiError(
         error,
-        config.getContentGeneratorConfig().authType,
+        config.getContentGeneratorConfig()?.authType,
       ),
     );
     process.exit(1);
diff --git a/packages/cli/src/ui/hooks/useGeminiStream.ts b/packages/cli/src/ui/hooks/useGeminiStream.ts
index 05fb9835..21d57b3b 100644
--- a/packages/cli/src/ui/hooks/useGeminiStream.ts
+++ b/packages/cli/src/ui/hooks/useGeminiStream.ts
@@ -226,7 +226,7 @@ export const useGeminiStream = (
           new UserPromptEvent(
             trimmedQuery.length,
             prompt_id,
-            config.getContentGeneratorConfig().authType!,
+            config.getContentGeneratorConfig()?.authType,
             trimmedQuery,
           ),
         );
@@ -408,7 +408,7 @@ export const useGeminiStream = (
           type: MessageType.ERROR,
           text: parseAndFormatApiError(
             eventValue.error,
-            config.getContentGeneratorConfig().authType,
+            config.getContentGeneratorConfig()?.authType,
             undefined,
             config.getModel(),
             DEFAULT_GEMINI_FLASH_MODEL,
@@ -588,7 +588,7 @@ export const useGeminiStream = (
               type: MessageType.ERROR,
               text: parseAndFormatApiError(
                 getErrorMessage(error) || 'Unknown error',
-                config.getContentGeneratorConfig().authType,
+                config.getContentGeneratorConfig()?.authType,
                 undefined,
                 config.getModel(),
                 DEFAULT_GEMINI_FLASH_MODEL,
diff --git a/packages/core/src/core/geminiChat.ts b/packages/core/src/core/geminiChat.ts
index ab4f602c..f93470dd 100644
--- a/packages/core/src/core/geminiChat.ts
+++ b/packages/core/src/core/geminiChat.ts
@@ -172,7 +172,7 @@ export class GeminiChat {
         this.config.getModel(),
         durationMs,
         prompt_id,
-        this.config.getContentGeneratorConfig().authType!,
+        this.config.getContentGeneratorConfig()?.authType,
         usageMetadata,
         responseText,
       ),
@@ -194,7 +194,7 @@ export class GeminiChat {
         errorMessage,
         durationMs,
         prompt_id,
-        this.config.getContentGeneratorConfig().authType!,
+        this.config.getContentGeneratorConfig()?.authType,
         errorType,
       ),
     );
diff --git a/packages/core/src/telemetry/types.ts b/packages/core/src/telemetry/types.ts
index 9f6e1462..9ac12050 100644
--- a/packages/core/src/telemetry/types.ts
+++ b/packages/core/src/telemetry/types.ts
@@ -96,13 +96,13 @@ export class UserPromptEvent {
   'event.timestamp': string; // ISO 8601
   prompt_length: number;
   prompt_id: string;
-  auth_type: string;
+  auth_type?: string;
   prompt?: string;
 
   constructor(
     prompt_length: number,
     prompt_Id: string,
-    auth_type: string,
+    auth_type?: string,
     prompt?: string,
   ) {
     this['event.name'] = 'user_prompt';
@@ -167,14 +167,14 @@ export class ApiErrorEvent {
   status_code?: number | string;
   duration_ms: number;
   prompt_id: string;
-  auth_type: string;
+  auth_type?: string;
 
   constructor(
     model: string,
     error: string,
     duration_ms: number,
     prompt_id: string,
-    auth_type: string,
+    auth_type?: string,
     error_type?: string,
     status_code?: number | string,
   ) {
@@ -205,13 +205,13 @@ export class ApiResponseEvent {
   total_token_count: number;
   response_text?: string;
   prompt_id: string;
-  auth_type: string;
+  auth_type?: string;
 
   constructor(
     model: string,
     duration_ms: number,
     prompt_id: string,
-    auth_type: string,
+    auth_type?: string,
     usage_data?: GenerateContentResponseUsageMetadata,
     response_text?: string,
     error?: string,