fix: address PR feedback for non-interactive and event translator

- Restore 'never' return type for runTerminalExitHandler

- Add TODO for usage event and debugLogger for unknown events

- Check for 'status' in isStructuredError type guard

- Fix unused property build error for experimentalAgentHistorySummarization

packages/cli/src/nonInteractiveCli.ts

@@ -37,6 +37,7 @@ import {
   LegacyAgentSession,
   ToolErrorType,
   geminiPartsToContentParts,
+  debugLogger,
 } from '@google/gemini-cli-core';
 
 import type { Part } from '@google/genai';
@@ -421,9 +422,7 @@ export async function runNonInteractive(
         return errToThrow;
       };
 
-      const runTerminalExitHandler = (
-        handler: () => void | never,
-      ): void | never => {
+      const runTerminalExitHandler = (handler: () => never): never => {
         terminalProcessExitHandled = true;
         return handler();
       };
@@ -615,10 +614,13 @@ export async function runNonInteractive(
           case 'elicitation_request':
           case 'elicitation_response':
           case 'usage':
+          // TODO: We should think about converting this into the usage event.
+          // fallthrough
           case 'custom':
             // Explicitly ignore these non-interactive events
             break;
           default:
+            debugLogger.error('Unknown agent event type:', event);
             event satisfies never;
             break;
         }

packages/core/src/agent/event-translator.ts

@@ -432,6 +432,7 @@ function isStructuredError(error: unknown): error is StructuredError {
   return (
     typeof error === 'object' &&
     error !== null &&
+    'status' in error &&
     'message' in error &&
     typeof error.message === 'string'
   );

packages/core/src/config/config.ts

@@ -2426,6 +2426,11 @@ export class Config implements McpContext, AgentLoopContext {
   getExperimentalAgentHistoryRetainedMessages(): number {
     return this.experimentalAgentHistoryRetainedMessages;
   }
+
+  isExperimentalAgentHistorySummarizationEnabled(): boolean {
+    return this.experimentalAgentHistorySummarization;
+  }
+
   getContextManagementConfig(): ContextManagementConfig {
     return this.contextManagement;
   }