feat(hooks): implement STOP_EXECUTION and enhance hook decision handling (#15685)

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -39,6 +39,7 @@ import {
   EDIT_TOOL_NAMES,
   processRestorableToolCalls,
   recordToolCallInteractions,
+  ToolErrorType,
 } from '@google/gemini-cli-core';
 import { type Part, type PartListUnion, FinishReason } from '@google/genai';
 import type {
@@ -1153,6 +1154,28 @@ export const useGeminiStream = (
         return;
       }
 
+      // Check if any tool requested to stop execution immediately
+      const stopExecutionTool = geminiTools.find(
+        (tc) => tc.response.errorType === ToolErrorType.STOP_EXECUTION,
+      );
+
+      if (stopExecutionTool && stopExecutionTool.response.error) {
+        addItem(
+          {
+            type: MessageType.INFO,
+            text: `Agent execution stopped: ${stopExecutionTool.response.error.message}`,
+          },
+          Date.now(),
+        );
+        setIsResponding(false);
+
+        const callIdsToMarkAsSubmitted = geminiTools.map(
+          (toolCall) => toolCall.request.callId,
+        );
+        markToolsAsSubmitted(callIdsToMarkAsSubmitted);
+        return;
+      }
+
       // If all the tools were cancelled, don't submit a response to Gemini.
       const allToolsCancelled = geminiTools.every(
         (tc) => tc.status === 'cancelled',