diff --git a/packages/core/src/telemetry/constants.ts b/packages/core/src/telemetry/constants.ts
index f87148cea2..f6fd14ed34 100644
--- a/packages/core/src/telemetry/constants.ts
+++ b/packages/core/src/telemetry/constants.ts
@@ -30,6 +30,7 @@ export const EVENT_CONTENT_RETRY = 'gemini_cli.chat.content_retry';
 export const EVENT_CONTENT_RETRY_FAILURE =
   'gemini_cli.chat.content_retry_failure';
 export const EVENT_FILE_OPERATION = 'gemini_cli.file_operation';
+export const EVENT_TOOL_OUTPUT_TRUNCATED = 'gemini_cli.tool_output_truncated';
 export const EVENT_MODEL_SLASH_COMMAND = 'gemini_cli.slash_command.model';
 export const EVENT_SMART_EDIT_STRATEGY = 'gemini_cli.smart_edit.strategy';
 export const EVENT_MODEL_ROUTING = 'gemini_cli.model_routing';
diff --git a/packages/core/src/telemetry/loggers.test.ts b/packages/core/src/telemetry/loggers.test.ts
index 99fa6b02fc..6ec5c4588a 100644
--- a/packages/core/src/telemetry/loggers.test.ts
+++ b/packages/core/src/telemetry/loggers.test.ts
@@ -37,6 +37,7 @@ import {
   EVENT_EXTENSION_DISABLE,
   EVENT_EXTENSION_INSTALL,
   EVENT_EXTENSION_UNINSTALL,
+  EVENT_TOOL_OUTPUT_TRUNCATED,
 } from './constants.js';
 import {
   logApiRequest,
@@ -1173,7 +1174,7 @@ describe('loggers', () => {
         attributes: {
           'session.id': 'test-session-id',
           'user.email': 'test-user@example.com',
-          'event.name': 'tool_output_truncated',
+          'event.name': EVENT_TOOL_OUTPUT_TRUNCATED,
           'event.timestamp': '2025-01-01T00:00:00.000Z',
           eventName: 'tool_output_truncated',
           prompt_id: 'prompt-id-1',
diff --git a/packages/core/src/telemetry/loggers.ts b/packages/core/src/telemetry/loggers.ts
index dde56a7136..ef3294f21a 100644
--- a/packages/core/src/telemetry/loggers.ts
+++ b/packages/core/src/telemetry/loggers.ts
@@ -29,6 +29,7 @@ import {
   EVENT_CONTENT_RETRY,
   EVENT_CONTENT_RETRY_FAILURE,
   EVENT_FILE_OPERATION,
+  EVENT_TOOL_OUTPUT_TRUNCATED,
   EVENT_RIPGREP_FALLBACK,
   EVENT_MODEL_ROUTING,
   EVENT_EXTENSION_INSTALL,
@@ -214,7 +215,7 @@ export function logToolOutputTruncated(
   const attributes: LogAttributes = {
     ...getCommonAttributes(config),
     ...event,
-    'event.name': 'tool_output_truncated',
+    'event.name': EVENT_TOOL_OUTPUT_TRUNCATED,
     'event.timestamp': new Date().toISOString(),
   };