From 5d68d8cda59ae24a213f828aef5e1de9b92b1d6f Mon Sep 17 00:00:00 2001
From: Spencer <spencer.tang12@gmail.com>
Date: Thu, 22 Jan 2026 20:16:00 +0000
Subject: [PATCH] fix(core): Resolve AbortSignal MaxListenersExceededWarning
 (#5950) (#16735)

---
 .../core/src/agents/local-executor.test.ts    | 22 ++++++++++++++-----
 .../services/sessionSummaryService.test.ts    | 16 +++++++++-----
 packages/core/src/tools/mcp-client.test.ts    | 11 ++++++----
 packages/core/src/tools/tools.ts              |  2 +-
 .../core/src/utils/llm-edit-fixer.test.ts     | 10 ++++++---
 5 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/packages/core/src/agents/local-executor.test.ts b/packages/core/src/agents/local-executor.test.ts
index e2269e815a..4578bfab8d 100644
--- a/packages/core/src/agents/local-executor.test.ts
+++ b/packages/core/src/agents/local-executor.test.ts
@@ -1369,9 +1369,13 @@ describe('LocalAgentExecutor', () => {
           (async function* () {
             await new Promise<void>((resolve) => {
               // This promise resolves when aborted, ending the generator.
-              signal?.addEventListener('abort', () => {
-                resolve();
-              });
+              signal?.addEventListener(
+                'abort',
+                () => {
+                  resolve();
+                },
+                { once: true },
+              );
             });
           })(),
       );
@@ -1681,7 +1685,9 @@ describe('LocalAgentExecutor', () => {
           (async function* () {
             // This promise never resolves, it waits for abort.
             await new Promise<void>((resolve) => {
-              signal?.addEventListener('abort', () => resolve());
+              signal?.addEventListener('abort', () => resolve(), {
+                once: true,
+              });
             });
           })(),
       );
@@ -1734,7 +1740,9 @@ describe('LocalAgentExecutor', () => {
           // eslint-disable-next-line require-yield
           (async function* () {
             await new Promise<void>((resolve) =>
-              signal?.addEventListener('abort', () => resolve()),
+              signal?.addEventListener('abort', () => resolve(), {
+                once: true,
+              }),
             );
           })(),
       );
@@ -1745,7 +1753,9 @@ describe('LocalAgentExecutor', () => {
           // eslint-disable-next-line require-yield
           (async function* () {
             await new Promise<void>((resolve) =>
-              signal?.addEventListener('abort', () => resolve()),
+              signal?.addEventListener('abort', () => resolve(), {
+                once: true,
+              }),
             );
           })(),
       );
diff --git a/packages/core/src/services/sessionSummaryService.test.ts b/packages/core/src/services/sessionSummaryService.test.ts
index c3362a63c9..1e16c6c120 100644
--- a/packages/core/src/services/sessionSummaryService.test.ts
+++ b/packages/core/src/services/sessionSummaryService.test.ts
@@ -346,12 +346,16 @@ describe('SessionSummaryService', () => {
               10000,
             );
 
-            abortSignal?.addEventListener('abort', () => {
-              clearTimeout(timeoutId);
-              const abortError = new Error('This operation was aborted');
-              abortError.name = 'AbortError';
-              reject(abortError);
-            });
+            abortSignal?.addEventListener(
+              'abort',
+              () => {
+                clearTimeout(timeoutId);
+                const abortError = new Error('This operation was aborted');
+                abortError.name = 'AbortError';
+                reject(abortError);
+              },
+              { once: true },
+            );
           }),
       );
 
diff --git a/packages/core/src/tools/mcp-client.test.ts b/packages/core/src/tools/mcp-client.test.ts
index eb63779bc2..45e06a43c6 100644
--- a/packages/core/src/tools/mcp-client.test.ts
+++ b/packages/core/src/tools/mcp-client.test.ts
@@ -1043,10 +1043,13 @@ describe('mcp-client', () => {
               if (options?.signal?.aborted) {
                 return reject(new Error('Operation aborted'));
               }
-              options?.signal?.addEventListener('abort', () => {
-                reject(new Error('Operation aborted'));
-              });
-              // Intentionally do not resolve immediately to simulate lag
+              options?.signal?.addEventListener(
+                'abort',
+                () => {
+                  reject(new Error('Operation aborted'));
+                },
+                { once: true },
+              );
             }),
         ),
         listPrompts: vi.fn().mockResolvedValue({ prompts: [] }),
diff --git a/packages/core/src/tools/tools.ts b/packages/core/src/tools/tools.ts
index 6029ba6673..82a980aeef 100644
--- a/packages/core/src/tools/tools.ts
+++ b/packages/core/src/tools/tools.ts
@@ -242,7 +242,7 @@ export abstract class BaseToolInvocation<
         }
       };
 
-      abortSignal.addEventListener('abort', abortHandler);
+      abortSignal.addEventListener('abort', abortHandler, { once: true });
 
       timeoutId = setTimeout(() => {
         cleanup();
diff --git a/packages/core/src/utils/llm-edit-fixer.test.ts b/packages/core/src/utils/llm-edit-fixer.test.ts
index d4fc95e400..a1215428a1 100644
--- a/packages/core/src/utils/llm-edit-fixer.test.ts
+++ b/packages/core/src/utils/llm-edit-fixer.test.ts
@@ -350,9 +350,13 @@ describe('FixLLMEditWithInstruction', () => {
           if (abortSignal?.aborted) {
             return reject(new DOMException('Aborted', 'AbortError'));
           }
-          abortSignal?.addEventListener('abort', () => {
-            reject(new DOMException('Aborted', 'AbortError'));
-          });
+          abortSignal?.addEventListener(
+            'abort',
+            () => {
+              reject(new DOMException('Aborted', 'AbortError'));
+            },
+            { once: true },
+          );
         }),
     );