diff --git a/extensions/google-meet/src/oauth.test.ts b/extensions/google-meet/src/oauth.test.ts
index 9904e717ebd..7580e3f1d2d 100644
--- a/extensions/google-meet/src/oauth.test.ts
+++ b/extensions/google-meet/src/oauth.test.ts
@@ -64,7 +64,7 @@ describe("Google Meet OAuth", () => {
     expect(tokens.tokenType).toBe("Bearer");
     expect(Number.isFinite(tokens.expiresAt)).toBe(true);
     expect(tokens.expiresAt).toBeGreaterThan(Date.now());
-    const body = fetchMock.mock.calls[0]?.[1]?.body;
+    const body = fetchMock.mock.calls.at(0)?.[1]?.body;
     expect(body).toBeInstanceOf(URLSearchParams);
     const params = body as URLSearchParams;
     expect(params.get("grant_type")).toBe("refresh_token");
diff --git a/extensions/google/image-generation-provider.test.ts b/extensions/google/image-generation-provider.test.ts
index 563f34b2aa9..07a23026854 100644
--- a/extensions/google/image-generation-provider.test.ts
+++ b/extensions/google/image-generation-provider.test.ts
@@ -52,7 +52,7 @@ function fetchRequest(fetchMock: ReturnType<typeof vi.fn>): {
   method?: string;
   url: string;
 } {
-  const [url, init] = fetchMock.mock.calls[0] as [string, RequestInit | undefined];
+  const [url, init] = fetchMock.mock.calls.at(0) as [string, RequestInit | undefined];
   expect(typeof url).toBe("string");
   if (!init) {
     throw new Error("Expected fetch init");
diff --git a/extensions/google/video-generation-provider.test.ts b/extensions/google/video-generation-provider.test.ts
index 2dbc6fd2fc6..22905042e16 100644
--- a/extensions/google/video-generation-provider.test.ts
+++ b/extensions/google/video-generation-provider.test.ts
@@ -287,7 +287,7 @@ describe("google video generation provider", () => {
       durationSeconds: 3,
     });
 
-    const [{ downloadPath }] = downloadMock.mock.calls[0] ?? [{}];
+    const [{ downloadPath }] = downloadMock.mock.calls.at(0) ?? [{}];
     const downloadBaseName = path.basename(String(downloadPath));
     expect(downloadBaseName).toContain("video-1.mp4");
     expect(downloadBaseName).toMatch(/\.part$/);
diff --git a/extensions/gradium/tts.test.ts b/extensions/gradium/tts.test.ts
index 847ade1e0fa..96648d8a994 100644
--- a/extensions/gradium/tts.test.ts
+++ b/extensions/gradium/tts.test.ts
@@ -119,7 +119,7 @@ describe("gradium tts diagnostics", () => {
     });
 
     expect(fetchMock).toHaveBeenCalledOnce();
-    const [url, init] = fetchMock.mock.calls[0] as [string, RequestInit];
+    const [url, init] = fetchMock.mock.calls.at(0) as [string, RequestInit];
     expect(url).toBe("https://api.gradium.ai/api/post/speech/tts");
     expect(init.method).toBe("POST");
     const headers = new Headers(init.headers);
diff --git a/extensions/imessage/src/actions.test.ts b/extensions/imessage/src/actions.test.ts
index 7b9332ca545..7ff44ce3850 100644
--- a/extensions/imessage/src/actions.test.ts
+++ b/extensions/imessage/src/actions.test.ts
@@ -203,7 +203,7 @@ describe("imessage message actions", () => {
     ).rejects.toThrow(/imsg private API bridge/);
 
     expect(loggerMock.warn).toHaveBeenCalledTimes(1);
-    const warnArg = String(loggerMock.warn.mock.calls[0][0]);
+    const warnArg = String(loggerMock.warn.mock.calls.at(0)?.[0]);
     expect(warnArg).toMatch(/iMessage react blocked: private API bridge unavailable/);
     expect(warnArg).toMatch(/imsg launch/);
     expect(runtimeMock.sendReaction).not.toHaveBeenCalled();
diff --git a/extensions/irc/src/inbound.behavior.test.ts b/extensions/irc/src/inbound.behavior.test.ts
index 480992cce88..980169fbf2f 100644
--- a/extensions/irc/src/inbound.behavior.test.ts
+++ b/extensions/irc/src/inbound.behavior.test.ts
@@ -196,7 +196,7 @@ describe("irc inbound behavior", () => {
 
     const assembledRequest = (
       coreRuntime.channel.turn.runAssembled as unknown as { mock: { calls: unknown[][] } }
-    ).mock.calls[0]?.[0] as { replyPipeline?: unknown } | undefined;
+    ).mock.calls.at(0)?.[0] as { replyPipeline?: unknown } | undefined;
     expect(assembledRequest?.replyPipeline).toEqual({});
   });
 });
diff --git a/extensions/line/src/monitor.lifecycle.test.ts b/extensions/line/src/monitor.lifecycle.test.ts
index 9a5bf04ba8e..e1820de5969 100644
--- a/extensions/line/src/monitor.lifecycle.test.ts
+++ b/extensions/line/src/monitor.lifecycle.test.ts
@@ -51,7 +51,7 @@ type WebhookRegistration = {
 };
 
 function requireWebhookRegistration(): WebhookRegistration {
-  const registration = registerWebhookTargetWithPluginRouteMock.mock.calls[0]?.[0] as
+  const registration = registerWebhookTargetWithPluginRouteMock.mock.calls.at(0)?.[0] as
     | WebhookRegistration
     | undefined;
   if (!registration) {
diff --git a/extensions/line/src/send.test.ts b/extensions/line/src/send.test.ts
index 4a235e8e835..e809489dbb1 100644
--- a/extensions/line/src/send.test.ts
+++ b/extensions/line/src/send.test.ts
@@ -418,7 +418,7 @@ describe("LINE send helpers", () => {
     );
 
     expect(pushMessageMock).toHaveBeenCalledTimes(1);
-    const firstCall = pushMessageMock.mock.calls[0] as [
+    const firstCall = pushMessageMock.mock.calls.at(0) as [
       { messages: Array<{ quickReply?: { items: unknown[] } }> },
     ];
     expect(firstCall[0].messages[0].quickReply?.items).toHaveLength(13);
diff --git a/extensions/line/src/signature.test.ts b/extensions/line/src/signature.test.ts
index 7fefeaae9f1..05f40dbaf79 100644
--- a/extensions/line/src/signature.test.ts
+++ b/extensions/line/src/signature.test.ts
@@ -26,7 +26,7 @@ describe("validateLineSignature", () => {
     expect(validateLineSignature(body, "short", secret)).toBe(false);
     expect(spy).toHaveBeenCalledTimes(1);
 
-    const [left, right] = spy.mock.calls[0] ?? [];
+    const [left, right] = spy.mock.calls.at(0) ?? [];
     expect(left).toBeInstanceOf(Buffer);
     expect(right).toBeInstanceOf(Buffer);
     expect(left?.byteLength).toBe(right?.byteLength);
diff --git a/extensions/litellm/image-generation-provider.test.ts b/extensions/litellm/image-generation-provider.test.ts
index 9d637b0facd..e15a5d7e942 100644
--- a/extensions/litellm/image-generation-provider.test.ts
+++ b/extensions/litellm/image-generation-provider.test.ts
@@ -193,7 +193,7 @@ describe("litellm image generation provider", () => {
     });
 
     expect(mockObjectArg(postJsonRequestMock).url).toBe("http://localhost:4000/images/edits");
-    const call = postJsonRequestMock.mock.calls[0][0] as { body: { images: unknown[] } };
+    const call = postJsonRequestMock.mock.calls.at(0)?.[0] as { body: { images: unknown[] } };
     expect(call.body.images).toHaveLength(1);
   });