fix(session-replay-browser): skip bisect-retry for non-WAF 413 responses

Non-WAF (app-layer) 413s are rejected by the server at any payload size,
so bisecting and retrying wastes O(2N-1) network requests before every
event is individually dropped. Guard handlePayloadTooLargeResponse with
an isWaf check to immediately drop the batch for non-WAF 413s.

Update unit and integration tests to reflect the new non-WAF immediate-drop
behavior; WAF 413 bisection behavior is unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: lewgordon-amplitude

packages/session-replay-browser/src/track-destination.ts

@@ -385,6 +385,14 @@ export class SessionReplayTrackDestination implements AmplitudeSessionReplayTrac
     const source = isWaf ? 'WAF (compressed payload too large)' : 'server (event too large)';
     const totalSizeKB = Math.round(context.events.reduce((sum, e) => sum + e.length, 0) / KB_SIZE);
 
+    if (!isWaf) {
+      this.completeRequest({
+        context,
+        err: `Session replay event batch dropped: ${source} rejected payload (${context.events.length} events, ${totalSizeKB} KB) — not retrying non-WAF 413`,
+      });
+      return;
+    }
+
     if (context.events.length === 1) {
       this.completeRequest({
         context,

packages/session-replay-browser/test/integration.test.ts

@@ -247,7 +247,7 @@ describe('module level integration', () => {
       await runScheduleTimers();
       expect(fetch).toHaveBeenCalledTimes(1);
       // eslint-disable-next-line @typescript-eslint/unbound-method
-      expect(mockLoggerProvider.warn).toHaveBeenCalledWith(expect.stringMatching(/single event.*cannot split further/));
+      expect(mockLoggerProvider.warn).toHaveBeenCalledWith(expect.stringContaining('not retrying non-WAF 413'));
     });
     test('should handle retry for 500 error', async () => {
       const sessionReplay = new SessionReplay();

packages/session-replay-browser/test/track-destination.test.ts

@@ -585,13 +585,28 @@ describe('SessionReplayTrackDestination', () => {
       ...overrides,
     });
 
-    test('drops single event and logs error with size', () => {
+    test('drops non-WAF batch immediately without bisecting', () => {
       const trackDestination = new SessionReplayTrackDestination({ loggerProvider: mockLoggerProvider });
       const completeRequest = jest.spyOn(trackDestination, 'completeRequest').mockReturnValueOnce(undefined);
-      const context = baseContext();
+      const sendEventsList = jest.spyOn(trackDestination, 'sendEventsList');
+      const context = baseContext({ events: ['event1', 'event2'] });
 
       trackDestination.handlePayloadTooLargeResponse(context, false);
 
+      expect(completeRequest).toHaveBeenCalledWith({
+        context,
+        err: expect.stringContaining('not retrying non-WAF 413'),
+      });
+      expect(sendEventsList).not.toHaveBeenCalled();
+    });
+
+    test('drops single WAF event and logs error with size', () => {
+      const trackDestination = new SessionReplayTrackDestination({ loggerProvider: mockLoggerProvider });
+      const completeRequest = jest.spyOn(trackDestination, 'completeRequest').mockReturnValueOnce(undefined);
+      const context = baseContext();
+
+      trackDestination.handlePayloadTooLargeResponse(context, true);
+
       expect(completeRequest).toHaveBeenCalledWith({
         context,
         err: expect.stringContaining('single event'),
@@ -611,15 +626,15 @@ describe('SessionReplayTrackDestination', () => {
       expect(errArg).toContain('WAF');
     });
 
-    test('bisects multi-event batch and re-enqueues both halves', () => {
+    test('bisects multi-event WAF batch and re-enqueues both halves', () => {
       const trackDestination = new SessionReplayTrackDestination({ loggerProvider: mockLoggerProvider });
       const capturedOnCompletes: Array<() => Promise<void>> = [];
       jest.spyOn(trackDestination, 'sendEventsList').mockImplementation((dest) => {
         capturedOnCompletes.push(dest.onComplete);
       });
       const context = baseContext({ events: ['event1', 'event2', 'event3', 'event4'] });
 
-      trackDestination.handlePayloadTooLargeResponse(context, false);
+      trackDestination.handlePayloadTooLargeResponse(context, true);
 
       expect((trackDestination.sendEventsList as jest.Mock).mock.calls).toHaveLength(2);
       expect((trackDestination.sendEventsList as jest.Mock).mock.calls[0][0].events).toEqual(['event1', 'event2']);
@@ -630,12 +645,12 @@ describe('SessionReplayTrackDestination', () => {
       void Promise.all(capturedOnCompletes.map((fn) => fn()));
     });
 
-    test('logs warn with event count and size when bisecting', () => {
+    test('logs warn with event count and size when bisecting WAF batch', () => {
       const trackDestination = new SessionReplayTrackDestination({ loggerProvider: mockLoggerProvider });
       jest.spyOn(trackDestination, 'sendEventsList').mockReturnValue(undefined);
       const context = baseContext({ events: ['event1', 'event2'] });
 
-      trackDestination.handlePayloadTooLargeResponse(context, false);
+      trackDestination.handlePayloadTooLargeResponse(context, true);
 
       // eslint-disable-next-line @typescript-eslint/unbound-method
       expect(mockLoggerProvider.warn).toHaveBeenCalledWith(expect.stringContaining('splitting'));