ReplayType incorrectly being identified as Session instead of Buffer

[minori-fh]

What React Native libraries do you use?

React Native without Frameworks

Are you using sentry.io or on-premise?

sentry.io (SaS)

Are you using any other error monitoring solution alongside Sentry?

Yes

Other Error Monitoring Solution Name

No response

@sentry/react-native SDK Version

7.4.0

How does your development environment look like?

⬇  Place the `npx react-native@latest info` output here. ⬇

Sentry.init()

{
      dsn: env.SENTRY_DSN,
      release: env.APP_VERSION_NAME,
      dist: env.APP_VERSION_CODE,
      sendDefaultPii: true,
      tracesSampleRate: 0.1,
      profilesSampleRate: 0,
      replaysSessionSampleRate: 0,
      replaysOnErrorSampleRate: 0.05,
      integrations: [
        Sentry.mobileReplayIntegration({
          maskAllText: false,
          maskAllImages: false,
          maskAllVectors: false,
        }),
        Sentry.appStartIntegration(),
        Sentry.reactNativeTracingIntegration(),
        this.navigationIntegration,
        featureFlagsIntegration(),
      ],
      enableAutoSessionTracking: true,
      sessionTrackingIntervalMillis: 1000,
      enableCaptureFailedRequests: true,
      enableUserInteractionTracing: true,
      attachScreenshot: false,
      debug: false,
      enableAppStartTracking: true,
      enableNativeFramesTracking: true,
      enableStallTracking: true,
    }

Steps to Reproduce

Capture session replay with init above.

Expected Result

Session replays without errors should not be coming in without errors. If they are they should be of replayType: buffer.

Actual Result

Session replays are coming in without any errors and are of replayType: Session.

[linear-code]

RN-551

[alwx]

Hey, @minori-fh and thanks for reporting this!

This is actually an expected behavior of how mobile session replay works under the hood. Here's what's happening: when you set replaysOnErrorSampleRate: 0.05, 5% of app sessions start a background buffer recording (keeping the last ~60s in memory). When an error occurs in one of those sessions, the buffer is getting flushed and the replay is being sent. After that flush the native SDKs transition to session-mode recording and continue capturing, and that's the reason why you see replayType: Session on subsequent replay segments.

So the replays you're seeing tagged as Session are continuations of error-triggered replays, not independently sampled session replays. The error is linked to the initial segment but the recording continues in session mode after the flush. Your replaysSessionSampleRate: 0 is working correctly — no replays are being independently started as full session recordings.

If you'd like the recording to stop after the error is captured rather than continue as a session, that would need to be a feature in the native SDKs (sentry-cocoa / sentry-java) since we basically just pass those options to them. We can look into whether that's something worth adding but in the meantime, you can filter these in Sentry's UI by looking at replays that have associated errors.