Bug: error tracking auto-capture never installs on first app launch due to race condition with remote config

[ptrkstr]

Version

3.48.3

Steps to Reproduce

1. Integrate the PostHog iOS SDK with error tracking auto-capture enabled in the dashboard.
2. Install the app on a device or simulator for the first time (no prior disk-cached remote config).
3. Trigger a crash or unhandled exception on first launch.
4. Relaunch the app, observe that the crash is not reported in PostHog Error Tracking.
5. Trigger the same crash on the second launch, observe that it is reported this time.

Expected Result

The error tracking auto-capture integration installs on the first launch, even if the remote config network fetch has not yet completed, by subscribing to remote config updates and performing a late install, matching the behaviour of the session replay integration.

Actual Result

The error tracking integration is installed synchronously during setup(), before the async remote config fetch completes. On first launch, no disk-cached config exists, so isAutocaptureExceptionsEnabled() returns false and the integration throws. When the fetch eventually completes, nothing re-installs the integration. Any crash on first launch is permanently lost.

Code References (courtesy of claude code)

1. PostHogSDK.setup() calls installIntegrations() synchronously (PostHogSDK.swift#L157)

2. installIntegrations() iterates integrations and calls install() (PostHogSDK.swift#L1898-L1933) — if install() throws, the integration is skipped and never retried.

3. Error tracking install() gates on remote config (PostHogErrorTrackingAutoCaptureIntegration.swift#L22-L25):

   if postHog.remoteConfig?.isAutocaptureExceptionsEnabled() == false {
       throw InternalPostHogError(description: "Error tracking auto capture integration disabled in remote config.")
   }

   At this point, only the disk-cached config has been loaded via preloadErrorTrackingConfig() (PostHogRemoteConfig.swift#L489-L496).

4. Remote config fetch is async — preloadRemoteConfig() dispatches to dispatchQueue.async (PostHogRemoteConfig.swift#L105), so it completes after installIntegrations() has already run and failed.

5. processErrorTrackingConfig() updates the flag but doesn't re-install (PostHogRemoteConfig.swift#L467-L487) — it sets autoCaptureExceptions and caches to disk, but there's no callback to PostHogSDK to retry the integration.

6. onRemoteConfigLoaded is only subscribed to by session replay (PostHogReplayIntegration.swift#L153), not by error tracking. Session replay has installReplayIntegration() (PostHogSDK.swift#L1939-L1952) as a late-install path — error tracking has no equivalent.

7. Even if installIntegrations() were called again, the guard at the top would block it (PostHogSDK.swift#L1899):

   guard installedIntegrations.isEmpty else {
       hedgeLog("Integrations already installed.")
       return
   }

   Other integrations (lifecycle, replay, surveys) installed successfully, so the array is non-empty.

Suggested Fix

Add an installErrorTrackingIntegration() method (analogous to installReplayIntegration()) and subscribe to onRemoteConfigLoaded in PostHogSDK to call it when the config flips to enabled.

[marandaneto]

@ioannisj i think for error tracking we'd need to default isAutocaptureExceptionsEnabled to true if remote config isnt returned yet, or we should install the integration and capture the crash but do not send it if isAutocaptureExceptionsEnabled=false on restart from the remote config
wdyt?

[marandaneto]

@ptrkstr thanks for reporting, will check

[ptrkstr]

No worries @marandaneto, added some code references. Would you know if my account would need to have some flag added to it so I could still test error reporting in the mean time (via the project settings toggle)? can now see it

[ioannisj]

@ioannisj i think for error tracking we'd need to default isAutocaptureExceptionsEnabled to true if remote config isnt returned yet, or we should install the integration and capture the crash but do not send it if isAutocaptureExceptionsEnabled=false on restart from the remote config wdyt?

I think what we need is a general solution on reacting to remote config changes and install/uninstall integrations as needed when config becomes available. We already do something similar with replay plugins here so we can kind of replicate that?

Downside is that integrations in general (like plugins) will do this on config changes:

• installed for a short period, then uninstalled (config flipped to false)
• short delay to get installed (config flipped to true)

For error tracking, however, second case may be a bit problematic cause it means there's a change we miss app start crashes when config flips from false/unknown to true?

[marandaneto]

yeah i think for error tracking this is a problem, theres a period of time that its not installed and the app may crash so we'll always miss the crash
thats why i suggested to default to true if remote config isnt loaded yet
wdyt?

[ioannisj]

Yeah, I think that sounds reasonable. I'll work on this soon, maybe abstract this behavior in PostHogIntegration for future uses as well

[ptrkstr]

@marandaneto @ioannisj wanted to put another iOS error reporting issue on your radar here: PostHog/posthog#55770
It fixes an issue of source code not being uploaded alongside the dSYM.