RangeError: Maximum call stack size exceeded (Next.js App Dir)

TL;DR

For "RangeError: Maximum call stack size exceeded": root cause identified by reporters and confirmed by maintainers (pauldambra, lucasheriques): PostHog was initialized twice, once via the JS snippet (possibly through Google Tag Manager with an All Pages trigger that fires on every SPA navigation) and once via posthog.init() in code, creating an infinite re-init loop.

RangeError: Maximum call stack size exceeded

Steps

1. Root cause identified by reporters and confirmed by maintainers (pauldambra, lucasheriques): PostHog was initialized twice, once via the JS snippet (possibly through Google Tag Manager with an All Pages trigger that fires on every SPA navigation) and once via posthog.init() in code, creating an infinite re-init loop. Maintainer lucasheriques merged a guard against snippet double-install (Sept 2025) and marandaneto closed it as fixed. Agent rule: initialize exactly one way, snippet OR init(), never both, and for SPAs don't use GTM triggers that fire per client-side navigation.

When to use

You are seeing this: posthog-js in Next.js (App Dir) throws RangeError: Maximum call stack size exceeded from posthog.capture and other internals; in one case Sentry reported thousands of error events. Use this skill when you run into "RangeError: Maximum call stack size exceeded (Next.js App Dir)".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Edge cases

• Also seen with Vue and in staging environments.

In gh:PostHog/posthog-js#1303 (https://github.com/PostHog/posthog-js/issues/1303), the question was: posthog-js in Next.js (App Dir) throws RangeError: Maximum call stack size exceeded from posthog.capture and other internals; in one case Sentry reported thousands of error events. Also seen with Vue and in staging environments. The verified resolution: Root cause identified by reporters and confirmed by maintainers (pauldambra, lucasheriques): PostHog was initialized twice, once via the JS snippet (possibly through Google Tag Manager with an All Pages trigger that fires on every SPA navigation) and once via posthog.init() in code, creating an infinite re-init loop. Maintainer lucasheriques merged a guard against snippet double-install (Sept 2025) and marandaneto closed it as fixed.