Reducer side effects trigger Redux errors #3 and #9 on the features page

[sentry]

Sentry: FLAGSMITH-FRONTEND-58P (also
58Q and
58R — same root cause)

Three Sentry issues, one underlying bug: a reducer performing side effects.

Sentry	Redux code	Meaning
58P	#3	"You may not call store.getState() while the reducer is executing."
58Q	#3	same
58R	#9	"Reducers may not dispatch actions."

Impact

1 event each, 1 user. All three fired 2026-08-03T07:23Z — same session, same
release 1785435093938, Firefox 152, production.
URL: https://app.flagsmith.com/project/12461/environment/DVMZZNZ6SVofMfkffi8rn5/features

Why grouped

Calling getState() inside a reducer (#3) and dispatching from inside a reducer
(#9) are the same class of defect: a reducer that isn't a pure function of
(state, action). All three landed in the same minute on the same page, so
they're near-certainly one code path.

Note on stack traces

There are no in-app frames — all frames sit inside
./node_modules/redux/dist/redux.mjs, because Redux throws from its own
internals once the invariant is broken. Reproducing on the features page with a
non-minified dev build will name the offending reducer (the dev build gives the
full message instead of a minified error code).

Caveat

Only 58P carries the Sentry↔GitHub link for this issue. 58Q and 58R are
triaged but not individually linked; consider sentry issue merge if you want
them consolidated in Sentry.

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Slack alert · filed by the sentry-triage skill