fix(settings): Defer sentry app form mount until data loads

[priscilawebdev]

The Sentry App edit page mounted useScrapsForm before the app data had finished loading, so the form's internal state was initialized from empty/default values. When the data arrived the form re-rendered, but TanStack Form does not pick up new defaultValues after init — so the rendered values lagged behind the real
data, briefly flashing (e.g. the Alert Rule Action switch flicking from off to on when opening an integration URL directly) and risking a save that overwrote
real values with empty ones. TanStack Form's defaultValues are reactive — when the real data arrived the form picked up the new defaults and re-rendered, which
is exactly what produced the visible flicker (e.g. the Alert Rule Action switch flipping from off to on when opening an integration URL directly) and risked a
save that overwrote real values with empty ones if the user interacted before the update landed.

Extract the form into a SentryApplicationForm child that the parent only mounts once the app query resolves (or for the new-app route), so useScrapsForm is initialized with the real values on its first render. Tokens are still prefetched in parallel from the parent so the credentials/tokens panel is ready by the time the form mounts.

Before

Screen.Recording.2026-05-08.at.11.30.34.mov

After

Screen.Recording.2026-05-08.at.11.31.09.mov

[linear-code]

DE-970

[github-actions]

📊 Type Coverage Diff

✅ No new type safety issues introduced. Coverage: 93.47%

[priscilawebdev]

bugbot run

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✅ Bugbot reviewed your changes and found no new issues!

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^{Reviewed by Cursor Bugbot for commit 39a785e. Configure here.}

[TkDodo]

When the data arrived the form re-rendered, but TanStack Form does not pick up new defaultValues after init — so the rendered values lagged behind the real data, briefly flashing (e.g. the Alert Rule Action switch flicking from off to on when opening an integration URL directly) and risking a save that overwrote real values with empty ones.

This assessment is wrong. The flickering happens precisely because TanStack Form does pick up defaultValues after init - they have reactive defaultValues.

So yes, the fix is to not render the form if you don’t want to init the form with fallback values that later update themselves, but the statement is not correct (I guess it’s AI?)

[priscilawebdev]

When the data arrived the form re-rendered, but TanStack Form does not pick up new defaultValues after init — so the rendered values lagged behind the real data, briefly flashing (e.g. the Alert Rule Action switch flicking from off to on when opening an integration URL directly) and risking a save that overwrote real values with empty ones.

This assessment is wrong. The flickering happens precisely because TanStack Form does pick up defaultValues after init - they have reactive defaultValues.

So yes, the fix is to not render the form if you don’t want to init the form with fallback values that later update themselves, but the statement is not correct (I guess it’s AI?)

yes it was auto-generated. Thanks for reading and correcting 🙏 I updated the description