The dep-only fix wasn't enough: better-auth's useSession (nanostores) can
re-emit on focus / store refresh, transitioning session.user.id through
undefined and back. Each transition re-fires the effect, which then calls
setTheme(session.user.theme) with the stale cached value and reverts the
user's selection.
Track "have we synced this tab session" with a ref. After the first
successful sync, no subsequent effect fire can revert.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
lorentz
f32403ee35