"We support Flutter and React Native" is easy to put on a landing page. Keeping it true is a discipline, and it's one most cross-platform tools quietly fail at.
How parity actually rots
The usual version of "we support both" means: we built it for the one we use daily, and there's a second SDK trailing a release or two behind, missing a few features nobody got around to porting. It happens gradually and almost innocently. You ship a feature to your primary SDK, you fully intend to bring it to the other one, and three releases later the second SDK is a museum piece — technically present, practically second-class.
The developer on the neglected platform feels it immediately. They read your docs, try the thing, and find out the thing isn't there for them. That's a worse experience than never claiming support at all.
The rule I hold
A feature isn't shipped until it's in both SDKs. Not "shipped to Flutter, React Native coming soon." Both, or it isn't done.
That's a tax I pay every single release, and I pay it on purpose, because the alternative is a promise that decays. If the Flutter and React Native SDKs are ever more than a hair apart, the claim on the homepage stops being true, and I'd rather carry the cost than carry a lie.
What parity is not
It is not identical APIs. Flutter and React Native are genuinely different worlds — different languages, different idioms, different package ecosystems, different release mechanics. Forcing the React Native SDK to look like Dart, or the Flutter SDK to look like TypeScript, just to claim surface-level sameness, produces something that feels foreign in both.
Idiomatic beats identical. A Dart developer should feel like the SDK was written by someone who loves Dart. A TypeScript developer should feel exactly the same way about theirs. Parity is about capability and timing — the same power available at the same time — not about the two SDKs reading like carbon copies.
The hard part
Underneath, the two platforms diverge most exactly where it matters most to me: code push. The runtimes are different enough that the machinery below the surface can't be the same. Keeping the developer experience consistent while the internals differ — so that pushing an update feels the same whether you're on Flutter or React Native, even though what's happening underneath is not — is the part I care most about getting right.
That's the real work of parity. Not a checkbox on a comparison table. A tax, paid every release, so that whichever ecosystem you're in, the platform underneath treats you like a first-class citizen.