Largest planets in science fiction

Does anyone know any really large planets in science fiction? Must be over 250,000 km in diameter. In Real Life, planets cannot become much larger than that because the immense mass and pressure in the core would start a nuclear fusion, which means that it would become a star. Also Internet would be highly impractical there due to unbearable latency.

The largest known exoplanet in reality is approximately 6.9 times the radius of Jupiter. It’s also a potential brown dwarf candidate.

It’s called HD 100546-b. It’s 341 light years away.

In sci fi? You'd want to start with a Ring world at least. You can upgrade to the solid Dyson Sphere from there, since they're popular enough as well. Both concepts tend to be about 1 AU radius.

Golden era fiction assumed that planets of all known sizes could support life (usually not as we know it, but sometimes as we know it as well). Aliens from Jupiter was just something that we assumed back then.

Then there's the matrioska brain idea, which itself is probably at least the size of Jupiter and layered enough to be much larger, where the internal simulated world is potentially as large as our galaxy.

So the "largest" ends up being quite a debatable point, where you have to define what metric you're using and what counts as a "planet".