Right, thanks for digging up the history. In this case, you’ll have to make some assumptions. If you know you’ll only interface with newer wallets (u128 support was rolled out May 4, 2022), then you can use the u128 bound.
If this is not certain, then you should go with the lower bound from the i64. But even if you sent too many cycles to an old wallet, in the worst case the wallet could render the cycles inaccessible until you upgrade the wallet wasm. The cycles could not get lost (unless you find a bug in the replica).
Thank you. Just wanted to confirm. So, if the cycles wallet supports the i128 API, it’s all good. I just created a wallet with dfx v0.12.1 so I assume it will use the latest WASM, so I should be covered.