# FP256 deployment record

The FP256 Yul object (release one, the 256-bit float) is deployed with
CREATE2 through Arachnid's deterministic-deployment proxy, exactly as FP127
is (see `FP127.md` for the procedure, the gas note and the trust model).
Machine-readable copy: `FP256.json`.

| | |
|---|---|
| address | `0x628b8dfC82954983a9E8E22056ffc767B4a26077` |
| chain | Ethereum Sepolia, chainId 11155111 |
| CREATE2 proxy | `0x4e59b44847b379578588920cA78FbF26c0B4956C` |
| salt | `0x4650323536207631000000000000000000000000000000000000000000000000` (ASCII `FP256 v1`, right-padded) |
| init code hash | `0xdb79b4b16f216a803757f7c89520212b48ce54eb5cf54a431465890f6ac80e42` |
| runtime keccak256 | `0xcf5c047227240c591f5d213aeef3bfd90343707c06d9a13d3ca857c579de83a1` (8,037 bytes) |
| source | `contracts/src/fp256/FP256.yul`, generated from `FP256.yul.src` |
| compiler | solc 0.8.24+commit.e11b9ed9, language Yul, optimizer on, 200 runs, evm shanghai |
| deployment tx | [`0xa2167e71…08d666`](https://sepolia.etherscan.io/tx/0xa2167e718174cc9ffad7f4d0c883a5b03c1bc2d338fe87c7f6d05955ec08d666), block 11,922,179, 12,641,159 gas, 2026-10-15 |
| source commit | `df5155d` (master after PR #71) |
| verification | [Sourcify](https://repo.sourcify.dev/11155111/0x628b8dfC82954983a9E8E22056ffc767B4a26077), [Blockscout](https://eth-sepolia.blockscout.com/address/0x628b8dfC82954983a9E8E22056ffc767B4a26077?tab=contract); Etherscan unverified (no Yul support) |
| Sourcify match | `match` on creation and runtime bytecode |
| smoke test | `make smoke-fp256-sepolia`: every committed vector across 19 ops matches the live contract |

Release one (2026-10-15): 19 ops; add, sub, mul, div, sqrt, the comparisons
and the conversions exact to the 237-bit grid; exp, ln and pow on FP127's
2^-192 kernels (146, 149 and 123 bits at worst over the vectors).

## Reproduce the bytecode

```sh
make build
FP_LIB=fp256 uv run scripts/fp127/stdjson.py check   # solc standard-json (language Yul) == Foundry artifact
make predict-fp256                                   # the address above, from the artifact alone
FP_LIB=fp256 uv run scripts/fp127/stdjson.py onchain https://ethereum-sepolia-rpc.publicnode.com 0x628b8dfC82954983a9E8E22056ffc767B4a26077
```