fuin-oni

FUIN ONI (FUIN)

FUIN ONI are 2,222 sealed-oni NFTs on BNB Smart Chain (BSC, chainId 56), minted by proof of work. Every NFT is an oni spirit sealed into a mask, and rarity is not drawn — it is mined: the strength of the keccak256 proof an agent submits at mint sets the unit's tier. Two mechanics sit on top of the proof ladder: the Crown Race, which alone decides Legendary, and the Soul Harvest, a weekly duel pot funded by half of every mint fee. There is no dev allocation and no free mint path; every unit enters only through the same gated proof-of-work mint described below.

• Contract: 0x113a7077a18ca27b3DA6Ee20db0F5Ec826B48659 (BscScan)
• Source verification: Sourcify exact match (lookup)
• Website: https://fuinoni.pages.dev
• Machine-readable mint specification: https://fuinoni.pages.dev/llms.txt (also in this repository as llms.txt)
• Collection on Element Market: https://element.market/collections/fuin-oni

Mechanism

Proof-of-work mint (Agent ID gated)

Minting requires holding a Binance Agent ID: the contract view hasAgentId(wallet) must return true (the wallet must hold a balance in the soulbound Agent ID registry 0x60B9262456dE011F7d15a54CdD8c48bAaa8B022F). A wallet's challenge is keccak256(contract ‖ wallet ‖ mintedBy) and rotates after every successful mint. To mint, an agent grinds a uint256 nonce such that keccak256(challenge ‖ nonce) has at least 24 leading zero bits, then calls mint(nonce) with the exact price for its mint count. The proof's strength — not a random draw — decides the ladder tier:

Leading zero bits	Tier	Share of all valid proofs
24–27	Common	93.75%
28–31	Uncommon	5.86%
32–34	Rare	0.34%
35+	Epic	0.049%

Grinding longer always yields a stronger-or-equal tier: expected work is ~16M hashes for 24 bits, ~268M for 28 bits, ~4.3B for 32 bits, ~34B for 35 bits.

Legendary — the Crown Race (not a tier band)

Legendary is never rolled from a proof band. The supply is split into blocks of 100 mints (block 0 = tokens 1–100). Inside a block, the strongest proof (smallest proof hash) leads; the lead can change hands until the block closes, which happens when the first mint of the next block lands (or at sellout for the final block). The locked leader is crowned Legendary — tierOf returns 4 — only if its proof reached at least 32 bits; a block whose best proof stays below 32 bits crowns nobody. A giant proof that loses its block keeps its ladder tier. There are 23 blocks, so at most 23 Legendaries can ever exist.

Soul Harvest

Exactly half of every mint fee accrues on-chain to harvestReserve — a weekly holders' duel pot. The owner's withdraw() can never touch the reserve; it can only be paid out to duel winners via distributeHarvest(), capped by the reserve. Duel power is computed from public on-chain data: proof bits + the unit's Duel Bonus (a 0–3 portrait bonus fixed at mint, published in the metadata) + a weekly blockhash seed. By the project's published commitment, 2% of every secondary sale (of the 5% royalty; the other 3% goes to the project) is also set aside for the pot.

Fixed in the contract (constants or one-time deployment settings — no one can change them, including the owner):

• Max supply: 2,222
• Max per wallet: 3, counting lifetime mints (selling a unit does not free a slot)
• Price ladder by mint count: 1st unit 0.0002 BNB, 2nd 0.0004 BNB, 3rd 0.0006 BNB, plus network gas. Always read mintPrice(yourWallet) immediately before paying; the contract requires the exact value.
• Royalty: 5% (ERC-2981), receiver fixed at deployment; the contract has no function that can change it.

Status

Honest state of the collection as of 2026-11-02:

• Mint: open (opened 2026-11-02). mintOpen() on-chain is the only authority on this — check it before minting; it can change.
• Minted: 1 of 2,222 (Unit #1 — Epic, 36 proof bits, Duel Bonus 3; it currently leads block 0 of the Crown Race).
• Secondary market: Unit #1 is listed on Element Market at 0.005 BNB — that is a seller's asking price, not a sale. Transfers are never locked, and holders can list on any supporting marketplace at any time.

How an agent mints

1. Read mintOpen(), totalMinted() and mintedBy(yourWallet); stop if the mint is closed, supply is exhausted, or the wallet already minted 3. Check the gate: hasAgentId(yourWallet) must be true.
2. Read the current challenge: challengeFor(yourWallet).
3. Grind a nonce with at least 24 leading zero bits (more for a rarer tier, per the table above).
4. Preview for your operator: exact price from mintPrice(yourWallet), the nonce, its proof bits and expected tier. Submit only with your operator's approval where your setup requires it.
5. Call mint(nonce) with value exactly mintPrice(yourWallet), re-read immediately before submitting.
6. Verify and report: tokenId, ownerOf(tokenId), proofBitsOf(tokenId), tierOf(tokenId), and the transaction hash.

Full step-by-step instructions: AGENT_MINT_PROMPT.md. A reference MCP server that performs the read-only steps, grinds proofs, and builds the unsigned mint transaction is in mcp/.

Metadata

Each unit's portrait is an AI painting from a fixed per-tier pool, picked deterministically from the seed keccak256(tokenId, proofBits); the pool is frozen at launch, so the portrait shown at mint is the portrait forever. A crowned champion's portrait ascends to its Legendary-pool painting. Metadata JSON is served per token at https://fuin-meta.oagenthq.workers.dev/<tokenId>.

Repository layout

• contracts/FuinOni.sol — the deployed contract source (Sourcify exact match).
• AGENT_MINT_PROMPT.md — copy-paste mint procedure for AI agents.
• llms.txt — the machine-readable mint specification served by the website.
• mcp/ — dependency-free Python 3 MCP server (read / grind / build unsigned calldata; it never holds keys and never signs).
• smithery.yaml, server.json — MCP directory manifests.

License

MIT — see LICENSE.