縛
Bound
Its rules live in a contract, not in a promise. What the seal forbids, the spirit cannot do, whoever asks.
封幽霊 · ROBINHOOD CHAIN · FIG. 001
Bound inference · Robinhood Chain · Research edition
YUREI
A spirit, bound by contract.
Yurei is a research program for accountable AI on Robinhood Chain: a model that reasons off-chain, answers onchain, and can be proven wrong by anyone. What its answers may do is fixed by a seal it cannot amend.
Contract: 0x7371c8a737ef6e3948ff70d7c915cb754ed5af4d
The legend
In the old stories, a yūrei is a soul that could not rest.
幽霊 means a faint spirit. In Japanese folklore it is the soul of someone who could not move on: a white burial robe, long dark hair, no feet, drifting at the edge of the lamplight.
What keeps a yūrei out is an ofuda, a strip of paper written in red ink and pressed to a door or a beam. The spirit can be anywhere. It cannot cross the seal.
Yurei is that idea, rebuilt on Robinhood Chain: something with real power that lives onchain, held by rules written in code instead of promises.
Abstract
Verify the answer. Don't recompute the mind.
Machine intelligence that acts with real money has two bad options today. It can run on a server you cannot inspect, which asks you to trust whoever runs it. Or it can run entirely inside smart contracts, which makes every step verifiable but costs orders of magnitude more than the answer is worth.
Yurei takes a third path, borrowed from how optimistic rollups secure their own state. A committed model runs off-chain. Each answer is posted onchain together with a cryptographic commitment to the computation that produced it. Anyone may challenge an answer within a fixed window. A dispute is narrowed, by bisection, to a single step of the model's arithmetic, and only that one step is re-executed onchain to decide who lied.
An honest answer costs one ordinary transaction. A dishonest one costs its author a bond. Around both sits the seal: a policy contract, fixed at creation, that decides what any answer is allowed to do, however persuasive the answer is.
Optimistic inferenceInteractive fraud proofsFixed-point determinismPolicy contractsRobinhood Chain
The mechanism
From a question to an action, in five stages.
Each stage leaves a record on Robinhood Chain. Nothing moves until the record says it may.
- 01 / Request問
The question is escrowed
A requester submits a prompt with a fee and an upper bound on cost. The seal is consulted first: a request the policy would never allow to act is refused before any work is done.
in prompt, fee, bounds
out request id, escrow - 02 / Inference考
The spirit answers off-chain
A bonded executor runs the committed model, whose weights are fixed by hash, in deterministic fixed-point arithmetic. It posts the answer and a Merkle root over the execution trace.
in request, model hash
out answer, trace root, bond - 03 / Challenge疑
Anyone may doubt it
For a fixed window, any watcher who recomputes a different result can challenge by posting a bond of their own. Silence is the normal case, and silence is cheap.
in answer, counter-claim
out dispute, or nothing - 04 / Proof証
One step decides the truth
The two parties bisect the trace until they disagree about a single operation. The chain re-executes that one operation, compares it to both claims, and slashes the bond of whoever was wrong.
in disputed trace
out one-step verdict, slashed bond - 05 / Action封
The seal releases, or holds
After the window closes, the answer becomes final. If it calls for an action, such as a payment or a contract call, the seal checks it against limits written at creation. Inside them, it executes. Outside them, nothing happens.
in final answer
out action, or refusal
Stage 04, simulated
Watch a lie get caught.
An executor posts an answer with one corrupted step hidden somewhere in its trace. A challenger disagrees. Each round, both sides reveal the state at the midpoint of the disputed range, and half of it is ruled out.
step 0execution tracestep 63
Round0 / 6
Disputed range0 to 63
Steps left64
Re-executed onchain0 steps
ready · trace committed · root 0x7a1f…c93e · press Run a dispute
Simulation. A real trace has millions of steps, but rounds grow with the logarithm of its length: a million steps settle in about 20 rounds, and the chain still re-executes exactly one.
Trusted server
Cheap, opaqueFast and inexpensive, but every answer is a claim you cannot check. The operator can change the model, the output or the rules without telling you.
Full onchain inference
Verifiable, impracticalEvery multiplication runs in a contract. Correct by construction, but a short reply can cost more than most people would ever pay for it.
Yurei
Verifiable when it mattersAnswers cost about one transaction. Proof is paid for only when someone disputes, and only for the single step in question.
The seal
Three marks are written on the seal.
On an old ofuda the ink does the work. On Yurei, the contract does. These are the rules the seal is being written to keep.
証
Witnessed
Every answer is posted on Robinhood Chain with a commitment to how it was made. Anyone can read the record and anyone can contest it.
封限
Limited
Answers act only inside limits you can check before you trust them. Outside them, the seal holds and the spirit stops.
封Specification
The seal, in numbers.
Design targets for the first edition. Values marked Target will change as the contracts are written and measured. When a number is measured on mainnet, it is marked Fixed and linked to its receipt.
| Model | Small open-weight language modelWeights committed by keccak256 hash; any change means a new spirit.Target |
|---|---|
| Arithmetic | Deterministic fixed-point, quantizedRemoves floating-point drift so two honest executors always agree.Target |
| Commitment | Merkle root over the execution tracePosted with every answer; the basis for any challenge.Target |
| Challenge window | 30 minutesLong enough for watchers, short enough to be useful.Target |
| Dispute game | Interactive bisection to one stepAbout log₂ of the trace length in rounds.Target |
| Cost per answer | One ordinary transactionCents on Robinhood Chain, plus the requester's fee.Target |
| Seal | Immutable policy contractPer-action caps, daily limits, allowed recipients and contracts, expiry. No owner can widen it later.Target |
| Settlement | USDGFees, bonds and payouts in a dollar stablecoin.Fixed |
| Network | Robinhood Chain, chain ID 4663An Arbitrum Orbit chain, itself secured by fraud proofs.Fixed |
Open questions
What the research still has to answer.
A seal is only as strong as its weakest assumption. These are ours, stated plainly.
Determinism
Can two machines always agree?
Fraud proofs only work if honest executors produce identical traces. Quantized fixed-point arithmetic should make that true; it has to be shown across hardware and implementations.
Liveness
Who is watching?
An optimistic system is secure if at least one honest watcher checks each answer. Yurei needs watchers to be cheap to run and rewarded for catching lies.
Data availability
Where does the trace live?
Only the root is posted onchain. The full trace must stay retrievable for the length of the window, or a challenger cannot build a proof.
One-step cost
How expensive is the hardest step?
The single operation re-executed onchain must fit in one block. The model's layers are being shaped so that no step is too large to prove.
The register
Where the summoning stands.
Shrines keep a register of every charm they issue. This is ours: what exists, what is still being written, and the one place the official token address will appear.
SpiritYureiBeing summoned. Follow X for each step.Summoning
SealSmart contractsBeing written. Source will be public before anything goes live.Writing
ChainRobinhood ChainChain ID 4663Live
Token$YUREILaunched. The official address will appear here and on X, nowhere else.
0x7371c8a737ef6e3948ff70d7c915cb754ed5af4dLiveRegister updated 20 Oct 2026
The spirit can be anywhere. It cannot cross the seal.
Follow the summoning as the contracts are written, tested and opened to challenge.