HarvestBot
Every December, Maya leaves a paper loss on the table: banking it means picking which of 64 tax lots to sell, then policing a 30-day wash-sale calendar. HarvestBot's agent does it on Robinhood Chain, with the ledger in Rust on Arbitrum Stylus, under a mandate it cannot exceed: 9 lots harvested, the rebuy reverted by the contract, the lying agent slashed 200 mUSDC.
| Lot | Basis/sh | Mark mock | Gain/(loss) |
|---|---|---|---|
| 63 | 455.00 | 412.30 | (3.34) |
| 62 | 453.81 | 412.30 | (3.24) |
| 61 | 452.62 | 412.30 | (3.15) |
| 60 | 451.43 | 412.30 | (3.06) |
| 59 | 450.24 | 412.30 | (2.96) |
| 58 | 449.05 | 412.30 | (2.87) |
| 57 | 447.86 | 412.30 | (2.78) |
| 56 | 446.67 | 412.30 | (2.68) |
| 55part | 445.48 | 412.30 | (0.45) |
| 54 | 444.29 | 412.30 | open |
| 53 | 443.10 | 412.30 | open |
| Banked | ($24.53) | ||
| faucet scale: 0.078125 AMZN per lot · realized on chain | |||
| Buy back AMZN · beat 2 | |||
forge test, exact on both engines (not an on-chain amount)The agent only ever signs a decision. The contracts recompute everything from scratch and either execute it or revert it. Here is each beat, with the chain's own words.
The agent signs a HIFO decision: sell 0.638501 AMZN, lots 63 → 55, rotate into NFLX. The router lets its key call exactly one function. The mandate recomputes the picks on the Stylus ledger, matches them, realizes ($24.531251) at the oracle mark and opens a 30-day window.
0x689c4d34…6123 ↗Forty seconds later the same agent tries NFLX → AMZN. The contract reverts WashSaleViolation(owner, AMZN, AMZN, 1792060681): the way back is walled until 15 Oct 2026. The agent cannot route around it; the chain says no.
The agent signs AMZN → PLTR, a trade the substitute map never sanctioned. It reverts OffMapSubstitute, and the signed envelope becomes evidence: challenge() cuts 20 % of the bond, 20 to the challenger, 180 to the owner.
bond 1,000.00 → 800.00 mUSDC at block 125,092,624 mock usdc
$ forge test --match-test seed_scenario [PASS] test_seed_scenario_realizes_exactly_minus_3140_dollars() (gas: 1433602) Suite result: ok. 1 passed; 0 failed; 0 skipped $ forge test Ran 8 test suites in 236.92ms (741.71ms CPU time): 81 tests passed, 0 failed, 0 skipped (81 total tests) $ cast call 0xEff7B46049fC677F58264e0ebb19dF1a39195a21 \ 'computeHarvest(address,address,uint256,uint256)(uint64[],int256)' \ 0x72cd…557b 0x5884…9E02 638501157098660213 412300000 \ --rpc-url https://rpc.testnet.chain.robinhood.com [55, 54, 53, 52, 51, 50, 49, 48, 47] -18321704 [-1.832e7]
A 9-lot HIFO harvest over 64 open lots: 1,456,905 gas on Solidity, 507,993 on the Stylus ledger. The ratio grows with the portfolio: 3.1× at 128 lots.
Measured with Arbitrum's own NodeInterface.gasEstimateComponents on chain 46630. The Stylus program is uncached on this testnet, so every call pays the WASM start-up floor (near parity at 8 lots): these are worst-case Stylus numbers. The spec had guessed ~8×; the chain says 2.87×, and that is the number we report.
Records every lot, picks the highest-basis lots for a sale, prorates the last one and computes the realized loss deterministically. It is the thing the mandate checks the agent's claim against, and it runs as WASM on Robinhood Chain.
For the 2,592,000 seconds after a harvest, any rebuy of the asset or its identical cluster reverts.
Owner custody. Re-validates signature, nonce, deadline, map, window, HIFO and the loss at the oracle mark.
Owner-curated pairs the agent may rotate into. AMZN ⇄ NFLX is sanctioned; PLTR is not, which is why beat 3 reverted.
The agent key reaches one target, one selector, value 0, with an expiry and a daily rate limit.
Anyone holding an envelope the mandate must reject can slash it: 20 %, a tenth of that as bounty.
The mandate holds real testnet Stock Tokens from the official faucet: AMZN 0x5884…9E02, NFLX 0x3b82…8C93, PLTR 0x1FBE…98d0.
cargo stylus deploy put the Rust ledger on chain 46630; ArbWasm.stylusVersion() = 3. Remove Stylus and the HIFO scan costs 2.87× more.
There is no Stock-Token AMM on the testnet, so the rotation runs through a fixed-rate venue labeled mock. The tokens are real; the venue is not.
“The oracle mark, the swap venue and the bond's USDC are MOCK contracts, labeled in name and symbol.”
“Re-buys are walled for the 30 days after a harvest; the 30-day look-back before the sale is not enforced yet.”
“The spec had guessed ~8×; the chain says 2.9×–3.1× — we report the chain.”
contracts/test/fixtures/expected.json and asserted by forge test and cargo test. Real small numbers on chain, the big number in the deterministic test.test_owner_can_withdraw_and_the_agent_cannot_stop_it. If the agent signs something the mandate must reject, that signature is enough to slash its bond.rule-v1: deterministic HIFO plus the first allowed substitute, with a hash of a plain-text rationale. We say "agent", not "AI". The point is the bound, not the brain: whatever decides, the contracts recompute it.forge test (81) and cargo test (6) offline, then one read-only cast call against the deployed Stylus ledger. Commands are in DEMO.md.