> For the complete documentation index, see [llms.txt](https://docs.syndromics.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.syndromics.xyz/architecture/overview.md).

# System overview

Syndromics is a small set of immutable contracts on Robinhood Chain surrounded by open-source services that anyone can run. The contracts hold the state and enforce the rules; the services make the protocol usable.

```mermaid
flowchart LR
  subgraph Users
    B[Borrower wallet<br/>Robinhood Wallet or any EVM<br/>4337 or 7702]
    L[Lender wallet]
    K[Keepers and liquidators]
  end

  subgraph OffChain[Off-chain services]
    FE[Next.js front-end]
    REL[Offer relayer API<br/>EIP-712 order book]
    IDX[Indexer<br/>Ponder or Envio]
    KYC[KYC provider<br/>issues EAS attestations]
    NOTIF[Alerts and keeper bots]
  end

  subgraph Chain[Robinhood Chain, 4663]
    CORE[LoanSettlement<br/>immutable core]
    ELIG[EligibilityRegistry]
    ORA[OracleRouter<br/>Chainlink Feeds and Streams<br/>Sequencer Uptime]
    AUC[LiquidationAuction]
    REFI[RefinanceAuction]
    POS[PositionNFT, ERC-721]
    PARK[IdleCapitalAdapter<br/>Morpho Blue USDG vault]
    PARAM[ParamController<br/>timelocked multisig]
    ST[(Stock Tokens<br/>ERC-20 and ERC-8056)]
    USDG[(USDG)]
    CL[(Chainlink)]
    MB[(Morpho Blue)]
  end

  B --> FE --> REL
  L --> FE
  FE --> IDX
  KYC --> ELIG
  REL --> CORE
  B --> CORE
  K --> AUC
  CORE --> ELIG
  CORE --> ORA --> CL
  CORE --> POS
  CORE --> ST
  CORE --> USDG
  CORE --> PARK --> MB
  CORE --> AUC
  CORE --> REFI
  PARAM --> CORE
  IDX --> CORE
  NOTIF --> IDX
```

## Layers

### On-chain

| Contract              | One-line responsibility                                                              |
| --------------------- | ------------------------------------------------------------------------------------ |
| `LoanSettlement`      | Verify offers, escrow collateral, disburse principal, track loans and slices, repay  |
| `OfferVerifier`       | EIP-712 hashing, ECDSA and EIP-1271 recovery, nonce bitmaps, partial-fill accounting |
| `EligibilityRegistry` | Attestation lookups, role checks, jurisdiction rules, expiry                         |
| `OracleRouter`        | Session-aware price with staleness, pause, multiplier and sequencer-uptime guards    |
| `LiquidationAuction`  | Dutch auction of collateral, in-kind option, penalty split                           |
| `RefinanceAuction`    | Rising-rate rollover auction at maturity                                             |
| `PositionNFT`         | One ERC-721 per lender slice, transfer-gated by eligibility                          |
| `IdleCapitalAdapter`  | Deposit and withdraw lender balances in a whitelisted Morpho vault                   |
| `ParamController`     | All tunable parameters behind a timelocked multisig; every change emits an event     |
| `FeeCollector`        | Origination, interest-share, penalty and refinance fees                              |

Details and interfaces are in [Smart contracts](/architecture/smart-contracts.md).

### Off-chain

| Service     | One-line responsibility                                                                  |
| ----------- | ---------------------------------------------------------------------------------------- |
| Relayer     | Public order book of signed offers and requests; validation; matching suggestions        |
| Indexer     | Event-sourced view of every loan, slice, auction and parameter for the explorer and bots |
| Keepers     | Alerts, auction kick-off, refinance acceptance, idle-capital rebalancing                 |
| KYC service | Identity, sanctions and residency checks; issues attestations; holds PII off-chain       |
| Front-end   | Borrower and lender dashboards, loan explorer, risk page, governance log                 |

Details are in [Off-chain services](/architecture/off-chain-services.md).

## Trust boundaries

* **The contracts trust Chainlink** for prices, within the guards in `OracleRouter`.
* **The contracts trust the attestation issuers** listed in `ParamController` for eligibility, and nothing else about a user.
* **The contracts trust the timelocked multisig** for parameter changes only. It cannot move funds, upgrade code or pause repayment.
* **Nobody trusts the relayer.** Every offer it serves is re-verified on-chain at settlement. A malicious relayer can withhold offers but cannot forge or alter them.
* **Nobody trusts the front-end.** It is a convenience over public data and public contracts.

## Deployment posture

* Core contracts are non-upgradeable. A new version is a new deployment; existing loans run to maturity on the old one.
* Parameters are the only mutable state outside loan data, and every change is timelocked and logged.
* Emergency pause covers new loans and liquidations only. Repayment and post-repayment withdrawal are never pausable.


---

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