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

# Protocol Architecture

Vayyl divides responsibility so no backend service needs custody of user funds or proof witnesses.

```mermaid
flowchart TB
    subgraph Wallet
      K[Shielded keys and notes]
      G[Proof worker]
      B[Encrypted backup]
    end

    subgraph Services
      I[Indexer]
      R[Relayers]
      Q[Oracle and keepers]
    end

    subgraph Soroban
      P[Asset pools]
      V[Proof verifiers]
      A[Association sets]
      X[Application adapters]
    end

    subgraph Stellar
      T[Native and issued assets]
    end

    K --> G
    K --> B
    I --> K
    G --> R
    R --> P
    Q --> X
    P --> V
    P --> A
    P <--> X
    P <--> T
```

## Trust boundaries

* **Wallet:** owns spending keys, note plaintext, witness selection, and proof generation.
* **Indexer:** serves public ledger-derived state. A dishonest response can delay or confuse a wallet, but must not authorize an invalid spend.
* **Relayer:** submits a prepared action and pays network fees. Proof-bound parameters prevent it from changing the recipient or value transition.
* **Contracts:** enforce roots, nullifiers, proofs, authorization, and asset movement.
* **Oracle and keeper:** provide public inputs and liveness for conditional applications; they must not gain unilateral control over private value.

## Shared state, modular applications

Payments and applications should use the same commitment and nullifier layer. Application contracts remain modular, but value returns to standard Vayyl notes. This creates a single wallet recovery model and avoids fragmenting privacy across unrelated pools.


---

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