> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neuro-tech.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Neuro architecture

> Understand the roles of your application, the Agent API, Neurons, and trust services

Your application connects to the **Agent API**, an HTTPS interface exposed by the Neuron that hosts its account. The Neuron coordinates the enabled identity, contract, token, payment, and messaging services.

```mermaid theme={null}
flowchart LR
  UI[Browser or mobile UI] --> Backend[Your backend]
  Backend --> API[Agent API]
  Service[Backend service] --> API
  API --> Neuron[Neuron]
  Neuron --> Objects[Accounts, identities, contracts, tokens, wallets]
  Objects --> Ledger[Neuro-Ledger history]
  Neuron <--> Peers[Other trusted services]
```

## Application responsibilities

Your application manages credentials, requests, user review, returned identifiers, and business logic. The Neuron executes the operations exposed through the API. Its provider controls enabled capabilities and trust relationships.

For browser applications, keep privileged credentials in your backend. The [application architecture guide](/get-started/choose-integration) and [application guide](/get-started/first-application) show this arrangement.

## Objects and their dependencies

A contract signature relates a Legal Identity to a role in an agreement. A token refers to its creation contract and may have a state machine. A payment has its own transaction outcome. These are related objects with distinct lifecycles.

Read the [object model](/concepts/object-model) to decide which identifiers and states to persist. Do not infer completed business activity from HTTP success alone.

## Trust across domains

Different participants can belong to different Neurons. Cross-domain interactions depend on the configured trust services and permissions. The [trust and federation concepts](/concepts/trust-and-federation) explain what this means for applications.

Continue with [your first API request](/neuron-api/quickstart) or [choose a build task](/build/overview).