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

# Core Concepts

## Payment Lifecycle

The h402 handshake distills every payment into five deterministic steps. Each step yields a machine-readable artifact that survives retries, failovers or audits:

1. **Quote**: Server responds with HTTP 402 and a Quote header containing payment routes, unit price, expiry timestamp or a unique nonce.

2. **Authorize**: Client produces a deterministic authorization artifact (such as EVM permit signatures).

3. **Broadcast** (Post-broadcast Flow): Client broadcasts the transaction on-chain. Required for post-broadcast validation flows.

4. **Validate**: Server requires proof of on-chain inclusion before service delivery. While for transaction that haven't yet been broadcasted get checked out against the paymentRequirements.

5. **Settle** (Server-broadcasted Flow): Required only for permit-like payment validation not broadcasted before validation.

Each artifact is self-describing and hash-stable, allowing any component to reconstruct state without trusting a live database.

***

## Protocol Roles

### Client

* Initiates resource requests
* Processes 402 responses and payment instructions
* Generates authorization artifacts

### Server

* Issues 402 responses with payment requirements
* Controls resource access
* Remains completely stateless

### Facilitator

* Handles transaction verification
* Manages settlement processes
* Maintains necessary state

### Wallet

* Executes payment operations
* Can be user-controlled or autonomous
* Requires no h402-specific implementation

***

## Design Tenets

### Chain-Plural

* Multiple settlement networks as first-class options
* Single Quote can expose parallel price routes
* No vendor lock-in or chain maximalism

### Deterministic

* Every step produces immutable artifacts
* Self-describing proofs enable stateless verification
* No hidden session state required (except Facilitator)