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

# Writz Protocol documentation

> Guides, architecture, security and developer references for Writz, a lending protocol on Stellar backed by native BTC.

Writz is a lending protocol on Stellar backed by native BTC. A Bitcoin Script holds the collateral on Bitcoin itself rather than a company, and it never becomes a wrapped token. Borrow USDC against it, repay on your own schedule, and recover your Bitcoin even if Writz disappears. Live on Stellar testnet.

> [!WARNING]
>
> Writz is on testnet only. The contracts are not audited yet. Never send real BTC, real USDC or a wallet that holds real funds to the testnet app.

## Start here

> [card] [What is Writz?](https://docs.writz.xyz/introduction/what-is-writz.md)
>
> The short version, and why it was not possible before.

> [card] [How Writz works](https://docs.writz.xyz/introduction/how-writz-works.md)
>
> A loan from deposit to release, in plain language.

> [card] [Try the testnet app](https://docs.writz.xyz/guides/start-here.md)
>
> What you need and the order to set it up, with free test coins.

## Use the app

> [card] [Borrow USDC against BTC](https://docs.writz.xyz/guides/borrow.md)
>
> Lock test BTC on signet and draw test USDC on Stellar.

> [card] [Repay and release your BTC](https://docs.writz.xyz/guides/repay-and-release.md)
>
> Pay back the loan and take your collateral back.

> [card] [Lend USDC](https://docs.writz.xyz/guides/lend.md)
>
> Supply USDC to the pool and earn the interest borrowers pay.

## Build on Writz

> [card] [Integration guide](https://docs.writz.xyz/developers/integrate.md)
>
> Prove a Bitcoin transaction from your Soroban contract or your app.

> [card] [Bitcoin SPV SDK](https://docs.writz.xyz/developers/spv-sdk.md)
>
> The `verify_transaction` reference: signature, errors and the proof route.

> [card] [Contract reference](https://docs.writz.xyz/developers/contract-reference.md)
>
> The public functions of the Writz contracts.

> [card] [For AI agents](https://docs.writz.xyz/developers/for-ai-agents.md)
>
> Contract IDs, signatures and verified examples in a compact format.

## Understand the design

> [card] [Technical architecture](https://docs.writz.xyz/architecture/technical-overview.md)
>
> How the Bitcoin script, the light client and the lending contract fit together.

> [card] [Security model](https://docs.writz.xyz/security/security-model.md)
>
> What the protocol protects against, and what it assumes.

> [card] [SPV vs wrapped Bitcoin](https://docs.writz.xyz/security/spv-vs-wrapped.md)
>
> Where a light client differs from bridges, and where it shares their risks.

> [card] [Research](https://docs.writz.xyz/research/spv-implementations.md)
>
> The studies behind the design: SPV, oracles, rates and liquidation.


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