---
name: btc-anchor
description: >
  Anchor a Merkle root (root_hex) to Bitcoin testnet or mainnet using OP_RETURN via bitcoin-cli.
  Emits PROOF.json + tx metadata with plan/apply/rollback and verification.
  Consumes merkle-forest ROOT.txt (or explicit ROOT_HEX). Triggers: 'btc anchor',
  'anchor root on bitcoin', 'op_return', 'taproot proof', 'bitcoin-cli'.
version: 1.0.0
---

# BTC Anchor (OP_RETURN via bitcoin-cli)

This skill anchors a **root_hex** on Bitcoin by creating a transaction
with an **OP_RETURN** output containing the root bytes.

## Requirements
- `bitcoin-cli` connected to a synced node (mainnet/testnet/signet)
- Wallet loaded + funded (UTXOs)
- Network parameters set (v1 uses `bitcoin-cli -testnet` / `-signet` flags)

## Quick Start

```bash
cd ~/.claude/skills/btc-anchor

export ROOT_FILE="$HOME/.claude/skills/merkle-forest/outputs/runs/<run>/ROOT.txt"
export BTC_NETWORK="testnet"          # mainnet|testnet|signet
export BTC_FEE_RATE="5"              # sat/vB (rough)
export OP_RETURN_PREFIX="VM"         # 2-byte ascii prefix

./scripts/00_preflight.sh
./scripts/10_plan.sh

export DRY_RUN=0
./scripts/11_apply.sh

./scripts/90_verify.sh
./scripts/99_report.sh
```

## Inputs

| Parameter | Required | Default | Description |
|---|---:|---|---|
| ROOT_FILE | No | (empty) | ROOT.txt path |
| ROOT_HEX | No | (empty) | Explicit root hex (overrides ROOT_FILE) |
| BTC_NETWORK | No | testnet | mainnet/testnet/signet |
| BTC_FEE_RATE | No | 5 | sat/vB (passed to walletcreatefundedpsbt) |
| OP_RETURN_PREFIX | No | VM | ASCII prefix (helps identify payloads) |
| DRY_RUN | No | 1 | Apply refuses unless DRY_RUN=0 |
| REQUIRE_CONFIRM | No | 1 | Require confirmation phrase |
| CONFIRM_PHRASE | No | I UNDERSTAND THIS WILL BROADCAST A BITCOIN TX | Safety phrase |

## Outputs
`outputs/runs/<label>_<timestamp>/`
- root_hex.txt
- op_return_hex.txt
- txid.txt
- rawtx.hex
- PROOF.json
- status_matrix.json
- audit_report.md

## Notes
- Payload format: `<prefix-as-hex><root-bytes>` truncated to fit OP_RETURN.
- v1 uses OP_RETURN and the node wallet RPCs: create raw tx → fund → sign → send.