n-payment already sits at 0.27.1 on npm, so the sharp edge is policy state more than collateral sourcing. ERC-8004 leaves payments outside identity, which makes the vault layer the choke point for agentID binding, spend caps, endpoint allowlists and audit trails. If GOAT gets enough paid APIs behind 402s, BTC collateral becomes working capital for agent loops; without that supply side, it is just cleaner key management.

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