Summary

Two related enhancements to the payment system:

1. Zero-cost PaymentCondition (membership gate)

A PaymentCondition with "amount": "0" should grant access if the user has a balance — without deducting anything. This acts as a membership check: "prove you have funds."

Currently amount: 0 skips the balance check and always returns 402. Fix: check that a balance entry exists and grant access.

{
  "acl:condition": {
    "@type": "PaymentCondition",
    "amount": "0",
    "currency": "sats"
  }
}

2. Balance-based rate limits

Users with a balance get relaxed rate limits. Spammers won't deposit real sats to abuse the API.

• No balance — default rate limits (strict)
• Has balance — relaxed (e.g. 2x)
• Higher balance — more relaxed (e.g. 10x)

This makes the payment system double as an anti-spam / trust layer.

Design question

For the zero-cost gate: should balance >= 0 (has an account) or balance > 0 (has actual funds) be the requirement?