SpendAuth

SpendAuth lets you pay operators directly on-chain without a credit card or account. Sign an EIP-712 typed data message with your wallet, attach it to the request, and the operator claims payment after serving inference.

How it works

1. Sign: Create an EIP-712 SpendAuth payload with your wallet
2. Send: Attach the signature as X-Payment-Signature header
3. Authorize: The gateway verifies the signature and calls authorizeSpend on-chain
4. Serve: The operator processes your inference request
5. Claim: The operator calls claimPayment to receive funds

Request format

curl -X POST "https://router.tangle.tools/v1/chat/completions" \
  -H "Content-Type: application/json" \
  -H "X-Payment-Signature: {
    \"commitment\": \"0xabc...\",
    \"serviceId\": \"1\",
    \"jobIndex\": 0,
    \"amount\": \"1000000\",
    \"operator\": \"0x70997970...\",
    \"nonce\": \"42\",
    \"expiry\": \"1712793600\",
    \"signature\": \"0xff...\"
  }" \
  -d '{"model": "llama-3.1-70b", "messages": [...]}'

Security

• EIP-712 signatures: Cryptographically verified against the signing address
• Nonce replay protection: Each nonce can only be used once per commitment (in-memory + Redis store)
• On-chain verification: The ShieldedCredits contract validates authorization and deducts balance
• Expiry: SpendAuth payloads have a timestamp-based expiry

Rate limits

SpendAuth requests get a generous 120 req/min limit per commitment since every request is paid.

On-chain contracts

SpendAuth uses the ShieldedCredits contract deployed on the Tangle network. The contract handles:

• Balance management (deposit, authorize, claim)
• Authorization verification (EIP-712 signature recovery)
• Payment settlement (operator claims after serving)

The operator-side settlement logic is implemented in tangle-inference-core, a shared Rust crate used by the LLM Inference Blueprint and other inference Blueprints.