[macjayz]

Summary

Adds the RPC that AI agents actually pay for to the reliability study: Pocket Network's Agentic Portal sells Ethereum, Base and Arbitrum JSON-RPC over x402 at $0.005 a call (USDC on Base, quoted 1 Nov 2026). In x402scan's top services, blockchain RPC is the only paid data that can be cross-checked, so this is where Heightproof's verification applies.

• @heightproof/web3: createHeightproofRpcClient accepts a fetchImpl for calls to rpcUrl, so a priced endpoint can be called through a paying fetch.
• scripts/study/paid.ts: wraps an x402 client with two spending caps.
  • x402 refuses any single payment above $0.01.
  • The wrapper stops paying for the rest of the UTC day once STUDY_PAID_DAILY_BUDGET_USD is spent.
  • Only settled or successful payments count toward the budget.
• Collector:
  • Paid endpoints are off unless STUDY_X402_PAYER_KEY is set.
  • They run every STUDY_PAID_EVERY_TICKS ticks (default 80, about every 20 minutes) and are never used as verification peers, so nothing else spends money.
  • Skipped ticks aren't recorded as provider failures.
• Compose: passes the new settings to the study service.

Cost at the defaults: about 72 rounds a day × ~6 calls × $0.005 ≈ $2.20 per chain, so about $6.50 a day for all three, with a hard cap of $8 a day.

OneSource was left out: it sells RPC through its own REST routes, not JSON-RPC.

Testing

• Tests: all workspace tests pass, including a new web3 test that fetchImpl replaces the global fetch for rpcUrl. Typecheck and lint are clean.
• Live against Pocket with an unfunded key:
  • the wrapper signs a payment and Pocket's facilitator rejects it (PAYMENT_INVALID)
  • nothing is counted against the budget
  • free endpoints pass straight through
  • the budget check blocks calls once the cap is reached
• Not tested: a settled payment, which needs a funded wallet.