diff --git a/docker-compose.yml b/docker-compose.yml
index 100d9fb..abb1f19 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -96,6 +96,10 @@ services:
       HEIGHTPROOF_ENDPOINT: http://api:8080
       DATABASE_URL: postgres://heightproof:heightproof@postgres:5432/heightproof
       STUDY_STATE: /data/state.json
+      # Optional: x402-paid RPC providers (USDC on Base). Off unless a funded key is set.
+      STUDY_X402_PAYER_KEY: ${STUDY_X402_PAYER_KEY:-}
+      STUDY_PAID_DAILY_BUDGET_USD: ${STUDY_PAID_DAILY_BUDGET_USD:-8}
+      STUDY_PAID_EVERY_TICKS: ${STUDY_PAID_EVERY_TICKS:-80}
     volumes:
       - heightproof-study:/data
     depends_on:
diff --git a/packages/web3/src/index.test.ts b/packages/web3/src/index.test.ts
index 5a1de82..363aabf 100644
--- a/packages/web3/src/index.test.ts
+++ b/packages/web3/src/index.test.ts
@@ -149,6 +149,25 @@ describe("result capture", () => {
     vi.unstubAllGlobals();
   });
 
+  it("calls the rpc url through fetchImpl when one is given", async () => {
+    captured.length = 0;
+    const globalFetch = vi.fn();
+    vi.stubGlobal("fetch", globalFetch);
+    const payingFetch = vi.fn(async () => ({
+      ok: true,
+      status: 200,
+      json: async () => ({ jsonrpc: "2.0", result: "0x10" })
+    })) as unknown as typeof fetch;
+
+    const client = createHeightproofRpcClient({ ...baseOptions, rpcUrl: "https://paid.example/v1/eth", fetchImpl: payingFetch });
+
+    expect(await client.request({ method: "eth_blockNumber", params: [] })).toBe("0x10");
+    expect(payingFetch).toHaveBeenCalledWith("https://paid.example/v1/eth", expect.objectContaining({ method: "POST" }));
+    expect(globalFetch).not.toHaveBeenCalled();
+
+    vi.unstubAllGlobals();
+  });
+
   it("never lets the rpc url reach the captured event", async () => {
     captured.length = 0;
     const fetchMock = vi.fn(async () => ({
diff --git a/packages/web3/src/index.ts b/packages/web3/src/index.ts
index 64a474b..ea4ed81 100644
--- a/packages/web3/src/index.ts
+++ b/packages/web3/src/index.ts
@@ -47,6 +47,11 @@ export type HeightproofWeb3Options = {
    * requests against the endpoints you name.
    */
   verify?: VerificationOptions;
+  /**
+   * Fetch used for calls to `rpcUrl`. Pass one that pays for priced endpoints, such as a fetch
+   * wrapped with x402. Defaults to the global fetch.
+   */
+  fetchImpl?: typeof fetch;
 };
 
 /**
@@ -87,7 +92,7 @@ export function createHeightproofRpcClient(options: HeightproofWeb3Options) {
   return {
     async request(args: JsonRpcRequest) {
       const outcome = await recorder.record(args, async () => {
-        const response = await fetch(options.rpcUrl!, {
+        const response = await (options.fetchImpl ?? fetch)(options.rpcUrl!, {
           method: "POST",
           headers: { "content-type": "application/json" },
           body: JSON.stringify({
diff --git a/scripts/study/collect.ts b/scripts/study/collect.ts
index a502800..eb02af6 100644
--- a/scripts/study/collect.ts
+++ b/scripts/study/collect.ts
@@ -9,11 +9,16 @@
  *
  * The first run signs up a dedicated workspace and keeps its API key in STUDY_STATE, so restarts
  * keep writing to the same project.
+ *
+ * Paid endpoints (STUDY_PAID_ENDPOINTS, x402 per call) run only when STUDY_X402_PAYER_KEY is set,
+ * on every STUDY_PAID_EVERY_TICKS-th tick, within STUDY_PAID_DAILY_BUDGET_USD. They are never
+ * used to verify other endpoints, so verification never spends money on their behalf.
  */
 import { randomBytes } from "node:crypto";
 import { mkdir, readFile, writeFile } from "node:fs/promises";
 import { dirname } from "node:path";
 import { createHeightproofRpcClient } from "@heightproof/web3";
+import { createPaidBudget } from "./paid.js";
 
 type Chain = {
   chainId: number;
@@ -27,7 +32,7 @@ type Chain = {
   /** How far behind the head a log range ends, about 10 s, so a provider a block behind is not a mismatch. */
   logLag: number;
 };
-type Endpoint = { name: string; url: string; chain: string };
+type Endpoint = { name: string; url: string; chain: string; paid: boolean };
 type StudyState = { projectId: string; apiKey: string; startedAt: string };
 
 const CHAINS: Record<string, Chain> = {
@@ -67,6 +72,12 @@ const DEFAULT_ENDPOINTS =
   "arbitrum/drpc=https://arbitrum.drpc.org," +
   "arbitrum/blastapi=https://arbitrum-one.public.blastapi.io";
 
+// RPC sold per call to AI agents over x402. Pocket Network quoted $0.005 a call on 1 Nov 2026.
+const DEFAULT_PAID_ENDPOINTS =
+  "pocket=https://agent.pocket.network/v1/eth," +
+  "base/pocket=https://agent.pocket.network/v1/base," +
+  "arbitrum/pocket=https://agent.pocket.network/v1/arb-one";
+
 const api = process.env.HEIGHTPROOF_ENDPOINT ?? "http://localhost:8080";
 const statePath = process.env.STUDY_STATE ?? ".study/state.json";
 const intervalMs = Number(process.env.STUDY_INTERVAL_MS ?? 15_000);
@@ -74,14 +85,35 @@ const sampleRate = Number(process.env.STUDY_VERIFY_SAMPLE_RATE ?? 0.2);
 const callTimeoutMs = Number(process.env.STUDY_CALL_TIMEOUT_MS ?? 10_000);
 // Log queries return the most data by far, so they run on every Nth tick only.
 const logsEveryTicks = Number(process.env.STUDY_LOGS_EVERY_TICKS ?? 4);
-const endpoints: Endpoint[] = (process.env.STUDY_ENDPOINTS ?? DEFAULT_ENDPOINTS)
-  .split(",")
-  .map((entry) => {
-    const [label, ...url] = entry.trim().split("=");
-    const chain = label.includes("/") ? label.slice(0, label.indexOf("/")) : "ethereum";
-    if (!CHAINS[chain]) throw new Error(`unknown chain "${chain}" in STUDY_ENDPOINTS`);
-    return { name: label, url: url.join("="), chain };
-  });
+const payerKey = process.env.STUDY_X402_PAYER_KEY as `0x${string}` | undefined;
+const paidEveryTicks = Number(process.env.STUDY_PAID_EVERY_TICKS ?? 80);
+const paidPriceUsd = Number(process.env.STUDY_PAID_PRICE_USD ?? 0.005);
+const paidDailyBudgetUsd = Number(process.env.STUDY_PAID_DAILY_BUDGET_USD ?? 8);
+
+function parseEndpoints(list: string, paid: boolean): Endpoint[] {
+  return list
+    .split(",")
+    .filter((entry) => entry.trim())
+    .map((entry) => {
+      const [label, ...url] = entry.trim().split("=");
+      const chain = label.includes("/") ? label.slice(0, label.indexOf("/")) : "ethereum";
+      if (!CHAINS[chain]) throw new Error(`unknown chain "${chain}" in study endpoints`);
+      return { name: label, url: url.join("="), chain, paid };
+    });
+}
+
+const endpoints: Endpoint[] = [
+  ...parseEndpoints(process.env.STUDY_ENDPOINTS ?? DEFAULT_ENDPOINTS, false),
+  ...(payerKey ? parseEndpoints(process.env.STUDY_PAID_ENDPOINTS ?? DEFAULT_PAID_ENDPOINTS, true) : [])
+];
+const budget = payerKey
+  ? createPaidBudget({
+      payerKey,
+      paidUrls: endpoints.filter((e) => e.paid).map((e) => e.url),
+      priceUsd: paidPriceUsd,
+      dailyBudgetUsd: paidDailyBudgetUsd
+    })
+  : undefined;
 
 // Deterministic reads whose answers every honest provider must agree on at a given height.
 const WALLET = "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045";
@@ -120,6 +152,11 @@ const state = await loadOrCreateState();
 console.log(
   `study project ${state.projectId} (since ${state.startedAt}); ${endpoints.length} endpoints every ${intervalMs}ms, verify sample ${sampleRate}`
 );
+console.log(
+  budget
+    ? `paid endpoints on: every ${paidEveryTicks} ticks, $${paidPriceUsd}/call, budget $${paidDailyBudgetUsd}/day`
+    : "paid endpoints off (set STUDY_X402_PAYER_KEY to a Base key holding USDC)"
+);
 
 const clients = endpoints.map((endpoint) => ({
   endpoint,
@@ -128,17 +165,20 @@ const clients = endpoints.map((endpoint) => ({
     apiKey: state.apiKey,
     endpoint: api,
     rpcUrl: endpoint.url,
+    fetchImpl: endpoint.paid ? budget!.fetch : undefined,
     provider: endpoint.name,
     chainId: CHAINS[endpoint.chain].chainId,
     serviceName: "rpc-study",
     environment: "study",
     verify: {
       endpoints: endpoints
-        .filter((other) => other !== endpoint && other.chain === endpoint.chain)
+        .filter((other) => other !== endpoint && other.chain === endpoint.chain && !other.paid)
         .map((other) => ({ rpcUrl: other.url, provider: other.name })),
       sampleRate,
       maxCallsPerMinute: 20,
-      timeoutMs: callTimeoutMs
+      timeoutMs: callTimeoutMs,
+      // A paid endpoint is also asked for the head when verifying, so that call must pay too.
+      fetchImpl: endpoint.paid ? budget!.fetch : undefined
     }
   })
 }));
@@ -150,8 +190,14 @@ process.on("SIGINT", () => (stopping = true));
 const totals = new Map(endpoints.map((endpoint) => [endpoint.name, { ok: 0, failed: 0 }]));
 for (let tick = 1; !stopping; tick++) {
   const started = Date.now();
+  // A multiple of logsEveryTicks, so paid endpoints get the log query too.
+  const paidTick = tick % paidEveryTicks === 0;
   await Promise.all(
     clients.map(async ({ endpoint, client }) => {
+      // Skip, rather than fail, paid calls outside their ticks or past the budget, so they do
+      // not show up as provider failures in the report.
+      if (endpoint.paid && (!paidTick || budget!.exhausted())) return;
+
       const head = await withTimeout(
         client.request({ method: "eth_blockNumber", params: [] }),
         callTimeoutMs
@@ -173,7 +219,8 @@ for (let tick = 1; !stopping; tick++) {
 
   if (tick % 20 === 0) {
     const summary = [...totals].map(([name, t]) => `${name} ${t.ok}/${t.ok + t.failed}`).join("  ");
-    console.log(`${new Date().toISOString()} tick ${tick}  ok/total: ${summary}`);
+    const spend = budget ? `  x402 spent today $${budget.spentTodayUsd().toFixed(3)}` : "";
+    console.log(`${new Date().toISOString()} tick ${tick}  ok/total: ${summary}${spend}`);
   }
   await sleep(Math.max(0, intervalMs - (Date.now() - started)));
 }
diff --git a/scripts/study/paid.ts b/scripts/study/paid.ts
new file mode 100644
index 0000000..b85f959
--- /dev/null
+++ b/scripts/study/paid.ts
@@ -0,0 +1,67 @@
+/**
+ * Paying for priced RPC endpoints in the study: providers that sell JSON-RPC per call over x402
+ * (USDC on Base). Spending is capped twice: x402 refuses any single payment above
+ * MAX_PER_PAYMENT, and this wrapper stops paying for the rest of the UTC day once the daily
+ * budget is spent.
+ */
+import { privateKeyToAccount } from "viem/accounts";
+import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
+import { registerExactEvmScheme } from "@x402/evm/exact/client";
+
+const BASE_MAINNET = "eip155:8453";
+const BASE_USDC = "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913";
+/** $0.01 in USDC base units: no single study call should cost more. */
+const MAX_PER_PAYMENT = "10000";
+
+export type PaidBudget = {
+  fetch: typeof fetch;
+  /** True once today's budget cannot cover another call. */
+  exhausted(): boolean;
+  spentTodayUsd(): number;
+};
+
+export function createPaidBudget(options: {
+  payerKey: `0x${string}`;
+  paidUrls: string[];
+  priceUsd: number;
+  dailyBudgetUsd: number;
+}): PaidBudget {
+  const payments = new x402Client().setSpendControls({
+    allowedAssets: [{ network: BASE_MAINNET, asset: BASE_USDC, maxAmountPerPayment: MAX_PER_PAYMENT }]
+  });
+  registerExactEvmScheme(payments, { signer: privateKeyToAccount(options.payerKey) });
+  const paying = wrapFetchWithPayment(fetch, payments);
+  const paidUrls = new Set(options.paidUrls);
+
+  let day = utcDay();
+  let spent = 0;
+  const rollOver = () => {
+    if (utcDay() !== day) {
+      day = utcDay();
+      spent = 0;
+    }
+  };
+  const exhausted = () => {
+    rollOver();
+    return spent + options.priceUsd > options.dailyBudgetUsd;
+  };
+
+  const budgetFetch = (async (input: RequestInfo | URL, init?: RequestInit) => {
+    const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
+    if (!paidUrls.has(url)) return fetch(input, init);
+    if (exhausted()) throw new Error("x402 daily budget reached");
+
+    const response = await paying(input, init);
+    // A settled payment comes back with a payment-response header; a successful answer
+    // implies one too. Rejected payments (unfunded wallet, bad signature) cost nothing.
+    const settled = response.headers.has("payment-response") || response.headers.has("x-payment-response");
+    if (settled || response.ok) spent += options.priceUsd;
+    return response;
+  }) as typeof fetch;
+
+  return { fetch: budgetFetch, exhausted, spentTodayUsd: () => (rollOver(), spent) };
+}
+
+function utcDay() {
+  return new Date().toISOString().slice(0, 10);
+}