Recently, PayAI added Auto Top-Up to the merchant portal. Set a threshold once, approve once, and your x402 credit balance refills itself before it ever reaches zero — on Solana or Base, paid in USDC, with no action from you and no card on file.

Your agents run around the clock. Your credit balance shouldn't need a human watching it.

What We Shipped

  • Automatic credit refills on two chains. Auto Top-Up works on Solana and Base, both in USDC. Pick the chain your treasury already lives on.
  • You set the rules. Choose the balance that triggers a purchase and the dollar amount to buy each time. Both are editable whenever you want.
  • One approval, then it's hands-off. You sign a single on-chain approval from your own wallet. After that, purchases happen without you.
  • We pay the gas on every refill. You cover gas once, on the approval transaction. Every automatic purchase after that is submitted and paid for by PayAI.
  • We tell you before you need it. The dashboard now watches your burn rate and warns you when you're running low — an amber notice at about a week of runway, red at two days. Because one credit is exactly one settled x402 request, that estimate is arithmetic, not guesswork.
  • Off in one click, on-chain. Disabling Auto Top-Up stops purchases immediately and revokes the on-chain approval in the same action. No leftover permissions.
  • Guardrails you don't have to configure. A cap on how many refills can happen in a day, an automatic pause if something's wrong with your wallet or approval, and a purchase history that shows every automatic top-up alongside your manual ones.

Why running out of credits is a 3am problem

In PayAI, one credit is one settled request. That makes running out unmistakable: your balance hits zero, /settle starts returning insufficient_credits, and your agent traffic stops.

Nobody schedules that moment. Agentic traffic isn't a nine-to-five workload — it spikes when your customers' agents decide to work, which is frequently at 3am on a Saturday. The balance that looked comfortable on Friday is gone by the weekend, and the first thing that tells you is your own error logs.

We've watched merchants hit this repeatedly. Not because they were careless — because manually monitoring a balance that's consumed by machines, at machine speed, is a job nobody should have.

Auto Top-Up removes the failure mode instead of alerting you about it faster.

What automatic credit refills unlock

  • Uninterrupted agent traffic. Your merchant server keeps settling through demand spikes, overnight, and over weekends.
  • Runway you can reason about. Set the threshold at whatever margin makes you comfortable — a day of traffic, a week — and let refills happen underneath it.
  • Predictable spend, not surprise invoices. You choose the purchase size, and every refill is a discrete, itemized purchase in your history. Nothing is metered against you after the fact.
  • A treasury workflow that fits crypto teams. USDC moves directly from your wallet to PayAI. No card, no bank rails, no third-party billing processor holding your payment method.

How to set up Auto Top-Up

Go to Buy Credits in the merchant portal and open the Auto Top-Up tab.

1. Pick your chain and your numbers. Solana or Base, the balance that should trigger a refill, and the dollar amount to buy each time.

PayAI Auto Top-Up setup form showing the Solana and Base network toggle, credit threshold, and per-purchase dollar amount

2. Sign one approval. Your wallet will ask you to approve USDC spending — an SPL delegate on Solana, a standard ERC-20 allowance on Base. This is the only transaction you pay gas for.

3. That's it. The card shows your settings, your remaining approval, and the time of your last refill. When your balance crosses the threshold, credits arrive within about five minutes.

PayAI Auto Top-Up enabled, showing the trigger threshold, purchase amount, remaining allowance, and funding wallet

To stop, press Disable Auto Top-Up. Purchases halt immediately, and your wallet will prompt once more to revoke the on-chain approval.

Frequently asked questions

What exactly am I approving? An unlimited USDC approval to a PayAI signing address on the chain you chose. We went with unlimited rather than a fixed cap because a cap that runs out silently is worse than no automation at all — you'd be back to manual purchases without realizing it. The limits that actually govern spending are the ones in your settings, which you can change any time without another wallet signature.

Can PayAI take more than I've agreed to? Purchases only happen when your balance is below your threshold, and only for the amount you set. A daily cap limits how many can happen in 24 hours. If you want the approval itself limited on-chain, disable and re-enable at any time — and disabling revokes it entirely.

What if I revoke the approval myself? Nothing breaks. The next attempt sees the missing approval, stops, and Auto Top-Up switches off with a note explaining why. You'll see it in the dashboard the next time you look.

What if my wallet doesn't have enough USDC? The purchase is skipped and recorded. After a few consecutive failures, Auto Top-Up pauses itself so it isn't retrying against an empty wallet forever. Refill the wallet, re-enable, and you're going again.

Does the signing address ever hold my funds? No. Each purchase moves USDC directly from your wallet to PayAI's receiving address in a single transaction. The address authorized to initiate that transfer never custodies anything.

Can I still buy x402 credits manually? Yes. One-time purchases are unchanged, and they're still the default tab. Auto Top-Up sits alongside them, and automatic purchases show up in the same history with an "Auto" badge.

Should I choose Solana or Base for auto top-up? Whichever holds your USDC. Base refills confirm in well under a second; Solana takes a couple of seconds. Both are far faster than noticing an outage. If you're weighing the two chains more broadly, our Flashblocks post covers why Base settlement is as quick as it is.

Auto Top-Up is live in the merchant portal today, for every PayAI merchant, at no additional cost. Credits are priced the same whether you buy them manually or automatically.

New to x402? Start with the PayAI docs, or read why the machine economy needs agent-native payments.

If you're running agent traffic through x402 and you've ever been paged by your own error logs at an unreasonable hour, this one's for you.

Let's build.