Sponge is betting on agentic commerce

Sponge co-founder Eric Zhang isn’t too concerned that fear or skepticism will slow AI’s takeoff. Most transformative technologies have hit the same wall of doubt, he says, before eventually breaking through.

“There's a threshold where suddenly everyone realizes how good something is, how reliable it is,” Zhang said. “It's a slowly-then-suddenly transition."

Sponge, backed by Y Combinator and founded by Stripe alums, is building for this transition. Their thesis is that autonomous agents will soon drive the vast majority of ecommerce. Agents will act like employees or assistants for consumers; researching, recommending, and executing on their behalf.

“I'm just one person, but I might have one agent to do my shopping for me, maybe another one managing my investments,” Zhang said. “I'll have all these specialized agents, they're all going to be transacting, and they're all going to be just as capable as me.”

Stablecoins are the logical choice to power agentic transactions, Zhang said. The reasoning is mechanical; stablecoins offer a faster, cheaper way to move money, and they’re better suited for microtransactions and high-velocity payments, both of which are common in agentic commerce.

But there isn’t a single way for agents to move value. A few different rails exist and are being developed today, including protocols designed for direct agent-to-service transactions, stablecoin-to-stablecoin settlement, and, the most important one for reaching most online merchants today, cards.

Sponge tapped Rain to power its card layer. Sponge users first complete KYC; the agentic actor is an extension of the user, not onboarded as a separate entity. When a Sponge user's agent needs to make a purchase, Rain issues a single-use virtual card against the user's stablecoin balance, scoped to the guidelines the user has set, like budget and vendor. The agent uses that card to complete the transaction across the web, then the card is retired.

This allows the agent to act on the user's behalf without ever touching their broader balance, keeping the program PCI compliant because the agent is never given a reusable credential. The user's guidelines are enforced at the card itself, at the moment it's issued, not retroactively through a dispute.

“It's the easiest way to set up a card issuance program, especially one backed by stablecoins, which is the main way we store value in our wallet,” Zhang said.

What that looks like in practice today is a growing list of flows running through Sponge: agents subscribing to the software they need to do their work, topping up AI tokens and compute mid-job, booking travel, and managing recurring payments. In the most ambitious cases, an agent will run an entire workflow end-to-end. An example is an agent buying premium data, analyzing it, and executing a trade on the user's behalf. The common thread is an agent doing the work all the way through, including the part where money changes hands.

AI is moving fast enough that betting on any single outcome is a losing strategy. Sponge isn't trying to predict where the agent economy lands, just to be ready when it gets there.

"My belief is that nobody knows what's going to happen, so the best thing for us to do is to support everything,” Zhang said.