The M2M Payment Stack Is Complete — Here's Who Built What

Six months ago, the idea of AI agents paying each other was a thought experiment. Today, the infrastructure is operational: 75 million transactions per month, three competing marketplaces, a Linux Foundation standards body with 40 members, and real money moving between machines.

Here is who built what, and where the gaps still are.

The Stack: 4 Layers

Layer 1 — The Standards War Is Over

On July 14, the Linux Foundation activated the x402 Foundation with ~40 founding members: Visa, Mastercard, Stripe, AWS, Google, Circle, Coinbase, Ripple, Solana, Stellar, Shopify, Cloudflare, Adyen, MoonPay, and two dozen others.

The numbers are staggering:

• 160 million cumulative agent-to-agent payments
• 75 million transactions in the most recent 30 days (~29/second)
• $24 million settled in that period
• Average payment: $0.32

This is real. HTTP 402 — the status code reserved in 1992 and never used — now routes millions of dollars per month between AI agents and APIs. An agent hits an endpoint, gets a 402 with payment terms, pays in USDC, retries — no human, no account, no checkout page.

Lightning Labs launched their L402 counterpart for Bitcoin/Lightning settlement. But the numbers speak: 98.6% of machine payments settle in USDC, per Visa's dual-rail report with Artemis. x402 won the standards layer.

Layer 2 — Three Marketplaces, Three Philosophies

OKX AI: The Full Stack

OKX launched OKX AI on June 30, 2026, and it's the most ambitious play. It's not just a marketplace — it's a complete agent economy operating system:

• Agent Payments Protocol (APP): An open standard for agent commerce that goes beyond pay-per-call. Escrow contracts for multi-step work, reputation tracking, and dispute resolution.
• Two connected marketplaces: One where developers list agents and set pricing, another where agents post tasks and hire each other.
• Zero-gas settlement on X Layer using USDT and USDG (Paxos). Micropayments as low as $0.01.
• Decentralized dispute resolution: Staked OKB evaluators arbitrate disagreements.

OKX CEO Star Xu called it infrastructure for "one-person companies generating over a million dollars." Launch partners include AWS, Ethereum Foundation, Solana, XMTP, CertiK, and SlowMist. OKX was valued at $25 billion in March after a ~$200M investment from ICE (NYSE parent).

AIsa: The Amazon for Agents

AIsa raised $6.5 million co-led by Alibaba and Tribe Capital in July 2026. It's building a unified transaction layer: agents discover, access, and pay for APIs, models, data, and compute through a single programmable interface. 50,000+ registered agents, 150x growth in H1 2026. Top seller on the x402 public leaderboard.

Starchild: The Open Marketplace

Launched x402 payments on August 1, 2026. Agents can publish services, receive payments, and transact directly through their Starchild wallet. All on-chain, all transparent.

Layer 3 — The Rails Multiply

Every blockchain wants to be the settlement layer for agent payments:

• Base (Coinbase): Where x402 started. The default. Gasless via EIP-3009.
• XDC Network: Demonstrated agentic commerce in NYC. Integrated Bridge (Stripe) for stablecoin infrastructure. Gasless USDC.
• Solana: Premier member of x402 Foundation. Low-latency settlement.
• Monad: AgentPay Router's home. High-throughput for micro-settlements.
• X Layer (OKX): Zero gas for OKX AI marketplace.

Circle launched Agent Nanopayments — batched, gas-free USDC payments supporting sub-$0.001 transactions. Visa's report confirmed the structural split: macro-commerce stays on card rails; micro-commerce ($0.001–$1.00) moves to stablecoins.

Layer 4 — Discovery: The Missing Piece

The payment rails are built. The marketplaces are live. But there's a gap nobody is talking about: how do agents find which services exist?

OKX, AIsa, and Starchild are walled gardens — you list your agent on their platform, using their SDK, settling on their chain. But an agent built with Claude Code, running on a developer's laptop, wanting to call 50 different x402 APIs across multiple chains — where does it look?

This is where minia2a fits: 218 x402 services, the largest public directory of agent-payable APIs. Not a marketplace — a discovery layer. Agents query /x402/preview, find the service they need, pay in USDC on Base, get their result. No platform lock-in, no SDK requirement, just HTTP.

Our data from 5,813 real agent trials shows what agents actually use:

• Infrastructure: captcha-solving (678), gas estimation (441), web scraping (304)
• Memory: find (371), recall (329), store (278) — the most engaged category
• DeFi: token security (136), Polymarket (162), DEX prices

Agents need plumbing more than they need AI — and they need a directory to find that plumbing.

What's Still Missing

The stack has four gaps as of August 2026:

1. Cross-platform discovery: An agent on OKX can't discover services on AIsa. Fragmentation is real.
2. Reputation portability: OKX has onchain reputation. AIsa doesn't. No agent can carry its rating between platforms.
3. Accountability layer: As Mintlayer noted, "The payment stack is real. The accountability layer isn't." Who verifies the work was done?
4. Agent identity: How does a service know the agent calling it is who it claims to be, without KYC?

Bottom Line

The M2M payment stack went from zero to production in 18 months. Standards (x402), marketplaces (OKX, AIsa, Starchild), rails (Base, Solana, XDC, X Layer), and discovery (minia2a) — four layers, each with real products and real users.

$24 million in monthly volume at $0.32 per transaction. 75 million transactions. This is no longer a prediction. The agent economy is running.