x402 V2: Evolving from a fee calculation tool to an intelligent economic layer

Built by Coinbase, the x402 protocol is based on the HTTP 402 status code—a once-forgotten error code now “resurrected” to embed direct payment logic into network requests. After 6 months of operation, x402 has processed over 100 million transactions, serving a variety of scenarios from paid APIs to AI agents automatically purchasing computing resources as needed.

From Technical Bottleneck to Flexible Economic Layer

Although V1 was oriented towards guidance, practical deployment revealed clear limitations: lack of cross-chain support, limited scalability, incomplete identity verification, and high recurring payment costs. x402 V2 is not only optimized but also comprehensively redesigned, transforming payments from a point of friction into a true economic layer.

Wallet Identity Verification & Session Reuse: Turning Payments into “Login”

This is the most impactful improvement in V2, addressing the burden of high-frequency tasks (such as large-scale LLM inference, multi-tier agent steps).

In the previous version, each API call required a full payment cycle, causing significant latency and prohibitive on-chain costs. x402 V2 supports wallet identity verification (Sign-In-With-X based on CAIP-122). After the initial verification and payment completion, the protocol allows creating a “Reusable Session.”

What does this bring? Repeated access to the same resource no longer requires blockchain checks. Latency is significantly reduced, on-chain costs are nearly eliminated, and user experience becomes almost “invisible payment.” Essentially, it shifts from a “pay-per-use” model to a “micro-subscription” session model.

One-Stop Payment Interface: Combining Multi-Chain & Traditional Payments

x402 V2 creates a unified payment format, regardless of whether assets are on-chain or even off-chain.

Multi-chain support: The protocol natively supports stablecoins and tokens on Base, Solana, and other L2s without requiring developers to build custom logic.

Cross-compatibility: Through Facilitators, V2 can connect with traditional channels like ACH, SEPA, or credit card networks, paving the way for communication between Web3 and legacy finance.

Dynamic payment routing at request level: Allows specifying recipient addresses, roles, or specific callback logic, ideal for complex multi-tenant API systems where multiple clients share the same infrastructure. Supports dynamic pricing based on input content, enabling sophisticated economic models.

Plugin Architecture: Developers Free to Extend Without Modifying Core

x402 V2 separates modules, protocol standards, SDKs, and Facilitators cleanly.

When adding a new blockchain or payment behavior, developers do not need to modify core standards or the main SDK. Instead, they simply register as installing a plugin. This makes the entire system both stable and easily scalable.

The SDK also supports business priority configurations: “prioritize Solana,” “avoid mainnet,” “use USDC only”—the SDK will automatically select the most suitable option without complex “copy-paste coding.”

Automated Discovery Tools: Service Synchronization Without Manual Effort

The “Discovery” extension allows services to publish structured metadata for Facilitators to automatically collect. Service prices, routing, and metadata can be continuously updated without manual intervention or hardcoded lists.

Effect: Sellers only need to publish their API once, and the entire ecosystem automatically synchronizes. This is a step toward a self-sufficient internet economy, where information is always fresh and accurate.

Impact by User Group

End users: Payments are nearly invisible, with faster speeds and lower costs for repeated use. The first transaction completes payment, but subsequent calls within the same session (such as continuous AI chat or accessing paid content) do not require additional payment if resources have already been purchased. Payment methods are also more diverse and convenient, from crypto to credit cards.

Developers & service providers: V2 addresses architectural issues of V1, offering high flexibility and reduced maintenance. Payments shift from “hardcoded” to “configurable,” making it easy to build dynamic pricing models based on input content (data size, model, etc.). Paywalls are modularized, allowing quick integration with different backends.

AI agents: This is a true revolution. Agents can be assigned wallets with budgets, autonomously decide when to call APIs to complete tasks, purchase computing resources, and search for optimal resources across networks. From “executor” to autonomous “economic entity.”

Outlook & Challenges

x402 V2 marks the evolution from a “per-use fee” tool to a flexible economic layer, enabling new identity and payment models. It could become the infrastructure for future internet payments.

However, realizing this vision requires overcoming many barriers: ecosystem adoption levels, module risks, refund and dispute handling difficulties, and regulatory uncertainties. But the potential is too great to ignore.