From Pay-Per-Use to Universal Payment Layer: A Comprehensive Overview of x402 V2 Upgrade

Article by: Tia, Techub News

On the evening of December 11, Coinbase-incubated open-source payment protocol x402 released version V2. This is the first major iteration since the mainnet launched in May 2025. Over the past six months, x402 has processed over 100 million payments, mainly in AI proxy microtransactions, paid APIs, and content subscription scenarios. V2, based on community feedback and production data, shifts the protocol from “single-chain, single-implementation” to a “multi-chain, pluggable, and evolvable” unified payment layer while maintaining full backward compatibility. Official documentation shows that V2 completed merging all core repositories on the same day, with SDK and Facilitator reference implementations updated simultaneously. Key changes at a glance:

V2 focuses on five areas:

Wallet Identity and Session Reuse: Supports CAIP-122 standard Sign-In-With-X, enabling a “reusable session” after a single on-chain payment. High-frequency calls within the same session no longer require repeated signatures or transfers, significantly reducing latency and fees, providing an experience close to “micro-subscriptions.”

Unified Payment Format + Multi-Chain / Fiat Routing: Standardizes the recognition of chains, assets, and traditional rails to form a “single payment format”; developers no longer need to write adapters for Base, Solana, ACH, or bank cards, as the SDK has built-in dynamic routing.

Automatic Service Discovery: Adds Bazaar API, allowing Facilitator nodes to crawl and index metadata of all x402 services (prices, supported chains, billing modes) in real-time, enabling users/agents to “search and use immediately.”

Modular SDK & Dynamic Payer: The protocol is divided into “type-logic-representation” three layers. Developers only need to implement the corresponding plugins to connect new billing models (tiered usage, commercial licensing, prepayment, subscriptions, etc.), and payment addresses can be dynamically returned by the Facilitator at runtime.

Native Support for More Tokens and Stablecoins: Besides USDC, it also defaults to compatible with native tokens of Base/Solana; CAIP standard allows horizontal extension to other chains without waiting for EIP-3009’s exclusivity lift in Q2 2026.

Community Feedback: Likes, Implementations, and Concerns

@ubountyAI (GitHub contributor) praised promptly: “V2 moved changes out of the core spec. Adding new chains or payment rails in the future only requires writing Extension and corresponding Facilitator implementations, no need to PR to the main repo. This is the correct approach for an evolvable standard.” This succinctly captures the governance benefits of “modularization” — stable protocols, externalized innovation, and sharply reduced conflicts.

Independent researcher @0xosprey believes: “Many underestimate Extensions. V1 was about ‘pushing’ new features, V2 is about the community ‘pulling’ new features. PMF is likely to erupt from some Extension.” He sees V2’s biggest selling point not as multi-chain routing but as shifting the “product-market fit” search cost onto thousands of developers, with the official only maintaining a minimal consensus layer.

The Chinese community’s voices are equally enthusiastic. Rooch Network founder @jolestar states: “V2 essentially transforms x402 from ‘a Coinbase implementation’ to ‘a community-evolving standard + pluggable reference implementation.’ This is the path to long-term viability.” This succinctly adds an economic and technical perspective to the “decentralization” banner.

Implementation is faster than commentary. Lighthouse storage developer @Dastan_rs84 upgraded the SDK on release day: “Filecoin storage now costs as low as $0.0001/MB, with proxy payments directly to the proxy, completely bypassing human wallets.” When “machine pays machine” shifts from demo to production parameters, V2’s narrative is no longer “better API” but “AI proxy Stripe.”

Of course, beyond the celebration, cold reflections remain. @corbits_dev reminds: “The protocol layer itself hasn’t changed much; mainly SDK and reference implementation improvements. The fundamental issues with two-phase settlement and relay dependencies remain unresolved.” @402zk points to privacy gaps: “In high-frequency micro-payment scenarios, privacy-stablecoins + ZK verification are still gaps; no related solutions seen in Extensions for now.”