Release notes - Agent stack - 2026

2026 release notes for Agent Stack

October 2026

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2026.10.13

API additions

Facilitator Service now supports the x402 upto scheme for usage-based USDC payments on Arc, Base, and Polygon PoS.

• How Facilitator Service works
• How-to: Set up a Permit2 allowance
• Supported networks

September 2026

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2026.09.16

Documentation additions

Launched Facilitator Service, Circle’s hosted x402 facilitator for accepting USDC payments on Arc, Base, and Polygon PoS.

• Facilitator Service overview
• How it works
• Quickstart: Accept x402 payments
• Supported networks
• API reference

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2026.09.16

Blockchain expansion

Added Arc mainnet as a supported blockchain for Agent Stack.

Updated topics:

• Agent Nanopayments quickstart
• Deposit
• Pay for service
• Withdraw
• Agent Wallets quickstart
• Agent Wallets supported blockchains
• Authenticate
• Bridge
• Custom policies
• Execute contract
• Fund
• Sign
• Swap
• Transfer
• Circle CLI command reference

August 2026

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2026.08.13

Released Circle CLI 1.0.0.

This release includes the following user-facing changes:

• Updated circle gateway deposit --method eco to use Eco’s quoted, single-use deposit vaults. The command now waits for Eco to publish the deposit by default and supports --no-wait for asynchronous workflows.
• Added version compatibility checks that guide you to circle update when a newer supported version is required.

See the CLI command reference for complete command syntax, including the updated Eco deposit options.

July 2026

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2026.07.31

Launched the Agent Marketplace, a curated catalog of x402-compatible services that accept USDC. Every listing is sanctions-screened and health-checked, so agents find services that are compliant and live.

Two new integration paths:

• Buyers (AI agents) discover services through the public, keyless Discovery API—GET https://api.circle.com/v2/x402/discovery/resources—with 14 query parameters to filter by category, blockchain, price, and more. No API key or account required.
• Sellers (API owners) list a service and get paid in USDC per call. See Become a seller for the nanopayments and vanilla x402 rails, or Get listed to submit a listing.

Browse the live catalog at agents.circle.com/services.

May 2026

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2026.05.12

Added documentation for Agent Nanopayments, which enables AI agents to make sub-cent USDC payments to x402-compatible services using Circle CLI.

Documentation additions

The following Agent Nanopayments documentation was created:

• Agent nanopayments
• Quickstart: Make a nanopayment
• Nanopayment operations
• How-to: Withdraw your balance

Documentation updates

The following how-tos moved from Agent Wallets into the new Agent Nanopayments section:

• How-to: Deposit for nanopayments
• How-to: Pay for a service

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2026.05.11

Launched Agent Stack, a new product line for AI agents to manage wallets, transact onchain, and pay for x402-compatible services using Circle CLI.

Documentation additions

The following Agent Stack and Circle CLI documentation was created:

• Agent stack
• Circle CLI
• CLI command reference

The following Agent Wallets documentation was created:

• Agent wallets
• Quickstart: Create an agent wallet
• Agent wallet supported blockchains
• Agent wallet fees
• Wallet operations
• How-to: Authenticate an agent wallet
• How-to: Fund an agent wallet
• How-to: Transfer USDC
• How-to: Bridge USDC
• How-to: Swap tokens
• How-to: Deposit for nanopayments
• How-to: Pay for a service
• How-to: Execute a smart contract
• How-to: Sign a message
• How-to: Set spending policies