feat: add OfframpActionProvider for Base USDC cash-out

[ADWilkinson]

Description

AgentKit already supports bringing funds onchain with get_onramp_buy_url. This PR completes the other half of the flow by adding OfframpActionProvider, giving agents a native way to cash out Base USDC to fiat through @usdctofiat/offramp.

With this provider, agents can:

• Use fast for live market pricing with 0% spread
• Use best to cash out through the Delegate strategy
• Send fiat to eligible payment rails such as Revolut and Venmo

This enables complete fiat-to-crypto-to-fiat workflows inside AgentKit: fund a wallet, transact onchain, and cash out when the user is ready.

Implementation

The new offramp action wraps:

cashout({ mode, signer, amount, currency, platform, payee })

It follows the existing AgentKit action-provider pattern and supports Base mainnet.

Tests

Added 10 unit tests covering provider behavior, network support, argument forwarding, and SDK responses. The SDK is mocked, so no USDC is spent during tests.

cd typescript/agentkit
pnpm test -- offrampActionProvider

pnpm exec changeset status recognises @coinbase/agentkit for a patch release.

The action-provider contract is covered with a mocked SDK, so no USDC is spent. A live chatbot cash-out was not run because it would sign and submit a financial transaction; that path remains host-controlled.

Links

• Offramp SDK
• Developer docs
• USDCtoFiat

Checklist

• Added documentation to all relevant README.md files
• Added a changelog entry

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[ADWilkinson]

Updated to current main in cc80691. The current lint rules exposed missing public JSDoc and stale schema formatting; fixed in d4f82e3. On the merged head, all 10 focused offramp tests pass; targeted ESLint and Prettier checks pass; TypeScript compilation with tsc --noEmit passes; git diff --check passes. Remaining gates are maintainer review / Heimdall.