Circle's Arc blockchain released three developer kits on Sept. 30 that let other applications embed USDC purchases, stablecoin lending and bitcoin-collateralized borrowing, the company said in a blog post.

The kits—Onramp Kit, Earn Kit and Borrow Kit—use Circle Technology Services as a software provider rather than a lender. The two credit products connect to Morpho at launch, letting integrators offer USDC and EURC deposits and cirBTC-backed loans without separately integrating each protocol.

The release extends a Sept. 21 rollout in which Circle extended bitcoin-backed USDC borrowing to eligible institutional Circle Mint customers. The Defiant reported that day that Arc's cirBTC market held $14.3 million of USDC borrowings.

What does each kit handle?

Onramp Kit embeds a hosted widget that delivers USDC or EURC to a specified Arc wallet. Debit cards, Apple Pay and Google Pay work in the U.S., U.K. and select EU jurisdictions; bank transfers support USDC in select U.S. states and EU countries. Credit cards are not supported.

Arc's onramp terms name Transak as the provider processing card, Apple Pay and Google Pay purchases. BVNK and Lead Bank supply virtual-account and payment-processing infrastructure, with Socure verifying customer identities on behalf of the payment processors. Circle does not run those services itself. The kit does not yet support converting balances back to fiat.

Integrators need a Circle API key and must complete business verification to enable card and mobile-wallet flows. End users must be at least 18, satisfy local age-of-majority rules, pass provider identity and sanctions checks and qualify under geographic restrictions.

How does bitcoin-backed borrowing work?

Borrow Kit uses cirBTC—Circle's wrapped bitcoin token, not native BTC—as collateral to borrow USDC through Morpho. The flow posts collateral and draws the loan in a single transaction on Arc; Arc pushes loan-health updates to the integrating app. Repayment releases the collateral.

Liquidation runs outside the SDK. According to Arc's loan-health documentation, liquidation takes place directly through the underlying protocol, outside the SDK: once a position breaches its market's threshold, a liquidator can repay debt in exchange for collateral at a discount.

What does the "Circle-guarded" vault label mean?

Earn Kit lets applications route USDC and EURC deposits into Morpho vaults, with integrators selecting which vaults to surface rather than connecting separately to each contract. Arc says the initial Morpho offering includes markets backed by ETH and BTC collateral. Depositors receive vault shares representing their position, and funds sit in vault contracts rather than with the software provider.

Arc applies a "Circle-guarded" label to certain vaults, a designation tied to Morpho's Vault V2 role structure. That design separates curators who set risk boundaries, allocators who deploy liquidity and sentinels who intervene. Circle frames its role as supervision, excluding vault ownership, strategy control or a guarantee against losses.

Morpho's sentinel guide tells operators to repeat deallocation as liquidity becomes available in an illiquid market. Veto and cap-reduction powers can restrain risk-taking; they are not a promise of cash on demand. Lending positions can lose value.

Arc has not set a date for adding fiat offramp to Onramp Kit, leaving applications that embed the widget without a built-in path to convert USDC balances back to traditional currency.