Crossmint's agent wallets put the rules on-chain: a smart wallet with two signers, where the owner has full control and the agent's TEE-held key can only act within limits the contract enforces. It is the hosted design closest to Coldstar's, and the differences are exactly where the two keys live.
Coldstar as the cold owner signer for a Crossmint smart wallet is a natural fit if Crossmint exposes owner signing that way; check their docs for your chain.
| Coldstar | Crossmint | |
|---|---|---|
| Who holds the root key | You. The cold root lives encrypted on your own USB drive. No vendor holds a key, a share, or an account. | Split: the owner signer is held by you (a person or company) with full control; the agent signer is held in Crossmint's TEE with scoped control. Owner can revoke. |
| Where the key lives | On your machine. The air-gapped root signs a bounded policy envelope; a disposable session key signs routine transactions inside it. | Owner key: wherever you keep it. Agent key: Crossmint's TEE (vendor not named). Rules: on-chain in the wallet contract. |
| Policy engine | Per-transaction limit, daily cap, program allowlist, recipient allowlist and blocklist, escalate-above threshold. Evaluated locally, first match wins, before any signature exists. | Per-transaction limits, rolling caps, allowlisted recipients, time windows, "or any other policy the owner configures", enforced by the smart contract at the wallet level. Exact Solana rule set not detailed on the docs overview. |
| Out-of-policy transactions | ESCALATE to a human over air-gapped QR, or REJECT. No signature is produced for a rejected transaction. | Reverted by the contract. Owner retains full control and can revoke the agent. Cards offer spend limits and human approval; a wallet-level approval queue is not documented. |
| Cold / offline root | Yes — the root key never touches a networked machine. | Possible in principle: the owner signer is customer-held, so it could be a cold key. Not documented as a product feature. |
| Agent integration | Framework-agnostic: the agent proposes an unsigned transaction, the signer decides. CLI signer today; MCP server in progress. | Agent Wallets plus Agentic Cards and x402; white-label SDK that plugs into agent frameworks as a tool. Solana Agent Kit ships a Crossmint example. |
| Solana support | Solana mainnet. Core is chain-agnostic; EVM signing exists. | Yes: agent wallets on EVM, Solana, and Stellar. |
| Source & self-hosting | Open source (MIT), self-hosted. No API key, no SaaS dependency, nothing to go down. | SDKs public; wallet contract and audit status not confirmed on the fetched pages. Hosted. |
| Pricing | Free software plus a ~$10 drive. | Free for 1,000 monthly active wallets; then from $0.05 per active wallet with volume discounts; enterprise custom. |
| Maturity | Beta — the signing core and policy engine are in scope for the planned independent audit. | Production; SOC 2 Type II; MiCA CASP authorisation. |
Crossmint and Coldstar agree that the agent must never hold the root and that rules must bind it. Crossmint enforces the rules on-chain with a vendor-held agent key; Coldstar enforces them locally with an owner-held cold root and a disposable session key.
Crossmint's two-signer model is a good one. The owner holds full control; the agent's key is scoped by the wallet contract and lives in Crossmint's TEE. You are trusting the wallet program, Crossmint's enclave operation for the agent key, and your own custody of the owner key. Limits that live on-chain are verifiable by anyone, which is a genuine advantage.
Coldstar keeps both halves on your side. The air-gapped root signs a policy envelope; the agent's session key is disposable and lives on a host you run; the policy is evaluated locally before any signature exists. There is no program to audit and no vendor on the signing path, at the cost of on-chain verifiability of the limits.
Crossmint is production and certified. Coldstar is beta, pre-audit.
Crossmint, inside a TEE, scoped by the on-chain wallet rules. The owner key is yours. With Coldstar, the root is yours and offline, and the agent's session key runs on your own host.
They are verifiable by third parties and survive compromise of off-chain components. Local policy is faster to change, can include escalation to a human, and does not depend on a smart-wallet program. Many teams will want both, using Squads spending limits for the on-chain ceiling.
Not as an integration today. If Crossmint's owner signer can be an external Solana keypair, a Coldstar-held key could serve as the cold owner.
Open source, MIT. macOS, Linux, Windows — and on the Solana Seeker dApp Store.
pip install coldstar
Third-party facts were checked against the vendor's own pages on the date above. Pricing and feature sets change; if something here is out of date, tell us and we will fix it.