Lobster Cash -- Treeship

Treeship provides the attestation layer for Lobster Cash (by Crossmint) payment workflows. Treeship attests every step of the payment lifecycle. Lobster Cash executes the payment. The result is a complete, cryptographically verifiable record from human intent to settled transaction.

Install

npm install -g treeship @crossmint/lobster-cli

Setup

Initialize the Lobster Cash commerce template

treeship init --template lobster-cash-commerce

This scaffolds a project with preconfigured policies, spend limits, and the lobster-cash skill.

Verify the installation

treeship doctor
lobster --version

Workflow overview

Every Lobster Cash payment flows through five attested steps:

1. Wallet check

The agent verifies it has access to a funded wallet before proceeding.

treeship wrap --actor agent://payments -- lobster wallet status

2. Intent declaration

The agent declares what it intends to purchase, the amount, and the recipient.

treeship attest decision \
  --actor agent://payments \
  --summary "Purchase 500 API credits for $49.99 USDC" \
  --confidence 0.95

3. Approval

A human (or policy engine) approves the spend. The approval binds to the intent via a nonce.

treeship attest approval \
  --approver human://ops \
  --description "approve $49.99 USDC for 500 API credits"

4. Delegate to Lobster Cash

The agent calls Lobster Cash to execute the payment. Treeship wraps the call and binds it to the approval nonce.

treeship wrap \
  --approval-nonce <nonce> \
  -- lobster pay --amount 49.99 --currency USDC --to 0x...

5. Verify

Anyone can verify the full chain: wallet check, intent, approval, payment, and settlement.

treeship verify --full

What gets attested

Each step in the workflow produces a distinct attestation with its own proof type:

Step	Attestation type	What it proves
Wallet check	Ed25519 signature	The agent had access to a funded wallet at the time of the check
Approval	Nonce binding	The human approved a specific action, bound to a unique nonce
Payment execution	Policy + spend-limit proof	The payment complied with the configured policy and did not exceed the spend limit
Session	Chain proof	Every step in the session chains together with Merkle integrity

The spend-limit proof uses the spend-limit-checker ZK circuit. This proves the payment amount falls within the approved limit without revealing the exact policy threshold to third-party verifiers.

The delegation boundary

Treeship and Lobster Cash own different parts of the workflow:

Responsibility	Owner
Attestation, approval, verification, chain integrity	Treeship
Wallet provisioning, transaction signing, settlement	Lobster Cash

This separation is intentional. Payment infrastructure and trust infrastructure have different threat models. Keeping them independent means each system can be audited, upgraded, and secured on its own.

Demo

Run the end-to-end demo to see the full workflow:

./packages/skills/lobster-cash/demo.sh

The demo walks through all five steps with a test wallet and prints the receipt chain at the end.

Verification

After a payment session, anyone can verify the full chain at:

treeship.dev/verify/[session-id]

Or via the CLI:

treeship verify --session <session-id> --full

The Lobster Cash skill source is available on GitHub at packages/skills/lobster-cash.

Lobster Cash

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