# Lobster Cash
Source: https://docs.treeship.dev/integrations/lobster-cash

> Cryptographic attestation for every Lobster Cash payment

Treeship provides the attestation layer for [Lobster Cash](https://www.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

```bash
npm install -g treeship @crossmint/lobster-cli
```

## Setup

<Steps>
  <Step>
    ### Initialize the Lobster Cash commerce template

    ```bash
    treeship init --template lobster-cash-commerce
    ```

    This scaffolds a project with preconfigured policies, spend limits, and the `lobster-cash` skill.
  </Step>

  <Step>
    ### Verify the installation

    ```bash
    treeship doctor
    lobster --version
    ```
  </Step>
</Steps>

## Workflow overview

Every Lobster Cash payment flows through five attested steps:

<Steps>
  <Step>
    ### 1. Wallet check

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

    ```bash
    treeship wrap --actor agent://payments -- lobster wallet status
    ```
  </Step>

  <Step>
    ### 2. Intent declaration

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

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

  <Step>
    ### 3. Approval

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

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

  <Step>
    ### 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.

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

  <Step>
    ### 5. Verify

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

    ```bash
    treeship verify --full
    ```
  </Step>
</Steps>

## 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:

```bash
./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:

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

<Callout type="info">
  The Lobster Cash skill source is available on GitHub at [`packages/skills/lobster-cash`](https://github.com/zerkerlabs/treeship/tree/main/packages/skills/lobster-cash).
</Callout>