Interop idea: pre-flight 402 inspection before x402-proxy execution

[mayim-mayim]

Hi Cascade Protocol team,

First of all, I really like the direction of x402-proxy.

The positioning as a lightweight “curl for x402 and MPP paid APIs” feels very useful for the ecosystem, especially for one-off paid API execution and MCP-style agent workflows.

I maintain ln-church-agent, a Python buyer-side HTTP 402 runtime focused on a slightly different layer:

• pre-flight inspection before payment
• local policy / budget decisioning
• multi-rail challenge parsing across x402, L402, MPP / Payment-draft, and SVM exact flows
• safe-stop behavior for unsupported or unstable payment-session flows
• receipts, evidence, sandbox validation, and replay validation

In v1.7.2, we added an inspect CLI command:

ln-church-agent inspect <paid-api-url> --json

This command intentionally does not execute payment.

It sends an unpaid request, analyzes the HTTP 402 challenge, identifies the likely payment rail, and returns a machine-readable recommendation such as:

• pay_and_verify
• observe_only
• stop_safely
• reject_invalid
• no_payment_required

So I see a potentially complementary workflow:

ln-church-agent inspect <url> --json
# pre-flight inspection / decisioning / safety check

x402-proxy <url>
# lightweight paid execution

I do not see this as a replacement for x402-proxy.

Rather, the split seems useful:

• x402-proxy: lightweight pay-and-fetch execution
• ln-church-agent: pre-flight inspection, buyer-side decisioning, evidence-oriented runtime behavior

If this framing sounds reasonable, I would be happy to explore a small async interop note or example at some point.

No immediate integration request or PR expectation from my side — just wanted to share the idea and see whether this separation of concerns makes sense to you.