# PR7 x402 Test Completion Report

## Scope

- Replaced the `test.todo` x402 payment-security checklist with an executable, self-contained deterministic facilitator and payment-middleware sandbox.
- Used Node's built-in Ed25519 signing and verification with fixed test key seeds; no chain RPC, external wallet, or external facilitator is used.
- Implemented the x402 SDK client flow in `sdk/v3/x402.ts`: challenge parsing, canonical payment signing through an injected signer, stable payment-header retries, bounded exponential backoff, receipt parsing, and failure handling.
- Bound an inclusive `validAfter` not-before timestamp and exclusive `expiresAt` timestamp into every prepared V3 payment signature. Both client and sandbox reject invalid windows; the sandbox requires `validAfter <= now < expiresAt` before settlement.
- Added an explicit sandbox store boundary. `InMemoryX402SandboxStore` can be shared by replacement middleware instances to test retry, idempotency, and payment-identity uniqueness behavior without representing production persistence.

## Coverage

The x402 payment-security suite runs 34 deterministic cases, including:

1. Challenges and settles all 77 priced routes in `generated/route-registry.json`, asserting exact amount, asset, network, payee, x402 version, method, path, and finality.
2. Wrong signer and invalid Ed25519 signature rejection.
3. Not-before and expiry rejection, including `validAfter <= now < expiresAt` boundary behavior and invalid windows.
4. Signed and unsigned `validAfter` mutation rejection.
5. Cross-request replay rejection with no additional settlement.
6. Method/path request binding.
7. Double-fulfillment prevention for a delivery retry.
8. Idempotency-key cached response with no additional charge.
9. Replacement middleware retry and idempotency behavior through a shared in-memory store.
10. In-process payment-id claim uniqueness across two middleware instances.
11. Settlement-finality gating.
12. Facilitator timeout retry with no phantom charge.
13. Settlement followed by simulated HTTP delivery timeout, retried with the same receipt.
14. Complete receipt fields, including tx hash, block number, chain id, asset, amount, payer, payee, x402 version, and finality.

The existing registry suite adds 4 tests.

## Boundaries

The deterministic store proves only synchronous, in-process conditional-write behavior for this test model. It does not provide crash durability, multi-process coordination, production idempotency storage, blockchain settlement, facilitator availability, or live network validation. V2 routes and public discovery remain outside this sandbox and unchanged.

## Verification

Commands run from `pr7`:

```text
npm run test:x402
npm test
npm run typecheck
```

Results:

```text
x402:       3 test files passed; 42 tests passed
full PR7:   10 test files passed; 69 tests passed
typecheck:  exit code 0
```

`git diff --check -- pr7` completed with exit code 0. The registry check completed with no generated-artifact drift, and no `test.todo` or `it.todo` remains under `tests/x402`.
