Vibes-Coded x402 fixture-merchant integration (evidence for #167 rail matrix)

[Rumblingb]

Split out from #167 as @doteyeso-ops suggested — #167 stays the matrix/truthfulness issue, this one carries the Vibes-Coded integration.

Context: vibes-coded.com offered to act as a fixture merchant so the x402 row of our rail matrix is backed by probes against a live counterparty instead of by the presence of an SDK import. Their reply in #167 answered the testnet, idempotency, failure-path and rate-limit questions.

First evidence pass — zero-fund, run 2026-07-27

User-Agent: AgentPay-EvidenceProbe/0.1 (+https://github.com/Rumblingb/Agentpay; issue-167), single sequential requests, well under the ~1 req/s they allowed. No funds moved.

#	Check	Expected (per #167 reply)	Observed
1	Unpaid POST /api/v1/outcomes/currency-convert	402 payment_required	402, well-formed x402v2 body with resource, serviceName, bazaar extension	✅
2	Zero-fund shape check ?preview=1	truncated live response	402, identical discovery body — no preview payload	⚠️
3	Bad key X-Vibes-Key: vb_notarealkey_000	invalid_vibes_key	402, same generic discovery body — no distinct error code	⚠️
4	Bare Python-urllib/3.11 UA	blocked at edge	403	✅

(1) and (4) reproduce exactly as described. The x402 discovery body is genuinely well-formed — this is a real rail, not a stub.

Two that didn't reproduce — likely my error, but worth pinning down

@doteyeso-ops — not raising these as defects, and the most probable explanation is that I'm calling them wrong:

• ?preview=1 returned the standard 402 rather than a truncated response. Is preview scoped to particular SKUs, or does it need a valid X-Vibes-Key present (even at zero balance) to distinguish "preview" from "anonymous"?
• Invalid key returned the generic 402 rather than invalid_vibes_key. Is the distinct error emitted only once a syntactically valid vb_ key is parsed, with mine failing the format check earlier in the chain and falling through to the unpaid path?

This distinction matters more than it looks for #167. "Underfunded", "bad key" and "never paid" are three different operational states, and a caller that cannot tell them apart cannot build correct retry logic — it will retry a permanently invalid key forever. If they are distinguishable and I simply probed wrong, that is a strong result for the matrix and I will record it as such.

Next, once the above is clarified

1. Human funds ~$1 USDC via https://vibes-coded.com/start → prepaid vb_… key, hard-capped. This is the only money that moves, and the cap is the security gate — no per-call wallet mid-run, so [P0] Establish sandbox-only payment rail contract and evidence matrix #167's "no mainnet wallets, no production credentials" constraint holds.
2. Walletless smoke via POST /api/v1/outcomes/balance/trial/claim with a stable agent_id, then retry an impulse SKU.
3. Full transcript against the 5 checks from [P0] Establish sandbox-only payment rail contract and evidence matrix #167: discovery → 402 → pay → 200; idempotent replay; nonce/replay rejection; the three failure codes; reconciliation against the public funnel.
4. Write the Vibes row into the rail matrix with links to each transcript.

Scope and security

Sandbox/evidence only. No production money movement is enabled by this issue, and nothing here makes any AgentPay rail live — see #167, which remains the gate. Per @doteyeso-ops, no PR from their side; public probes plus prepaid hops are the whole partnership.

Also worth stating plainly, as in #167: AgentPay has no live payment rail and no genuine revenue. This integration produces evidence for a matrix, not a production path.

[doteyeso-ops]

@Rumblingb — thanks for opening this and for the careful zero-fund pass. (1) and (4) matching is the right start. Both ⚠️ rows were probe shape, not rail stubs — pinning them for the matrix:

?preview=1

Needs a schema-valid JSON body. Empty/{} (or wrong field names) hit the unpaid discovery path with force_challenge, which intentionally skips preview so crawlers don’t burn COGS.

Works:

curl -sS -X POST \
  'https://vibes-coded.com/api/v1/outcomes/currency-convert?preview=1' \
  -H 'User-Agent: AgentPay-EvidenceProbe/0.1 (+https://github.com/Rumblingb/Agentpay; issue-222)' \
  -H 'Content-Type: application/json' \
  -d '{"amount":1,"from_currency":"USD","to_currency":"EUR"}'
# → 200 { "ok": true, "preview": true, "truncated": true, ... }

Notes: impulse SKUs only; one live truncated response per client IP / slug; second call → error_code: preview_exhausted. No X-Vibes-Key required for preview.

invalid_vibes_key vs unpaid

Format gate is strict: ^vb_[0-9a-f]{32}$.

Key shape	Behavior
Malformed (e.g. vb_notarealkey_000)	Treated as absent → generic unpaid payment_required (same as no header)
Well-formed but unknown (vb_ + 32 hex)	402 + error_code: invalid_vibes_key
Well-formed, known, balance < price	prepaid_insufficient (or trial_empty on trial keys)

So your exact probe was the first row — that’s why it looked identical to unpaid. For the matrix failure-path column, use something like:

# invalid_vibes_key
-H 'X-Vibes-Key: vb_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'

# unpaid / never paid
# (omit header, or send a non-matching string)

Re-proved from here just now: valid-body ?preview=1 → 200 preview; well-formed unknown key → invalid_vibes_key; your vb_notarealkey_000 → payment_required.

Once those two land in your transcript, the prepaid ~$1 /start hop is the right next gate for checks 1–5. Happy to sanity-check a paste of the failure-path table before you write the Vibes row into the matrix.