x402.api.agentmail.to now serves PaySponge challenges asking a flat +$8.00 per call. Intended?

[ApoorvKhanna]

We run Vaaya (vaaya.ai), a service catalog for AI agents. We integrated the AgentMail x402 endpoint in May 2026 and live-confirmed the documented pricing on 2026-05-26: create_inbox $2.00, send $0.01, list-messages free.

What changed (observed 2026-08-18): unpaid probes of x402.api.agentmail.to now return payment challenges whose resource.url points at api.paysponge.com, and every call carries a flat +$8.00:

• POST /v0/inboxes/{inbox}/messages/send asks 8010000 USDC base units ($8.01, was $0.01)
• GET /v0/inboxes/{inbox}/messages asks 8000000 ($8.00, was free)
• create_inbox still settled at the documented $2.00 earlier the same day

Probe excerpt (no payment attached):

{
  "x402Version": 2,
  "resource": {
    "url": "https://api.paysponge.com/v0/inboxes/crayon-board@agentmail.to/messages/send",
    "description": "Service: AgentMail API (https://api.paysponge.com/v0/inboxes/...)"
  },
  "accepts": [
    { "scheme": "exact", "network": "eip155:8453", "amount": "8010000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x6e3184C204e596dED89E8A5693B602097F4Ab687" }
  ]
}

Note the challenges are now x402Version: 2 where the host previously served v1.

Questions:

1. Is PaySponge an authorized payment processor for AgentMail? The x402 docs (docs.agentmail.to/integrations/x402) do not mention it.
2. Is the flat +$8.00 per call intended pricing, or a misconfiguration / compromised front?
3. If intended, is there a migration or pricing note we missed?

Impact on our side: our per-call price caps refuse the new amounts, so the AgentMail x402 integration is disabled for our users; we have moved sends to the keyed REST API (api.agentmail.to) in the meantime, which works fine.

Happy to share more probe data if useful.