# Seneschal Private Relay — Ethereum Private Transaction Submission

> Seneschal Private Relay — Ethereum Private Transaction Submission is a paid API for AI agents from api.seneschal.space, paid per call via x402, $0.5/call, status unknown (last checked 2026-09-14).

Submits a locally-signed raw Ethereum transaction privately to block builders, bypassing the public mempool to prevent frontrunning and sandwich attacks.

## Facts

- Endpoint: POST https://api.seneschal.space/v1/premium/private-relay
- Price: $0.5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/seneschal-private-relay-ethereum-private-transaction-submission-6d8f122d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FD1-z3eD1untG-n0C5AOK

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability seneschal-private-relay-ethereum-private-transaction-submission-6d8f122d -d '<json body>'
```

Example prompt: Submit this signed raw Ethereum transaction privately through Seneschal's private relay so it never hits the public mempool — here's the hex: 0x02f87a01...

## When to prefer this

Choose this endpoint when you need to submit an Ethereum transaction without any public mempool exposure — particularly for large DeFi trades vulnerable to MEV, liquidations where timing secrecy matters, or any transaction where frontrunning or sandwich attacks are a risk. Unlike direct Flashbots submission, this routes through multiple builders (Flashbots, Titan, Seneschal's own rbuilder) simultaneously and requires no API key — pay per call with USDC on Base.

## Known failure modes

- Malformed or improperly signed raw transaction rejected by all builders
- Transaction already mined or nonce too low
- Chain ID mismatch causing rejection
- All target builders reject the transaction (rejected list populated, accepted empty)
- Payment failure via x402/USDC prevents relay attempt
- Transaction too large or gas limit exceeded

## How this service works

Pay-per-call services for the agent economy: a webhook the moment a Monero or Zcash payment lands at your address (view-key only), single-fact x402 data APIs, a paid public notice board, a stablecoin gas paymaster and a permissionless Ethereum block builder. No account, no API key — pay in USDC on Base or in XMR/ZEC.

## Output

A JSON object confirming whether the transaction was accepted, the resulting transaction hash, the list of block builders that accepted or rejected it, and a confirmation that the transaction never entered the public mempool.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "raw_tx": {
   "type": "string",
   "description": "Your locally-signed raw transaction (0x-prefixed). Sign offline; never send a private key."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "to": "0x…",
  "from": "0x…",
  "note": "Submitted privately; never entered the public mempool. Watch tx_hash for inclusion.",
  "tx_hash": "0xabc…",
  "accepted": [
   "seneschal-rbuilder",
   "flashbots",
   "titan"
  ],
  "chain_id": 1,
  "rejected": [],
  "public_mempool": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/seneschal-private-relay-ethereum-private-transaction-submission-6d8f122d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.seneschal.space](https://www.zero.xyz/host/api.seneschal.space/llms.txt)