# DELTA Witness Preflight Check

> DELTA Witness Preflight Check is a paid API for AI agents from delta-witness-api.ruphussten.workers.dev, paid per call via x402, $5/call, status unknown (last checked 2026-09-15).

Fetches a public URL, verifies its content against expected conditions, and returns a cryptographic proof bundle for machine-verifiable trust before an autonomous action

## Facts

- Endpoint: POST https://delta-witness-api.ruphussten.workers.dev/v1/preflight
- Price: $5/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/delta-witness-preflight-check-294f3aee
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ifgy92XpiQe6DIv2ehuTV

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 delta-witness-preflight-check-294f3aee -d '<json body>'
```

Example prompt: Before you proceed with the purchase, do a preflight check on https://shop.example.com/product/42 and verify the page still contains 'In Stock' and hasn't changed since the last proof — freshness within 300 seconds.

## When to prefer this

Choose this endpoint when an autonomous agent needs machine-verifiable, cryptographically-attested evidence of a public web page's content state before taking an irreversible or high-stakes action. It is distinct from simple web scraping because it produces a signed proof bundle with a persistent manifest URL — ideal for audit trails, compliance workflows, or multi-agent trust chains where one agent must prove to another what a page said at a specific moment.

## Known failure modes

- URL is unreachable or returns a non-200 status — ok:false with network error detail
- Expected 'contains' strings not found in fetched content — safe:false
- Expected 'excludes' strings found in fetched content — safe:false
- Content hash differs from prior_proof_id baseline — changed:true
- Content is older than freshness_seconds threshold — staleness violation
- Invalid URL format (not http/https) — 400 validation error
- prior_proof_id not found or malformed — 422 error
- Payment not received or insufficient — 402 Payment Required

## How this service works

Paid, machine-verifiable capture and preflight checks for public web sources.

## Output

A JSON object indicating whether the preflight passed (ok, safe, changed flags), a UUID proof_id, a SHA-256 bundle_root hash of the observed content, an ISO 8601 observed_at timestamp, and URLs to the full proof manifest and human-readable public proof page for independent verification.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "pattern": "^https?://",
   "description": "Public HTTP(S) source to observe before an action."
  },
  "expected": {
   "type": "object",
   "properties": {
    "contains": {
     "type": "array",
     "items": {
      "type": "string",
      "maxLength": 200
     },
     "maxItems": 10
    },
    "excludes": {
     "type": "array",
     "items": {
      "type": "string",
      "maxLength": 200
     },
     "maxItems": 10
    },
    "html_sha256": {
     "type": "string",
     "pattern": "^sha256:[0-9a-f]{64}$"
    },
    "markdown_sha256": {
     "type": "string",
     "pattern": "^sha256:[0-9a-f]{64}$"
    }
   },
   "additionalProperties": false
  },
  "prior_proof_id": {
   "type": "string",
   "pattern": "^[0-9a-fA-F-]{36}$",
   "description": "Optional DELTA proof to use as the hash baseline."
  },
  "freshness_seconds": {
   "type": "integer",
   "maximum": 2592000,
   "minimum": 0
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "safe": true,
  "changed": false,
  "product": "preflight",
  "proof_id": "7d9d12f7-8f91-5f41-9f0c-5ef257d9ea5d",
  "bundle_root": "sha256:0000000000000000000000000000000000000000000000000000000000000000",
  "observed_at": "2026-08-31T00:00:00.000Z",
  "manifest_url": "https://delta-witness-api.ruphussten.workers.dev/v1/proofs/7d9d12f7-8f91-5f41-9f0c-5ef257d9ea5d",
  "public_proof_url": "https://delta-witness-api.ruphussten.workers.dev/p/7d9d12f7-8f91-5f41-9f0c-5ef257d9ea5d"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/delta-witness-preflight-check-294f3aee/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from delta-witness-api.ruphussten.workers.dev](https://www.zero.xyz/host/delta-witness-api.ruphussten.workers.dev/llms.txt)