Examples — Copy-Ready API Requests

Practical NexArt examples: certify an AI call, verify a record offline, register a Project Bundle, and wire attestation into existing pipelines with copy.

Reference Implementations

End-to-end examples showing how NexArt fits into real applications.

LangChain example

Create and verify CERs in LangChain chains and agent workflows.

Official example repo · GitHub

n8n example

Turn n8n workflow outcomes into Certified Execution Records.

Official example repo · GitHub

Common Integration Patterns

Request/response shapes you'll use in most integrations.

Certify an AI Execution

Send execution data to the certify endpoint and receive a verifiable record.

Certify Request

POST /v1/cer/ai/certify
Authorization: Bearer NEXART_API_KEY

{
  "model": "gpt-4",
  "input": "Summarize this contract and highlight key obligations.",
  "output": "The contract requires monthly reporting and a 30-day notice period for termination.",
  "metadata": {
    "appId": "contract-assistant",
    "projectId": "proj_abc123"
  }
}

Certify Response

The response includes everything needed to share and verify the record.

Certify Response

{
  "verificationUrl": "https://verify.nexart.io/c/sha256%3A9e8d7c6b5a4f3210...",
  "certificateHash": "sha256:9e8d7c6b5a4f3210...",
  "receipt": {
    "certificateHash": "sha256:9e8d7c6b5a4f3210...",
    "timestamp": "2026-03-06T12:00:01.000Z",
    "nodeId": "nexart-node-primary",
    "kid": "key_01HXYZ..."
  },
  "signatureB64Url": "MEUCIQD3a8b1c4d5e6f..."
}

The API response includes receipt and signature at the top level for convenience. In the CER bundle, this data lives at meta.attestation.

Verification URL

Records are verified publicly by certificateHash:

Verification URL

# By certificate hash (canonical)
https://verify.nexart.io/c/sha256%3A9e8d7c6b5a4f3210...

certificateHash is the canonical identity of a CER. executionId is a builder-supplied label and is not a unique artifact identifier. Do not build verification URLs around it.

Share the /c/ URL with anyone. The public verifier shows the verification status without exposing raw inputs or outputs.

Create-Only Response (No Attestation)

If you use POST /v1/cer/ai/create, you get the CER bundle but no attestation, receipt, or verification URL.

Create Response (No Attestation)

{
  "bundleType": "cer.ai.execution.v1",
  "version": "0.1",
  "createdAt": "2026-03-06T12:00:00.000Z",
  "snapshot": {
    "model": "gpt-4",
    "inputHash": "sha256:a1b2c3d4e5f67890...",
    "outputHash": "sha256:f6e5d4c3b2a10987...",
    "metadata": {
      "appId": "contract-assistant",
      "projectId": "proj_abc123"
    }
  },
  "certificateHash": "sha256:9e8d7c6b5a4f3210..."
}

Signed Receipt

The signed receipt is produced by the attestation node and stored at meta.attestation in the CER bundle.

Signed Receipt (meta.attestation)

// meta.attestation:
{
  "receipt": {
    "certificateHash": "sha256:9e8d7c6b5a4f3210...",
    "timestamp": "2026-03-06T12:00:01.000Z",
    "nodeId": "nexart-node-primary",
    "kid": "key_01HXYZ..."
  },
  "signature": "<raw Ed25519 signature bytes>",
  "kid": "key_01HXYZ..."
}

Advanced / Protocol Shapes

Lower-level protocol structures for advanced integrations and verification tooling.

n8n Flow

Certify AI results inside an n8n workflow using the NexArt community node.

AI Step (e.g. OpenAI, Claude)

↓

NexArt Certify AI Execution

↓

verificationUrl + receipt

CER Bundle (Certified)

A fully certified CER bundle with attestation data:

CER Bundle (Certified)

{
  "bundleType": "cer.ai.execution.v1",
  "version": "0.1",
  "createdAt": "2026-03-06T12:00:00.000Z",
  "snapshot": {
    "model": "gpt-4",
    "inputHash": "sha256:a1b2c3d4e5f67890...",
    "outputHash": "sha256:f6e5d4c3b2a10987...",
    "metadata": {
      "appId": "customer-chatbot",
      "projectId": "proj_abc123"
    }
  },
  "certificateHash": "sha256:9e8d7c6b5a4f3210...",
  "meta": {
    "attestation": {
      "receipt": {
        "certificateHash": "sha256:9e8d7c6b5a4f3210...",
        "timestamp": "2026-03-06T12:00:01.000Z",
        "nodeId": "nexart-node-primary",
        "kid": "key_01HXYZ..."
      },
      "signature": "<raw Ed25519 signature bytes>",
      "kid": "key_01HXYZ..."
    }
  }
}

Project Bundle (Multi-Step Workflow)

A Project Bundle groups multiple step CERs into one verifiable unit. Use this when you have a multi-step or multi-agent workflow that should be verified as a whole. Single-CER use cases do not need a Project Bundle.

Build a Project Bundle with @nexart/agent-kit

import { startWorkflow } from "@nexart/agent-kit";

const workflow = startWorkflow({ projectTitle: "Refund decision" });

const policy = await workflow.step("Check policy", async () => {
  return { eligible: true, policyId: "ret-30d" };
});

const decision = await workflow.step("Final decision", async () => {
  return { decision: "approve_refund", policy };
});

const bundle = workflow.finish();
// bundle.bundleType        = "cer.project.bundle.v1"
// bundle.integrity.projectHash = "sha256:..."
// bundle.steps[i].certificateHash = "sha256:..."

// Register the bundle on the node for public verification.
// See /docs/end-to-end-verification.

Local SDK verification of a Project Bundle works without registration. Public verification on verify.nexart.io requires the bundle to be registered on the node.

Redacted Reseal

A redacted reseal has sensitive fields removed and is re-signed for safe sharing. The certificateHash is recomputed over the redacted contents.

Redacted Reseal

{
  "bundleType": "signed-redacted-reseal",
  "version": "0.1",
  "createdAt": "2026-03-06T12:00:00.000Z",
  "snapshot": {
    "model": "gpt-4",
    "inputHash": "[REDACTED]",
    "outputHash": "sha256:f6e5d4c3b2a10987...",
    "metadata": {
      "appId": "customer-chatbot"
    }
  },
  "certificateHash": "sha256:1a2b3c4d5e6f7890..."
}

Hash-Only Timestamp

Attests only the certificateHash. Snapshot is not included. Verifies as VERIFIED when all applicable checks pass.

Hash-Only Timestamp

{
  "bundleType": "hash-only-timestamp",
  "version": "0.1",
  "createdAt": "2026-03-06T12:00:00.000Z",
  "snapshot": null,
  "certificateHash": "sha256:7f8e9d0c1b2a3456..."
}

Verification Report

Summarizes the result of validating a CER.

Verification Report (VERIFIED)

{
  "status": "VERIFIED",
  "checks": {
    "bundleIntegrity": "PASS",
    "nodeSignature": "PASS",
    "receiptConsistency": "PASS"
  },
  "reasonCodes": [],
  "certificateHash": "sha256:...",
  "bundleType": "cer.ai.execution.v1",
  "verifiedAt": "2026-03-06T12:05:00.000Z",
  "verifier": "nexart-verifier/1.0.0"
}

Node Key Discovery

Nodes publish their public keys at a well-known endpoint for independent signature verification.

Node Key Discovery

GET node.nexart.io/.well-known/nexart-node.json

{
  "nodeId": "nexart-node-primary",
  "activeKid": "key_01HXYZ...",
  "keys": [
    {
      "kid": "key_01HXYZ...",
      "algorithm": "Ed25519",
      "publicKey": "MCowBQYDK2VwAyEA..."
    }
  ]
}