CRE Simulation

Chainlink's CRE CLI provides a local simulation environment for testing GHOST's confidential workflows without deploying to the DON.

Prerequisites

Install the CRE CLI:

npm install -g @chainlink/cre-cli

Verify installation:

cre --version

Simulating Workflows

Settle Loans

cd ghost-settler
cre workflow simulate ./settle-loans \
  --target=staging-settings \
  --non-interactive \
  --trigger-index=0

This simulates a single cron trigger of the matching engine. The workflow will:

1. Call expireProposals on the GHOST server
2. Fetch pending intents
3. Decrypt rates (using the test private key from config)
4. Run matching
5. Post proposals back to the server

Execute Transfers

cre workflow simulate ./execute-transfers \
  --target=staging-settings \
  --non-interactive \
  --trigger-index=0

Check Loans

cre workflow simulate ./check-loans \
  --target=staging-settings \
  --non-interactive \
  --trigger-index=0

Configuration for Simulation

Each workflow's config.staging.json should point to your local server for simulation:

{
  "schedule": "every 30 seconds",
  "ghostApiUrl": "http://localhost:3000",
  "internalApiKey": "your-local-api-key"
}

DON secrets are resolved differently in simulation mode. The CRE CLI reads them from local environment variables or a .secrets file rather than the DON's secret store.

Simulation vs Production

Aspect	Simulation	Production
Execution environment	Local Node.js/WASM	DON TEE nodes
Secret management	Local env vars / .secrets file	DON threshold secret store
HTTP client	Direct fetch	ConfidentialHTTPClient (encrypted)
EVM reads	Direct RPC	EVMClient through DON
Trigger	Manual (CLI)	Cron schedule
Consensus	Single execution	Threshold consensus across DON nodes

WASM Compatibility Notes

When developing CRE workflows, be aware of WASM constraints:

Compatible libraries:

• eciesjs v0.4 (pure JS/WASM ECIES)
• viem v2 (Ethereum utilities)
• @noble/hashes (cryptographic hashes)
• ethers v6 (wallet signing, ABI encoding)

Not compatible:

• Node.js built in modules (fs, crypto, net, path)
• Native addons (anything requiring node-gyp)
• Libraries that use process.env directly (use config instead)

Import Rules

All CRE SDK imports must come from the root package:

// Correct
import { ConfidentialHTTPClient, EVMClient } from "@chainlink/cre-sdk";

// Incorrect (will fail in WASM)
import { ConfidentialHTTPClient } from "@chainlink/cre-sdk/http";

HTTP Request Pattern

The CRE SDK uses a builder pattern for HTTP requests:

const response = ConfidentialHTTPClient.sendRequest(runtime, {
  url: "https://example.com/api",
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": config.apiKey,
  },
  body: JSON.stringify(payload),
}).result();

const data = JSON.parse(response.body);

Note the .result() call at the end. This is required to execute the request and retrieve the response synchronously within the WASM runtime.

Workflow Handler Signature

Every CRE workflow exports a handler with this signature:

import type { Runtime, CronPayload } from "@chainlink/cre-sdk";

interface Config {
  schedule: string;
  ghostApiUrl: string;
  internalApiKey: string;
  // ... workflow-specific config
}

export default function handler(
  runtime: Runtime<Config>,
  payload: CronPayload
): string {
  // Workflow logic here
  return "Execution summary";
}

The handler receives the runtime (with config and SDK access) and the cron payload (trigger metadata). It must return a string that is logged by the DON.

Debugging Tips

Problem	Solution
"Module not found" in WASM	Check that the dependency is WASM compatible and imported from root
ConfidentialHTTPClient returns empty	Check that .result() is called on the request
Secrets not resolving	In simulation, set them as env vars or in .secrets
EVMClient read fails	Verify RPC URL and contract address in config
Timeout during simulation	Increase CLI timeout with --timeout=60000