LangChain.js

npm install @veriproof/sdk-core @veriproof/sdk-instrumentation-langchainjs @langchain/core @langchain/anthropic

VERIPROOF_API_KEY=vp_cust_your-tenant.<key-material>
VERIPROOF_APPLICATION_ID=my-langchain-app
ANTHROPIC_API_KEY=sk-ant-...

import {
  VeriproofClient,
  VeriproofSdkOptions,
  DecisionContext,
  RiskLevel,
  SessionIntent,
  SessionOutcome,
} from '@veriproof/sdk-core';
import { createVeriproofLangChainCallbackHandler } from '@veriproof/sdk-instrumentation-langchainjs';
import { ChatAnthropic } from '@langchain/anthropic';
import { ChatPromptTemplate } from '@langchain/core/prompts';
import { StringOutputParser } from '@langchain/core/output_parsers';
import { NodeTracerProvider } from '@opentelemetry/sdk-trace-node';
 
// 1. Configure VeriProof once at startup
const provider = new NodeTracerProvider();
const client = new VeriproofClient(
  VeriproofSdkOptions.createDevelopment({
    apiKey: process.env.VERIPROOF_API_KEY!,
    applicationId: process.env.VERIPROOF_APPLICATION_ID!,
  }),
);
const { exporter } = client.configureTracing({
  serviceName: process.env.VERIPROOF_APPLICATION_ID!,
  tracerProvider: provider,
  setGlobal: true,
});
provider.register();
process.on('SIGTERM', async () => { await exporter.shutdown(); });
 
// 2. Create the LangChain callback handler — attaches VeriProof spans to chain runs
const veriproofCallback = createVeriproofLangChainCallbackHandler({
  captureInputs: true,
  captureOutputs: true,
});
 
// 3. Build a governance session
const session = client.startSession(
  'contract-summarisation',
  process.env.VERIPROOF_APPLICATION_ID,
  { sessionIntent: SessionIntent.Review },
);
 
// 4. Build and invoke a LangChain chain — all spans captured automatically
const model = new ChatAnthropic({ model: 'claude-3-5-haiku-20241022', maxTokens: 512 });
const prompt = ChatPromptTemplate.fromMessages([
  ['system', 'You are a legal analyst. Summarise the key obligations of each party.'],
  ['human', '{contract_text}'],
]);
const chain = prompt.pipe(model).pipe(new StringOutputParser());
 
const summary = await chain.invoke(
  { contract_text: '...contract text here...' },
  { callbacks: [veriproofCallback] },
);
 
// 5. Record the decision and complete the session
session
  .setDecision(DecisionContext.simple('contract-summary', summary))
  .setRiskLevel(RiskLevel.Low)
  .setOutcome(SessionOutcome.Success);
 
const result = await session.complete();
console.log('Session ID:', result.sessionId);