LangChain & LlamaIndex PII Redaction Middleware for TypeScript & Node.js

import { createLangChainTransform, PrivacyScrubberEngine } from '@privacyscrubber/sdk';
import { ChatOpenAI } from '@langchain/openai';
import { PromptTemplate } from '@langchain/core/prompts';
import { StringOutputParser } from '@langchain/core/output_parsers';
import { RunnableSequence } from '@langchain/core/runnables';

// 1. Initialize persistent agent state engine
const engine = new PrivacyScrubberEngine({
    profile: 'Legal',
    detectSecrets: true
});

// 2. Create LangChain transforms
const { preprocess, postprocess } = createLangChainTransform({
    engine,
    profile: 'Legal'
});

// 3. Build secure LCEL chain
const prompt = PromptTemplate.fromTemplate('Analyze contract for client: {client_info}');
const model = new ChatOpenAI({ modelName: 'gpt-4o' });
const parser = new StringOutputParser();

// 4. Ingest raw data -> Preprocess (Sanitize) -> Prompt -> LLM -> Parser -> Postprocess (Restore)
const chain = RunnableSequence.from([
    {
        client_info: (input) => preprocess(input.client_info).scrubbedText,
        _tokenMap: (input) => preprocess(input.client_info).tokenMap
    },
    prompt,
    model,
    parser,
    (output, config) => postprocess(output, config._tokenMap).restoredText
]);

const result = await chain.invoke({
    client_info: 'Alice Smith (alice@corp.com, SSN: 000-12-3456)'
});

console.log('Final Restored Agent Output:', result);