@pathcourse/langchain

@pathcourse/langchain

LangChain.js integration for PathCourse Health. Autonomous agent inference with USDC billing on Base L2 — no accounts, no credit cards, no KYC.

Install

npm install @pathcourse/langchain

Quick Start

import { ChatPathCourse } from "@pathcourse/langchain";
import { ChatPromptTemplate } from "@langchain/core/prompts";

const llm = new ChatPathCourse({ model: "pch-fast" });   // set PCH_API_KEY env var

const prompt = ChatPromptTemplate.fromTemplate("Explain {topic} in one paragraph.");
const chain = prompt.pipe(llm);
const result = await chain.invoke({ topic: "autonomous agent billing" });
console.log(result.content);

Drop-in replacement for ChatOpenAI

// Before
import { ChatOpenAI } from "@langchain/openai";
const llm = new ChatOpenAI({ model: "gpt-4o-mini" });

// After
import { ChatPathCourse } from "@pathcourse/langchain";
const llm = new ChatPathCourse({ model: "pch-fast" });

Every LangChain chain, agent, tool, and memory module keeps working unchanged.

Embeddings

import { PathCourseEmbeddings } from "@pathcourse/langchain";
import { MemoryVectorStore } from "langchain/vectorstores/memory";

const embeddings = new PathCourseEmbeddings();
const store = await MemoryVectorStore.fromTexts(
  ["hello world", "goodbye world"],
  [{}, {}],
  embeddings,
);
const results = await store.similaritySearch("greeting");

Models

Model	Rate	Min tier	Notes
pch-fast	$0.44 / M tokens	uncertified	Fast reasoning, classification, routing
pch-coder	$3.50 / M tokens	uncertified	Code generation, debugging
pch-embed	$0.015 / M tokens	uncertified	Text embeddings for semantic search / RAG
pch-translate	$0.08 / M chars	uncertified	Multilingual translation
pch-pro	$1.96 / M tokens	bronze	Deep reasoning, multi-step planning
pch-audio	$1.85 / M chars	bronze	Text-to-speech, standard quality
pch-documents	$0.26 in / $1.48 out per M tokens	bronze	Document parsing / OCR
pch-transcribe	$0.0008 / minute	bronze	Speech-to-text
pch-extract	$0.012 / M tokens	bronze	Structured data extraction
pch-rerank	$0.025 / M tokens	bronze	Reranking for RAG pipelines
pch-image	$0.028 / image	silver	Text-to-image
pch-audio-premium	$37.00 / M chars	silver	Text-to-speech, premium quality
pch-talk	$0.001 / minute	silver	Voice conversation
claude-haiku	Common rate	silver	Anthropic Claude Haiku
claude-sonnet	Common rate	gold	Anthropic Claude Sonnet

The full list above shows what's reachable through the gateway. ChatPathCourse and PathCourseEmbeddings only operate on chat-completion and embedding shapes — for image, audio, transcription, etc., use the PCH JS SDK directly.

Choosing a chat model:

• Fast response, simple task → pch-fast
• Complex reasoning, multi-step → pch-pro
• Writing or reviewing code → pch-coder
• Long context or premium reasoning → claude-sonnet (Gold tier)

Authentication

Set PCH_API_KEY in your environment, or pass pchApiKey to the constructor.

export PCH_API_KEY=pch_prod_b_...

Get an API key at pathcoursehealth.com.

Links

• Platform: pathcoursehealth.com
• npm SDK: npmjs.com/package/@pathcourse/sdk
• Python SDK: pypi.org/project/pathcourse-sdk
• Integration examples: github.com/pathcourse-health/pch-integration-examples

License

MIT