langchain-pathcourse

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

Install

pip install langchain-pathcourse

Quick Start

from langchain_pathcourse import ChatPathCourse
from langchain_core.prompts import ChatPromptTemplate

llm = ChatPathCourse(model="pch-fast")   # set PCH_API_KEY env var

prompt = ChatPromptTemplate.from_template("Explain {topic} in one paragraph.")
chain = prompt | llm
print(chain.invoke({"topic": "autonomous agent billing"}))

Drop-in replacement for ChatOpenAI

ChatPathCourse extends ChatOpenAI. Anywhere you use ChatOpenAI in LangChain — chains, agents, tools, memory, callbacks — just swap in ChatPathCourse and your code keeps working.

# Before
from langchain_openai import ChatOpenAI
llm = ChatOpenAI(model="gpt-4o-mini")

# After
from langchain_pathcourse import ChatPathCourse
llm = ChatPathCourse(model="pch-fast")

Embeddings

from langchain_pathcourse import PathCourseEmbeddings
from langchain_community.vectorstores import FAISS

embeddings = PathCourseEmbeddings()
store = FAISS.from_texts(["hello world", "goodbye world"], embeddings)
results = store.similarity_search("greeting")

Models

The full list above shows what's reachable through the gateway. ChatPathCourse and the embeddings class only operate on chat-completion and embedding shapes — for image, audio, transcription, etc., use the PCH Python SDK directly. The token-counting models all share one OpenAI-compatible endpoint, so the same ChatPathCourse instance works for any of them by changing the model= argument.

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)

List all models programmatically:

ChatPathCourse.list_models()

Authentication

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

export PCH_API_KEY=pch_prod_b_...

Developer access — $5 USDC. Send $5+ USDC on Base (chain ID 8453) to the PCH treasury wallet, then call pathcourse.claim_key(tx_hash, wallet) to retrieve your key. No accounts, no credit card, no KYC. $5 buys thousands of pch-fast calls — enough to verify any integration. Top up to $25 lifetime and your account auto-upgrades to Uncertified with pch-coder access. Treasury address: see payment.treasury_wallet in /.well-known/agent.json.

Links

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

License

MIT