langchain-hs-gemini

Google Gemini Interactions v1 API client and LangChain provider for langchain-hs.

Built using type-safe Servant bindings over the official Google GenAI OpenAPI specification (Interactions v1 API), following the design patterns of MercuryTechnologies/openai.

Features

• Type-Safe Servant Bindings (Gemini.Client):
  • createInteraction (POST /v1/interactions)
  • getInteraction (GET /v1/interactions/{id})
  • cancelInteraction (POST /v1/interactions/{id}/cancel)
  • deleteInteraction (DELETE /v1/interactions/{id})
  • embedContent (POST /v1/models/{model}:embedContent)
  • batchEmbedContents (POST /v1/models/{model}:batchEmbedContents)
  • SSE Streaming (streamGeminiInteraction)
• LangChain ChatModel Provider (Langchain.Provider.Gemini):
  • Full ChatModel instance supporting synchronous invoke and streaming stream.
  • Multi-turn conversation mapping and system instructions.
  • Multi-modal content support (Base64 images, audio, documents).
  • Function calling & tool binding via ToolBinder.
  • Built-in tools: Code Execution, Google Search, Google Maps, File Search, URL Context.
• LangChain Embeddings (Langchain.Embeddings.Gemini):
  • Effect-polymorphic Embeddings instance (embedQuery and embedDocuments).

Installation

# package.yaml / .cabal
dependencies:
  - langchain-hs-gemini
  - langchain-hs-core

Quick Start

1. ChatModel Provider

{-# LANGUAGE OverloadedStrings #-}

import Control.Monad.Except (runExceptT)
import Langchain.Model
import Langchain.Provider.Gemini

main :: IO ()
main = do
  let provider = newGemini "AIzaSy..." "gemini-3.6-flash" Nothing
  res <- runExceptT $ invoke provider [userMessage "Why is the sky blue?"] Nothing
  case res of
    Left err -> putStrLn $ "Error: " ++ show err
    Right msg -> putStrLn $ extractMessageText msg

2. Streaming with Conduit

import Control.Monad.Trans.Resource (runResourceT)
import Control.Monad.Except (runExceptT)
import Langchain.Model
import Langchain.Provider.Gemini
import Langchain.Stream (collectEvents)

main :: IO ()
main = do
  let provider = newGemini "AIzaSy..." "gemini-3.6-flash" Nothing
  eEvents <- runResourceT $ runExceptT $ collectEvents $ stream provider [userMessage "Tell me a short story"] Nothing
  case eEvents of
    Left err -> print err
    Right events -> mapM_ print events

3. Embeddings

import Control.Monad.Except (runExceptT)
import Langchain.Embeddings.Core (Embeddings (..))
import Langchain.Embeddings.Gemini (defaultGeminiEmbeddings)

main :: IO ()
main = do
  let embeddings = defaultGeminiEmbeddings "AIzaSy..."
  res <- runExceptT $ embedQuery embeddings "Functional programming in Haskell"
  case res of
    Left err -> print err
    Right vec -> putStrLn $ "Generated vector with dimension: " ++ show (length vec)

4. Direct Servant Client

import Gemini.Client

main :: IO ()
main = do
  env <- newGeminiClientEnv "AIzaSy..."
  let req = createModelInteraction "gemini-3.6-flash" (TextInput "Explain quantum computing in one sentence")
  res <- runGeminiClient env (createInteraction "AIzaSy..." req)
  case res of
    Left clientErr -> print clientErr
    Right interaction -> print (interactionSteps interaction)