ocaml-ai-sdk

Type-safe, provider-agnostic AI model abstraction for OCaml, inspired by the Vercel AI SDK. Targets wire compatibility with AI SDK v6 so you can pair an OCaml backend with @ai-sdk/react frontends.

Libraries

Library	opam lib	Description
ai_provider	ocaml-ai-sdk.ai_provider	Provider abstraction — language model module types, tool definitions, prompt types, GADT-based provider options
ai_provider_anthropic	ocaml-ai-sdk.ai_provider_anthropic	Anthropic Messages API — streaming SSE, thinking, cache control, full Claude model catalog
ai_provider_openai	ocaml-ai-sdk.ai_provider_openai	OpenAI Chat Completions API — streaming SSE, tool calling with strict mode, GPT-4o/o1/o3/o4-mini catalog
ai_provider_openrouter	ocaml-ai-sdk.ai_provider_openrouter	OpenRouter Chat Completions API — model routing, provider preferences, reasoning, web search, usage accounting, prompt caching
ai_core	ocaml-ai-sdk.ai_core	Core SDK — generate_text, stream_text (with tool loops), UIMessage stream protocol, server handler, structured output
ai_sdk_react	ai-sdk-react.ai_sdk_react	Melange bindings for @ai-sdk/react — useChat, useCompletion, v6 part types

Quick start

opam install ocaml-ai-sdk

One-shot generation

open Ai_core
open Ai_provider_anthropic

let () =
  Lwt_main.run @@
  let model = Anthropic.create_model "claude-sonnet-4-20250514" in
  let%lwt result = Generate_text.generate ~model ~prompt:"Say hello" () in
  Lwt_io.printl result.text

Streaming

let () =
  Lwt_main.run @@
  let model = Anthropic.create_model "claude-sonnet-4-20250514" in
  let%lwt result = Stream_text.stream ~model ~prompt:"Tell me a joke" () in
  Lwt_stream.iter_s Lwt_io.printl result.text_stream

Chat server (with UIMessage protocol)

let handler = Server_handler.create ~model ()
(* Serves SSE responses compatible with useChat() from @ai-sdk/react *)

See examples/ for complete runnable demos including tool use, thinking, structured output, OpenRouter prompt caching, and full-stack Melange apps.

Architecture

ai_provider          Provider abstraction (module types, GADT options)
├── ai_provider_anthropic   Anthropic implementation
├── ai_provider_openai      OpenAI implementation
├── ai_provider_openrouter  OpenRouter implementation
└── ai_core                 Core SDK (generate, stream, UIMessage protocol)

Key design choices:

• Provider options use an extensible GADT (type _ key = ..) for compile-time type-safe provider-specific settings (e.g. thinking budget, cache control, OpenRouter routing)
• Prompt types are role-constrained variants — System accepts only strings, User accepts text + files, etc.
• Streaming uses Lwt_stream.t — stream_text returns synchronously with streams populated by a background Lwt task
• UIMessage protocol emits SSE chunks matching the ai@6 Zod schemas exactly, so useChat() works without adaptation

AI SDK v6 compatibility

The UIMessage stream protocol (x-vercel-ai-ui-message-stream: v1) is wire-compatible with:

• @ai-sdk/react 3.x (useChat, useCompletion)
• ai 6.x (core SDK)

All chunk types are supported: text, reasoning, tool call (start/delta/result), source, file, data, error, finish message/step.

Requirements

• OCaml >= 4.14
• For Melange bindings: melange >= 4.0.0

Development

make build    # Build all libraries
make test     # Run test suites
make dev      # Watch mode

License

MIT