oocla

README

oocla

日本語

An HTTP server that speaks both the Ollama API and the OpenAI API, backed by the claude CLI. Clients of either dialect can request models by names like opus / sonnet / haiku. The name is OpenAI + Ollama + CLAude.

$ oocla serve
oocla listening on 127.0.0.1:11434

$ curl localhost:11434/api/chat -d '{
    "model": "haiku",
    "stream": false,
    "messages": [{"role": "user", "content": "Capital of Japan?"}]
  }'
{"model":"haiku:latest","message":{"role":"assistant","content":"Tokyo"},
 "done":true,"done_reason":"stop","prompt_eval_count":170,"eval_count":81}

$ curl localhost:11434/v1/chat/completions -d '{
    "model": "haiku",
    "messages": [{"role": "user", "content": "Capital of Japan?"}]
  }'
{"id":"chatcmpl-1","object":"chat.completion","model":"haiku:latest",
 "choices":[{"index":0,"message":{"role":"assistant","content":"Tokyo"},"finish_reason":"stop"}], ...}

Principles

• Tools are JSON tool definitions only. Claude Code's built-in tools are all disabled
• Claude Code's default system prompt is disabled. It behaves as a plain LLM
• No involvement in authentication. Whatever the environment's claude CLI is authenticated as is inherited verbatim
• No conversation is ever stored: every turn runs with --no-session-persistence
• Standard library only. No external dependencies

Requirements

An authenticated claude CLI on PATH. That is all. oocla itself is a single binary with no runtime dependencies; Go is not needed.

Install

Homebrew, on macOS and Linuxbrew alike:

$ brew install kazufusa/tap/oocla

With a Go toolchain:

$ go install github.com/kazufusa/oocla/cmd/oocla@latest

Or download oocla_<version>_<os>_<arch> from the releases and unpack it.

$ tar -xzf oocla_1.0.0_linux_amd64.tar.gz
$ ./oocla_1.0.0_linux_amd64/oocla version
v1.0.0

amd64 and arm64 builds are provided for linux / macOS / Windows. Verify with oocla_<version>_checksums.txt.

Build from source

Requires Go 1.25 or later.

$ git clone https://github.com/kazufusa/oocla
$ cd oocla && make build   # produces bin/oocla

Usage

oocla serve [options]

Option	Default	Description
--addr	127.0.0.1:11434	Address to listen on
--claude	claude	Path to the claude executable
--bare	false	Removes every injection, but requires API key auth (see below)

Stops on SIGINT / SIGTERM. On shutdown it waits for in-flight requests, then removes its scratch working directory.

Every turn runs claude with --no-session-persistence, so no conversation is ever written to disk. In exchange, a multi-turn conversation resends its whole history folded into one turn, so input tokens grow with the length of the conversation.

Model names

Requested name	Value passed to claude --model
opus, sonnet, haiku, fable	Same name
Any of the above with :latest	Same name
An exact model id like claude-haiku-4-5-20251001	Passed through as is

Any tag other than :latest is a 404: there is no way to serve a pinned revision.

Endpoints

Endpoint	Description
POST /api/chat	Streaming / non-streaming. tools, format, think, options.stop
POST /api/generate	Streaming / non-streaming
GET /api/tags POST /api/show GET /api/version	Model catalog
GET /api/ps	Always empty. No model is ever resident in memory
POST /api/pull	Succeeds for known models. There is nothing to transfer
POST /v1/chat/completions	OpenAI-compatible. SSE supported
GET /v1/models GET /v1/models/{model}	OpenAI-compatible
POST /api/embeddings /api/embed /v1/embeddings	501. The claude CLI has no embeddings
POST /api/create /api/copy /api/push, DELETE /api/delete	400. No local model files exist

Tools

As with Ollama, the server never executes tools. It returns tool_calls; the client executes them and sends the results back as role: "tool" messages.

$ curl localhost:11434/api/chat -d '{
    "model": "haiku", "stream": false,
    "messages": [{"role": "user", "content": "What is the weather in Tokyo?"}],
    "tools": [{"type": "function", "function": {
      "name": "get_weather",
      "parameters": {"type": "object", "properties": {"city": {"type": "string"}}}}}]
  }' | jq .message.tool_calls
[{"function":{"name":"get_weather","arguments":{"city":"Tokyo"}}}]

options

Ollama's options configure a local inference runner, and the claude CLI has almost no matching entry points. Only stop is implemented; the rest are ignored with a warning log. Nothing is refused.

think

Value	Behaviour
absent / false	Thinking is not returned
true	Delivered in message.thinking
"low" "medium" "high"	Delivered, with the reasoning depth set

Known limitations

By default the claude CLI injects a base prompt plus a <system-reminder> carrying the logged-in email address and the date, even with an empty system prompt (about 170 tokens in total). Claude Code's real agent prompt (thousands of tokens) is successfully disabled.

To remove everything, use oocla serve --bare. In that mode the claude CLI only reads ANTHROPIC_API_KEY or an apiKeyHelper, so an OAuth login no longer works. See docs/DESIGN.md for details, including measured results for --agents / --safe-mode and friends.

Also unsupported:

• Image input. The images field is accepted but unused
• Embeddings
• Any options other than stop, e.g. num_predict temperature seed
• Continuation via context on /api/generate: it is accepted but ignored, since no session is ever kept

Development

make check   # gofmt / vet / test -race / build
make e2e     # conformance tests against a real server
make dist    # builds release artifacts into dist/

make e2e calls the real claude and costs money. It needs an authenticated environment.

A release runs when a tag starting with v is pushed. CI runs make check and then publishes the make dist artifacts as they are. Running make dist VERSION=v1.0.0 locally produces the same files. Tags containing a hyphen, like v1.0.0-rc1, become prereleases.

Design and measured behaviour live in docs/DESIGN.md.