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[ARTICLE · art-81125] src=simonwillison.net ↗ pub= topic=ai-tools verified=true sentiment=↑ positive

llm-chat-completions-server 0.1a0

Simon Willison released llm-chat-completions-server 0.1a0, a plugin that exposes LLM models via an OpenAI Chat Completions-compatible endpoint. The plugin leverages content-addressable logs in LLM 0.32rc1 to de-duplicate conversation messages using hashes. GPT-5.6 Sol wrote the entire plugin code.

read1 min views1 publishedJul 30, 2026

Release: llm-chat-completions-server 0.1a0

A key goal of the new content-addressable logs in LLM 0.32rc1 was being able to support OpenAI Chat Completion style requests where each incoming message extends the previous conversation, like this:

curl http://localhost:8002/v1/chat/completions \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "qwen3.5-4b",
    "messages": [
      {"role": "user", "content": "Capital of France?"},
      {"role": "assistant", "content": "Paris."},
      {"role": "user", "content": "Germany?"}
    ]
  }'

Here the conversation state is tracked by the client, so each of these requests gets longer and longer. The new schema design in LLM is designed to de-duplicate these using hashes of the individual message parts.

To test that out, I built this plugin:

uv tool install llm --pre
llm install llm-chat-completions-server
llm chat-completions-server -p 9001

Running this starts a localhost server on port 9001 that exposes your full collection of LLM models (from any plugins you have installed) using a ChatGPT Completions compatible endpoint.

GPT-5.6 Sol wrote the whole thing - it turns out it knows the OpenAI Chat Completions API shape really well.

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