LM Studio — OpenAI Compatibility Endpoints

LM Studio exposes an OpenAI-compatible HTTP server. Any existing OpenAI client (Python, TypeScript, cURL, C#, etc.) works against it by changing only the base URL.

Default port: 1234.

Supported Endpoints

Endpoint	Method	Purpose
`/v1/models`	GET	List loaded/available models
`/v1/responses`	POST	Responses API (Codex-compatible)
`/v1/chat/completions`	POST	Chat with text and images
`/v1/embeddings`	POST	Generate text embeddings
`/v1/completions`	POST	Legacy completions

Switching Base URL

Only one line changes — the base_url / baseUrl property.

Python

from openai import OpenAI

client = OpenAI(
    base_url="http://localhost:1234/v1"
)
# rest of your code unchanged

TypeScript

import OpenAI from 'openai';

const client = new OpenAI({
  baseUrl: "http://localhost:1234/v1"
});

cURL

curl http://localhost:1234/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "<model-identifier-from-lmstudio>",
    "messages": [{"role": "user", "content": "Say this is a test!"}],
    "temperature": 0.7
  }'

Codex Support

LM Studio supports OpenAI Codex via the POST /v1/responses endpoint — the same one Codex targets.

Key Takeaways

Drop-in replacement — swap base_url to http://localhost:1234/v1; no other code changes needed
Five endpoints — models, responses, chat/completions, embeddings, legacy completions
No API key required by default (LM Studio runs locally)
Codex works because LM Studio implements /v1/responses
Model IDs differ — use the model identifier shown in LM Studio, not OpenAI slugs like gpt-4o
For richer stats (token/s, TTFT, model lifecycle) use the wiki/claude-code/lmstudio-rest-api instead

wiki/claude-code/lmstudio-anthropic-compat — /v1/messages drop-in for Claude SDK
wiki/claude-code/lmstudio-chat-completions — full param reference for /v1/chat/completions
wiki/claude-code/lmstudio-embeddings — /v1/embeddings for local RAG pipelines
wiki/claude-code/lmstudio-rest-api — native v1 API with extended model metadata
wiki/claude-code/lmstudio-idle-ttl-auto-evict — memory management for loaded models

Sources

LM Studio OpenAI Compat Docs — raw/OpenAI Compatibility Endpoints.md

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