Engine Lm Studio

---
name: engine-lm-studio
description: "Reuse what LM Studio already has on this computer through its `lms` CLI: adopt its running server into the person's fleet, serve its MLX models, or serve its GGUF files without it. Load before touching LM Studio, its models or its server."
---

# LM Studio (`lms` CLI, no clicks)

Official docs, read 2026-09-29 (source files in github.com/lmstudio-ai/docs):
[App, llmster and lms](https://lmstudio.ai/docs/app/basics/lmstudio-vs-llmster-vs-lms) ·
[Headless](https://lmstudio.ai/docs/developer/core/headless) · [lms server start](https://lmstudio.ai/docs/cli/serve/server-start) ·
[lms server stop](https://lmstudio.ai/docs/cli/serve/server-stop) · [lms load](https://lmstudio.ai/docs/cli/local-models/load) ·
[lms import](https://lmstudio.ai/docs/cli/local-models/import) · [lms daemon up/down](https://lmstudio.ai/docs/cli/daemon/daemon-up) ·
[Idle TTL](https://lmstudio.ai/docs/developer/core/ttl-and-auto-evict) · [OpenAI compatibility](https://lmstudio.ai/docs/developer/openai-compat) ·
[Tools](https://lmstudio.ai/docs/developer/openai-compat/tools) · [Structured output](https://lmstudio.ai/docs/developer/openai-compat/structured-output) ·
[Import models](https://lmstudio.ai/docs/app/advanced/import-model) · [Server settings](https://lmstudio.ai/docs/developer/core/server/settings)
Tested: LM Studio 0.4.25 (`brew install --cask lm-studio`), MacBook Pro M1 Pro 32 GB, macOS 26.6, 2026-09-29.
Tags: `[doc]` official page above, `[run]` seen on the tested machine, `[?]` unverified.

## When to use it

- **A model in LM Studio's folder**, GGUF or MLX (`fleet models` → START WITH `lm-studio`): LM Studio runs
  it, because it downloaded it and loads it.
  - **Its server answering**: adopt it, but load the model yourself with a 64K+ context (below) — a model
    it loads on demand gets 8192 [run], too small for an agent.
  - **`(start it)`**: start its server yourself (below); an LM Studio that is off is the normal case, not
    a reason to switch engines.
- **An MLX model elsewhere and mlx-lm not installed**: LM Studio runs MLX on Apple silicon (its
  structured output uses Outlines for MLX [doc]), so use it instead of installing anything.
- Never install LM Studio just to serve a model: Grid's engine covers GGUF, mlx-lm covers MLX.

## Where its models live / how to list them

- `~/.lmstudio/models/<publisher>/<model>/<file>` — it keeps Hugging Face's layout [doc]. The folder can be
  moved in the app's My Models tab [doc]; no documented setting file or env var [?]. Older versions used
  `~/.cache/lm-studio/models` [?]. `fleet models` scans both.
- `lms ls --json` → `modelKey`, `path`, `format` (gguf/mlx), `sizeBytes` [run]. Keys prefix-match: a short
  key matched two downloaded models and loaded "the first one" [run] — always pass the exact key.
- A fresh install holds only an embedding model, no chat model [run].

## Installed? Running?

- App: `/Applications/LM Studio.app`. `lms` lives in `~/.lmstudio/bin` and appears only after the app ran
  once [run]. Headless servers use **llmster** instead of the app: `curl -fsSL https://lmstudio.ai/install.sh | bash` [doc].
- `lms server status` → "The server is not running." or its port [run]. Launching the app does not
  start the server [run]. `fleet models` lists a running one as `kind: lm-studio` (its `owned_by` is
  `organization_owner` [run]).

## Start an already-downloaded model

Port P from outside `machine.listeningPorts`. Always `--port`: without it the last used port is reused [doc].

    export PATH="$HOME/.lmstudio/bin:$PATH"
    lms server start --port P --bind 127.0.0.1           # starts LM Studio in the background if needed [doc][run]
    lms load <exact key> --estimate-only --context-length 65536 --gpu max -y   # fits? [doc][run]
    lms load <exact key> --context-length 65536 --gpu max --identifier <id> -y

- With the app closed, `server start` printed "Waking up LM Studio service..." and was up in 4 s; it runs
  the app as `LM Studio --run-as-service`, with no window [run]. It returns at once (not a foreground process).
- `--estimate-only` prints GPU and total memory for that context and whether guardrails allow it [doc][run].
- A model loaded with `lms load` has no idle timer and stays until unloaded [doc]; on-demand loads unload
  after 60 minutes idle [doc]. Nothing downloads on load [run].

## Ready means

Run `"$GRID_FLEET" verify --at http://127.0.0.1:P/v1 --model <id> --kind lm-studio` — it performs the
request checks with deadlines and prints each one. Also:

1. `lms server status` shows port P [run]. 2. `GET http://127.0.0.1:P/v1/models` lists `<id>` [doc][run].
3. LM Studio reports `<id>` loaded with ≥ 65536 (`/api/v0/models`, the CONTEXT `lms ps` shows) [run]. 4. One bounded `/v1/chat/completions` request with
`model: <id>`, `max_tokens` 16 → non-empty `content` [run].
A 401 means the person turned on "Require Authentication" [doc]: do not change their setting; say so and
serve the file with Grid's engine instead.

## Join Harness Compute

    "$GRID_FLEET" run -- join GRID --at http://127.0.0.1:P/v1 -m <id> --advertise-as ALIAS

`/v1` is required: with the bare root, Grid's capability probe records structured output as unsupported [run].
Grid's own detector finds LM Studio only on 1234 [run].

## Tool calls, JSON output, thinking

- Tools: `tools` on `/v1/chat/completions` and `/v1/responses`, OpenAI format [doc]. Grid's probe: tools yes [run].
- Structured output: `response_format` with `json_schema` [doc]; GGUF uses llama.cpp grammars, MLX uses
  Outlines [doc]. Grid's probe: json_schema yes, json_object no [run].
- Thinking control through the OpenAI endpoint: not documented [?]. Check `content` in the ready request.

## Memory and speed knobs

`--context-length` (≥ 65536 here), `--gpu max|off|0–1` (automatic when omitted) [doc], `--ttl <seconds>` [doc],
`--parallel <n>` (default 4 on this build [run]), `--speculative-draft-mtp` for models with MTP layers [run: in help].

## Stop

- Your model: `lms unload <id>` [doc]. Your server: `lms server stop` [doc] — the background service keeps running [run].
- The service you woke: `lms daemon down` stops llmster only, not the app [doc]; the app service ends with
  `osascript -e 'quit app "LM Studio"'` [run].
- If LM Studio was running before you came, unload only your model and leave the rest as it was.

## Known failures → what to do

| Sign | Do |
|---|---|
| "2 models match the provided model key" | use the exact `modelKey` from `lms ls --json` [run] |
| CONTEXT 8192 in `lms ps` | the model was loaded on demand; unload it and `lms load` with `--context-length 65536` [run] |
| `lms get … -y` shows a spinner forever | it downloads in the background [run]; never start a download without the go-ahead |
| a foreign GGUF must appear in LM Studio | `lms import -l -y --user-repo <user>/<repo> FILE.gguf`: **without `-l` it moves the file** [doc]; the file name must end in `.gguf` and the link must point at the real file, not a temp copy [run] |
| 401 from `/v1/models` | authentication is on in the person's settings [doc]; do not turn it off |
| a model already on disk is not in `lms ls` | no download: an **MLX folder** is symlinked as `~/.lmstudio/models/<publisher>/<name>` → the folder, then `lms ls` lists it [run]; a **GGUF** goes in with `lms import -l` (row above). Neither copies |
| answers come back as reasoning only; no request switch turns thinking off | some models keep thinking under LM Studio whatever the request says [run]. That is not a failure: `fleet verify` asks once more with room to think and passes, noting it. Never hand-test switches with `curl` (it cost minutes [run]); tell the person replies will be slower, and offer a model that can switch it off if they want that |