LmsPs — LM Studio PowerShell MCP Server

A minimal, environment‑driven MCP server that exposes a persistent PowerShell session to LM Studio. It keeps a single pwsh.exe/powershell.exe process alive and offers tools to run commands, manage cwd, and get/set env vars. Responses to the client are trimmed (default 500 chars) while full I/O is logged.

Features

Tools: ps_run, cd, cwd, env_get, env_set, ping
Persistent PowerShell between calls (stateful session)
500‑char response trim to the client; full logs on disk
All paths/config via environment variables (no hardcoded paths)

Install (dev)

cd K:/Repos/LmsPs
python -m venv .venv
. .venv/Scripts/activate  # Windows
pip install -e .

Run (stdio)

From WSL (recommended by LM Studio):

bash K:/Repos/LmsPs/scripts/start_ps_mcp_stdio.sh

Or directly (Windows):

python -m lmsps.server

Environment variables

LMSPS_POWERSHELL_PATH — Preferred path to Windows PowerShell 5.1 (default C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe).
LMSPS_PWSH — Legacy override for the PowerShell executable (retained for backward compatibility).
LMSPS_LOGDIR — log directory (default: <repo>/logs)
LMSPS_TRIM_CHARS — max characters returned to client (default: 500)
LMSPS_TIMEOUT_SEC — per‑call timeout in seconds (default: 30)
LMSPS_MAX_COMMAND_CHARS — maximum PowerShell command length accepted by ps_run (default: 8192)

`ps_run` tool

Arguments
- command (required): exact PowerShell command text passed to -Command.
- timeout_sec (optional): overrides the per-call timeout (defaults to LMSPS_TIMEOUT_SEC or 30s).
- trim_chars (optional): overrides the maximum characters returned to the client (defaults to LMSPS_TRIM_CHARS or 500).
Execution
- Uses Windows PowerShell 5.1 (powershell.exe) with -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Bypass to avoid side effects. Override the path with LMSPS_POWERSHELL_PATH (or legacy LMSPS_PWSH).
- The process runs with the server's current working directory and an environment overlay managed by env_set.
- The working directory persists across calls; use cd to reposition before running relative-path commands.
Return payload
- The tool now returns a JSON object with fields:
  - status: ok, powershell-error, timeout, invalid-command, or internal-error.
  - exit_code: integer PowerShell exit code (or null for tool-level failures).
  - stdout / stderr: decoded (UTF‑16/UTF‑8 aware) output trimmed to trim_chars.
  - message: optional human-readable context (e.g., timeout notice, validation failure).
  - timeout_seconds: populated only for timeout responses so callers know the enforced limit.
Validation & failure modes
- Commands must be non-empty strings and shorter than LMSPS_MAX_COMMAND_CHARS; invalid input returns status: invalid-command without touching PowerShell.
- Timeouts return status: timeout with any partial decoded output that PowerShell produced.
- Spawn failures or unexpected exceptions return status: internal-error along with the exception type in message.

LM Studio configuration example

Add to your LM Studio settings JSON:

{
  "mcpServers": {
    "lmsps": {
      "command": "bash",
      "args": ["-lc", "K:/Repos/LmsPs/scripts/start_ps_mcp_stdio.sh"],
      "env": {
        "LMSPS_PWSH": "/mnt/c/Program Files/PowerShell/7/pwsh.exe",
        "LMSPS_LOGDIR": "/mnt/k/LMstudio/LmsPs/logs",
        "LMSPS_TRIM_CHARS": "500"
      }
    }
  }
}

Smoke test (from LM Studio)

ps_run → Get-Process | Select-Object -First 3
cwd → should show current location
cd → change to a test directory and re‑run cwd
env_set/env_get → write/read a temp environment variable
Re‑run ps_run to confirm session persistence

Working directory model

The MCP server maintains a single-process working directory stored in memory.
cwd reports the current directory, and cd updates it (accepting absolute or relative paths).
Subsequent ps_run commands execute within that directory, so Get-ChildItem -Path . and Get-Content on relative paths resolve as expected.
FastMCP routes requests sequentially, so there is no concurrent mutation of this state; the model matches LM Studio's expectation of a single PowerShell session.

Logs

Full request/response JSON lines are appended to LMSPS_LOGDIR/lmsps_server.log.

Repo layout

src/lmsps/server.py — MCP server implementation
scripts/start_ps_mcp_stdio.sh — stdio launcher (used by LM Studio)
logs/ — default log directory (overridable via LMSPS_LOGDIR)

License

MIT

LmsPs — LM Studio PowerShell MCP Server

Environment variables

LMSPS_POWERSHELL_PATH — Preferred path to Windows PowerShell 5.1 (default C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe).

LMSPS_PWSH — Legacy override for the PowerShell executable (retained for backward compatibility).

LMSPS_LOGDIR — log directory (default: <repo>/logs)

LMSPS_TRIM_CHARS — max characters returned to client (default: 500)

LMSPS_TIMEOUT_SEC — per‑call timeout in seconds (default: 30)

LMSPS_MAX_COMMAND_CHARS — maximum PowerShell command length accepted by ps_run (default: 8192)

ps_run tool

Arguments

command (required): exact PowerShell command text passed to -Command.
timeout_sec (optional): overrides the per-call timeout (defaults to LMSPS_TIMEOUT_SEC or 30s).
trim_chars (optional): overrides the maximum characters returned to the client (defaults to LMSPS_TRIM_CHARS or 500).

Execution

Uses Windows PowerShell 5.1 (powershell.exe) with -NoLogo -NoProfile -NonInteractive -ExecutionPolicy Bypass to avoid side effects. Override the path with LMSPS_POWERSHELL_PATH (or legacy LMSPS_PWSH).
The process runs with the server's current working directory and an environment overlay managed by env_set.
The working directory persists across calls; use cd to reposition before running relative-path commands.

Return payload

The tool now returns a JSON object with fields:
- status: ok, powershell-error, timeout, invalid-command, or internal-error.
- exit_code: integer PowerShell exit code (or null for tool-level failures).
- stdout / stderr: decoded (UTF‑16/UTF‑8 aware) output trimmed to trim_chars.
- message: optional human-readable context (e.g., timeout notice, validation failure).
- timeout_seconds: populated only for timeout responses so callers know the enforced limit.

Validation & failure modes

Commands must be non-empty strings and shorter than LMSPS_MAX_COMMAND_CHARS; invalid input returns status: invalid-command without touching PowerShell.
Timeouts return status: timeout with any partial decoded output that PowerShell produced.
Spawn failures or unexpected exceptions return status: internal-error along with the exception type in message.

LM Studio configuration example

Add to your LM Studio settings JSON:

{ "mcpServers": { "lmsps": { "command": "bash", "args": ["-lc", "K:/Repos/LmsPs/scripts/start_ps_mcp_stdio.sh"], "env": { "LMSPS_PWSH": "/mnt/c/Program Files/PowerShell/7/pwsh.exe", "LMSPS_LOGDIR": "/mnt/k/LMstudio/LmsPs/logs", "LMSPS_TRIM_CHARS": "500" } } } }

Working directory model

The MCP server maintains a single-process working directory stored in memory.

cwd reports the current directory, and cd updates it (accepting absolute or relative paths).

Subsequent ps_run commands execute within that directory, so Get-ChildItem -Path . and Get-Content on relative paths resolve as expected.

FastMCP routes requests sequentially, so there is no concurrent mutation of this state; the model matches LM Studio's expectation of a single PowerShell session.

LmsPs

LmsPs — LM Studio PowerShell MCP Server

Features

Install (dev)

Run (stdio)

Environment variables

ps_run tool

LM Studio configuration example

Smoke test (from LM Studio)

Working directory model

Logs

Repo layout

License

LmsPs — LM Studio PowerShell MCP Server

Features

Install (dev)

Run (stdio)

Environment variables

ps_run tool

LM Studio configuration example

Smoke test (from LM Studio)

Working directory model

Logs

Repo layout

License

`ps_run` tool

`ps_run` tool