BLTSpice MCP Server

Converts ltspice netlist .net to ltspice .asc file format!

REALTIME LTSpice simulation and export to .csv!

- src/bltspice_mcp/server source code
- tests/unit/unit tests
- tests/integration/integration tests
- testfiles/copied example assets (.asc/.log/.raw/.asy/.txt/.net)
- examples/codex/andexamples/opencode/MCP call recipes for LLM agents
- config.jsonserver configuration
- bltspice_mcp_for_LLM.mdLLM tool-calling reference

- Python 3.11+
- LTspice installed
- Linux/macOS with Wine for Windows LTspice binary

python3 -m venv .venv . .venv/bin/activate pip install -U pip pip install "PyLTSpice>=6.0.1" "fastmcp>=3.4.4" "electronics-design>=0.1.9" pytest pytest-asyncio pip install -e .

{ "mcp_server_name": "My PyLTSpice MCP Server", "mcp_server_url": "http://localhost:7543", "wine_path": "/usr/bin/wine", "ltspice_path": "/home/brosnan/.wine/drive_c/Program Files/ADI/LTspice/LTspice.exe", "enable_extra_tools": true, "timeout": 600, "convert_settings": { "ltspice_windows_path": "C:\\users\\brosnan\\AppData\\Local\\LTspice\\", "ltspice_wine_path": "~/.wine/drive_c/users/brosnan/AppData/Local/LTspice/", "custom_search_paths": ["./valid_asy/"], "minimum_dist": 32, "wire_pin_out_dist": 16, "grid_size": 16, "autoplace_iter": 12, "ltspice_version": 4.1, "voltage_must_have_dc": true } }

convert_settingsis optional. Each setting is optional and receives a default when omitted. Relativecustom_search_pathsare resolved from the server project root; Windows paths remain in Windows syntax for Wine-based conversion.

mcp_server_urlsupportshttp://,https://, andstdio://.

. .venv/bin/activate python -m bltspice_mcp --config /home/brosnan/bltspice_mcp/bltspice_mcp/config.json

{ "mcpServers": { "bltspice_mcp": { "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python", "args": [ "-m", "bltspice_mcp", "--config", "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json" ] } } }

{ "mcpServers": { "bltspice_mcp": { "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python", "args": [ "-m", "bltspice_mcp", "--config", "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json" ] } } }

{ "mcp_servers": { "bltspice_mcp": { "command": "/home/brosnan/bltspice_mcp/bltspice_mcp/.venv/bin/python", "args": [ "-m", "bltspice_mcp", "--config", "/home/brosnan/bltspice_mcp/bltspice_mcp/config.json" ] } } }

- performing LTspice operation in progress
- LTspice operation completed!
- invalid input!
- file not found!
- unsupported file type!
- simulator not configured!
- simulation failed!
- parser failed!
- LTspice operation timed out!
- internal error

Each payload includesoperation. Successful responses includeoutput, and optionallyoutput_obj_name.

Each MCP session owns a dedicated OS worker process group containing its dispatcher registry, PyLTSpiceRunTaskthreads, simulator subprocesses, and callback children.stop_resetinterrupts that session immediately withSIGKILL, clears operations that were already queued for it, and discards its object registry. It does not signal worker groups belonging to other MCP sessions. Because operating systems applySIGKILLto processes rather than individual threads, killing the session worker process terminates all of its threads atomically.

The immediate response is the normal in-progress payload. Pollexecute_statusuntil bothstatusis complete andoperationisstop_reset. Its output includesworker_process_killed,processes_killed,threads_terminated_with_processes, andqueued_operations_killed. Work submitted after the reset call waits until the reset completes and runs in a fresh session worker.

Convert selected traces from a loadedRawReadobject into one CSV per wave/step.

- object_name: name of a storedRawReadobject
- trace_refs: array of trace names (any length), for example["V(opamp_input)", "V(opamp_output)"]
- output_files:

- string prefix/path, example./sim_wave_-> writes./sim_wave_0.csv,./sim_wave_1.csv, ...
- or array of explicit.csvpaths with one entry per wave

{"tool":"execute","arguments":{"api_name":"traces_to_csv","inputs":{"object_name":"raw","trace_refs":["V(opamp_input)","V(opamp_output)"],"output_files":"./sim_wave_"}}}

LTspice schematic conversion viaexecute

The followingelectronics-designAPIs are available throughexecute:is_valid_ltspice_netlist_fileandltspice_netlist_to_asc.

ltspice_netlist_to_ascreceives the configuredconvert_settingsautomatically. A request may include aninputs.convert_settingsobject to override individual values for that call.is_valid_ltspice_netlist_fileonly requires its filepath.voltage_must_have_dcmust be a JSON boolean and is passed toltspice_netlist_to_ascinsideconvert_settings.

run_ltspice_to_csv.pyEquivalent MCP Flow

Equivalent artifacts are included for the op-amp example workflow:

- netlist fixture:/home/brosnan/bltspice_mcp/bltspice_mcp/testfiles/opampdouble.net
- Codex recipe:/home/brosnan/bltspice_mcp/bltspice_mcp/examples/codex/run_ltspice_to_csv.md
- OpenCode recipe:/home/brosnan/bltspice_mcp/bltspice_mcp/examples/opencode/run_ltspice_to_csv.md
- integration test:/home/brosnan/bltspice_mcp/bltspice_mcp/tests/integration/test_run_ltspice_to_csv_via_mcp.py

- Core MCP flow test (runtime_info,execute,execute_status,stop_reset)
- Mapping coverage for the checked-in PyLTSpice example-name manifest (tests/fixtures/pyltspice_example_manifest.json)
- Mapping coverage for the checked-in README example-name list in that manifest
- End-to-endrun_ltspice_to_csv.pystyle MCP workflow foropampdouble.net

. .venv/bin/activate pytest -q tests/unit/test_responses.py pytest -q tests/unit/test_config.py pytest -q tests/unit/test_dispatcher.py pytest -q tests/unit/test_session.py pytest -q tests/integration/test_mcp_server_integration.py pytest -q tests/integration/test_examples_via_mcp.py pytest -q tests/integration/test_readme_examples_via_mcp.py pytest -q tests/integration/test_run_ltspice_to_csv_via_mcp.py

- runtime_infois immediate and does not requireexecute_statuspolling.
- Server queuesexecutein FIFO per MCP session;stop_resetinterrupts only that session's worker process group and clears its existing queue.
- execute_statuspolls the latest status for queued operations.
- Completion/error notifications are emitted through MCP notification channel.

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