Simulink automation

Unified skill for all Simulink CLI operations (read-only analysis and parameter editing). Canonical skill name is simulink-automation (module path simulink_cli is internal only). This skill belongs to plugin simulink-automation-suite.

Prerequisites

• MATLAB Engine for Python installed in the active Python environment.
• A shared MATLAB session started via matlab.engine.shareEngine in MATLAB.

Discovery

Call schema to get the full runtime contract (actions, fields, types, defaults, error codes):

python -m simulink_cli schema
python -m simulink_cli --json '{"action":"schema"}'

Schema output is the authoritative reference for command syntax. Do not rely on static docs for field names or types.

Workflow Strategy

1. Discover — list_opened to see available models; session list if multiple MATLAB sessions exist.
2. Quick lookup — inspect with a specific target and specific param for single-value checks; highlight for visual location.
3. Deep analysis — delegate to simulink-analyzer agent (see Responsibility & Handoff).
4. Modify — set_param with dry-run preview before any write; block_add for placing new blocks (note: some library source paths contain literal newlines — use JSON \n escape, common in SPS libraries); line_add for connecting ports (supports both numeric signal ports and physical port names like LConn1/RConn1 for SPS connections); line_delete to remove a signal connection; block_delete to remove a block (also silently removes connected lines). See Write Safety Model below.
5. Simulate — simulate to run the model simulation after the modeling workflow is complete.
6. Update — model_update to compile/update diagram after structural changes.
7. Verify — inspect the target after write to confirm the change took effect.
8. Finalize — model_save then model_close when done.

Both single-param (param/value) and multi-param (params object) modes available. Always read and understand the model before modifying.

Responsibility & Handoff

This skill and the simulink-analyzer agent have non-overlapping responsibilities.

Direct Handling (this skill)

The following actions are handled directly without dispatching the agent:

Action	Reason
session (list/current/use/clear)	Meta-query; main agent needs session context for dispatch decisions
list_opened	Meta-query; main agent needs model list for dispatch decisions
schema	Self-discovery; main agent may need the action catalog
highlight	UI side-effect; no analysis output to isolate
inspect (specific target + specific param)	Single-value response; main agent needs the value in context
set_param	Write operation; requires user interaction for safety
model_new / model_open / model_save	Write/lifecycle operations
model_close / model_update	Lifecycle operations; direct execution
block_add	Write operation; structural mutation
line_add	Write operation; signal routing
line_delete	Write operation; signal disconnection
block_delete	Write operation; structural removal (also removes connected lines)
simulate	Operational; runs model simulation
matlab_eval	Operational; executes arbitrary MATLAB code

Delegate to simulink-analyzer agent

The following actions are delegated to the analyzer agent for context isolation:

Action	Reason
scan (any configuration)	Topology output; potentially large
find (any criteria)	Search results; potentially large
connections (any configuration)	Connection graph; potentially large
inspect (no specific param or param=All)	Full parameter list; potentially large
Multi-step read analysis workflows	Workflow-level context isolation

Before dispatching, resolve session and model via direct session current or list_opened, then provide them explicitly to the agent.

Delegate to sim-analyst agent

Action	Reason
Post-simulation signal analysis	Waveform data can be millions of points; isolate from main context
Dynamic performance evaluation	Rise time, overshoot, settling time, steady-state error
Multi-signal comparison	Cross-correlation, phase analysis

Before dispatching, ensure simulate has been run (so sl_sim_result exists in workspace). Provide session, model, and specific analysis goals.

Composite Requests

When a user request involves both analysis and modification (e.g., "check the PID parameters, then set Kp to 2.0"):

1. Dispatch the simulink-analyzer agent for the analysis portion first.
2. Use the analysis results to execute the write workflow directly via this skill.

Always analyze before writing. Never combine analysis delegation and write execution in a single step.

Write Safety Model

All writes go through a guarded preview-execute-verify cycle:

1. Preview — set_param defaults to dry_run=true. Returns current_value, proposed_value, apply_payload, and rollback.
2. Execute — Replay the returned apply_payload verbatim in JSON mode. It carries expected_current_value as a precondition guard.
3. Verify — Check the verified field in the response. If false, investigate before proceeding.
4. Rollback — Use the rollback payload from any response to restore the prior value.

If the model changed between preview and execute, precondition_failed is returned without writing. If read-back fails, verification_failed is returned with rollback and write-state data.

For response shape examples, see reference.md.

Recovery Routing

Error-driven next actions (consult schema for the full error code list):

Error	Recovery
engine_unavailable	Install/configure MATLAB Engine for Python, retry
no_session	Run matlab.engine.shareEngine in MATLAB, retry
session_required	session list → session use <name> or pass --session
session_not_found	session list → copy exact name, retry
model_required	list_opened → retry with explicit --model
model_not_found	list_opened → open or create the model first
block_not_found	scan or find to locate valid block path
param_not_found	inspect --param All to list available parameters
subsystem_not_found	Shallow root scan → select valid subsystem
inactive_parameter	Use --resolve-effective or --strict-active
precondition_failed	Rerun dry-run to refresh, replay new apply_payload
set_param_failed	Inspect target/value constraints; prefer rollback if write may have occurred
verification_failed	Inspect target again or use rollback payload
model_already_loaded	Use a different name or close existing model
model_save_failed	Check file permissions and disk space
source_not_found	Verify library source path; use find to browse available library blocks
block_already_exists	Use a different destination name or inspect existing block
model_dirty	model_save first, or retry with force: true to discard changes
line_already_exists	Check existing connections with connections; use a different port
line_not_found	Verify src/dst block and port names with connections; confirm the line exists before deleting
simulation_failed	Check model for errors with model_update; fix unconnected ports or type mismatches, then retry
update_failed	Check model for errors (unconnected ports, type mismatches); fix with set_param or line_add, retry
eval_failed	Check MATLAB code syntax and referenced variables/functions; retry with corrected code
eval_timeout	Increase timeout or simplify the code; avoid infinite loops
state_write_failed / state_clear_failed	Check plugin state-file permissions or pass explicit --session
invalid_json / json_conflict / unknown_parameter / invalid_input	Correct request payload per schema, retry
find returns empty	Broaden name pattern, try different block_type, widen scope

Common Patterns

Recipes for tasks that combine multiple actions. These patterns use existing CLI capabilities — no additional tools required.

Query Bus Selector signal list

The signal names live in the InputSignals parameter, which is populated only after model compilation:

1. model_update — compile the model diagram.
2. inspect with --target MyModel/BusSel --param InputSignals — returns the comma-separated signal list.

Discover library block paths

Library paths vary by toolbox. block_add auto-loads the library root on first use, so you only need the correct path:

• Standard library: simulink/Math Operations/Gain, simulink/Sources/Step
• SPS / Simscape: powerlib/powergui, spsUniversalBridgeLib/Universal Bridge
• Some paths contain literal newlines: simulink/Signal\nRouting/Mux. In JSON mode use the \n escape.

When source_not_found persists after auto-load, verify the path in MATLAB documentation or via find_system('<library>', 'Type', 'block').

SPS physical connections

SPS (Simscape / Specialized Power Systems) blocks use physical ports (LConn1, RConn1, etc.) instead of numbered signal ports. line_add supports these directly:

{"action": "line_add", "model": "MyModel", "src_block": "DC_Source", "src_port": "LConn1", "dst_block": "Inverter", "dst_port": "LConn1"}

Use connections on a block to discover its physical port names — they appear in physical_neighbors with "type": "physical".

Multi-line MATLAB code via matlab_eval

matlab_eval accepts multi-line code as a single JSON string. Use \n for line breaks in the JSON payload:

{"action": "matlab_eval", "code": "x = 42;\nfprintf('value = %d\\n', x);\ndisp(x)"}

Key points:

• Output is captured via MATLAB evalc — both disp() and fprintf() output appear in the output field.
• MATLAB \n in fprintf format strings must be double-escaped in JSON: \\n (so MATLAB receives \n).
• Use timeout to guard long-running code (default: 30s).

Access simulation results

After simulate runs, the SimulationOutput object is stored in the base workspace as sl_sim_result. Use matlab_eval to query it:

{"action": "matlab_eval", "code": "signals = sl_sim_result.logsout.getElementNames; for i=1:numel(signals), fprintf('%s\\n', signals{i}); end"}

For detailed waveform analysis, dispatch the sim-analyst agent (see Responsibility & Handoff).

Read block port connections

To understand how a block is wired:

1. connections with the block as target — returns upstream/downstream signal edges and physical neighbors.
2. Signal edges carry "type": "signal" with numeric port indices. SPS physical connections carry "type": "physical" and appear in physical_neighbors (direction-agnostic).
3. For port names on masked blocks, inspect --param PortNames or related mask parameters.

Known Limitations

Current CLI capability boundaries. For operations beyond these limits, use direct MATLAB Engine access or run_matlab (when available):

Limitation	Impact	Workaround
No workspace access	Cannot read/write base workspace variables or simulation results.	evalin/assignin via matlab_eval

Output Discipline

• Ground claims in tool JSON output — do not hallucinate parameter values.
• Keep stdout to a single JSON payload; warnings must not leak as raw text.
• Keep outputs compact: selected model, scan root, key findings.
• Do not dump full recursive trees unless explicitly requested.
• JSON mode (--json / --json-file) is first-class and mutually exclusive with flag-mode arguments.
• Both JSON mode and flag mode produce JSON output on stdout. Flag mode is not plain-text — it returns the same JSON envelope as --json.

Related Docs

• Response shape examples: reference.md