Sim Cli

sim-cli

You are working in a sim-cli-enabled solver workflow. Use the sim runtime where it adds control and observability, and compose solver-native tools directly where they are the right primitive. This skill carries the cross-solver discipline — the rules that hold across sim-cli workflows, regardless of which solver you drive.

The solver's plugin skill is self-contained for solver-specific work: solver hard constraints, dependency chains, snippets, workflows, SDK/solver notes. It does not depend on loading this skill — but it should stay consistent with the discipline below. If a rule applies to more than one solver, it belongs here, not in a plugin skill.

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Execution models

The plugin skill tells you which model the solver uses. Choose the narrowest correct execution primitive; sim-cli is composable, not a universal wrapper.

| Model | Used by | Lifecycle | |---|---|---| | Persistent session | Drivers that hold a live process open | sim connect → sim exec × N → sim inspect → sim disconnect | | sim-wrapped one-shot batch | Plugin wrappers that add linting, profile-aware invocation, parsing, history, or safer execution | sim check → sim run → parse_output/logs → evaluate | | Native/tool one-shot batch | Ready solver decks/scripts, vendor batch commands, project pipelines, or post-processing tools where native execution is the right primitive | version/profile probe → native command/script → parse artifacts/logs → evaluate |

sim-cli does not try to wrap every solver operation, executable flag, vendor batch mode, or post-processing script. Use sim when it adds a stable control plane: solver discovery and profile checks, live sessions, bounded exec / inspect loops, history/log capture, parsing, screenshots, or shared agent discipline. If the artifact is already a solver-native deck/script and the solver's own batch command is the right execution primitive, call that native command directly instead of forcing it through sim run. Preserve stdout/stderr, generated files, and acceptance evidence just as carefully.

Use sim run when the plugin skill says it is the canonical one-shot path or when the wrapper adds real value. Otherwise, keep the sim-cli discipline while composing the solver's native tools directly.

The loop, any model: classify inputs and get the missing Category A values from the user (including the acceptance criterion) → choose the execution primitive → run a Step-0 version/profile probe (sim inspect session.versions for persistent sessions; sim check , plugin guidance, or native --version / license probe for one-shot work) → execute one bounded step at a time → inspect last.result or parse the native logs/artifacts between steps → evaluate against the acceptance criterion → sim disconnect if a persistent session was opened. On any failure, stop and report — do not silently retry.

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Hard constraints (shared sim-cli discipline)

1. Never invent Category A defaults. Physical decisions — geometry,

materials, boundary conditions, the acceptance criterion — must come from the user. "Just use defaults" / "just run it" does not override this; treat it as a missing input and ask.

1. Step-0 version/profile probe is mandatory. After sim connect, call

sim inspect session.versions and use the returned profile / active_sdk_layer / active_solver_layer to pick the right files in the plugin skill. Before sim run or native one-shot execution, run the relevant probe for that path (sim check , plugin guidance, or the solver's native --version / license check). If a required profile is empty, unknown, or deprecated — stop.

1. Acceptance ≠ exit code. A sim run / sim exec / native solver command

can return success and still be physically wrong. Always validate against an outcome-based, bounded, measurable criterion — not "the solver ran".

1. Never silently retry a failed step. Report stderr, stdout, and

run_count / completion state / relevant artifact state; let the user decide the next move.

1. Reference example values are not defaults. Values in any examples/

directory describe a specific published test case. Offer them explicitly if useful, but wait for the user's confirmation before adopting them.

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Input classification

Every task starts with: which inputs must the user supply, which may I default, which can I derive from the files in front of me?

| Category | Rule | Examples | |---|---|---| | A — physical decisions | Must ask if absent. Non-negotiable. | Geometry, materials, boundary/initial conditions, physics-model choices, the acceptance criterion | | B — operational | May default — must disclose. Affects runtime/convenience, not what the simulation represents. | --processors, --ui-mode, --workspace, smoke-test iteration counts, log verbosity | | C — file-derivable | Infer from the actual files via a diagnostic sim exec, solver-native inspection command, or artifact parser — not from a similar example. Confirm if a downstream decision depends on it. | Mesh cell count, boundary names/types, fields present in a result file, material IDs |

Do not start until every Category A field has an explicit value from the user.

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Where sim serve runs (Windows session-context foot-gun)

If you reach a remote sim host via sim --host or SIM_HOST, how the operator started sim serve changes which drivers actually work. This is purely a Windows concern — Linux and macOS don't isolate display sessions the same way.

| sim serve started from… | Headless / CLI drivers | GUI-capable drivers | |---|---|---| | Logged-in Windows desktop (Windows Terminal / RDP / Task Scheduler "run only when user is logged on" + interactive) | ✅ works | ✅ works — windows are visible; gui can find / click / screenshot them | | SSH session (ssh then sim serve …) | ✅ works | ❌ silent breakage — windows launch in a non-interactive session with no display surface; gui finds zero windows, screenshots come back black |

If the host advertises tools: ["gui"] but gui.find(...) returns nothing for windows you have strong reason to believe exist, do not retry — surface "the server may have been started from a non-interactive session" and ask the operator to restart sim serve from a desktop session. The agent never starts sim serve itself.

See [gui/SKILL.md](gui/SKILL.md) for the full GUI actuation API.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: svd-ai-lab
• Source: svd-ai-lab/sim-cli
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.