neqsim: Skill for Claude Code

.github/skills/neqsim-dynamic-equipment-implementation/SKILL.md

neqsim-dynamic-equipment-implementation is a skill for Claude Code, Codex from equinor/neqsim. It costs 60 tokens per session (2,718 once invoked), scanned A, original, Apache-2.0.

A Java development guide for adding transient simulation to NeqSim process equipment. Transient simulation models how equipment changes over time instead of calculating only a steady operating point.

In plain words
What is it for?
Use it when implementing pressure, level, temperature, inventory, or controller behavior in equipment, and when adding JUnit tests for those time-based changes.
Why use it?
It helps equipment behave correctly during timestep-based simulations instead of falling back to steady-state behavior or reporting that transient operation is unsupported.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

This is equinor/neqsim's own configuration. It tells Claude Code and Codex how to work on neqsim itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything neqsim configures →

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is python devtools/verify_skills_agents.py.

Reuse

Borrowing it

Nothing to install: this file belongs to equinor/neqsim. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/equinor/neqsim/master/.github/skills/neqsim-dynamic-equipment-implementation/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim

Made for: Claude Code, Codex.

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Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,718 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00060 $0.02718
Opus 5 $0.00030 $0.01359
Sonnet 5 $0.00012 $0.00544
Haiku 4.5 $0.00006 $0.00272

Measured yesterday against content hash b578aa0617fe, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

neqsim-dynamic-equipment-implementation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/skills/neqsim-dynamic-equipment-implementation/SKILL.md · 193 lines

How it starts

The opening of the file, as written. The whole thing — 193 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Dynamic Equipment Implementation

Use this skill when a NeqSim equipment class needs real dynamic simulation support instead of the default steady-state fallback or unsupported transient behavior.

This complements neqsim-dynamic-simulation, which explains how to run dynamic studies. This skill explains how to implement and test the Java code that makes equipment participate correctly in ProcessSystem.runTransient(dt, id).

Local Architecture

  • SimulationInterface.runTransient(double dt, UUID id) defaults to steady-state run(id) when getCalculateSteadyState() is true, otherwise throws UnsupportedOperationException.
  • ProcessSystem.runTransient(dt, id) steps each ProcessEquipmentInterface through a skip-aware wrapper and calls unit.runTransient(dt, id).
  • Equipment that has real dynamic behavior must override runTransient(double dt, UUID id).
  • Existing reference implementations include Separator, ThreePhaseSeparator, Tank, Compressor, ThrottlingValve, SafetyValve, BlowdownValve, PipeBeggsAndBrills, WaterHammerPipe, SimpleReservoir, and WellFlow.
  • All dynamic equipment code must remain Java 8 compatible, use Log4j2 for logging, and pass Spotless formatting.

Implementation Decision Tree

  1. Is the equipment purely algebraic?

    • Examples: simple pressure drop, splitter ratio, ideal heater with no metal/fluid holdup.
    • Implement only if needed to propagate controller or actuator dynamics; otherwise the steady-state fallback may be sufficient.
  2. Does the equipment hold mass or energy inventory?

    • Examples: separator, tank, column tray/section, adsorber bed, exchanger volume, pipe segment, reactor, accumulator.
    • Add explicit volume/holdup state and integrate component moles and internal energy over dt.
  3. Does the equipment have actuator or mechanical state?

    • Examples: compressor shaft speed, valve opening, pump ramp, fan speed, bed switching, recycle valve position.
    • Add bounded state variables, ramp-rate limits, and controller hooks.

Read the full file on GitHub · 193 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday Changed · +59 lines b578aa0617fe
  2. 9d ago First seen · 134 lines · 60 tokens per session scan A 2b3aaf97257c

Subscribe to this mod's changes

neqsim-dynamic-equipment-implementation is a skill published in the GitHub repository equinor/neqsim (151 stars, last pushed today), licensed Apache-2.0. It adds 60 tokens to every session and 2,718 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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