numerical-stability

numerical-stability is a skill for Claude Code from beita6969/ScienceClaw. It costs 61 tokens per session (1,568 once invoked), scanned A, original, MIT.

A checklist and set of analyses for keeping time-dependent partial differential equation simulations numerically stable. Stability means preventing calculation errors from growing until the result becomes unusable.

In plain words
What is it for?
Use it to check CFL and Fourier limits, compare explicit and implicit schemes, analyse waves, and inspect matrix conditioning.
Why use it?
It helps detect unsafe time steps, poor matrix conditioning, and unstable choices of numerical scheme before a simulation blows up.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Use it to check CFL and Fourier limits, compare explicit and implicit schemes, analyse waves, and inspect matrix conditioning.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/beita6969/scienceclaw/numerical-stability
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add beita6969/ScienceClaw --skill numerical-stability
Clone the repo
git clone --depth 1 https://github.com/beita6969/ScienceClaw

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for numerical-stability

README.md
[![agentmods](https://agentmods.dev/badge/skills/beita6969/scienceclaw/numerical-stability/github.svg)](https://agentmods.dev/skills/beita6969/scienceclaw/numerical-stability)
Your own site
<a href="https://agentmods.dev/skills/beita6969/scienceclaw/numerical-stability"><img src="https://agentmods.dev/badge/skills/beita6969/scienceclaw/numerical-stability/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for numerical-stability

Your own site · 80×15
<a href="https://agentmods.dev/skills/beita6969/scienceclaw/numerical-stability"><img src="https://agentmods.dev/badge/skills/beita6969/scienceclaw/numerical-stability.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,568 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 $0.00061 $0.01568
Opus 5 $0.00030 $0.00784
Sonnet 5 $0.00012 $0.00314
Haiku 4.5 $0.00006 $0.00157

Measured 5d ago against content hash 8350046ff9c3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

numerical-stability 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 5d ago.

The scan reads SKILL.md. This mod also ships 4 executable files (scripts/cfl_checker.py, scripts/matrix_condition.py, scripts/stiffness_detector.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/numerical-stability/SKILL.md · 150 lines

How it starts

The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Numerical Stability

Goal

Provide a repeatable checklist and script-driven checks to keep time-dependent simulations stable and defensible.

Requirements

  • Python 3.8+
  • NumPy (for matrix_condition.py and von_neumann_analyzer.py)
  • See scripts/requirements.txt for dependencies

Inputs to Gather

Input Description Example
Grid spacing dx Spatial discretization 0.01 m
Time step dt Temporal discretization 1e-4 s
Velocity v Advection speed 1.0 m/s
Diffusivity D Thermal/mass diffusivity 1e-5 m²/s
Reaction rate k First-order rate constant 100 s⁻¹
Dimensions 1D, 2D, or 3D 2
Scheme type Explicit or implicit explicit

Decision Guidance

Choosing Explicit vs Implicit

Is the problem stiff (fast + slow dynamics)?
├── YES → Use implicit or IMEX scheme
│         └── Check conditioning with matrix_condition.py
└── NO → Is CFL/Fourier satisfied with reasonable dt?
    ├── YES → Use explicit scheme (cheaper per step)
    └── NO → Consider implicit or reduce dx

Stability Limit Quick Reference

Physics Number Explicit Limit (1D) Formula
Advection CFL C ≤ 1 C = v·dt/dx
Diffusion Fourier Fo ≤ 0.5 Fo = D·dt/dx²
Reaction Reaction R ≤ 1 R = k·dt

Multi-dimensional correction: For d dimensions, diffusion limit is Fo ≤ 1/(2d).

Script Outputs (JSON Fields)

Script Key Outputs
scripts/cfl_checker.py metrics.cfl, metrics.fourier, recommended_dt, stable
scripts/von_neumann_analyzer.py results.max_amplification, results.stable
scripts/matrix_condition.py results.condition_number, results.is_symmetric
scripts/stiffness_detector.py results.stiffness_ratio, results.stiff, results.recommendation

Workflow

  1. Identify dominant physics (advection vs diffusion vs reaction)
  2. Run CFL checker with scripts/cfl_checker.py
  3. Compare to limits and adjust dt if needed
  4. Check stiffness with scripts/stiffness_detector.py if multiple scales
  5. Analyze custom schemes with scripts/von_neumann_analyzer.py
  6. Check conditioning with scripts/matrix_condition.py for implicit solves
  7. Document the stability verdict and recommended time step

Read the full file on GitHub · 150 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. 5d ago First seen · 150 lines · 61 tokens per session scan A 8350046ff9c3

Subscribe to this mod's changes

numerical-stability is a skill published in the GitHub repository beita6969/ScienceClaw (896 stars, last pushed 3mo ago), licensed MIT. It adds 61 tokens to every session and 1,568 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 2026-09-03.

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