solid

solid is a skill for Claude Code from krzysztofsurdy/code-virtuoso. It costs 99 tokens per session (1,298 once invoked), scanned A, original, MIT.

A guide to five principles for organising object-oriented code: keeping each class focused, limiting dependencies, and making components easier to replace or extend. It includes examples in PHP, Java, Python, TypeScript, and C++.

In plain words
What is it for?
Use it to review classes, find SOLID violations, reduce coupling, and make code easier to test or extend.
Why use it?
It helps identify designs where one change affects many unrelated parts, code breaks unexpectedly, or components are too intertwined to reuse. It gives names and rules for reducing those problems.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the knowledge-virtuoso plugin — 15 skills shipped together

Good fit Use it to review classes, find SOLID violations, reduce coupling, and make code easier to test or extend.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/krzysztofsurdy/code-virtuoso/solid
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 krzysztofsurdy/code-virtuoso --skill solid
Clone the repo
git clone --depth 1 https://github.com/krzysztofsurdy/code-virtuoso

Made for: Claude Code.

Or install knowledge-virtuoso, the plugin that ships this one along with the rest of its 15 skills.

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 solid

README.md
[![agentmods](https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/solid.svg)](https://agentmods.dev/skills/krzysztofsurdy/code-virtuoso/solid)
Your own site
<a href="https://agentmods.dev/skills/krzysztofsurdy/code-virtuoso/solid"><img src="https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/solid.svg" alt="Measured on agentmods" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,298 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.
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 $0.00099 $0.01298
Opus 5 $0.00049 $0.00649
Sonnet 5 $0.00020 $0.00260
Haiku 4.5 $0.00010 $0.00130

Measured 7d ago against content hash ce0931039ca8, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

solid 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 7d ago.

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/knowledge/solid/SKILL.md · 131 lines

How it starts

The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SOLID Principles

Five core principles of object-oriented design that lead to systems which are simpler to maintain, test, and extend. Robert C. Martin (Uncle Bob) formalized these ideas, and Michael Feathers coined the SOLID acronym.

Principle Index

Principle Summary Reference
S — Single Responsibility A class should have only one reason to change reference
O — Open/Closed Open for extension, closed for modification reference
L — Liskov Substitution Subtypes must be substitutable for their base types reference
I — Interface Segregation Prefer many specific interfaces over one general-purpose interface reference
D — Dependency Inversion Depend on abstractions, not concretions reference

Why SOLID Matters

Without SOLID, codebases gradually develop these problems:

  • Rigidity — one change ripples through many unrelated modules
  • Fragility — modifying one area breaks another seemingly unconnected area
  • Immobility — components are so intertwined that extracting them for reuse is impractical
  • Viscosity — doing things correctly is harder than hacking around the design

SOLID tackles each of these by defining clear boundaries, explicit contracts, and flexible points for extension.

Quick Decision Guide

Symptom Likely Violated Principle Fix
Class does too many things SRP Split into focused classes
Adding a feature requires editing existing classes OCP Introduce polymorphism or strategy
Subclass breaks when used in place of parent LSP Fix inheritance hierarchy or use composition
Classes forced to implement unused methods ISP Break interface into smaller ones
High-level module imports low-level details DIP Introduce an abstraction layer

Quick Examples

SRP — Before and After

Read the full file on GitHub · 131 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 7d ago First seen · 131 lines · 99 tokens per session scan A ce0931039ca8

Subscribe to this mod's changes

solid is a skill published in the GitHub repository krzysztofsurdy/code-virtuoso (20 stars, last pushed 3mo ago), licensed MIT. It adds 99 tokens to every session and 1,298 once invoked, about $0.0005 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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