design-patterns-behavioral

design-patterns-behavioral is a skill for Claude Code, Codex from mickeyyaya/refactoring-skills. It costs 40 tokens per session (3,136 once invoked), scanned A, original, MIT.

A code-review guide to behavioral design patterns, which organize how objects communicate and share responsibility.

In plain words
What is it for?
Use it when reviewing handlers, commands, iterators, mediators, undo-style state handling, notification systems, or large type-based conditionals.
Why use it?
It helps uncover tangled conditions, tightly connected objects, duplicated algorithms, and fragile event wiring.

Skill for Claude CodeCodex

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

Good fit Use it when reviewing handlers, commands, iterators, mediators, undo-style state handling, notification systems, or large type-based conditionals.

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Install with agentmods
npx agentmods add skills/mickeyyaya/refactoring-skills/design-patterns-behavioral
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 mickeyyaya/refactoring-skills --skill design-patterns-behavioral
Clone the repo
git clone --depth 1 https://github.com/mickeyyaya/refactoring-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

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README.md
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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.

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Your own site · 80×15
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Per session 40 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,136 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 $0.00040 $0.03136
Opus 5 $0.00020 $0.01568
Sonnet 5 $0.00008 $0.00627
Haiku 4.5 $0.00004 $0.00314

Measured 10d ago against content hash 702f064c923a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

design-patterns-behavioral 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 10d 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/design-patterns-behavioral/SKILL.md · 320 lines

How it starts

The opening of the file, as written. The whole thing — 320 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Design Patterns: Behavioral

Overview

Behavioral patterns address how objects communicate and distribute responsibility. They replace tangled conditional logic, tight coupling, and ad-hoc event wiring with well-named structures. Recognizing which pattern is — or should be — present is a core code review skill.

When to Use

  • Large switch/if-else blocks branching on type or state
  • Tightly coupled objects calling each other in every direction
  • Duplicated algorithm logic with only small steps varying
  • Event/notification systems needing correctness and scalability review

Quick Reference

Pattern Core Problem Solved Key Red Flag
Chain of Responsibility Decouple sender from receiver; multiple handlers Hardcoded handler cascade in caller
Command Encapsulate request as object; undo/queue Method calls not storable or reversible
Iterator Uniform traversal without exposing internals Callers access internal array fields directly
Mediator Replace many-to-many with central coordinator Objects holding refs to many unrelated peers
Memento Save/restore state without breaking encapsulation Caller copies internal fields for undo
Observer Notify dependents of state changes automatically Producer manually calls every consumer
State Object changes behavior as state changes Giant switch (this.state) in multiple methods
Strategy Interchangeable algorithms at runtime if (type === 'A') algoA() else algoB()
Template Method Fix algorithm structure; vary steps Copy-pasted algorithm with 1-2 lines differing
Visitor Add operations without modifying hierarchy New instanceof branch per operation
Interpreter Evaluate sentences in a simple grammar Ad-hoc string parsing scattered across codebase

Behavioral Patterns

1. Strategy (most commonly applied)

Intent: Define a family of algorithms, encapsulate each one, and make them interchangeable.

Read the full file on GitHub · 320 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. 10d ago First seen · 320 lines · 40 tokens per session scan A 702f064c923a

Subscribe to this mod's changes

design-patterns-behavioral is a skill published in the GitHub repository mickeyyaya/refactoring-skills (6 stars, last pushed 5mo ago), licensed MIT. It adds 40 tokens to every session and 3,136 once invoked, about $0.0002 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 2026-08-31.