class-size

A set of rules for keeping TypeScript files and classes focused and manageable. It recommends splitting files when they combine unrelated responsibilities or become very large.

In plain words
What is it for?
Use it when adding features to large files, extracting helpers or UI parts, reviewing overly broad classes, or organizing registries and rendering code.
Why use it?
Large mixed-purpose files are harder to understand, test, and change safely. These rules help prevent one class or module from becoming a catch-all.

Cursor rule for Cursor

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.

agentmods
npx agentmods add rules/andvolodko/html5-game-editor/class-size
Clone the repo
git clone --depth 1 https://github.com/andvolodko/html5-game-editor

Made for: Cursor.

Per session 36 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 270 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00036 $0.00270
Opus 5 $0.00018 $0.00135
Sonnet 5 $0.00007 $0.00054
Haiku 4.5 $0.00004 $0.00027

Measured 2d ago against content hash 3d62fdad33f8, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

class-size 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 2d 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.

.cursor/rules/class-size.mdc · 25 lines

What it actually says

Class and module size

Prefer modules/classes under ~300 lines when they hold behavior. Treat ~500+ lines or 2+ unrelated responsibility clusters as a required split before adding more features there.

How to split

  1. Extract pure helpers / registries first (no behavior change).
  2. Extract collaboration objects (texture cache, drag controller) with clear ownership.
  3. Keep thin façades (Editor, PixiSceneRenderer) that delegate.

React surfaces: extract hooks / row / menu components when a panel mixes tree + DnD + menus + rename.

Strategy registries (painters, factories, node-type defs, inspector fields): one visual category per file, not one mega-switch. Align splits across visual-componentsschemafactoriespixi-definitionspainters → inspector fields.

Do not

  • Split solely to hit a line count if the module is one coherent algorithm.
  • Move domain logic into React, or renderer objects into serialized scene data.
  • Create circular package deps while extracting.
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. 2d ago First seen · 25 lines · 36 tokens per session scan A 3d62fdad33f8

Subscribe to this mod's changes

class-size is a cursor rule published in the GitHub repository andvolodko/html5-game-editor (5 stars, last pushed 8d ago), licensed MIT. It adds 36 tokens to every session and 270 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.