What is effect-solutions CLAUDE.md?

Repository instructions for Effect Solutions, a documentation website and command-line tool containing guidance and patterns for the Effect programming ecosystem. They describe the project structure, local reference repositories, development commands, and generated Open Graph images.

Use them to run the documentation site or CLI, check and format the code, run tests, and rebuild social-preview images.

They show contributors where the website, command-line tool, and reference code live, and which commands maintain them.

How kitlangton/effect-solutions configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to kitlangton/effect-solutions. 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/kitlangton/effect-solutions/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/kitlangton/effect-solutions

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/kitlangton/effect-solutions/claude-md/github.svg)](https://agentmods.dev/instructions/kitlangton/effect-solutions/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/kitlangton/effect-solutions/claude-md"><img src="https://agentmods.dev/badge/instructions/kitlangton/effect-solutions/claude-md/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/kitlangton/effect-solutions/claude-md"><img src="https://agentmods.dev/badge/instructions/kitlangton/effect-solutions/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 1,873 This file is loaded in full into every session.

When invoked 1,873 The same file — it is already loaded in full.

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.

Model	Per session	Once invoked
Fable 5.1	$0.01873	$0.01873
Opus 5.5	$0.00749	$0.00749
Sonnet 5.5	$0.00375	$0.00375
Haiku 4.5	$0.00187	$0.00187

Measured 2mo ago against content hash b24ee1d3b86f, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

effect-solutions CLAUDE.md 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 2mo 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.

CLAUDE.md · 221 lines

How it starts

The opening of the file, as written. The whole thing — 221 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Effect Solutions

Effect best practices and patterns for humans and AI agents — https://www.effect.solutions

Living Document: This is an opinionated collection exploiting Cunningham's Law ("the best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer"). Disagree with a recommendation? Think we should cover something? Open an issue

Project Structure

packages/website/ - Documentation site (Next.js)
packages/cli/ - CLI for local docs access
.github/workflows/ - Automated validation & bots

Quick Links

Website: https://www.effect.solutions
CLI: bunx effect-solutions@latest list

Local Reference Repos

Effect core monorepo (source for @effect/*, including @effect/vitest / it.layer): /Users/kit/code/effectful/repos/effect

Development

bun install          # Install dependencies
bun run dev          # Website dev server
bun run dev:cli      # CLI dev mode
bun run check        # Biome (writes), tsc --build, tests
bun --cwd packages/website run format  # Format website/docs
bun --cwd packages/website run generate:og  # Rebuild Open Graph images

Open Graph Images

The Playwright generator lives at packages/website/scripts/generate-og.ts and renders the static template in packages/website/src/app/og/template/page.tsx. Run bun --cwd packages/website run generate:og to refresh every image (or OG_ONLY=slug1,slug2 bun --cwd packages/website run generate:og to target a subset). The resulting PNGs are written to packages/website/public/og/ and referenced automatically in the Next.js metadata.

Changesets & Publishing

bun scripts/changeset-named.ts "description"  # Create named changeset
bun release                                    # Version + tag packages, push tags for CI publish

Creating changesets:

Use bun scripts/changeset-named.ts "fix audio overlap" to create descriptive changeset files
Avoids random names like "purple-olives-look.md"
Script prompts for package selection and change type interactively
Resulting file: .changeset/fix-audio-overlap.md

Read the full file on GitHub · 221 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.

2mo ago First seen · 221 lines · 1,873 tokens per session scan A b24ee1d3b86f

Subscribe to this mod's changes

effect-solutions CLAUDE.md is an instructions file published in the GitHub repository kitlangton/effect-solutions (463 stars, last pushed 6mo ago), licensed MIT. It adds 1,873 tokens to every session, about $0.0075 per session on Opus 5.5. 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.

Languages TypeScript Writing and docs

effect-solutions CLAUDE.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
effect-solutions CLAUDE.mdkitlangton/effect-solutions	Instructions file	463	6mo ago	MIT	A	1,873	Claude Code
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	9,719	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	today	MIT	A	7,461	Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	yesterday	MIT	A	4,680	Codex, OpenCode
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	5,516	GitHub Copilot
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	yesterday	MIT	A	3,093	GitHub Copilot
deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness	Instructions file	274k	2d ago	MIT	A	4,313	Codex, OpenCode

effect-solutions: Instructions file for Claude Code