What is fold CLAUDE.md?

Repository instructions for Fold, a Go gateway that combines multiple MCP tool servers behind one governed endpoint. MCP is a standard way for applications and coding agents to connect to tools.

Building, testing, linting, benchmarking, and checking Fold, while keeping its MCP protocol implementation aligned with the official Go SDK.

They give contributors the correct development and testing commands and describe the gateway's rules for authentication, policies, caching, limits, and auditing.

How fold-run/fold configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to fold-run/fold. 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/fold-run/fold/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/fold-run/fold

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/fold-run/fold/claude-md/github.svg)](https://agentmods.dev/instructions/fold-run/fold/claude-md)

Your own site

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

Per session 2,352 This file is loaded in full into every session.

When invoked 2,352 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	$0.02352	$0.02352
Opus 5.5	$0.00941	$0.00941
Sonnet 5.5	$0.00470	$0.00470
Haiku 4.5	$0.00235	$0.00235

Measured 2mo ago against content hash dc19ea928b45, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

fold 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 · 64 lines

How it starts

The opening of the file, as written. The whole thing — 64 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

What this is

This repo is fold, the enterprise MCP gateway — one governed endpoint federating any number of upstream MCP servers into a single virtual server, adding auth, policy, caching, rate limiting, and audit. Single Go module; the Makefile is a thin wrapper over the Go toolchain and is the source of truth for dev/CI commands. The wire protocol (streamable HTTP, request/response and SSE) is the official MCP Go SDK's implementation on both the client-facing and upstream-facing sides — fold never hand-rolls protocol framing.

Commands

make build
make test                                    # unit + integration (real SDK client/server fixtures)
make race                                    # what CI runs
make lint                                    # golangci-lint (config in .golangci.yml)
make check                                   # fmt-check + tidy-check + vet + build + race + lint

go test ./gateway -run TestName -v           # one test
make bench                                   # latency gate (FOLD_BENCH=1; skipped without it)
make conformance                             # official MCP conformance suite through the gateway (needs node/npx)

# Federation cost — the list path, whose work scales with federation size and
# which the latency gate's 1-upstream fixture does not exercise:
go test ./gateway -run '^$' -bench BenchmarkFederatedListTools -benchmem
FOLD_LOAD_UPSTREAMS=20 FOLD_LOAD_TOOLS=50 make loadtest

# Tenant resolution cost, whose work scales with the number of tenant
# declarations rather than with the federation:
go test ./gateway -run '^$' -bench BenchmarkResolveTenant -benchmem

CI (.github/workflows/ci.yml) gates every merge on: gofmt, go mod tidy -diff, vet, build, go test -race, golangci-lint, govulncheck, the added-latency benchmark (added p50 < 5 ms through the proxy path), and the conformance suite (40/40 checks, pinned to a commit in scripts/conformance.sh — bump deliberately).

Read the full file on GitHub · 64 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 Changed · +22 tokens per session dc19ea928b45
2mo ago First seen · 64 lines · 2,330 tokens per session scan A e15a8a548957

Subscribe to this mod's changes

fold CLAUDE.md is an instructions file published in the GitHub repository fold-run/fold (1 stars, last pushed 12d ago), licensed Apache-2.0. It adds 2,352 tokens to every session, about $0.0094 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 2026-08-31.

Go Planning ai api-gateway federation gateway go

fold CLAUDE.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
fold CLAUDE.mdfold-run/fold	Instructions file	1	12d ago	Apache-2.0	A	2,352	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	yesterday	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

fold: Instructions file for Claude Code