What is nexus CLAUDE.md?

Repository instructions for Nexus, an AI router that connects language models to multiple MCP servers, which are services exposing tools and data to AI systems. They define commit-message rules, project terminology, and Rust coding guidance.

Use them when editing Nexus, especially when writing Rust code, describing MCP or routing behavior, and preparing commits.

They give coding agents the domain background and contribution conventions needed to change the router consistently.

How Nexus-Router/nexus configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to Nexus-Router/nexus. 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/Nexus-Router/nexus/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/Nexus-Router/nexus

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/nexus-router/nexus/claude-md/github.svg)](https://agentmods.dev/instructions/nexus-router/nexus/claude-md)

Your own site

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

Per session 5,592 This file is loaded in full into every session.

When invoked 5,592 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	$0.05592	$0.05592
Opus 5.5	$0.02237	$0.02237
Sonnet 5.5	$0.01118	$0.01118
Haiku 4.5	$0.00559	$0.00559

Measured 2mo ago against content hash d6c1758d75cb, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

nexus 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 · 694 lines

How it starts

The opening of the file, as written. The whole thing — 694 lines — stays where its author put it; the contents beside it link to each section on GitHub.

LLM Code Editing Guidelines for Nexus

When editing code in this repository, you are working on Nexus, an AI router that aggregates MCP (Model Context Protocol) servers and LLMs. This system helps reduce tool proliferation by intelligently routing and indexing available tools.

Commit Messages

Follow the Conventional Commits 1.0.0 specification for every commit message.
Use recent commits (git log) as a reference for tone and formatting if you need examples.
Structure messages as type(issue number): subject, where
Common type values include feat, fix, chore, docs, refactor, test, and build; pick the one that best matches the change.
The issue number is a linear issue number, in the format of gb-1234. The user should give you this in the prompt, but if you don't have it, you can ask the user for it.
Keep the subject in the imperative mood, ≤72 characters, and avoid punctuation at the end.

Domain Context

MCP (Model Context Protocol): A protocol for connecting AI models with external tools and data sources
AI Router: Nexus acts as an intelligent intermediary between LLMs and multiple MCP servers
Tool Indexing: Uses Tantivy (full-text search engine) to create searchable indexes of available tools
Dynamic vs Static Tools: Static tools are shared across users; dynamic tools require user authentication

Key Technologies

Rust: The primary programming language
Axum: Web framework for HTTP routing and middleware
Tantivy: Full-text search engine for tool indexing
Tokio: Async runtime
Serde: Serialization/deserialization for JSON/TOML
RMCP: Rust MCP client/server implementation
Anyhow: Error handling with context and backtrace
Reqwest: HTTP client for external API calls
JWT-Compact: JWT token handling for authentication
Tower/Tower-HTTP: Middleware and service layers
Rustls: TLS implementation for secure connections
Insta: Snapshot testing framework
Clap: Command-line argument parsing
Logforth: Structured logging with tracing support
Docker Compose: For integration testing with Hydra OAuth2 server
Governor: Rate limiting with token bucket algorithm
Mini-moka: In-memory caching for rate limit buckets
Redis: Redis support for distributed rate limiting
Deadpool: Connection pooling
OpenTelemetry: Observability with metrics collection and OTLP export

Read the full file on GitHub · 694 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 · 694 lines · 5,592 tokens per session scan A d6c1758d75cb

Subscribe to this mod's changes

nexus CLAUDE.md is an instructions file published in the GitHub repository Nexus-Router/nexus (438 stars, last pushed 7mo ago), licensed MPL-2.0. It adds 5,592 tokens to every session, about $0.0224 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.

ai api large-language-models llmops llms mcp

nexus CLAUDE.md next to 6 instructions from other repositories
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nexus: Instructions file for Claude Code