What is crossbus CLAUDE.md?

Instructions for using CrossBus, a library for sending messages between browser frames, web workers, tabs, and WebSockets. They include examples for broadcasting events, making requests, handling messages, and configuring secure production connections.

Use them to add cross-context messaging, remote procedure calls, event listeners, transports, health checks, and cleanup.

They give an agent ready-to-use patterns for connecting separate parts of an application and avoiding unsafe production settings.

How GiuseppeScottoLavina/crossbus configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to GiuseppeScottoLavina/crossbus. 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/GiuseppeScottoLavina/crossbus/master/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/GiuseppeScottoLavina/crossbus

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/giuseppescottolavina/crossbus/claude-md/github.svg)](https://agentmods.dev/instructions/giuseppescottolavina/crossbus/claude-md)

Your own site

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

Per session 758 This file is loaded in full into every session.

When invoked 758 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	$0.00758	$0.00758
Opus 5.5	$0.00303	$0.00303
Sonnet 5.5	$0.00152	$0.00152
Haiku 4.5	$0.00076	$0.00076

Measured 2mo ago against content hash d0d297b9abb1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

crossbus 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 · 122 lines

How it starts

The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CLAUDE.md - Instructions for Claude/Anthropic Agents

For Claude and Anthropic AI models: Copy-paste ready patterns for CrossBus.

TL;DR

CrossBus = cross-context messaging (iframes, workers, tabs, WebSocket).

// Hub (orchestrator)
import { CrossBus } from 'crossbus';
const hub = new CrossBus({ isHub: true, peerId: 'hub', allowedOrigins: ['*'] });

// Agent (spoke in iframe/worker)
const agent = new CrossBus({ peerId: 'agent-1', allowedOrigins: ['*'] });

🚀 Production Setup (Use This!)

// ALWAYS use createSecure() for production
const hub = CrossBus.createSecure({
  peerId: 'production-hub',
  isHub: true,
  allowedOrigins: ['https://your-domain.com']
});
// Enforces: strictMode, maxPayloadSize, maxPendingRequests

📋 Core API Cheatsheet

Task	Code
Broadcast to all	`bus.signal('event', data)`
RPC to peer	`await bus.request('peerId', 'handler', data)`
Register handler	`bus.handle('name', (payload) => result)`
Listen to signals	`bus.on('event', (e) => process(e.data))`
Add transport	`bus.addTransport(transport, {peerId: 'remote'})`
Check health	`bus.healthCheck()`
Cleanup	`bus.destroy()`

🔌 Transports

Transport	Use Case	Code
PostMessage	iframe ↔ parent	`new PostMessageTransport(window.parent)`
BroadcastChannel	tab ↔ tab	`new BroadcastChannelTransport('channel')`
WebSocket	browser ↔ server	`new WebSocketTransport({url: 'ws://...'})`

🛡️ Security Options

bus.handle('sensitiveAction', handler, {
  allowedPeers: ['trusted-agent'],  // Whitelist
  rateLimit: 10,                    // Max calls/sec
  validatePayload: (p) => p.id != null
});

🔍 Schema Validation

import { withSchemaValidation } from 'crossbus/plugins/schema-validation';

const schema = {
  type: 'object',
  required: ['name'],
  properties: { name: { type: 'string' } }
};

bus.handle('createUser', withSchemaValidation(schema, async (p) => {
  // p is pre-validated!
}));

Read the full file on GitHub · 122 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 · 122 lines · 758 tokens per session scan A d0d297b9abb1

Subscribe to this mod's changes

crossbus CLAUDE.md is an instructions file published in the GitHub repository GiuseppeScottoLavina/crossbus (5 stars, last pushed 7mo ago), licensed Apache-2.0. It adds 758 tokens to every session, about $0.0030 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.

Backend and APIs ai-agents broadcast-channel cross-origin event-emitter iframe

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