Correspondents/CLAUDE.md

CLAUDE.md

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

Project Overview

Multi-agent chat interface deployed to Cloudflare Workers. Users select from configured AI agents and chat with them through n8n webhooks. The interface features a glass-morphism design with mobile support, markdown rendering with code highlighting, and a custom diff visualization tool.

Key Commands

Development

pnpm dev              # Start Next.js dev server at localhost:3000
pnpm build            # Build Next.js application
pnpm lint             # Run ESLint checks
pnpm test             # Run Vitest test suites
pnpm test:ui          # Run tests with Vitest UI
pnpm test:coverage    # Generate test coverage report

Deployment to Cloudflare

npx @opennextjs/cloudflare build  # Convert Next.js build to Cloudflare Workers format
npx wrangler deploy                # Deploy to Cloudflare (requires OpenNext build first)
npx wrangler deploy --env=""       # Deploy to default environment explicitly
npx wrangler tail                  # View live logs from deployed worker

Critical: Always run npx @opennextjs/cloudflare build before deploying. The standard next build alone is insufficient for Cloudflare deployment.

Architecture

Agent Configuration

• Agents are defined via environment variables: AGENT_N_URL, AGENT_N_NAME, AGENT_N_DESCRIPTION (where N = 1, 2, 3...)
• /api/agents dynamically discovers agents by iterating through numbered environment variables
• Each agent has a webhook URL pointing to an n8n workflow
• Agent selection is persisted to localStorage using agent-specific keys

Message Flow

1. User submits message through ChatInterface component
2. POST /api/chat receives message with agentId, sessionId, timestamp, and optional base64 images
3. Route extracts webhook URL from environment variables based on agentId format (agent-N)
4. Message forwarded to n8n webhook with all metadata
5. Response parsed from n8n (supports streaming chunks and diff tool calls)
6. Messages stored in localStorage per agent (chat-messages-{agentId})

Session Management

• Each agent has its own session: chat-session-{agentId} in localStorage
• Session ID format: session-{agentId}-{timestamp}-{random}
• New session created when user clicks "Start a fresh conversation"
• Messages persist across page reloads per agent

Diff Tool Integration

• Custom markdown code fence: ```diff-tool with JSON payload
• n8n can send type: "tool_call", name: "show_diff" which is converted server-side
• MarkdownRenderer parses diff-tool blocks and renders via DiffTool → DiffDisplay components
• Diff props: oldCode, newCode, title, language

Code Structure

API Routes

• src/app/api/agents/route.ts - Discovers and returns configured agents from environment variables
• src/app/api/chat/route.ts - Proxies chat messages to agent webhooks, handles streaming responses and diff tool calls

Core Components

• src/app/page.tsx - Main page with agent selection/persistence and chat interface mounting
• src/components/chat-interface.tsx - Full chat UI: message history, input composer, agent dropdown, image attachments
• src/components/markdown-renderer.tsx - Renders markdown with syntax highlighting and custom diff-tool blocks
• src/components/diff-tool.tsx - Wrapper for diff display functionality
• src/components/diff-display.tsx - Side-by-side diff visualization

Styling

• Tailwind CSS 4.x with custom glass-morphism design system
• Custom colors defined in CSS variables (charcoal, burnt, terracotta, etc.)
• Mobile-specific classes: mobile-shell, mobile-feed, mobile-composer
• Framer Motion for animations and layout transitions

Type Definitions

• src/lib/types.ts - All TypeScript interfaces for Agent, Message, API requests/responses

Important Patterns

Environment Variable Access

Always extract agent index from agentId before accessing env vars:

const match = agentId.match(/agent-(\d+)/)
const agentIndex = match[1]
const webhookUrl = process.env[`AGENT_${agentIndex}_URL`]

LocalStorage Keys

• Agent selection: selected-agent (full object), selected-agent-id (string)
• Per-agent session: chat-session-{agentId}
• Per-agent messages: chat-messages-{agentId}

Response Parsing in /api/chat

The route handles multiple n8n response formats:

1. Streaming chunks (newline-delimited JSON with type: "item")
2. Tool calls (type: "tool_call", name: "show_diff")
3. Regular JSON with various fields (response, message, output, text)
4. Plain text fallback

Image Handling

• Images converted to base64 via FileReader in browser
• Passed as images: string[] array to /api/chat
• Forwarded to n8n webhook for processing
• Preview thumbnails shown in composer with remove buttons

Deployment Configuration

wrangler.jsonc

• Worker entry: .open-next/worker.js (generated by OpenNext)
• Assets directory: .open-next/assets
• Production route: agents.nicholai.work
• Compatibility flags: nodejs_compat, global_fetch_strictly_public

Build Output

• Standard Next.js build: .next/
• Cloudflare-adapted build: .open-next/ (generated by @opennextjs/cloudflare)
• Only .open-next/ is deployed to Cloudflare

UI/UX Details

Empty State

• Hero greeting animation with per-character stagger
• Agent selection buttons shown prominently
• Sample prompt cards (4 suggestions) users can click to populate input

Composer Behavior

• Auto-expanding textarea (max 224px height)
• Agent dropdown required before sending first message
• Agent selection highlighted if not yet chosen
• Enter to send, Shift+Enter for new line
• Paperclip icon for image attachments

Message Display

• User messages: right-aligned with glass bubble styling
• Assistant messages: markdown-rendered with copy button and syntax highlighting
• Error messages: red text, optional hint field displayed below
• Loading state: animated shimmer bar

Feature Flag System

Architecture

• Flags defined in src/lib/flags.ts with TypeScript interfaces
• Environment variable based: IMAGE_UPLOADS_ENABLED, DIFF_TOOL_ENABLED
• Runtime overrides supported via registerRuntimeFlags() (useful for testing)
• Global caching in globalThis.__MULTI_AGENT_CHAT_FLAGS__
• Client-side access via useFlags() hook that fetches from /api/flags

Available Flags

• IMAGE_UPLOADS_ENABLED (default: true) - Controls image attachment UI and API validation
• DIFF_TOOL_ENABLED (default: true) - Controls diff visualization rendering

Flag Checking Patterns

Server-side (API routes):

import { getFlags } from '@/lib/flags'

const flags = getFlags()
if (!flags.IMAGE_UPLOADS_ENABLED) {
  return NextResponse.json({ error: 'Feature disabled' }, { status: 403 })
}

Client-side (Components):

import { useFlags } from '@/lib/use-flags'

const { flags, isLoading, error } = useFlags()
if (flags.IMAGE_UPLOADS_ENABLED) {
  // Render feature UI
}

Testing:

import { registerRuntimeFlags, resetFlagsCache } from '@/lib/flags'

beforeEach(() => {
  resetFlagsCache()
  registerRuntimeFlags({ IMAGE_UPLOADS_ENABLED: false })
})

Configuration

• Development: Set in .env.local
• Production: Set in wrangler.jsonc under env.production.vars
• Parse format: "true"/"false", "1"/"0", "yes"/"no" (case-insensitive)

Testing

Test Framework

• Vitest 4.0 - Fast unit test framework with Jest-compatible API
• @testing-library/react - React component testing utilities
• jsdom - Browser environment simulation

Test Structure

Tests organized in __tests__/ by domain:

• lib/ - Utility and library tests (flags, types, helpers)
• api/ - API route tests with mocked fetch
• components/ - React component rendering tests
• flags/ - Feature flag integration tests

Running Tests

pnpm test                # Run all tests in watch mode
pnpm test:ui             # Open Vitest UI dashboard
pnpm test:coverage       # Generate coverage report

Test Patterns

API Route Testing:

import { POST } from '@/app/api/chat/route'
import { NextRequest } from 'next/server'

const request = new NextRequest('http://localhost/api/chat', {
  method: 'POST',
  body: JSON.stringify({ message: 'test', agentId: 'agent-1' })
})
const response = await POST(request)

Component Testing:

import { render, screen } from '@testing-library/react'
import { MarkdownRenderer } from '@/components/markdown-renderer'

render(<MarkdownRenderer content="# Hello" />)
expect(screen.getByText('Hello')).toBeInTheDocument()

Flag Behavior Testing:

// Test feature when flag is disabled
process.env.IMAGE_UPLOADS_ENABLED = 'false'
resetFlagsCache()

const response = await POST(requestWithImages)
expect(response.status).toBe(403)

Test Configuration

• Config: vitest.config.ts
• Setup: vitest.setup.ts (mocks window.matchMedia, IntersectionObserver, etc.)
• Path aliases: @/ resolves to ./src/
• Environment: jsdom with globals enabled
• Coverage: v8 provider, excludes node_modules, .next, tests

Important Testing Notes

• Always call resetFlagsCache() in beforeEach when testing flags
• Mock global.fetch for API tests that call webhooks
• Use vi.mock() for module mocking, vi.spyOn() for function spying
• Clean up mocks with vi.clearAllMocks() in beforeEach
• Test both success and error paths for all features

Development Notes

• Next.js 15.5.4 with App Router (all components are Client Components via "use client")
• React 19.1.0 with concurrent features
• Deployed to Cloudflare Workers, not Vercel
• No database - all state in localStorage and n8n workflows
• Mobile-first responsive design with specific mobile breakpoint styling
• Vitest for testing with Testing Library for React components