agentviewer

agentviewer

A localhost web server that allows AI agents (Claude Code, etc.) to display rich content to users in a browser.

Features

• Tabbed browser interface for viewing multiple documents
• Markdown with GitHub Flavored Markdown, Mermaid diagrams, and LaTeX math
• Code with syntax highlighting (180+ languages)
• Diffs with side-by-side comparison view
• Live updates via WebSocket - content updates instantly in the browser
• REST API for programmatic control by AI agents

┌─────────────────┐    WebSocket     ┌─────────────────┐
│  Browser Tab    │◄────────────────►│   agentviewer   │
│  (localhost)    │                  │   HTTP Server   │
└─────────────────┘                  └────────▲────────┘
                                             │ REST API (curl)
                                    ┌────────┴────────┐
                                    │  Claude / Agent │
                                    └─────────────────┘

Installation

macOS (Homebrew)

brew install pengelbrecht/tap/agentviewer

Windows (Scoop)

scoop bucket add agentviewer https://github.com/pengelbrecht/scoop-agentviewer
scoop install agentviewer

Windows (Winget)

winget install pengelbrecht.agentviewer

Note: Winget package pending submission to winget-pkgs repository.

Windows (Binary)

Download from GitHub Releases:

# Download and add to PATH
Invoke-WebRequest -Uri "https://github.com/pengelbrecht/agentviewer/releases/latest/download/agentviewer-windows-amd64.exe" -OutFile "$env:LOCALAPPDATA\agentviewer.exe"
$env:PATH += ";$env:LOCALAPPDATA"

Or download agentviewer-windows-amd64.exe manually and add to your PATH.

Linux (apt/deb - Debian, Ubuntu)

# Download and install .deb package
curl -LO https://github.com/pengelbrecht/agentviewer/releases/latest/download/agentviewer_$(uname -m | sed 's/x86_64/amd64/' | sed 's/aarch64/arm64/').deb
sudo dpkg -i agentviewer_*.deb

Linux (rpm - Fedora, RHEL, CentOS)

# Download and install .rpm package
curl -LO https://github.com/pengelbrecht/agentviewer/releases/latest/download/agentviewer_$(uname -m).rpm
sudo rpm -i agentviewer_*.rpm

macOS/Linux (Binary)

Download the latest release for your platform:

# Detect platform and download
curl -L "https://github.com/pengelbrecht/agentviewer/releases/latest/download/agentviewer-$(uname -s | tr '[:upper:]' '[:lower:]')-$(uname -m | sed 's/x86_64/amd64/' | sed 's/aarch64/arm64/')" -o agentviewer
chmod +x agentviewer
sudo mv agentviewer /usr/local/bin/

Or download manually from GitHub Releases.

Available binaries:

• agentviewer-darwin-arm64 - macOS Apple Silicon (M1/M2/M3)
• agentviewer-darwin-amd64 - macOS Intel
• agentviewer-linux-amd64 - Linux x86_64
• agentviewer-linux-arm64 - Linux ARM64
• agentviewer-windows-amd64.exe - Windows x86_64

Available packages (version-less for stable URLs):

• agentviewer_amd64.deb / agentviewer_arm64.deb - Debian/Ubuntu
• agentviewer_x86_64.rpm / agentviewer_aarch64.rpm - Fedora/RHEL

Go Install

If you have Go 1.22+ installed:

go install github.com/pengelbrecht/agentviewer@latest

From Source

git clone https://github.com/pengelbrecht/agentviewer
cd agentviewer
make install

This installs to $GOBIN (usually ~/go/bin). Ensure this is in your PATH.

Verify Installation

agentviewer --version
agentviewer serve --help

Quick Start

1. Start the server (opens browser automatically):

   agentviewer serve --open
   

2. Create content via API:

   curl -X POST http://localhost:3333/api/tabs \
     -H "Content-Type: application/json" \
     -d '{"title": "Hello", "type": "markdown", "content": "# Hello World\n\nThis is **bold** text."}'
   

3. View in browser at http://localhost:3333

Usage

Command Line

# Start server (foreground, blocks)
agentviewer serve

# Start server and open browser
agentviewer serve --open

# Custom port
agentviewer serve --port 4000

# Start with initial file
agentviewer serve --open README.md

REST API

Base URL: http://localhost:3333/api

Method	Endpoint	Description
POST	/api/tabs	Create or update a tab
GET	/api/tabs	List all tabs
GET	/api/tabs/:id	Get tab content
DELETE	/api/tabs/:id	Delete a tab
DELETE	/api/tabs	Delete all tabs
POST	/api/tabs/:id/activate	Switch to a tab
GET	/api/status	Server status

API Examples

Create markdown tab:

curl -X POST localhost:3333/api/tabs \
  -d '{"title": "Notes", "type": "markdown", "content": "# My Notes\n\n- Item 1\n- Item 2"}'