Claude Code

This guide walks you through setting up Claude Code to work with FastRouter.ai as your API provider.

Introduction

Claude Code is Anthropic's official CLI tool that brings Claude's AI capabilities directly to your terminal and development workflow. It enables you to interact with Claude for coding tasks, file operations, git workflows, and more—all from the command line.

FastRouter.ai is an intelligent AI routing platform that offers access to multiple model providers with a single API, offering cost reduction, improved reliability, and enhanced performance through smart routing algorithms.

By integrating Claude Code with FastRouter.ai, you gain a centralized and enterprise-ready way to operate Claude across your organization. FastRouter acts as the control plane for all usage—allowing you to securely manage and rotate user API keys, standardize access across teams, and eliminate the risks of scattered credentials.

In addition, FastRouter provides built-in observability and governance, giving you clear visibility into usage patterns, spend, and performance. You can enforce rate limits to prevent abuse, define role-based access controls to ensure the right people have the right level of access, and set budgets to keep costs predictable. Together, this integration lets you scale Claude Code safely, efficiently, and with full operational control—without slowing down developers.

Prerequisites

• Linux operating system

• Terminal access

• A FastRouter.ai API key (Get one here)

Installation

Step 1: Install Claude Code

Run the following command in your terminal to install Claude Code on Linux:

curl -fsSL https://claude.ai/install.sh | bash

This will download and install the latest version of Claude Code on your system.

Configuration

Step 2: Navigate to Your Project Directory

Change to the directory where you want to use Claude Code:

cd /path/to/your/project

Step 3: Set Environment Variables

Run the following commands in your terminal to configure Claude Code to use FastRouter.ai:

export ANTHROPIC_BASE_URL="https://api.fastrouter.ai"
export ANTHROPIC_API_KEY=""
export ANTHROPIC_AUTH_TOKEN=[YOUR-FASTROUTER-API-KEY]

Important Notes:

• Replace [YOUR-FASTROUTER-API-KEY] with your actual FastRouter.ai API key

• Setting ANTHROPIC_API_KEY="" (empty string) is required for proper functionality

• These environment variables will only persist for your current terminal session

Step 4: Persist Environment Variables (Optional)

To make these settings permanent across terminal sessions, add them to your shell profile file.

For Bash users (~/.bashrc or ~/.bash_profile):

echo 'export ANTHROPIC_BASE_URL="https://api.fastrouter.ai"' >> ~/.bashrc
echo 'export ANTHROPIC_API_KEY=""' >> ~/.bashrc
echo 'export ANTHROPIC_AUTH_TOKEN=[YOUR-FASTROUTER-API-KEY]' >> ~/.bashrc
source ~/.bashrc

For Zsh users (~/.zshrc):

echo 'export ANTHROPIC_BASE_URL="https://api.fastrouter.ai"' >> ~/.zshrc
echo 'export ANTHROPIC_API_KEY=""' >> ~/.zshrc
echo 'export ANTHROPIC_AUTH_TOKEN=[YOUR-FASTROUTER-API-KEY]' >> ~/.zshrc
source ~/.zshrc

For Fish users (~/.config/fish/config.fish):

echo 'set -x ANTHROPIC_BASE_URL "https://api.fastrouter.ai"' >> ~/.config/fish/config.fish
echo 'set -x ANTHROPIC_API_KEY ""' >> ~/.config/fish/config.fish
echo 'set -x ANTHROPIC_AUTH_TOKEN [YOUR-FASTROUTER-API-KEY]' >> ~/.config/fish/config.fish
source ~/.config/fish/config.fish

Verification

Step 5: Launch Claude Code

Start Claude Code by running:

claude

Claude Code should now be configured to route all API requests through FastRouter.ai.

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Using Other Models via FastRouter

One of the key advantages of routing Claude Code through FastRouter is access to the full range of models supported by FastRouter—not just Anthropic's Claude. You can point Claude Code at any model available on FastRouter by passing the --model flag at startup.

Syntax

claude --model <provider-name>/<model-name>

Examples

OpenAI GPT-5.4 Mini

claude --model openai/gpt-5.4-mini

DeepSeek V4 Pro

claude --model deepseek/deepseek-v4-pro

How It Works

When you specify a model using the --model flag, FastRouter intercepts the request and routes it to the appropriate provider on your behalf. Your FastRouter API key handles authentication across all supported providers—no additional credentials needed.

Note: Model availability depends on your FastRouter plan. Visit the FastRouter model catalog to see the full list of supported models and providers.

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Troubleshooting

Common Issues

Issue: Authentication errors

• Verify your FastRouter.ai API key is correct

• Ensure ANTHROPIC_API_KEY is set to an empty string ("")

• Check that ANTHROPIC_BASE_URL is exactly https://api.fastrouter.ai

Issue: Environment variables not persisting

• Make sure you've added the exports to the correct shell profile file

• Run source ~/.bashrc (or appropriate file) to reload the configuration

• Verify the variables are set with: echo $ANTHROPIC_BASE_URL

Issue: Claude Code not found after installation

• Restart your terminal or open a new terminal window

• Check if the installation path is in your PATH variable

• Try running the installation command again

Issue: Model not found or unsupported

• Confirm the model name matches FastRouter's catalog exactly (e.g., openai/gpt-5.4-mini)

• Ensure your FastRouter plan includes access to the requested provider

• Check FastRouter documentation for the current list of supported models

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