Claude Code custom API setup

---
title: Claude Code custom API setup
description: Connect Claude Code directly to the Relyven Anthropic-compatible API with a custom base URL and API key.
lastUpdated: 2026-07-29
---

This page configures Claude Code directly. To manage Claude and Codex providers through a desktop app, use the [CC Switch guide](/en/integrations/cc-switch/).

## Before you start

- Install Claude Code and confirm the `claude` command runs.
- Create a Relyven key that can use the Claude model you need.
- Copy the exact model ID from the dashboard when the client asks for one.

## Configure the custom API

```bash
export ANTHROPIC_BASE_URL=https://api.relyven.com
export ANTHROPIC_AUTH_TOKEN="$RELYVEN_API_KEY"
claude
```

Use the service root without `/v1`. Claude Code adds the Anthropic Messages path.

Store the key in an environment variable or secret manager. Do not put it in a repository, screenshot, or shared prompt.

## Verify the connection

Start a new Claude Code conversation and make a short request. Then ask it to inspect a small local project with a tool call. A text reply confirms basic generation; it does not confirm tool events.

For an existing long conversation, save a rollback copy of the client configuration before changing providers. Use a new conversation for the first test so cached client state does not affect the result.

Relyven does not intentionally rewrite supported `system`, `tools`, `thinking`, `cache_control`, `max_tokens`, or streaming fields. The selected model still determines which combinations it accepts.

## Troubleshooting

| Result | Check |
|---|---|
| `401` | `ANTHROPIC_AUTH_TOKEN` and the base URL |
| `403` | Model permission on the current key |
| `400` | Request fields, model capability, context limit, and client version |
| `429` | Balance, key limits, and `retry-after` |
| Text works but tools fail | Tool schema and the returned Anthropic event types |
| Configuration did not change | Start a new shell and a new Claude Code conversation |

For raw API examples, see [Anthropic Messages](/en/api/messages/) and [API error handling](/en/api/errors/).

This page configures Claude Code directly. To manage Claude and Codex providers through a desktop app, use the CC Switch guide.

Before you start

Install Claude Code and confirm the claude command runs.
Create a Relyven key that can use the Claude model you need.
Copy the exact model ID from the dashboard when the client asks for one.

Configure the custom API

export ANTHROPIC_BASE_URL=https://api.relyven.com
export ANTHROPIC_AUTH_TOKEN="$RELYVEN_API_KEY"
claude

Use the service root without /v1. Claude Code adds the Anthropic Messages path.

Store the key in an environment variable or secret manager. Do not put it in a repository, screenshot, or shared prompt.

Verify the connection

Start a new Claude Code conversation and make a short request. Then ask it to inspect a small local project with a tool call. A text reply confirms basic generation; it does not confirm tool events.

For an existing long conversation, save a rollback copy of the client configuration before changing providers. Use a new conversation for the first test so cached client state does not affect the result.

Relyven does not intentionally rewrite supported system, tools, thinking, cache_control, max_tokens, or streaming fields. The selected model still determines which combinations it accepts.

Troubleshooting

Result	Check
`401`	`ANTHROPIC_AUTH_TOKEN` and the base URL
`403`	Model permission on the current key
`400`	Request fields, model capability, context limit, and client version
`429`	Balance, key limits, and `retry-after`
Text works but tools fail	Tool schema and the returned Anthropic event types
Configuration did not change	Start a new shell and a new Claude Code conversation

For raw API examples, see Anthropic Messages and API error handling.