How to use Claude Code with a custom Anthropic API endpoint

echo 'export ANTHROPIC_BASE_URL="https://www.ccsub.net"' >> ~/.zshrc
echo 'export ANTHROPIC_AUTH_TOKEN="sk-your-key"' >> ~/.zshrc
source ~/.zshrc
claude

Claude Code is Anthropic's agentic coding tool for the terminal, and it only speaks the Anthropic Messages API. That keeps the setup short: no Claude account login and no code changes. You tell Claude Code where to send requests (ANTHROPIC_BASE_URL) and which credential to send (ANTHROPIC_AUTH_TOKEN). Anthropic documents this as connecting Claude Code to an "LLM gateway", and CCSub works the same way.

The two variables

The mistake we see most often is a /v1 suffix. Claude Code builds the request path itself, so https://www.ccsub.net becomes https://www.ccsub.net/v1/messages. If you enter https://www.ccsub.net/v1, the request goes to /v1/v1/messages and fails.

macOS and Linux

Check your shell with echo $SHELL. If it ends in zsh, edit ~/.zshrc; if it ends in bash, edit ~/.bashrc:

echo 'export ANTHROPIC_BASE_URL="https://www.ccsub.net"' >> ~/.zshrc
echo 'export ANTHROPIC_AUTH_TOKEN="sk-your-key"' >> ~/.zshrc
source ~/.zshrc

Run echo $ANTHROPIC_BASE_URL afterwards. If it prints the URL, the current window has picked it up.

Windows (PowerShell)

Store the values as user environment variables so every new terminal sees them:

[System.Environment]::SetEnvironmentVariable('ANTHROPIC_BASE_URL', 'https://www.ccsub.net', 'User')
[System.Environment]::SetEnvironmentVariable('ANTHROPIC_AUTH_TOKEN', 'sk-your-key', 'User')

Then close all PowerShell and terminal windows. Windows does not push new variables into windows that are already open, and the same goes for the integrated terminal inside VS Code or Cursor: quit the editor and start it again.

Using settings.json instead

If you would rather not touch system variables, put the values in Claude Code's own settings file, ~/.claude/settings.json (%USERPROFILE%\.claude\settings.json on Windows). It applies to every project, including background sessions:

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://www.ccsub.net",
    "ANTHROPIC_AUTH_TOKEN": "sk-your-key"
  }
}

If the file already has other settings, merge the env block in and watch your commas. When the same variable is set both in your shell and in settings.json, the settings file wins — check it first if a shell change seems to do nothing.

For a single project, use .claude/settings.local.json. Do not put the key in a project's .claude/settings.json: that file is normally committed, so the key would travel with the repository. Project-level files also only apply after you accept the folder trust prompt.

The VS Code extension

The Claude Code extension checks credentials before it launches, and that check does not read ~/.claude/settings.json. Anthropic's docs recommend VS Code's own user settings instead. Run Preferences: Open User Settings (JSON) and add:

{
  "claudeCode.environmentVariables": [
    { "name": "ANTHROPIC_BASE_URL", "value": "https://www.ccsub.net" },
    { "name": "ANTHROPIC_AUTH_TOKEN", "value": "sk-your-key" }
  ]
}

Start a session and confirm the route

cd ~/your-project
claude

Accept the defaults on first launch. Type /model to choose a model; the model field takes IDs such as claude-sonnet-5, and every available ID is listed on the models page.

Two ways to confirm traffic really goes through CCSub:

1. Run /status. The Status tab should show an Anthropic base URL line with https://www.ccsub.net and an Auth token line naming ANTHROPIC_AUTH_TOKEN. If the base URL line is missing, the variable did not reach the session.
2. Check the bill: send one message, then open Usage in the CCSub dashboard. If the request and its token counts show up, you are done.

Before opening Claude Code at all, you can test the URL and key with curl. A JSON body starting with {"id":"msg_ means everything works; a 401 means the key is wrong:

curl -sS -X POST "$ANTHROPIC_BASE_URL/v1/messages" \
  -H "Authorization: Bearer $ANTHROPIC_AUTH_TOKEN" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5","max_tokens":16,"messages":[{"role":"user","content":"hi"}]}'

Switching between providers

If you move between CCSub and other API providers, editing variables every time gets old. CC Switch is a desktop app that swaps Claude Code providers with one click, and CCSub is already in its preset list. For OpenAI's terminal agent, see the Codex CLI guide.

A note on cost

Every turn in Claude Code resends the conversation so far, so input tokens grow over a long session. On CCSub, cache reads and writes for regular accounts are billed at the input price, which means /clear when you change topics and /compact for long threads are the simplest ways to keep usage down. Each request's charge is itemised on the Usage page.