Claude Code API Setup

Claude Code is a terminal AI coding assistant. It connects to UnioAPI over the Anthropic-compatible protocol via POST /v1/messages.

1. Install Claude Code

Skip to section 2 if it is already installed.

Install Node.js (18 or newer) first, then run:

npm install -g @anthropic-ai/claude-code

Verify:

claude --version

Output like x.x.xxx (Claude Code) means the install succeeded.

2. Connect to UnioAPI

Create an API key in the console first.

macOS / Linux

Write the environment variables into your shell config (auto-detects zsh or bash):

SHELL_RC="$HOME/.zshrc"; case "$SHELL" in *bash*) SHELL_RC="$HOME/.bashrc";; esac
cat >> "$SHELL_RC" <<'EOF'
export ANTHROPIC_BASE_URL=https://api.unioapi.com
export ANTHROPIC_AUTH_TOKEN="your UnioAPI key"
EOF
source "$SHELL_RC"

Windows (PowerShell)

setx writes user-level environment variables; reopen the terminal afterwards:

setx ANTHROPIC_BASE_URL "https://api.unioapi.com"
setx ANTHROPIC_AUTH_TOKEN "your UnioAPI key"

Launch

claude

If the chat starts and replies normally, you are connected.

3. Optional: pin models

Claude Code supports environment variables that pin the model per tier. Use Unio model identifiers (full list: GET /v1/models):

export ANTHROPIC_MODEL=claude-sonnet-5
export ANTHROPIC_DEFAULT_SONNET_MODEL=claude-sonnet-5
export ANTHROPIC_DEFAULT_HAIKU_MODEL=claude-haiku-4.5

Without these, Claude Code uses its default model names; if a default model is not available on UnioAPI you will get a 404 — pin an available model as shown above.

Troubleshooting