Using Claude Code and Agent SDK with Alternative Providers

Claude Code isn't locked to Anthropic's direct API. By setting a few environment variables, you can route requests through alternative providers like Z.AI or OpenRouter—useful for accessing different models, managing costs, or leveraging provider-specific features.

Quick Reference

Provider	Base URL	Key Variable	Notes
Anthropic	(default)	`ANTHROPIC_API_KEY`	No configuration needed
Z.AI	`https://api.z.ai/api/anthropic`	`ANTHROPIC_AUTH_TOKEN`	Higher token limits, GLM-4.7 access
OpenRouter	`https://openrouter.ai/api`	`ANTHROPIC_AUTH_TOKEN`	400+ models, failover, budget controls

Anthropic (Default)

No setup required. After logging in, Claude Code uses Anthropic's API directly:

claude

For API key authentication without interactive login:

export ANTHROPIC_API_KEY="sk-ant-..."
claude

Z.AI Configuration

Z.AI provides an Anthropic-compatible endpoint with higher token quotas and access to GLM-4.7 models.

Shell Function (Recommended)

Add to ~/.zshrc or ~/.bashrc:

zaiclaude() {
  ANTHROPIC_BASE_URL=https://api.z.ai/api/anthropic \
  ANTHROPIC_AUTH_TOKEN="YOUR_ZAI_TOKEN" \
  CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1 \
  claude "$@"
}

Usage:

zaiclaude

Fish Shell

Add to ~/.config/fish/config.fish:

function zaiclaude
  set -lx ANTHROPIC_BASE_URL https://api.z.ai/api/anthropic
  set -lx ANTHROPIC_AUTH_TOKEN "YOUR_ZAI_TOKEN"
  set -lx CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC 1
  claude $argv
end

Global Configuration

To make Z.AI the default for all Claude Code sessions:

export ANTHROPIC_BASE_URL="https://api.z.ai/api/anthropic"
export ANTHROPIC_AUTH_TOKEN="YOUR_ZAI_TOKEN"
export CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1

OpenRouter Configuration

OpenRouter aggregates 400+ models and provides automatic failover between providers.

Shell Function

openrouterclaude() {
  ANTHROPIC_BASE_URL="https://openrouter.ai/api" \
  ANTHROPIC_AUTH_TOKEN="$OPENROUTER_API_KEY" \
  ANTHROPIC_API_KEY="" \
  CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1 \
  claude "$@"
}

Important: ANTHROPIC_API_KEY must be explicitly set to empty string. If unset (null), Claude Code may fall back to default authentication behavior.

Fish Shell

function openrouterclaude
  set -lx ANTHROPIC_BASE_URL "https://openrouter.ai/api"
  set -lx ANTHROPIC_AUTH_TOKEN "$OPENROUTER_API_KEY"
  set -lx ANTHROPIC_API_KEY ""
  set -lx CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC 1
  claude $argv
end

Global Configuration

export OPENROUTER_API_KEY="sk-or-..."
export ANTHROPIC_BASE_URL="https://openrouter.ai/api"
export ANTHROPIC_AUTH_TOKEN="$OPENROUTER_API_KEY"
export ANTHROPIC_API_KEY=""
export CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1

Model Overrides

When using OpenRouter, you can override which models Claude Code uses for different tiers:

# Override the default "Sonnet" tier model
export ANTHROPIC_DEFAULT_SONNET_MODEL="z-ai/glm-4.7"

# Override the "Opus" tier model
export ANTHROPIC_DEFAULT_OPUS_MODEL="openai/gpt-5.2-pro"

# Override the "Haiku" tier model
export ANTHROPIC_DEFAULT_HAIKU_MODEL="z-ai/glm-4.5-air"

Popular Model Choices

Tier	Model ID	Provider
Sonnet	`z-ai/glm-4.7`	Z.AI
Sonnet	`openai/gpt-5.2`	OpenAI
Sonnet	`mistralai/devstral-2512`	Mistral
Opus	`openai/gpt-5.2-pro`	OpenAI
Haiku	`z-ai/glm-4.5-air`	Z.AI
Haiku	`xiaomi/mimo-v2-flash:free`	Xiaomi

GLM-4.7 via OpenRouter

Dedicated function for using Z.AI's GLM-4.7 through OpenRouter:

glmclaude() {
  ANTHROPIC_BASE_URL="https://openrouter.ai/api" \
  ANTHROPIC_AUTH_TOKEN="$OPENROUTER_API_KEY" \
  ANTHROPIC_API_KEY="" \
  ANTHROPIC_DEFAULT_SONNET_MODEL="z-ai/glm-4.7" \
  CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1 \
  claude "$@"
}

Anthropic Agent SDK

The Agent SDK uses Claude Code as its runtime, so the same environment variables apply.

TypeScript

npm install @anthropic-ai/claude-agent-sdk

import { query } from "@anthropic-ai/claude-agent-sdk";

// Set environment variables before running:
// ANTHROPIC_BASE_URL=https://openrouter.ai/api
// ANTHROPIC_AUTH_TOKEN=your_openrouter_api_key
// ANTHROPIC_API_KEY=""

async function main() {
  for await (const message of query({
    prompt: "Find and fix the bug in auth.py",
    options: {
      allowedTools: ["Read", "Edit", "Bash"],
    },
  })) {
    if (message.type === "assistant") {
      console.log(message.message.content);
    }
  }
}

main();

Python

pip install claude-agent-sdk

import asyncio
from claude_agent_sdk import query, ClaudeAgentOptions

# Set environment variables before running:
# ANTHROPIC_BASE_URL=https://openrouter.ai/api
# ANTHROPIC_AUTH_TOKEN=your_openrouter_api_key
# ANTHROPIC_API_KEY=""

async def main():
    async for message in query(
        prompt="Find and fix the bug in auth.py",
        options=ClaudeAgentOptions(
            allowed_tools=["Read", "Edit", "Bash"]
        )
    ):
        print(message)

asyncio.run(main())

The Agent SDK inherits all model override capabilities. Use ANTHROPIC_DEFAULT_SONNET_MODEL and similar variables to route agents to different models.

GitHub Actions

Use OpenRouter with the official Claude Code GitHub Action:

- name: Run Claude Code
  uses: anthropics/claude-code-action@v1
  with:
    anthropic_api_key: ${{ secrets.OPENROUTER_API_KEY }}
  env:
    ANTHROPIC_BASE_URL: https://openrouter.ai/api

Store your OpenRouter API key as a GitHub secret named OPENROUTER_API_KEY.

Environment Variables Reference

Variable	Purpose	Required For
`ANTHROPIC_BASE_URL`	API endpoint URL	Z.AI, OpenRouter
`ANTHROPIC_AUTH_TOKEN`	Authentication token	Z.AI, OpenRouter
`ANTHROPIC_API_KEY`	Anthropic API key (set empty for alternatives)	OpenRouter
`ANTHROPIC_DEFAULT_SONNET_MODEL`	Override Sonnet tier model	Model customization
`ANTHROPIC_DEFAULT_OPUS_MODEL`	Override Opus tier model	Model customization
`ANTHROPIC_DEFAULT_HAIKU_MODEL`	Override Haiku tier model	Model customization
`CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC`	Disable telemetry	Recommended for all

Verification

After configuration, verify your setup:

Run /status inside Claude Code to check the connection
Check OpenRouter Activity Dashboard to see requests (if using OpenRouter)
Monitor your provider's usage dashboard for billing accuracy

Troubleshooting

Issue	Solution
Auth errors	Ensure `ANTHROPIC_API_KEY=""` is explicitly empty (not unset)
Requests still hitting Anthropic	Run `/logout` first if previously logged in
Model not found	Check model ID on OpenRouter models
Tool use failing	Verify your chosen model supports tool use

Important Considerations

Tool Use Support: Claude Code relies heavily on tool use (file reading, command execution, editing). When selecting alternative models, ensure they support tool use. Filter by this capability on the OpenRouter models page.
Billing: You're billed through your chosen provider. Usage appears in their respective dashboards, not Anthropic's.
Privacy: OpenRouter doesn't log prompts by default. Check provider privacy policies for specifics.
Performance: While many models work, Claude models typically provide the best experience for complex coding tasks due to their optimization for tool use and code generation.