Claude Code

Claude Code talks to an Anthropic Messages endpoint. Point it at BitRouter instead of api.anthropic.com and every request flows through the registry — so the same agent can run on Anthropic, OpenAI, Google, or an open model, with provider selection and fallback underneath.

Prerequisites

• BitRouter running — local proxy at http://127.0.0.1:4356, or BitRouter Cloud at https://api.bitrouter.ai.

• Claude Code installed:

  npm install -g @anthropic-ai/claude-code
  # or the native installer:
  curl -fsSL https://claude.ai/install.sh | bash

Point Claude Code at BitRouter

Claude Code reads three environment variables. Set the base URL to BitRouter's host root — it appends /v1/messages itself.

export ANTHROPIC_BASE_URL=http://127.0.0.1:4356
export ANTHROPIC_AUTH_TOKEN=local-placeholder        # sent as a bearer token
export ANTHROPIC_MODEL=anthropic/claude-sonnet-4-6
claude

Prefer a file? Put the same values in .claude/settings.json so they apply per-project without exporting:

{
  "env": {
    "ANTHROPIC_BASE_URL": "http://127.0.0.1:4356",
    "ANTHROPIC_AUTH_TOKEN": "local-placeholder",
    "ANTHROPIC_MODEL": "anthropic/claude-sonnet-4-6"
  }
}

Pick a model

ANTHROPIC_MODEL takes any registry id in provider/model form — anthropic/claude-sonnet-4-6, openai/gpt-4o, google/gemini-2.5-pro. Add a :cost or :latency suffix to bias provider selection for the session. Switch mid-session with /model <id>, or at launch with claude --model <id>. See Models for the full id scheme.

Verify

Launch claude, ask it anything, and confirm the response. To see which provider actually answered, read BitRouter's request finished log line (~/.bitrouter/bitrouter.log for a local install) — it records the provider and model that served the request.

Learn more

• Claude Code — LLM gateway config
• Model fallback — pass an ordered model list and walk it on failure.
• OpenTelemetry — trace every Claude Code request.