Claude agent sdk multi provider bridge

Multi-provider agent behind one AgentBackend

When to use

• App wants "use Claude, but also OpenAI, Gemini, Llama-via-Ollama, Codex, Copilot" without maintaining N bespoke client stacks.
• Claude Agent SDK already handles Claude and any Anthropic-compatible endpoint; a second SDK (Pi) covers OpenAI/Google/Copilot idioms.
• Need a single AgentBackend interface so session storage, tool dispatch, event adapters don't branch per provider.

How it works

1. Define a common AgentBackend interface: start(options), query(messages), abort(), event stream, permission callbacks. Both ClaudeAgent and PiAgent implement it.
2. Driver registry keyed by provider:

   const DRIVER_REGISTRY: Record<AgentProvider, ProviderDriver> = {
     anthropic: anthropicDriver,
     pi: piDriver,
   };
   

3. Each LLM connection record carries providerType (anthropic, openai, google, openrouter, groq, mistral, xai, ...) and authType (apiKey, oauth, claudeMax, ...).
4. For Anthropic-family providers, anthropicDriver resolves the API key / OAuth token and sets ANTHROPIC_BASE_URL + ANTHROPIC_AUTH_TOKEN (or ANTHROPIC_API_KEY) before instantiating the Claude SDK. That's ALL it takes to point at OpenRouter or Ollama.
5. For Pi-family providers, piDriver configures @mariozechner/pi-ai with provider-specific auth (GOOGLE_API_KEY, Codex OAuth, Copilot device-code flow).
6. A shared event adapter translates each SDK's stream into the app's normalized AgentEvent type; Claude and Pi have separate adapters but produce the same output shape.

Example

// Configure Claude SDK to talk to OpenRouter:
const env = {
  ...process.env,
  ANTHROPIC_BASE_URL: 'https://openrouter.ai/api/v1',
  ANTHROPIC_AUTH_TOKEN: userOpenRouterKey,
};
const q = query({ prompt, options: { ...base, model: 'anthropic/claude-opus-4.7' } });

// Shared dispatch
function createAgent(conn: LlmConnection): AgentBackend {
  const driver = DRIVER_REGISTRY[getProvider(conn.providerType)];
  return driver.create(conn);
}

Gotchas

• OpenRouter uses provider/model-name slugs, not bare model names - surface that in the UI.
• Ollama has no auth; pass an empty string for ANTHROPIC_AUTH_TOKEN but the env var must exist or the SDK will complain.
• The Pi SDK is ESM-only; your build pipeline needs bun build --target=bun --format=esm or it breaks at runtime.
• Don't leak provider-specific fields through the event adapter - keep AgentEvent canonical so UI code doesn't sprout if (provider === …).