Castari Proxy — Development agent for Claude Code

Castari Proxy

Castari Proxy lets you run the Claude Agent SDK against any model—including OpenRouter catalog models—without changing your agent logic. Install the `castari-proxy` wrapper, point it at the **hosted Castari Worker**, and keep using the same SDK APIs. The worker translates Anthropic-style Messages requests to whichever upstream (Anthropic or OpenRouter) matches the model string you provide.

Claude Agent SDK ── queryCastari ──► Castari Worker (hosted)
                                       ├─► Anthropic Messages API
                                       ├─► OpenRouter Chat Completions
                                       └─► *more coming soon*

Don't want to hit the hosted worker? See [Self-Hosting the Worker](#self-hosting-the-worker) for instructions to deploy your own copy.

Repo Overview

This repository contains three main components that work together to enable multi-provider support for the Claude Agent SDK:

1. Wrapper Package (`src/`)

The `castari-proxy` npm package provides `queryCastari()`, a drop-in replacement for the SDK's `query()` function. It:

• Resolves which provider to use based on the model string (e.g., or:gpt-5-mini → OpenRouter)
• Intercepts SDK network calls via a global fetch hook
• Injects routing headers and metadata into outgoing requests
• Handles subagent model inheritance for the Task tool

2. Cloudflare Worker (`worker/`)

A stateless proxy that translates between API formats. It:

• Routes requests to Anthropic (passthrough) or OpenRouter (with translation)
• Converts Anthropic Messages API ↔ OpenRouter Chat Completions format
• Handles streaming (SSE) translation with tool call assembly
• Enforces server tool policies (MCP, web search, etc.)

3. Demo Application (`claude-agent-demo/`)

A full-stack Next.js reference implementation of the Claude Agent SDK featuring:

• 12-model selection UI (3 Claude + 9 OpenRouter models)
• Streaming chat with real-time tool execution visualization

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