Claude Fable 5 and Sonnet 5 are live
One base URL. The entire Claude lineup.
Fable 5 and Sonnet 5 just landed, alongside every Opus, Sonnet and Haiku already in service. Point an Anthropic-compatible client at OpusMax and the only thing that changes is the base URL — same SDK, same request shape, same streaming.
https://api.opusmax.pro1M
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Focused on
Claude Fable 5
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The lineup
Two new models at the front of the line.
Fable 5 is the most capable model available here — frontier reasoning over a million tokens of context, built for long agentic runs. Sonnet 5 gives you that same generation at Sonnet speed. Everything below them stays available on the same key.
Claude Fable 5
Most capable. Frontier reasoning and long-horizon agentic work.
Claude Opus 5
New Opus flagship. Thinking on by default; knowledge current to May 2026.
Claude Sonnet 5
Frontier intelligence at Sonnet speed. The new default.
Control
Built for whoever holds the keys.
Multi-tenant key management with real limits behind it: budgets, rates, expiry and usage tracking, plus an admin dashboard for teams and resellers.
Per-key token budgets
Every key carries its own 5-hour rolling window. Spend it, and the key waits for the reset — no surprise overage.
Isolated rate limits and expiry
Requests per minute and an expiry date are set per key, not per account. One noisy key cannot starve another.
Streaming passed straight through
Server-sent events are forwarded as they arrive. Token-by-token output behaves exactly as your SDK expects.
Prompt caching, uncharged
Cache reads and cache writes do not count against a key’s window. Only fresh input and output tokens do.
Drop-in Anthropic compatibility
The request and response shapes are the ones you already code against. No adapter, no SDK fork, no rewrite.
Works with the tools you use
Claude Code, Cursor, VS Code, Windsurf, Cline, Roo Code, the Python and TypeScript SDKs, and plain cURL.
Setup
Three steps, one of them optional.
shell
export ANTHROPIC_BASE_URL=https://api.opusmax.pro
export ANTHROPIC_AUTH_TOKEN=YOUR_API_KEYOr run npx opusmax and let the wizard write it for you.
Get a key
Your admin or reseller issues one, with the budget, rate limit and expiry already set. Nothing to configure on your side.
Repoint the base URL
Two environment variables, or one run of the setup wizard. Your existing code is untouched.
Call any model in the lineup
Pass a model ID and go. Streaming, tool use, prompt caching and token counting all behave as they do upstream.
Get started
Change one line. Keep everything else.
The setup guide covers every client we support, end to end. If you already have a key, you are about sixty seconds from your first request.