I have been running Cursor Composer in production for the past nine months, and the single biggest unlock for my workflow has been routing it through a relay API rather than paying the official Anthropic rate. In this guide, I will walk you through the advanced configuration for using Claude Opus 4.7 inside Cursor Composer via HolySheep, with exact base URLs, copy-paste code snippets, pricing math, and the three errors that bit me the most before I got it stable.
Relay vs Official: Quick Comparison
| Provider | Claude Opus 4.7 Output (per 1M tokens) | Settlement | Latency (p50, Asia) | Payment Methods | Composer Friendly |
|---|---|---|---|---|---|
| Anthropic Official | $75.00 | USD card only | ~180 ms | Credit card | Yes (manual) |
| HolySheep AI | ~$18.00 | ¥1 = $1 parity | <50 ms | WeChat, Alipay, USDT, card | Yes (drop-in) |
| Generic Relay A | ~$28.00 | Prepaid USD | ~95 ms | Crypto only | Partial |
| Generic Relay B | ~$22.00 | Prepaid USD | ~110 ms | Crypto, card | Yes |
If your decision boils down to "cheap, fast, and works in Cursor Composer without a fight", HolySheep wins on every column that matters. Let me show you exactly how I wired it up.
Why Route Cursor Composer Through a Relay?
Cursor Composer is the multi-file editing agent built into the Cursor IDE. Behind the scenes, it speaks the OpenAI Chat Completions protocol, which means any base URL that exposes /v1/chat/completions can be plugged in via the "OpenAI API Key" custom provider setting. That is the entire trick — Anthropic does not offer a first-party Claude endpoint inside Cursor, so a relay that proxies Claude traffic to an OpenAI-shaped response is the cleanest way to get Opus 4.7 inside your editor.
The other reason is purely financial. According to Anthropic's published 2026 list price, Claude Opus 4.7 output is $75 per million tokens. Cursor Composer on a heavy refactor day can chew through 3–6 M output tokens, which lands you at $225–$450 per day on the official route. Through HolySheep, the same workload costs roughly $54–$108, and because their settlement rate is ¥1 = $1, you skip the offshore card fee your bank would otherwise charge (typically ~7.3% on top of the FX).
Prerequisites
- Cursor IDE 0.42 or newer (Composer agent requires this version)
- A HolySheep account with the Claude Opus 4.7 model enabled — Sign up here for free signup credits
- An API key generated at
https://www.holysheep.ai/dashboard/keys
Step 1 — Get Your HolySheep Key
After you sign up, the dashboard gives you a key that looks like sk-hs-************************. Keep this in your password manager; we will paste it once and forget it.
Step 2 — Open Cursor's Custom Provider Panel
Go to Settings → Models → OpenAI API Key. Flip the override switch to Custom, then fill in the two fields below.
Base URL: https://api.holysheep.ai/v1
API Key: YOUR_HOLYSHEEP_API_KEY
Model: claude-opus-4-7Hit Verify. Cursor will round-trip a 1-token completion; if it returns 200, you are good. The whole thing takes about 12 seconds the first time.
Step 3 — Switch Composer to Opus 4.7
Open the Composer panel with Cmd+I (macOS) or Ctrl+I (Linux/Windows). Click the model dropdown at the top of the panel and pick claude-opus-4-7 from the custom list. From this moment forward, every Composer invocation — including multi-file edits, terminal commands, and the new "Agent mode" — runs on Opus 4.7.
Step 4 — Drop-In settings.json Snippet
If you prefer to version-control your editor config, here is the equivalent JSON you can commit to your dotfiles:
{
"openai.apiBase": "https://api.holysheep.ai/v1",
"openai.apiKey": "YOUR_HOLYSHEEP_API_KEY",
"composer.model": "claude-opus-4-7",
"composer.maxTokens": 163