Cursor’s login prompt glares back, demanding its own cash while Copilot sits idle on my tab.
Reverse-engineering Cursor IDE to run on GitHub Copilot? That’s the hack one dev just dropped, proxying the hell out of its proprietary guts. Love the UI – Composer, terminal magic, those MCP tools. Hate the lockdown. It’s 2024, and we’re still fighting app stores in code editors.
Cursor blocks your keys. Hard. Tries to shove claude-3.5-sonnet through their billing machine. No escape.
But this guy built a MITM proxy. Local services on ports 4141 and 4142. Auth layer fakes OAuth to GitHub. Intelligence proxy – Bun-powered – snags outbound traffic, tweaks payloads, fires to Copilot.
Flow’s simple: Cursor ➡️ Proxy (4142) ➡️ Bridge (4141) ➡️ GitHub.
Easy? Ha. Cursor’s no dummy.
Why Does Cursor Actively Block Your Copilot Keys?
Set a custom model like claude-3.5-sonnet to localhost:4142? Cursor sniffs the name, ignores you, routes to api2.cursor.sh. Internal router’s ironclad.
Loophole hunt. Cursor hijacks known models only. Unknown? Falls back to your endpoint.
Prefix trick: cus-claude-3.5-sonnet. Cursor shrugs – “Local LLM? Fine.” Payload escapes to proxy.
Inside Bun: strip the ‘cus-‘, forward clean model name. Handshake cracked.
I love Cursor IDE. It is arguably the most advanced AI code editor on the market today. But I hate closed ecosystems. And I absolutely refuse to pay for two AI subscriptions when one should do the job.
That’s the dev’s manifesto. Spot on. Cursor’s PR spins ‘smoothly integration.’ Translation: captive audience.
Roadblock two hits harder. Agent features? Composer? Massive tool arrays. Anthropic schemas – input_schema keys. Copilot demands OpenAI format: parameters in functions.
Forward raw? 400 Bad Request. Illegal props like additionalProperties: false, title, $schema. Copilot chokes.
No regex hack. Too gnarly. Enter recursive AST cleaner. Walks JSON tree, nukes junk, recurses properties and arrays.
Then tool transform: Anthropic to OpenAI. Map input_schema to parameters. Clean every tool.
Code’s brutal poetry:
const cleanSchema = (schema: any) => {
if (!schema || typeof schema !== 'object') return schema;
// Copilot's OpenAI parser hates these. Nuke them.
if (schema.additionalProperties !== undefined) delete schema.additionalProperties;
if (schema.$schema !== undefined) delete schema.$schema;
if (schema.title !== undefined) delete schema.title;
// Recurse...
};
Real-time mutation. Milliseconds. Cursor none the wiser.
Can Any Dev Pull Off This Cursor Copilot Proxy?
You? Maybe. Grab the ports, Bun script, open-source connector. Tweak for your setup.
But here’s my hot take – Cursor’s begging for backlash. Remember Firefox extensions vs. Chrome’s Manifest V3 lockdown? Devs forked Chromium, built ungoogled-chrome. This proxy’s the spark. Bold prediction: forks of Cursor incoming, Copilot-native from day one. Open-weight UIs crushing proprietary backends.
Cursor’s spin? ‘Best experience.’ Bull. It’s rent-seeking. GitHub/Microsoft already owns the backend game – why double-dip?
Tested it? Composer hums. Terminal executes. Tools fire. All on Copilot’s dime.
Dry humor alert: Feels like jailbreaking your Roomba to vacuum the neighbor’s house. Efficient, if slightly felonious.
Walled gardens crumble under MITM fire. Cursor next?
Devs, hoard this repo. Before Cursor patches the ‘cus-’ hole.
Unique angle: Parallels the 90s RealPlayer wars. Proprietary codecs forced proxies everywhere. Flash died to HTML5. History rhymes – open APIs win.
Cursor team, reading this? Open the damn router. Or watch proxies multiply.
The Bigger Hack: AI IDE Hypocrisy Exposed
Everyone praises Cursor’s ‘intelligence.’ But intelligence without portability? Just a pretty trap.
Copilot’s open-ish API shines here. Anthropic’s tool spec? Too bespoke. OpenAI’s the glue.
This proxy proves UI from one, brains from another. Stackable. Future of tools.
One-paragraph rant: Companies like Cursor bet on inertia. ‘Users won’t hack.’ Wrong. We’re the ones writing the patches.
Short punch: Hack responsibly.
Dense dive: Proxy scales. Add o1-preview? Tweak model map. Multi-provider? Route table. But security – MITM local only, no cloud leaks. Audit that Bun code.
Cursor updates? Breakage likely. Dev’s chasing. Community fork?
PR spin callout: ‘Advanced agent features.’ Nah. Borrowed from Anthropic, repackaged.
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Frequently Asked Questions
How do I set up a Cursor IDE GitHub Copilot proxy?
Spin up ports 4141/4142 with the scripts. Config cus-model in Cursor settings. Proxy strips and cleans. Boom.
Does Cursor block custom API keys in Agent mode?
Yes. Hardcodes routing for known models. Prefix hack bypasses.
Is reverse-engineering Cursor legal?
Your machine, your rules. No EULA dive here – but don’t sell it.
Worth 950 words of your time? Damn right.
