Nexus Connect lets you run your Nexus Calc on your own AI provider account instead of buying credits from us. You plug in one API key, pick your model, and every solve runs on your plan — billed directly by the provider, never throttled by us.
This guide covers the two ways to get a key: the easy one-key-for-everything route with OpenRouter, and the direct route with OpenAI, Google, or Anthropic. Either works — pick whichever fits how you like to manage things.
What is an API key?
An API key is a private password that lets an app (your Nexus Calc) talk to an AI provider's models on your behalf. When you add a key to Nexus Connect, your calculator sends each problem to that provider and gets the step-by-step solution back. The provider bills your account for usage — usually fractions of a cent per solve.
Your key is encrypted and stored on your device — it's never sent to or stored on our servers in plaintext. Your credentials stay yours.
Option A — OpenRouter (recommended: one key, every model)
OpenRouter is a single gateway that gives you access to GPT, Gemini, Claude, and dozens of other models through one key. It's the easiest option because you don't need separate accounts with each provider, and you can switch models anytime without changing keys.
Step 1: Go to openrouter.ai and sign up (Google or email).
Step 2: Click your avatar → Keys (or visit openrouter.ai/keys).
Step 3: Click Create Key, give it a name like "Nexus Calc", and copy the key. It starts with sk-or-v1-…
Step 4: Add credits under Settings → Credits (a few dollars goes a long way — most solves cost well under a cent).
Step 5: Paste the key into your Nexus Connect dashboard (see the last section).
OpenRouter charges pay-as-you-go from your prepaid balance, so there are no monthly fees and no surprise bills — when the balance runs out, you simply top it up.
Option B — Direct provider keys
If you'd rather use a provider account directly, here's where to get a key from each. You only need one of these — Nexus Connect supports all three.
OpenAI (GPT-4o, GPT-5)
Step 1: Go to platform.openai.com/api-keys and sign in.
Step 2: Click Create new secret key, name it, and copy it. It starts with sk-…
Step 3: Add a payment method under Settings → Billing (OpenAI requires a small prepaid balance).
Google (Gemini 2.5 Pro)
Step 1: Go to aistudio.google.com/apikey and sign in with your Google account.
Step 2: Click Create API key and copy it.
Step 3: Google AI Studio includes a free tier — great for trying it out before adding billing.
Anthropic (Claude)
Step 1: Go to console.anthropic.com/settings/keys and sign in.
Step 2: Click Create Key, name it, and copy it. It starts with sk-ant-…
Step 3: Add credits under Billing.
How much does it cost?
Because you're billed by the provider directly, you only pay for what you use. A typical math solve sends a small image plus a short prompt and gets a short answer back — usually well under one cent. Five dollars of OpenRouter or provider credit covers hundreds of solves.
This is the difference between Nexus Connect and Nexus Credits:
- Nexus Connect — bring your own key, pay the provider directly, no markup, switch models freely. Best if you already have (or don't mind making) a provider account.
- Nexus Credits — no setup, no API key, just buy credits from us and solve. Best if you want the simplest possible experience.
Adding your key to Nexus Connect
Once you have a key from any of the options above, connecting it takes about 30 seconds:
Step 1: Sign in to your Nexus Calc dashboard.
Step 2: Find the provider card (OpenAI, Anthropic, or Google) and paste your key into the field.
Step 3: Pick your default model from the dropdown.
Step 4: Click Save key. The card flips to "Connected" and your calculator is ready.
You can swap keys, change your default model, or remove a key anytime from the same dashboard. Keys are encrypted and stored locally — we never see them in plaintext.
Security tips
- Treat your key like a password. Anyone with it can spend on your account. Don't paste it into public chats or commit it to code.
- Set a spending limit in your provider dashboard so a runaway script can't drain your balance.
- Rotate it if it leaks. Delete the old key in the provider console and create a new one — it takes seconds.
- Use a dedicated key named "Nexus Calc" so you can revoke just that one without affecting your other apps.
Ready to connect your own key?
Plug in an OpenRouter, OpenAI, Google, or Anthropic key and run your Nexus Calc on your own plan — or skip setup entirely with Nexus Credits.
Get started with Nexus Connect →