Support signing in with a SuperGrok / X Premium subscription for xAI (Grok) models

[Talimanato]

Body

What are you proposing?

Add an option to authenticate Zed's xAI provider with an existing SuperGrok / X Premium subscription — "bring your own subscription" via xAI account sign-in — instead of requiring a separate pay-per-token API key.

Why does this matter?

Today the only way to use Grok models in Zed is an xAI API key from console.x.ai, billed per token. Many users already pay for SuperGrok, SuperGrok Heavy, or X Premium for Grok access, so they effectively pay twice for the same models. API billing also requires a credit card and pre-paid credits, and costs are unpredictable under heavy agent usage.

[thibaudgg]

I forked Zed just for adding that feature yesterday and so far it's working like a charm. I'm planning to submit a PR after a week of testing without any hiccup.

The commit adding support for SuperGrok OAuth provider (x_ai_subscribed) and Grok 4.5 and 4.6 models (similar to #62731) on my fork: thibaudgg@785e781

[thibaudgg]

@bennetbo would you be interested in a PR for that or is it something that you are already planning to add internally? Thanks!

[bennetbo]

Enough people asked for it at this point, so happy to review a PR and get it merged

[thibaudgg]

Awesome to hear, I will submit a PR for it this week. 👍🏻

[thibaudgg]

PR is up: #63248