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Privacy

Last updated: April 2026

Who we are

Deltaframe is a system design practice product operated by LuoForge. When this policy says “we” or “us,” we mean LuoForge.

What we collect

  • Account data. Your email address, a hashed password if you sign up with email/password, and — if you sign in with GitHub — your name, profile image, and GitHub OAuth tokens (access and refresh tokens). We never store your GitHub password.
  • Practice data.The system design answers you write, the AI evaluations and follow-up exchanges generated from them, your skill scores, and the concepts queued for review. The full text of your answers is sent to Anthropic to produce evaluations (see “Third parties” below).
  • Onboarding assessment data. If you take the onboarding assessment, your answers are stored with your authenticated account and used to personalize your practice plan.
  • Payment data. If you upgrade to a paid tier, billing details (card number, billing address) are handled by Stripe and never touch our servers. We store only your Stripe customer ID and your subscription tier.
  • Operational data. Authentication cookies, session tokens, basic server logs, and anonymized page-view and Core Web Vitals data via Vercel Analytics.

How we use it

We use this data to provide the practice and evaluation features you signed up for, to decide which concepts to queue for your review, to operate billing, and to fix bugs and improve performance. We do not sell your data and we do not run advertising.

Third parties

We send data to a small set of providers strictly to operate the service:

  • Anthropic.The full text of your practice answers and follow-up responses is sent to Anthropic’s Claude API to produce evaluations. Anthropic processes the data on our behalf.
  • Stripe. Payment information.
  • GitHub. Only if you choose to sign in with GitHub.
  • Resend. Transactional email (password resets, email verification) if email is configured.
  • Vercel. Hosting, plus anonymized analytics on page views and Core Web Vitals.

Retention

We keep your account and practice data for as long as your account is active. Onboarding assessment data follows the same retention period as the rest of your account practice data.

Deleting your data

We don’t have a self-service delete button yet. If you want your account and associated practice data removed, email us via the support page and we’ll do it manually. Billing records that we’re required to keep for tax or legal reasons may be retained even after deletion.

Changes

If we make material changes to this policy, we’ll update the date at the top of this page.