Privacy Policy

Stella is operated by Northbrook PBC (“Stella,” “we,” “us”). We provide a text-first tutoring service that students reach through iMessage and SMS at stellatutor.com. When we refer to “the Service” in this policy, we mean the Stella website, the Stella tutoring line, and any related tools.

We collect the information needed to sign you up, tutor you by text, keep context across sessions, and bill for a subscription.

• Account details. Your phone number and a verification code sent by text when you sign in. We use phone number as your primary identifier, and Stella may learn your preferred name in the tutoring conversation.
• Messages and attachments. The content you send to Stella and Stella's replies, including screenshots, photos of worksheets, and voice notes. Messages are linked to your account so Stella can keep context across sessions.
• Tutoring workspace. Materials generated while tutoring you, such as your learning plan, session notes, and saved memory. These exist so Stella can pick up where you left off.
• Family connections. If a parent, guardian, or tutor is linked to a student account, we store the relationship and any shared messaging thread so everyone sees the same conversation.
• Billing information. If you start a paid plan, our payment processor collects your payment method and returns subscription details (plan, status, renewal dates) to us. We do not store full card numbers.
• Device and usage data. Standard server logs (IP address, browser, pages visited, timestamps) and cookies used to keep you signed in and to understand how the Service is used.

• To run the tutoring service. Route your messages to Stella, generate responses, keep context across sessions, and show your plan and history in the dashboard.
• To verify and secure your account. Send one-time codes, authenticate you, detect abuse, and protect the Service.
• To bill subscriptions. Process payments, manage your plan, and send receipts and renewal notices.
• To improve Stella. Measure product usage, debug issues, and evaluate tutoring quality. We do not sell your data or use your messages to train third-party foundation models.
• To communicate with you. Respond to support requests, share updates about the Service, and (if you signed up) send text messages from Stella.

We share the minimum information necessary with the vendors that help us operate Stella. Each is contractually limited to using that data to provide their service to us.

• Supabase. Hosts our database and user authentication. Stores your profile, messages, learning plan, and subscription state.
• Linq. Delivers and receives iMessages between Stella and you. Linq handles the messages sent to and from the Stella tutoring line.
• Anthropic and other AI providers. Process the content of your messages to generate tutoring responses. We route model requests through the Vercel AI Gateway. Providers are contractually required not to train their foundation models on your content.
• Stripe. Processes payments and manages subscriptions. Stripe receives your payment method directly; we receive only non-sensitive subscription details.
• Vercel. Hosts and serves the website and serverless functions that power Stella.

We may also disclose information when required by law, to respond to valid legal process, to protect the rights or safety of Stella users, or in connection with a business transaction such as a merger or acquisition (with notice to you where required).

Stella works primarily by text. When you message the Stella line, your carrier and Apple’s iMessage service handle delivery in the same way they would for any other contact. The contents of messages you send to Stella are received by our partner Linq and stored in Stella’s systems so that Stella can respond and remember prior conversations.

Standard message and data rates may apply. You can stop receiving texts from Stella at any time by replying STOP, or by asking us to close your account.

Stella uses large language models to read your messages and generate tutoring responses. Your messages, attachments, and relevant context from your workspace are sent to AI providers in order to produce a reply. We configure these providers for zero data retention where available, and they are contractually prohibited from training their foundation models on your content.

Because AI responses can contain mistakes, do not rely on Stella for medical, legal, financial, or other professional advice.

Stella is designed for students, including middle-school and high-school learners, and for the parents and guardians who support them.

Stella is not directed to children under 13, and we do not knowingly collect personal information from a child under 13 without verifiable parental consent. If you are a parent or guardian and believe your child has provided us with information without your consent, please contact us at team@northbrook.com and we will delete the account and associated data.

Where a student account is linked to a parent or guardian, we share the tutoring thread and basic session information with that adult. Parents can request account closure or data deletion on behalf of their child at the contact address above.

We use a small number of first-party cookies to keep you signed in and to remember preferences. We also use privacy-respecting analytics to understand aggregate product usage. We do not use third-party advertising cookies, and we do not sell or share personal information for cross-context behavioral advertising.

We keep your account information, messages, and workspace for as long as your account is active so Stella can tutor you with context. When you close your account, we delete or de-identify your personal information within a reasonable period, except where we need to keep records to comply with law (for example, billing records) or to resolve disputes.

We protect your information with encryption in transit, access controls, and row-level security in our database. No online service can be perfectly secure, but we work to keep your data safe and to notify affected users promptly if a breach occurs.

You can ask us to access, correct, export, or delete your personal information, and you can ask us to stop texting you at any time. Depending on where you live, you may have additional rights under laws like the GDPR or CCPA/CPRA, including the right to object to certain processing and to lodge a complaint with a data protection authority.

To exercise any of these rights, email team@northbrook.com. We will respond within the time required by applicable law.

Stella is operated from the United States. If you use the Service from outside the U.S., you understand that your information will be transferred to and processed in the United States and other countries where our service providers operate.

We may update this policy from time to time. When we make material changes, we will update the effective date and, where appropriate, notify you by text or on the website before the changes take effect.

Questions, requests, or concerns about this policy or your data can be sent to team@northbrook.com.