Daily astrology readings for couples

The idea

Astrology apps are built for one person staring at their own chart, but the dominant use case is visibly relational — screenshotting a horoscope to send a partner, reading compatibility posts, checking a crush’s moon sign. Co-Star and The Pattern bolt compatibility on as a feature; nobody has built the daily ritual for two people around a shared reading both partners open together.

Project A proves LLM-generated astrology converts to consumer subscriptions at meaningful scale right now. The couples framing changes everything downstream: the content (synastry between two real charts, not a generic sun-sign blurb), the notification (tonight’s theme for both of you), and the reason to open it (did they check in yet). It also builds distribution into the product — every subscriber invites their partner by design, delivering a second retained user per sale and a viral loop the single-player incumbents would have to redesign their apps to copy. Real ephemeris math under LLM prose keeps the astrology-literate from catching errors and the content cost near zero.

Who pays

Realistically one partner pays — women 20-35 who already spend on astrology apps — at $9.99/mo or $59.99/yr covering both people, through an onboarding paywall right after the compatibility reveal. Distribution: TikTok and Instagram couples-astrology content (an enormous existing content category), ASO on couples astrology and synastry terms, and the built-in partner invite.

MVP scope

• Dual birth-chart entry with real ephemeris-computed natal charts and synastry aspects
• Nightly batch generation of a shared daily reading, conversation prompt, and push notification
• Mutual mood check-in with reciprocal reveal
• One-time compatibility report as the paywall moment
• Partner invite flow and RevenueCat subscription covering both users
• Skip for v1: Android at launch, chat between partners, tarot and extra divination modes, widgets

Build Synastry, a daily astrology app for couples. Stack: React Native with Expo, Claude API for reading generation, Swiss Ephemeris (via the sweph library) for chart math, RevenueCat for subscriptions.

Core flow: user enters both partners' birth date, time, and place (partner two can be entered by the subscriber — do not block on the partner installing). The app computes both natal charts and the synastry aspects between them with the ephemeris library. Each night a batch job generates tomorrow's shared reading: current transits are computed as structured data (planet, aspect, orb, houses touched in each chart) and passed to Claude with the couple's synastry summary to produce a 150-word daily reading, one conversation prompt, and a one-line theme for the push notification. Both partners see the same reading — that shared object is the product. Each partner logs a daily mood emoji; when both have checked in, each can see the other's, a reciprocity mechanic that drives second-user retention.

Non-obvious details: never let Claude do chart math — compute all aspects deterministically and pass them as JSON, with the LLM only writing prose, or accuracy-obsessed astrology users will catch errors. Cache one reading per couple per day at generation time; marginal content cost stays near zero.

Screens: onboarding with dual birth-chart entry, paywall, today (shared reading, prompt, mood check-in), compatibility report, partner invite, settings.

Pricing: $9.99/mo or $59.99/yr covering both partners; invite unlocks a free week.