Primal needed a Nostr social client for Android that could stand next to mainstream social apps on speed and polish, not read as a protocol demo. Nostr itself was young, so the app had to be built greenfield and keep pace as the protocol moved under it. We came in at kickoff, and have kept it production-grade through every release since. The engagement runs three years and counting.

What began as the Android client has grown, over three years, into the core of Primal’s mobile stack: the social app, a long-form reading experience, live streaming and media playback, two generations of Bitcoin wallet, a remote signer, and the cross-platform libraries underneath them.

Social client. The social experience covers a real-time feed, search, media, direct messages, profiles, and threaded conversations. The feed is not one fixed format. Several feed types are on offer, and a feed heavy with images and video renders in a more visual layout built around the media rather than a plain text timeline. Posts can also be polls, and a vote can be cast as a plain tap or as a zap, sending real sats to the option a person backs.

Reads. Reads is the long-form half of Primal: a dedicated reading experience with its own article-focused feeds, separate from the social timeline. It renders Markdown cleanly and supports in-text highlighting that few other Nostr clients implement. Comments on an article are themselves Nostr notes, so the discussion under a piece is native to the protocol rather than a bolted-on system.

Live and media. The app handles more than images and video in the feed. Live streams are watchable in-app, and an audio link posted to Nostr gets a real player rather than a dead link. Playback integrates with the operating system: picture-in-picture for video, plus background video and audio, so a stream or a track keeps running while the user moves elsewhere in the app or leaves it.

Bitcoin wallet. Primal has shipped two wallets under this engagement. The first was custodial and ran in production for more than two years. We then replaced it with a non-custodial, Spark-based Bitcoin and Lightning wallet, and moved the existing userbase onto it in a single tap.

Signer. The signer lets a user sign Nostr events without handing their private key to every app they touch. It covers NIP-46 remote signing, where a Nostr web app delegates signing to the phone, and NIP-55 local signing on-device, both behind a single session model. It ships on iOS and Android.

Cross-platform libraries. Beneath the wallet and the signer sit cross-platform libraries: the shared code each was extracted into. They are deliverables in their own right, with their own consumers. Primal’s iOS app is built directly on these libraries, and we work daily with the developers integrating them.

Several decisions shaped the codebase more than the rest.

Local-first data. Early on we proposed a local database on every device as the single source of truth, even though Primal already ran a caching server that would have done the job. The team weighed the trade-off and agreed. Three years on, the app feels the same on fiber and on weak connections.

Multi-platform extraction. The split goes deeper than a shared module or two. Primal’s entire business logic and data layer live in shared multiplatform code, outside the Android project, leaving Android with just the UI and its screen logic. Two parts of that shared code, the wallet and the signer, are packaged as standalone libraries and run in production on iOS. The rest could run there too, but consuming it on iOS needs refactoring we have chosen not to take on yet.

Multi-account and multi-wallet by design. A person can hold several Nostr accounts in the app, and several wallets, and move between them instantly. That is an architectural choice made at the data layer: an account and a wallet are each treated as a first-class, swappable context, not a single default with extra ones bolted on later. Switching between them is a state change measured in milliseconds.

Standards-first. Everything is built on the open Nostr protocol. Across the whole app, it follows the published standards rather than proprietary variants. That keeps Primal interoperable: a user’s identity, content, and connections are not locked to one client but move with them across the Nostr ecosystem.

The engagement produced two outcomes: a production app, and the cross-platform libraries underneath it.

The app. Primal is among the most widely used Nostr clients, live in production across Android and iOS. Primal 3.5 shipped weeks ahead of the other platforms, with no client-reported issues in its first weeks. When the non-custodial wallet launched, roughly 14,000 users migrated within two weeks, moving hundreds of millions of sats with zero technical defects in production.

The libraries. The wallet and the signer each became a standalone cross-platform library, now running in production on iOS as well, and reusable well beyond this app. Each has its own case study: