Introducing Postr, a deliberately small Nostr composer for Android. Post. That's all. A durable outbox survives airplane mode, process death, and unreliable relays. Once Amber signs a note, Postr keeps working until it can verify that exact event on your relays. Private keys stay in Amber. Postr requests only two signing capabilities: kind-1 notes and file-scoped Blossom upload authorizations. It cannot read DMs, sign unrelated event kinds, or publish a relay list. Postr also includes verified Blossom attachments, mention search, opt-in link previews, and a zero-blue night theme you can retint end to end. Install: https://zapstore.dev Code, issues, and contributions: https://gitworkshop.dev//postr Inside the architecture: #postr #nostr #android #foss #grownostr