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+# Amethyst Builder Skill
+
+Build customized Amethyst Nostr clients for Android. Fork, rebrand, customize, and distribute your own version.
+
+## Overview
+
+[Amethyst](https://github.com/vitorpamplona/amethyst) is the premier Nostr client for Android. This skill enables you to:
+- Create rebranded versions (custom name, package, icons)
+- Build F-Droid-compatible releases (no Google Play dependencies)
+- Add or modify features
+- Sign and distribute APKs
+
+## Prerequisites
+
+### Required Tools
+
+1. **Java 21** (via SDKMAN)
+   ```bash
+   curl -s "https://get.sdkman.io" | bash
+   source "$HOME/.sdkman/bin/sdkman-init.sh"
+   sdk install java 21.0.5-tem
+   sdk use java 21.0.5-tem
+   ```
+
+2. **Android SDK**
+   - Command-line tools from https://developer.android.com/studio#command-line-tools-only
+   - Required components: build-tools, platform-tools, platforms;android-35
+
+3. **Git** for cloning the repository
+
+### Environment Setup
+
+```bash
+export ANDROID_HOME=$HOME/Android/Sdk
+export PATH=$PATH:$ANDROID_HOME/cmdline-tools/latest/bin
+export PATH=$PATH:$ANDROID_HOME/platform-tools
+```
+
+## Build Workflow
+
+### 1. Clone the Repository
+
+```bash
+mkdir -p ~/projects/your-app-name
+cd ~/projects/your-app-name
+git clone https://github.com/vitorpamplona/amethyst.git .
+```
+
+### 2. Create Signing Key
+
+```bash
+keytool -genkeypair -v \
+  -keystore ./release-key.jks \
+  -alias your-app \
+  -keyalg RSA -keysize 2048 \
+  -validity 10000
+```
+
+Create `keystore.properties` in project root:
+```properties
+storeFile=release-key.jks
+storePassword=your-password
+keyAlias=your-app
+keyPassword=your-password
+```
+
+### 3. Configure Signing
+
+Add to `amethyst/build.gradle` inside the `android {}` block:
+
+```gradle
+def keystorePropertiesFile = rootProject.file("keystore.properties")
+def keystoreProperties = new Properties()
+if (keystorePropertiesFile.exists()) {
+    keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
+}
+
+signingConfigs {
+    release {
+        if (keystorePropertiesFile.exists()) {
+            storeFile rootProject.file(keystoreProperties['storeFile'])
+            storePassword keystoreProperties['storePassword']
+            keyAlias keystoreProperties['keyAlias']
+            keyPassword keystoreProperties['keyPassword']
+        }
+    }
+}
+```
+
+Update the release buildType to use the signing config:
+```gradle
+buildTypes {
+    release {
+        signingConfig signingConfigs.release
+        // ... existing config
+    }
+}
+```
+
+### 4. Disable Google Services (Required for F-Droid)
+
+**⚠️ CRITICAL:** The Google Services plugin fails when you change the package name. For F-Droid builds, disable it.
+
+Edit `amethyst/build.gradle`, comment out the plugin:
+```gradle
+plugins {
+    alias(libs.plugins.androidApplication)
+    alias(libs.plugins.jetbrainsKotlinAndroid)
+    // alias(libs.plugins.googleServices)  // DISABLED for F-Droid
+    alias(libs.plugins.jetbrainsComposeCompiler)
+}
+```
+
+### 5. Build
+
+```bash
+source "$HOME/.sdkman/bin/sdkman-init.sh"
+sdk use java 21.0.5-tem
+./gradlew assembleFdroidRelease
+```
+
+**Build time:** ~9 minutes first build, faster on subsequent builds.
+
+### 6. Locate APKs
+
+Output directory: `amethyst/build/outputs/apk/fdroid/release/`
+
+Files generated:
+- `amethyst-fdroid-arm64-v8a-release.apk` - ARM64 (most phones)
+- `amethyst-fdroid-universal-release.apk` - All architectures (larger)
+
+## Customizations
+
+### Change App Name
+
+Edit `amethyst/src/main/res/values/strings.xml`:
+```xml
+<string name="app_name" translatable="false">YourAppName</string>
+<string name="app_name_debug" translatable="false">YourAppName Debug</string>
+```
+
+### Change Package ID
+
+Edit `amethyst/build.gradle`:
+```gradle
+android {
+    defaultConfig {
+        applicationId = "com.yourcompany.yourapp"
+    }
+}
+```
+
+### Change Project Name
+
+Edit `settings.gradle`:
+```gradle
+rootProject.name = "YourAppName"
+```
+
+### Change App Icon
+
+Replace icon files in:
+- `amethyst/src/main/res/mipmap-*/ic_launcher.webp`
+- `amethyst/src/main/res/mipmap-*/ic_launcher_round.webp`
+
+### Add Client Tag to Posts
+
+Make your app identify itself on posts with `["client", "YourAppName"]`.
+
+**1. Create tag builder extension:**
+
+Create `quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip01Core/tags/clientTag/TagArrayBuilderExt.kt`:
+```kotlin
+package com.vitorpamplona.quartz.nip01Core.tags.clientTag
+
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip01Core.core.TagArrayBuilder
+
+fun <T : Event> TagArrayBuilder<T>.client(clientName: String) = 
+    addUnique(arrayOf(ClientTag.TAG_NAME, clientName))
+```
+
+**2. Add to TextNoteEvent:**
+
+Edit `quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip10Notes/TextNoteEvent.kt`:
+
+Add import:
+```kotlin
+import com.vitorpamplona.quartz.nip01Core.tags.clientTag.client
+```
+
+In both `build()` functions, add after `alt(...)`:
+```kotlin
+client("YourAppName")
+```
+
+### Modify Default Relays
+
+Edit relay configuration in `quartz/src/main/java/com/vitorpamplona/quartz/nip01Core/relay/` or the UI settings files.
+
+## Troubleshooting
+
+### google-services.json error
+Disable the Google Services plugin (see step 4).
+
+### Java version error
+```bash
+sdk use java 21.0.5-tem
+java -version  # Must show 21.x
+```
+
+### Out of memory
+Edit `gradle.properties`:
+```properties
+org.gradle.jvmargs=-Xmx4g -XX:MaxMetaspaceSize=512m
+```
+
+### Clean build
+```bash
+./gradlew --stop
+./gradlew clean
+./gradlew assembleFdroidRelease
+```
+
+## Distribution
+
+Deploy APKs via:
+- **Surge.sh:** `surge ./releases your-app.surge.sh`
+- **Zapstore:** Submit to zapstore.dev
+- **Direct download:** Host on any web server