Compose Multiplatform 1.12 and the Hot Reload MCP server
Short answer: the latest Compose Multiplatform is 1.12.1, released on September 22, 2026, after 1.12.0 in late August. The headline feature is an experimental MCP server in Compose Hot Reload: an AI coding agent can reload your running desktop app, take screenshots, read the semantic tree and logs, and click or type to check its own edits. Connect it by pointing your agent’s MCP config at the hotMcpServer Gradle task. 1.12 also brings automatic font fallback on web and a v2 window and dialog API for desktop.
Hot Reload MCP tools
From JetBrains’ Compose Hot Reload documentation, read 1 October 2026. The README lists all tools and parameters.
| Tool | What the agent can do |
|---|---|
| reload | Recompile the project and hot-reload changed classes |
| take_screenshot | Capture the current state of an app window |
| get_semantic_tree | Read the Compose semantic tree to understand the UI |
| get_logs | Read recent logs, including runtime exceptions |
| click, type_text, scroll | Simulate user input to test flows |
Connecting an AI agent
Hot Reload runs your shared UI in the desktop target, so your project needs one; from Compose Multiplatform 1.10.0 the Hot Reload plugin is bundled and on by default for such projects. It needs Kotlin 2.1.20 or later and a JVM target of Java 21 or earlier. To connect an agent, add an MCP server whose command is
./gradlew with the arguments --no-daemon, --quiet, --console=plain and hotMcpServer, for example in .mcp.json. Gradle matches the short name to the target task; if a module has several JVM targets, use the full name, such as :composeApp:hotMcpServerJvm or :app:hotMcpServerDesktop. With several windows open, the agent can list them and pick one. On the Apple side, the same idea arrived in Xcode, see the Xcode MCP server.Web, iOS and desktop changes
Web: characters your fonts don’t cover used to show as empty boxes; Compose for web now downloads the matching Noto font subset on demand and recomposes the text, so Japanese, Arabic, Devanagari and emoji render without bundling fonts. A box can appear briefly while the font loads. iOS: lazy layouts scroll more smoothly because item deactivation moved out of the drawing phase, and the Skia update to Milestone 150 fixes duplicate-symbol conflicts in apps that bundle their own Skia. Desktop: the experimental v2
WindowState and DialogState API in androidx.compose.ui.window.v2 lets you choose the screen, set minimum and maximum sizes, size a window to its content and place dialogs relative to their parent. LocalSystemTheme is deprecated.Versions and requirements
Compose Multiplatform 1.12.1 is based on Jetpack Compose 1.12.1, covered in the latest Compose BOM and Compose 1.12; JetBrains says its releases usually trail Jetpack Compose by one to three months. Its Material 3 artifact is still
1.12.0-alpha03, based on Material 3 1.5.0-alpha22, and its Navigation 3 artifact is 1.1.2, see Navigation 3. Minimum platforms are Android 5.0, iOS 14, macOS 13 on Apple silicon, Windows 10, Ubuntu 20.04 and browsers with WasmGC. Desktop apps need JDK 11 or later, and JDK 17 or later to package native distributions. For iOS styling, see Compose Multiplatform and Liquid Glass.Where Censuus fits
One codebase on every platform helps you ship; being found brings people to it. Censuus ranks apps by the visits they draw, and adding your app is free through the List my app form. Placement comes from traffic and sponsorship: apps climb on the visits they draw, and a sponsor can pay to rise higher.
Frequently asked questions
What is the latest version of Compose Multiplatform?
Compose Multiplatform 1.12.1, released on September 22, 2026. 1.13.0 is in alpha.
How do I connect an AI agent to Compose Hot Reload?
Configure an MCP server in your agent, for example in .mcp.json, that runs ./gradlew --no-daemon --quiet --console=plain hotMcpServer. This needs Compose Multiplatform 1.12.0 or later and a desktop target.
Does Compose Hot Reload work on Android?
JetBrains documents it for the desktop target and says other targets are being explored. You can run shared UI code in the desktop app as a sandbox while you work.
Why is Compose Hot Reload not working?
Check the requirements JetBrains lists: a desktop target, Kotlin 2.1.20 or later, and a JVM target of Java 21 or earlier. Before Compose Multiplatform 1.10.0 you also had to add the plugin by hand.
How does Compose Multiplatform for web handle missing characters?
From 1.12, it downloads the needed Noto font subset when it finds unsupported characters and recomposes the text.
Guides for app developers
- How to market an app: a stage-by-stage plan
- Submit your app for free
- How to get your app to show up in Google search
- How to get your app recommended by AI assistants
- Free app promotion sites, checked for dofollow
- App store optimization checklist: what Apple and Google actually say
- App launch checklist: iOS and Android, step by step
- How to find beta testers for your app
- How to get more app reviews without breaking the store rules
- How to get your app featured on the App Store and Google Play
- App Store and Google Play screenshot sizes: what you must upload
- How to promote an app on Google Play with Play Console’s own tools
- How to promote an iOS app with App Store Connect’s own tools
- App Store keywords: how to fill the 100-character field
- How to market a fitness app: what Apple and Google let you claim
- How to market a kids app: the store rules that shape it
- How to market a finance app: the store rules to know first
- How to market a dating app: the store rules that shape it
- How to market a subscription app: what the stores require of your offer
- How to market a mobile game: the store rules that shape it
- Apple Ads MCP: connect an AI assistant to your campaigns
- How to promote an app on TikTok with creators
- How to promote an app on YouTube with creators
- How to market a VPN app: the store rules to know first
- How to market an AI app: the store rules that shape it
- How to market an education app: schools, parents and learners
- How to localize your App Store and Google Play listing
- Android vitals and Google Play visibility: the thresholds that hide apps
- App Store and Google Play age ratings: what drives them
- App Store privacy labels and Google Play Data safety: what to declare
- Common App Store rejection reasons and how to avoid them
- How to get the first users for your app
- App preview video specs: App Store sizes, length and rules, and the Google Play video
- App Store custom product pages, and the Google Play version
- App icon size for the App Store and Google Play
- App Store phased release and Google Play staged rollouts
- App Store subtitle and promotional text: limits and how to use them
- Google Play feature graphic: size, placement and rules
- TestFlight public link: set it up, limit it, and fix it when it does not work
- App Store promo codes and offer codes: how they work and their limits
- App Store A/B testing: product page optimization and Google Play experiments
- App Store in-app events: limits, badges and media sizes
- App Store Connect analytics: what each metric means
- Google Play store listing reports: clicks, CTR and the 2026 changes
- Google Play target API level requirements for 2026
- Android developer verification: what changed on September 30, 2026
- App Store and Google Play fees in 2026
- Google Play’s 12 testers for 14 days rule, explained
- How to transfer an app to another developer account
- How to remove an app from the App Store and Google Play
- The app account deletion requirement on the App Store and Google Play
- Google Play 16 KB page size requirement: dates, checks and fixes
- Declared Age Range and Play Age Signals: age assurance APIs for app developers
- Xcode 26 and the iOS 26 SDK requirement for App Store Connect
- The iOS privacy manifest: what to declare and how
- Accessibility Nutrition Labels: what to declare on your App Store page
- Google Play’s photo and video permissions policy, explained
- Google Play Billing Library version requirement: what you need to ship now
- App Tracking Transparency: when to ask and how
- App Store Connect API key: create it, store it, use it
- How to submit an In-App Purchase for review
- The Play Integrity API: what it checks and how to use it
- How long app review takes on the App Store and Google Play
- Google Play policy updates in 2026, with the deadlines
- Rosetta 2 end of support: what Mac developers need to do
- Monthly subscriptions with a 12-month commitment on the App Store
- Subscription Bundles, Suites and multiseat purchases on the App Store
- Sign in with Apple private relay email and the new private.icloud.com domain
- App Store Server Notifications V2: switching from V1 and handling every event
- Migrating to StoreKit 2: what is deprecated and what replaces it
- App Store creative assets: headers and search result visuals in iOS 27
- On-Demand Resources is deprecated: moving to Background Assets
- Time Allowances in iOS 27: how your app gets its category
- Android Contact Picker and the new READ_CONTACTS rules
- The Android 17 location button and Google Play’s precise location rules
- Phone verification without READ_CALL_LOG: what replaces call-based checks
- Apple’s EU business terms from October 1, 2026
- Android 17 app memory limits: detect, test and stay under them
- The Android 17 local network permission
- Android 17 background audio hardening
- Cleartext HTTP and certificate transparency on Android 17
- Android 17: lock-free MessageQueue and static final fields
- Android 17 ignores orientation lock and resizability on large screens
- Android 17 behavior changes: a checklist for target SDK 37
- Preparing your app for iPhone Duo
- Google Play subscription grace period and account hold
- Getting your Android app ready for Googlebook
- The Android 17 Handoff API
- ADB Wi-Fi 2.0 wireless debugging
- Android AppFunctions: your app as on-device tools for AI agents
- Android Live Updates: how to qualify for a promoted notification
- App Store Connect webhooks
- Apple Foundation Models: on-device vs Private Cloud Compute
- Using Claude, Codex and other agents in Android Studio
- Gemini Nano for Android developers
- Firebase AI Logic: the App Check deadline and Gemini 2.5 shutdowns
- Swift 6.4: what’s new for app developers
- The Swift SDK for Android
- Publishing your game on Android Auto and Android Automotive OS
- Liquid Glass in a Compose Multiplatform app
- Expo SDK 58: when it ships and what changes
- Device Hub in Xcode 27
- Using the Xcode MCP server with Claude Code, Codex and other agents
- Xcode 27: release, requirements and point releases
- Gemma 4 and Android skills in Android Studio
- The UIScene life cycle is required in iOS 27
- Migrating to Android Gradle plugin 9
- Navigation 3 for Jetpack Compose
- Kotlin 2.4, 2.4.20 and the road to 2.5
- Upgrading your app build to Gradle 9
- The latest Compose BOM and Compose 1.12
- Opting out of Liquid Glass with UIDesignRequiresCompatibility
- Flutter 3.47 and the latest stable version
- React Native 0.87 and the latest version
- Android Studio Quail 4 and what comes next
- CocoaPods goes read-only: what changes and when
- Fixing YouTube Error 153 in embedded players
- Fixing “APNS token has not been set yet” in Firebase Messaging
- Older iOS Simulator runtimes and Rosetta destinations in Xcode
- Fixing the fmt consteval error in React Native on Xcode 26.4
Put your app in the ranking
Censuus ranks apps by the visits they draw and by sponsorship, no bots. Listing is free; sponsorship raises placement.