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Kotlin · Android

Amper Is Dead: JetBrains Folds Its Build Tool Into a Unified Kotlin CLI

By RockByte ·
Read original on juejin.cn ↗ Google Translate ↗ Alt translation

A single `kotlin` CLI that builds, tests, and publishes JVM libraries to Maven Central without Gradle or external GPG tooling lowers the setup tax for new Kotlin projects and makes the toolchain scriptable by AI agents. The Alpha designation means JetBrains is committing to long-term support, so teams evaluating Kotlin now have a supported, lighter alternative to the Gradle monolith.

Summary

The standalone Amper build tool is gone. JetBrains shipped Kotlin Toolchain 0.11, which swallows all of Amper's functionality into a unified `kotlin` command-line entry point now in Alpha. The tool covers the full lifecycle — init, build, run, test, package, and publish — plus new JVM library publishing to Maven Central with automatic PGP signing, sources, and javadoc handling.

Plugin authors get a reworked API with custom checks, public commands, and a unified `generated` node for registering outputs. C interop bindings now generate from definition files, and the IDE downloads library sources in the background after sync. Terminal output and compiler diagnostics also got a visual refresh.

The rename signals a strategic pivot: instead of fighting Gradle's dominance, JetBrains is building a CLI-first toolchain that AI agents can invoke directly. Global installation via SDKMAN! means the `kotlin` command works from any directory, and wrapper scripts keep per-project version pinning intact.

Takeaways
— Amper is discontinued; all its features now live inside Kotlin Toolchain, which enters Alpha with the 0.11 release.
— One `kotlin` command covers project creation, building, running, testing, packaging, and publishing.
— JVM library publishing to Maven Central is built in — sources JAR, javadoc JAR, PGP signing, and checksums are handled automatically.
— Global installation via SDKMAN! (`sdk install kotlintoolchain`) lets the `kotlin` command run from any directory while per-project wrapper scripts pin versions.
— C interop bindings now generate from `.def` files placed in a module's `cinterop` folder, with IDE assistance during sync.
— Plugin development adds `checks` (custom quality gates for `kotlin check`), `commands` (public task entry points), and a `generated` node to register outputs.
— The `run` command auto-selects the correct module and platform when only one option is viable on the current host.
— Library source code downloads in the background after project sync, so the IDE is usable immediately.
— Module-level dependency resolution now matches CLI behavior, fixing version mismatches and false editor warnings.
— Default tool versions bumped: Kotlin 2.3.21, Compose Hot Reload 1.1.1, KSP 2.3.7, Ktor 3.4.3, SpringBoot 4.0.6, JUnit Platform 6.0.3.
— Amper users must manually replace wrapper scripts with `kotlin` and `kotlin.bat`; automatic migration is not supported.
Conclusions

JetBrains is conceding that a new build tool cannot unseat Gradle's JVM monopoly and is instead betting on a CLI-first toolchain that AI agents can drive.

The Alpha label on a tool that absorbed a previously separate project signals urgency — AI coding assistants need scriptable build commands more than they need another plugin ecosystem.

Built-in Maven Central publishing with automatic signing removes a persistent friction point that has pushed JVM library authors toward Gradle plugins or manual scripts.

Global install plus per-project wrapper scripts is the same pattern Node (nvm) and Rust (rustup) use; Kotlin is catching up to that ergonomic standard.

Module-level dependency resolution parity between IDE and CLI closes a long-standing class of bugs where the editor showed errors the command line did not.

Renaming `lib` to `kmp/lib` is a small change that prevents the kind of ambiguous naming that causes misconfiguration in multiplatform projects.

Concepts & terms
Kotlin Toolchain
A unified CLI tool from JetBrains that replaces Amper and provides a single `kotlin` command for creating, building, running, testing, packaging, and publishing Kotlin projects.
Amper
JetBrains' previous experimental build tool, now discontinued and fully merged into Kotlin Toolchain.
Cinterop
Kotlin/Native's mechanism for generating Kotlin bindings to C libraries from `.def` definition files, now supported directly in Kotlin Toolchain.
Wrapper scripts
Project-local `kotlin` and `kotlin.bat` scripts that pin a specific toolchain version, ensuring reproducible builds regardless of the globally installed version.
Maven Central Publisher Portal
The web interface for publishing artifacts to Maven Central; Kotlin Toolchain automates the packaging and signing steps but still requires portal-based verification unless `publishingMode: auto` is set.
Source: juejin.cn ↗ Google Translate ↗ Backup ↗