Kotlin Multiplatform v1.9.20-Beta Release Notes & Developer Guide
What's New for Developers
Kotlin 1.9.20-Beta focuses on stabilizing the K2 compiler with over 100 bug fixes, particularly for Kotlin Multiplatform and Analysis API. Major improvements include WebAssembly backend enhancements, new enumEntries intrinsic support across platforms, and stricter validation for expect/actual declarations. Performance optimizations in FIR compilation and type resolution provide faster IDE responsiveness.
Highlights
- Analysis API source shadowing feature for improved extension resolution
- Significant performance improvements in K2 FIR compilation and type resolution
- Multiple K2 compiler fixes for Kotlin Multiplatform expect/actual declarations
- WebAssembly backend enhancements including Node.js 20 compatibility
- New enumEntries intrinsic implementation across JVM, Native, and Wasm
- Enhanced annotation support with type parameters and improved validation
Breaking Changes
- KMP: prohibit implicit actualization via Java for expect/actual declarations
- KMP: prohibit expect tailrec and expect external modifiers
- Analysis API: forbid providing custom KtLifetimeToken for every analyze call
Deprecations
- Deprecation for open val with backing field and deferred initialization in K1
Recent Releases
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Oct 21, 2026
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Oct 8, 2026
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Sep 30, 2026
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Sep 7, 2026
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Aug 26, 2026
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Aug 12, 2026
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Jul 14, 2026
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Jul 7, 2026
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