Risks of migrating to JetBrains Fleet and Air for Kotlin development

JetBrains ended Fleet distribution on December 22, 2025. The company moved the Fleet technology into a new product called Air, which is an agentic development environment. Teams planning a migration from VS Code or Zed to Fleet in late 2026 face immediate obsolescence because JetBrains ceased all Fleet updates and downloads last year. JetBrains found that rebuilding full IntelliJ capabilities inside Fleet created little value for users. The company decided to focus on agentic workflows after finding that Fleet could not compete as a standalone IDE. This decision leaves current Fleet users depending on tools that may stop working if server-side services like AI Assistant fail. JetBrains researchers confirmed that Fleet did not succeed as a standalone product because it could neither replace IntelliJ IDEA nor find a clear, differentiated niche. Users expressed that switching from existing JetBrains IDEs like PyCharm or WebStorm required a strong reason that Fleet did not provide.

Resource costs and missing functionality

Fleet lacks the massive plugin ecosystem and customization options of VS Code. Users moving from VS Code or Zed will find fewer themes and less functionality. Installation requires the JetBrains Toolbox application. Fleet does not support code formatting or the "go to definition" functionality in its current state. The UI relies on a JSON settings file and lacks a dedicated interface for run configurations. While Fleet aims for a lightweight feel, it uses almost 12 times more memory than VS Code when running without smart mode. This memory consumption creates a significant hurdle for developers using low-spec hardware. You should check your system specifications before committing to this tool. Developers migrating from VS Code to Fleet must account for the fact that the editor consumes nearly twelve times the memory of its competitor, which creates a significant bottleneck for teams running multiple containerized environments or heavy local services. Fleet’s user interface feels unpolished because margins, icons, and fonts feel too tight for easy navigation. In testing, Fleet smart mode takes 2 minutes to index a project and requires 3 to 4 seconds to start the IntelliJ instance. This delay makes the editor feel less responsive than VS Code.

Kotlin stability and collaboration gaps

The K2 compiler provides an analysis phase up to 376% faster than previous generations. This speed comes from the new Frontend Intermediate Representation. However, Fleet smart mode requires 3 to 4 seconds to start the IntelliJ instance, which delays code completion. This delay offsets the speed gains of the K2 compiler. Kotlin developers also rely on the K2 compiler to unify the backend for JVM, Native, WebAssembly, and JavaScript. The K2 engine tracks "synthetic data flow variables" to improve smart-cast accuracy. The compiler also identifies the nearest common ancestor in class hierarchies. Kotlin 2.0 also enables context parameters and stable guard conditions across the entire ecosystem.

Teams using JetBrains for real-time collaboration face a critical deadline. JetBrains announced the discontinuation of Code With Me in March 2026. This tool reaches its end of life in Q1 2027. Teams must find alternatives like VS Code Live Share, which supports up to 30 participants and provides independent cursors for each user. Replit provides an alternative with a Kanban board for project management and a Pro plan that supports 15 collaborators. Teams moving from Zed will face a larger transition because Zed provides local models for both its Agent and its Edit Prediction system. VS Code users can connect to Ollama and Foundry Local for chat and agent workflows without a GitHub account. Will the new Air environment provide the same level of synchronous control required for intensive pair programming?