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Update K2 mode for 2025.3 #5208

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17 changes: 2 additions & 15 deletions docs/topics/k2-compiler-migration-guide.md
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Expand Up @@ -522,7 +522,7 @@ Starting with Kotlin 2.0.0, the Kotlin K2 compiler is enabled by default.
To upgrade the Kotlin version, change it to 2.0.0 or a later release in your [Gradle](gradle-configure-project.md#apply-the-plugin) and
[Maven](maven.md#configure-and-enable-the-plugin) build scripts.

To have the best experience with IntelliJ IDEA or Android Studio, consider [enabling K2 mode](#support-in-ides)
To have the best experience with IntelliJ IDEA or Android Studio, use [K2 mode](#support-in-ides)
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@zamulla zamulla Dec 4, 2025

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Should we say right here that IDEA doesn't even have the option to not use it? It feels a little disjointed to do a call to action and then follow a link that says that there is no action.

in your IDE.

### Use Kotlin build reports with Gradle
Expand Down Expand Up @@ -557,26 +557,13 @@ For more information on what is possible with build reports, see [Build reports]

K2 mode in IntelliJ IDEA and Android Studio uses the K2 compiler to improve code analysis, code completion, and highlighting.

Starting with IntelliJ IDEA 2025.1, K2 mode is [enabled by default](https://blog.jetbrains.com/idea/2025/04/k2-mode-in-intellij-idea-2025-1-current-state-and-faq/).
IntelliJ IDEA 2025.3 and later always uses K2 mode.

In Android Studio, you can enable K2 mode starting with 2024.1 by following these steps:

1. Go to **Settings** | **Languages & Frameworks** | **Kotlin**.
2. Select the **Enable K2 mode** option.

### Previous IDE behavior {initial-collapse-state="collapsed" collapsible="true"}

If you want to go back to the previous IDE behavior, you can disable K2 mode:

1. Go to **Settings** | **Languages & Frameworks** | **Kotlin**.
2. Deselect the **Enable K2 mode** option.

> We plan to introduce [Stable](components-stability.md#stability-levels-explained) language features after Kotlin 2.1.0.
> Until then, you can continue to use the previous IDE features for code analysis, and you won't encounter any code highlighting
> issues due to unrecognized language features.
>
{style="note"}

## Try the Kotlin K2 compiler in the Kotlin Playground

The Kotlin Playground supports Kotlin 2.0.0 and later releases. [Check it out!](https://pl.kotl.in/czuoQprce)
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2 changes: 1 addition & 1 deletion docs/topics/releases.md
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Expand Up @@ -121,7 +121,7 @@ Kotlin has full out-of-the-box support in [IntelliJ IDEA](https://www.jetbrains.

K2 mode in IntelliJ IDEA and Android Studio uses the K2 compiler to improve code analysis, code completion, and highlighting.

Starting with IntelliJ IDEA 2025.1, K2 mode is [enabled by default](https://blog.jetbrains.com/idea/2025/04/k2-mode-in-intellij-idea-2025-1-current-state-and-faq/).
IntelliJ IDEA 2025.3 and later always uses K2 mode.

In Android Studio, you can enable K2 mode starting with 2024.1 by following these steps:

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43 changes: 15 additions & 28 deletions docs/topics/run-code-snippets.md
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Expand Up @@ -4,66 +4,53 @@ Kotlin code is typically organized into projects with which you work in an IDE,
if you want to quickly see how a function works or find an expression's value, there's no need to create a new project
and build it. Check out these three handy ways to run Kotlin code instantly in different environments:

* [Scratch files and worksheets](#ide-scratches-and-worksheets) in the IDE.
* [Scratch files](#ide-scratches-and-worksheets) in the IDE.
* [Kotlin Playground](#browser-kotlin-playground) in the browser.
* [ki shell](#command-line-ki-shell) in the command line.

## IDE: scratches and worksheets
## IDE: scratches {id="ide-scratches-and-worksheets"}

IntelliJ IDEA and Android Studio support Kotlin [scratch files and worksheets](https://www.jetbrains.com/help/idea/kotlin-repl.html#efb8fb32).
IntelliJ IDEA and Android Studio support Kotlin [scratch files](https://www.jetbrains.com/help/idea/kotlin-repl.html#efb8fb32).

* _Scratch files_ (or just _scratches_) let you create code drafts in the same IDE window as your project and run them on the fly.
Scratches are not tied to projects; you can access and run all your scratches from any IntelliJ IDEA window on your OS.
_Scratch files_ (or just _scratches_) let you create code drafts in the same IDE window as your project and run them on the fly.
Scratches are not tied to projects; you can access and run all your scratches from any IntelliJ IDEA window on your OS.

To create a Kotlin scratch, click **File** | **New** | **Scratch File** and select the **Kotlin** type.

* _Worksheets_ are project files: they are stored in project directories and tied to the project modules.
Worksheets are useful for writing pieces of code that don't actually make a software unit but should still be stored together
in a project, such as educational or demo materials.

To create a Kotlin worksheet in a project directory, right-click the directory in the project tree and select
**New** | **Kotlin Class/File** | **Kotlin Worksheet**.

> Kotlin worksheets aren't supported in [K2 mode](https://blog.jetbrains.com/idea/2024/11/k2-mode-becomes-stable/). We're working on providing an alternative with similar functionality.
>
{style="warning"}
To create a Kotlin scratch, click **File** | **New** | **Scratch File** and select the **Kotlin** type.

Syntax highlighting, auto-completion, and other
IntelliJ IDEA code editing features are supported in scratches and worksheets. There's no need to declare the `main()` function
IntelliJ IDEA code editing features are supported in scratches. There's no need to declare the `main()` function
– all the code you write is executed as if it were in the body of `main()`.

Once you have finished writing your code in a scratch or a worksheet, click **Run**.
Once you have finished writing your code in a scratch, click **Run**.
The execution results will appear in the lines opposite your code.

![Run scratch](scratch-run.png){width=700}

### Interactive mode

The IDE can run code from scratches and worksheets automatically. To get execution results as soon as you stop
The IDE can run code from scratches automatically. To get execution results as soon as you stop
typing, switch on **Interactive mode**.

![Scratch interactive mode](scratch-interactive.png){width=700}

### Use modules

You can use classes or functions from a Kotlin project in your scratches and worksheets.

Worksheets automatically have access to classes and functions from the module where they reside.
You can use classes or functions from a Kotlin project in your scratches.

To use classes or functions from a project in a scratch, import them into the scratch file with the
`import` statement, as usual. Then write your code and run it with the appropriate module selected in the **Use classpath of module** list.

Both scratches and worksheets use the compiled versions of connected modules. So, if you modify a module's source files,
the changes will propagate to scratches and worksheets when you rebuild the module.
To rebuild the module automatically before each run of a scratch or a worksheet, select **Make module before Run**.
Scratches and use the compiled versions of connected modules. So, if you modify a module's source files,
the changes will propagate to scratches when you rebuild the module.
To rebuild the module automatically before each run of a scratch, select **Make module before Run**.

![Scratch select module](scratch-select-module.png){width=700}

### Run as REPL

To evaluate each particular expression in a scratch or a worksheet, run it with **Use REPL** selected. The code lines
To evaluate each particular expression in a scratch, run it with **Use REPL** selected. The code lines
will run sequentially, providing the results of each call.
You can later use the results in the same file by reffering to their auto-generated `res*` names (they are shown in the corresponding lines).
You can later use the results in the same file by refering to their auto-generated `res*` names (they are shown in the corresponding lines).
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@zamulla zamulla Dec 4, 2025

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Suggested change
You can later use the results in the same file by refering to their auto-generated `res*` names (they are shown in the corresponding lines).
You can later use the results in the same file by referring to their auto-generated `res*` names (they are shown in the corresponding lines).


![Scratch REPL](scratch-repl.png){width=700}

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