MPS

The list below only mentions user-visible changes and does not include refactorings such as dead-code removal or moving functionality around.

BaseLanguage

• 🆕 IForEachLoop interface to capture commonalities between various foreach loops.
• ↗️ Intention ‘Add Field For Unused Param’ got a slightly nicer name
• ↗️ BaseLanguage no longer depends on the behavior language
• ↗️ Resolution of unknown elements during Java parsing will not add a used language when it already comes from a used devkit.
• 🐞 Fixed a few NPEs when accessing scope or class hierarchy for a detached node

Behavior language

• ↗️ Generated code changes to improve diagnostics: parameter names are now tracked, no code is generated for empty constructors, and invoking some internal implementation methods directly to shorten stack traces.
• ↗️ Removed the dependency of the behavior language on the kernel subsystem.

Core

• ↗️ Diagnostics improvements (better printout from ClassLoaderManager, extra trace from EDTExecutor).
• ↗️ Continued internal refactoring towards per-project repositories.

Editor

• ↗️ The : cell was made non-selectable in Boolean style items.
• ↗️ Avoid auto-fixing references in nodes that are no longer open in the editor.

Find Usages

• ↗️ A nicer tab name for module dependency usages.

Make

• ↗️ The RCP build script wizard was updated to reflect the fact that the MPS Make plugin now depends on the Java plugin.

Migrations

• ↗️ Minor improvements in the migration notification (“Some languages in the project are not deployed…”)

MPS-extensions

• 🆕 blutil language was extended with several additional operations, such as ’elvis’ operator ?:, integer ranges ([2..5]), select with index, and more. For more details, see the changelog.

• 🆕 EditorTestLifecycleMethods attribute and related intentions were added to the nl.f1re.testing language. With these intentions you can add before/after tests methods to editor tests.

• 🐞 de.itemis.mps.linenumbers Improve line numbers position in diff editors where the line numbers appear to the right of the editor.

• 🐞 de.itemis.mps.linenumbers Fix a NullPointerException that would occur after application shutdown and would be logged e.g. by command line tools. The NPE was caused by failing to properly dispose a Swing timer.

• 🐞 de.itemis.mps.editor.celllayout.runtime Grid layout was broken after previous performance optimization

mbeddr platform

Bugfixes to several languages:

• 🐞 com.mbeddr.mpsutil.filepicker: Solution-relative pickers now work correctly during generation.
• 🐞 com.mbeddr.mpsutil.hyperlink: random exceptions should no longer occur after module reload.
• 🐞 com.mbeddr.mpsutil.interpreter: Throw a more detailed exception when TypedChildConstraint cannot determine the type of a node.
• 🐞 com.mbeddr.mpsutil.interpreter: Generated node URLs now correctly point to the input model instead of the transient model.

KernelF

• no changes in March

mbeddr/mps-gradle-plugin

• 🐞 A minor fix to the MpsMigrate: pass an additional --add-open argument to MPS so that versions 2025.1 and above do not complain at run time.

mps-build-backends

• 🐞 A few fixes to get fewer stack traces logged during backend execution.
• 🆕 The execute backend can now exit with a custom error code: if the executed method returns an integer value, this value is used as the backend exit code.

Other projects

• Eugen Schindler from DSLFoundry wrote in to mention that he recently migrated two DSLFoundry projects to MPS 2025.1: mps-UMLRT and mps-metabnf.

• MetaBNF seems to be a catchy name because this is also the name of a new project open-sourced by Porsche. Both projects appear to be focused on generating MPS DSLs from a Backus-Naur Form (BNF) description.

MPS

The main areas of work in February were:

• closer integration with the IDEA platform and being a good citizen of it,
• refactorings and improvements towards replacing the global repository with per-project repositories (a long-term effort),
• deadlock hunting,
• removal of deprecated code,
• various minor bug fixes in areas such as base language data flow with commented out nodes, proper cleanup in editor tests in case of failure, and handling of Java source stubs (MPS models created based on Java sources, as opposed to compiled class files).

MPS-extensions

Optimizing performance of editors showing many similar kinds of images (e.g. checkboxes) and editors using the celllayout language which installs a layout interceptor to modify how MPS lays out its editors.

Line numbers now properly appear when a new editor is opened.

mbeddr

A new language to visualize generator plans, com.mbeddr.mpsutil.genplandiagram.

IETS3 Opensource

• Variability-related improvements

mps-build-backends

In the execute backend (which is a replacement/improvement over the run mps code MPS functionality and the corresponding runMPS Ant task) if the executed method returns an integer value, it will be used as the exit code of the backend. This allows the caller to distinguish between several error conditions.

Additionally, project-loader got some workarounds so that a few scary-looking but harmless stack traces that appeared during MPS startup and shutdown will no longer be logged.

mbeddr/mps-gradle-plugin

The plugin had a minor update to upgrade the dependencies it uses. It will now work with the current MPS prerelease.

MPS

There have been quite a lot of changes in January, so I am splitting them by subsystem.

AI

• Include the mcp-server plugin from IDEA in MPS.

Base Language

• Refactoring: moving code around to reduce the number of cyclic dependencies in the subsystem.
• Classifier.isDescendant() optimized to avoid loading stubs unnecessarily and walk the class hierarchy more efficiently.

Editor

• Cleanup: a deprecated 2-argument cell factory method in the editor language generator was removed, only the no-argument version remains. This affects authors of custom editor cells.

Migrations

• Cleanup: removed unused code, old project migrations (2020 and earlier).
• Refactoring of internals to improve the internal API and reduce the need for model read lock.
• Changes around how language versions and module dependencies are computed - less guessing, version -1 will be used if not stored.

Model Persistence

• New version of binary model persistence (.mpb files). The format now stores versions of languages used by the model. This is related to the changes in the migration subsystem.

Project

• Continued preparations for closer integration with the IDEA platform (workspace model)

Structure

• Cleanup: EnumDataTypeDeclaration_Old and related concepts deprecated several years ago were removed.
• Internal: show ‘concept scope’ in developer mode (concept scope is an experimental, internal feature to designate some concepts as non-referenceable or only referenceable from within the same root node).

Testing

• Cleanup: drop previously deprecated concepts for node tests (NodeTypeSystemWarningCheckOperation and CheckNodeForErrors)

VCS

• UI improvements around conflict resolution

MPS-extensions

• diagrams: to support custom SVG export, the SVGGenerator class is now an object with options (TextAsShape, UseCSS, SetViewBox).
• rich text: Generic placeholders like generic comments can’t be inserted into words anymore (an exception was thrown).
• tables: Prevent inserting a new row node before/after a singular cardinality child node

mbeddr

An exception was fixed in the mpsutil filepicker.

IETS3 Opensource

KernelF

• Physical units:
  • The units Joule, Coulomb and Watt can now have also prefixes with negative metric scaling, e.g., mW (milliwatt). Additionally, some typos have been corrected in the physical units documentation.
  • The precision of number types with prefixed units (e.g. mW or km) was always set to infinite by the typesystem. Now, the precision is as precise as possible.
• ShortLambda Interpreter: Fixed a bug which resulted in a RuntimeErrorType when interpreting ShortLambdas.

Variability

• Viewer for skeleton trees has been improved (better error reporting, more stable, does not break on nodes which are string literals).

specificlanguages/mps-gradle-plugin

I have finally released version 2.0.0 of the plugin, after replacing the buggy artifact transforms with a custom caching solution. A few days later, I released version 2.0.1 which improves compatibility with Gradle configuration cache.

My goal now is to improve the plugin so that it can be used for the build of mbeddr. The main missing features are 1) dependencies on other subprojects and 2) sharing external libraries among several MPS projects in the same repository.

MPS master (version 2026.1)

• Fix for Java stubs being loaded incorrectly sometimes (MPS-39316, also in 2025.3), along with a few improvements to Java stubs (MPS-39356).
• Support for multi-line binary expressions (MPSSPRT-474, not accessible publicly).
• UI color fixes and a new splash screen (MPS-39266 - editor gutter color, MPS-39257 - red color in dependency analyzer tool for the Islands theme, MPS-39370 - the new splash screen).
• Migration listeners were changed from extension points to ModuleRuntime.Extensions (a newer way of implementing extensions with an API that is supposed to be more safe in the face of reloading classes).
• Accommodating the updates of the underlying IDEA platform: fixes related to the product-info.json file, RCP boot classpath, converting a component to a service.
• The HTML page that appears when opening a node by URL now shows international characters in the node name correctly (MPS-39352).
• (Ongoing) Updating the generator_demo sample project to the current best practices (ongoing, MPS-39192).
• (Ongoing) integration of the MPS in-IDE build with JPS (the IntelliJ Platform build system). This should help with implementing a background build in the future. MPS used to be able to build in the background, but this option was disabled because with newer MPS versions it led to deadlocks.

MPS-extensions

• Line numbers are now updated asynchronously for better performance
• The assertions of the ‘compare’ language can now be configured to ignore annotations (as they previously did by default).
• An experimental extension point for customizing concept aliases. This feature is implemented using MPS internals and can break in future MPS versions, but you can try it out and give feedback.
• An extension point to customize intentions (e.g. disable intentions from libraries or change their descriptions). Works with the custom intentions menu.

mbeddr

No changes except integrating the MPS-extensions updates above.

IETS3 Opensource

• Improvements in feature modeling. I do not have enough knowledge to describe them or comment on them.

• The typesystem rules now use nullable ‘as’ casts instead of strict (’:’) casts and KernelF should produce fewer exceptions in unforeseen cases.

mps-build-backends, mbeddr/mps-gradle-plugin

No changes in December.

specificlanguages/mps-gradle-plugin

No changes in December.

The artifact transforms story from November turned out to be more complicated. As pointed out by Sascha Lißon, artifact transforms will not let users share MPS or JBR versions among unrelated projects. The key under which the result of an artifact transform is cached takes into account the complete classpath of the Gradle build script that performs the transform (not just the classpath of the transform itself). This classpath depends on the set of applied plugins and their versions and is likely to be different for different build scripts.

IntelliJ Platform Gradle Plugin hit this problem as well and solved it by implementing its own caching of the extracted distributions. I am almost finished implementing this for the MPS Gradle plugin and I’m going to release the final version 2.0.0 soon.

I list changes on master/main branches only. Some, but not all, of these changes are backported to older versions as well.

MPS master (version 2026.1)

IDE

• Update to the latest IDEA platform.
• Various minor UI improvements. For example, an annoying bug where the project pane selection would jump to the ‘Transient Models’ on every build (if transient models are enabled) was fixed.
• UI performance improvements.

Version Control

• Merge driver improvements (‘do not generate’ flag is now merged properly).
• Merge UI improvements.

Generator

• An initial implementation of conditional generation (MPS-38762).

Editor

• Intentions are now enabled on read-only cells (MPS-33716)
  • This should make the corresponding hack in MPS-extensions unnecessary.

Java

• Javadoc improvements:
  • The javadoc language now uses the text language for its text content, including text in various tags such as @param or @deprecated.
  • Text can now be pasted ‘as Javadoc’ (in addition to ‘as Java statement’ and ‘as Java class content’).

Building and Packaging

• All JARs from mps_home/lib/modules are added to the IDEA layout, making the MPS.ThirdParty module in MPS-extensions unnecessary (the module was removed as a consequence, see MPS-extensions changes below).
• MPS build scripts now have a property, mps.log.dir, that can be used to specify a directory where logs will be written, so that they are not written into the MPS home directory. This allows using one MPS installation in multiple parallel builds.

MPS-extensions

Based on the changelog and commit logs:

• Tables: copy-paste support for tables was added.
• Diagrams: there is now a flag to suppress autolayout-on-init functionality, useful when laying out multiple diagrams in a batch.
• Improvements to spell checking functionality (support for custom dictionaries).
• MPS.ThirdParty solution with stubs of libraries bundled with MPS was removed, MPS.IDEA or MPS.IDEA.Modules can now be used instead.

mbeddr

Based on the changelog and commit logs:

Assessments

• Performance improvement when updating results of previously run queries.
• A new option, ‘always show checkboxes’, to let users check off individual entries without marking the entire containing assessment with an error.
• API change to make the current MPS project available in assessments and assessment scopes.

Action Filter

• UI fixes to make sure the selected action profile stays selected after a restart.
• Filtering now works without having to install an IDEA plugin.

Small improvements

• The search tool has got a new icon to distinguish it from the built-in Find Usages tool window.
• CommandButton#perform got an overload accepting the current project as a parameter.

IETS3 Opensource (KernelF)

Based on the changelog and commit logs. These changes are only present on the MPS 2025.1 branch and haven’t been merged to master yet, but hopefully will be soon.

Added

• The Maven POM now contains all bundled JARs as dependencies with provided scope to help with automated license and vulnerability scanning.
• The Grammar Cells of KernelF editors can now be customized through the extension point EditorCustomization. Optional cells, flag cells, constant cells, substitute cells and side transformations can be customized (activation of substitutions, side transformations, description text, post-processing

Fixed

• NumberLiteral editor no longer breaks if a property macro was used for its value.
• Added missing support for IndexExpr for the operations findFirst and forEach.
• Some editor action descriptions were improved.

mps-build-backends

Added support for the current MPS master (2025.3/2026.1). This required passing an additional --add-opens flag to the JVM when launching MPS and making the remigrate backend (for executing re-runnable migrations) properly wait until MPS is done building its indices.

mbeddr/mps-gradle-plugin

No changes in November, but I am working on a simple change to bump the dependency on mps-build-backends launcher from above. However, this leads to dropping support for older MPS versions, at least in tests.

specificlanguages/mps-gradle-plugin

I wanted to release the final version 2.0.0, but unfortunately my clever use of artifact transforms to share a single MPS installation among multiple projects got derailed.

Gradle 9.1 has begun checking the transformed artifacts to make sure they are not changed after transformation, and since MPS likes to write its logs into its home directory, we did not pass the check. JetBrains has implemented a fix for this issue, but the fix did not work correctly on older MPS versions. So now I am waiting for the fix to the fix to be released and hoping that I will not have to implement a workaround.