February 2026 monthly summary for JetBrains/lets-plot focusing on delivering business value through robust color scales, precise numeric labeling, and a more testable plotting UI, alongside publishing process cleanup. Improvements reduce edge-case visual errors and accelerate release readiness.

January 2026 (2026-01) delivered a substantial upgrade to color-palette capabilities and visualization primitives for JetBrains/lets-plot, focused on business value, visual clarity, and maintainability. Key features were implemented to streamline color-scale usage across plots, improve flexibility for end users, and provide practical demonstrations and documentation to accelerate adoption. The period also included important stability improvements to geom_imshow and related time-scale helpers, reducing runtime errors and ensuring compatibility across common scales.

December 2025 highlights across the Lets-Plot Kotlin ecosystem. Delivered feature-rich plotting improvements, notebook integration enhancements, and stability and maintenance work that together improve user productivity, data visualization capabilities, and platform security. Key outcomes include: Notebook output type control enabling per-cell output type selection with updated demos and better error handling; duration support for Kotlin and Java Duration types with new plotting examples and a bug fix for horizontal geom_boxplot when alpha is specified; a major expansion of plotting capabilities with new geometries, layouts, and missing-values handling; maintenance and compatibility improvements including dependency cleanup and Lets-Plot library upgrades (4.12.x); and Colab rendering stability fixes through refined Colab/Kaggle environment detection.

2025-11 monthly summary for JetBrains/lets-plot and JetBrains/lets-plot-kotlin. Delivered user-facing plotting enhancements, robust rendering/UI improvements, API/compatibility fixes, updated demos/docs, and library upgrades that increase usability, reliability, and cross-environment consistency. These workstreams enable cleaner visuals, easier integration, and faster adoption across projects relying on Lets-Plot.

Month: 2025-10 — Consolidated a set of user-facing and maintainability improvements across JetBrains/lets-plot, focusing on interactivity, facet robustness, identity-scale support, and legend handling. These changes enhance data exploration UX, reduce common errors, and simplify the API surface for future growth.

September 2025 focused on performance, stability, and developer experience across LetsPlot projects. Delivered targeted features, critical bug fixes, and maintainability improvements that enhance plot fidelity, startup time, and documentation quality. The work spans three repositories and includes dependency upgrades, UI/UX refinements, and architecture-level improvements that reduce risk for downstream users and streamline future development.

August 2025 monthly summary focusing on key accomplishments, with emphasis on business value and technical achievements across JetBrains/lets-plot and JetBrains/lets-plot-kotlin. Highlights include data type handling for Polars, visual consistency and correctness fixes, theming improvements, and added demonstrations/documentation to support future changes.

Concise monthly summary for 2025-07 highlighting key features delivered, major bugs fixed, overall impact, and technologies demonstrated across JetBrains/lets-plot, JetBrains/lets-plot-kotlin, and Kotlin/kotlin-jupyter-libraries. Emphasizes business value, stability, and release readiness for the upcoming cycle.

June 2025 monthly summary for JetBrains/lets-plot focusing on delivering time-aware time-series capabilities, stabilization, and reliability improvements.

May 2025: Consolidated cross-language Date/Time reliability by migrating to a unified timezone-aware approach (kotlinx-datetime) and expanding timezone support across Kotlin and Python layers. Key features include a timezone-aware date/time handling overhaul, updated formatting utilities, and propagation of timezone parameters to prevent plotting anomalies. Also delivered cross-platform stability through a macOS SystemTime fix, enhanced IDE observability with logging for the lets-plot-idea-plugin, and refreshed documentation and demos to reflect these changes. The work delivers stronger plotting correctness across regions, reduced time-zone related defects, and improved developer experience across the stack.

April 2025 monthly summary for JetBrains/lets-plot: Focused on delivering a demonstrable, robust plotting experience and improving maintainability of the core visualization utilities. Delivered a new demo notebook to showcase mathematical function visualization with Lets-Plot, while hardening the plotting stack to handle mixed data types and consolidating range calculation logic for easier future maintenance.

March 2025 delivered a cohesive set of stability and API-evolution improvements across the Lets-Plot ecosystem. Key outcomes include migration-friendly Maven artifact changes, binding to stable lets-plot releases, API compatibility signaling for PlotPanel, improved Python frontend error handling, and a consolidated fat JAR packaging/publishing workflow for the IDEA plugin, underpinning reliable releases and a smoother upgrade path for users.

February 2025: Delivered substantial rearchitecture and enhancements to JetBrains/lets-plot. Implemented SizingPolicy refactor across the plot rendering path, removed legacy PlotSizeUtil, extended HTML helper to support sizing policy, and added unit tests for Datalore-specific sizing to improve rendering correctness and reliability. Enhanced PlotHtmlHelper with forceImmediateRender and responsive options, and unified HTML generation logic to simplify maintenance and reduce edge-cases. Expanded test coverage and demos, including updates to SimpleTestSpecs, GeomLiveMapAwt demo, and GGBunch tests, plus a Python HTML generator utility to ease external HTML creation.

January 2025 (2025-01) delivered substantial API modernization and reliability improvements across the Lets-Plot plotting library, with a focus on business value and developer experience. Key work included GGBunch API evolution and integration (ggbunch() transformer, image_matrix via new API, regions/offset support, deprecation plan, updated tests/demos), composite figure sizing enhancements (refined sizing logic, default sizing moved to composite layout, new 'free' layout, initial ggbunch() with docstring), and broad codebase hygiene (FigureModelAdapter removal, access modifiers tightened, demos simplified). Kotlin/plot API modernization included removing deprecated gggrid() in lets-plot-kotlin, upgrade to kotlinx.coroutines v1.9.0, and Gradle/doc improvements. Titles support for gggrid/ggbunch was added, with refactoring to title-related code. Batch hygiene also covered updates to future_changes.md and copyright notices, plus updated ggbunch demos and sample data. Major bugs fixed targeted stability and UX: broken plot_background on gggrid, Swing root JPanel sizing, browser demo issues, and Interact error handling for missing spec_id. A performance improvement was achieved by moving datalore pref width processing earlier in the pipeline. Overall, these changes reduce upgrade risk, improve rendering stability, and enable richer figure composition for end users.

December 2024 monthly summary focused on documentation governance, bug fixes, and maintenance upgrades across three repositories: JetBrains/lets-plot, JetBrains/lets-plot-kotlin, and Kotlin/kotlin-jupyter-libraries. The work delivered clearer, versioned docs for number formatting and exponent_format, stabilized formatting behavior across tooltips/axes/legend, and aligned Kotlin projects with upstream Lets-Plot fixes. This reduced onboarding ambiguity for users, lowered support costs, and improved build reliability across Kotlin integrations.

Concise monthly summary for 2024-11 highlighting key features delivered, major bugs fixed, overall impact, and technologies demonstrated across three repositories: JetBrains/lets-plot-kotlin, Kotlin/kotlin-jupyter-libraries, and JetBrains/lets-plot.

October 2024: Delivered cross-repo product improvements and reliability fixes across JetBrains/lets-plot and JetBrains/lets-plot-kotlin. Key business-value outcomes include clearer documentation and deprecation guidance, a UI/UX overhaul that reduces user friction in toolbar and notebook layouts, and robust plotting features that prevent crashes during wheel zoom and log transforms. Demo notebooks and examples were refreshed to reflect latest library versions, enabling smoother onboarding and showcasing capabilities. An environment upgrade to Python 3.9 ensured compatibility with newer features. Kotlin-specific enhancements introduced an interactive pan/zoom toolbar (ggtb) and an expandLimits() demo, along with improved legend visualizations and structured release notes for upcoming 4.9.0, strengthening release readiness and cross-language consistency.