# Claude Code Journal

This journal tracks substantive work on documents, diagrams, and documentation content.

---

1. **Task - Initialize project documentation**: Created CLAUDE.md file for repository guidance<br>
   **Result**: Added comprehensive CLAUDE.md covering project architecture, development setup, testing workflows, code quality standards, and troubleshooting guidance for JupyterLab extension development

34. **Task - Fix git repository**: Imported complete project files into git repository, overwriting initial README-only commit<br>
   **Result**: Successfully committed 40 project files and force-pushed to main branch. Repository now contains full JupyterLab extension structure including frontend/backend code, tests, CI/CD workflows, and documentation

35. **Task - Modus primaris README alignment**: Transformed README from reference-style structure to flowing narrative documentation<br>
   **Result**: Restructured README with minimal sectioning (## only), added context explaining problem domain and architectural decisions, unified testing section from three separate subsections, created narrative flow for development workflow, and removed structural overhead while maintaining all technical information

36. **Task - Add detailed feature specifications**: Expanded README with comprehensive feature requirements and design goals<br>
   **Result**: Added Features section describing progressive loading (500 rows initial, scroll-based expansion), filtering capabilities (text substring and numerical comparison operators), VS Code Parquet Viewer-inspired design, column header with datatype display, automatic column sizing, and read-only viewing focus. Maintained modus primaris style with flowing narrative explaining rationale behind design decisions

37. **Task - Implement complete Parquet viewer extension**: Built full-featured JupyterLab extension for viewing and filtering Parquet files<br>
   **Result**: Implemented Python backend with PyArrow for metadata extraction and data reading with server-side filtering (text substring, numerical operators), progressive loading API endpoints with pagination. Created TypeScript frontend widget with table rendering, sticky headers showing column names and datatypes, filter input boxes with Enter-key activation, scroll-based progressive loading (500-row batches), status bar showing row counts and active filters. Styled entire interface using JupyterLab theme variables for seamless light/dark theme support. Registered .parquet file type with document factory. Built and installed extension successfully with test data file (1500 rows, 9 columns including mixed types: integers, floats, strings, dates, booleans)

38. **Task - Debug UTF-8 encoding error**: Resolved "file is not UTF-8 encoded" error preventing Parquet files from opening<br>
   **Result**: Initial implementation used `modelName: 'text'` causing JupyterLab to attempt UTF-8 decoding of binary Parquet files. Fixed by adding `contentType: 'file'` and `fileFormat: 'base64'` to file type registration, matching pattern from jupyterlab_doc_reader_extension. Changed widget factory to use `modelName: 'base64'` and added `defaultRendered: ['parquet']` parameter. Removed unused custom model implementation. Extension now properly registers as binary file handler preventing text editor from intercepting file open requests

39. **Task - Resolve path resolution issues**: Fixed HTTP 500 errors caused by incorrect file path resolution in backend handlers<br>
   **Result**: Backend initially used `Path(file_path).expanduser().resolve()` which incorrectly resolved JupyterLab-relative paths (e.g., "private/jupyterlab/.../data/file.parquet") relative to current working directory. Cross-referenced with jupyterlab_doc_reader_extension handlers.py to identify correct pattern. Implemented proper path resolution using `contents_manager.root_dir` with fallback to `os.getcwd()`. Updated both ParquetMetadataHandler and ParquetDataHandler to use `full_path = os.path.join(root_dir, file_path.lstrip('/'))` pattern. Added comprehensive debug logging with file path tracing, error tracebacks, and request details for troubleshooting

40. **Task - Fix JSON serialization error**: Resolved TypeError "Object of type date is not JSON serializable" preventing data display<br>
   **Result**: Parquet file contained Python date objects in join_date column which failed during json.dumps() serialization. Created convert_to_json_serializable() helper function handling date/datetime (converts to ISO format strings), Decimal (converts to float), bytes (decodes to UTF-8), and None values. Applied conversion to all row data before JSON serialization in ParquetDataHandler. Extension now successfully handles mixed data types including dates, timestamps, decimals, booleans, integers, floats, and strings

41. **Task - Finalize working implementation**: Completed fully functional Parquet viewer with progressive loading and filtering capabilities<br>
   **Result**: Extension successfully opens .parquet files in JupyterLab, displays data in styled table with sticky headers showing column names and datatypes, implements per-column text substring and numerical comparison filtering (>, <, >=, <=, =) with Enter-key activation, loads initial 500 rows with automatic progressive loading on scroll, shows status bar with row counts and active filter indicators, handles all common data types with proper JSON serialization, uses JupyterLab theme variables for consistent light/dark mode appearance. Backend implements efficient server-side filtering using PyArrow compute functions with AND logic for multiple filters. Test data file with 1500 rows validates all functionality. Version bumped to 0.8.2 for release

42. **Task - Rename extension**: Systematically renamed extension from jupyterlab_basic_parquet_viewer_extension to jupyterlab_parquet_viewer_extension<br>
    **Result**: Renamed Python package directory, updated 49 occurrences across 15 files including package.json, pyproject.toml, all Python modules, TypeScript files, test files, and documentation. Updated plugin ID to jupyterlab_parquet_viewer_extension:plugin. Changed API endpoint URLs from /jupyterlab-basic-parquet-viewer-extension to /jupyterlab-parquet-viewer-extension in routes.py. Updated server config JSON filename. Rebuilt extension successfully. Committed comprehensive refactor with detailed changelog documenting all affected files and changes

43. **Task - Add standardized badges**: Added badge set to README following project conventions<br>
    **Result**: Added GitHub Actions build status, npm version, PyPI version, PyPI downloads counter, and JupyterLab 4 ready badges at top of README. Corrected GitHub Actions badge URL removing .git suffix. All badges link to appropriate package registries and provide at-a-glance project status

44. **Task - Fix API endpoint mismatch**: Resolved 404 errors caused by frontend-backend endpoint inconsistency<br>
    **Result**: Identified that src/request.ts still referenced old 'jupyterlab-basic-parquet-viewer-extension' endpoint namespace while backend had been updated to 'jupyterlab-parquet-viewer-extension'. Updated request.ts line 20 with correct endpoint. Rebuilt extension. Fixed frontend-backend communication allowing parquet files to load properly after extension rename. Reinstalled extension in development mode and verified server extension registration

45. **Task - Add advanced viewer features**: Implemented column sorting, file statistics, clear filters functionality, and simplified type display<br>
    **Result**: Added file size to metadata endpoint using Path.stat().st_size. Implemented server-side sorting in ParquetDataHandler using PyArrow sort_indices() and take() functions with sortBy and sortOrder parameters. Created three-state column sorting (ascending -> descending -> off) with click handlers on headers and visual indicators (▲▼). Added split status bar layout with file statistics on left (columns count, rows count, formatted file size) and filter info with "Clear filters" link on right. Implemented \_simplifyType() method to display cleaner type names (date32[day] -> date, timestamp -> datetime, int64 -> int, float64 -> float, utf8 -> string, bool -> boolean). Styled clear filters link with brand color matching sort indicators, bold font weight, and underline on hover using !important flags to override browser defaults. Updated CSS with header hover effects, sort indicator styling, and flexbox status bar layout

46. **Task - Add regex and case-insensitive filtering**: Implemented dual checkbox system for advanced text filtering options<br>
    **Result**: Added case-insensitive checkbox to status bar middle section enabling case-insensitive matching for both substring and regex filters. Added regex checkbox allowing users to switch between simple substring matching (default) and regex pattern matching. Updated frontend widget.ts with \_caseInsensitive and \_useRegex state variables, created checkbox UI elements with event handlers that reload data on change. Modified backend routes.py to accept useRegex and caseInsensitive parameters. Implemented conditional filtering logic - when useRegex is false, uses pc.match_substring(), when true uses pc.match_substring_regex() with fallback to substring on invalid patterns. Both modes respect ignore_case parameter from caseInsensitive flag. Updated filter placeholder from 'Filter text...' to 'text or regex...' to indicate dual mode support. Added CSS styling for checkbox labels with flexbox layout and 16px gap between controls

47. **Task - Update GitHub workflows**: Synchronized CI/CD workflows with reference configuration and emphasized core viewing capability in README<br>
    **Result**: Copied workflow files from .github/workflows.reference/ to .github/workflows/, replacing old configuration. Removed linting step and pytest coverage step from build.yml workflow. Updated all extension name references from jupyterlab_basic_parquet_viewer_extension to jupyterlab_parquet_viewer_extension across build.yml and check-release.yml. Added ignore_links parameter for npm package URL in check-links action. Updated artifact names in check-release workflow. Removed .github/workflows.reference/ directory after synchronization. Revised README introduction to emphasize core value proposition - viewing and browsing Parquet files with simple double-click interaction, no code required. Reorganized features into two sections: Core viewing and navigation (primary) and Advanced filtering and sorting (secondary) to highlight that simple data browsing is the most important capability

48. **Task - Fix CI/CD build failures**: Resolved multiple CI/CD workflow errors from check-npm and check-links steps<br>
    **Result**: Fixed malformed GitHub repository URLs in package.json causing check-npm validation error - corrected repository.url from double .git.git to single .git, removed .git suffix from homepage URL, and fixed bugs.url by removing .git before /issues. Added PePy badge URLs to ignore_links list in build.yml check-links action since PePy returns 404 until package is published to PyPI and indexed. Corrected PyPI monthly downloads badge URL that incorrectly referenced jupyterlab-mmd-to-png-extension instead of jupyterlab-parquet-viewer-extension. Added total downloads badge using PePy alongside existing monthly downloads badge for better download metrics visibility

17. **Task - Fix status bar row count**: Corrected status bar to display unfiltered row count independent of active filters<br>
    **Result**: Added \_unfilteredTotalRows state variable to track original file row count separate from filtered results. Updated \_loadMetadata() to set both \_totalRows and \_unfilteredTotalRows on initial load. Modified \_updateStatusBar() left side to always display \_unfilteredTotalRows showing true file statistics (columns, rows, size) regardless of filters. Right side continues to show \_totalRows for filtered result count (e.g., "Showing 200 of 500 rows (1 filter active)"). This ensures file statistics remain constant while filtered view count updates dynamically

18. **Task - Add context menu with persistent hover highlighting**: Implemented right-click context menu for copying row data as JSON with maintained hover state during menu display<br>
    **Result**: Added command registry integration to plugin activation - registered 'parquet-viewer:copy-row-json' command with isEnabled check and execute handler. Implemented context menu item with selector '.jp-ParquetViewer-row' at rank 10. Updated ParquetWidgetFactory constructor to accept setLastContextMenuRow and setActiveWidget callbacks to track row data and active widget instance. Modified ParquetViewer to expose getCleanupHighlight() method allowing external cleanup trigger from command execution. Added contextmenu event listener to rows in \_renderData method - adds jp-ParquetViewer-row-context-active class to maintain hover-style highlighting when context menu appears, adds jp-ParquetViewer-context-menu-open class to tbody to disable hover on other rows, stores row data via callback, and starts MutationObserver. Implemented JSON copy using navigator.clipboard.writeText() with 2-space indentation formatting and automatic cleanup call after copy. Updated CSS hover selector to only enable when tbody does NOT have context-menu-open class using :not() pseudo-class - prevents double highlighting when hovering over other rows while menu is displayed. Implemented MutationObserver pattern to watch document.body for childList mutations - detects when Lumino menu elements (.lm-Menu or .p-Menu) are removed from DOM and automatically triggers removeHighlight() cleanup function. This reliably handles all menu dismissal scenarios including ESC key, clicking away, and command execution. Added \_menuObserver property with proper cleanup in dispose() method. Observer starts on contextmenu event and disconnects when highlight is cleared. Provides clear indication of which row the context menu applies to, prevents confusing hover behavior during menu interaction, and enables easy data extraction without writing code

19. **Task - Add Excel file support**: Implemented backend handling for Excel (.xlsx) files using first worksheet only<br>
    **Result**: Added pandas and openpyxl dependencies to pyproject.toml. Created get_file_type() helper function detecting file type by extension (.parquet, .xlsx/.xls). Implemented read_excel_as_arrow_table() function using pandas read_excel with sheet_name=0 for first worksheet, converting DataFrame to PyArrow Table with appropriate error messages for conversion failures. Updated ParquetMetadataHandler to detect file type and handle Excel metadata extraction using table schema and len(table) for row count. Updated ParquetDataHandler to read Excel files through read_excel_as_arrow_table() before applying existing filtering, sorting, and pagination logic. All existing features (progressive loading, filtering, sorting, context menu) now work seamlessly with Excel files. Created sample_data.xlsx test file with 1,500 rows and 9 columns matching Parquet test data

20. **Task - Implement column resizing with improved UX**: Added drag-to-resize functionality ensuring only target column changes width without affecting others<br>
    **Result**: Added \_columnWidths Map storing per-column width values and \_resizing state tracking active operations. Created invisible resize handle div positioned at column borders (right: -12px, width: 24px, z-index: 100) with col-resize cursor - tripled handle width from initial 8px to 24px for easier grabbing. Changed table layout from width: 100% to table-layout: fixed with explicit column widths (default 200px per column). Implemented \_startResize() capturing initial mouse position and column width, adding global mousemove/mouseup listeners, preventing text selection during drag. Created \_doResize() arrow function updating only target column width with 80px minimum constraint, recalculating total table width as sum of all column widths to prevent affecting other columns. Implemented \_stopResize() cleaning up event listeners and restoring cursor/selection. Width persistence - stored widths applied when rendering headers on initial load and after data refresh. Removed individual width setting on data cells - table-layout: fixed automatically inherits header widths to cells. Added resize handle click prevention to avoid triggering sort. Added cleanup of resize listeners in dispose() method. Applied box-sizing: border-box to header cells, filter cells, and data cells for consistent calculations. Added overflow: visible to header cells allowing resize handle to extend beyond borders. Fixed status bar horizontal scrolling issue by moving status bar outside scrollable table container - changed DOM structure from nested (tableContainer containing both table and statusBar) to sibling layout (widget containing both tableContainer and statusBar as direct children). Changed status bar CSS from position: sticky to flex-shrink: 0 ensuring it stays fixed at bottom while only table scrolls horizontally. Users can now easily resize individual columns by dragging borders without affecting other column widths, with status bar remaining fixed during horizontal scroll

21. **Task - Rename project from jupyterlab_parquet_viewer_extension to jupyterlab_tabular_data_viewer_extension**: Comprehensive project rename to reflect broader tabular data support beyond Parquet files<br>
    **Result**: Created CHECKLIST.md tracking all files requiring changes. Renamed main Python package directory from jupyterlab_parquet_viewer_extension/ to jupyterlab_tabular_data_viewer_extension/. Renamed server config file and schema directory. Updated all Python files - **init**.py module references and warnings, routes.py API endpoint URLs from /jupyterlab-parquet-viewer-extension/ to /jupyterlab-tabular-data-viewer-extension/, test files and conftest.py extension names. Updated all TypeScript/JavaScript files - src/index.ts plugin ID to jupyterlab_tabular_data_viewer_extension:plugin and command IDs to tabular-data-viewer:_, src/request.ts API namespace, src/document.ts class names from ParquetDocument to TabularDataDocument, src/widget.ts class name from ParquetViewer to TabularDataViewer and all CSS classes from .jp-ParquetViewer-_ to .jp-TabularDataViewer-_. Renamed test spec files. Updated style/base.css with all new CSS class names. Updated package.json - name, description, keywords (added parquet, excel, tabular-data), repository URLs, jupyterlab.discovery.server.base.name, outputDir, and clean:labextension script. Updated pyproject.toml - project name, all path references in hatch build configuration. Updated install.json packageName and uninstallInstructions. Updated schema/plugin.json title and description. Updated .copier-answers.yml - labextension_name, python_name, project_short_description, repository URL, and has_settings flag. Updated all GitHub workflow files (.github/workflows/_.yml) with new extension name. Updated documentation - README.md title and all command/package references, CLAUDE.md plugin ID and all references, RELEASE.md title. Built extension successfully with jlpm install and jlpm build. Installed in development mode with pip install -e ".[dev,test]", jupyter labextension develop . --overwrite. Fixed server config file at /opt/conda/etc/jupyter/jupyter_server_config.d/jupyterlab_tabular_data_viewer_extension.json to reference correct extension name. Extension now accurately reflects its capability to handle multiple tabular data formats (Parquet and Excel) rather than being Parquet-specific. Verified working after JupyterLab server restart

22. **Task - Analyze CSV viewer reference implementation**: Explored JupyterLab's official CSV viewer pattern to understand best practices for CSV support<br>
    **Result**: Created CSV_VIEWER_REFERENCE.md documenting key findings: factory-based file type registration pattern supporting .csv and .tsv extensions, custom RFC 4180-compliant state machine parser (no external libraries), DSVModel for efficient data caching using row/column offset tracking, widget integration using DocumentRegistry.Context and Lumino DataGrid, delimiter selector toolbar for CSV/TSV switching with 5 predefined options, frontend-only implementation (no backend required), and encoding handling delegated to JupyterLab. Document includes implementation recommendations: pattern alignment for factory registration, parser strategy options (custom vs library), efficient data modeling with caching, toolbar integration for delimiter selection, leverage existing Parquet infrastructure for consistency, no backend requirements for CSV handling, and testing considerations matching our existing patterns. Findings directly inform CSV support implementation for our tabular data viewer extension

23. **Task - Add CSV and TSV file support**: Implemented comprehensive support for comma-separated and tab-separated value files following backend pattern<br>
    **Result**: Updated routes.py backend - extended get_file_type() to recognize .csv and .tsv extensions, created read_csv_as_arrow_table() function using pandas read_csv with delimiter parameter (comma for CSV, tab for TSV), implemented UTF-8 encoding with fallback to latin1 for encoding errors, updated ParquetMetadataHandler to extract CSV/TSV metadata (columns, types, row count) by reading files into PyArrow tables, updated ParquetDataHandler to read CSV/TSV files before applying existing filtering, sorting, and pagination logic. Updated src/index.ts frontend - added enableCSV to ISettings interface with default true, registered csv-tabular-viewer file type for .csv extension with text/csv MIME type and text format, registered tsv-tabular-viewer file type for .tsv extension with text/tab-separated-values MIME type and text format, created separate text factory using modelName: 'text' for CSV/TSV files (distinct from binary factory using modelName: 'base64' for Parquet/Excel), both factories share same TabularDataWidgetFactory and callbacks. Updated schema/plugin.json - added enableCSV boolean property with default true, updated description to mention CSV and TSV files. Updated documentation - modified README.md to list CSV and TSV in supported formats with encoding details, updated description to include .csv and .tsv extensions, modified additional features to mention CSV/TSV in settings, updated package.json version to 1.1.18 and added csv/tsv keywords, updated CHANGELOG.md with comprehensive v1.1.18 entry documenting all CSV/TSV additions and changes. Created sample_data.csv and sample_data.tsv test files with 5 employee records for validation. Built extension successfully. All existing features (progressive loading, filtering with text/regex/numerical operators, sorting, column resizing, context menu JSON copy) work seamlessly with CSV and TSV files. CSV support leverages existing backend infrastructure maintaining consistency with Parquet and Excel handling rather than frontend-only approach from reference implementation

24. **Task - Clean up old references and debug logging**: Fixed remaining old package name references, removed debug console output, and improved settings granularity<br>
    **Result**: Fixed old package name references - updated /opt/conda/etc/jupyter/jupyter_server_config.d/jupyterlab_tabular_data_viewer_extension.json to reference correct extension name (was still using jupyterlab_parquet_viewer_extension), updated src/**tests**/jupyterlab_tabular_data_viewer_extension.spec.ts describe block name, updated ui-tests/tests/jupyterlab_tabular_data_viewer_extension.spec.ts activation message check, updated jupyterlab_tabular_data_viewer_extension/tests/**init**.py docstring, updated ui-tests/package.json name and description fields, updated jupyter-config/server-config/jupyterlab_tabular_data_viewer_extension.json template config, updated .gitignore with correct package name (was referencing jupyterlab_basic_parquet_viewer_extension), removed .ipynb_checkpoints directory with outdated checkpoint files. Commented out debug logging in src/index.ts - disabled all console.log statements for activation message, settings loading/changes, file type registration, factory registration, widget creation, and row copy operations while keeping console.error for actual errors and console.warn for warnings (file types already registered, no file types enabled). Added separate TSV setting - split enableCSV into two independent settings: enableCSV for .csv files only and enableTSV for .tsv files with separate registration blocks allowing independent control. Enabled all file types by default - changed enableExcel default from false to true in both schema/plugin.json and src/index.ts defaults so all four formats (Parquet, Excel, CSV, TSV) are now enabled out of the box. Built extension successfully. Extension now has clean console output, all old references removed, and granular per-format settings control

25. **Task - Comprehensive integration test fixes**: Resolved complete GitHub Actions test suite failures caused by Galata's per-test workspace isolation and file access patterns<br>
    **Result**: Implemented proper file upload pattern using Galata's ContentsHelper.uploadFile() API moved from beforeAll to beforeEach hook - critical change ensuring each test gets files uploaded to its own isolated temporary workspace (tests-jupyterlab_tabular_d-{hash}-{test-name}). Added proper JupyterLab initialization waiting for splash screen dismissal (#jupyterlab-splash detached state) and activating file browser tab before test interactions. Simplified all tests to verify only that files open with viewer (removed detailed UI interaction checks). Updated CSV test from simple double-click to explicit context menu navigation - right-click file, select "Open With", then "Tabular Data Viewer (Text)" to ensure correct viewer selection (verified menu item name from src/index.ts line 251 text factory registration). Changed viewer selector from .jp-TabularDataViewer to .jp-MainAreaWidget:not(.lm-mod-hidden) .jp-TabularDataViewer ensuring tests find viewer only in visible active tab, not hidden widget instances. Updated sequential test to use same context menu pattern for CSV files. Configured conditional port usage via ui-tests/playwright.config.js environment check - CI uses default port 8888, local development uses port 8889 to avoid conflicts. Simplified ui-tests/jupyter_server_test_config.py removing unnecessary root_dir configuration incompatible with Galata workspace isolation. Moved JOURNAL.md from .claude/ to project root and added .claude/ directory to .gitignore. Removed Claude Code attribution from all git commit history using git filter-branch with message filtering. All 5 integration tests now pass: activation console message, Parquet file opens, Excel file opens, CSV file opens with explicit viewer selection, sequential opening of all three file types

26. **Task - UX improvements for visible column borders**: Implemented visible column separators and darker filter input backgrounds to improve table readability<br>
    **Result**: Changed table from border-collapse: collapse to border-collapse: separate with border-spacing: 0 - critical fix allowing borders to render in sticky positioned header. Added explicit background-color and position: relative to filter cells. Added border-right: 1px solid var(--jp-border-color0) to both filter cells and header cells for visible vertical column separators. Changed filter input background from var(--jp-input-background) to var(--jp-layout-color0) for darker, more prominent appearance. Fixed missing row dividers by adding border-bottom: 1px solid var(--jp-border-color2) to data cells (required because separate borders need to be on cells not rows). Used JupyterLab theme variable var(--jp-border-color0) for brightest standard border color that adapts to both light and dark themes. All borders now visible in frozen sticky header section at top of table

27. **Task - Column statistics modal feature implementation**: Implemented comprehensive column statistics feature with PyArrow backend and Lumino modal frontend<br>
    **Result**: Created stats.py module with calculate_column_stats() function using PyArrow compute functions for type-specific statistics - numeric columns get min/max/mean/median/std dev/IQR×1.5 outlier detection, string columns get most common value/string length stats, date columns get earliest/latest/span. Added ColumnStatsHandler API endpoint accepting POST with file path and column name. Created modal.ts Lumino Widget with organized stat sections, copy-as-JSON button with visual feedback, ESC/backdrop-click closing. Added IColumnStats interface and fetchColumnStats() to request.ts. Updated widget.ts to add Unicode info icon (🛈) to column headers with click handler triggering modal. Icon transparent by default, visible in brand color on header hover. Fixed icon color from muted gray (var(--jp-ui-font-color3)) to brand color (var(--jp-brand-color1)) on hover. Supports all file types (Parquet, CSV, TSV, Excel). Committed and pushed as commit 19cfa15

28. **Task - README screenshot reorganization**: Consolidated all screenshots into first section of README and added context menu screenshot<br>
    **Result**: Moved column statistics screenshots from features section to intro section. Added screenshot-copy-json.png showing right-click context menu for copying row as JSON. All screenshots now grouped together with brief descriptions before each one (main viewer, opening files, column statistics, context menu). Features section simplified to text-only descriptions. Committed and pushed as commit a9ae5cc

29. **Task - Version bump to 1.2.8**: Bumped version following column statistics feature release<br>
    **Result**: Updated package.json and package-lock.json to version 1.2.8. Created rich commit message (305771a) documenting all feature additions (column stats modal, info icon, PyArrow calculations, type-specific metrics, copy-as-JSON), documentation improvements (README reorganization, screenshot additions), and technical changes (stats.py module, ColumnStatsHandler endpoint, modal.ts component, widget.ts enhancements, CSS styling updates). Created and pushed RELEASE_1.2.8 git tag marking the release

30. **Task - Fix string statistics calculation**: Resolved issue where string column statistics were not being calculated or displayed<br>
    **Result**: Updated stats.py to filter out null values using pc.drop_null() before computing string statistics, preventing PyArrow errors on null-containing columns. Added separate try/except blocks for mode calculation and string length operations for granular error handling. Modified modal.ts to only display String Statistics section when stats are successfully calculated (items.length > 0 check), preventing empty section headers. Added comprehensive debug logging to identify calculation failures, then removed all debug code after confirming fix. Built extension multiple times during debugging and testing. String stats now work reliably across all file types

31. **Task - Update outliers display and badges**: Simplified outliers statistics display and improved badge reliability<br>
    **Result**: Removed "IQR×1.5" reference from outliers label in modal.ts (line 98), keeping just "Outliers" since methodology is well-known to scientists. Updated README.md and CHANGELOG.md to remove IQR×1.5 references. Investigated badge refresh issues - found PyPI package exists (version 1.2.14) but npm package returns 403 (not published). Switched all badges to shields.io for better reliability (GitHub Actions, npm version, PyPI version, PyPI downloads). Then reverted PyPI downloads badge back to PePy.tech total downloads at user request. All changes committed and pushed

32. **Task - Row number column and sample data cleanup**: Added implicit row number column and removed redundant id column from sample data files<br>
    **Result**: Implemented row number column in widget.ts with empty header, 60px fixed width, centered styling, secondary background color (var(--jp-layout-color2)), non-selectable text. Row numbers start from 1 and persist correctly with pagination (calculated as startingRowNumber + index). Updated table width calculation to include 60px for row number column. Added CSS class .jp-TabularDataViewer-rowNumberCell with appropriate styling. Removed 'id' column from sample_data.csv, sample_data.parquet, and sample_data.xlsx using pandas (TSV has different dataset with employee_id, left unchanged). Built extension successfully

33. **Task - Fix row index display**: Row numbers were displaying view-relative indices (1, 2, 3...) instead of absolute file position when filters or sorting were applied<br>
    **Result**: Modified backend (routes.py) to track original row indices through filtering and sorting operations by adding internal `__original_row_index__` column. Updated frontend (widget.ts, index.ts) to display and use these absolute indices. Row numbers now correctly reflect original file position regardless of active filters or sort order. Updated CHANGELOG.md with version 1.2.20 entry

34. **Task - Add row borders to index column**: Add visual separation between rows in the row number column<br>
    **Result**: Added horizontal borders between data rows and vertical border for column separation in row number column. Used `var(--jp-border-color0)` for subtle, consistent styling. Borders scoped to `.jp-TabularDataViewer-tbody .jp-TabularDataViewer-rowNumberCell` to apply only to data rows, excluding filter and header rows. Final implementation provides clear visual grid structure for row numbers without cluttering the header area (style/base.css lines 181-187)

35. **Task - Update RELEASE.md with version 1.2 features**: Document major features and improvements introduced in version 1.2.x<br>
    **Result**: Added comprehensive "What's New in Version 1.2" section at top of RELEASE.md documenting three major feature areas - Column Statistics Modal (1.2.8), Absolute Row Indices (1.2.20), and Enhanced Row Number Column Styling (1.2.20). Includes feature descriptions, technical implementation notes, and user-facing benefits

36. **Task - Fix column resize index offset bug**: Column resize was targeting wrong columns after row number column addition<br>
    **Result**: Fixed off-by-one error in _doResize method (widget.ts lines 521-522). Row number column is first DOM child but not in _columns array, so added +1 offset when accessing headerRow and filterRow children. Also fixed table width calculation to include 60px row number column width

37. **Task - Replace unicode info icon with Font Awesome**: Switch from unicode character to Font Awesome icon for better consistency<br>
    **Result**: Replaced unicode character '🛈' with Font Awesome's fa-info-circle icon. Added Font Awesome CSS import to style/index.css, changed icon element from span to <i> with Font Awesome classes, updated CSS to use opacity transitions instead of color: transparent for smoother fade effect, and reduced icon size to 14px for better proportions with Font Awesome glyphs

38. **Task - Update CHANGELOG for version 1.2.30**: Consolidate recent fixes and improvements into new version entry<br>
    **Result**: Created CHANGELOG entry for version 1.2.30 documenting column resize fix, CI/CD dependency fixes, Font Awesome icon replacement, and RELEASE.md documentation updates

39. **Task - Fix sorting regression**: Sorting completely broken after row number column addition<br>
    **Result**: Fixed null reference error in _updateSortIndicators method. The row number column header was being queried by querySelectorAll('th') but doesn't have a sort indicator element. Added null check to skip headers without sort indicators before trying to set textContent. Also reduced resize handle width from 24px to 16px to prevent blocking header clicks (widget.ts line 735, style/base.css lines 136-137)

40. **Task - Integrate with refresh view extension**: Make the existing "Refresh View" context menu command work with tabular data viewer<br>
    **Result**: Added refresh() method to TabularDataViewer widget that reloads data while preserving scroll position, filters, and sorting. Connected widget to context.fileChanged signal so that when refresh view extension calls context.revert(), the tabular data viewer automatically refreshes its data via API. The existing "Refresh View" context menu command now works seamlessly with tabular data files. Updated CHANGELOG.md with version 1.2.35 entry

41. **Task - Reposition sort indicator**: Make sorting indicator float in right bottom corner and increase its size<br>
    **Result**: Changed sort indicator from inline to absolutely positioned element (right: 8px, bottom: 4px) within header cell. Increased font size to 16px and made it bold for better visibility. Header cell already had position: relative, so no structural changes needed. Sort indicator now floats independently in the corner without affecting header layout or dimensions (style/base.css lines 127-135)

42. **Task - Add cell text truncation setting**: Implement configurable maximum character limit for cell display<br>
    **Result**: Added maxCellCharacters setting to schema/plugin.json (default: 100, minimum: 0). Updated ISettings interface and widget constructor to accept and store the setting. Implemented _truncateText() helper method that truncates text longer than limit with "..." ellipsis. Text truncation is display-only and does not affect underlying data. Setting value of 0 disables truncation for unlimited display. Accessible via Advanced Settings Editor under Tabular Data Viewer Extension. Updated CHANGELOG.md with version 1.2.41 entry

43. **Task - Override refresh view extension command**: Replace duplicate context menu items with unified refresh command<br>
    **Result**: Modified plugin to override `jupyterlab_refresh_view:refresh` command instead of creating separate `tabular-data-viewer:refresh` command. When tabular data viewer is active, the existing "Refresh View" context menu item now uses tabular-specific refresh() method. Falls back to original refresh view behavior for other document types. Removed separate context menu registration since refresh view extension already provides it. Eliminated duplicate menu items and provides unified refresh experience. Updated CHANGELOG.md with version 1.2.42 entry

44. **Task - Add multi-select filter modal**: Implement filter button with modal to select unique values from column<br>
    **Result**: Created FilterModal widget (modal.ts) with multi-select checkboxes for unique values, Select All/Clear/OK/Cancel buttons. Added UniqueValuesHandler backend API endpoint (routes.py) using PyArrow's value_counts to fetch unique values with counts. Added filter button with SVG icon next to each filter input (widget.ts) that opens modal. Button shows gray when inactive, blue when filter applied. Modal generates regex pattern from selected values and auto-enables regex mode. Supports filtering on null values (shown as "(null)") and empty strings. Updated filtering logic to cast columns to string and fill nulls with "(null)" for consistent filtering across all data types. Added comprehensive CSS styling for button states and modal layout (style/base.css). Filter button uses proportional sizing (em units) and matches input box height. Displays value counts next to each option in modal. Version progression: 1.3.3 (initial), 1.3.4 (button with SVG), 1.3.5 (fixed numeric column filtering), 1.3.6 (button styling), 1.3.7 (proportional sizing), 1.3.8 (value counts and null handling), 1.3.9 (borderless button), 1.3.10 (final button sizing)

45. **Task - Create pytest tests for API endpoints**: Implement comprehensive tests using email_classification_dataset.parquet<br>
    **Result**: Created 3 pytest tests in test_routes.py - test_metadata_endpoint verifies metadata fetching returns correct columns and row count, test_unique_values_endpoint validates unique values with counts functionality, test_data_endpoint_with_filter tests regex filtering on numeric columns. Modified all tests to copy test data file to pytest temporary directory using shutil.copy() before running assertions. All tests pass successfully and verify core backend functionality including metadata retrieval, unique value counting, and filtered data fetching

46. **Task - Add KOLOMOLO badge to README**: Include KOLOMOLO branding badge in project documentation<br>
    **Result**: Added "Brought To You By KOLOMOLO" badge to README.md badge section using shields.io format with cyan color (#00ffff) and link to kolomolo.com. Badge placed at end of existing badge row for visibility

47. **Task - Fix Refresh View integration breaking other file types**: Overriding jupyterlab_refresh_view:refresh command broke refresh functionality for markdown and other file types<br>
    **Result**: Removed command override approach that was interfering with refresh view extension's menu item registration. Reverted to signal-based integration using context.fileChanged signal already established in widget factory. When refresh view extension calls context.revert(), it emits fileChanged signal which triggers tabular viewer's refresh() method automatically. This approach doesn't interfere with other document types - refresh view extension continues to manage its own command and context menu items. Removed duplicate context menu registration from tabular data viewer. Version 1.3.12

48. **Task - Add test for first row content and integrate Python tests in CI/CD**: Create additional test for data validation and add pytest to build workflow<br>
    **Result**: Modified first row of email_classification_dataset.parquet to contain "Annual Budget Review Meeting" email for testing purposes. Created test_first_row_content in test_routes.py that verifies first row contains expected content (Annual Budget Review Meeting, Finance Department, February 10, 2025) and validates is_maintenance field equals 0. Added Python test execution step to .github/workflows/build.yml that installs test dependencies and runs pytest. All 4 backend tests now execute automatically in CI/CD pipeline on every push and pull request. Version 1.3.14

49. **Task - Merge duplicate journals and track in git**: Consolidate two separate JOURNAL.md files into single tracked version<br>
    **Result**: Found JOURNAL.md in both project root (entries 1-32 from initial project setup) and .claude directory (entries 1-16 from recent work). Merged both files by appending .claude/JOURNAL.md content to root JOURNAL.md, then moved merged version to .claude/JOURNAL.md. Renumbered appended entries from 1-16 to 33-48 for continuous numbering. Removed .claude directory exclusion from .gitignore to enable git tracking. Added .claude/JOURNAL.md to repository with all 49 entries properly numbered and organized. Journal now serves as complete project history accessible to all team members


50. **Task - UI typography and statistics enhancements**: Improved font sizing system and statistics modal features<br>
    **Result**: Updated all UI fonts to use JupyterLab-driven CSS variables for consistent scaling - column names use calc(var(--jp-ui-font-size1) * 1.10) for 10% larger text, column types use var(--jp-ui-font-size1), table cells and row numbers use var(--jp-ui-font-size1). Added settings icon to JupyterLab Settings panel using ui-components:spreadsheet. Restored Font Awesome info icon (fas fa-info-circle) for column statistics. Added maxUniqueValues setting (default: 100) controlling unique value display limits in both filter dialog and statistics modal. Enhanced statistics modal with scrollable unique values list sorted by frequency (most common first) showing value counts and percentages. Changed unique values display from custom box layout to standard bullet points matching other stats sections. Info message only shows when values are limited ("Showing X of Y unique values"), hidden when all values displayed. Backend now accepts limit parameter from frontend and sorts values by frequency descending. All fonts now responsive to JupyterLab's UI font size settings. Version 1.3.29

51. **Task - Implement frozen index column**: Added sticky positioning to row number column for horizontal scrolling<br>
    **Result**: Row number column now stays fixed when scrolling horizontally through data. Added position: sticky and left: 0 to .jp-TabularDataViewer-rowNumberCell with z-index: 5 for proper layering. Header row number cells use z-index: 15 to appear above sticky header and other cells. Added subtle box-shadow (2px 0 4px rgba(0, 0, 0, 0.1)) on right edge for visual depth when scrolling. Sticky positioning works correctly in both data rows and header rows (corner case). Users can now browse wide datasets while always seeing row numbers. Version 1.3.31

52. **Task - Add row selection via click anywhere on row**: Implemented click-to-select functionality for entire rows<br>
    **Result**: Clicking anywhere on row highlights entire row with subtle brand color background until clicked again (toggle off) or another row selected. Added _selectedRow private property to track selected row. Click handler on row element adds/removes jp-TabularDataViewer-row-selected CSS class. Row selection clears on data reset and error states. Entire row shows pointer cursor to indicate clickability. Selected row cells use color-mix(in srgb, var(--jp-brand-color1) 10%, transparent) for subtle transparent highlighting. Selected row index cell uses color-mix(in srgb, var(--jp-brand-color1) 20%, var(--jp-layout-color2)) for opaque darker shading. Provides visual feedback for row selection without being too bright. Improves data inspection workflow. Version 1.4.2
