[Unreleased]

[0.1.14] - 2026-10-10

Added

• Non-self-closing <sheet> and <xf> tag compatibility: Verify and support spreadsheet XML where <sheet>...</sheet> in workbook.xml or <xf>...</xf> in styles.xml are serialized with explicit closing tags rather than self-closing syntax.

• Namespace prefix resilience for relationship and embed attributes: Match relationship and embed attributes by local name or any namespace prefix (r:id, d3p1:id, rel:id, id, r:embed, embed) across WorkbookListener, HyperlinksListener, DrawingListener, and WorksheetParser, ensuring reliable sheet, hyperlink, and media resolution for non-standard XML generators.

• UTF-16LE, UTF-16BE, and UTF-8 BOM encoding normalization in ZipReader: Automatically detect and transcode Byte Order Mark (BOM) encoded XML streams (\xFF\xFE, \xFE\xFF, and \xEF\xBB\xBF) to UTF-8 in ZipReader#read_entry and EntryStreamIO, enabling seamless parsing of workbooks generated on Windows Phone and legacy platforms.

• XML 1.0 line ending normalization (\r\n and \r to \n): Normalize line breaks in shared strings, inline strings, and cell text values per W3C XML 1.0 §2.11 across SharedStringsParser and WorksheetParser.

• Whitespace and newline tolerance in cell regex scanning: Allow whitespace and newline sequences between <c> child tags (<f>, <v>, <is>) and strip whitespace on extracted values in WorksheetParser, ensuring reliable parsing of pretty-printed or formatted worksheet XML.

• Sequential row index fallback for omitted r attributes: Track previous row index and fall back to sequential 1-based indexing when <row> elements omit the r attribute per ECMA-376 Part 1 §18.3.1.73 across direct string scanning, chunked stream scanning, and event scanning in WorksheetParser.

• Case-insensitive part name lookup in ZipReader: Fall back to case-insensitive lookup for package part entries per ECMA-376 Part 2 §8.1.1, allowing workbooks with case-varying part names (such as lower-case xl/sharedstrings.xml or xl/styles.xml) to resolve transparently.

• Windows backslash path separator normalization in ZipReader: Normalize Windows backslash separators (\) in ZIP central directory and local headers to standard forward slashes (/), enabling transparent extraction and catalog lookup for XLSX archives generated on Windows.

• First-class sparkline groups on worksheet and add_sparkline helper: Expose sparkline_groups reader and keyword argument on Elements::Worksheet, propagate ws.sparkline_groups during Xlsxrb.write DOM serialization, and add add_sparkline(location:, range:, type:, **opts) helper to WorksheetBuilder, StreamWriter, and StreamWriter::SheetContext supporting :win_loss mapping to "stacked".

• High-level print area and print titles DSL: Add print_area, print_titles, repeat_rows, and repeat_columns to WorksheetBuilder, StreamWriter::SheetContext, and StreamWriter, expose print_area and print_titles on Elements::Worksheet, and auto-generate _xlnm.Print_Area and _xlnm.Print_Titles defined names in WorkbookBuilder#build and Xlsxrb.write DOM export.

• ECMA-376 indexed color palette and Xlsxrb::Colors: Add Xlsxrb::Colors providing INDEXED_COLORS (indices 0..63 per ECMA-376 Part 4 §18.8.27), palette_color, and to_hex utilities, expose Xlsxrb.palette_color and Xlsxrb.to_hex_color facade methods, and resolve integer palette indices 0..63 automatically in StyleBuilder.resolve_color.

• Flexible rich text run input in Xlsxrb.rich_text: Support [text, font_hash] pair arrays, alternating varargs of plain strings and format hashes or objects responding to to_font_hash, and mixed Elements::RichTextRun instances.

• First-class Elements::Hyperlink, Xlsxrb.hyperlink, and Cell#tooltip: Add Elements::Hyperlink data class and Xlsxrb.hyperlink factory helper with tooltip: support, expose Cell#tooltip and :tooltip, :url symbol key access on Elements::Cell, and support Elements::Hyperlink instances in WorksheetBuilder#hyperlink, StreamWriter#hyperlink, and Ooxml::Writer#hyperlink.

• Array and dynamic array formula serialization and Xlsxrb.array_formula: Add Xlsxrb.array_formula(expression, ref, cached_value:) factory method, extend Xlsxrb.formula with optional type: and ref: keywords, and serialize <f t="array" ref="..."> and shared formula attributes across all WorksheetWriter serialization paths.

• First-class style_index: keyword on Elements::Column: Add style_index: keyword argument directly to Elements::Column.new, storing it in Data.define attributes and populating it from rc[:style_index] during worksheet parsing and DSL column definitions.

• In-memory streaming write and row append chaining: Support Xlsxrb.write with omitted target in block mode to return an in-memory binary String, support self-returning << row appending for chaining across StreamWriter, SheetContext, and WorksheetBuilder, and add add_row aliases.

• Unified color and border style normalizers in StyleBuilder: Add StyleBuilder.normalize_color (supporting 140+ CSS named colors, #RGB, #RRGGBB, #AARRGGBB hex strings, numeric RGB integers, and optional alpha channel) and StyleBuilder.normalize_border_style (supporting border style symbols, aliases, strings, and 0..13 numeric border indices).

• Public date and time serial conversion utilities: Expose date_to_serial, serial_to_date, datetime_to_serial, and serial_to_time (aliased serial_to_datetime) on Xlsxrb and Xlsxrb::Utils for converting Ruby Date and Time instances to and from Excel 1900 and 1904 serial numbers.

• Cascade style inheritance and column styles: Support cascade style inheritance (Cell Style > Row Style > Column Style) in WorksheetWriter, and add style: parameter to StreamWriter#column and WorksheetBuilder#column.

• Embedded drawing and image extraction: Add Elements::Image representing anchored embedded images, expose images, images_at, and with_images across StreamSheet and Elements::Worksheet, and expose images and images_at across Elements::Workbook.

• Configurable sparse vs padded row and cell iteration: Add pad_empty_rows and pad_empty_cells options to Xlsxrb.read, Xlsxrb.build_worksheet, StreamSheet, WorksheetParser.each_row, and Elements::Worksheet to pad skipped rows or missing cells up to the maximum column, and add StreamRow#to_h and Elements::Row#cells_hash for coordinate-keyed row maps.

• Row XML metadata accessors and serialization: Expose row XML metadata (collapsed, collapsed?, hidden?, custom_height?, attributes) on StreamRow and Elements::Row, support collapsed: in StreamWriter#row and WorksheetBuilder#row, and serialize collapsed="1" in WorksheetWriter.

• Format classification helpers: Add Elements::Styles#format_code_for and #classification_for aliases, allow NumberFormatter format predicates (date_format?, time_format?, etc.) to resolve built-in formats by num_fmt_id, and expose format_type, date_format?, and time_format? on Elements::Cell.

• Date1904 accessor: Expose Ooxml::Reader#date1904? and add date1904: keyword argument to Elements::Workbook#initialize.

• Coordinate utilities module: Add Xlsxrb::Utils exposing public coordinate helpers (ref_to_row_col, row_col_to_ref, col_name_to_index, col_index_to_name, split_coordinate).

• Configurable trailing empty row trimming: Add trim_empty_rows option across Xlsxrb.read, Xlsxrb.build_worksheet, WorksheetParser.each_row, StreamSheet#initialize, StreamSheet#each_row, StreamSheet#each_row_values, StreamSheet#each, Elements::Worksheet#initialize, Elements::Worksheet#each_row, and Elements::Worksheet#each_row_values to omit trailing empty rows, and add empty? predicate to StreamRow and Elements::Row.

• Direct typed values streaming iterator: Add StreamSheet#each_row_values and Elements::Worksheet#each_row_values to stream row values directly as Arrays without allocating Elements::Cell objects, and add type_cast: true support across StreamSheet#each_row_values, Elements::Worksheet#each_row_values, StreamRow#values, and Elements::Row#values to coerce date/time serial numbers into Date and Time instances.

• Precomputed number format classifications in Styles: Add Xlsxrb::Elements::Styles (subclass of Hash) with precomputed $O(1)$ format classification lookups (number_format, format_type, date_format?, datetime_format?, time_format?, date_only_format?), update StylesParser.parse to return Elements::Styles, and add classification helper methods to Xlsxrb::NumberFormatter.

• Worksheet dimension and coordinate bounds: Expose dimension, first_row, first_column (aliased first_col), last_row, and last_column (aliased last_col) on StreamSheet and Elements::Worksheet (and Elements::CoordinateAccess), lazily extracting <dimension ref="..."/> in $O(1)$ memory without scanning the full sheet.

• Date1904 propagation to streaming sheets and rows: Propagate the workbook’s 1904 date system flag to StreamSheet and StreamRow, expose date1904? on StreamSheet, StreamRow, Elements::Worksheet, and Elements::Cell, and default Cell#to_date and Cell#to_time to the cell’s date1904 setting.

• Elements::RichTextRun: Add RichTextRun data class representing formatted text runs within RichText, supporting hash-like bracket access and seamless integration with Xlsxrb.rich_text.

• First-class conditional formatting and data validation on Elements::Worksheet: Expose conditional_formatting (and alias conditional_formats) and data_validations as first-class fields on Elements::Worksheet, populate them during round-trip parsing in Xlsxrb.build_worksheet, and serialize them in in-memory workbook serialization.

• Date1904 calendar system arithmetic: Support the 1904 date system (1904-01-01 base epoch) across serial date conversions, Cell#to_date, Cell#to_time, Elements::Workbook#date1904?, Ooxml::Reader, Ooxml::WorksheetWriter, Ooxml::WorkbookWriter, and StreamWriter.

• Row and column styles persistence: Expose style_index on Row, Column, and StreamRow, and persist row and column styles (<row s="..." customFormat="1"> and <col style="..."/>) during serialization and round-trip parsing.

• Styles metadata persistence: Support border colors, cell alignment, and protection attributes in stylesheet generation and round-trip parsing.

• Dual format support for num_fmts: Support both Hash ({ 164 => "format" }) and Array ([{ num_fmt_id: 164, format_code: "format" }]) structures for custom number formats in WorkbookWriter.

• Initial shared strings table seeding: Support pre-seeding sst in Xlsxrb.write when workbook.shared_strings is provided.

• Sheet visibility state: Support worksheet visibility state (state, hidden?, visible?) across StreamSheet, Elements::Worksheet, WorkbookParser, WorkbookBuilder, and WorkbookWriter, preserving :visible, :hidden, and :very_hidden visibility in streaming read, in-memory representations, and XML serialization.

• Workbook defined names: Parse <definedNames> in WorkbookParser and expose defined_names array and defined_name(name, sheet: nil) lookup on Elements::Workbook, supporting global and sheet-scoped named ranges and formula constants.

• Cell formula query and expression methods: Expose formula? predicate and formula_expression string accessor on Elements::Cell, and normalize empty formula expressions to nil in streaming and DOM cell parsing.

• Worksheet and cell hyperlinks: Parse and expose hyperlink metadata across StreamSheet#hyperlinks, Elements::Worksheet#hyperlinks, and Elements::Cell#hyperlink, #link?, and #url, supporting external targets and internal sheet references in streaming read, DOM models, and builders.

• Worksheet and cell comments: Parse and expose comment and note metadata across StreamSheet#comments, StreamSheet#comment, Elements::Worksheet#comments, and Elements::Cell#comment, #comment?, and #comment_text, supporting comment annotations and coordinate lookups in streaming read, DOM models, and builders.

• Number formatting engine and extended cell metadata: Add Xlsxrb::NumberFormatter supporting standard and custom OpenXML format codes (currencies, percentages, date/time, fixed-point padding, accounting patterns, scientific notation, and text), expose formatted_value, raw_value, and format_code on Elements::Cell, add formatted_value coordinate lookups on Elements::Worksheet, StreamSheet, and Elements::Workbook, and expose raw_values, formatted_values, and formulas metadata on Elements::Row and StreamRow.

• Fallback serialization for DOM model attributes: Support serializing first-class ws.state, ws.comments, ws.hyperlinks, and workbook.defined_names in Xlsxrb.write(workbook) when not explicitly packaged inside unmapped_data[:facade] metadata.

Changed

• Optimize chunked streaming read performance: Hoist </sheetData> tag lookup outside row iteration, eliminate byte delimiter array allocations, and terminate entry inflation early once worksheet rows are fully parsed, restoring streaming read throughput faster than in-memory read while preserving $O(1)$ memory consumption.

Fixed

• Fallback cached value for formula cells: Emit <v>0</v> instead of omitting <v> when a formula cell does not specify a cached value, ensuring compatibility with OpenXML parsers (such as Roo and LibreOffice) that discard formula cells lacking <v> elements.

• Shared formula cell parsing: Support self-closing formula tags (e.g. <f t="shared" si="0"/>) in WorksheetParser regex scanners, preventing cells containing shared formulas from being silently omitted.

• Fixed missing dcterms:created and dcterms:modified serialization in WorkbookWriter core properties (docProps/core.xml).

• Prevent Encoding::CompatibilityError in Xlsxrb.read and Cfb::Reader.cfb? when inspecting raw string buffers in UTF-8 encoding.

[0.1.13] - 2026-09-25

Added

• Non-destructive template modification: Support modifying existing XLSX templates while preserving unmapped parts, media, charts, drawings, and VBA macros via Xlsxrb.modify.

• StreamSheet structural metadata accessors: Expose merged_cells, auto_filter, data_validations, and conditional_formats on StreamSheet.

• Pre-Push Smart Change Detection: Optimized bin/pre-push --all to automatically skip runtime RBS validation and pure logic mutation testing when unrelated files are modified, adding --last and --force controls.

Changed

• True O(1) memory streaming read via chunked entry inflation in ZipReader and WorksheetParser, preventing unbounded memory retention on large worksheets.

• Extracted pure DSL normalizers (Xlsxrb::DslHelpers) and fast XML unescape utilities (Ooxml::XmlBuilder.unescape).

• Constrained rexml runtime dependency to ~> 3.0 and excluded documentation, build assets, and developer configurations from the gem package.

Removed

• OpenTelemetry runtime dependency and tracer spans.

[0.1.12] - 2026-09-20

Added

• Mutation Testing Framework (mutant):

• Full-scale integration of mutant test suite targeting the Functional Core (10 classes and modules, 38 subjects).

• Achieved 100.00% Kill Rate (1,091 / 1,091 mutations killed, 0 alive) without exclusions.

• Added dedicated root configuration .mutant.yml for streamlined CLI execution (bundle exec mutant run -- '...').

• Integrated bundle exec rake mutant:pure into GitHub Actions CI pipeline (main.yml), guaranteeing mutation-tested quality on every push and pull request.

• Added architecture and testing guide in docs/MUTATION_TESTING.md.

• Pre-Push Quality Verification Script (bin/pre-push): Added automated pre-push verification script running RuboCop, Steep type checking, RBS sync validation, Unit & Contract tests, RBS runtime type validation, and pure logic mutation testing, with automatic hook installation in bin/setup.

Changed

• Functional Core & Imperative Shell Architecture:

• Purified core business logic and domain entities into deterministic, side-effect-free class methods and predicates:

  • Extracted coordinate and validation predicates: Elements::Cell.valid_value?, Cell.valid_coordinates?, Cell.calculate_column_letter, Cell.calculate_column_index.

  • Extracted domain validation predicates: Elements::Row.valid_index?, Elements::Column.valid_index?, Elements::Worksheet.valid_name?.

  • Replaced date/time serial calculations in Ooxml::Utils with pure mathematical conversions (Julian Day math for date_to_serial, divmod arithmetic for serial_to_datetime, and 1900 leap year bug handling).

  • Extracted binary packing utilities in Ooxml::ZipGenerator (le16, le32, and bitfield arithmetic for dos_datetime).

  • Extracted pure XML character escaping logic in Ooxml::XmlBuilder.escape.

• Modularized Ooxml::Writer into domain-specific mixin modules (DrawingXml, FeaturesXml, StylesXml).

• Extracted shared DSL parameter normalization and range expansion into Xlsxrb::DslHelpers.

• Modularized reader SAX listeners into domain-specific parser components.

Fixed

• Boundary Validation & Error Reporting:

• Strictly validate row number digits in Elements::Cell.parse_ref to reject malformed cell coordinate strings (e.g. A0, A01).

• Harmonized supported value type checks and nil/empty handling across Elements::Cell.validate.

• Corrected maximum row index boundary error messages in Elements::Row.validate.

• Hardened cryptographic stream boundary checks and corrupted header handling in Standard and Agile encryption modes.

• RBS Runtime Type Validation:

• Expanded Elements::Workbook#initialize, #sheet, and [] type annotations to accept StreamSheet instances used by streaming readers.

• Made update block parameter optional in Elements::Workbook#update_sheet to allow testing missing block validation.

• Supported Numeric types (Float and Integer) in ChartBuilder and SeriesBuilder kwargs (width, etc.).

• Handled RBS::Test::Tester::TypeError in unit tests verifying block return type validation.

[0.1.11] - 2026-08-19

Performance

• Sub-Second Streaming Write (< 1.0s / 1,000,000 cells):

• Achieved sub-second streaming write performance (0.97 s median for 1M cells) while maintaining 100% full SST (Shared String Table) XML deduplication and ISO/IEC 29500 compatibility.

• Implemented 1-Pass Direct ZIP streaming pipeline, eliminating all intermediate tempfiles, disk seek-backs, and extra deflate flush cycles.

• Added dedicated unstyled fast-path in WorksheetWriter#write_row_values with precomputed coordinate and integer lookup tables.

• Pre-registered default date/time formatting styles, completely eliminating redundant per-row scan loops.

• Streamlined ZipWriter instance variable lookups to eliminate per-chunk hash overhead.

• Added alias << row to WorksheetProxy and StreamWriter for idiomatic Ruby streaming.

• High-Speed Streaming Read (1.61s / 1,000,000 cells):

• Reduced streaming read execution time from 3.40 s down to 1.61 s (over 2x speedup).

• Refactored Elements::Cell into an optimized lightweight class with Cell.fast_create, reducing 1M cell instantiation overhead by 5.2x (0.92s → 0.17s) while maintaining full pattern matching (deconstruct, deconstruct_keys) and immutability.

• Replaced per-byte Ruby scanning in WorksheetParser.fast_scan_cells_direct with an Onigmo C-level regular expression scanner (CELL_FAST_RE), eliminating 100,000 intermediate XML substring allocations and nested byte loops.

• Optimized StreamRow#cells to populate cell arrays via direct block traversal, eliminating Enumerator object allocations.

Documentation

• Updated benchmark results, performance comparisons, and linear-scale SVG charts across README.md and docs/PEER_LIBRARIES.md.

[0.1.10] - 2026-08-19

Added

• Peer Libraries Ecosystem Guide (docs/PEER_LIBRARIES.md): Introduced a respectful overview of the Ruby XLSX ecosystem featuring official self-descriptions, architectural tradeoffs (SST vs. Inline Strings, Streaming vs. In-Memory), and reproducible benchmarks across 9 popular Ruby XLSX gems.

• Visual Assets & Screen Previews:

• Embedded interactive WebAssembly Playground live demo preview in README.md.

• Added real-world Ruby LSP autocompletion and RBS type hint preview in README.md.

• Created accurate, neutral linear-scale SVG benchmark performance chart.

• Multi-Layered Test Suite Expansion:

• ECMA-376 XSD Schema Validation: XML schema validation suite ensuring strict element ordering and ISO/IEC 29500 compliance.

• Contract Testing Suite: Parity verification between Streaming (Xlsxrb.write) and In-Memory (Xlsxrb.build) APIs.

• Property-Based Testing (PBT): Expanded automated random generation tests for Row/Column invariants, styles, and edge cases.

• Visual Regression Testing (VRT): Added new visual baselines for table styles, drawing shapes, and pivot tables.

• E2E Interoperability Suite: Added tests for namespace-prefixed XML streaming, conditional formatting, and table structures.

Fixed

• WebAssembly (ruby.wasm) Compatibility: Bundled pp and prettyprint standard libraries in ruby.wasm package to resolve REXML LoadError during browser-based evaluation.

Changed

• Streamlined README: Refactored README from 363 to 175 lines, focusing on core motivation, clean 4-column feature matrix, concise usage examples, and direct links to specialized documentation.

[0.1.9] - 2026-08-18

Added

• Password Protection & Document Encryption ([MS-OFFCRYPTO] / [MS-CFB]): Full native Pure-Ruby support for reading, writing, and modifying password-protected Excel spreadsheets without any external C-extension dependencies.

• Standard Encryption: AES-128-ECB and SHA-1 Key Derivation with CryptoAPI 50,000-spin hashing, fully interoperable across Microsoft Excel, LibreOffice, and Google Sheets.

• Agile Encryption: Modern AES-256-CBC, PBKDF2/SHA-512, and HMAC-SHA512 data integrity verification.

• Compound File Binary (CFB) Engine: Pure-Ruby reader and writer for OLE structured storage containers with Mini Stream, FAT/MiniFAT sectors, and Red-Black tree directory management.

• Transparent Public API Integration: Added password: and encryption_mode: arguments to Xlsxrb.read, Xlsxrb.write, and Xlsxrb.modify.

• Security & Threat Model Hardening:

  • Constant-time hash verification via OpenSSL.secure_compare to prevent timing attacks (CWE-208).

  • CSPRNG-backed salt, IV, and session key generation via SecureRandom (CWE-330).

  • DoS defense: spinCount limit ($\le 10\text{M}$), CFB circular sector chain loop detection in directory/FAT parsing, and total_size bounds validation (CWE-400, CWE-835).

  • Strict exception hierarchy (EncryptedFileError, InvalidPasswordError, DecryptionError).

• Cross-Platform & Interoperability Validation: Bidirectional validation with Microsoft .NET OpenXML SDK and LibreOffice Calc.

• WebAssembly (ruby.wasm) Support: Pre-packaged docs/wasm/ruby.wasm updated with document encryption support for browser playground.

[0.1.8] - 2026-08-18

Changed

• Unified Symmetric Entrypoints: Consolidated reading into Xlsxrb.read (supporting file path, IO, and raw binary string) and writing into Xlsxrb.write (supporting streaming blocks or in-memory Workbooks). Removed legacy open, foreach, and generate methods.

• Streaming-First Defaults: Xlsxrb.read yields and returns lightweight StreamSheet instances with $O(1)$ constant-memory consumption by default.

• Explicit In-Memory Materialization (#load): Stripped accidental random-access memory traps from StreamSheet; introduced explicit StreamSheet#load / Workbook#load (inspired by ActiveRecord Relations) to transition from lazy streaming to in-memory Elements::Worksheet / Elements::Workbook.

• CoordinateAccess Module: Extracted coordinate lookup methods ([], cell_value, row_at, first_row, last_row, cells, cells_hash) into a dedicated Xlsxrb::Elements::CoordinateAccess mixin module included in Elements::Worksheet.

Added

• Default Cell Streaming (Xlsxrb::StreamRow): Enabled streaming along both row and cell dimensions via row.each_cell and sheet.each_cell, parsing cells on-demand to handle sheets with thousands of columns in $O(1)$ constant memory.

[0.1.7] - 2026-08-16

Added

• Bundled native Ruby LSP Add-on (RubyLsp::Xlsxrb::Addon) for zero-configuration, context-aware method autocompletion and rich markdown documentation in VS Code and LSP-enabled editors for block arguments (wb., s., sheet., stream_writer., stream_sheet.).

• YARD documentation (@param, @return, @example) across all public APIs, builders, proxies, and elements.

Developer Experience

• Enhanced rbs-inline type signatures across all facade methods and builder objects with automated RBS generation.

• Added VS Code Steep extension configuration for Dev Containers.

[0.1.6] - 2026-08-15

Added

• Support for unseekable IO streams (pipes, ActionDispatch::Response::Buffer, socket streams) across streaming reader and writer.

• Complete rbs-inline type annotations across all library source files and automated sig/generated/ synchronization in CI.

• Automated Steep static type-checking workflow in GitHub Actions.

• Hash-compatible symbol indexing in Elements::Row#[] (:cells, :index, :height, :attrs) and Elements::Cell#[] (:value, :ref, :style_index).

Performance

• Streaming Write: Replaced per-cell micro IO calls with row-level string buffering and fast-path serialization for unstyled cells (1,000,000 cells in 1.62s with standard SST).

• In-Memory Write: Optimized DOM serialization (WorksheetWriter#write_row) with row-level buffer aggregation, boosting 1,000,000 cells write from 22.33s to 4.06s (5.5x faster) and reducing GC count by 83%.

• Streaming Read: Implemented zero-allocation byte scanning for cell attributes (r="...", t="...", s="...") and direct integer conversion for SST indexes, cutting GC count by ~70% (129 -> 40) and boosting 1,000,000 cells read to 3.38s.

• In-Memory Read: Reduced peak memory footprint by 57% (582 MB -> 250 MB).

Documentation

• Overhauled benchmark.rb with bundler/inline for deterministic, zero-setup benchmark reproduction pinning peer gem versions.

• Updated README.md Motivation and Benchmark tables with verified default vs optional string storage architecture (SST vs Inline) and latest 1,000,000 cells measurements.

[0.1.5] - 2026-08-11

Added

• Functional API for updating existing files (Xlsxrb.modify).

• New Workbook#update_sheet and Worksheet#update_cell helpers for immutable data structures.

• Syntactic sugar for styles: in sheet.row using Hash and Range keys (e.g. styles: { 0..4 => "header" }).

• Support for inline anonymous styles as Hash objects (e.g. styles: { 0 => { font: { bold: true } } }).

• Support for Range and Array arguments in sheet.column to modify multiple columns at once.

• WorkbookBuilder#[] and StreamWriter#[] aliased to #sheet for elegant context switching.

• Block-based configuration for font and border properties inside StyleBuilder.

• Extensive inline RBS typing with strict generic types (eliminated untyped from the public API).

• Full RBS::Test runtime type validation enabled for the entire test suite.

• Extensive Excel limit warnings documented via YARD tags.

• Formal SemVer API contract with @api public tags for user-facing methods.

• Mutation testing (Mutant) and test coverage (SimpleCov) integrations.

Changed

• Replaced method_missing with statically defined, fully typed methods in WorksheetProxy, ChartBuilder, and SeriesBuilder.

• Removed deprecated instance_eval block context for builders; explicit block arguments are now required.

• Hardened security and bounds checking across the DSL for strict_excel_mode.

• Fixed numerous Rubocop linting violations and standardized style rules.

• Add specification reference policy and implemented specification mapping (docs/SPEC_SOURCES.md).

• Introduce unified event-based streaming and parsing architecture (Ooxml::Event and event streams for WorksheetParser/SharedStringsParser).

• Restructure test suite into four distinct tiers (Unit, Contract, E2E, Visual) and renamed facade_test.rb to public_api_test.rb.

• Add visual examples gallery (examples/visual/ and docs/visual/README.md) and promoted it via animated GIF in the main README.

• Implement visual regression testing (VRT) pipeline comparing generated sheets against reference baselines.

[0.1.0] - 2026-03-25

• Initial release