Critical bug fixes found during comprehensive codebase audit.

• Image embedding broken — generateDrawingXml rId off-by-one causing images to silently fail
• Frozen panes: wrong activePane — column-only freeze wrote "bottomLeft" instead of "topRight"
• Invalid JSON for NaN/Infinity — write_f64_json now writes null instead of crashing JSON.parse
• Custom numFmt ID collision — resolveNumFmtId now always assigns IDs >= 164 per ECMA-376

• HashMap::with_capacity in ZIP reader
• col_index_to_letter delegates to optimized col_to_letters
• TextEncoder hoisted to module-level constant

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Closed 7 SheetJS advantage categories + added native Excel Tables, headers/footers, row/column grouping, and print layout. 704 tests (217 Rust + 487 TypeScript).

• encodeRow() — convert 0-based row index to 1-based string
• decodeRow() — convert 1-based row string to 0-based index
• splitCellRef() — decompose $A1ドル into { col, row, absCol, absRow }

• appVersion — roundtrip <AppVersion> from app.xml
• hyperlinkBase — roundtrip <HyperlinkBase> from app.xml
• revision — roundtrip <cp:revision> from core.xml
• application, company, manager — now fully parsed and written

• sheetToTxt() — tab-separated text output (reuses CSV engine with \t delimiter)
• sheetToFormulae() — extract all cell values and formulas as ["A1=100", "A3='SUM(A1:A2)"]

• Conditional sections — parse [>100]#,##0;[<=100]0.00 with condition evaluation
• Bracket color codes — extract [Red], [Blue], [Color3]–[Color56] from format strings
• formatCellRich() — returns { text, color } with color metadata
• loadFormat() — register custom format code at runtime
• loadFormatTable() — bulk-register format codes by ID

• ws.usedRange — computed getter returning cell extent (e.g., "B2:D5") or null
• ws.tabColor — getter/setter for sheet tab RGB hex color, roundtrips through WASM

• cell.numberFormat — resolves style index → numFmtId → format code string
• cell.dateValue — returns Date if cell contains a date-formatted number
• Stub cell type — 'stub' in CellType union for explicitly empty cells (SheetJS type "z")

• dynamicArray — roundtrip cm="1" attribute on <f> element for SPILL/dynamic array formulas

Category	v0.4.0	v0.5.0
Worksheet operations	Tie	modern-xlsx wins
Cell operations	Tie	modern-xlsx wins
Formulas	Tie	modern-xlsx wins
Document properties	SheetJS wins	modern-xlsx wins
Cell ref utilities	SheetJS wins	Tie
Number formatting	SheetJS wins	modern-xlsx wins
Sheet conversion	SheetJS wins	SheetJS (gap narrowed)

• Full OOXML Table read/write — native xl/tables/table{n}.xml support with SAX parser and XML writer
• ws.tables — getter returning all tables on a worksheet
• ws.getTable(name) — find table by name
• ws.addTable(opts) — create table with name, ref, columns, style, totalsRow, autoFilter
• ws.removeTable(name) — delete table by name
• 60 built-in table styles — TABLE_STYLES.light (1-21), .medium (1-28), .dark (1-11)
• VALID_TABLE_STYLES — ReadonlySet for style name validation
• TotalsRowFunction — type for totals row calculations (sum, count, average, etc.)

• ws.headerFooter — getter/setter for HeaderFooterData with odd/even/first header/footer
• HeaderFooterBuilder — fluent builder with left(), center(), right(), build()
• Static formatting helpers — pageNumber(), totalPages(), date(), time(), fileName(), sheetName(), filePath()
• Text formatting — bold(), italic(), underline(), strikethrough(), fontSize(), fontName(), color()

• ws.groupRows(start, end, level?) — set outline level (0-7) on row range
• ws.ungroupRows(start, end) — remove outline level from rows
• ws.collapseRows(start, end) — collapse grouped rows
• ws.expandRows(start, end) — expand collapsed rows
• ws.groupColumns(start, end, level?) — set outline level on column range
• ws.ungroupColumns(start, end) — remove outline level from columns
• ws.outlineProperties — getter/setter for summary row/column position

• wb.setPrintTitles(sheet, opts) — set repeating rows/columns via _xlnm.Print_Titles defined name
• wb.getPrintTitles(sheet) — get current print title configuration
• wb.setPrintArea(sheet, area) — set print area via _xlnm.Print_Area defined name
• wb.getPrintArea(sheet) — get current print area

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Declarative table generation API with styled headers, zebra striping, auto-width, merge cells, and multi-table composition. Critical bug fixes across WASM init, writer performance, and sheet conversion utilities.

• drawTable(wb, ws, opts) — generate styled XLSX tables from declarative options, no manual cell coordinate math
• drawTableFromData(wb, ws, data, opts?) — create tables from JSON arrays with auto-extracted headers and headerMap display names
• Header styling — customizable font, background color, and alignment with sensible defaults (bold white on #4472C4)
• Body styling — zebra striping via alternateRowColor, configurable borders, font, and alignment
• Auto-width — content-aware column width calculation with CJK double-width character support
• Per-cell style overrides — cellStyles map with "row,col" keys for targeted formatting on top of base styles
• Merge cells — row and column spanning via merges array (0-based, relative to data area)
• Column definitions — TableColumn with per-column width, alignment, and number format (e.g. '$#,##0.00')
• Freeze header — freezeHeader: true freezes the header row for scrolling
• Auto-filter — autoFilter: true adds filter dropdown arrows to header cells
• Nested composition — use TableResult.lastDataRow to stack tables vertically with gap rows
• Side-by-side composition — use origin column offsets to place tables horizontally

• jsonToSheet startCol — writeDataRow now respects the startCol parameter instead of ignoring it
• resolveNumFmtId sort assumption — no longer assumes the numFmt array is sorted, uses correct lookup
• initWasmSync race condition — concurrent initWasm calls no longer conflict with synchronous initialization
• frozenPane field names — table engine uses correct rows/cols field names for frozen pane data
• WASM reader HashSet rebuild — eliminated unnecessary HashSet reconstruction on every read operation
• Comments clone — removed avoidable .clone() in comments path handling
• Writer insert shift — replaced Vec::insert(0, ...) O(n) shift with efficient prepend pattern

• columnToLetter / letterToColumn — corrected examples that used wrong indices
• serialToDate — fixed example showing wrong return type
• addValidation — corrected example using wrong field name
• Rich text — fixed example that accessed private fields

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Pure TypeScript barcode/QR generation with 9 formats, PNG renderer, and XLSX embedding. Full codebase audit with critical bug fixes. 437 tests (157 Rust + 280 TypeScript).

• 9 barcode formats — Code 39, Code 128, EAN-13, UPC-A, ITF-14, GS1-128, QR Code, Data Matrix, PDF417
• renderBarcodePNG() — pure TypeScript PNG renderer (no external dependencies)
• generateBarcode() — one-call XLSX embedding with drawing XML and relationships
• generateDrawingXml() / generateDrawingRels() — low-level drawing XML generation
• Multi-image accumulation — multiple images per sheet without data loss

• Unicode panic — validate.rs byte-indexing multi-byte characters → chars().take(n).collect()
• Multi-image data loss — addImage() now accumulates via Maps instead of overwriting drawing XML
• SST insert performance — Entry API replaces double hash lookup in shared_strings.rs
• Comments author dedup — Entry::Vacant pattern eliminates double lookup in comments.rs
• DXF diagonal attrs — eliminated redundant UTF-8 decoding in styles.rs

• GF(256) lookup tables hoisted to module-level constants (Data Matrix encoder)
• Array.prototype.at(-1) for O(1) sorted-array access (utils.ts, style-builder.ts)
• split_once(':') replaces split(':').collect::<Vec<>>() in validators
• Single TextEncoder instance in QR encoder (was creating two)

• All docs updated for v0.3.0 accuracy
• Barcode generation examples in playground
• Migration guides updated with barcode comparison

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Browser-first release with IIFE bundle, CDN distribution, Web Worker support, and framework examples. 419 tests (171 Rust + 248 TypeScript).

• IIFE build — self-contained modern-xlsx.min.js (~29 KB) exposing window.ModernXlsx
• CDN distribution — available on jsDelivr and unpkg, no bundler required
• detectWasmUrl() — auto-detection of WASM binary URL from document.currentScript.src
• initWasmSync(module) — synchronous WASM initialization from pre-loaded buffer
• ensureReady() — lazy auto-initialization on first use (cached Promise pattern)
• Source maps — .map files generated for all build outputs (ESM, IIFE, Worker)

• createXlsxWorker() — off-thread XLSX read/write via Web Worker message passing
• modern-xlsx.worker.js — dedicated worker script with auto WASM init
• Transferable buffers — zero-copy transfer of Uint8Array results back to main thread

• tsdown 3-build config — ESM (primary), IIFE (browser), Worker (off-thread)
• Package exports — "." (ESM), "./browser" (IIFE), "./worker" (Worker script)
• browser / unpkg / jsdelivr fields in package.json for CDN auto-resolution

• Interactive browser playground at docs/site/playground.html
• 6 built-in examples: Hello World, Styled Workbook, Read & Inspect, Batch Data, JSON to Sheet, Formulas & Dates
• Live WASM status indicator, Ctrl+Enter execution, download integration

• React — hooks-based integration with useEffect WASM init
• Vue 3 — Composition API with onMounted WASM init
• Svelte 5 — $effect rune-based WASM init
• Angular — service-based WASM init with standalone components

• Cloudflare Workers — XLSX generation at the edge
• Deno Deploy — server-side XLSX with Deno-native imports
• Service Worker — offline XLSX generation with custom WASM URL

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Complete 0.1.x hardening series. 419 tests (171 Rust + 248 TypeScript).

• Style roundtrip: gradient fills, diagonal borders, DXF styles, cell named styles
• Formula metadata: array formulas, shared formulas, formulaRef, sharedIndex
• Feature roundtrip: hyperlinks, comments, data validation, conditional formatting, sheet protection, page setup
• Edge cases: empty workbooks, malformed XML, boundary values
• Error handling: corrupted files, invalid inputs, graceful degradation
• Streaming & benchmarks: 100K row read/write, parallel parsing, buffer scaling
• Utilities: cell refs, dates, format codes, CSV/HTML/JSON conversion

• push_entity() — zero-allocation XML entity resolution
• Vec::with_capacity() on all XML parse buffers (11 sites)
• from_utf8().unwrap_or_default() replaces from_utf8_lossy() (6 sites)
• entries.remove() in StreamingReader — moves data instead of cloning
• drain() in collect_preserved() — moves preserved entries
• #[non_exhaustive] on error enum

• Module-scoped CELL_REF_RE regex (hoisted from hot loop)
• isolatedDeclarations: true in tsconfig
• Shared WASM init via __tests__/setup.ts

• Migration guide: SheetJS
• Migration guide: ExcelJS
• Usage examples cookbook
• Release roadmap

• GitHub Actions pinned to stable versions
• Rust toolchain: @stable
• Node.js engine: >=24.0.0

---

First public release.

• Full XLSX read/write with Rust WASM core
• Cell styling — fonts, fills, borders, alignment, number formats via StyleBuilder
• Data validation — list, number, date, text length, custom formula
• Conditional formatting — color scales, data bars, icon sets, formula-based rules
• Frozen panes, hyperlinks, comments, sheet protection, page setup
• Rich text with RichTextBuilder
• Named ranges, document properties, workbook views, calc chain
• Streaming reader/writer for large files
• Parallel sheet parsing (rayon)
• Cell reference utilities, date utilities, format utilities
• Sheet conversion utilities (JSON, CSV, HTML, array-of-arrays)
• Browser Blob download support
• 342 tests (170 Rust + 172 TypeScript)

Operation	modern-xlsx	SheetJS CE	Factor
Read 100K	1,155 ms	4,927 ms	4.3x faster
Write 100K	5,048 ms	5,048 ms	1.0x
sheetToJson 10K	54 ms	103 ms	1.9x faster