Local-first spreadsheet engine with a C11 native core, exact representable rational arithmetic, native formula evaluation/dependencies, predecessor-linked SHA-256 cell proofs, optional system SQLite ledger, narrow XLSX support, .NET 8 P/Invoke bindings and a Windows WPF client.
| Layer | Implementation | Verification boundary |
|---|---|---|
| Arithmetic | canonical int64 rational operations; private wide intermediates | native boundary/property tests and independent Fraction oracle |
| Formula | SUM, AVG/AVERAGE, MIN, MAX, COUNT/COUNTA, PRODUCT, ABS, ROUND, CEILING/FLOOR, lazy IF and numeric comparisons | native boundary tests, independent Fraction oracle and managed/native differential cases; bounded grammar |
| Dependencies | direct/range edges and filtered topological recalculation | failed-mutation regression; 100 random DAGs, 2,000 mutations |
| Integrity | ABI-96 cell proofs and optional SQLite metadata ledger | existing tamper tests; not encryption, identity authentication or backup |
| XLSX | supported native reader/writer subset; bounded ZIP validation | synthetic malformed/round-trip tests; not general Excel compatibility |
| Managed | P/Invoke and OPC utilities | lifetime/concurrency/malformed-image regressions pass; see ABI.md |
| Desktop | WPF editing, Undo/Redo, Find Next, freeze/selection indicators, formula syntax preview, typography/borders/wrap, number formats, dimensions and four themes | bounded XLSX style/layout import/export and WPF interaction contracts; see DESKTOP.md and FEATURE-GAP.md |
| Tables/charts | semantic ranges, exact SUM totals, coordinate-safe sort views; single-series Bar/Column/Line models, WPF rendering and XLSX parts | managed round-trip and actual WPF interaction tests; see TABLES.md and CHARTS.md |
| Localization | English controls; Unicode cell strings | complete localization/RTL workflows remain unverified |
cmake -S . -B build/release -DCMAKE_BUILD_TYPE=Release
cmake --build build/release --parallel 4
ctest --test-dir build/release --output-on-failureDisable the optional SQLite ledger explicitly with -DKHZ_ENABLE_LEDGER=OFF when its development package is unavailable. On Windows, use pwsh -NoProfile -File build-desktop.ps1.
For all local release checks and machine receipts:
pwsh -NoProfile -File scripts/verify-windows.ps1bash scripts/verify-linux.shCompiler warnings are errors by default. Managed projects are console assertion runners; use dotnet run for executed checks. dotnet test alone discovers no framework tests.
Read BUILDING.md, TESTING.md, ARCHITECTURE.md, NUMERIC-MODEL.md, FORMULA-LANGUAGE.md, ABI.md, XLSX-BOUNDARY.md, OPC-PRESERVATION.md, PROOF-CONTRACT.md, LEDGER.md and PQC-RELEASE.md. TABLES.md, CHARTS.md, LOCALIZATION.md, ACCESSIBILITY.md and DESKTOP.md distinguish implemented surfaces from absent capabilities.
SECURITY.md and THREAT-MODEL.md describe remaining boundaries. PERFORMANCE.md contains measured results and methodology. RELEASE-CHECKLIST.md defines the unfulfilled release gates. CHANGELOG.md records this intervention. evidence/20260929 contains normalized command evidence and hashes; private machine paths are not published.
This is a verified subset of the requested intervention, not a claim of production readiness, financial suitability or safe arbitrary-XLSX handling.