The Startup Fortune report says the applications are written from scratch in Rust and read and write DOCX, XLSX, and PPTX files; no Microsoft 365 account is required. Developer Brandon Thomas said he used Anthropic’s Claude Opus 5.5 to help write the code.
The report gives project-reported estimates that illustrate the gap between interface coverage and practical readiness: GridCraft covers 89% of Excel ribbon commands and about 93% of worksheet functions, while its README estimates it is about 50% ready for real work. WordCraft is reported at 87% of Word ribbon commands and about 62% overall completion. These are not independent assessments of compatibility or reliability.