The IRS open sourced their direct-file code after it got cut. IIRC similar work done there. https://github.com/IRS-Public/direct-file
One past thread:
IRS Direct File - https://news.ycombinator.com/item?id=44131901 - May 2025 (65 comments)
IRS Direct File - https://news.ycombinator.com/item?id=44131901 - May 2025 (65 comments)