Solved
Worksheets and F8606 correctly show 2024 contribution made in 2025 but is not carrying the nontaxable contribution to basis. The taxable portion is treated as nontaxable, and the nontaxable portion is treated as taxable. Bug needs a software fix.
If you made a contribution in 2025 for 2024, then you cannot convert this basis in 2024 since it wasn't in your account in 2024. Contributions made in 2025 for 2024 are subtracted from the rest of the basis (see line 5 of Form 8606).
Please review How do I enter a backdoor Roth IRA conversion?
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