{"model":"backdoor-roth","specVersion":"1.0.0","specUrl":"/api/v1/models/backdoor-roth/spec","inputs":{"nondeductibleContribution":{"kind":"float","min":500,"max":7500},"existingPretaxIraBalance":{"kind":"float","min":0,"max":2000000},"marginalRate":{"kind":"float","min":0.1,"max":0.37}},"arrayInputs":{},"constraints":["nondeductibleContribution max is the TY2026 IRA limit (facts registry irs.ira.contribution-limit.2026); existingPretaxIraBalance aggregates all traditional/SEP/SIMPLE IRAs and is assumed fully pre-tax."],"sentinels":[],"facts":[{"id":"irs.ira.contribution-limit.2026","label":"Traditional/Roth IRA contribution limit","value":7500,"period":"TY2026","source":"IRS TY2026 announcements (Notice 2025-67; Rev. Proc. 2025-32 newsroom page)"}],"disclaimer":"Illustrative planning model, not financial advice. Outputs follow the published model spec exactly; read the spec for assumptions and exclusions before relying on any number."}