Plan Diagnostics is FIREproof's automated review of your saved simulation. After a run, the engine inspects the result for known anti-patterns and missed opportunities, then surfaces a Diagnostics button on Proof and a full drawer of expandable items.

The Diagnostics button on Proof

The Diagnostics button sits under the success rate at the top of the Proof view, next to Share. Its red badge counts the items that need attention plus the opportunities; assumptions and notes are left out of the badge. Hover the button for the count of every severity, and click it to open the full drawer. The sidebar's Diagnostics entry shows the same count and opens the same drawer. Dismissed items drop out of both counts.

Severities: needs attention vs. opportunity

• Needs attention (red). Something in the plan is failing or actively hurting outcomes: portfolios depleting, ACA cliffs being crossed, mandatory contributions triggering early-withdrawal penalties.
• Opportunity (teal). The plan works, but a different choice would likely improve it: unfilled bracket headroom for Roth conversions, suboptimal withdrawal ordering, FAFSA-shaping options for households with dependents.
• Assumption (amber). Calls out an input the engine had to guess or that most users would benefit from reviewing.
• Information (blue). Neutral context, not a recommendation.

Surplus Deposit Capacity alert

When working-year surplus exceeds your retirement accounts' IRS contribution limits and your plan doesn't have a taxable brokerage to absorb the rest, the engine routes the residual into your checking-style account as cash. This pushes allocation off-target and gives up the growth that money would otherwise earn.

The Surplus Deposit Capacity alert in the drawer counts the cycles where this happened and sums the dollars that landed in cash. The recommended fix is to add a taxable brokerage or investment account and place it in your cash-flow priorities, so surplus has somewhere to go and the rebalancer can keep allocation on target.

Debt and retirement cash flow

A loan or HELOC above the plan's riskless nominal yardstick is flagged when surplus is deposited and no Cash Flow Priority targets that debt. The yardstick is the funded ratio's real discount rate plus median inflation. Use Rank a Debt Paydown priority to choose its place in your savings order.

A balance still open in the retirement year raises a warning with the remaining payment years within the simulation and a tax-cost proxy: the payment times the estimated marginal rate. This is not an exact withdrawal tax calculation. Loan payoffs can also trigger the cash-flow redeployment nudge, and loans alongside idle cash are measured by their balance.

Early retirement with a pre-tax-heavy portfolio

When you retire at least three years before 59½ with 40% or more of your liquid money in pre-tax accounts, the drawer points out the bridge years those accounts are penalized. A 401(k) or 403(b) with a Rule of 55 age you have reached by retirement does not count toward that 40%, since its withdrawals are not penalized. Roth conversion ladders, 72(t) SEPP plans and the Rule of 55 are the three standard ways to close the gap.

Snoozing and dismissing

Each diagnostic can be dismissed once you've considered it. Dismissals are scoped per saved simulation and are tied to an evidence hash. If the underlying numbers change in a later run, the diagnostic re-appears so you don't unintentionally hide a fresh problem.

Use the Show dismissed toggle in the drawer to bring previously-dismissed items back into view and undismiss them.

Comparison shortcuts

Many diagnostics include action buttons that wire directly to a virtual A/B comparison:

• Roth Conversions. Runs a "without conversions" virtual sim and opens it in Compare Sims.
• ACA Cap. Runs a virtual sim with the ACA subsidy cap inverted.
• Social Security Timing. Opens the What-If modal pre-loaded for the Social Security Reduced slider.
• FAFSA Optimize. Runs a virtual sim with FAFSA-optimized withdrawals enabled for the affected dependent.
• Defer Roth Conversion. Runs a virtual sim with the offending conversion shifted past the FAFSA base-year window.

ACA Cap, FAFSA Optimize and Defer Roth Conversion compare against a Pro feature, so without Pro they show locked with a Get Pro button instead of running.