The What-If Explorer is an interactive stress-tester. You apply one or more "what if" changes on top of your saved plan, the Monte Carlo simulation reruns instantly with those changes layered in, and you see how each lever moves the result. Nothing you do here modifies your saved plan - clear the levers and the explorer returns to the baseline.

This is the tool for questions like "what if I retire two years earlier?", "what if SS gets cut 25% in 2033?", "what if I live to 95 instead of 88?", "what if I crank up spending 20%?" Each question gets a side-by-side comparison: your baseline plan on one side, the scenario-adjusted plan on the other, plus delta charts that quantify the change.

How it's organized

Scenarios are grouped into five tabs. The tab labels show a small badge with the number of active levers inside, so you can see at a glance how many changes you've stacked:

• Profile
  • Retirement-age delta (you and spouse)
  • Longevity-age delta (you and spouse)
  • Relocation (move to another US state mid-plan and watch the state-tax line shift). This is a quick state-tax what-if; it replaces your residence for the projection, so it's unavailable when your plan already includes relocation events. In that case, adjust their timing or destination on the Milestones & Events page instead - the nudge buttons on each event let you shift a move a year at a time and see the impact live.
• Spending
  • Global spending delta (% change to recurring spending; applies only to the discretionary portion once you've set Essential % on any expense row)
  • Spending shocks (one-time spikes at a specified age, e.g. a $50k expense at 70)
  • Inflation delta (raise or lower the plan's general inflation rate)
• Income
  • Social Security cut (configurable percentage and date range, the classic 2033-trust-fund scenario)
  • Part-time income (add wage income over a defined age window)
  • Pension lump-sum override (force a lump-sum payout in place of the configured stream)
• Investments
  • Return deltas for stocks and bonds
  • Asset-allocation overrides (force a different pre- and post-retirement mix)
  • Market-crash scenario (injects a sequence of bad years at a chosen age)
• Debts
  • Extra debt payment (apply a percentage extra to consumer-debt monthly payments)
  • Extra mortgage payment (same idea for mortgages)
  The tab is always visible, but its cards only do work on plans that actually carry debt.

How the output reads

Two surfaces sit side by side:

• Delta bar charts (left column) - show the baseline-vs-scenario gap on the headline metrics: success rate, median ending balance, lifetime taxes, and return assumptions. Bars are colored to indicate direction (better, worse, neutral).
• Monte Carlo chart (right column) - a full simulation chart of the scenario run, with the same percentile bands and median path as the dashboard. Useful when you want to see when the gap opens up, not just the bottom-line number.

Each tab also surfaces context-specific insights underneath the relevant cards - things like "Debt-free 4 years earlier" or "$67k less lifetime tax" or "Spending change: +$1.4M lifetime cost" - so you can read off the headline impact without having to interpret bar lengths.

Stacking and clearing scenarios

You can stack as many levers as you want - apply a longevity delta, a spending delta, and an SS cut simultaneously, and the simulation runs them all together. Each tab has its own clear control to zero out just that group, or you can clear everything and return to baseline.

What's saved and what isn't

Scenario state lives in your browser's local storage, so the same browser remembers your stacked scenario across reloads but a different browser or device starts fresh. Scenario state never overwrites your baseline either way - the dashboard and Plan Report continue to reflect the saved plan, not the Explorer state. If you want to make an Explorer scenario "real," edit the saved plan inputs to match (e.g. change retirement age on the Profile page rather than via a delta in the Explorer).

What-If Explorer vs the Optimizers

The Explorer is open-ended: you decide what to vary and read off the impact. The optimizers - Social Security, Pension, Roth Conversion, and Spending - are goal-directed: each sweeps a parameter space to find the value that maximizes a chosen metric. The two approaches are complementary. A common workflow is to use the Explorer to find the lever that seems most promising, then point the matching optimizer at that lever for a more rigorous search.