The recompute solved each Case's FIRE number with an independent binary search,
so Monte-Carlo path noise + the coarse £15k tolerance made Family (Household + 2
kids) tie or even UNDERCUT Household (6 hard inversions + 5 exact ties across the
22 countries) — the ~£20k kids cost quantised to ~£0.
Now solve the Cases in increasing-cost order and lower-bound each by the previous
Case's target on the SAME return paths: a heavier Case (more spend / +kids /
+home) can never need less net worth than a lighter one, so
Solo <= Household <= Family <= Family+home holds by construction. tol tightened
15k -> 1k so the genuine but small kids/home increment resolves instead of
snapping to the previous grid step. Kids/home were already modelled correctly
(verified) — this is purely a solver-resolution + monotonicity fix.
Found + verified via the fire-countdown flaw-hunt workflow. 346 tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Add a Monte-Carlo "FIRE number" solver so the wealth dashboard can show a £
countdown to retirement across life-stage cases, in today's money.
Viktor wants to see, per country, how far his net worth is from being able to
retire for good under three cases — Solo (his spend ×1.5), Household (+Anca
×1.5), Family (+2 kids) — with cost-of-living re-scaling per country and a 99%
Guyton-Klinger success bar.
- spend_model: per-Case real-GBP spend, COL-scaled (rent + non-rent essentials
scale by country; Holidays fixed), ×1.5 safety. Constants sourced live from
actualbudget (Viktor) / on-record (Anca).
- geo: city -> tax jurisdiction (nomad fallback).
- fire_target: binary-search the smallest LIQUID net worth where GK reaches the
bar; pension modelled as a tranche unlocking at ~57, kids ramp + optional home
as cashflows. New fire_target table (migration 0007) + idempotent upsert.
- recompute-fire-targets CLI: solve every Case x country and persist for Grafana.
- CONTEXT.md glossary + ADR-0001 (why MC-threshold on liquid NW, not 25x spend).
Reuses the existing simulator unchanged (its cashflow hooks already supported
pension/kids/home). 345 tests pass; mypy + ruff clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
