Test retirement risk with historical market shocks

They used Claude to model a retirement portfolio and check whether spending would still hold up through past bear markets and extra home costs.

Done with Claude· Advanced· Sep 2026

What they did
They rebuilt their retirement setup in Claude and asked it to project a 60/40 portfolio across 15 to 20 years. The model started from a 6% growth path, then mixed in two or three past bear markets at random points and added one-off home-improvement expenses. In comments, they said they had first laid out a month-by-month budget so recurring costs and drawdowns were easier to see, and that Claude separated the stock and bond pieces.
How it went
The exercise backed up their view that planned income and spending would probably last for more than 20 years. The main warning from the thread was trust: several people said not to accept Claude’s numbers at face value and to check the model, or have it generate code or spreadsheet formulas first.
Tips
Use clear assumptions before you start, especially for withdrawals, recurring expenses, and market-shock timing. Pause and review the setup before any submission or decision, and validate the math in code or a spreadsheet if the results matter.

Try it yourself with Claude Code

Help me stress-test my retirement plan. Use a [stock/bond allocation] portfolio with a starting balance of [amount], annual spending of [amount], and a horizon of [number] years. Build a base growth path using [assumed annual return], then run a Monte Carlo-style test that randomly places [two or three] historical bear markets, such as [example years], somewhere in the early and middle years. Also include one-time costs for [home repairs or other expenses] at [timing]. First, show me the assumptions you will use and ask for my approval before you run the model or make any irreversible changes. Then report the chance of lasting the full period, the worst balances, and a plain-English summary.

Fill in the [brackets]. Agents can make mistakes, so review anything before it is sent, paid or deleted.

Read the original on reddit.com ↗

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