Reign

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Don't know where you stand financially, or if you can retire? Give the 3 minute demo a try for free.

Inspiration

Every personal finance tool ends the same way: a dashboard, and you doing the reasoning.

Mint-style apps categorize spending. Budgeting apps track envelopes. The good FI/RE tools hand you a retirement age and a Monte Carlo chart. None of them understand your situation well enough to tell you what to do next — with your accounts, your rates, your numbers.

I wanted software that behaves less like a report and more like an advisor who has actually read your statements: one that notices your employer match is underfunded, debt payoff priority, and says in plain language what changed and why it matters.

What it does

Reign is intelligent finance middleware—not a bank, lender, or a budgeting app.

It reads a user's real accounts through Plaid and builds a living picture of their path to financial independence and how to get there.

Then it runs in the background—daily updates, weekly briefs, alerts when balances or spending drift, and a recommendations engine that surfaces concrete opportunities.

Dashboards show. Reign does.

How we built it

This is the boring but necessary stuff:

Next.js deployed to Vercel
Supabase for auth and database (Postgres + Row Level Security)
Plaid for account and transaction data
Stripe for payments
Gemini for the entire reasoning layer
Claude as my coding companion

One architectural rule shaped everything else: Gemini ingests numbers and outputs language. It never generates a projection. Every FI figure—retirement age, FI number, scenario modeling—is computed deterministically by a shared financial-math engine and handed to the model only as context to narrate.

That rule came from an early failure: given room to compute, the model produced plausible, confident, wrong number calculations.

Every Gemini call routes through a shared wrapper, logAgentEvent, that writes latency, token usage, and success/failure to an agent_logs table. The AI's behavior in production is auditable, not a black box.

Challenges we ran into

Enforcing that rule was harder than stating it.

Even with the model barred from computing, its narrative would occasionally cite a FI age different from the one the app had just computed.

Prompting alone never closed the gap.

What did: a chain of validators that checks every AI-generated surface—onboarding, weekly brief, live chat—against the real computed values before anything reaches a user, with automatic retry on mismatch and monitoring.

The harder bug to solve looked like a hallucination and wasn't.

Adversarial testing against a live account caught the chat agent confidently telling a user they had already reached financial independence. Round after round of prompt fixes did nothing, because the problem sat underneath the prompt:

Vercel doesn't guarantee that fire-and-forget work after a streamed response completes, so the validation and logging callback silently never ran and the model reasoned from bad context. waitUntil() fixed it. Some of the scariest AI failures are plumbing bugs wearing a trenchcoat.

Accomplishments that we're proud of

The correctness discipline we built around letting an LLM sit this close to real money.

One math engine is the single source of truth for every number in the product, and every AI surface is validated against it before display.

Plaid accounts and manually entered ones merge additively down a single canonical computation path, so a user's FI age is identical across the app.

That's what makes the AI operational rather than decorative. Gemini isn't a chat widget bolted onto a dashboard; it's the layer that decides what a user is told to do next, running under constraints strict enough that we'd point it at our own accounts.

What we learned

Live adversarial testing catches a class of bug that unit tests, type checking, and static review all miss. Both of our most serious correctness failures were found by a person deliberately trying to break the running product—and one of them had a root cause four layers below the prompt. When an AI system says something wrong, "the model hallucinated" is a hypothesis, not a diagnosis. Trace all the way down before you accept it.

What's next for Reign

Reign is built on a strong foundation with a proven math engine, golden fixtures, and capable intelligence. From here, we have a lot of work to do to improve the user experience and education. The tooling exists, the ease-of-use is not were it needs to be.

Upcoming work:

Intelligent task recommendations
Cash flow modeling
Retirement modeling and burndown
Finance optimization planning
Financial independence modeling
Investment portfolio analysis

Look, here's the real honest future of Reign and where I want this product to go...

I want Reign to save the world. Really, seriously.

Tell me if you've heard any of these:

"I'm never going to be able to retire"
"I can't afford to buy a home"
"It's all the billionaires fault"
"It's all the boomers fault"
on and on

Financially, most people are in trouble. They want someone or something to blame. They don't know what to do for themselves or they don't have the knowledge and time to figure it out.

The facts:

Approximately 77% of American adults carry debt
Roughly 48% feel they are struggling or the situation is worsening
Around 65% of non-retired Americans are not on track for retirement
Half the country have less than $100k in savings
Professional money management costs roughly $3000-6000 per year
Most professional money manager do not outperform the market, even under perform

Reign will change that.

Reign is not biased, scheming, pushing a particular investment vehicle, doesn't get emotional. Reign evaluates a person's financial status and optimizes for best results.

Reign is foundational in its financial perspective. Not gambling, not hoping, or placing all the chips on a single stock. Reign follows core financial principles for operation and works with each user in their unique situation to clearly optimize income, spending, saving, investing with an easy to understand plan.

Reign is your best smart financial friend, not a rando on Reddit posting about their killer portfolio.

This should already exist, there's no reason this type of system can't exist — except that the philosophy goes against institutions and money makers and media headlines.

Earn money. Spend less than you have. Save. Invest. Play the long game. Improve. Reinvest. And you will live well and retire.