Solentrex · 2026
Lender certification, and the money math
I rebuilt the financing integration, passed the lender's certification at 100 of 100 addresses, and built the checks that catch pricing and savings errors before a customer sees them.
What it was
Every proposal we send a homeowner is a financial document. It quotes a system size, a monthly payment, and twenty five years of projected savings, and a lender underwrites a loan against those numbers. I inherited the integration that produces them.
Two things had to be true at once. The lender had to certify our design output as accurate enough to fund, and the money on the page had to be right.
What I did
I rebuilt the financing integration end to end: the design and pricing payload we send, the webhooks that come back, and the loan states in between. Then I ran the lender's certification set and passed it at 100 of 100 addresses.
The math was the harder half. I stopped reading the code and started checking the numbers against real production data, because that is the only way to know what a system actually produces.
| What I built | How it is proven |
|---|---|
| One savings engine instead of several copies | The escalation schedule runs through a single shared function, verified live in production against the contract terms rather than against my reading of the code. Landed across 14 merged pull requests. |
| An approved-loan audit | Every approved loan in production is checked against its own design record, so the system size on the loan and the system size on the design have to agree. |
| Adder pricing checks | Multi-adder pricing is reproduced against real production proposals, so the loan amount has to match the quote. |
| Guards on the lender's limits | Values are validated against the lender's published limits before they are sent, so anything out of range is caught on our side. |
| A standing sweep over the financing surface | A parallel agent audit runs across live proposals and reports anything whose displayed state does not match its own record. |
What it produced
The integration is certified and live, and the savings math now runs through one shared function instead of several copies, which let me delete about a thousand lines of dead code.
The part I care about is the order of events. The checks run on production data before a homeowner ever signs, which is the only point where finding something is still cheap.