SHT-01General arrangement
Software you rent makes you bend the business to fit it. A custom system does the opposite: your stages, your pricing rules, your documents, your data, in one place your crew can actually use.
SHT-02Live detail · drag it
This is the planner from a sauna builder's system, running here on demo data. It is the clearest answer to what custom means: no product you can buy has a sauna in it.
Drag one corner and its neighbours move with it. A diagonal wall prices a room nobody can frame, so the geometry refuses to make one.
The default is outward, and it is a safety rule rather than a preference: a door that opens inward onto a hot bench is a trap.
The framed opening is wider and taller than the door itself. The planner adds that margin so the crew is not doing it on site.
Every wall is drawn at the same scale on purpose, so two walls can be compared by eye without reading the numbers.
SHT-02ATiming diagram · inbound call
The card arrives in Telegram before the phone rings. Not moments after, not on a good day: the system waits for the card to be delivered before it tells the network to start ringing, so the order is guaranteed rather than hoped for.
Recording stays off unless it is deliberately switched on, and when it is, both sides hear that it is happening before the call connects. A call can never move a project by itself; there is a test whose only job is to fail if that ever becomes possible.
Ref · sauna-crm · app/api/twilio/voice/route.ts
Call reaches the system
Twilio posts the webhook
Who is calling is looked up
Matched against the client list
Card lands in Telegram
Name, number, last project
The phone starts ringing
Only now is the dial returned
SHT-03Detail callouts
These are the parts that pay for themselves: the work that used to depend on someone remembering.
An unknown number calls. Before the phone starts ringing, a card lands in Telegram with who it is, their number in a tappable format, and the last project they discussed. By the time it is picked up, the context is already there.
Ref · sauna-crm · app/api/twilio/voice/route.ts
The client opens a link, reads the estimate, and signs on their phone. The signature page is composited into the real PDF along with both names, the date, and the audit trail. Branding comes from the company record, so the document looks like the contractor's, not like ours.
Ref · sauna-crm · supabase/migrations/028_esignature.sql
Built on Stripe Connect so the money lands in the contractor's own account. The platform fee comes out of their payout rather than being added to the homeowner's total, and bank transfer is offered because on a large deposit the card fee is the difference between five dollars and a few hundred.
Ref · sauna-crm · lib/deposit-fee.ts
The crew moves a project forward by tapping a button in Telegram: deposit received, scheduled, work started, finished, paid. It refuses free text and voice notes on purpose, because one misheard word would move a real project.
Ref · sauna-crm · lib/telegram-actions.ts
When an estimate goes quiet, the system drafts the nudge and shows it. Nothing is sent until it is read and sent deliberately. It waits business days, stops after three attempts, and is not allowed to invent a number that is not already on the estimate.
Ref · sauna-crm · lib/followup-draft.ts
Reports that agree with each other because revenue is defined in one module. Crew payouts under one rule instead of three that disagreed. Stock that comes off the shelf when a client approves, once, even if the webhook fires twice. A calendar where an installer sees their own jobs.
Ref · sauna-crm · lib/revenue.ts, lib/installer-pay.ts
SHT-04QA schedule
Custom software is only worth it if it is right. These are the habits that keep it right, and each of them exists because something once went wrong without making a sound.
Run: 49 files, 557 passing
Every schema change, in order
They read the source, not the output
How a price is printed lives in one file. What revenue means lives in one file. When the same fact is computed twice, the two eventually disagree, and they disagree on a screen a client is looking at.
When a formula exists in the application and in the database, both move in the same commit or neither does. Otherwise the database quietly computes one number while the screen shows another.
Each one was run against the code that shipped the bug it guards against, and had to flag exactly that code before it was allowed in. A test that has never failed is decoration.
A query that errors and a query that finds nothing both return something falsy. Checks here are written so a mistake reports as a mistake instead of printing a confident zero.
SHT-05Comparative notes
Rented software is the right call more often than a studio will admit. Here is the honest line between them.
SHT-08Issued for construction
A short video walkthrough of where your lead flow leaks and what it would take to close it. Free, and there is no call afterwards unless you want one.
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