One quiet afternoon, a ticket came in from a garage. A customer, we will call her Anna, had signed into the portal to check on her car. The sign-in went perfectly. The portal even greeted her by name. She tapped through to her vehicle and found herself staring at someone else's car. Wrong make, wrong year, wrong plate, service notes mentioning a mechanic she had never met in her life. Her first thought, reasonably, was that someone had stolen her account. Nobody had. The sign-in had handed back exactly the right person. The famously solved problem of proving who you are was working flawlessly. The part underneath, the part that actually fetches your car, had grabbed the wrong record. Every sign-in light was green. The trouble was sitting somewhere those lights never shine.
The obvious fix would have been to comb through the sign-in. We did. It was spotless. The little sealed pass the system hands you when you walk in was correct in every way. The name on it was Anna. The session was fresh. By every textbook test, the system had correctly figured out who she was. The real problem sat one floor below. Two different garages each had a customer using the very same email address. Two real human beings, one shared inbox at a small family business. And the part that fetched the car was looking people up by email alone, because email was all it had been told, with no sense of which garage the request even belonged to. Sign-in told the system who. It never told the parts downstream where.
This is the trap nobody warns you about when you stitch tools together. Proving who someone is turns out to be the easy half. Knowing the context is the hard half. A customer is not just a name. They are a name, inside a particular business, in a particular role, on a particular device, in a particular language, holding a particular currency. Every one of those facts has to ride along with the request. When you have one tool, the context is invisible, because the tool only knows about itself. When you have five tools, the context has to be handed over out loud, or each tool will invent its own answer. Sometimes the answers disagree, and a customer ends up introduced to a stranger's car.
It bothered us more than the average bug, because it touched trust. So we spent a few intense days building what we think of as a context layer. The first move was a fast patch, just enough to stop the bleeding. Then we did the real thing properly. Now, every internal request carries a sealed, tamper-proof envelope describing not just who is asking, but which business, in which role, in which language, valid only for a short while. Every part reads from that envelope and never improvises. The envelope is checked at every step. If it is missing, the request is turned away. If the envelope says one business and the record belongs to another, the request is turned away. Today, Anna would have met a polite, firm refusal, not a stranger's car.
If you run a business stitched together from a handful of tools, you have already paid for this lesson without noticing. Each tool checks the user against your single sign-in. Then each tool decides, all on its own, what to show. The handoff between them carries an email, maybe a token, almost never a clean statement of this person is acting in this role, inside this business. So the tools improvise. One looks people up by email. One by phone. One by name. Sooner or later, two records collide, and a customer sees something they were never meant to.
The bill arrives as a steady drip of small embarrassments rather than one dramatic disaster. A loyal regular gets greeted as a brand-new lead. A discount lands on the wrong staff member. An invoice sails off to a company with a similar name. Each one is a five-minute sorry-about-that phone call. Five minutes times a thousand of those calls a year is a part-time job nobody is hiring for, and it gets paid entirely out of your customers' goodwill.
The cure is dull and unglamorous. Pick one true source for which business, one for which person, one for which role. Hand them over together in a sealed envelope, not as scattered scraps each tool reads its own way. Turn away anything that shows up without the envelope. You are not buying speed when you do this. You are buying the right to never have the Anna conversation again, and that is worth more than any of the tools you bolted together to avoid building it.