What got measured, and what it cost.

A BLE backfill path rejected 99.3 percent of the records it asked for, then acknowledged the delete so the device wiped its own buffer. Two ordinary bugs, each survivable alone, destructive together.

Same coordinates, same minute, four providers, a 5.7 degree disagreement about the current temperature. One reported zero precipitation while the others reported rain. What that costs anything built on one upstream source.

The first Lina pilots shipped on the GPT-4o transcription API. It came out three months later. Self-hosted Whisper large-v3 turned out faster, cheaper, and quieter on the DSGVO front.

One webhook per call event collapsed the practice's n8n bridge at the 8 to 10 am peak. An append-only log fixed the retry storm in two and a half days.

Voiceflow carried the first three demos, but the block model could not hold the uncertainty gate. Replacing it with a TypeScript node graph where safeguards are middleware.

Intent classifiers route to a handler; hand-off architectures route to a human. Why four parallel safeguards end up safer for medical calls, and the over-escalation trade-off you accept in exchange.

Signing the AVV is the easy 30 percent. The harder 70 percent is what the practice itself owes: patient notices, § 203 StGB authorisation, and the AI Act Art. 50 disclosure.