A camera that submits like a file input
A device produces a Blob; a form expects a FileList, and FileList is read-only. The one constructible path, and what it saves you on the server.
The prompt that Tesseract cannot read
The function signatures survived the engine swap. The shape of the answer did not — and that is where the cost of a stable boundary hides.
Two people, one row
Several people fill one submission together, none of them signed in. Tokens, seats, presence, and the row lock that stops a lost update.
A foreign key to any unique column
Two ways to point at a row of another form — by id, or by any UNIQUE column. Why the second exists, and what building SQL against runtime tables costs.
Six of the twenty-nine are not fields
A camera field produces a file minutes before the form exists. Uploading it early inverts ownership, and the fence that puts it back.
CORS for a write surface
Allow-Origin star is fine for a public feed and catastrophic for a write endpoint. A per-form allow-list, exact origin matching, and the preflight trap.
An offline queue that loses nothing
Queueing JSON is easy. Queueing a form whose photos were already uploaded is not. Negative placeholder ids, and the errors you must never retry.
Materialising a form as a real PostgreSQL table
JSONB stops paying off eventually. Here is how a user-drawn form becomes a real typed table, versioned outside django_migrations, additively.
An OCR result that knows which field it filled
Every OCR tutorial ends at image_to_string. Production starts there — attaching the text to a field, storing failures, and a confidence score that is not one.
Sixteen operators, six actions, two implementations
Conditional form logic in the browser is presentation, not validation. Keeping show, enable and require independent — and the half that must exist twice.
A form that does not exist when Django starts
A form builder means the form does not exist at import time. Here is the dispatch, the degradation rule, and the N+1 that a dict literal hides.