A draughtsman draws a plan once, carefully, and then works to it; a plan redrawn from memory at every sitting is a different building by the third floor. A character described from memory at every job is redrawn each time, and every redrawing moves her a little. Written once on a draftingtable card and pinned above the table, she is drawn a single time, and every tool works to the same plan.
The card holds five lines in fixed order. Age, a plain number. Hair — colour, length, one habitual style. Build in two or three words. Face — one or two enduring details. Signature — the detail that survives a tight crop. Beneath the lines, the sitting line for the day: outfit, setting, hour, light. The sitting line is expected to change; the plan is not.
Paste the card word for word at the head of every prompt. Generate at the standard cost of 6 credits, keep the best third, and judge every result against the plan — not against the previous frame, which may itself have drifted off it.
Drift is not a model problem. It is a records problem. Keep the plan pinned, and the character holds her lines.