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SetTaskStatus was the only mutation on a task row, so a typo in a dictated task was permanent and a deadline could not move. EditTask rewrites the three fields capture set — text, due date and weight — and nothing else. Status stays the one-way ladder SetTaskStatus owns. Two things the task asked to settle. A text edit re-normalises the dedupe key and can collide with another live row. That is ErrTaskDuplicate, a refusal rather than a merge: two live rows carry two provenances, two capture times and possibly two external identities, and merging picks a winner for all three with nobody asked. The surface names the row that holds the text. A resolved task is refused outright (ErrTaskResolved). Its text is the record of what was finished, and rewriting it rewrites history. due nil clears the date, because clearing has to be sayable — an absent date and "remove the date" cannot be one argument.