A delivery note's cost price is what the business paid. Editing it
while setting a margin rewrites that silently, so a stray keystroke
changes every downstream number on the note without ever looking like
a pricing decision.
The rule lives in quote-pricing.ts as a `costLocked` flag captured at
load time, and repriceLine DROPS a cost patch on a locked line. That
is the guarantee; the read-only cell in the UI is only the
convenience, so no caller can quietly rewrite the cost.
- "Edit note" and "Create quote" grids: cost is read-only with a lock
icon once the line arrived costed; a blank cost stays fillable and
still seeds the 25% default markup on first entry.
- readOnly, not disabled, so the number can still be selected and
checked against a supplier invoice.
- Locked at load, not per keystroke: a cost typed in this session
stays correctable until save (an operator choice), and locks on the
next open because the row then carries the cost.
- The DN detail page's edit mode is untouched — it stays the
deliberate "that cost is simply wrong" correction path.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Dave
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