waste-adjusted-yield-cost

---
name: waste-adjusted-yield-cost
description: Costs a dish on what you end up with after trim, peel and cooking loss, not the raw weight bought. It turns a purchased quantity and measured usable yield into a true cost per usable kilogram, keeping the waste percentage visible so a jump in trim loss shows before it eats the margin. Use whenever a dish uses a bulk ingredient losing weight before the plate, and to check why a real cost drifted from the recipe card.
---

# What a kilogram costs once the bit you can't serve is gone

Give this a purchased quantity and price, and the usable weight recovered after trimming, peeling, boning or cooking it. Get back the true cost per usable kilogram, the waste percentage, and a flag if it has moved against the recipe card.

## What it does

1. **Record the purchased weight and its VAT-exclusive price**, from an invoice, as dish-cost-builder does; a guessed price inherits into every dish using it.
2. **Record the usable weight recovered**, from a real trim test, not a textbook yield. WRAP put UK sector food waste at "920,000 tonnes... wasted at outlets each year", costed at "£2.5 billion per year in 2011", and a more recent figure puts edible waste at "£0.97 per restaurant cover". Trim loss on one ingredient is a small, local version of that number.
3. **Waste percentage**: (purchased weight minus usable weight) divided by purchased weight.
4. **True cost per usable kilogram**: price divided by usable weight, not purchased weight. This is the figure that belongs in a recipe cost.
5. **Compare against the recipe card's assumed yield**, if one exists, and flag any gap. A fish yielding 48% instead of a usual 55% means a different supplier, cut, or generous cutting, worth knowing before it shows as a smaller margin with no obvious cause.

## Then it checks

1. Purchased and usable weights are both real measured figures, not assumed percentages.
2. Waste percentage and cost per usable kilogram are shown as calculations.
3. Any recipe-card assumed yield is named "assumed", never confused with the measured figure.
4. A gap of over 5 points from a prior measurement or the recipe card is flagged by name.
5. The purchase price used is confirmed VAT-exclusive, consistent with dish-cost-builder.

Any check fails: redo once. Failed twice: say what is wrong and stop.

## Rules

- Public information only. Never invent a fact, number or quote, or a yield percentage; it comes from a weighed test, or isn't used.
- Anything sent in someone's name says whose name it is.
- Never state a UK-wide average as applying to one kitchen; sector figures are context, not a target.
- Never quietly replace a measured weight with an assumed one; flag the gap.
- Working document for the owner to check against their trim tests and recipe cards, and their accountant on cost of sales. Not accountancy advice.

## Built from
- WRAP, "Overview: Waste in the UK Hospitality and Food Service Sector", https://www.wrap.ngo/resources/report/overview-waste-hospitality-and-food-service-sector, published 1 November 2013, read 4 November 2026: the 920,000 tonnes/£2.5bn sector figures, step 2.
- Public Sector Catering, "WRAP calls on people to feed the bottom line, not the bin", https://www.publicsectorcatering.co.uk/in-depth/wrap-calls-people-feed-bottom-line-not-bin, published 9 February 2023, read 4 November 2026: WRAP's £0.97-per-cover figure, Eleanor Morris, step 2.

# waste-adjusted-yield-cost

## You are given
For each ingredient: purchased quantity and VAT-exclusive price (ideally from the same invoice as dish-cost-builder), the measured usable weight from an actual trim, peel, bone-out or cook test, and the test date. Where it exists, the recipe card's assumed yield percentage. Any previous yield test on file for the same ingredient and supplier.

## Produce
Write into a `./waste-adjusted-yield-cost-output/` folder:

1. `yield-tests.csv`: `ingredient_name`, `test_date`, `purchased_weight`, `purchased_unit`, `price_ex_vat`, `usable_weight`, `usable_unit`, `waste_percent`, `cost_per_usable_unit`, plus matching `_formula` columns. `waste_percent` = `(purchased_weight - usable_weight) / purchased_weight * 100`. `cost_per_usable_unit` = `price_ex_vat / usable_weight`.
2. `yield-drift.csv`: `ingredient_name`, `current_waste_percent`, `comparison_waste_percent`, `comparison_source` (`recipe card assumed yield`, `previous test on file`, `none available`), `drift_percentage_points`, `flagged` (`yes` when drift exceeds 5 points either way).
3. `gaps.md` - numbered list of: every ingredient with no comparison available; every `flagged: yes` row; any price not confirmed VAT-exclusive; any usable weight exceeding purchased weight, always an input error, never passed through silently.

## Rules
- Codex calculates, compares and flags. It never invents a yield, trim loss or usable weight not measured and supplied.
- `waste_percent` and `cost_per_usable_unit` are always shown with their formula.
- A missing comparison is recorded as `none available`, never filled in with an assumed industry figure.
- An input where usable exceeds purchased weight is listed in `gaps.md` as an input error and excluded from `yield-drift.csv` until corrected.
- Never write a UK-wide average into any ingredient's own row.
- British English, GBP, DD Month YYYY dates. No em dashes.
- Every file ends with: this is a working document prepared for the owner to check against their own weighed trim tests and recipe cards, and for their accountant where the figures feed into cost of sales. It is not accountancy advice.

## Return
The absolute path and row count of each file. For every ingredient: purchased weight, usable weight, waste percentage, and cost per usable unit, with formulas. Every flagged ingredient, with drift and comparison source. The number with no comparison available. Any input error found. The `gaps.md` item count.