recipe-scaler

---
name: recipe-scaler
description: Scales a recipe from one portion count to another, every ingredient by the same ratio, showing the arithmetic so a wrong scale is caught before it reaches the kitchen. It keeps non-scaling items, a pinch, a garnish, a bay leaf, out of the ratio and flags them for a human decision instead of multiplying nonsense. Use whenever a recipe is batch-cooked at a different size, for a function, or to test a new portion size.
---

# Scaling a recipe without breaking what made it work

Give this a recipe at its original yield and the new yield needed. Get back every ingredient scaled by the same ratio, the ratio shown, and a list of lines the scale couldn't safely apply to on its own.

## What it does

1. **Work out the scaling ratio**: new portions divided by original, as a fraction and a decimal (50 from 12 is 50/12, 4.17). No ratio shown means nobody can check it.
2. **Apply the ratio to every quantified line**, converting to a sensible unit (grams not a gram fraction, whole eggs unless the recipe genuinely divides).
3. **Set aside anything that can't scale by simple multiplication**: a pinch, "to taste", a whole spice meant as one regardless of yield, or anything crossing a different pack size or method at scale. Listed for a human decision, never silently multiplied.
4. **Flag that scaling changes a declared quantity.** Quantity is a "main characteristic" a business must not misdescribe under the Consumer Protection from Unfair Trading Regulations 2008; a dish later described by weight ("200g steak") must still deliver it.
5. **Never touch an allergen.** Scaling changes quantity, not content; a matrix built for the original yield still applies, unless an ingredient is substituted at scale, which triggers its own fresh check.

## Then it checks

1. The ratio shown matches new yield divided by original, recalculated independently.
2. Every scaled figure divided by its original equals the ratio, within rounding shown.
3. Every set-aside line is listed with its reason, not silently dropped.
4. No ingredient name or type changed during scaling; only quantities moved.
5. The scaled recipe states the same allergens as the original, unless a substitution was separately flagged.

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

## Rules

- Public information only. Never invent a fact, number or quote, or a pack size, conversion or substitution not in the recipe.
- Anything sent in someone's name says whose name it is.
- Never multiply a "to taste", single spice, or garnish line automatically; list it for a human decision.
- Never claim allergen-equivalence without checking no ingredient was substituted during scaling.
- Working document for the owner to check against their recipe and kitchen practice, and a food safety adviser where method or holding time changes. Not food safety advice.

## Built from
- Consumer Protection from Unfair Trading Regulations 2008, regulation 5, https://www.legislation.gov.uk/uksi/2008/1277/made, SI 2008/1277, read 4 November 2026: lists "quantity of the product" among "main characteristics" in 5(5), used in step 4.
- Food Standards Agency, "Allergen guidance for food businesses", https://www.gov.uk/government/publications/allergen-guidance-for-food-businesses/allergen-guidance-for-food-businesses, published 2 April 2020, updated 17 July 2026, read 4 November 2026: confirms allergen info covers actual ingredients present, used in step 5.

# recipe-scaler

## You are given
A recipe at its original yield (portions) with one row per ingredient, quantity and unit. The new target yield. Any pack-size constraints already known (e.g. eggs only scale in whole units). Any note that an ingredient will be substituted at the new scale, separate from the scaling request itself.

## Produce
Write into a `./recipe-scaler-output/` folder:

1. `scaled-recipe.csv`: `row_ref`, `ingredient_name`, `original_quantity`, `original_unit`, `scaled_quantity`, `scaled_unit`, `ratio_applied`, `scaling_method`. `row_ref` is R0001 upward. `ratio_applied` is the fraction used, e.g. `50/12`. `scaling_method` is `direct multiplication`, `rounded to whole unit`, or `set aside, not scaled`.
2. `set-aside.csv`: `row_ref`, `ingredient_name`, `original_quantity`, `original_unit`, `reason_not_scaled` (`to taste`, `single whole item intended regardless of yield`, `pack size would not divide cleanly`, `method changes at this scale`, `other, see note`).
3. `ratio-check.csv`: `row_ref`, `ingredient_name`, `expected_ratio`, `actual_ratio_from_scaled_figures`, `match` (`yes`/`no`), recalculated independently for every scaled/rounded row.
4. `allergen-carryover.csv`: `ingredient_name`, `substituted_at_scale` (`yes`/`no`), `substitution_detail`, `allergen_recheck_required` (`yes` whenever substituted).
5. `gaps.md` - numbered list of: every `no` in `ratio-check.csv`; every row in `set-aside.csv`; every `yes` in `allergen_recheck_required`; any ingredient with no unit supplied.

## Rules
- Codex multiplies, converts and checks. It never decides a "to taste" or single-item line should be scaled, and never invents a pack size or substitution not supplied.
- The ratio is always shown as the fraction used, never only a decimal.
- A row is only marked scaled if the ratio check passes; a failed row is corrected once, and if it still fails, left with `match` set to `no` rather than forced to pass.
- Never mark `allergen_recheck_required` as `no` for a flagged substitution; the flag always carries through.
- 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 recipe and kitchen practice, and for a food safety adviser to check where a scaled batch changes cooking method or holding time. It is not food safety advice.

## Return
The absolute path and row count of each file. The ratio used, as fraction and decimal. Rows scaled directly, rounded, and set aside, each reason counted. `ratio-check.csv` result for every row, including any mismatch. Ingredients flagged for an allergen recheck. The `gaps.md` item count.