fix: avoid rounding for liquid/gas ingredients

Author: rockfactory

src/codex/items/CodexItemDetail.tsx

@@ -227,7 +227,12 @@ function RecipeTable({
           const baseAmount = relevantPart ? relevantPart.amount : 0;
           const effectiveAmount =
             type === 'ingredient' && relevantPart
-              ? applyRecipeMultiplier(baseAmount, recipeMultiplier, recipe)
+              ? applyRecipeMultiplier(
+                  baseAmount,
+                  recipeMultiplier,
+                  recipe,
+                  AllFactoryItemsMap[highlightResource]?.form,
+                )
               : baseAmount;
           const rate = relevantPart ? (effectiveAmount * 60) / recipe.time : 0;
 

src/codex/recipes/CodexRecipeDetail.tsx

@@ -154,11 +154,13 @@ export function CodexRecipeDetail() {
                   ing.amount,
                   recipeMultiplier,
                   recipe,
+                  item?.form,
                 );
                 const effectiveDisplayAmount = applyRecipeMultiplier(
                   ing.displayAmount,
                   recipeMultiplier,
                   recipe,
+                  item?.form,
                 );
                 const rate = (effectiveAmount * 60) / recipe.time;
                 const isModified = effectiveDisplayAmount !== ing.displayAmount;

src/recipes/recipeMultiplier.ts

@@ -1,13 +1,28 @@
 const PACKAGER_BUILDING_ID = 'Build_Packager_C';
 
+/**
+ * Applies the Satisfactory 1.2 "Recipe Parts Cost Multiplier" to a
+ * single ingredient amount. Three rules govern the result:
+ *
+ * 1. Packager recipes are exempt: the game never scales packaging or
+ *    unpackaging ingredients regardless of the multiplier.
+ * 2. Fluids and gases are scaled without rounding (e.g. 3 * 0.25 = 0.75 m3),
+ *    because fractional fluid amounts are valid in-game.
+ * 3. Solids are rounded to the nearest integer with a floor of 1, because
+ *    handcrafting requires whole items and zero-cost ingredients would break
+ *    recipes (e.g. 1 * 0.25 = 0.25, rounded to 0, floored to 1).
+ */
 export function applyRecipeMultiplier(
   baseAmount: number,
   multiplier: number,
   recipe?: { producedIn: string },
+  itemForm?: string,
 ): number {
   if (multiplier === 1) return baseAmount;
   if (recipe?.producedIn === PACKAGER_BUILDING_ID) return baseAmount;
-  return Math.max(1, Math.round(baseAmount * multiplier));
+  const scaled = baseAmount * multiplier;
+  if (itemForm === 'Liquid' || itemForm === 'Gas') return scaled;
+  return Math.max(1, Math.round(scaled));
 }
 
 export function isPackagerRecipe(recipe: { producedIn: string }): boolean {

src/recipes/ui/RecipeTooltip.tsx

@@ -46,6 +46,7 @@ export function RecipeTooltip(props: IRecipeTooltipProps) {
                         ingredient.displayAmount,
                         recipeMultiplier,
                         recipe,
+                        AllFactoryItemsMap[ingredient.resource].form,
                       ) *
                         60) /
                       recipe.time

src/solver/algorithm/compute/computeProductionConstraints.tsx

@@ -192,6 +192,7 @@ export function computeProductionConstraints(
           ingredient.amount,
           ctx.request.recipeMultiplier ?? 1,
           recipe,
+          ingredientItem.form,
         );
         const ingredientAmount = (multipliedAmount * 60) / recipe.time;
         const factor = productAmount / ingredientAmount;

src/solver/layout/nodes/machine-node/RecipeIngredientRow.tsx

@@ -36,6 +36,7 @@ export const RecipeIngredientRow = ({
           ingredient.displayAmount,
           recipeMultiplier,
           recipe,
+          item.form,
         )
       : ingredient.displayAmount;
   const baseRate = (effectiveAmount * 60) / recipe.time;