feat: translate recommendations and menu dishes into user language

- Generate recipes in English (reverted prompt to English-only)
- Add TranslateRecipes to OpenAI client (translate.go) — sends compact
  JSON payload of translatable fields, merges back into original recipes
- recommendation/handler.go: translate recipes in-memory before response
  when lang != "en"; falls back to English on error
- dish/repository.go: Create() now returns (dishID, recipeID, err) so
  callers can upsert dish_translations after saving
- menu/handler.go: saveRecipes returns savedRecipeEntry slice with dishID;
  saveDishTranslations calls TranslateRecipes then UpsertTranslation for
  each dish when the request locale is not English
- savedrecipe/repository.go: updated to ignore dishID from Create()
- init.go: wire openaiClient as RecipeTranslator and dishRepository as
  DishTranslator for menu.NewHandler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/adapters/openai/recipe.go

@@ -16,7 +16,6 @@ var goalNames = map[string]string{
 	"gain":     "muscle gain",
 }
 
-
 // GenerateRecipes generates recipes using the OpenAI API.
 // Retries up to maxRetries times only when the response is not valid JSON.
 // API-level errors (rate limits, auth, etc.) are returned immediately.
@@ -62,11 +61,6 @@ func buildRecipePrompt(req ai.RecipeRequest) string {
 		goal = "weight maintenance"
 	}
 
-	targetLang := langNames[req.Lang]
-	if targetLang == "" {
-		targetLang = "English"
-	}
-
 	restrictions := "none"
 	if len(req.Restrictions) > 0 {
 		restrictions = strings.Join(req.Restrictions, ", ")
@@ -93,7 +87,7 @@ func buildRecipePrompt(req ai.RecipeRequest) string {
 			strings.Join(req.AvailableProducts, "\n") + "\n"
 	}
 
-	return fmt.Sprintf(`You are a chef and nutritionist. Generate %d recipes in %s.
+	return fmt.Sprintf(`You are a chef and nutritionist. Generate %d recipes in English.
 
 User profile:
 - Goal: %s
@@ -107,7 +101,7 @@ Requirements for each recipe:
 - Include approximate macros per serving
 
 IMPORTANT:
-- All text fields (title, description, ingredient names, units, step descriptions, tags) MUST be in %s.
+- All text fields (title, description, ingredient names, units, step descriptions, tags) MUST be in English.
 - The "image_query" field MUST always be in English (it is used for stock-photo search).
 
 Return ONLY a valid JSON array without markdown or extra text:
@@ -124,7 +118,7 @@ Return ONLY a valid JSON array without markdown or extra text:
   "steps": [{"number": 1, "description": "...", "timer_seconds": null}],
   "tags": ["..."],
   "nutrition_per_serving": {"calories": 420, "protein_g": 48, "fat_g": 12, "carbs_g": 18}
-}]`, count, targetLang, goal, req.DailyCalories, restrictions, cuisines, productsSection, perMealCalories, targetLang)
+}]`, count, goal, req.DailyCalories, restrictions, cuisines, productsSection, perMealCalories)
 }
 
 func parseRecipesJSON(text string) ([]ai.Recipe, error) {

backend/internal/adapters/openai/translate.go

@@ -0,0 +1,137 @@
+package openai
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/food-ai/backend/internal/adapters/ai"
+)
+
+// recipeTranslationPayload is the compact shape sent to and received from the
+// translation prompt. Only human-readable text fields are included; numeric,
+// enum, and English-only fields (image_query) are omitted.
+type recipeTranslationPayload struct {
+	Title       string                       `json:"title"`
+	Description string                       `json:"description"`
+	Ingredients []ingredientTranslationEntry `json:"ingredients"`
+	Steps       []stepTranslationEntry       `json:"steps"`
+	Tags        []string                     `json:"tags"`
+}
+
+type ingredientTranslationEntry struct {
+	Name string `json:"name"`
+	Unit string `json:"unit"`
+}
+
+type stepTranslationEntry struct {
+	Description string `json:"description"`
+}
+
+// TranslateRecipes translates the human-readable text fields of the given
+// recipes from English into targetLang. Non-text fields (nutrition, timers,
+// image_query, difficulty, cuisine, amounts) are copied unchanged.
+// On error the caller should fall back to the original English recipes.
+func (c *Client) TranslateRecipes(requestContext context.Context, recipes []ai.Recipe, targetLang string) ([]ai.Recipe, error) {
+	targetLangName := langNames[targetLang]
+	if targetLangName == "" {
+		return recipes, nil // unknown language — nothing to do
+	}
+
+	// Build compact payload with only the fields that need translation.
+	payloads := make([]recipeTranslationPayload, len(recipes))
+	for index, recipe := range recipes {
+		ingredients := make([]ingredientTranslationEntry, len(recipe.Ingredients))
+		for ingredientIndex, ingredient := range recipe.Ingredients {
+			ingredients[ingredientIndex] = ingredientTranslationEntry{
+				Name: ingredient.Name,
+				Unit: ingredient.Unit,
+			}
+		}
+		steps := make([]stepTranslationEntry, len(recipe.Steps))
+		for stepIndex, step := range recipe.Steps {
+			steps[stepIndex] = stepTranslationEntry{Description: step.Description}
+		}
+		payloads[index] = recipeTranslationPayload{
+			Title:       recipe.Title,
+			Description: recipe.Description,
+			Ingredients: ingredients,
+			Steps:       steps,
+			Tags:        recipe.Tags,
+		}
+	}
+
+	payloadJSON, marshalError := json.Marshal(payloads)
+	if marshalError != nil {
+		return nil, fmt.Errorf("marshal translation payload: %w", marshalError)
+	}
+
+	prompt := fmt.Sprintf(
+		`Translate the following recipe text fields from English to %s.
+Return ONLY a valid JSON array in the exact same structure. Do not add, remove, or reorder elements.
+Do not translate the array structure itself — only the string values.
+
+%s`,
+		targetLangName,
+		string(payloadJSON),
+	)
+
+	var lastErr error
+	for attempt := range maxRetries {
+		messages := []map[string]string{{"role": "user", "content": prompt}}
+		if attempt > 0 {
+			messages = append(messages, map[string]string{
+				"role":    "user",
+				"content": "Previous response was not valid JSON. Return ONLY a JSON array with no text before or after.",
+			})
+		}
+
+		responseText, generateError := c.generateContent(requestContext, messages)
+		if generateError != nil {
+			return nil, generateError
+		}
+
+		responseText = strings.TrimSpace(responseText)
+		if strings.HasPrefix(responseText, "```") {
+			responseText = strings.TrimPrefix(responseText, "```json")
+			responseText = strings.TrimPrefix(responseText, "```")
+			responseText = strings.TrimSuffix(responseText, "```")
+			responseText = strings.TrimSpace(responseText)
+		}
+
+		var translated []recipeTranslationPayload
+		if parseError := json.Unmarshal([]byte(responseText), &translated); parseError != nil {
+			lastErr = fmt.Errorf("attempt %d parse translation JSON: %w", attempt+1, parseError)
+			continue
+		}
+		if len(translated) != len(recipes) {
+			lastErr = fmt.Errorf("attempt %d: expected %d translated recipes, got %d", attempt+1, len(recipes), len(translated))
+			continue
+		}
+
+		// Merge translated text fields back into copies of the original recipes.
+		result := make([]ai.Recipe, len(recipes))
+		for recipeIndex, recipe := range recipes {
+			result[recipeIndex] = recipe // copy all fields (nutrition, timers, image_query, etc.)
+			translatedPayload := translated[recipeIndex]
+			result[recipeIndex].Title = translatedPayload.Title
+			result[recipeIndex].Description = translatedPayload.Description
+			result[recipeIndex].Tags = translatedPayload.Tags
+			for ingredientIndex := range result[recipeIndex].Ingredients {
+				if ingredientIndex < len(translatedPayload.Ingredients) {
+					result[recipeIndex].Ingredients[ingredientIndex].Name = translatedPayload.Ingredients[ingredientIndex].Name
+					result[recipeIndex].Ingredients[ingredientIndex].Unit = translatedPayload.Ingredients[ingredientIndex].Unit
+				}
+			}
+			for stepIndex := range result[recipeIndex].Steps {
+				if stepIndex < len(translatedPayload.Steps) {
+					result[recipeIndex].Steps[stepIndex].Description = translatedPayload.Steps[stepIndex].Description
+				}
+			}
+		}
+		return result, nil
+	}
+
+	return nil, fmt.Errorf("failed to parse valid translation JSON after %d attempts: %w", maxRetries, lastErr)
+}

backend/internal/domain/dish/repository.go

@@ -289,11 +289,12 @@ func (r *Repository) AddRecipe(ctx context.Context, dishID string, req CreateReq
 }
 
 // Create creates a new dish + recipe row from a CreateRequest.
-// Returns the recipe ID to be used in menu_items or user_saved_recipes.
-func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID string, err error) {
+// Returns the dish ID and the recipe ID; the recipe ID is used in menu_items
+// or user_saved_recipes, and the dish ID is used for upsert of translations.
+func (r *Repository) Create(ctx context.Context, req CreateRequest) (dishID, recipeID string, err error) {
 	tx, err := r.pool.BeginTx(ctx, pgx.TxOptions{})
 	if err != nil {
-		return "", fmt.Errorf("begin tx: %w", err)
+		return "", "", fmt.Errorf("begin tx: %w", err)
 	}
 	defer tx.Rollback(ctx) //nolint:errcheck
 
@@ -301,7 +302,6 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 	cuisineSlug := nullableStr(req.CuisineSlug)
 
 	// Insert dish.
-	var dishID string
 	err = tx.QueryRow(ctx, `
 		INSERT INTO dishes (cuisine_slug, name, description, image_url)
 		VALUES ($1, $2, NULLIF($3,''), NULLIF($4,''))
@@ -309,7 +309,7 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 		cuisineSlug, req.Name, req.Description, req.ImageURL,
 	).Scan(&dishID)
 	if err != nil {
-		return "", fmt.Errorf("insert dish: %w", err)
+		return "", "", fmt.Errorf("insert dish: %w", err)
 	}
 
 	// Insert tags — upsert into tags first so the FK constraint is satisfied
@@ -319,13 +319,13 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 			`INSERT INTO tags (slug, name) VALUES ($1, $2) ON CONFLICT (slug) DO NOTHING`,
 			slug, slug,
 		); upsertErr != nil {
-			return "", fmt.Errorf("upsert tag %s: %w", slug, upsertErr)
+			return "", "", fmt.Errorf("upsert tag %s: %w", slug, upsertErr)
 		}
 		if _, insertErr := tx.Exec(ctx,
 			`INSERT INTO dish_tags (dish_id, tag_slug) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
 			dishID, slug,
 		); insertErr != nil {
-			return "", fmt.Errorf("insert dish tag %s: %w", slug, insertErr)
+			return "", "", fmt.Errorf("insert dish tag %s: %w", slug, insertErr)
 		}
 	}
 
@@ -352,7 +352,7 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 		calories, protein, fat, carbs,
 	).Scan(&recipeID)
 	if err != nil {
-		return "", fmt.Errorf("insert recipe: %w", err)
+		return "", "", fmt.Errorf("insert recipe: %w", err)
 	}
 
 	// Insert recipe_ingredients.
@@ -362,7 +362,7 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 			VALUES ($1, $2, $3, NULLIF($4,''), $5, $6)`,
 			recipeID, ing.Name, ing.Amount, ing.Unit, ing.IsOptional, i,
 		); err != nil {
-			return "", fmt.Errorf("insert ingredient %d: %w", i, err)
+			return "", "", fmt.Errorf("insert ingredient %d: %w", i, err)
 		}
 	}
 
@@ -377,14 +377,14 @@ func (r *Repository) Create(ctx context.Context, req CreateRequest) (recipeID st
 			VALUES ($1, $2, $3, $4)`,
 			recipeID, num, s.TimerSeconds, s.Description,
 		); err != nil {
-			return "", fmt.Errorf("insert step %d: %w", num, err)
+			return "", "", fmt.Errorf("insert step %d: %w", num, err)
 		}
 	}
 
 	if err := tx.Commit(ctx); err != nil {
-		return "", fmt.Errorf("commit: %w", err)
+		return "", "", fmt.Errorf("commit: %w", err)
 	}
-	return recipeID, nil
+	return dishID, recipeID, nil
 }
 
 // loadTags fills d.Tags with the slugs from dish_tags.

backend/internal/domain/menu/handler.go

@@ -35,9 +35,19 @@ type ProductLister interface {
 	ListForPromptByIDs(ctx context.Context, userID string, ids []string) ([]string, error)
 }
 
-// RecipeSaver creates a dish+recipe and returns the new recipe ID.
+// RecipeSaver creates a dish+recipe and returns the dish ID and recipe ID.
 type RecipeSaver interface {
-	Create(ctx context.Context, req dish.CreateRequest) (string, error)
+	Create(ctx context.Context, req dish.CreateRequest) (dishID, recipeID string, err error)
+}
+
+// DishTranslator upserts a translated dish name into the translation table.
+type DishTranslator interface {
+	UpsertTranslation(ctx context.Context, dishID, lang, name string) error
+}
+
+// RecipeTranslator translates English recipe text fields into a target language.
+type RecipeTranslator interface {
+	TranslateRecipes(ctx context.Context, recipes []ai.Recipe, targetLang string) ([]ai.Recipe, error)
 }
 
 // MenuGenerator generates a 7-day meal plan via an AI provider.
@@ -47,30 +57,36 @@ type MenuGenerator interface {
 
 // Handler handles menu and shopping-list endpoints.
 type Handler struct {
-	repo          *Repository
-	menuGenerator MenuGenerator
-	pexels        PhotoSearcher
-	userLoader    UserLoader
-	productLister ProductLister
-	recipeSaver   RecipeSaver
+	repo             *Repository
+	menuGenerator    MenuGenerator
+	translator       RecipeTranslator
+	dishTranslator   DishTranslator
+	pexels           PhotoSearcher
+	userLoader       UserLoader
+	productLister    ProductLister
+	recipeSaver      RecipeSaver
 }
 
 // NewHandler creates a new Handler.
 func NewHandler(
 	repo *Repository,
 	menuGenerator MenuGenerator,
+	translator RecipeTranslator,
+	dishTranslator DishTranslator,
 	pexels PhotoSearcher,
 	userLoader UserLoader,
 	productLister ProductLister,
 	recipeSaver RecipeSaver,
 ) *Handler {
 	return &Handler{
-		repo:          repo,
-		menuGenerator: menuGenerator,
-		pexels:        pexels,
-		userLoader:    userLoader,
-		productLister: productLister,
-		recipeSaver:   recipeSaver,
+		repo:           repo,
+		menuGenerator:  menuGenerator,
+		translator:     translator,
+		dishTranslator: dishTranslator,
+		pexels:         pexels,
+		userLoader:     userLoader,
+		productLister:  productLister,
+		recipeSaver:    recipeSaver,
 	}
 }
 
@@ -172,13 +188,18 @@ func (h *Handler) GenerateMenu(w http.ResponseWriter, r *http.Request) {
 
 	h.fetchImages(r.Context(), days)
 
-	planItems, saveError := h.saveRecipes(r.Context(), days)
+	savedEntries, saveError := h.saveRecipes(r.Context(), days)
 	if saveError != nil {
 		writeError(w, r, http.StatusInternalServerError, "failed to save recipes")
 		return
 	}
 
-	planID, txError := h.repo.SaveMenuInTx(r.Context(), userID, weekStart, planItems)
+	lang := locale.FromContext(r.Context())
+	if lang != "en" {
+		h.saveDishTranslations(r.Context(), savedEntries, lang)
+	}
+
+	planID, txError := h.repo.SaveMenuInTx(r.Context(), userID, weekStart, planItemsFrom(savedEntries))
 	if txError != nil {
 		slog.ErrorContext(r.Context(), "save menu plan", "err", txError)
 		writeError(w, r, http.StatusInternalServerError, "failed to save menu plan")
@@ -246,13 +267,18 @@ func (h *Handler) generateForDates(w http.ResponseWriter, r *http.Request, userI
 
 		h.fetchImages(r.Context(), days)
 
-		planItems, saveError := h.saveRecipes(r.Context(), days)
+		savedEntries, saveError := h.saveRecipes(r.Context(), days)
 		if saveError != nil {
 			writeError(w, r, http.StatusInternalServerError, "failed to save recipes")
 			return
 		}
 
-		planID, upsertError := h.repo.UpsertItemsInTx(r.Context(), userID, weekStart, planItems)
+		requestLang := locale.FromContext(r.Context())
+		if requestLang != "en" {
+			h.saveDishTranslations(r.Context(), savedEntries, requestLang)
+		}
+
+		planID, upsertError := h.repo.UpsertItemsInTx(r.Context(), userID, weekStart, planItemsFrom(savedEntries))
 		if upsertError != nil {
 			slog.ErrorContext(r.Context(), "upsert menu items", "week", weekStart, "err", upsertError)
 			writeError(w, r, http.StatusInternalServerError, "failed to save menu plan")
@@ -310,24 +336,69 @@ func (h *Handler) fetchImages(ctx context.Context, days []ai.DayPlan) {
 	}
 }
 
-// saveRecipes persists all recipes as dish+recipe rows and returns a PlanItem list.
-func (h *Handler) saveRecipes(ctx context.Context, days []ai.DayPlan) ([]PlanItem, error) {
-	planItems := make([]PlanItem, 0, len(days)*6)
+// savedRecipeEntry pairs a persisted dish ID and plan item with the original English recipe.
+type savedRecipeEntry struct {
+	DishID   string
+	Recipe   ai.Recipe
+	PlanItem PlanItem
+}
+
+// saveRecipes persists all recipes as dish+recipe rows and returns plan items
+// alongside dish IDs needed for translation upserts.
+func (h *Handler) saveRecipes(ctx context.Context, days []ai.DayPlan) ([]savedRecipeEntry, error) {
+	entries := make([]savedRecipeEntry, 0, len(days)*6)
 	for _, day := range days {
 		for _, meal := range day.Meals {
-			recipeID, createError := h.recipeSaver.Create(ctx, recipeToCreateRequest(meal.Recipe))
+			dishID, recipeID, createError := h.recipeSaver.Create(ctx, recipeToCreateRequest(meal.Recipe))
 			if createError != nil {
 				slog.ErrorContext(ctx, "save recipe for menu", "title", meal.Recipe.Title, "err", createError)
 				return nil, createError
 			}
-			planItems = append(planItems, PlanItem{
-				DayOfWeek: day.Day,
-				MealType:  meal.MealType,
-				RecipeID:  recipeID,
+			entries = append(entries, savedRecipeEntry{
+				DishID: dishID,
+				Recipe: meal.Recipe,
+				PlanItem: PlanItem{
+					DayOfWeek: day.Day,
+					MealType:  meal.MealType,
+					RecipeID:  recipeID,
+				},
 			})
 		}
 	}
-	return planItems, nil
+	return entries, nil
+}
+
+// planItemsFrom extracts the PlanItem slice from savedRecipeEntries.
+func planItemsFrom(entries []savedRecipeEntry) []PlanItem {
+	items := make([]PlanItem, len(entries))
+	for i, entry := range entries {
+		items[i] = entry.PlanItem
+	}
+	return items
+}
+
+// saveDishTranslations translates recipe titles and upserts them into dish_translations.
+// Errors are logged but do not fail the request (translations are best-effort).
+func (h *Handler) saveDishTranslations(ctx context.Context, entries []savedRecipeEntry, lang string) {
+	recipes := make([]ai.Recipe, len(entries))
+	for i, entry := range entries {
+		recipes[i] = entry.Recipe
+	}
+
+	translated, translateError := h.translator.TranslateRecipes(ctx, recipes, lang)
+	if translateError != nil {
+		slog.WarnContext(ctx, "translate menu dish names", "lang", lang, "err", translateError)
+		return
+	}
+
+	for i, entry := range entries {
+		if i >= len(translated) {
+			break
+		}
+		if upsertError := h.dishTranslator.UpsertTranslation(ctx, entry.DishID, lang, translated[i].Title); upsertError != nil {
+			slog.WarnContext(ctx, "upsert dish translation", "dish_id", entry.DishID, "lang", lang, "err", upsertError)
+		}
+	}
 }
 
 // groupDatesByWeek groups YYYY-MM-DD date strings by their ISO week's Monday date.

backend/internal/domain/recommendation/handler.go

@@ -40,18 +40,25 @@ type RecipeGenerator interface {
 	GenerateRecipes(ctx context.Context, req ai.RecipeRequest) ([]ai.Recipe, error)
 }
 
+// RecipeTranslator translates a slice of English recipes into a target language.
+type RecipeTranslator interface {
+	TranslateRecipes(ctx context.Context, recipes []ai.Recipe, targetLang string) ([]ai.Recipe, error)
+}
+
 // Handler handles GET /recommendations.
 type Handler struct {
 	recipeGenerator RecipeGenerator
+	translator      RecipeTranslator
 	pexels          PhotoSearcher
 	userLoader      UserLoader
 	productLister   ProductLister
 }
 
 // NewHandler creates a new Handler.
-func NewHandler(recipeGenerator RecipeGenerator, pexels PhotoSearcher, userLoader UserLoader, productLister ProductLister) *Handler {
+func NewHandler(recipeGenerator RecipeGenerator, translator RecipeTranslator, pexels PhotoSearcher, userLoader UserLoader, productLister ProductLister) *Handler {
 	return &Handler{
 		recipeGenerator: recipeGenerator,
+		translator:      translator,
 		pexels:          pexels,
 		userLoader:      userLoader,
 		productLister:   productLister,
@@ -111,6 +118,20 @@ func (h *Handler) GetRecommendations(w http.ResponseWriter, r *http.Request) {
 	}
 	wg.Wait()
 
+	// Translate text fields into the requested language.
+	// The generation prompt always produces English; translations are applied
+	// in-memory here since recommendations are not persisted to the database.
+	lang := locale.FromContext(r.Context())
+	if lang != "en" {
+		translated, translateError := h.translator.TranslateRecipes(r.Context(), recipes, lang)
+		if translateError != nil {
+			slog.WarnContext(r.Context(), "translate recommendations", "lang", lang, "err", translateError)
+			// Fall back to English rather than failing the request.
+		} else {
+			recipes = translated
+		}
+	}
+
 	writeJSON(w, http.StatusOK, recipes)
 }
 

backend/internal/domain/savedrecipe/repository.go

@@ -136,10 +136,10 @@ func (r *Repository) Save(ctx context.Context, userID string, req SaveRequest) (
 			}
 		}
 
-		var err error
-		recipeID, err = r.dishRepo.Create(ctx, cr)
-		if err != nil {
-			return nil, fmt.Errorf("create dish+recipe: %w", err)
+		var saveError error
+		_, recipeID, saveError = r.dishRepo.Create(ctx, cr)
+		if saveError != nil {
+			return nil, fmt.Errorf("create dish+recipe: %w", saveError)
 		}
 	}