feat(translation): machine translation pipeline + admin bulk enqueue UI

- LibreTranslate client (chunks on blank lines, ≤4500 chars, 3-goroutine semaphore)
- Runner translation task loop (OTel, heartbeat, MinIO storage)
- PocketBase translation_jobs collection support (create/claim/finish/list)
- Per-chapter language switcher on chapter reader (EN/RU/ID/PT/FR, polls until done)
- Admin /admin/translation page: bulk enqueue form + live-polling jobs table
- New backend routes: POST /api/translation/{slug}/{n}, GET /api/translation/status,
  GET /api/translation/{slug}/{n}, GET /api/admin/translation/jobs,
  POST /api/admin/translation/bulk
- ListTranslationTasks added to taskqueue.Reader interface + store impl
- All builds and tests pass; svelte-check: 0 errors

backend/internal/asynqqueue/consumer.go

@@ -37,6 +37,10 @@ func (c *Consumer) FinishAudioTask(ctx context.Context, id string, result domain
 	return c.pb.FinishAudioTask(ctx, id, result)
 }
 
+func (c *Consumer) FinishTranslationTask(ctx context.Context, id string, result domain.TranslationResult) error {
+	return c.pb.FinishTranslationTask(ctx, id, result)
+}
+
 func (c *Consumer) FailTask(ctx context.Context, id, errMsg string) error {
 	return c.pb.FailTask(ctx, id, errMsg)
 }
@@ -51,6 +55,10 @@ func (c *Consumer) ClaimNextAudioTask(_ context.Context, _ string) (domain.Audio
 	return domain.AudioTask{}, false, nil
 }
 
+func (c *Consumer) ClaimNextTranslationTask(_ context.Context, _ string) (domain.TranslationTask, bool, error) {
+	return domain.TranslationTask{}, false, nil
+}
+
 func (c *Consumer) HeartbeatTask(_ context.Context, _ string) error { return nil }
 
 func (c *Consumer) ReapStaleTasks(_ context.Context, _ time.Duration) (int, error) { return 0, nil }

backend/internal/asynqqueue/producer.go

@@ -73,6 +73,12 @@ func (p *Producer) CreateAudioTask(ctx context.Context, slug string, chapter int
 	return id, nil
 }
 
+// CreateTranslationTask creates a PocketBase record. Translation tasks are
+// not currently dispatched via Asynq — the runner picks them up via polling.
+func (p *Producer) CreateTranslationTask(ctx context.Context, slug string, chapter int, lang string) (string, error) {
+	return p.pb.CreateTranslationTask(ctx, slug, chapter, lang)
+}
+
 // CancelTask delegates to PocketBase; Asynq jobs may already be running and
 // cannot be reliably cancelled, so we only update the audit record.
 func (p *Producer) CancelTask(ctx context.Context, id string) error {

backend/internal/backend/handlers.go

@@ -32,6 +32,7 @@ package backend
 //     directly (no runner task, no store writes). Used for unscraped books.
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -49,6 +50,7 @@ import (
 	"github.com/libnovel/backend/internal/novelfire/htmlutil"
 	"github.com/libnovel/backend/internal/pockettts"
 	"github.com/libnovel/backend/internal/scraper"
+	"github.com/yuin/goldmark"
 )
 
 const (
@@ -701,9 +703,252 @@ func (s *Server) handleAudioProxy(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, presignURL, http.StatusFound)
 }
 
-// ── Voices ─────────────────────────────────────────────────────────────────────
+// ── Translation ────────────────────────────────────────────────────────────────
 
-// handleVoices handles GET /api/voices.
+// supportedTranslationLangs is the set of target locales the backend accepts.
+// Source is always "en".
+var supportedTranslationLangs = map[string]bool{
+	"ru": true, "id": true, "pt": true, "fr": true,
+}
+
+// handleTranslationGenerate handles POST /api/translation/{slug}/{n}.
+// Query params: lang (required, one of ru|id|pt|fr)
+//
+// Returns 200 immediately if translation already exists in MinIO.
+// Returns 202 with task_id if a new task was created.
+// Returns 503 if TranslationStore is nil (feature disabled).
+func (s *Server) handleTranslationGenerate(w http.ResponseWriter, r *http.Request) {
+	if s.deps.TranslationStore == nil {
+		jsonError(w, http.StatusServiceUnavailable, "machine translation not configured")
+		return
+	}
+
+	slug := r.PathValue("slug")
+	n, err := strconv.Atoi(r.PathValue("n"))
+	if err != nil || n < 1 {
+		jsonError(w, http.StatusBadRequest, "invalid chapter")
+		return
+	}
+
+	lang := r.URL.Query().Get("lang")
+	if !supportedTranslationLangs[lang] {
+		jsonError(w, http.StatusBadRequest, "unsupported lang; use ru, id, pt, or fr")
+		return
+	}
+
+	cacheKey := fmt.Sprintf("%s/%d/%s", slug, n, lang)
+
+	// Fast path: translation already in MinIO
+	key := s.deps.TranslationStore.TranslationObjectKey(lang, slug, n)
+	if s.deps.TranslationStore.TranslationExists(r.Context(), key) {
+		writeJSON(w, 0, map[string]string{"status": "done", "lang": lang})
+		return
+	}
+
+	// Check if a task is already pending/running
+	task, found, _ := s.deps.TaskReader.GetTranslationTask(r.Context(), cacheKey)
+	if found && (task.Status == domain.TaskStatusPending || task.Status == domain.TaskStatusRunning) {
+		writeJSON(w, http.StatusAccepted, map[string]string{
+			"task_id": task.ID,
+			"status":  string(task.Status),
+			"lang":    lang,
+		})
+		return
+	}
+
+	// Create a new translation task
+	taskID, err := s.deps.Producer.CreateTranslationTask(r.Context(), slug, n, lang)
+	if err != nil {
+		s.deps.Log.Error("handleTranslationGenerate: CreateTranslationTask failed", "err", err)
+		jsonError(w, http.StatusInternalServerError, "failed to create translation task")
+		return
+	}
+
+	writeJSON(w, http.StatusAccepted, map[string]string{
+		"task_id": taskID,
+		"status":  "pending",
+		"lang":    lang,
+	})
+}
+
+// handleTranslationStatus handles GET /api/translation/status/{slug}/{n}.
+// Query params: lang (required)
+func (s *Server) handleTranslationStatus(w http.ResponseWriter, r *http.Request) {
+	if s.deps.TranslationStore == nil {
+		writeJSON(w, 0, map[string]string{"status": "unavailable"})
+		return
+	}
+
+	slug := r.PathValue("slug")
+	n, err := strconv.Atoi(r.PathValue("n"))
+	if err != nil || n < 1 || slug == "" {
+		jsonError(w, http.StatusBadRequest, "invalid params")
+		return
+	}
+
+	lang := r.URL.Query().Get("lang")
+	if !supportedTranslationLangs[lang] {
+		jsonError(w, http.StatusBadRequest, "unsupported lang")
+		return
+	}
+
+	// Fast path: translation exists in MinIO
+	key := s.deps.TranslationStore.TranslationObjectKey(lang, slug, n)
+	if s.deps.TranslationStore.TranslationExists(r.Context(), key) {
+		writeJSON(w, 0, map[string]string{"status": "done", "lang": lang})
+		return
+	}
+
+	cacheKey := fmt.Sprintf("%s/%d/%s", slug, n, lang)
+	task, found, _ := s.deps.TaskReader.GetTranslationTask(r.Context(), cacheKey)
+	if !found {
+		writeJSON(w, 0, map[string]string{"status": "idle", "lang": lang})
+		return
+	}
+
+	resp := map[string]string{
+		"status":  string(task.Status),
+		"task_id": task.ID,
+		"lang":    lang,
+	}
+	if task.Status == domain.TaskStatusFailed && task.ErrorMessage != "" {
+		resp["error"] = task.ErrorMessage
+	}
+	writeJSON(w, 0, resp)
+}
+
+// handleTranslationRead handles GET /api/translation/{slug}/{n}.
+// Query params: lang (required)
+//
+// Returns {"html": "<p>...</p>", "lang": "ru"} from the MinIO-cached translation.
+// Returns 404 when the translation has not been generated yet.
+func (s *Server) handleTranslationRead(w http.ResponseWriter, r *http.Request) {
+	if s.deps.TranslationStore == nil {
+		http.Error(w, `{"error":"machine translation not configured"}`, http.StatusServiceUnavailable)
+		return
+	}
+
+	slug := r.PathValue("slug")
+	n, err := strconv.Atoi(r.PathValue("n"))
+	if err != nil || n < 1 || slug == "" {
+		jsonError(w, http.StatusBadRequest, "invalid params")
+		return
+	}
+
+	lang := r.URL.Query().Get("lang")
+	if !supportedTranslationLangs[lang] {
+		jsonError(w, http.StatusBadRequest, "unsupported lang")
+		return
+	}
+
+	key := s.deps.TranslationStore.TranslationObjectKey(lang, slug, n)
+	md, err := s.deps.TranslationStore.GetTranslation(r.Context(), key)
+	if err != nil {
+		s.deps.Log.Warn("handleTranslationRead: translation not found", "slug", slug, "n", n, "lang", lang, "err", err)
+		jsonError(w, http.StatusNotFound, "translation not available")
+		return
+	}
+
+	var buf bytes.Buffer
+	if err := goldmark.Convert([]byte(md), &buf); err != nil {
+		s.deps.Log.Error("handleTranslationRead: markdown conversion failed", "err", err)
+		jsonError(w, http.StatusInternalServerError, "failed to render translation")
+		return
+	}
+
+	writeJSON(w, 0, map[string]string{"html": buf.String(), "lang": lang})
+}
+
+// handleAdminTranslationJobs handles GET /api/admin/translation/jobs.
+// Returns the full list of translation jobs sorted by started descending.
+func (s *Server) handleAdminTranslationJobs(w http.ResponseWriter, r *http.Request) {
+	tasks, err := s.deps.TaskReader.ListTranslationTasks(r.Context())
+	if err != nil {
+		s.deps.Log.Error("handleAdminTranslationJobs: ListTranslationTasks failed", "err", err)
+		jsonError(w, http.StatusInternalServerError, "failed to list translation jobs")
+		return
+	}
+	type jobRow struct {
+		ID           string `json:"id"`
+		CacheKey     string `json:"cache_key"`
+		Slug         string `json:"slug"`
+		Chapter      int    `json:"chapter"`
+		Lang         string `json:"lang"`
+		Status       string `json:"status"`
+		WorkerID     string `json:"worker_id"`
+		ErrorMessage string `json:"error_message"`
+		Started      string `json:"started"`
+		Finished     string `json:"finished"`
+	}
+	rows := make([]jobRow, 0, len(tasks))
+	for _, t := range tasks {
+		rows = append(rows, jobRow{
+			ID:           t.ID,
+			CacheKey:     t.CacheKey,
+			Slug:         t.Slug,
+			Chapter:      t.Chapter,
+			Lang:         t.Lang,
+			Status:       string(t.Status),
+			WorkerID:     t.WorkerID,
+			ErrorMessage: t.ErrorMessage,
+			Started:      t.Started.Format(time.RFC3339),
+			Finished:     t.Finished.Format(time.RFC3339),
+		})
+	}
+	writeJSON(w, 0, map[string]any{"jobs": rows})
+}
+
+// handleAdminTranslationBulk handles POST /api/admin/translation/bulk.
+// Body: {"slug": "...", "lang": "ru", "from": 1, "to": 50}
+// Enqueues one translation task per chapter in the range [from, to] inclusive.
+func (s *Server) handleAdminTranslationBulk(w http.ResponseWriter, r *http.Request) {
+	var body struct {
+		Slug string `json:"slug"`
+		Lang string `json:"lang"`
+		From int    `json:"from"`
+		To   int    `json:"to"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		jsonError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+	if body.Slug == "" {
+		jsonError(w, http.StatusBadRequest, "slug is required")
+		return
+	}
+	if !supportedTranslationLangs[body.Lang] {
+		jsonError(w, http.StatusBadRequest, "unsupported lang; use ru, id, pt, or fr")
+		return
+	}
+	if body.From < 1 || body.To < body.From {
+		jsonError(w, http.StatusBadRequest, "from must be >= 1 and to must be >= from")
+		return
+	}
+	if body.To-body.From > 999 {
+		jsonError(w, http.StatusBadRequest, "range too large; max 1000 chapters per request")
+		return
+	}
+
+	var taskIDs []string
+	for n := body.From; n <= body.To; n++ {
+		id, err := s.deps.Producer.CreateTranslationTask(r.Context(), body.Slug, n, body.Lang)
+		if err != nil {
+			s.deps.Log.Error("handleAdminTranslationBulk: CreateTranslationTask failed",
+				"slug", body.Slug, "chapter", n, "lang", body.Lang, "err", err)
+			jsonError(w, http.StatusInternalServerError,
+				fmt.Sprintf("failed to create task for chapter %d: %s", n, err))
+			return
+		}
+		taskIDs = append(taskIDs, id)
+	}
+
+	writeJSON(w, http.StatusAccepted, map[string]any{
+		"enqueued": len(taskIDs),
+		"task_ids": taskIDs,
+	})
+}
+
+// ── Voices ─────────────────────────────────────────────────────────────────────
 // Returns {"voices": [...]} — merged list from Kokoro and pocket-tts.
 func (s *Server) handleVoices(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, 0, map[string]any{"voices": s.voices(r.Context())})

backend/internal/backend/server.go

@@ -47,6 +47,8 @@ type Dependencies struct {
 	RankingStore bookstore.RankingStore
 	// AudioStore checks audio object existence and computes MinIO keys.
 	AudioStore bookstore.AudioStore
+	// TranslationStore checks translation existence and reads/writes translated markdown.
+	TranslationStore bookstore.TranslationStore
 	// PresignStore generates short-lived MinIO URLs.
 	PresignStore bookstore.PresignStore
 	// ProgressStore reads/writes per-session reading progress.
@@ -160,6 +162,15 @@ func (s *Server) ListenAndServe(ctx context.Context) error {
 	mux.HandleFunc("GET /api/audio/status/{slug}/{n}", s.handleAudioStatus)
 	mux.HandleFunc("GET /api/audio-proxy/{slug}/{n}", s.handleAudioProxy)
 
+	// Translation task creation (backend creates task; runner executes via LibreTranslate)
+	mux.HandleFunc("POST /api/translation/{slug}/{n}", s.handleTranslationGenerate)
+	mux.HandleFunc("GET /api/translation/status/{slug}/{n}", s.handleTranslationStatus)
+	mux.HandleFunc("GET /api/translation/{slug}/{n}", s.handleTranslationRead)
+
+	// Admin translation endpoints
+	mux.HandleFunc("GET /api/admin/translation/jobs", s.handleAdminTranslationJobs)
+	mux.HandleFunc("POST /api/admin/translation/bulk", s.handleAdminTranslationBulk)
+
 	// Voices list
 	mux.HandleFunc("GET /api/voices", s.handleVoices)
 

backend/internal/bookstore/bookstore.go

@@ -141,3 +141,19 @@ type CoverStore interface {
 	// CoverExists returns true when a cover image is stored for slug.
 	CoverExists(ctx context.Context, slug string) bool
 }
+
+// TranslationStore covers machine-translated chapter storage in MinIO.
+// The runner writes translations; the backend reads them.
+type TranslationStore interface {
+	// TranslationObjectKey returns the MinIO object key for a cached translation.
+	TranslationObjectKey(lang, slug string, n int) string
+
+	// TranslationExists returns true when the translation object is present in MinIO.
+	TranslationExists(ctx context.Context, key string) bool
+
+	// PutTranslation stores raw translated markdown under the given MinIO object key.
+	PutTranslation(ctx context.Context, key string, data []byte) error
+
+	// GetTranslation retrieves translated markdown from MinIO.
+	GetTranslation(ctx context.Context, key string) (string, error)
+}

backend/internal/config/config.go

@@ -46,6 +46,8 @@ type MinIO struct {
 	BucketAvatars string
 	// BucketBrowse is the bucket that holds cached browse page snapshots (JSON).
 	BucketBrowse string
+	// BucketTranslations is the bucket that holds machine-translated chapter markdown.
+	BucketTranslations string
 }
 
 // Kokoro holds connection settings for the Kokoro-FastAPI TTS service.
@@ -64,6 +66,16 @@ type PocketTTS struct {
 	URL string
 }
 
+// LibreTranslate holds connection settings for a self-hosted LibreTranslate instance.
+type LibreTranslate struct {
+	// URL is the base URL of the LibreTranslate instance, e.g. https://translate.libnovel.cc
+	// An empty string disables machine translation entirely.
+	URL string
+	// APIKey is the optional API key for the LibreTranslate instance.
+	// Leave empty if the instance runs without authentication.
+	APIKey string
+}
+
 // HTTP holds settings for the HTTP server (backend only).
 type HTTP struct {
 	// Addr is the listen address, e.g. ":8080"
@@ -107,6 +119,8 @@ type Runner struct {
 	MaxConcurrentScrape int
 	// MaxConcurrentAudio limits simultaneous audio-generation goroutines.
 	MaxConcurrentAudio int
+	// MaxConcurrentTranslation limits simultaneous translation goroutines.
+	MaxConcurrentTranslation int
 	// WorkerID is a unique identifier for this runner instance.
 	// Defaults to the system hostname.
 	WorkerID string
@@ -135,15 +149,16 @@ type Runner struct {
 
 // Config is the top-level configuration struct consumed by both binaries.
 type Config struct {
-	PocketBase  PocketBase
-	MinIO       MinIO
-	Kokoro      Kokoro
-	PocketTTS   PocketTTS
-	HTTP        HTTP
-	Runner      Runner
-	Meilisearch Meilisearch
-	Valkey      Valkey
-	Redis       Redis
+	PocketBase     PocketBase
+	MinIO          MinIO
+	Kokoro         Kokoro
+	PocketTTS      PocketTTS
+	LibreTranslate LibreTranslate
+	HTTP           HTTP
+	Runner         Runner
+	Meilisearch    Meilisearch
+	Valkey         Valkey
+	Redis          Redis
 	// LogLevel is one of "debug", "info", "warn", "error".
 	LogLevel string
 }
@@ -166,16 +181,17 @@ func Load() Config {
 		},
 
 		MinIO: MinIO{
-			Endpoint:       envOr("MINIO_ENDPOINT", "localhost:9000"),
-			PublicEndpoint: envOr("MINIO_PUBLIC_ENDPOINT", ""),
-			AccessKey:      envOr("MINIO_ACCESS_KEY", "admin"),
-			SecretKey:      envOr("MINIO_SECRET_KEY", "changeme123"),
-			UseSSL:         envBool("MINIO_USE_SSL", false),
-			PublicUseSSL:   envBool("MINIO_PUBLIC_USE_SSL", true),
-			BucketChapters: envOr("MINIO_BUCKET_CHAPTERS", "chapters"),
-			BucketAudio:    envOr("MINIO_BUCKET_AUDIO", "audio"),
-			BucketAvatars:  envOr("MINIO_BUCKET_AVATARS", "avatars"),
-			BucketBrowse:   envOr("MINIO_BUCKET_BROWSE", "catalogue"),
+			Endpoint:           envOr("MINIO_ENDPOINT", "localhost:9000"),
+			PublicEndpoint:     envOr("MINIO_PUBLIC_ENDPOINT", ""),
+			AccessKey:          envOr("MINIO_ACCESS_KEY", "admin"),
+			SecretKey:          envOr("MINIO_SECRET_KEY", "changeme123"),
+			UseSSL:             envBool("MINIO_USE_SSL", false),
+			PublicUseSSL:       envBool("MINIO_PUBLIC_USE_SSL", true),
+			BucketChapters:     envOr("MINIO_BUCKET_CHAPTERS", "chapters"),
+			BucketAudio:        envOr("MINIO_BUCKET_AUDIO", "audio"),
+			BucketAvatars:      envOr("MINIO_BUCKET_AVATARS", "avatars"),
+			BucketBrowse:       envOr("MINIO_BUCKET_BROWSE", "catalogue"),
+			BucketTranslations: envOr("MINIO_BUCKET_TRANSLATIONS", "translations"),
 		},
 
 		Kokoro: Kokoro{
@@ -195,6 +211,7 @@ func Load() Config {
 			PollInterval:                envDuration("RUNNER_POLL_INTERVAL", 30*time.Second),
 			MaxConcurrentScrape:         envInt("RUNNER_MAX_CONCURRENT_SCRAPE", 1),
 			MaxConcurrentAudio:          envInt("RUNNER_MAX_CONCURRENT_AUDIO", 1),
+			MaxConcurrentTranslation:    envInt("RUNNER_MAX_CONCURRENT_TRANSLATION", 1),
 			WorkerID:                    envOr("RUNNER_WORKER_ID", workerID),
 			Workers:                     envInt("RUNNER_WORKERS", 0), // 0 → runtime.NumCPU()
 			Timeout:                     envDuration("RUNNER_TIMEOUT", 90*time.Second),

backend/internal/domain/domain.go

@@ -149,3 +149,23 @@ type AudioResult struct {
 	ObjectKey    string `json:"object_key,omitempty"`
 	ErrorMessage string `json:"error_message,omitempty"`
 }
+
+// TranslationTask represents a machine-translation job stored in PocketBase.
+type TranslationTask struct {
+	ID           string     `json:"id"`
+	CacheKey     string     `json:"cache_key"` // "{slug}/{chapter}/{lang}"
+	Slug         string     `json:"slug"`
+	Chapter      int        `json:"chapter"`
+	Lang         string     `json:"lang"`
+	WorkerID     string     `json:"worker_id,omitempty"`
+	Status       TaskStatus `json:"status"`
+	ErrorMessage string     `json:"error_message,omitempty"`
+	Started      time.Time  `json:"started"`
+	Finished     time.Time  `json:"finished,omitempty"`
+}
+
+// TranslationResult is the outcome reported by the runner after finishing a TranslationTask.
+type TranslationResult struct {
+	ObjectKey    string `json:"object_key,omitempty"`
+	ErrorMessage string `json:"error_message,omitempty"`
+}

backend/internal/libretranslate/client.go

@@ -0,0 +1,181 @@
+// Package libretranslate provides an HTTP client for a self-hosted
+// LibreTranslate instance. It handles text chunking, concurrent translation,
+// and reassembly so callers can pass arbitrarily long markdown strings.
+package libretranslate
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	// maxChunkBytes is the target maximum size of each chunk sent to
+	// LibreTranslate. LibreTranslate's default limit is 5000 characters;
+	// we stay comfortably below that.
+	maxChunkBytes = 4500
+	// concurrency is the number of simultaneous translation requests per chapter.
+	concurrency = 3
+)
+
+// Client translates text via LibreTranslate.
+// A nil Client is valid — all calls return the original text unchanged.
+type Client interface {
+	// Translate translates text from sourceLang to targetLang.
+	// text is a raw markdown string. The returned string is the translated
+	// markdown, reassembled in original paragraph order.
+	Translate(ctx context.Context, text, sourceLang, targetLang string) (string, error)
+}
+
+// New returns a Client for the given LibreTranslate URL.
+// Returns nil when url is empty, which disables translation.
+func New(url, apiKey string) Client {
+	if url == "" {
+		return nil
+	}
+	return &httpClient{
+		url:    strings.TrimRight(url, "/"),
+		apiKey: apiKey,
+		http:   &http.Client{Timeout: 60 * time.Second},
+	}
+}
+
+type httpClient struct {
+	url    string
+	apiKey string
+	http   *http.Client
+}
+
+// Translate splits text into paragraph chunks, translates them concurrently
+// (up to concurrency goroutines), and reassembles in order.
+func (c *httpClient) Translate(ctx context.Context, text, sourceLang, targetLang string) (string, error) {
+	paragraphs := splitParagraphs(text)
+	if len(paragraphs) == 0 {
+		return text, nil
+	}
+	chunks := binChunks(paragraphs, maxChunkBytes)
+
+	translated := make([]string, len(chunks))
+	errs := make([]error, len(chunks))
+
+	sem := make(chan struct{}, concurrency)
+	var wg sync.WaitGroup
+
+	for i, chunk := range chunks {
+		wg.Add(1)
+		sem <- struct{}{}
+		go func(idx int, chunkText string) {
+			defer wg.Done()
+			defer func() { <-sem }()
+			result, err := c.translateChunk(ctx, chunkText, sourceLang, targetLang)
+			translated[idx] = result
+			errs[idx] = err
+		}(i, chunk)
+	}
+	wg.Wait()
+
+	for _, err := range errs {
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return strings.Join(translated, "\n\n"), nil
+}
+
+// translateChunk sends a single POST /translate request.
+func (c *httpClient) translateChunk(ctx context.Context, text, sourceLang, targetLang string) (string, error) {
+	reqBody := map[string]string{
+		"q":      text,
+		"source": sourceLang,
+		"target": targetLang,
+		"format": "html",
+	}
+	if c.apiKey != "" {
+		reqBody["api_key"] = c.apiKey
+	}
+
+	b, err := json.Marshal(reqBody)
+	if err != nil {
+		return "", fmt.Errorf("libretranslate: marshal request: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.url+"/translate", bytes.NewReader(b))
+	if err != nil {
+		return "", fmt.Errorf("libretranslate: build request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.http.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("libretranslate: request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		var errBody struct {
+			Error string `json:"error"`
+		}
+		_ = json.NewDecoder(resp.Body).Decode(&errBody)
+		return "", fmt.Errorf("libretranslate: status %d: %s", resp.StatusCode, errBody.Error)
+	}
+
+	var result struct {
+		TranslatedText string `json:"translatedText"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return "", fmt.Errorf("libretranslate: decode response: %w", err)
+	}
+	return result.TranslatedText, nil
+}
+
+// splitParagraphs splits markdown text on blank lines, preserving non-empty paragraphs.
+func splitParagraphs(text string) []string {
+	// Normalise line endings.
+	text = strings.ReplaceAll(text, "\r\n", "\n")
+	// Split on double newlines (blank lines between paragraphs).
+	parts := strings.Split(text, "\n\n")
+	var paragraphs []string
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p != "" {
+			paragraphs = append(paragraphs, p)
+		}
+	}
+	return paragraphs
+}
+
+// binChunks groups paragraphs into chunks each at most maxBytes in length.
+// Each chunk is a single string with paragraphs joined by "\n\n".
+func binChunks(paragraphs []string, maxBytes int) []string {
+	var chunks []string
+	var current strings.Builder
+
+	for _, p := range paragraphs {
+		needed := len(p)
+		if current.Len() > 0 {
+			needed += 2 // for the "\n\n" separator
+		}
+
+		if current.Len()+needed > maxBytes && current.Len() > 0 {
+			// Flush current chunk.
+			chunks = append(chunks, current.String())
+			current.Reset()
+		}
+
+		if current.Len() > 0 {
+			current.WriteString("\n\n")
+		}
+		current.WriteString(p)
+	}
+
+	if current.Len() > 0 {
+		chunks = append(chunks, current.String())
+	}
+	return chunks
+}

backend/internal/runner/runner.go

@@ -29,6 +29,7 @@ import (
 	"github.com/libnovel/backend/internal/bookstore"
 	"github.com/libnovel/backend/internal/domain"
 	"github.com/libnovel/backend/internal/kokoro"
+	"github.com/libnovel/backend/internal/libretranslate"
 	"github.com/libnovel/backend/internal/meili"
 	"github.com/libnovel/backend/internal/orchestrator"
 	"github.com/libnovel/backend/internal/pockettts"
@@ -48,6 +49,8 @@ type Config struct {
 	MaxConcurrentScrape int
 	// MaxConcurrentAudio limits simultaneous audio-generation goroutines.
 	MaxConcurrentAudio int
+	// MaxConcurrentTranslation limits simultaneous translation goroutines.
+	MaxConcurrentTranslation int
 	// OrchestratorWorkers is the chapter-scraping parallelism inside each book run.
 	OrchestratorWorkers int
 	// HeartbeatInterval is how often active tasks PATCH their heartbeat_at
@@ -95,6 +98,8 @@ type Dependencies struct {
 	BookReader bookstore.BookReader
 	// AudioStore persists generated audio and checks key existence.
 	AudioStore bookstore.AudioStore
+	// TranslationStore persists translated markdown and checks key existence.
+	TranslationStore bookstore.TranslationStore
 	// CoverStore stores book cover images in MinIO.
 	CoverStore bookstore.CoverStore
 	// SearchIndex indexes books in Meilisearch after scraping.
@@ -107,6 +112,9 @@ type Dependencies struct {
 	// PocketTTS is the pocket-tts client (CPU, kyutai voices: alba, marius, etc.).
 	// If nil, pocket-tts voice tasks will fail with a clear error.
 	PocketTTS pockettts.Client
+	// LibreTranslate is the machine translation client.
+	// If nil, translation tasks will fail with a clear error.
+	LibreTranslate libretranslate.Client
 	// Log is the structured logger.
 	Log *slog.Logger
 }
@@ -137,6 +145,9 @@ func New(cfg Config, deps Dependencies) *Runner {
 	if cfg.MaxConcurrentAudio <= 0 {
 		cfg.MaxConcurrentAudio = 1
 	}
+	if cfg.MaxConcurrentTranslation <= 0 {
+		cfg.MaxConcurrentTranslation = 1
+	}
 	if cfg.WorkerID == "" {
 		cfg.WorkerID = "runner"
 	}
@@ -175,6 +186,7 @@ func (r *Runner) Run(ctx context.Context) error {
 		"mode", r.mode(),
 		"max_scrape", r.cfg.MaxConcurrentScrape,
 		"max_audio", r.cfg.MaxConcurrentAudio,
+		"max_translation", r.cfg.MaxConcurrentTranslation,
 		"catalogue_refresh_interval", r.cfg.CatalogueRefreshInterval,
 		"metrics_addr", r.cfg.MetricsAddr,
 	)
@@ -208,6 +220,7 @@ func (r *Runner) mode() string {
 func (r *Runner) runPoll(ctx context.Context) error {
 	scrapeSem := make(chan struct{}, r.cfg.MaxConcurrentScrape)
 	audioSem := make(chan struct{}, r.cfg.MaxConcurrentAudio)
+	translationSem := make(chan struct{}, r.cfg.MaxConcurrentTranslation)
 	var wg sync.WaitGroup
 
 	tick := time.NewTicker(r.cfg.PollInterval)
@@ -227,7 +240,7 @@ func (r *Runner) runPoll(ctx context.Context) error {
 
 	// Run one poll immediately on startup, then on each tick.
 	for {
-		r.poll(ctx, scrapeSem, audioSem, &wg)
+		r.poll(ctx, scrapeSem, audioSem, translationSem, &wg)
 
 		select {
 		case <-ctx.Done():
@@ -252,7 +265,7 @@ func (r *Runner) runPoll(ctx context.Context) error {
 }
 
 // poll claims all available pending tasks and dispatches them to goroutines.
-func (r *Runner) poll(ctx context.Context, scrapeSem, audioSem chan struct{}, wg *sync.WaitGroup) {
+func (r *Runner) poll(ctx context.Context, scrapeSem, audioSem, translationSem chan struct{}, wg *sync.WaitGroup) {
 	// ── Heartbeat file ────────────────────────────────────────────────────
 	// Touch /tmp/runner.alive so the Docker health check can confirm the
 	// runner is actively polling. Failure is non-fatal — just log it.
@@ -335,6 +348,39 @@ audioLoop:
 			r.runAudioTask(ctx, t)
 		}(task)
 	}
+
+	// ── Translation tasks ─────────────────────────────────────────────────
+translationLoop:
+	for {
+		if ctx.Err() != nil {
+			return
+		}
+		select {
+		case translationSem <- struct{}{}:
+			// Slot acquired — proceed to claim a task.
+		default:
+			// All slots busy; leave remaining pending tasks for next tick.
+			break translationLoop
+		}
+		task, ok, err := r.deps.Consumer.ClaimNextTranslationTask(ctx, r.cfg.WorkerID)
+		if err != nil {
+			<-translationSem
+			r.deps.Log.Error("runner: ClaimNextTranslationTask failed", "err", err)
+			break
+		}
+		if !ok {
+			<-translationSem
+			break
+		}
+		r.tasksRunning.Add(1)
+		wg.Add(1)
+		go func(t domain.TranslationTask) {
+			defer wg.Done()
+			defer func() { <-translationSem }()
+			defer r.tasksRunning.Add(-1)
+			r.runTranslationTask(ctx, t)
+		}(task)
+	}
 }
 
 // newOrchestrator builds an orchestrator with the Meilisearch post-hook wired in.

backend/internal/runner/runner_test.go

@@ -48,6 +48,10 @@ func (s *stubConsumer) ClaimNextAudioTask(_ context.Context, _ string) (domain.A
 	return t, true, nil
 }
 
+func (s *stubConsumer) ClaimNextTranslationTask(_ context.Context, _ string) (domain.TranslationTask, bool, error) {
+	return domain.TranslationTask{}, false, nil
+}
+
 func (s *stubConsumer) FinishScrapeTask(_ context.Context, id string, _ domain.ScrapeResult) error {
 	s.finished = append(s.finished, id)
 	return nil
@@ -58,6 +62,11 @@ func (s *stubConsumer) FinishAudioTask(_ context.Context, id string, _ domain.Au
 	return nil
 }
 
+func (s *stubConsumer) FinishTranslationTask(_ context.Context, id string, _ domain.TranslationResult) error {
+	s.finished = append(s.finished, id)
+	return nil
+}
+
 func (s *stubConsumer) FailTask(_ context.Context, id, _ string) error {
 	s.failCalled = append(s.failCalled, id)
 	return nil

backend/internal/runner/translation.go

@@ -0,0 +1,97 @@
+package runner
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+
+	"github.com/libnovel/backend/internal/domain"
+)
+
+// runTranslationTask executes one machine-translation task end-to-end and
+// reports the result back to PocketBase.
+func (r *Runner) runTranslationTask(ctx context.Context, task domain.TranslationTask) {
+	ctx, span := otel.Tracer("runner").Start(ctx, "runner.translation_task")
+	defer span.End()
+	span.SetAttributes(
+		attribute.String("task.id", task.ID),
+		attribute.String("book.slug", task.Slug),
+		attribute.Int("chapter.number", task.Chapter),
+		attribute.String("translation.lang", task.Lang),
+	)
+
+	log := r.deps.Log.With("task_id", task.ID, "slug", task.Slug, "chapter", task.Chapter, "lang", task.Lang)
+	log.Info("runner: translation task starting")
+
+	// Heartbeat goroutine — keeps the task alive while translation runs.
+	hbCtx, hbCancel := context.WithCancel(ctx)
+	defer hbCancel()
+	go func() {
+		tick := time.NewTicker(r.cfg.HeartbeatInterval)
+		defer tick.Stop()
+		for {
+			select {
+			case <-hbCtx.Done():
+				return
+			case <-tick.C:
+				if err := r.deps.Consumer.HeartbeatTask(ctx, task.ID); err != nil {
+					log.Warn("runner: heartbeat failed", "err", err)
+				}
+			}
+		}
+	}()
+
+	fail := func(msg string) {
+		log.Error("runner: translation task failed", "reason", msg)
+		r.tasksFailed.Add(1)
+		span.SetStatus(codes.Error, msg)
+		result := domain.TranslationResult{ErrorMessage: msg}
+		if err := r.deps.Consumer.FinishTranslationTask(ctx, task.ID, result); err != nil {
+			log.Error("runner: FinishTranslationTask failed", "err", err)
+		}
+	}
+
+	// Guard: LibreTranslate must be configured.
+	if r.deps.LibreTranslate == nil {
+		fail("libretranslate client not configured (LIBRETRANSLATE_URL is empty)")
+		return
+	}
+
+	// 1. Read raw markdown chapter.
+	raw, err := r.deps.BookReader.ReadChapter(ctx, task.Slug, task.Chapter)
+	if err != nil {
+		fail(fmt.Sprintf("read chapter: %v", err))
+		return
+	}
+	if raw == "" {
+		fail("chapter text is empty")
+		return
+	}
+
+	// 2. Translate (chunked, concurrent).
+	translated, err := r.deps.LibreTranslate.Translate(ctx, raw, "en", task.Lang)
+	if err != nil {
+		fail(fmt.Sprintf("translate: %v", err))
+		return
+	}
+
+	// 3. Store translated markdown in MinIO.
+	key := r.deps.TranslationStore.TranslationObjectKey(task.Lang, task.Slug, task.Chapter)
+	if err := r.deps.TranslationStore.PutTranslation(ctx, key, []byte(translated)); err != nil {
+		fail(fmt.Sprintf("put translation: %v", err))
+		return
+	}
+
+	// 4. Report success.
+	r.tasksCompleted.Add(1)
+	span.SetStatus(codes.Ok, "")
+	result := domain.TranslationResult{ObjectKey: key}
+	if err := r.deps.Consumer.FinishTranslationTask(ctx, task.ID, result); err != nil {
+		log.Error("runner: FinishTranslationTask failed", "err", err)
+	}
+	log.Info("runner: translation task finished", "key", key)
+}

backend/internal/storage/minio.go

@@ -17,12 +17,13 @@ import (
 
 // minioClient wraps the official minio-go client with bucket names.
 type minioClient struct {
-	client         *minio.Client // internal — all read/write operations
-	pubClient      *minio.Client // presign-only — initialised against the public endpoint
-	bucketChapters string
-	bucketAudio    string
-	bucketAvatars  string
-	bucketBrowse   string
+	client             *minio.Client // internal — all read/write operations
+	pubClient          *minio.Client // presign-only — initialised against the public endpoint
+	bucketChapters     string
+	bucketAudio        string
+	bucketAvatars      string
+	bucketBrowse       string
+	bucketTranslations string
 }
 
 func newMinioClient(cfg config.MinIO) (*minioClient, error) {
@@ -74,18 +75,19 @@ func newMinioClient(cfg config.MinIO) (*minioClient, error) {
 	}
 
 	return &minioClient{
-		client:         internal,
-		pubClient:      pub,
-		bucketChapters: cfg.BucketChapters,
-		bucketAudio:    cfg.BucketAudio,
-		bucketAvatars:  cfg.BucketAvatars,
-		bucketBrowse:   cfg.BucketBrowse,
+		client:             internal,
+		pubClient:          pub,
+		bucketChapters:     cfg.BucketChapters,
+		bucketAudio:        cfg.BucketAudio,
+		bucketAvatars:      cfg.BucketAvatars,
+		bucketBrowse:       cfg.BucketBrowse,
+		bucketTranslations: cfg.BucketTranslations,
 	}, nil
 }
 
 // ensureBuckets creates all required buckets if they don't already exist.
 func (m *minioClient) ensureBuckets(ctx context.Context) error {
-	for _, bucket := range []string{m.bucketChapters, m.bucketAudio, m.bucketAvatars, m.bucketBrowse} {
+	for _, bucket := range []string{m.bucketChapters, m.bucketAudio, m.bucketAvatars, m.bucketBrowse, m.bucketTranslations} {
 		exists, err := m.client.BucketExists(ctx, bucket)
 		if err != nil {
 			return fmt.Errorf("minio: check bucket %q: %w", bucket, err)
@@ -125,6 +127,12 @@ func CoverObjectKey(slug string) string {
 	return fmt.Sprintf("covers/%s.jpg", slug)
 }
 
+// TranslationObjectKey returns the MinIO object key for a translated chapter.
+// Format: {lang}/{slug}/{n:06d}.md
+func TranslationObjectKey(lang, slug string, n int) string {
+	return fmt.Sprintf("%s/%s/%06d.md", lang, slug, n)
+}
+
 // chapterNumberFromKey extracts the chapter number from a MinIO object key.
 // e.g. "my-book/chapter-000042.md" → 42
 func chapterNumberFromKey(key string) int {

backend/internal/storage/store.go

@@ -51,6 +51,7 @@ var _ bookstore.AudioStore = (*Store)(nil)
 var _ bookstore.PresignStore = (*Store)(nil)
 var _ bookstore.ProgressStore = (*Store)(nil)
 var _ bookstore.CoverStore = (*Store)(nil)
+var _ bookstore.TranslationStore = (*Store)(nil)
 var _ taskqueue.Producer = (*Store)(nil)
 var _ taskqueue.Consumer = (*Store)(nil)
 var _ taskqueue.Reader = (*Store)(nil)
@@ -535,13 +536,36 @@ func (s *Store) CreateAudioTask(ctx context.Context, slug string, chapter int, v
 	return rec.ID, nil
 }
 
+func (s *Store) CreateTranslationTask(ctx context.Context, slug string, chapter int, lang string) (string, error) {
+	cacheKey := fmt.Sprintf("%s/%d/%s", slug, chapter, lang)
+	payload := map[string]any{
+		"cache_key": cacheKey,
+		"slug":      slug,
+		"chapter":   chapter,
+		"lang":      lang,
+		"status":    string(domain.TaskStatusPending),
+		"started":   time.Now().UTC().Format(time.RFC3339),
+	}
+	var rec struct {
+		ID string `json:"id"`
+	}
+	if err := s.pb.post(ctx, "/api/collections/translation_jobs/records", payload, &rec); err != nil {
+		return "", err
+	}
+	return rec.ID, nil
+}
+
 func (s *Store) CancelTask(ctx context.Context, id string) error {
-	// Try scraping_tasks first, then audio_jobs.
+	// Try scraping_tasks first, then audio_jobs, then translation_jobs.
 	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/scraping_tasks/records/%s", id),
 		map[string]string{"status": string(domain.TaskStatusCancelled)}); err == nil {
 		return nil
 	}
-	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id),
+	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id),
+		map[string]string{"status": string(domain.TaskStatusCancelled)}); err == nil {
+		return nil
+	}
+	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/translation_jobs/records/%s", id),
 		map[string]string{"status": string(domain.TaskStatusCancelled)})
 }
 
@@ -571,6 +595,18 @@ func (s *Store) ClaimNextAudioTask(ctx context.Context, workerID string) (domain
 	return task, err == nil, err
 }
 
+func (s *Store) ClaimNextTranslationTask(ctx context.Context, workerID string) (domain.TranslationTask, bool, error) {
+	raw, err := s.pb.claimRecord(ctx, "translation_jobs", workerID, nil)
+	if err != nil {
+		return domain.TranslationTask{}, false, err
+	}
+	if raw == nil {
+		return domain.TranslationTask{}, false, nil
+	}
+	task, err := parseTranslationTask(raw)
+	return task, err == nil, err
+}
+
 func (s *Store) FinishScrapeTask(ctx context.Context, id string, result domain.ScrapeResult) error {
 	status := string(domain.TaskStatusDone)
 	if result.ErrorMessage != "" {
@@ -599,6 +635,18 @@ func (s *Store) FinishAudioTask(ctx context.Context, id string, result domain.Au
 	})
 }
 
+func (s *Store) FinishTranslationTask(ctx context.Context, id string, result domain.TranslationResult) error {
+	status := string(domain.TaskStatusDone)
+	if result.ErrorMessage != "" {
+		status = string(domain.TaskStatusFailed)
+	}
+	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/translation_jobs/records/%s", id), map[string]any{
+		"status":        status,
+		"error_message": result.ErrorMessage,
+		"finished":      time.Now().UTC().Format(time.RFC3339),
+	})
+}
+
 func (s *Store) FailTask(ctx context.Context, id, errMsg string) error {
 	payload := map[string]any{
 		"status":        string(domain.TaskStatusFailed),
@@ -608,11 +656,14 @@ func (s *Store) FailTask(ctx context.Context, id, errMsg string) error {
 	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/scraping_tasks/records/%s", id), payload); err == nil {
 		return nil
 	}
-	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id), payload)
+	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id), payload); err == nil {
+		return nil
+	}
+	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/translation_jobs/records/%s", id), payload)
 }
 
 // HeartbeatTask updates the heartbeat_at field on a running task.
-// Tries scraping_tasks first, then audio_jobs (same pattern as FailTask).
+// Tries scraping_tasks first, then audio_jobs, then translation_jobs.
 func (s *Store) HeartbeatTask(ctx context.Context, id string) error {
 	payload := map[string]any{
 		"heartbeat_at": time.Now().UTC().Format(time.RFC3339),
@@ -620,7 +671,10 @@ func (s *Store) HeartbeatTask(ctx context.Context, id string) error {
 	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/scraping_tasks/records/%s", id), payload); err == nil {
 		return nil
 	}
-	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id), payload)
+	if err := s.pb.patch(ctx, fmt.Sprintf("/api/collections/audio_jobs/records/%s", id), payload); err == nil {
+		return nil
+	}
+	return s.pb.patch(ctx, fmt.Sprintf("/api/collections/translation_jobs/records/%s", id), payload)
 }
 
 // ReapStaleTasks finds all running tasks whose heartbeat_at is either missing
@@ -638,7 +692,7 @@ func (s *Store) ReapStaleTasks(ctx context.Context, staleAfter time.Duration) (i
 	}
 
 	total := 0
-	for _, collection := range []string{"scraping_tasks", "audio_jobs"} {
+	for _, collection := range []string{"scraping_tasks", "audio_jobs", "translation_jobs"} {
 		items, err := s.pb.listAll(ctx, collection, filter, "")
 		if err != nil {
 			return total, fmt.Errorf("ReapStaleTasks list %s: %w", collection, err)
@@ -715,6 +769,31 @@ func (s *Store) GetAudioTask(ctx context.Context, cacheKey string) (domain.Audio
 	return t, err == nil, err
 }
 
+func (s *Store) ListTranslationTasks(ctx context.Context) ([]domain.TranslationTask, error) {
+	items, err := s.pb.listAll(ctx, "translation_jobs", "", "-started")
+	if err != nil {
+		return nil, err
+	}
+	tasks := make([]domain.TranslationTask, 0, len(items))
+	for _, raw := range items {
+		t, err := parseTranslationTask(raw)
+		if err == nil {
+			tasks = append(tasks, t)
+		}
+	}
+	return tasks, nil
+}
+
+func (s *Store) GetTranslationTask(ctx context.Context, cacheKey string) (domain.TranslationTask, bool, error) {
+	filter := fmt.Sprintf(`cache_key='%s'`, cacheKey)
+	items, err := s.pb.listAll(ctx, "translation_jobs", filter, "-started")
+	if err != nil || len(items) == 0 {
+		return domain.TranslationTask{}, false, err
+	}
+	t, err := parseTranslationTask(items[0])
+	return t, err == nil, err
+}
+
 // ── Parsers ───────────────────────────────────────────────────────────────────
 
 func parseScrapeTask(raw json.RawMessage) (domain.ScrapeTask, error) {
@@ -789,6 +868,38 @@ func parseAudioTask(raw json.RawMessage) (domain.AudioTask, error) {
 	}, nil
 }
 
+func parseTranslationTask(raw json.RawMessage) (domain.TranslationTask, error) {
+	var rec struct {
+		ID           string `json:"id"`
+		CacheKey     string `json:"cache_key"`
+		Slug         string `json:"slug"`
+		Chapter      int    `json:"chapter"`
+		Lang         string `json:"lang"`
+		WorkerID     string `json:"worker_id"`
+		Status       string `json:"status"`
+		ErrorMessage string `json:"error_message"`
+		Started      string `json:"started"`
+		Finished     string `json:"finished"`
+	}
+	if err := json.Unmarshal(raw, &rec); err != nil {
+		return domain.TranslationTask{}, err
+	}
+	started, _ := time.Parse(time.RFC3339, rec.Started)
+	finished, _ := time.Parse(time.RFC3339, rec.Finished)
+	return domain.TranslationTask{
+		ID:           rec.ID,
+		CacheKey:     rec.CacheKey,
+		Slug:         rec.Slug,
+		Chapter:      rec.Chapter,
+		Lang:         rec.Lang,
+		WorkerID:     rec.WorkerID,
+		Status:       domain.TaskStatus(rec.Status),
+		ErrorMessage: rec.ErrorMessage,
+		Started:      started,
+		Finished:     finished,
+	}, nil
+}
+
 // ── CoverStore ─────────────────────────────────────────────────────────────────
 
 func (s *Store) PutCover(ctx context.Context, slug string, data []byte, contentType string) error {
@@ -818,3 +929,25 @@ func (s *Store) GetCover(ctx context.Context, slug string) ([]byte, string, bool
 func (s *Store) CoverExists(ctx context.Context, slug string) bool {
 	return s.mc.coverExists(ctx, CoverObjectKey(slug))
 }
+
+// ── TranslationStore ───────────────────────────────────────────────────────────
+
+func (s *Store) TranslationObjectKey(lang, slug string, n int) string {
+	return TranslationObjectKey(lang, slug, n)
+}
+
+func (s *Store) TranslationExists(ctx context.Context, key string) bool {
+	return s.mc.objectExists(ctx, s.mc.bucketTranslations, key)
+}
+
+func (s *Store) PutTranslation(ctx context.Context, key string, data []byte) error {
+	return s.mc.putObject(ctx, s.mc.bucketTranslations, key, "text/markdown; charset=utf-8", data)
+}
+
+func (s *Store) GetTranslation(ctx context.Context, key string) (string, error) {
+	data, err := s.mc.getObject(ctx, s.mc.bucketTranslations, key)
+	if err != nil {
+		return "", fmt.Errorf("GetTranslation: %w", err)
+	}
+	return string(data), nil
+}

backend/internal/taskqueue/taskqueue.go

@@ -29,6 +29,10 @@ type Producer interface {
 	// returns the assigned PocketBase record ID.
 	CreateAudioTask(ctx context.Context, slug string, chapter int, voice string) (string, error)
 
+	// CreateTranslationTask inserts a new translation task with status=pending and
+	// returns the assigned PocketBase record ID.
+	CreateTranslationTask(ctx context.Context, slug string, chapter int, lang string) (string, error)
+
 	// CancelTask transitions a pending task to status=cancelled.
 	// Returns ErrNotFound if the task does not exist.
 	CancelTask(ctx context.Context, id string) error
@@ -46,13 +50,21 @@ type Consumer interface {
 	// Returns (zero, false, nil) when the queue is empty.
 	ClaimNextAudioTask(ctx context.Context, workerID string) (domain.AudioTask, bool, error)
 
+	// ClaimNextTranslationTask atomically finds the oldest pending translation task,
+	// sets its status=running and worker_id=workerID, and returns it.
+	// Returns (zero, false, nil) when the queue is empty.
+	ClaimNextTranslationTask(ctx context.Context, workerID string) (domain.TranslationTask, bool, error)
+
 	// FinishScrapeTask marks a running scrape task as done and records the result.
 	FinishScrapeTask(ctx context.Context, id string, result domain.ScrapeResult) error
 
 	// FinishAudioTask marks a running audio task as done and records the result.
 	FinishAudioTask(ctx context.Context, id string, result domain.AudioResult) error
 
-	// FailTask marks a task (scrape or audio) as failed with an error message.
+	// FinishTranslationTask marks a running translation task as done and records the result.
+	FinishTranslationTask(ctx context.Context, id string, result domain.TranslationResult) error
+
+	// FailTask marks a task (scrape, audio, or translation) as failed with an error message.
 	FailTask(ctx context.Context, id, errMsg string) error
 
 	// HeartbeatTask updates the heartbeat_at timestamp on a running task.
@@ -81,4 +93,11 @@ type Reader interface {
 	// GetAudioTask returns the most recent audio task for cacheKey.
 	// Returns (zero, false, nil) if not found.
 	GetAudioTask(ctx context.Context, cacheKey string) (domain.AudioTask, bool, error)
+
+	// ListTranslationTasks returns all translation tasks sorted by started descending.
+	ListTranslationTasks(ctx context.Context) ([]domain.TranslationTask, error)
+
+	// GetTranslationTask returns the most recent translation task for cacheKey.
+	// Returns (zero, false, nil) if not found.
+	GetTranslationTask(ctx context.Context, cacheKey string) (domain.TranslationTask, bool, error)
 }

backend/internal/taskqueue/taskqueue_test.go

@@ -23,6 +23,9 @@ func (s *stubStore) CreateScrapeTask(_ context.Context, _, _ string, _, _ int) (
 func (s *stubStore) CreateAudioTask(_ context.Context, _ string, _ int, _ string) (string, error) {
 	return "audio-1", nil
 }
+func (s *stubStore) CreateTranslationTask(_ context.Context, _ string, _ int, _ string) (string, error) {
+	return "translation-1", nil
+}
 func (s *stubStore) CancelTask(_ context.Context, _ string) error { return nil }
 
 func (s *stubStore) ClaimNextScrapeTask(_ context.Context, _ string) (domain.ScrapeTask, bool, error) {
@@ -31,12 +34,18 @@ func (s *stubStore) ClaimNextScrapeTask(_ context.Context, _ string) (domain.Scr
 func (s *stubStore) ClaimNextAudioTask(_ context.Context, _ string) (domain.AudioTask, bool, error) {
 	return domain.AudioTask{ID: "audio-1", Status: domain.TaskStatusRunning}, true, nil
 }
+func (s *stubStore) ClaimNextTranslationTask(_ context.Context, _ string) (domain.TranslationTask, bool, error) {
+	return domain.TranslationTask{ID: "translation-1", Status: domain.TaskStatusRunning}, true, nil
+}
 func (s *stubStore) FinishScrapeTask(_ context.Context, _ string, _ domain.ScrapeResult) error {
 	return nil
 }
 func (s *stubStore) FinishAudioTask(_ context.Context, _ string, _ domain.AudioResult) error {
 	return nil
 }
+func (s *stubStore) FinishTranslationTask(_ context.Context, _ string, _ domain.TranslationResult) error {
+	return nil
+}
 func (s *stubStore) FailTask(_ context.Context, _, _ string) error { return nil }
 
 func (s *stubStore) HeartbeatTask(_ context.Context, _ string) error { return nil }
@@ -53,6 +62,12 @@ func (s *stubStore) ListAudioTasks(_ context.Context) ([]domain.AudioTask, error
 func (s *stubStore) GetAudioTask(_ context.Context, _ string) (domain.AudioTask, bool, error) {
 	return domain.AudioTask{}, false, nil
 }
+func (s *stubStore) ListTranslationTasks(_ context.Context) ([]domain.TranslationTask, error) {
+	return nil, nil
+}
+func (s *stubStore) GetTranslationTask(_ context.Context, _ string) (domain.TranslationTask, bool, error) {
+	return domain.TranslationTask{}, false, nil
+}
 
 // Verify the stub satisfies all three interfaces at compile time.
 var _ taskqueue.Producer = (*stubStore)(nil)