feat(backend): handle processing errors and add PWA routes

- Block file downloads and previews with a 424 StatusFailedDependency if file processing failed or the box has issues. - Register routes for `/service-worker.js` and `/share-target` to support PWA features. - Update README.md with an AI usage disclosure.
2026-06-08 11:53:37 +03:00
parent dbfdacc396
commit d11aec96e5
26 changed files with 1186 additions and 35 deletions
--- a/backend/libs/handlers/app.go
+++ b/backend/libs/handlers/app.go
@@ -54,6 +54,8 @@ func (a *App) renderPage(w http.ResponseWriter, r *http.Request, status int, pag
 func (a *App) RegisterRoutes(mux *http.ServeMux) {
 	mux.HandleFunc("GET /", a.Home)
 	mux.HandleFunc("GET /api", a.APIDocs)
+	mux.HandleFunc("GET /service-worker.js", a.ServiceWorker)
+	mux.HandleFunc("POST /share-target", a.ShareTargetFallback)
 	mux.HandleFunc("GET /register", a.Register)
 	mux.HandleFunc("POST /register", a.RegisterPost)
 	mux.HandleFunc("GET /login", a.Login)
--- a/backend/libs/handlers/download.go
+++ b/backend/libs/handlers/download.go
@@ -59,6 +59,8 @@ type fileView struct {
 	ReactionMore int
 	Reacted      bool
 	Processing   bool
+	Failed       bool
+	Error        string
 }

 type reactionView struct {
@@ -242,12 +244,32 @@ func (a *App) DownloadFile(w http.ResponseWriter, r *http.Request) {
 			http.Error(w, "file is still processing", http.StatusAccepted)
 			return
 		}
+		if file.ProcessingError != "" {
+			a.logger.Warn("failed file preview blocked for social bot", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4241, "box_id", box.ID, "file_id", file.ID, "error", file.ProcessingError)...)
+			http.Error(w, "file processing failed: "+file.ProcessingError, http.StatusFailedDependency)
+			return
+		}
+		if services.BoxHasTrouble(box) {
+			a.logger.Warn("failed box preview blocked for social bot", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4245, "box_id", box.ID, "file_id", file.ID, "error", services.BoxTroubleReason(box))...)
+			http.Error(w, "box processing failed: "+services.BoxTroubleReason(box), http.StatusFailedDependency)
+			return
+		}
 		if shouldServeRawSocialMedia(file) {
 			a.serveFileContent(w, r, box, file, false)
 			a.logger.Info("media file served inline for social preview", withRequestLogAttrs(r, "source", "download", "severity", "user_activity", "code", 2009, "box_id", box.ID, "file_id", file.ID)...)
 			return
 		}
 	}
+	if file.ProcessingError != "" && !locked {
+		a.logger.Warn("failed file preview blocked", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4242, "box_id", box.ID, "file_id", file.ID, "error", file.ProcessingError)...)
+		http.Error(w, "file processing failed: "+file.ProcessingError, http.StatusFailedDependency)
+		return
+	}
+	if services.BoxHasTrouble(box) && !locked {
+		a.logger.Warn("failed box preview blocked", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4246, "box_id", box.ID, "file_id", file.ID, "error", services.BoxTroubleReason(box))...)
+		http.Error(w, "box processing failed: "+services.BoxTroubleReason(box), http.StatusFailedDependency)
+		return
+	}
 	view := a.fileView(box, file)
 	fileSize := helpers.FormatBytes(file.Size)
 	title := file.Name
@@ -306,6 +328,16 @@ func (a *App) DownloadFileContent(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "file is still processing", http.StatusAccepted)
 		return
 	}
+	if file.ProcessingError != "" {
+		a.logger.Warn("failed file download blocked", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4243, "box_id", box.ID, "file_id", file.ID, "error", file.ProcessingError)...)
+		http.Error(w, "file processing failed: "+file.ProcessingError, http.StatusFailedDependency)
+		return
+	}
+	if services.BoxHasTrouble(box) {
+		a.logger.Warn("failed box download blocked", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4247, "box_id", box.ID, "file_id", file.ID, "error", services.BoxTroubleReason(box))...)
+		http.Error(w, "box processing failed: "+services.BoxTroubleReason(box), http.StatusFailedDependency)
+		return
+	}

 	a.serveFileContent(w, r, box, file, r.URL.Query().Get("inline") != "1")
 	a.logger.Info("file content served", withRequestLogAttrs(r, "source", "download", "severity", "user_activity", "code", 2005, "box_id", box.ID, "file_id", file.ID, "attachment", r.URL.Query().Get("inline") != "1")...)
@@ -321,6 +353,11 @@ func (a *App) Thumbnail(w http.ResponseWriter, r *http.Request) {
 		a.servePlaceholderThumbnail(w, r)
 		return
 	}
+	if services.BoxHasTrouble(box) || services.FileHasTrouble(file) {
+		a.logger.Warn("thumbnail request skipped trouble file", withRequestLogAttrs(r, "source", "thumbnail", "severity", "warn", "code", 4110, "box_id", box.ID, "file_id", file.ID, "error", troubleReasonForLog(box, file))...)
+		a.servePlaceholderThumbnail(w, r)
+		return
+	}

 	object, err := a.uploadService.OpenThumbnailObject(r.Context(), box, file)
 	if err != nil {
@@ -363,6 +400,11 @@ func (a *App) VideoScenesPreview(w http.ResponseWriter, r *http.Request) {
 		a.servePlaceholderThumbnail(w, r)
 		return
 	}
+	if services.BoxHasTrouble(box) || services.FileHasTrouble(file) {
+		a.logger.Warn("video scenes preview request skipped trouble file", withRequestLogAttrs(r, "source", "thumbnail", "severity", "warn", "code", 4111, "box_id", box.ID, "file_id", file.ID, "error", troubleReasonForLog(box, file))...)
+		a.servePlaceholderThumbnail(w, r)
+		return
+	}

 	object, err := a.uploadService.OpenSceneThumbnailObject(r.Context(), box, file)
 	if err != nil {
@@ -400,6 +442,11 @@ func (a *App) ArchiveListing(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "password required", http.StatusUnauthorized)
 		return
 	}
+	if services.BoxHasTrouble(box) || services.FileHasTrouble(file) {
+		a.logger.Warn("archive listing request skipped trouble file", withRequestLogAttrs(r, "source", "thumbnail", "severity", "warn", "code", 4112, "box_id", box.ID, "file_id", file.ID, "error", troubleReasonForLog(box, file))...)
+		http.Error(w, "archive preview unavailable: file processing failed", http.StatusFailedDependency)
+		return
+	}

 	if strings.ToLower(filepath.Ext(file.ArchiveListing)) != ".json" {
 		if listing := a.generateMissingArchiveListingForRequest(r, box, file); listing != "" {
@@ -432,7 +479,7 @@ func (a *App) ArchiveListing(w http.ResponseWriter, r *http.Request) {
 }

 func (a *App) generateMissingThumbnailForRequest(r *http.Request, box services.Box, file services.File) string {
-	if file.Thumbnail != "" || !jobs.NeedsThumbnail(file) {
+	if file.Thumbnail != "" || !jobs.NeedsThumbnail(file) || services.BoxHasTrouble(box) || services.FileHasTrouble(file) || file.Processing {
 		return ""
 	}
 	thumbnail, err := jobs.GenerateThumbnailForFile(a.uploadService, box, file)
@@ -456,7 +503,7 @@ func (a *App) generateMissingThumbnailForRequest(r *http.Request, box services.B
 }

 func (a *App) generateMissingVideoScenesForRequest(r *http.Request, box services.Box, file services.File) string {
-	if file.SceneThumbnail != "" || !jobs.NeedsVideoScenes(file) {
+	if file.SceneThumbnail != "" || !jobs.NeedsVideoScenes(file) || services.BoxHasTrouble(box) || services.FileHasTrouble(file) || file.Processing {
 		return ""
 	}
 	scene, err := jobs.GenerateVideoScenesForFile(a.uploadService, box, file)
@@ -480,7 +527,7 @@ func (a *App) generateMissingVideoScenesForRequest(r *http.Request, box services
 }

 func (a *App) generateMissingArchiveListingForRequest(r *http.Request, box services.Box, file services.File) string {
-	if strings.ToLower(filepath.Ext(file.ArchiveListing)) == ".json" || !jobs.NeedsArchiveListing(file) {
+	if strings.ToLower(filepath.Ext(file.ArchiveListing)) == ".json" || !jobs.NeedsArchiveListing(file) || services.BoxHasTrouble(box) || services.FileHasTrouble(file) || file.Processing {
 		return ""
 	}
 	listing, err := jobs.GenerateArchiveListingForFile(a.uploadService, box, file)
@@ -504,6 +551,13 @@ func (a *App) generateMissingArchiveListingForRequest(r *http.Request, box servi
 	return listing
 }

+func troubleReasonForLog(box services.Box, file services.File) string {
+	if services.FileHasTrouble(file) {
+		return file.ProcessingError
+	}
+	return services.BoxTroubleReason(box)
+}
+
 // servePlaceholderThumbnail serves the fallback image with no-store so the
 // browser re-requests on the next load and picks up the real thumbnail as soon
 // as it has been generated.
@@ -651,6 +705,22 @@ func (a *App) DownloadZip(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "password required", http.StatusUnauthorized)
 		return
 	}
+	for _, file := range box.Files {
+		if file.Processing {
+			http.Error(w, "file is still processing", http.StatusAccepted)
+			return
+		}
+		if file.ProcessingError != "" {
+			a.logger.Warn("zip download blocked by failed file", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4244, "box_id", box.ID, "file_id", file.ID, "error", file.ProcessingError)...)
+			http.Error(w, "file processing failed: "+file.ProcessingError, http.StatusFailedDependency)
+			return
+		}
+	}
+	if services.BoxHasTrouble(box) {
+		a.logger.Warn("zip download blocked by failed box", withRequestLogAttrs(r, "source", "download", "severity", "warn", "code", 4248, "box_id", box.ID, "error", services.BoxTroubleReason(box))...)
+		http.Error(w, "box processing failed: "+services.BoxTroubleReason(box), http.StatusFailedDependency)
+		return
+	}

 	w.Header().Set("Content-Type", "application/zip")
 	w.Header().Set("Content-Disposition", contentDisposition("attachment", "warpbox-"+box.ID+".zip"))
@@ -685,9 +755,9 @@ func (a *App) fileViewWithReactions(box services.Box, file services.File, reacti
 		ThumbnailURL: fmt.Sprintf("/d/%s/thumb/%s", box.ID, file.ID),
 		SceneURL:     fmt.Sprintf("/d/%s/scene/%s", box.ID, file.ID),
 		ArchiveURL:   fmt.Sprintf("/d/%s/archive/%s", box.ID, file.ID),
-		HasThumbnail: file.Thumbnail != "" || jobs.NeedsThumbnail(file),
-		HasScene:     file.SceneThumbnail != "" || jobs.NeedsVideoScenes(file),
-		HasArchive:   file.ArchiveListing != "" || jobs.NeedsArchiveListing(file),
+		HasThumbnail: !services.BoxHasTrouble(box) && !services.FileHasTrouble(file) && (file.Thumbnail != "" || jobs.NeedsThumbnail(file)),
+		HasScene:     !services.BoxHasTrouble(box) && !services.FileHasTrouble(file) && (file.SceneThumbnail != "" || jobs.NeedsVideoScenes(file)),
+		HasArchive:   !services.BoxHasTrouble(box) && !services.FileHasTrouble(file) && (file.ArchiveListing != "" || jobs.NeedsArchiveListing(file)),
 		IconURL:      fileIconURL("standard", icon.Standard),
 		IconRetroURL: fileIconURL("retro", icon.Retro),
 		ReactURL:     fmt.Sprintf("/d/%s/f/%s/react", box.ID, file.ID),
@@ -695,6 +765,8 @@ func (a *App) fileViewWithReactions(box services.Box, file services.File, reacti
 		ReactionMore: reactionOverflowCount(reactionViews),
 		Reacted:      reacted,
 		Processing:   file.Processing,
+		Failed:       services.BoxHasTrouble(box) || services.FileHasTrouble(file),
+		Error:        troubleReasonForLog(box, file),
 	}
 }

--- a/backend/libs/handlers/pages.go
+++ b/backend/libs/handlers/pages.go
@@ -10,6 +10,7 @@ import (

 type homeData struct {
 	MaxUploadSize        string
+	MaxUploadBytes       int64
 	LimitSummary         string
 	Collections          []collectionView
 	IsAdmin              bool
@@ -57,7 +58,7 @@ func (a *App) Home(w http.ResponseWriter, r *http.Request) {
 		"actor", actor,
 		"user_id", user.ID,
 	)...)
-	maxUploadSize, limitSummary := a.homeUploadPolicyLabels(settings, user, loggedIn, isAdmin)
+	maxUploadSize, maxUploadBytes, limitSummary := a.homeUploadPolicyLabels(settings, user, loggedIn, isAdmin)
 	expiryOptions, defaultExpiry := a.homeExpiryOptions(settings, user, loggedIn, isAdmin)
 	a.renderPage(w, r, http.StatusOK, "home.html", web.PageData{
 		Title:        "Upload your files",
@@ -68,6 +69,7 @@ func (a *App) Home(w http.ResponseWriter, r *http.Request) {
 		CurrentUser:  currentUser,
 		Data: homeData{
 			MaxUploadSize:        maxUploadSize,
+			MaxUploadBytes:       maxUploadBytes,
 			LimitSummary:         limitSummary,
 			Collections:          collections,
 			IsAdmin:              isAdmin,
@@ -155,22 +157,25 @@ func expiryLabel(minutes int) string {
 	}
 }

-func (a *App) homeUploadPolicyLabels(settings services.UploadPolicySettings, user services.User, loggedIn, isAdmin bool) (string, string) {
+func (a *App) homeUploadPolicyLabels(settings services.UploadPolicySettings, user services.User, loggedIn, isAdmin bool) (string, int64, string) {
 	if isAdmin {
-		return "No file size limit", "Admin uploads bypass storage and daily caps."
+		return "No file size limit", -1, "Admin uploads bypass storage and daily caps."
 	}
 	if !loggedIn {
 		if !settings.AnonymousUploadsEnabled {
-			return "Anonymous uploads disabled", "Sign in to upload files."
+			return "Anonymous uploads disabled", 0, "Sign in to upload files."
 		}
-		return services.FormatMegabytesLabel(settings.AnonymousMaxUploadMB), "Daily anonymous cap: " + services.FormatMegabytesLabel(settings.AnonymousDailyUploadMB) + " per IP · " + strconv.Itoa(settings.AnonymousMaxDays) + " day max."
+		return services.FormatMegabytesLabel(settings.AnonymousMaxUploadMB), services.MegabytesToBytes(settings.AnonymousMaxUploadMB), "Daily anonymous cap: " + services.FormatMegabytesLabel(settings.AnonymousDailyUploadMB) + " per IP · " + strconv.Itoa(settings.AnonymousMaxDays) + " day max."
 	}
 	policy := a.settingsService.EffectivePolicyForUser(settings, user)
 	maxUpload := a.uploadService.MaxUploadSizeLabel()
+	maxUploadBytes := a.uploadService.MaxUploadSize()
 	if policy.MaxUploadMB < 0 {
 		maxUpload = "unlimited"
+		maxUploadBytes = -1
 	} else if policy.MaxUploadMB > 0 {
 		maxUpload = services.FormatMegabytesLabel(policy.MaxUploadMB)
+		maxUploadBytes = services.MegabytesToBytes(policy.MaxUploadMB)
 	}
 	quota := "unlimited"
 	if policy.StorageQuotaSet {
@@ -180,5 +185,5 @@ func (a *App) homeUploadPolicyLabels(settings services.UploadPolicySettings, use
 	if policy.MaxDays < 0 {
 		expiryLimit = "no expiry limit."
 	}
-	return maxUpload, "Daily cap: " + services.FormatMegabytesLabel(policy.DailyUploadMB) + " · Storage quota: " + quota + " · " + expiryLimit
+	return maxUpload, maxUploadBytes, "Daily cap: " + services.FormatMegabytesLabel(policy.DailyUploadMB) + " · Storage quota: " + quota + " · " + expiryLimit
 }
--- a/backend/libs/handlers/resumable.go
+++ b/backend/libs/handlers/resumable.go
@@ -180,7 +180,7 @@ func (a *App) CompleteResumableUpload(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if session.Status == services.ResumableStatusCompleted || session.Status == services.ResumableStatusProcessing {
+	if session.Status == services.ResumableStatusCompleted {
 		result, completed, err := a.uploadService.CompleteResumableSession(r.Context(), session.ID)
 		if err != nil {
 			a.logger.Warn("resumable upload completion replay failed", withRequestLogAttrs(r, "source", "user-upload", "severity", "warn", "code", 4004, "session_id", session.ID, "error", err.Error())...)
@@ -191,6 +191,17 @@ func (a *App) CompleteResumableUpload(w http.ResponseWriter, r *http.Request) {
 		helpers.WriteJSON(w, http.StatusOK, result)
 		return
 	}
+	if session.Status == services.ResumableStatusProcessing {
+		result, err := a.uploadService.FinalizeProcessingResumableSession(r.Context(), session.ID)
+		if err != nil {
+			a.logger.Warn("resumable upload completion replay failed", withRequestLogAttrs(r, "source", "user-upload", "severity", "warn", "code", 4004, "session_id", session.ID, "error", err.Error())...)
+			helpers.WriteJSONError(w, http.StatusBadRequest, err.Error())
+			return
+		}
+		a.logger.Info("resumable upload completion replayed", withRequestLogAttrs(r, "source", "user-upload", "severity", "user_activity", "code", 2004, "session_id", session.ID, "box_id", result.BoxID, "files", len(result.Files))...)
+		helpers.WriteJSON(w, http.StatusOK, result)
+		return
+	}
 	user, loggedIn, _ := a.currentUserWithAuthError(r)
 	isAdminUpload := loggedIn && user.Role == services.UserRoleAdmin
 	settings, policy, ok := a.loadUploadPolicyForAPI(w, r, user, loggedIn)
--- a/backend/libs/handlers/static.go
+++ b/backend/libs/handlers/static.go
@@ -34,6 +34,17 @@ func (a *App) EmojiAsset(w http.ResponseWriter, r *http.Request) {
 	http.ServeFile(w, r, path)
 }

+func (a *App) ServiceWorker(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/javascript; charset=utf-8")
+	w.Header().Set("Cache-Control", "public, max-age=86400")
+	w.Header().Set("Service-Worker-Allowed", "/")
+	http.ServeFile(w, r, filepath.Join(a.cfg.StaticDir, "js", "service-worker.js"))
+}
+
+func (a *App) ShareTargetFallback(w http.ResponseWriter, r *http.Request) {
+	http.Redirect(w, r, "/?share-target=unsupported", http.StatusSeeOther)
+}
+
 func setStaticCacheHeaders(w http.ResponseWriter, path string) {
 	ext := strings.ToLower(filepath.Ext(path))

--- a/backend/libs/handlers/static_test.go
+++ b/backend/libs/handlers/static_test.go
@@ -1,7 +1,11 @@
 package handlers

 import (
+	"encoding/json"
+	"net/http"
 	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"testing"
 )

@@ -24,3 +28,76 @@ func TestSetStaticCacheHeaders(t *testing.T) {
 		}
 	}
 }
+
+func TestWebManifestIncludesShareTarget(t *testing.T) {
+	data, err := os.ReadFile(filepath.Join("..", "..", "static", "site.webmanifest"))
+	if err != nil {
+		t.Fatalf("ReadFile returned error: %v", err)
+	}
+	var manifest struct {
+		ShareTarget struct {
+			Action  string `json:"action"`
+			Method  string `json:"method"`
+			EncType string `json:"enctype"`
+			Params  struct {
+				Title string `json:"title"`
+				Text  string `json:"text"`
+				URL   string `json:"url"`
+				Files []struct {
+					Name   string   `json:"name"`
+					Accept []string `json:"accept"`
+				} `json:"files"`
+			} `json:"params"`
+		} `json:"share_target"`
+	}
+	if err := json.Unmarshal(data, &manifest); err != nil {
+		t.Fatalf("json.Unmarshal returned error: %v", err)
+	}
+	if manifest.ShareTarget.Action != "/share-target" || manifest.ShareTarget.Method != "POST" || manifest.ShareTarget.EncType != "multipart/form-data" {
+		t.Fatalf("unexpected share_target config: %+v", manifest.ShareTarget)
+	}
+	if manifest.ShareTarget.Params.Title != "title" || manifest.ShareTarget.Params.Text != "text" || manifest.ShareTarget.Params.URL != "url" {
+		t.Fatalf("unexpected share_target params: %+v", manifest.ShareTarget.Params)
+	}
+	if len(manifest.ShareTarget.Params.Files) != 1 || manifest.ShareTarget.Params.Files[0].Name != "files" || len(manifest.ShareTarget.Params.Files[0].Accept) != 1 || manifest.ShareTarget.Params.Files[0].Accept[0] != "*/*" {
+		t.Fatalf("unexpected share_target files: %+v", manifest.ShareTarget.Params.Files)
+	}
+}
+
+func TestServiceWorkerServedFromRootScope(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	request := httptest.NewRequest(http.MethodGet, "/service-worker.js", nil)
+	response := httptest.NewRecorder()
+	app.ServiceWorker(response, request)
+
+	if response.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", response.Code, response.Body.String())
+	}
+	if got := response.Header().Get("Service-Worker-Allowed"); got != "/" {
+		t.Fatalf("Service-Worker-Allowed = %q, want /", got)
+	}
+	if got := response.Header().Get("Content-Type"); got != "text/javascript; charset=utf-8" {
+		t.Fatalf("Content-Type = %q", got)
+	}
+	if response.Body.Len() == 0 {
+		t.Fatalf("service worker body missing")
+	}
+}
+
+func TestShareTargetFallbackRedirectsHome(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	request := httptest.NewRequest(http.MethodPost, "/share-target", nil)
+	response := httptest.NewRecorder()
+	app.ShareTargetFallback(response, request)
+
+	if response.Code != http.StatusSeeOther {
+		t.Fatalf("status = %d, want %d", response.Code, http.StatusSeeOther)
+	}
+	if got := response.Header().Get("Location"); got != "/?share-target=unsupported" {
+		t.Fatalf("Location = %q", got)
+	}
+}
--- a/backend/libs/handlers/upload.go
+++ b/backend/libs/handlers/upload.go
@@ -53,6 +53,11 @@ func (a *App) Upload(w http.ResponseWriter, r *http.Request) {
 	}
 	if err := r.ParseMultipartForm(parseLimit); err != nil {
 		a.logger.Warn("upload form parse failed", withRequestLogAttrs(r, "source", "user-upload", "severity", "warn", "code", 4000, "user_id", user.ID, "error", err.Error())...)
+		var maxBytesErr *http.MaxBytesError
+		if errors.As(err, &maxBytesErr) {
+			helpers.WriteJSONError(w, http.StatusRequestEntityTooLarge, "upload exceeds the configured upload limit")
+			return
+		}
 		helpers.WriteJSONError(w, http.StatusBadRequest, "upload form could not be read")
 		return
 	}
@@ -244,7 +249,7 @@ func (a *App) checkUploadPolicyForSizes(r *http.Request, user services.User, log
 		maxBytes := services.MegabytesToBytes(policy.MaxUploadMB)
 		for _, fileSize := range fileSizes {
 			if fileSize > maxBytes {
-				return http.StatusRequestEntityTooLarge, "file exceeds upload size limit"
+				return http.StatusRequestEntityTooLarge, "file exceeds upload size limit of " + services.FormatMegabytesLabel(policy.MaxUploadMB)
 			}
 		}
 	}
--- a/backend/libs/handlers/upload_stage3_test.go
+++ b/backend/libs/handlers/upload_stage3_test.go
@@ -218,6 +218,44 @@ func TestFilePreviewPageIncludesPreviewMetadata(t *testing.T) {
 	}
 }

+func TestDownloadPageShowsProcessingFailure(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+	payload := uploadThroughApp(t, app)
+	box, err := app.uploadService.GetBox(payload.BoxID)
+	if err != nil {
+		t.Fatalf("GetBox returned error: %v", err)
+	}
+	box.Files[0].Processing = false
+	box.Files[0].ProcessingError = "Access Denied."
+	if err := app.uploadService.SaveBox(box); err != nil {
+		t.Fatalf("SaveBox returned error: %v", err)
+	}
+
+	request := httptest.NewRequest(http.MethodGet, "/d/"+payload.BoxID, nil)
+	request.SetPathValue("boxID", payload.BoxID)
+	response := httptest.NewRecorder()
+	app.DownloadPage(response, request)
+
+	if response.Code != http.StatusOK {
+		t.Fatalf("status = %d, body = %s", response.Code, response.Body.String())
+	}
+	body := response.Body.String()
+	for _, want := range []string{
+		"Upload processing failed",
+		"Access Denied.",
+		"is-failed",
+		"Failed",
+	} {
+		if !strings.Contains(body, want) {
+			t.Fatalf("download page missing %q: %s", want, body)
+		}
+	}
+	if strings.Contains(body, `data-download-url="/d/`+payload.BoxID+`/f/`+payload.Files[0].ID+`/download"`) {
+		t.Fatalf("failed file still exposed download context: %s", body)
+	}
+}
+
 func TestFileDownloadUsesOriginalFilename(t *testing.T) {
 	app, cleanup := newTestApp(t)
 	defer cleanup()