feat(files): MinIO fallback for stale S3 downloads (#152)

sync: gitea main (sortBy fix #18 + funding)

.env.example

@@ -25,3 +25,12 @@ ONLYOFFICE_PROJECT_ID=33
 # cmd/office TUI — optional Document Server for DOCX→HTML preview:
 # ONLYOFFICE_DOCS_URL=https://docs.example.com
 # ONLYOFFICE_DOCS_SECRET=
+
+# MinIO download fallback for the portal's stale AWS S3 consumer (older
+# Documents folders). When the portal redirects to amazonaws.com with access
+# key "minio" (403 InvalidAccessKeyId), files are fetched from the local MinIO
+# store instead. Without a key/secret the fallback is disabled.
+# MINIO_ENDPOINT=http://192.168.188.10:9000
+# MINIO_BUCKET=office
+# MINIO_ACCESS_KEY=
+# MINIO_SECRET_KEY=

.github/FUNDING.yml

@@ -0,0 +1,6 @@
+github: eSlider
+ko_fi: eslider
+liberapay: eslider
+patreon: eslider
+custom:
+  - https://polar.sh/eslider

.release-please-manifest.json

@@ -1,3 +1,3 @@
 {
-  ".": "0.16.0"
+  ".": "0.17.0"
 }

AGENTS.md

@@ -28,7 +28,7 @@ Canonical Go client for OnlyOffice Workspace (Projects + Calendar + CRM) and the
 - Prefer `ResponseObject` / `postFormObject` / `putFormObject` / `deleteObject` over hand-rolled `json.Unmarshal(responseField(...))` blocks — they exist for DRY, use them.
 - Domain split is by file, **not** by subpackage. Don't introduce `internal/` or `pkg/*` subpackages inside the library — it flattens the `*Client` call surface for a reason.
 - CLI commands follow **subject → verb** structure (`oo <subject> <verb>`), never `oo <verb>-<subject>`. Add new commands to the existing subject file if one fits; create a new `cmd/oo/<subject>.go` for a genuinely new domain.
-- **Documents for agents:** prefer Markdown in git; OnlyOffice UI is weak for `.md`/`.txt`. Use `oo docs put-md` (md→docx) and `oo docs put-txt` (txt→docx, preserves line breaks). `oo projects files dedupe PROJECT_ID` reports/removes duplicate stem|ext copies (`--apply`, `--cross`).
+- **Documents for agents:** prefer Markdown in git; OnlyOffice UI is weak for `.md`/`.txt`. Use `oo docs put-md` (md→docx) and `oo docs put-txt` (txt→docx, preserves line breaks). All upload paths default to **upsert** by `stem|ext` (`--replace`, default true); `--no-replace` fails on conflict; `--allow-duplicate` opts into raw OO append. `oo projects files dedupe PROJECT_ID` reports/removes duplicate stem|ext copies (`--apply`, `--cross`; includes project root folder).
 - Every table output goes through `printTable(headers, rows)`; every single-object through `printObject(v)`. Do not `fmt.Println` rows ad-hoc or the `--output json` flag breaks for that command.
 - No secrets in the repo; use `.env` (gitignored). Commit `.env.example` only.
 - Follow SemVer on tags; this repo is tagged at GitHub under `git@github.com:eSlider/go-onlyoffice.git`.

CHANGELOG.md

@@ -6,6 +6,18 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
 
+## [0.17.0](https://github.com/eSlider/go-onlyoffice/compare/v0.16.0...v0.17.0) (2026-08-31)
+
+
+### Features
+
+* **mailsync:** FetchMailFolder — integration-layer walk for ETL consumers ([35f0cb8](https://github.com/eSlider/go-onlyoffice/commit/35f0cb8d20076244141065c07e203e633bc3612a))
+
+
+### Bug Fixes
+
+* **files:** upsert uploads by default and dedupe project root ([24ca144](https://github.com/eSlider/go-onlyoffice/commit/24ca144b22abc5d056a5fd1ed9a1887f26a79d15))
+
 ## [0.16.0](https://github.com/eSlider/go-onlyoffice/compare/v0.15.0...v0.16.0) (2026-08-30)
 
 ### Features

cmd/oo/dav.go

@@ -0,0 +1,291 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	onlyoffice "github.com/eslider/go-onlyoffice"
+	"github.com/spf13/cobra"
+)
+
+func init() {
+	rootCmd.AddCommand(davCmd())
+}
+
+// davCmd exposes the Documents module through the same Dav calls that back
+// oo-webdav (ListDavFolder / MoveDavItems / CopyDavItems / DownloadDavFile).
+// MoveDavItems sends resolveType=Skip + holdResult=true, which the legacy
+// fileops/move call without those params silently ignores (200 without move).
+func davCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "dav",
+		Short: "Documents module by folder/file id (oo-webdav proven path)",
+	}
+	cmd.AddCommand(davLsCmd())
+	cmd.AddCommand(davMoveCmd())
+	cmd.AddCommand(davCopyCmd())
+	cmd.AddCommand(davMkdirCmd())
+	cmd.AddCommand(davRenameFileCmd())
+	cmd.AddCommand(davRenameFolderCmd())
+	cmd.AddCommand(davDownloadCmd())
+	cmd.AddCommand(davFileOpsCmd())
+	return cmd
+}
+
+func davLsCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "ls FOLDER_ID",
+		Short: "List a Documents folder (@root for virtual sections)",
+		Args:  cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			ctx := cmd.Context()
+			if args[0] == "@root" {
+				sections, err := c.ListDavSections(ctx)
+				if err != nil {
+					return err
+				}
+				rows := make([]map[string]any, 0, len(sections))
+				for _, s := range sections {
+					rows = append(rows, map[string]any{
+						"id":           s.ID,
+						"title":        s.Title,
+						"filesCount":   s.FilesCount,
+						"foldersCount": s.FoldersCount,
+					})
+				}
+				printTable([]string{"id", "title", "filesCount", "foldersCount"}, rows)
+				return nil
+			}
+			l, err := c.ListDavFolder(ctx, args[0])
+			if err != nil {
+				return err
+			}
+			if outputFormat == "json" {
+				folders := make([]map[string]any, 0, len(l.Folders))
+				for _, f := range l.Folders {
+					folders = append(folders, map[string]any{
+						"id":           f.ID,
+						"title":        f.Title,
+						"filesCount":   f.FilesCount,
+						"foldersCount": f.FoldersCount,
+					})
+				}
+				files := make([]map[string]any, 0, len(l.Files))
+				for _, f := range l.Files {
+					files = append(files, map[string]any{
+						"id":      f.ID,
+						"title":   f.Title,
+						"size":    f.Size,
+						"updated": f.Updated,
+					})
+				}
+				printObject(map[string]any{"folders": folders, "files": files})
+				return nil
+			}
+			if len(l.Folders) > 0 {
+				frows := make([]map[string]any, 0, len(l.Folders))
+				for _, f := range l.Folders {
+					frows = append(frows, map[string]any{
+						"id":           f.ID,
+						"title":        f.Title,
+						"filesCount":   f.FilesCount,
+						"foldersCount": f.FoldersCount,
+					})
+				}
+				if outputFormat == "table" {
+					fmt.Println("folders:")
+				}
+				printTable([]string{"id", "title", "filesCount", "foldersCount"}, frows)
+			}
+			rows := make([]map[string]any, 0, len(l.Files))
+			for _, f := range l.Files {
+				rows = append(rows, map[string]any{
+					"id":      f.ID,
+					"title":   f.Title,
+					"size":    f.Size,
+					"updated": f.Updated,
+				})
+			}
+			if outputFormat == "table" {
+				fmt.Println("files:")
+			}
+			printTable([]string{"id", "title", "size", "updated"}, rows)
+			return nil
+		},
+	}
+	return cmd
+}
+
+func davMoveCmd() *cobra.Command {
+	var folderIDs []string
+	cmd := &cobra.Command{
+		Use:   "move DEST_FOLDER_ID FILE_ID [FILE_ID...]",
+		Short: "Move file(s) into a Documents folder (resolveType=Skip, holdResult)",
+		Args:  cobra.MinimumNArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			if err := c.MoveDavItems(cmd.Context(), folderIDs, args[1:], args[0]); err != nil {
+				return err
+			}
+			printObject(map[string]any{"moved_files": args[1:], "moved_folders": folderIDs, "dest": args[0]})
+			return nil
+		},
+	}
+	cmd.Flags().StringSliceVar(&folderIDs, "folders", nil, "folder ids to move along with the files")
+	return cmd
+}
+
+func davCopyCmd() *cobra.Command {
+	var folderIDs []string
+	cmd := &cobra.Command{
+		Use:   "copy DEST_FOLDER_ID FILE_ID [FILE_ID...]",
+		Short: "Copy file(s) into a Documents folder (conflictResolveType=Skip)",
+		Args:  cobra.MinimumNArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			if err := c.CopyDavItems(cmd.Context(), folderIDs, args[1:], args[0]); err != nil {
+				return err
+			}
+			printObject(map[string]any{"copied_files": args[1:], "copied_folders": folderIDs, "dest": args[0]})
+			return nil
+		},
+	}
+	cmd.Flags().StringSliceVar(&folderIDs, "folders", nil, "folder ids to copy along with the files")
+	return cmd
+}
+
+func davMkdirCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "mkdir PARENT_FOLDER_ID TITLE",
+		Short: "Create a subfolder in Documents",
+		Args:  cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			f, err := c.CreateDavFolder(cmd.Context(), args[0], args[1])
+			if err != nil {
+				return err
+			}
+			printObject(map[string]any{"id": f.ID, "title": f.Title, "parent": args[0]})
+			return nil
+		},
+	}
+}
+
+func davRenameFileCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "rename-file FILE_ID NEW_TITLE",
+		Short: "Rename a Documents file (include extension in NEW_TITLE)",
+		Args:  cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			if err := c.RenameDavFile(cmd.Context(), args[0], args[1]); err != nil {
+				return err
+			}
+			printObject(map[string]any{"id": args[0], "title": args[1]})
+			return nil
+		},
+	}
+}
+
+func davRenameFolderCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "rename-folder FOLDER_ID NEW_TITLE",
+		Short: "Rename a Documents folder",
+		Args:  cobra.ExactArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			if err := c.RenameDavFolder(cmd.Context(), args[0], args[1]); err != nil {
+				return err
+			}
+			printObject(map[string]any{"id": args[0], "title": args[1]})
+			return nil
+		},
+	}
+}
+
+func davDownloadCmd() *cobra.Command {
+	var to string
+	cmd := &cobra.Command{
+		Use:   "download FILE_ID",
+		Short: "Download Documents file bytes (default path: ./<title>)",
+		Args:  cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			ctx := cmd.Context()
+			f, err := c.GetFile(ctx, args[0])
+			if err != nil {
+				return err
+			}
+			path := to
+			if path == "" {
+				path = onlyoffice.SafeLocalFileName(onlyoffice.FileEntryTitle(f))
+			}
+			out, err := os.Create(path)
+			if err != nil {
+				return err
+			}
+			defer out.Close()
+			n, err := c.DownloadDavFile(ctx, args[0], out)
+			if err != nil {
+				_ = os.Remove(path)
+				return err
+			}
+			printObject(map[string]any{"path": path, "bytes": n})
+			return nil
+		},
+	}
+	cmd.Flags().StringVar(&to, "to", "", "output path (default: ./<server title>)")
+	return cmd
+}
+
+func davFileOpsCmd() *cobra.Command {
+	return &cobra.Command{
+		Use:   "fileops",
+		Short: "List active file operations (move/copy status polling)",
+		Args:  cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			c, err := newOO(cmd)
+			if err != nil {
+				return err
+			}
+			ops, err := c.ListFileOps(cmd.Context())
+			if err != nil {
+				return err
+			}
+			rows := make([]map[string]any, 0, len(ops))
+			for _, op := range ops {
+				rows = append(rows, map[string]any{
+					"id":        fmt.Sprint(op["id"]),
+					"operation": fmt.Sprint(op["operation"]),
+					"progress":  fmt.Sprint(op["progress"]),
+					"finished":  fmt.Sprint(op["finished"]),
+					"error":     fmt.Sprint(op["error"]),
+				})
+			}
+			printTable([]string{"id", "operation", "progress", "finished", "error"}, rows)
+			return nil
+		},
+	}
+}

cmd/oo/docs.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -423,44 +424,28 @@ func docsPutMDCmd() *cobra.Command {
 				}
 			}
 			ctx := cmd.Context()
-			var ent *onlyoffice.FileEntry
+			ent, deleted, err := uploadProjectDoc(ctx, c, pid, docxPath, folderID, replace)
-			var deleted []int
-			if folderID != "" {
-				if replace {
-					ent, deleted, err = c.UploadToFolderReplacing(ctx, folderID, docxPath)
-				} else {
-					ent, err = c.UploadToFolder(ctx, folderID, docxPath)
-				}
 			if err != nil {
 				return err
 			}
 			obj := map[string]any{
 				"project_id": pid,
-					"folder_id":  folderID,
 				"md":         mdPath,
 				"uploaded":   fileEntryToMap(ent),
 			}
+			if folderID != "" {
+				obj["folder_id"] = folderID
+			}
 			if len(deleted) > 0 {
 				obj["replaced_file_ids"] = deleted
 			}
 			printObject(obj)
 			return nil
-			}
-			ent, err = c.UploadProjectFile(ctx, pid, docxPath)
-			if err != nil {
-				return err
-			}
-			printObject(map[string]any{
-				"project_id": pid,
-				"md":         mdPath,
-				"uploaded":   fileEntryToMap(ent),
-			})
-			return nil
 		},
 	}
 	cmd.Flags().StringVar(&folderID, "folder", "", "Documents folder id (default: project root)")
 	cmd.Flags().StringVar(&keepLocalDOCX, "keep-docx", "", "also write the generated DOCX to this local path")
-	cmd.Flags().BoolVar(&replace, "replace", true, "delete same-stem files in folder before upload (put-md upsert)")
+	cmd.Flags().BoolVar(&replace, "replace", true, "replace same stem|ext before upload (default); false = fail if name taken")
 	return cmd
 }
 
@@ -503,44 +488,28 @@ func docsPutTxtCmd() *cobra.Command {
 				}
 			}
 			ctx := cmd.Context()
-			var ent *onlyoffice.FileEntry
+			ent, deleted, err := uploadProjectDoc(ctx, c, pid, docxPath, folderID, replace)
-			var deleted []int
-			if folderID != "" {
-				if replace {
-					ent, deleted, err = c.UploadToFolderReplacing(ctx, folderID, docxPath)
-				} else {
-					ent, err = c.UploadToFolder(ctx, folderID, docxPath)
-				}
 			if err != nil {
 				return err
 			}
 			obj := map[string]any{
 				"project_id": pid,
 				"txt":        txtPath,
-					"folder_id":  folderID,
 				"uploaded":   fileEntryToMap(ent),
 			}
+			if folderID != "" {
+				obj["folder_id"] = folderID
+			}
 			if len(deleted) > 0 {
 				obj["replaced_file_ids"] = deleted
 			}
 			printObject(obj)
 			return nil
-			}
-			ent, err = c.UploadProjectFile(ctx, pid, docxPath)
-			if err != nil {
-				return err
-			}
-			printObject(map[string]any{
-				"project_id": pid,
-				"txt":        txtPath,
-				"uploaded":   fileEntryToMap(ent),
-			})
-			return nil
 		},
 	}
 	cmd.Flags().StringVar(&folderID, "folder", "", "Documents folder id (default: project root)")
 	cmd.Flags().StringVar(&keepLocalDOCX, "keep-docx", "", "also write the generated DOCX to this local path")
-	cmd.Flags().BoolVar(&replace, "replace", true, "delete same-stem files in folder before upload (put-txt upsert)")
+	cmd.Flags().BoolVar(&replace, "replace", true, "replace same stem|ext before upload (default); false = fail if name taken")
 	return cmd
 }
 
@@ -618,21 +587,7 @@ formulas (SUM/AVG, cross-sheet refs, named inputs) via --template, or upload an
 			}
 
 			ctx := cmd.Context()
-			var ent *onlyoffice.FileEntry
+			ent, deleted, err := uploadProjectDoc(ctx, c, pid, xlsxPath, folderID, replace)
-			var deleted []int
-			if folderID != "" {
-				if replace {
-					ent, deleted, err = c.UploadToFolderReplacing(ctx, folderID, xlsxPath)
-				} else {
-					ent, err = c.UploadToFolder(ctx, folderID, xlsxPath)
-				}
-			} else {
-				if replace {
-					ent, deleted, err = c.UploadProjectFileReplacing(ctx, pid, xlsxPath)
-				} else {
-					ent, err = c.UploadProjectFile(ctx, pid, xlsxPath)
-				}
-			}
 			if err != nil {
 				return err
 			}
@@ -655,6 +610,25 @@ formulas (SUM/AVG, cross-sheet refs, named inputs) via --template, or upload an
 	cmd.Flags().StringVar(&template, "template", "", "built-in workbook template (cutover-portugal)")
 	cmd.Flags().StringVar(&title, "title", "", "upload file name when using --template")
 	cmd.Flags().StringVar(&keepLocal, "keep-xlsx", "", "also write generated/uploaded bytes to this local path")
-	cmd.Flags().BoolVar(&replace, "replace", true, "delete same-stem files before upload")
+	cmd.Flags().BoolVar(&replace, "replace", true, "replace same stem|ext before upload (default); false = fail if name taken")
 	return cmd
 }
+
+// uploadProjectDoc upserts (--replace, default) or no-clobbers into project/folder Documents.
+func uploadProjectDoc(ctx context.Context, c *onlyoffice.Client, pid, localPath, folderID string, replace bool) (*onlyoffice.FileEntry, []int, error) {
+	if folderID != "" {
+		if replace {
+			return c.UploadToFolderReplacing(ctx, folderID, localPath)
+		}
+		if err := c.AssertNoFileConflict(ctx, folderID, localPath); err != nil {
+			return nil, nil, err
+		}
+		ent, err := c.UploadToFolder(ctx, folderID, localPath)
+		return ent, nil, err
+	}
+	if replace {
+		return c.UploadProjectFileReplacing(ctx, pid, localPath)
+	}
+	ent, err := c.UploadProjectFileNoClobber(ctx, pid, localPath)
+	return ent, nil, err
+}

cmd/oo/main.go

@@ -16,6 +16,7 @@
 //	oo mails         accounts | folders | list | get | download-attachment | draft | attach | draft-invoice | delete
 //	oo invoices      list | get | create | update | pdf | pdf-cleanup | status | delete | items …
 //	oo docs          tools | convert | ocr | as-md | put-md
+//	oo dav           ls | move | copy | mkdir | rename-file | rename-folder | download | fileops
 //
 // CRM association rules: docs/crm-associations.md
 //

cmd/oo/projects_files.go

@@ -107,9 +107,12 @@ func prjFilesListCmd() *cobra.Command {
 }
 
 func prjFilesUploadCmd() *cobra.Command {
-	return &cobra.Command{
+	var replace, allowDuplicate bool
+	cmd := &cobra.Command{
 		Use:   "upload PROJECT_ID LOCAL_PATH [LOCAL_PATH...]",
-		Short: "Upload file(s) into the project's Documents folder",
+		Short: "Upload file(s) into the project's Documents folder (upsert by stem|ext)",
+		Long: `Default: replace an existing file with the same logical name (stem|ext), like cp overwrite.
+Pass --no-replace to fail when the name is taken; --allow-duplicate to always create a new file id.`,
 		Args: cobra.MinimumNArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			c, err := newOO(cmd)
@@ -118,15 +121,31 @@ func prjFilesUploadCmd() *cobra.Command {
 			}
 			pid := args[0]
 			for _, p := range args[1:] {
-				entry, err := c.UploadProjectFile(cmd.Context(), pid, p)
+				var entry *onlyoffice.FileEntry
+				var deleted []int
+				switch {
+				case allowDuplicate:
+					entry, err = c.UploadProjectFile(cmd.Context(), pid, p)
+				case replace:
+					entry, deleted, err = c.UploadProjectFileReplacing(cmd.Context(), pid, p)
+				default:
+					entry, err = c.UploadProjectFileNoClobber(cmd.Context(), pid, p)
+				}
 				if err != nil {
 					return err
 				}
-				printObject(fileEntryToMap(entry))
+				obj := fileEntryToMap(entry)
+				if len(deleted) > 0 {
+					obj["replaced_file_ids"] = deleted
+				}
+				printObject(obj)
 			}
 			return nil
 		},
 	}
+	cmd.Flags().BoolVar(&replace, "replace", true, "replace same stem|ext in project folder (default)")
+	cmd.Flags().BoolVar(&allowDuplicate, "allow-duplicate", false, "always create a new file even when the name exists")
+	return cmd
 }
 
 func prjFilesDownloadCmd() *cobra.Command {

crm.go

@@ -15,10 +15,15 @@ import (
 )
 
 // ListContacts returns a page of CRM contacts and the total count.
+// sortBy=id is always set: OnlyOffice filter.json without an explicit sort
+// order is non-deterministic on large contact sets, so a paged walk
+// (ListAllContacts, ListContactsByTag, FindCompany, FindPerson) can skip or
+// duplicate contacts across page boundaries.
 func (c *Client) ListContacts(ctx context.Context, count, startIndex int, search string) ([]map[string]any, int, error) {
 	q := url.Values{}
 	q.Set("count", strconv.Itoa(count))
 	q.Set("startIndex", strconv.Itoa(startIndex))
+	q.Set("sortBy", "id")
 	if search != "" {
 		q.Set("filterValue", search)
 	}
@@ -243,6 +248,24 @@ func (c *Client) DeleteContact(ctx context.Context, contactID string) (map[strin
 	return c.deleteObject(ctx, fmt.Sprintf("/api/2.0/crm/contact/%s.json", url.PathEscape(contactID)))
 }
 
+// UpdateContactName renames a CRM company contact displayName.
+// Uses the company endpoint (person names go through /crm/contact/person/{id}).
+func (c *Client) UpdateContactName(ctx context.Context, contactID, newName string) (map[string]any, error) {
+	body := map[string]any{
+		"displayName": newName,
+		"companyName": newName,
+		"isCompany":   true,
+	}
+	out, err := c.putJSONObject(ctx, fmt.Sprintf("/api/2.0/crm/contact/company/%s.json", url.PathEscape(contactID)), body)
+	if err != nil {
+		return out, err
+	}
+	if fresh, gerr := c.GetContact(ctx, contactID); gerr == nil && fresh != nil {
+		out = fresh
+	}
+	return out, nil
+}
+
 // ListContactTags returns all CRM contact tags (title + relativeItemsCount).
 func (c *Client) ListContactTags(ctx context.Context) ([]map[string]any, error) {
 	return c.ResponseArray(ctx, "/api/2.0/crm/contact/tag.json")
@@ -288,6 +311,7 @@ func (c *Client) ListContactsByTag(ctx context.Context, tagName string, count, s
 	q.Set("count", strconv.Itoa(count))
 	q.Set("startIndex", strconv.Itoa(startIndex))
 	q.Set("tags", tagName)
+	q.Set("sortBy", "id")
 	raw, err := c.getJSON(ctx, "/api/2.0/crm/contact/filter.json?"+q.Encode())
 	if err != nil {
 		return nil, 0, err
@@ -717,6 +741,11 @@ func (c *Client) DeleteCRMTask(ctx context.Context, id string) (map[string]any,
 	return c.deleteObject(ctx, fmt.Sprintf("/api/2.0/crm/task/%s.json", url.PathEscape(id)))
 }
 
+// CloseCRMTask closes (completes) a CRM task via the task close endpoint.
+func (c *Client) CloseCRMTask(ctx context.Context, id string) (map[string]any, error) {
+	return c.putFormObject(ctx, fmt.Sprintf("/api/2.0/crm/task/%s/close.json", url.PathEscape(id)), url.Values{})
+}
+
 // ListTaskCategories returns CRM task categories.
 func (c *Client) ListTaskCategories(ctx context.Context) ([]map[string]any, error) {
 	return c.ResponseArray(ctx, "/api/2.0/crm/task/category.json")

files.go

@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"net/http"
 	"net/url"
 	"path"
 	"strconv"
@@ -321,11 +320,21 @@ func (c *Client) MoveFiles(ctx context.Context, destFolderID int, fileIDs []int)
 		"folderIds":    []int{},
 		"fileIds":      fileIDs,
 		"destFolderId": destFolderID,
+		"resolveType":  "Skip",
+		"holdResult":   true,
 	}
 	out, err := c.putJSONObject(ctx, "/api/2.0/files/fileops/move.json", body)
 	if err != nil {
 		out, err = c.putJSONObject(ctx, "/api/2.0/files/fileops/move", body)
 	}
+	if err != nil {
+		return nil, err
+	}
+	if raw, merr := json.Marshal(out); merr == nil {
+		if ferr := fileopsError(raw); ferr != nil {
+			return nil, ferr
+		}
+	}
 	return out, err
 }
 
@@ -346,6 +355,24 @@ func (c *Client) UploadToFolder(ctx context.Context, folderID, localPath string)
 	return decodeResponseFileEntry(raw)
 }
 
+// UpdateFile uploads a new version of an existing file (same id, name and
+// folder). It does not delete and does not create a second file.
+func (c *Client) UpdateFile(ctx context.Context, fileID, localPath string) (*FileEntry, error) {
+	if fileID == "" || localPath == "" {
+		return nil, fmt.Errorf("file id and local path are required")
+	}
+	uploadPath := fmt.Sprintf("/api/2.0/files/%s/update", url.PathEscape(fileID))
+	raw, err := c.uploadMultipart(ctx, uploadPath, "file", localPath)
+	if err != nil {
+		uploadPath = fmt.Sprintf("/api/2.0/files/%s/update.json", url.PathEscape(fileID))
+		raw, err = c.uploadMultipart(ctx, uploadPath, "file", localPath)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return decodeResponseFileEntry(raw)
+}
+
 // FileFolderID returns the parent folder id string for a file entry, if known.
 func FileFolderID(f *FileEntry) string {
 	if f == nil || f.FolderID == nil {
@@ -355,36 +382,15 @@ func FileFolderID(f *FileEntry) string {
 }
 
 // DownloadFile streams file bytes from the file's viewUrl using the same auth
-// as API calls. Writes into dst.
+// as API calls. Writes into dst. When the portal serves the file from its stale
+// AWS S3 consumer, the bytes are fetched from the local MinIO store instead
+// (see storage_fallback.go).
 func (c *Client) DownloadFile(ctx context.Context, fileID string, dst io.Writer) (int64, error) {
 	f, err := c.GetFile(ctx, fileID)
 	if err != nil {
 		return 0, err
 	}
-	if f.ViewURL == nil || *f.ViewURL == "" {
+	return c.downloadFileEntry(ctx, f, dst)
-		return 0, fmt.Errorf("file %s has no viewUrl", fileID)
-	}
-	downloadURL := c.resolveAPIURL(*f.ViewURL)
-	auth, err := c.authHeader()
-	if err != nil {
-		return 0, err
-	}
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
-	if err != nil {
-		return 0, err
-	}
-	req.Header.Set("Authorization", auth)
-	resp, err := c.client.Do(req)
-	if err != nil {
-		return 0, err
-	}
-	defer resp.Body.Close()
-	if resp.StatusCode >= 400 {
-		b, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
-		return 0, fmt.Errorf("GET viewUrl: %d %s", resp.StatusCode, truncate(string(b), 400))
-	}
-	n, err := io.Copy(dst, resp.Body)
-	return n, err
 }
 
 func (c *Client) resolveAPIURL(ref string) string {

files_dedupe.go

@@ -2,6 +2,7 @@ package onlyoffice
 
 import (
 	"context"
+	"encoding/json"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -310,25 +311,70 @@ func (c *Client) DeleteFilesByDedupKey(ctx context.Context, folderID, stem, ext
 	return ids, nil
 }
 
+// mergeProjectRootForDedupe includes projectFolder files in dedupe scans. OO often lists
+// root documents only in pf.Files while pf.Folders is empty.
+func mergeProjectRootForDedupe(rootID string, folders []*FolderEntry, filesByFolder map[string][]*FileEntry, rootFiles []*FileEntry) ([]*FolderEntry, map[string][]*FileEntry) {
+	if rootID == "" {
+		return folders, filesByFolder
+	}
+	if filesByFolder == nil {
+		filesByFolder = map[string][]*FileEntry{}
+	}
+	for _, folder := range folders {
+		if folder != nil && folder.ID != nil && folder.ID.String() == rootID {
+			if len(rootFiles) > 0 {
+				filesByFolder[rootID] = rootFiles
+			}
+			return folders, filesByFolder
+		}
+	}
+	if len(rootFiles) == 0 {
+		return folders, filesByFolder
+	}
+	id := json.Number(rootID)
+	title := "(project root)"
+	folders = append(folders, &FolderEntry{ID: &id, Title: &title})
+	filesByFolder[rootID] = rootFiles
+	return folders, filesByFolder
+}
+
 // DedupeProject scans project folders and optionally deletes duplicates.
 func (c *Client) DedupeProject(ctx context.Context, projectID string, opts DedupOptions, apply bool) ([]DedupGroup, []int, error) {
 	pf, err := c.GetProjectFiles(ctx, projectID)
 	if err != nil {
 		return nil, nil, err
 	}
-	filesByFolder := make(map[string][]*FileEntry, len(pf.Folders))
+	rootID, err := c.projectFolderID(ctx, projectID)
+	if err != nil {
+		return nil, nil, err
+	}
+	var rootFiles []*FileEntry
+	if rootID != "" {
+		rootFiles, err = c.FolderFiles(ctx, rootID)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+	filesByFolder := make(map[string][]*FileEntry, len(pf.Folders)+1)
+	folders := make([]*FolderEntry, 0, len(pf.Folders)+1)
 	for _, folder := range pf.Folders {
 		if folder == nil || folder.ID == nil {
 			continue
 		}
 		fid := folder.ID.String()
+		if fid == rootID {
+			filesByFolder[fid] = rootFiles
+		} else {
 			files, err := c.FolderFiles(ctx, fid)
 			if err != nil {
 				return nil, nil, err
 			}
 			filesByFolder[fid] = files
 		}
-	groups := FindProjectDuplicates(pf.Folders, filesByFolder, opts)
+		folders = append(folders, folder)
+	}
+	folders, filesByFolder = mergeProjectRootForDedupe(rootID, folders, filesByFolder, rootFiles)
+	groups := FindProjectDuplicates(folders, filesByFolder, opts)
 	if !apply || len(groups) == 0 {
 		return groups, nil, nil
 	}

files_dedupe_test.go

@@ -64,6 +64,26 @@ func TestCrossFolderPrefersNonTrash(t *testing.T) {
 	}
 }
 
+func TestMergeProjectRootForDedupe(t *testing.T) {
+	old := &FileEntry{ID: jsonNum("1"), Title: strPtr("a.docx"), FileExst: strPtr(".docx")}
+	newer := &FileEntry{ID: jsonNum("2"), Title: strPtr("a.docx"), FileExst: strPtr(".docx")}
+	rootFiles := []*FileEntry{old, newer}
+	folders, byFolder := mergeProjectRootForDedupe("489", nil, nil, rootFiles)
+	if len(folders) != 1 || folders[0].ID.String() != "489" {
+		t.Fatalf("folders=%+v", folders)
+	}
+	if len(byFolder["489"]) != 2 {
+		t.Fatalf("root files=%d", len(byFolder["489"]))
+	}
+	groups := findWithinFolderDuplicates([]ProjectFolderFile{
+		{FolderID: "489", FolderTitle: "(project root)", File: old},
+		{FolderID: "489", FolderTitle: "(project root)", File: newer},
+	})
+	if len(groups) != 1 {
+		t.Fatalf("groups=%d", len(groups))
+	}
+}
+
 func TestIsTrashFolderTitle(t *testing.T) {
 	if !IsTrashFolderTitle("_trash-md") {
 		t.Fatal("expected trash")

files_stem.go

@@ -3,10 +3,15 @@ package onlyoffice
 import (
 	"context"
 	"encoding/json"
+	"errors"
+	"fmt"
 	"path/filepath"
 	"strings"
 )
 
+// ErrFileExists is returned when --no-replace / no-clobber upload hits an existing stem|ext.
+var ErrFileExists = errors.New("onlyoffice: file already exists in folder (use replace or delete first)")
+
 // FileEntryStem returns the logical basename without duplicated extensions.
 // OO often stores title="foo.docx" and fileExst=".docx" (UI shows foo.docx.docx).
 func FileEntryStem(f *FileEntry) string {
@@ -116,6 +121,38 @@ func (c *Client) DeleteFilesByStem(ctx context.Context, folderID, stem string) (
 	return ids, nil
 }
 
+// AssertNoFileConflict reports ErrFileExists when localPath stem|ext is already in folderID.
+func (c *Client) AssertNoFileConflict(ctx context.Context, folderID, localPath string) error {
+	files, err := c.FolderFiles(ctx, folderID)
+	if err != nil {
+		return err
+	}
+	stem := UploadStemFromLocal(localPath)
+	ext := UploadExtFromLocal(localPath)
+	matches := FindFilesByDedupKey(files, stem, ext)
+	if len(matches) == 0 {
+		return nil
+	}
+	ids := make([]string, 0, len(matches))
+	for _, f := range matches {
+		ids = append(ids, fmt.Sprintf("%d", FileEntryNumericID(f)))
+	}
+	return fmt.Errorf("%w: %s%s in folder %s (existing file ids: %s)",
+		ErrFileExists, stem, ext, folderID, strings.Join(ids, ", "))
+}
+
+// UploadProjectFileNoClobber uploads only when stem|ext is not already in the project folder.
+func (c *Client) UploadProjectFileNoClobber(ctx context.Context, projectID, localPath string) (*FileEntry, error) {
+	folderID, err := c.projectFolderID(ctx, projectID)
+	if err != nil {
+		return nil, err
+	}
+	if err := c.AssertNoFileConflict(ctx, folderID, localPath); err != nil {
+		return nil, err
+	}
+	return c.UploadProjectFile(ctx, projectID, localPath)
+}
+
 // UploadToFolderReplacing deletes same stem+ext files then uploads localPath.
 func (c *Client) UploadToFolderReplacing(ctx context.Context, folderID, localPath string) (*FileEntry, []int, error) {
 	stem := UploadStemFromLocal(localPath)

files_webdav.go

@@ -144,28 +144,86 @@ func (c *Client) RenameDavFile(ctx context.Context, id, title string) error {
 }
 
 // MoveDavItems moves the given folders and/or files into destFolderID.
+// The fileops API answers 200 with per-operation error strings even when
+// nothing moves (e.g. missing permission), so the response is parsed and the
+// first operation error is returned instead of a silent nil.
 func (c *Client) MoveDavItems(ctx context.Context, folderIDs, fileIDs []string, destFolderID string) error {
-	_, err := c.putJSON(ctx, "/api/2.0/files/fileops/move", map[string]any{
+	raw, err := c.putJSON(ctx, "/api/2.0/files/fileops/move", map[string]any{
 		"folderIds":    nums(folderIDs),
 		"fileIds":      nums(fileIDs),
 		"destFolderId": num(destFolderID),
 		"resolveType":  "Skip",
 		"holdResult":   true,
 	})
+	if err != nil {
 		return err
 	}
+	return fileopsError(raw)
+}
 
 // CopyDavItems copies the given folders and/or files into destFolderID.
+// Per-operation errors are surfaced like in MoveDavItems.
 func (c *Client) CopyDavItems(ctx context.Context, folderIDs, fileIDs []string, destFolderID string) error {
-	_, err := c.putJSON(ctx, "/api/2.0/files/fileops/copy", map[string]any{
+	raw, err := c.putJSON(ctx, "/api/2.0/files/fileops/copy", map[string]any{
 		"folderIds":           nums(folderIDs),
 		"fileIds":             nums(fileIDs),
 		"destFolderId":        num(destFolderID),
 		"conflictResolveType": "Skip",
 		"deleteAfter":         true,
 	})
+	if err != nil {
 		return err
 	}
+	return fileopsError(raw)
+}
+
+// ListFileOps returns the currently active file operations
+// (GET /api/2.0/files/fileops) for status polling.
+func (c *Client) ListFileOps(ctx context.Context) ([]map[string]any, error) {
+	raw, err := c.getJSON(ctx, "/api/2.0/files/fileops")
+	if err != nil {
+		return nil, err
+	}
+	resp, err := responseField(raw, "response")
+	if err != nil {
+		return nil, err
+	}
+	if len(resp) == 0 || string(resp) == "null" {
+		return nil, nil
+	}
+	var ops []map[string]any
+	if err := json.Unmarshal(resp, &ops); err != nil {
+		return nil, err
+	}
+	return ops, nil
+}
+
+// fileopsError extracts per-operation "error" strings from a fileops/move or
+// fileops/copy envelope. A 200 with error entries means nothing moved.
+func fileopsError(raw json.RawMessage) error {
+	resp, err := responseField(raw, "response")
+	if err != nil {
+		return err
+	}
+	var ops []struct {
+		Error    *string `json:"error"`
+		Finished *bool   `json:"finished"`
+		Progress *int    `json:"progress"`
+	}
+	if err := json.Unmarshal(resp, &ops); err != nil {
+		return nil // not an operations envelope — nothing to report
+	}
+	var errs []string
+	for _, op := range ops {
+		if op.Error != nil && *op.Error != "" {
+			errs = append(errs, *op.Error)
+		}
+	}
+	if len(errs) > 0 {
+		return fmt.Errorf("onlyoffice: fileops: %s", strings.Join(errs, "; "))
+	}
+	return nil
+}
 
 // DeleteDavItems deletes the given folders and/or files.
 func (c *Client) DeleteDavItems(ctx context.Context, folderIDs, fileIDs []string) error {
@@ -201,34 +259,10 @@ func (c *Client) UploadDavFile(ctx context.Context, folderID, fileName string, s
 	return env.Response, nil
 }
 
-// DownloadDavFile streams the file identified by id to w, returning bytes copied.
+// DownloadDavFile streams the file identified by id to w, returning bytes
+// copied. It shares the MinIO stale-S3 fallback with DownloadFile.
 func (c *Client) DownloadDavFile(ctx context.Context, id string, w io.Writer) (int64, error) {
-	file, err := c.GetFile(ctx, id)
+	return c.DownloadFile(ctx, id, w)
-	if err != nil {
-		return 0, err
-	}
-	if file.ViewURL == nil || *file.ViewURL == "" {
-		return 0, fmt.Errorf("onlyoffice: file %s has no viewUrl", id)
-	}
-	u := c.resolveAPIURL(*file.ViewURL)
-	auth, err := c.authHeader()
-	if err != nil {
-		return 0, err
-	}
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
-	if err != nil {
-		return 0, err
-	}
-	req.Header.Set("Authorization", auth)
-	resp, err := c.client.Do(req)
-	if err != nil {
-		return 0, err
-	}
-	defer resp.Body.Close()
-	if resp.StatusCode >= 400 {
-		return 0, fmt.Errorf("onlyoffice: download: %d", resp.StatusCode)
-	}
-	return io.Copy(w, resp.Body)
 }
 
 // --- internal helpers -------------------------------------------------------

go.mod

@@ -4,6 +4,7 @@ go 1.25.0
 
 require (
 	github.com/JohannesKaufmann/html-to-markdown/v2 v2.5.2
+	github.com/aws/aws-sdk-go-v2 v1.41.1
 	github.com/charmbracelet/bubbles v0.18.0
 	github.com/charmbracelet/bubbletea v0.25.0
 	github.com/charmbracelet/glamour v0.8.0
@@ -26,6 +27,7 @@ require (
 	github.com/JohannesKaufmann/dom v0.3.1 // indirect
 	github.com/alecthomas/chroma/v2 v2.14.0 // indirect
 	github.com/atotto/clipboard v0.1.4 // indirect
+	github.com/aws/smithy-go v1.24.0 // indirect
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/aymerick/douceur v0.2.0 // indirect
 	github.com/containerd/console v1.0.4-0.20230313162750-1ae8d489ac81 // indirect

go.sum

@@ -10,6 +10,10 @@ github.com/alecthomas/repr v0.4.0 h1:GhI2A8MACjfegCPVq9f1FLvIBS+DrQ2KQBFZP1iFzXc
 github.com/alecthomas/repr v0.4.0/go.mod h1:Fr0507jx4eOXV7AlPV6AVZLYrLIuIeSOWtW57eE/O/4=
 github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z4=
 github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
+github.com/aws/aws-sdk-go-v2 v1.41.1 h1:ABlyEARCDLN034NhxlRUSZr4l71mh+T5KAeGh6cerhU=
+github.com/aws/aws-sdk-go-v2 v1.41.1/go.mod h1:MayyLB8y+buD9hZqkCW3kX1AKq07Y5pXxtgB+rRFhz0=
+github.com/aws/smithy-go v1.24.0 h1:LpilSUItNPFr1eY85RYgTIg5eIEPtvFbskaFcmmIUnk=
+github.com/aws/smithy-go v1.24.0/go.mod h1:LEj2LM3rBRQJxPZTB4KuzZkaZYnZPnvgIhb4pu07mx0=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
 github.com/aymanbagabas/go-udiff v0.2.0 h1:TK0fH4MteXUDspT88n8CKzvK0X9O2xu9yQjWpi6yML8=

mailsync.go

@@ -0,0 +1,175 @@
+package onlyoffice
+
+// High-level mail folder walk for ETL consumers (2dph brain mail-ingest,
+// cv tools). This is the "integration layer" half of reusing the canonical
+// client instead of private per-project OOClient copies: the caller gets a
+// single hydrated stream instead of hand-rolling list → get → download
+// against the raw API.
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+	"time"
+)
+
+// MailSyncAttachment is one attachment of a hydrated mail message.
+type MailSyncAttachment struct {
+	ID   string // id accepted by Client.DownloadMailAttachment
+	Name string
+	Size int64
+	Body []byte // non-nil only when MailSyncOptions.FetchBodies is set
+}
+
+// MailSyncMessage is a hydrated mail message for sync pipelines.
+type MailSyncMessage struct {
+	ID             int64
+	Folder         int
+	Subject        string
+	From           string // raw RFC 5322 header value ("Name" <addr>)
+	Date           time.Time
+	IsNew          bool
+	HasAttachments bool
+	Attachments    []MailSyncAttachment
+}
+
+// MailSyncOptions controls FetchMailFolder.
+type MailSyncOptions struct {
+	Limit       int  // max messages to hydrate; 0 = whole folder
+	StartIndex  int  // skip this many messages before collecting
+	FetchBodies bool // eagerly download attachment bytes
+}
+
+// FetchMailFolder walks a mail folder page by page and hydrates every
+// message: list → get → (optionally) download attachments. It is the single
+// entry point sync pipelines need on top of the mail API.
+//
+// Messages are returned in API order (newest first). The folder walk stops
+// at the first empty or short page.
+func (c *Client) FetchMailFolder(ctx context.Context, folderID int, opts MailSyncOptions) ([]MailSyncMessage, error) {
+	if folderID <= 0 {
+		folderID = MailFolderInbox
+	}
+	var out []MailSyncMessage
+	skipped := 0
+	for page := 1; ; page++ {
+		batch, err := c.ResponseArray(ctx,
+			mailMessagesPath(MailMessagesFilter{Folder: folderID}, page, mailMessagesPageSize))
+		if err != nil {
+			return nil, fmt.Errorf("FetchMailFolder: %w", err)
+		}
+		if len(batch) == 0 {
+			break
+		}
+		for _, raw := range batch {
+			if skipped < opts.StartIndex {
+				skipped++
+				continue
+			}
+			msg, err := c.hydrateMailMessage(ctx, raw, opts)
+			if err != nil {
+				return nil, err
+			}
+			out = append(out, *msg)
+			if opts.Limit > 0 && len(out) >= opts.Limit {
+				return out, nil
+			}
+		}
+		if len(batch) < mailMessagesPageSize {
+			break
+		}
+	}
+	return out, nil
+}
+
+// hydrateMailMessage converts one raw API message into a MailSyncMessage,
+// fetching the full record when the list item does not carry the attachment
+// metadata, and downloading bodies when requested.
+func (c *Client) hydrateMailMessage(ctx context.Context, m map[string]any, opts MailSyncOptions) (*MailSyncMessage, error) {
+	msg := &MailSyncMessage{
+		ID:      Int64FromMap(m, "id"),
+		Folder:  int(Int64FromMap(m, "folder")),
+		Subject: stringFromMap(m, "subject"),
+		From:    stringFromMap(m, "from"),
+		IsNew:   boolFromMap(m, "isNew") == "true",
+	}
+	msg.Date = parseMailTime(stringFromMap(m, "date"))
+
+	atts, _ := m["attachments"].([]any)
+	hasFlag := boolFromMap(m, "hasAttachments") == "true"
+	if hasFlag && len(atts) == 0 {
+		// List items may omit the attachment array; pull the full record.
+		full, err := c.GetMailMessage(ctx, strconv.FormatInt(msg.ID, 10))
+		if err != nil {
+			return nil, fmt.Errorf("FetchMailFolder: hydrate message %d: %w", msg.ID, err)
+		}
+		atts, _ = full["attachments"].([]any)
+	}
+	for _, a := range atts {
+		am, ok := a.(map[string]any)
+		if !ok {
+			continue
+		}
+		att := MailSyncAttachment{
+			ID:   mailAttachmentID(am),
+			Name: stringFromMap(am, "fileName"),
+			Size: Int64FromMap(am, "size"),
+		}
+		if att.Name == "" {
+			att.Name = stringFromMap(am, "name")
+		}
+		if att.ID != "" {
+			msg.Attachments = append(msg.Attachments, att)
+		}
+	}
+	msg.HasAttachments = hasFlag || len(msg.Attachments) > 0
+
+	if opts.FetchBodies {
+		for i := range msg.Attachments {
+			body, err := c.DownloadMailAttachment(ctx, msg.Attachments[i].ID)
+			if err != nil {
+				return nil, fmt.Errorf("FetchMailFolder: message %d attachment %q: %w",
+					msg.ID, msg.Attachments[i].Name, err)
+			}
+			msg.Attachments[i].Body = body
+		}
+	}
+	return msg, nil
+}
+
+// mailAttachmentID extracts the download id from an attachment object.
+// OnlyOffice variants use "id", "fileId" or "attachmentId".
+func mailAttachmentID(am map[string]any) string {
+	for _, key := range []string{"id", "fileId", "attachmentId"} {
+		switch v := am[key].(type) {
+		case string:
+			if s := v; s != "" {
+				return s
+			}
+		case float64:
+			if n := int64(v); n != 0 {
+				return strconv.FormatInt(n, 10)
+			}
+		case int64:
+			if v != 0 {
+				return strconv.FormatInt(v, 10)
+			}
+		}
+	}
+	return ""
+}
+
+// parseMailTime accepts the OnlyOffice timestamp shapes seen in the wild:
+// RFC3339 (with any fractional digits) and second-precision local form.
+func parseMailTime(s string) time.Time {
+	if s == "" {
+		return time.Time{}
+	}
+	if t, err := time.Parse(time.RFC3339, s); err == nil {
+		return t
+	}
+	if t, err := time.Parse("2006-01-02T15:04:05", s); err == nil {
+		return t
+	}
+	return time.Time{}
+}

mailsync_test.go

@@ -0,0 +1,137 @@
+package onlyoffice
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+// mailsSyncMock serves a two-page inbox: page 1 has two list items (one
+// reporting hasAttachments but omitting the attachment array, forcing the
+// full-record fetch), page 2 is empty. The full record for message 102
+// carries one attachment whose body is served by download.ashx.
+func newMailSyncTestServer(t *testing.T, msgsPage1 string) *httptest.Server {
+	t.Helper()
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.URL.Path == "/api/2.0/authentication.json":
+			http.SetCookie(w, &http.Cookie{Name: "sessionid", Value: "abc", Path: "/"})
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"response":{"token":"tok","expires":"2099-01-01T00:00:00.0000000+00:00"}}`))
+
+		case r.URL.Path == "/api/2.0/mail/messages":
+			w.Header().Set("Content-Type", "application/json")
+			if r.URL.Query().Get("page") > "1" {
+				_, _ = w.Write([]byte(`{"response":[]}`))
+				return
+			}
+			_, _ = w.Write([]byte(`{"response":[` + msgsPage1 + `]}`))
+
+		case r.URL.Path == "/api/2.0/mail/messages/102":
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write([]byte(`{"response":{
+				"id":102,"subject":"Full record","from":"\"A\" <a@b.com>",
+				"date":"2026-08-22T10:15:00+02:00","folder":1,"isNew":false,
+				"hasAttachments":true,
+				"attachments":[{"id":77,"fileName":"report.pdf","size":3}]}}`))
+
+		case r.URL.Path == "/addons/mail/httphandlers/download.ashx":
+			if r.Header.Get("Cookie") == "" {
+				http.Error(w, "missing cookie", http.StatusUnauthorized)
+				return
+			}
+			_, _ = w.Write([]byte("PDF!"))
+
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+}
+
+func TestFetchMailFolderHydratesAndDownloads(t *testing.T) {
+	page1 := `
+		{"id":101,"subject":"Plain","from":"x@y.z","date":"2026-08-21T09:00:00Z",
+		 "folder":1,"isNew":true,"hasAttachments":false},
+		{"id":102,"subject":"With attachment (list item)","from":"a@b.com",
+		 "date":"2026-08-22T10:15:00+02:00","folder":1,"isNew":false,
+		 "hasAttachments":true}
+	`
+	srv := newMailSyncTestServer(t, page1)
+	defer srv.Close()
+
+	c := NewClient(Credentials{Url: srv.URL, User: "u", Password: "p"})
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	msgs, err := c.FetchMailFolder(ctx, MailFolderInbox, MailSyncOptions{FetchBodies: true})
+	if err != nil {
+		t.Fatalf("FetchMailFolder: %v", err)
+	}
+	if len(msgs) != 2 {
+		t.Fatalf("got %d messages, want 2", len(msgs))
+	}
+
+	first := msgs[0]
+	if first.ID != 101 || first.Subject != "Plain" || !first.IsNew {
+		t.Fatalf("first = %+v", first)
+	}
+	if first.Date.IsZero() || first.Date.Year() != 2026 {
+		t.Fatalf("first date = %v", first.Date)
+	}
+	if first.HasAttachments {
+		t.Fatalf("first should have no attachments")
+	}
+
+	second := msgs[1]
+	if !second.HasAttachments || len(second.Attachments) != 1 {
+		t.Fatalf("second attachments = %+v", second.Attachments)
+	}
+	att := second.Attachments[0]
+	if att.ID != "77" || att.Name != "report.pdf" || att.Size != 3 || string(att.Body) != "PDF!" {
+		t.Fatalf("attachment = %+v", att)
+	}
+	if second.Date.Location() == time.UTC && second.Date.Hour() != 8 {
+		t.Fatalf("second date = %v (want +02:00 offset preserved)", second.Date)
+	}
+}
+
+func TestFetchMailFolderLimitAndStartIndex(t *testing.T) {
+	var items []string
+	for i := 1; i <= 5; i++ {
+		items = append(items, `{"id":`+string(rune('0'+i))+`,"subject":"m`+string(rune('0'+i))+`",
+			"from":"x@y.z","date":"2026-08-20T00:00:00Z","folder":1}`)
+	}
+	srv := newMailSyncTestServer(t, strings.Join(items, ","))
+	defer srv.Close()
+
+	c := NewClient(Credentials{Url: srv.URL, User: "u", Password: "p"})
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	got, err := c.FetchMailFolder(ctx, MailFolderInbox, MailSyncOptions{StartIndex: 1, Limit: 2})
+	if err != nil {
+		t.Fatalf("FetchMailFolder: %v", err)
+	}
+	if len(got) != 2 {
+		t.Fatalf("got %d messages, want 2", len(got))
+	}
+	if got[0].ID != 2 || got[1].ID != 3 {
+		t.Fatalf("ids = %d,%d want 2,3", got[0].ID, got[1].ID)
+	}
+}
+
+func TestParseMailTime(t *testing.T) {
+	fractions := "2026-08-22T10:15:00.1234567+02:00"
+	if parseMailTime(fractions).IsZero() {
+		t.Fatalf("RFC3339 with 7-digit fraction failed: %q", fractions)
+	}
+	if parseMailTime("2026-08-22T10:15:00").IsZero() {
+		t.Fatal("second-precision form failed")
+	}
+	if !parseMailTime("").IsZero() || !parseMailTime("garbage").IsZero() {
+		t.Fatal("unparseable input must yield zero time")
+	}
+}

storage_fallback.go

@@ -0,0 +1,200 @@
+package onlyoffice
+
+// MinIO download fallback for the portal's stale AWS S3 consumer.
+//
+// On the Fibu EDL portal some older Documents files live in S3/MinIO, but the
+// portal's storage consumer still points at s3.us-east-1.amazonaws.com with
+// access key "minio". Downloads of those files answer 403 InvalidAccessKeyId.
+// The bytes are present in the local MinIO store under a deterministic object
+// key, so the client retries the GET there.
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/signer/v4"
+)
+
+const (
+	defaultMinioEndpoint = "http://192.168.188.10:9000"
+	defaultMinioBucket   = "office"
+	minioRegion          = "us-east-1"
+)
+
+// minioObjectKey is the fallback object key layout the portal's S3 consumer
+// writes for Documents files: 00/00/01/files/folder_<folderId>/file_<fileId>/v1/content.pdf.
+// Prefer minioObjectKeyFromURL: the portal stores all files below its storage
+// root folder, which is not the API folderId returned by GetFile.
+func minioObjectKey(fileID, folderID string) string {
+	return "00/00/01/files/folder_" + folderID + "/file_" + fileID + "/v1/content.pdf"
+}
+
+// minioObjectKeyFromURL extracts the object key from an S3 download URL. Path
+// style URLs (bucket as first path segment) have that segment removed; virtual
+// host style URLs are returned as-is. This is authoritative: the portal signs
+// the exact key, so no folder-id guessing is needed.
+func minioObjectKeyFromURL(rawURL, bucket string) (string, bool) {
+	u, err := url.Parse(strings.TrimSpace(rawURL))
+	if err != nil || u.Path == "" {
+		return "", false
+	}
+	segs := strings.Split(strings.Trim(u.Path, "/"), "/")
+	// Path-style URLs carry the bucket as leading segment; the portal's S3
+	// consumer can emit it twice (serviceurl already includes the bucket), so
+	// strip every leading segment equal to the bucket.
+	for len(segs) > 0 && bucket != "" && segs[0] == bucket {
+		segs = segs[1:]
+	}
+	if len(segs) == 0 {
+		return "", false
+	}
+	for _, s := range segs {
+		if s == "" || s == "." || s == ".." {
+			return "", false
+		}
+	}
+	return strings.Join(segs, "/"), true
+}
+
+// isStaleS3Redirect reports whether a download landed on the portal's stale AWS
+// S3 consumer. Such responses either carry an S3 InvalidAccessKeyId XML body or
+// point at amazonaws.com with the "minio" access key id in the query.
+func isStaleS3Redirect(rawURL string, body []byte) bool {
+	if strings.Contains(strings.ToLower(string(body)), "invalidaccesskeyid") {
+		return true
+	}
+	u, err := url.Parse(strings.TrimSpace(rawURL))
+	if err != nil || u.Host == "" {
+		return false
+	}
+	host := strings.ToLower(u.Host)
+	if !strings.Contains(host, "amazonaws.com") {
+		return false
+	}
+	q := strings.ToLower(u.RawQuery)
+	return strings.Contains(q, "accesskeyid=minio") || strings.Contains(q, "x-amz-credential=minio")
+}
+
+// minioConfig is the runtime configuration for the local MinIO fallback.
+type minioConfig struct {
+	Endpoint  string
+	Bucket    string
+	AccessKey string
+	SecretKey string
+}
+
+// loadMinioConfig reads the fallback configuration from the environment.
+// Secrets are never defaulted; without access/secret keys the fallback is off.
+func loadMinioConfig() minioConfig {
+	return minioConfig{
+		Endpoint:  strings.TrimRight(firstNonEmpty(os.Getenv("MINIO_ENDPOINT"), defaultMinioEndpoint), "/"),
+		Bucket:    firstNonEmpty(os.Getenv("MINIO_BUCKET"), defaultMinioBucket),
+		AccessKey: os.Getenv("MINIO_ACCESS_KEY"),
+		SecretKey: os.Getenv("MINIO_SECRET_KEY"),
+	}
+}
+
+// downloadFileEntry downloads f's bytes to dst. It transparently falls back to
+// the local MinIO store when the portal redirects the download to its stale AWS
+// S3 consumer.
+func (c *Client) downloadFileEntry(ctx context.Context, f *FileEntry, dst io.Writer) (int64, error) {
+	if f == nil {
+		return 0, fmt.Errorf("onlyoffice: download: nil file entry")
+	}
+	if f.ViewURL == nil || *f.ViewURL == "" {
+		return 0, fmt.Errorf("onlyoffice: file has no viewUrl")
+	}
+	downloadURL := c.resolveAPIURL(*f.ViewURL)
+	auth, err := c.authHeader()
+	if err != nil {
+		return 0, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
+	if err != nil {
+		return 0, err
+	}
+	req.Header.Set("Authorization", auth)
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return 0, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 400 {
+		b, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+		finalURL := downloadURL
+		if resp.Request != nil && resp.Request.URL != nil {
+			finalURL = resp.Request.URL.String()
+		}
+		if isStaleS3Redirect(finalURL, b) {
+			key, ok := minioObjectKeyFromURL(finalURL, loadMinioConfig().Bucket)
+			if !ok {
+				fileID := ""
+				if f.ID != nil {
+					fileID = f.ID.String()
+				}
+				key = minioObjectKey(fileID, FileFolderID(f))
+			}
+			n, merr := c.downloadFromMinio(ctx, key, dst)
+			if merr == nil {
+				return n, nil
+			}
+			return 0, fmt.Errorf("GET viewUrl: %d (stale S3) and minio fallback: %w", resp.StatusCode, merr)
+		}
+		return 0, fmt.Errorf("GET viewUrl: %d %s", resp.StatusCode, truncate(string(b), 400))
+	}
+	return io.Copy(dst, resp.Body)
+}
+
+// downloadFromMinio streams objectKey from the configured MinIO bucket.
+func (c *Client) downloadFromMinio(ctx context.Context, objectKey string, dst io.Writer) (int64, error) {
+	if objectKey == "" {
+		return 0, fmt.Errorf("onlyoffice: minio fallback: empty object key")
+	}
+	cfg := loadMinioConfig()
+	if cfg.AccessKey == "" || cfg.SecretKey == "" {
+		return 0, fmt.Errorf("onlyoffice: minio fallback: MINIO_ACCESS_KEY/MINIO_SECRET_KEY not set")
+	}
+	base, err := url.Parse(cfg.Endpoint)
+	if err != nil || base.Host == "" {
+		return 0, fmt.Errorf("onlyoffice: minio fallback: bad MINIO_ENDPOINT %q", cfg.Endpoint)
+	}
+	u := *base
+	u.Path = "/" + cfg.Bucket + "/" + objectKey
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
+	if err != nil {
+		return 0, err
+	}
+	if err := signMinioRequest(ctx, cfg, req); err != nil {
+		return 0, err
+	}
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return 0, fmt.Errorf("onlyoffice: minio fallback: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 400 {
+		b, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+		return 0, fmt.Errorf("onlyoffice: minio fallback: %d %s", resp.StatusCode, truncate(string(b), 300))
+	}
+	return io.Copy(dst, resp.Body)
+}
+
+// signMinioRequest signs req with AWS Signature V4 for the S3 service.
+func signMinioRequest(ctx context.Context, cfg minioConfig, req *http.Request) error {
+	sum := sha256.Sum256(nil)
+	creds := aws.Credentials{AccessKeyID: cfg.AccessKey, SecretAccessKey: cfg.SecretKey}
+	if err := v4.NewSigner().SignHTTP(ctx, creds, req, hex.EncodeToString(sum[:]), "s3", minioRegion, time.Now()); err != nil {
+		return fmt.Errorf("onlyoffice: minio fallback: sign: %w", err)
+	}
+	return nil
+}

storage_fallback_integration_test.go

@@ -0,0 +1,45 @@
+//go:build integration
+
+package onlyoffice
+
+import (
+	"context"
+	"io"
+	"os"
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestIntegrationMinioFallback downloads known stale-S3 files through the local
+// MinIO fallback. Requires ONLYOFFICE_URL/USER/PASS (as all integration tests),
+// MINIO_ACCESS_KEY/MINIO_SECRET_KEY and MINIO_TEST_FILE_IDS="3785,3859,3666";
+// skips when any of those are missing.
+func TestIntegrationMinioFallback(t *testing.T) {
+	if os.Getenv("MINIO_ACCESS_KEY") == "" || os.Getenv("MINIO_SECRET_KEY") == "" {
+		t.Skip("MINIO_ACCESS_KEY/MINIO_SECRET_KEY not set — skipping integration test")
+	}
+	raw := strings.TrimSpace(os.Getenv("MINIO_TEST_FILE_IDS"))
+	if raw == "" {
+		t.Skip("MINIO_TEST_FILE_IDS not set — skipping integration test")
+	}
+	c := liveClient(t)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	defer cancel()
+	for _, id := range strings.Split(raw, ",") {
+		id = strings.TrimSpace(id)
+		if id == "" {
+			continue
+		}
+		n, err := c.DownloadFile(ctx, id, io.Discard)
+		if err != nil {
+			t.Errorf("DownloadFile(%s): %v", id, err)
+			continue
+		}
+		if n == 0 {
+			t.Errorf("DownloadFile(%s): 0 bytes", id)
+		} else {
+			t.Logf("DownloadFile(%s): %d bytes", id, n)
+		}
+	}
+}

storage_fallback_test.go

@@ -0,0 +1,219 @@
+package onlyoffice
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestMinioObjectKey(t *testing.T) {
+	cases := []struct {
+		fileID   string
+		folderID string
+		want     string
+	}{
+		{"3785", "652", "00/00/01/files/folder_652/file_3785/v1/content.pdf"},
+		{"1", "2", "00/00/01/files/folder_2/file_1/v1/content.pdf"},
+		{"3666", "4000", "00/00/01/files/folder_4000/file_3666/v1/content.pdf"},
+	}
+	for _, tc := range cases {
+		if got := minioObjectKey(tc.fileID, tc.folderID); got != tc.want {
+			t.Errorf("minioObjectKey(%q, %q) = %q, want %q", tc.fileID, tc.folderID, got, tc.want)
+		}
+	}
+}
+
+func TestMinioObjectKeyFromURL(t *testing.T) {
+	cases := []struct {
+		name   string
+		url    string
+		bucket string
+		want   string
+		ok     bool
+	}{
+		{
+			name:   "path style drops bucket segment",
+			url:    "https://s3.us-east-1.amazonaws.com/office/00/00/01/files/folder_4000/file_3785/v1/content.pdf?AWSAccessKeyId=minio",
+			bucket: "office",
+			want:   "00/00/01/files/folder_4000/file_3785/v1/content.pdf",
+			ok:     true,
+		},
+		{
+			name:   "doubled bucket segment (portal serviceurl includes bucket)",
+			url:    "https://s3.us-east-1.amazonaws.com/office/office/00/00/01/files/folder_4000/file_3785/v1/content.pdf?AWSAccessKeyId=minio",
+			bucket: "office",
+			want:   "00/00/01/files/folder_4000/file_3785/v1/content.pdf",
+			ok:     true,
+		},
+		{
+			name:   "virtual host style keeps path",
+			url:    "https://office.s3.us-east-1.amazonaws.com/00/00/01/files/folder_4000/file_3785/v1/content.pdf",
+			bucket: "office",
+			want:   "00/00/01/files/folder_4000/file_3785/v1/content.pdf",
+			ok:     true,
+		},
+		{
+			name:   "foreign first segment kept",
+			url:    "https://example.com/other/file_1/v1/content.pdf",
+			bucket: "office",
+			want:   "other/file_1/v1/content.pdf",
+			ok:     true,
+		},
+		{name: "empty path", url: "https://example.com", bucket: "office", ok: false},
+		{name: "traversal", url: "https://example.com/office/../etc/passwd", bucket: "office", ok: false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			got, ok := minioObjectKeyFromURL(tc.url, tc.bucket)
+			if ok != tc.ok || got != tc.want {
+				t.Errorf("minioObjectKeyFromURL(%q, %q) = (%q, %v), want (%q, %v)", tc.url, tc.bucket, got, ok, tc.want, tc.ok)
+			}
+		})
+	}
+}
+
+func TestIsStaleS3Redirect(t *testing.T) {
+	cases := []struct {
+		name string
+		url  string
+		body []byte
+		want bool
+	}{
+		{
+			name: "aws redirect with minio access key",
+			url:  "https://s3.us-east-1.amazonaws.com/office/x/file_1?AWSAccessKeyId=minio&Expires=1",
+			want: true,
+		},
+		{
+			name: "aws redirect with minio x-amz-credential",
+			url:  "https://office.s3.us-east-1.amazonaws.com/00/00/01/files/folder_1/file_1?X-Amz-Credential=minio%2F20260914",
+			want: true,
+		},
+		{
+			name: "invalid access key xml body",
+			url:  "https://portal.internal/download/1",
+			body: []byte(`<?xml version="1.0"?><Error><Code>InvalidAccessKeyId</Code><AWSAccessKeyId>minio</AWSAccessKeyId></Error>`),
+			want: true,
+		},
+		{
+			name: "regular pdf from portal",
+			url:  "https://portal.internal/download/1",
+			body: []byte("%PDF-1.7 data"),
+			want: false,
+		},
+		{
+			name: "aws redirect with foreign key",
+			url:  "https://s3.us-east-1.amazonaws.com/office/x?AWSAccessKeyId=other",
+			want: false,
+		},
+		{
+			name: "amazonaws in path but foreign host",
+			url:  "https://example.com/amazonaws.com/file?AWSAccessKeyId=minio",
+			want: false,
+		},
+		{
+			name: "empty",
+			want: false,
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := isStaleS3Redirect(tc.url, tc.body); got != tc.want {
+				t.Errorf("isStaleS3Redirect(%q, %q) = %v, want %v", tc.url, tc.body, got, tc.want)
+			}
+		})
+	}
+}
+
+const staleS3Body = `<?xml version="1.0" encoding="UTF-8"?>` +
+	`<Error><Code>InvalidAccessKeyId</Code>` +
+	`<Message>The AWS Access Key Id you provided does not exist in our records.</Message>` +
+	`<AWSAccessKeyId>minio</AWSAccessKeyId></Error>`
+
+func TestDownloadFileMinioFallback(t *testing.T) {
+	const payload = "PDFDATA-3785"
+
+	portal := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api/2.0/files/file/3785.json":
+			w.Header().Set("Content-Type", "application/json")
+			io.WriteString(w, `{"response":{"id":3785,"title":"04.pdf","folderId":655,"viewUrl":"/download/3785"}}`)
+		case "/download/3785":
+			http.Redirect(w, r, "/office/00/00/01/files/folder_4000/file_3785/v1/content.pdf?AWSAccessKeyId=minio", http.StatusTemporaryRedirect)
+		case "/office/00/00/01/files/folder_4000/file_3785/v1/content.pdf":
+			w.WriteHeader(http.StatusForbidden)
+			io.WriteString(w, staleS3Body)
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer portal.Close()
+
+	var minioPath, minioAuth string
+	minio := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		minioPath, minioAuth = r.URL.Path, r.Header.Get("Authorization")
+		io.WriteString(w, payload)
+	}))
+	defer minio.Close()
+
+	t.Setenv("MINIO_ENDPOINT", minio.URL)
+	t.Setenv("MINIO_BUCKET", "office")
+	t.Setenv("MINIO_ACCESS_KEY", "testkey")
+	t.Setenv("MINIO_SECRET_KEY", "testsecret")
+
+	c := &Client{
+		client:      portal.Client(),
+		credentials: &Credentials{Url: portal.URL},
+		token:       &Token{Value: "Bearer test", Expires: Time(time.Now().Add(time.Hour))},
+	}
+
+	var buf bytes.Buffer
+	n, err := c.DownloadFile(context.Background(), "3785", &buf)
+	if err != nil {
+		t.Fatalf("DownloadFile: %v", err)
+	}
+	if n != int64(len(payload)) || buf.String() != payload {
+		t.Fatalf("got %d bytes %q, want %d bytes %q", n, buf.String(), len(payload), payload)
+	}
+	if want := "/office/00/00/01/files/folder_4000/file_3785/v1/content.pdf"; minioPath != want {
+		t.Errorf("minio path = %q, want %q", minioPath, want)
+	}
+	if !strings.HasPrefix(minioAuth, "AWS4-HMAC-SHA256") {
+		t.Errorf("minio request not SigV4-signed; Authorization=%q", minioAuth)
+	}
+}
+
+func TestDownloadFileMinioFallbackWithoutCreds(t *testing.T) {
+	portal := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/api/2.0/files/file/3785.json":
+			io.WriteString(w, `{"response":{"id":3785,"folderId":652,"viewUrl":"/download/3785"}}`)
+		default:
+			w.WriteHeader(http.StatusForbidden)
+			io.WriteString(w, staleS3Body)
+		}
+	}))
+	defer portal.Close()
+
+	t.Setenv("MINIO_ACCESS_KEY", "")
+	t.Setenv("MINIO_SECRET_KEY", "")
+
+	c := &Client{
+		client:      portal.Client(),
+		credentials: &Credentials{Url: portal.URL},
+		token:       &Token{Value: "Bearer test", Expires: Time(time.Now().Add(time.Hour))},
+	}
+
+	_, err := c.DownloadFile(context.Background(), "3785", io.Discard)
+	if err == nil {
+		t.Fatal("expected error without minio credentials")
+	}
+	if !strings.Contains(err.Error(), "MINIO_ACCESS_KEY/MINIO_SECRET_KEY not set") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}