Testing this with 8.5.5 (39213) on macOS.

• Dragging a file from one browser window to the other works as expected as [documented] (https://docs.cyberduck.io/cyberduck/browser/#move-or-duplicate-files-and-folders) ¹
• Choosing ⌘-X and ⌘-V works as expected
• Choosing ⌘-X and ⌘-V works as expected
• Choosing ⌘-C and ⌘-V will do the copying by a download & upload as there is no copy operation in SFTP.

Thanks for the link to the documentation!

• Note on docs: FTP, SFTP and FTPS as protocols supporting server-side copy and/or move operations are mentioned nowhere, neither in the existing documentation nor the pending documentation update.

Interestingly my testing experience is contrary to yours

Environment

• Client: Cyberduck 8.5.5 (39213) on macOS 11.7.3 Big Sur
  • Maybe my elder macOS?
• Server: SFTP, on custom port (5-digits, assigned by my webhost), authentication with SSH key
  • Maybe that particular protocol and configuration?

Tests

Dragging a file from one browser window to the other

Maybe the whole thing is a client side GUI/interaction bug? Long before it reaches the network protocol functions? I have this suspicion due to this observation:

• No modifier key held: During dragging mouse pointer shows with the extra "+" (plus) symbol.
  • ❗️ Correct for move operation would be just the normal mouse pointer.
• Holding down ⌥ (or ⌘ alternatively as an experiment) that does NOT change the mouse pointer.
  • ❗️ Also contrary to documentation and usual macOS conventions.
• Whatever modifier key you use (none, ⌥ , ⌘ ) → Transfer goes through client!
  • ❗️ "Transfer" window shows so. Does not happen server side.

⌘-X and ⌘-V not working at all

• Focus in window 1.
• File selected in window 1.
• ⌘-X
  • ✅ Menu bar > "Edit" flashes shortly.
• Focus in window 2
• Either nothing selected or any file selected (makes no difference).
• ⌘-V.
  • ❌ Nothing happens. 👉 I hear the standard macOS error beep sound.
• Further tests/observations.
• Focus still in window 2.
• I go to: Menu > Edit: Interestingly Paste ⌘ V is shown as inactive (greyed out)
  • Again: Cyberduck seems to "forbid" that for some reason.
• Focus back to window 1.
• Menu > Edit: Paste "filename-that-i-had-cut.png" ⌘ V is shown normally.

⌘-C and ⌘-V not working at all

• Focus in window 1.
• File selected in window 1.
• ⌘-C
  • ✅ Menu bar > "Edit" flashes shortly.
• Focus in window 2
• Either nothing selected or any file selected (makes no difference).
• ⌘-V.
  • ❌ Nothing happens. 👉 I hear the standard macOS error beep sound.
• I go to: Menu > Edit: Interestingly Paste ⌘ V is shown as inactive (greyed out)
  • So Cyberduck seems to "forbid" that for some reason.
• Focus back to window 1.
• Menu > Edit: Paste "filename-that-i-had-copied.png" ⌘ V is shown normally.

Please also note: When I do all of the above in a single window, then all operations work normal.

Move operation

• ⌘-X, go into other folder, ⌘-V
• Drag'n'drop into folder with no modifier key
• Outcome of both methods → ✅ Immediate server side move operation.

Copy operation

• ⌘-C, go into other folder, ⌘-V
• Drag'n'drop into folder with ⌥ key held
• Outcome of both methods → ✅ Transfer clearly goes through the client.
  • Note: "Transfer" window shows nothing.
  • But status bar on window bottom shows spinner plus Copying "filename-that-I-dropped.png"
  • And my Network monitoring shows the traffic corresponding to file size..
  • 💡 Ofc I would prefer this to happen server side too. But if the protocol ain't allowing it, so be it.

Thanks for your concise report, I can now reproduce. The workaround is to

• Open a new browser window (⌘-N)
• Connect to the same bookmark

Regression from #2596.

Haha! Finally found something

• Your proposed workaround (by itself alone) did not help.
• But I found one way!

Currently only way to perform file move/copy operations between two windows of the same server.

• Close all browser windows.
  • 👉 So that automatic window restoration on startup does not interfere! Makes the difference!
• Quit Cyberduck.
• Start Cyberduck.
  • No windows are open now.
  • Note: In my recent scenario tests my window 1 was mostly/always a restored window (👍 so convenient to continue in the same working directory as last time, great feature 👍 ).
• Then open new window 1, then open new window 2.
• ✅ All operations work as expected for the protocol type.

Tried another variation of this, which sadly does not work

• Close all windows.
• Restart Cyberduck.
• Open window 1.
• Browse somewhere.
• Right click directory → New Browser → Opens window 2.
• Now between window 1 and 2 we have the same problems as initially described.

TL;DR: So currently only works like this:

1. Close all windows. Restart Cyberduck.
2. New Window 1, browse to source path.
3. New Window 2, browse to destination path.
4. Perform your file copy/move operations.
5. Note: Closing all windows and then proceeding to °2 (two fresh windows) worked in some instances! In doubt you must proceed to °1 (a "clean slate" restart).

1. Great that your pull requests get proper code review and expert discussion.

2. But please don't forget about the second part: For optimal co-operation with your bug-reporters, software-testers, etc, please add a proper close comment, so that your submitter knows what was fixed (all, parts, still some limitations, etc) and whether any further software testing is expected or would be appreciated.

My concrete question: After this fix copy/move operations on the same server with the same protocol between multiple browser window instances work, regardless how the windows get into existence?

Please re-open!

• Tested Cyberduck 8.5.6 (39394)
• macOS 11.7.4 Big Sur
• Server: SFTP, on custom port (5-digits, assigned by my webhost), authentication with SSH key

Test scenarios and their outcome

• One window open. Right-click folder → Open new browser.
  • ✅ Drag'n'drop: Moves file.
    • But its UX is dangerously impacted by File move operation with drag'n'drop to destination window shows file still at source window although not there anymore on server in reality #14186
  • ✅ Drag'n'drop + ALT key down: Copies file through the client as SFTP allows no copy on server operation.
  • ❌ Copy/cut/paste via shortcuts still both fail:
    • ⌘X or ⌘C in one window both work. But then ⌘V in the other window fails.
    • Menu > Edit > Paste menu entry is shown as grayed out!