DeleteImage fails if it is sent right after the image is generated

[Lawrr]

Expected Behavior

1. I send an API request to GenerateText2Image and get returned the path to the image
2. I then send an API request to DeleteImage and it deletes the image successfully

Actual Behavior

1. I send an API request to GenerateText2Image and get returned the path to the image
2. I then send an API request to DeleteImage and it returns an error

Steps to Reproduce

1. Send an API request to GenerateText2Image
2. Send an API request to DeleteImage (will be dependent on timing, see logs below)

Debug Logs

Logs (with some additional log lines added):

Error 1 - If GetOrCreatePreviewFor wins

22:12:01.641 [Debug] [ComfyUI-0/STDERR] Prompt executed in 25.48 seconds
22:12:02.162 [Info] T2API.saveImage start
22:12:02.190 [Info] session.SaveImage start
22:12:02.197 [Info] session.SaveImage done
22:12:02.200 [Info] async Utilities.RunCheckedTask start
22:12:02.202 [Info] T2API.saveImage done
22:12:02.207 [Info] Generated an image in 7.53 sec (prep) and 26.00 sec (gen)
22:12:02.221 [Info] Returning images to client
22:12:02.274 [Info] File.WriteAllBytes start
22:12:02.277 [Info] File.WriteAllBytes done
22:12:02.280 [Info] API.HandleAsyncRequest - start handling API request
22:12:02.281 [Info] OutputMetadataTracker.GetOrCreatePreviewFor start
22:12:02.316 [Warning] Error reading image preview for file 'C:/Folders/StableDiffusion/SwarmUI/Output/local/raw/foo.jpg': System.IO.IOException: The process cannot access the file 'C:\Folders\StableDiffusion\SwarmUI\Output\local\raw\2025-12-23\foo.jpg' because it is being used by another process.
   at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.File.ReadAllBytes(String path)
   at SwarmUI.Utils.OutputMetadataTracker.GetOrCreatePreviewFor(String file) in C:\Folders\StableDiffusion\SwarmUI\src\Utils\OutputMetadataTracker.cs:line 276
22:12:02.320 [Info] OutputMetadataTracker.GetOrCreatePreviewFor done
22:12:02.322 [Debug] Saved an output file as 'C:\Folders\StableDiffusion\SwarmUI\Output\local\raw\2025-12-23\foo.jpg'

Error 2 - If DeleteImage wins

21:24:47.647 [Debug] [ComfyUI-0/STDERR] Prompt executed in 23.18 seconds
21:24:48.108 [Info] T2API.saveImage start
21:24:48.111 [Info] session.SaveImage start
21:24:48.117 [Info] session.SaveImage done
21:24:48.119 [Info] async Utilities.RunCheckedTask start
21:24:48.120 [Info] T2API.saveImage done
21:24:48.124 [Info] Generated an image in 9.53 sec (prep) and 23.64 sec (gen)
21:24:48.133 [Info] Returning images to client
21:24:48.185 [Info] File.WriteAllBytes start
21:24:48.189 [Info] File.WriteAllBytes done
21:24:48.191 [Info] API.HandleAsyncRequest - start handling API request
21:24:48.200 [Warning] Error reading image preview for file 'C:/Folders/StableDiffusion/SwarmUI/Output/local/raw/foo.jpg' because it is being used by another process.
   at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.File.ReadAllBytes(String path)
   at SwarmUI.Utils.OutputMetadataTracker.GetOrCreatePreviewFor(String file) in C:\Folders\StableDiffusion\SwarmUI\src\Utils\OutputMetadataTracker.cs:line 276
21:24:48.210 [Debug] Saved an output file as 'C:\Folders\StableDiffusion\SwarmUI\Output\local\raw\2025-12-23\foo.jpg'

Other

Seems to be a race condition between the DeleteImage API request and this line:

SwarmUI/src/Accounts/Session.cs

Line 262 in 424453d

OutputMetadataTracker.GetOrCreatePreviewFor(fullPath.Replace('\\', '/'));

but in theory it could also happen if the image hasn't been saved yet by

SwarmUI/src/Accounts/Session.cs

Line 250 in 424453d

File.WriteAllBytes(fullPath, actualFile.RawData);

Note: Only started running into this after I updated to master. Going back to the 0.9.7-Beta release doesn't seem to have this issue. It seems like for whatever reason, previously the DeleteImage API request began being handled after the image was fully finished saving in that release. i.e. logs looked like this instead:

21:11:08.886 [Debug] [ComfyUI-0/STDERR] Prompt executed in 23.34 seconds
21:11:09.321 [Info] T2API.saveImage start
21:11:09.323 [Info] session.SaveImage start
21:11:09.330 [Info] session.SaveImage done
21:11:09.332 [Info] async Utilities.RunCheckedTask start
21:11:09.333 [Info] T2API.saveImage done
21:11:09.337 [Info] Generated an image in 9.50 sec (prep) and 23.78 sec (gen)
21:11:09.346 [Info] Returning images to client
21:11:09.398 [Info] File.WriteAllBytes start
21:11:09.401 [Info] File.WriteAllBytes done
21:11:09.402 [Debug] Saved an output file as 'C:\Folders\StableDiffusion\SwarmUI\Output\local\raw\2025-12-23\foo.jpg'
21:11:09.403 [Info] API.HandleAsyncRequest - start handling API request

[mcmonkey4eva]

Just send "donotsave": true in your request?

[Lawrr]

I want to include the image metadata without having to change the user-level settings for ReformatTransientImages, which isn't supported

[mcmonkey4eva]

You can and should just enable that setting