diff --git a/frontend/src/react/components/OpBlockNoteEditor.tsx b/frontend/src/react/components/OpBlockNoteEditor.tsx
index 55e1f385173b..12efd08a77b4 100644
--- a/frontend/src/react/components/OpBlockNoteEditor.tsx
+++ b/frontend/src/react/components/OpBlockNoteEditor.tsx
@@ -29,6 +29,7 @@ import { BlockNoteEditorOptions, BlockNoteSchema, User } from '@blocknote/core';
 import { ExternalLinkA11yExtension } from '../extensions/external-link-a11y';
 import { ExternalLinkCaptureExtension } from '../extensions/external-link-capture';
 import { CollaborationCursorLabelFitExtension } from '../extensions/collaboration-cursor-label-fit';
+import { FailedUploadCleanupExtension } from '../extensions/failed-upload-cleanup';
 import { HeadingLinkExtension } from '../extensions/heading-link';
 import { filterSuggestionItems } from '@blocknote/core/extensions';
 import { withCollaboration } from '@blocknote/core/yjs';
@@ -100,6 +101,7 @@ export function OpBlockNoteEditor({
       extensions: [
         ExternalLinkA11yExtension,
         HeadingLinkExtension,
+        ...(attachmentsEnabled ? [FailedUploadCleanupExtension] : []),
         ...(captureExternalLinks ? [ExternalLinkCaptureExtension] : []),
         ...(hocuspocusProvider ? [CollaborationCursorLabelFitExtension] : []),
       ],
diff --git a/frontend/src/react/extensions/failed-upload-cleanup.spec.ts b/frontend/src/react/extensions/failed-upload-cleanup.spec.ts
new file mode 100644
index 000000000000..dee1bd617eaf
--- /dev/null
+++ b/frontend/src/react/extensions/failed-upload-cleanup.spec.ts
@@ -0,0 +1,136 @@
+//-- copyright
+// OpenProject is an open source project management software.
+// Copyright (C) the OpenProject GmbH
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License version 3.
+//
+// OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+// Copyright (C) 2006-2013 Jean-Philippe Lang
+// Copyright (C) 2010-2013 the ChiliProject Team
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+//
+// See COPYRIGHT and LICENSE files for more details.
+//++
+
+import { BlockNoteEditor, PartialBlock } from '@blocknote/core';
+import { FailedUploadCleanupExtension } from './failed-upload-cleanup';
+
+const UPLOADED_URL = 'https://openproject.example/attachments/1/content';
+
+const cleanups:(() => void)[] = [];
+
+function mountEditor(uploadFile:(file:File) => Promise<string>, initialContent?:PartialBlock[]) {
+  const container = document.createElement('div');
+  document.body.appendChild(container);
+  const editor = BlockNoteEditor.create({ initialContent, uploadFile, extensions: [FailedUploadCleanupExtension] });
+  editor.mount(container);
+  cleanups.push(() => {
+    editor.unmount();
+    container.remove();
+  });
+
+  return { editor, container };
+}
+
+function filesTransfer():DataTransfer {
+  const transfer = new DataTransfer();
+  transfer.items.add(new File(['content'], 'notes.odt', { type: 'application/vnd.oasis.opendocument.text' }));
+  return transfer;
+}
+
+function dropFile(container:HTMLElement):void {
+  const target = container.querySelector('.bn-block-content')!;
+  const { left, top } = target.getBoundingClientRect();
+  target.dispatchEvent(new DragEvent('drop', {
+    dataTransfer: filesTransfer(), clientX: left + 5, clientY: top + 2, bubbles: true, cancelable: true,
+  }));
+}
+
+function pasteFile(editor:BlockNoteEditor):void {
+  editor.prosemirrorView.dom.dispatchEvent(new ClipboardEvent('paste', {
+    clipboardData: filesTransfer(), bubbles: true, cancelable: true,
+  }));
+}
+
+const settled = () => new Promise((resolve) => { setTimeout(resolve, 50); });
+const blockTypes = (editor:BlockNoteEditor) => editor.document.map((block) => block.type);
+
+describe('FailedUploadCleanupExtension', () => {
+  afterEach(() => {
+    cleanups.splice(0).forEach((cleanup) => cleanup());
+  });
+
+  it('removes the placeholder of a dropped file whose upload failed', async () => {
+    const { editor, container } = mountEditor(() => Promise.resolve(''), [{ type: 'paragraph', content: 'Text' }]);
+
+    dropFile(container);
+    await settled();
+
+    expect(blockTypes(editor)).toEqual(['paragraph']);
+    expect(container.querySelector('.bn-file-loading-preview')).toBeNull();
+  });
+
+  it('keeps the block of a dropped file that was uploaded', async () => {
+    const { editor, container } = mountEditor(() => Promise.resolve(UPLOADED_URL), [{ type: 'paragraph', content: 'Text' }]);
+
+    dropFile(container);
+    await settled();
+
+    expect(editor.document.find((block) => block.type === 'file')?.props).toMatchObject({ url: UPLOADED_URL });
+  });
+
+  it('removes the placeholder of a pasted file whose upload failed', async () => {
+    const { editor, container } = mountEditor(() => Promise.resolve(''), [{ type: 'paragraph' }]);
+    editor.focus();
+
+    pasteFile(editor);
+    await settled();
+
+    expect(blockTypes(editor)).not.toContain('file');
+    expect(container.querySelector('.bn-file-loading-preview')).toBeNull();
+  });
+
+  it('keeps the block of a file panel upload that failed, which offers to add a file again', async () => {
+    const { editor, container } = mountEditor(() => Promise.resolve(''), [{ id: 'image', type: 'image' }, { type: 'paragraph' }]);
+    const file = new File(['content'], 'photo.png', { type: 'image/png' });
+
+    const url = await editor.uploadFile!(file, 'image');
+    editor.updateBlock('image', { props: { name: file.name, url: url as string } });
+    await settled();
+
+    expect(blockTypes(editor)).toEqual(['image', 'paragraph']);
+    expect(container.querySelector('.bn-add-file-button')).not.toBeNull();
+  });
+
+  it('leaves an empty file block nobody uploaded to', async () => {
+    const { editor } = mountEditor(() => Promise.resolve(''), [{ type: 'file' }, { type: 'paragraph' }]);
+
+    await settled();
+
+    expect(blockTypes(editor)).toEqual(['file', 'paragraph']);
+  });
+
+  it('does nothing once the editor is gone', async () => {
+    let finishUpload:((url:string) => void)|undefined;
+    const { container } = mountEditor(() => new Promise((resolve) => { finishUpload = resolve; }), [{ type: 'paragraph' }]);
+    dropFile(container);
+
+    cleanups.splice(0).forEach((cleanup) => cleanup());
+    finishUpload!('');
+
+    await expect(settled()).resolves.toBeUndefined();
+  });
+});
diff --git a/frontend/src/react/extensions/failed-upload-cleanup.ts b/frontend/src/react/extensions/failed-upload-cleanup.ts
new file mode 100644
index 000000000000..42aa970200ae
--- /dev/null
+++ b/frontend/src/react/extensions/failed-upload-cleanup.ts
@@ -0,0 +1,44 @@
+//-- copyright
+// OpenProject is an open source project management software.
+// Copyright (C) the OpenProject GmbH
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License version 3.
+//
+// OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+// Copyright (C) 2006-2013 Jean-Philippe Lang
+// Copyright (C) 2010-2013 the ChiliProject Team
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+//
+// See COPYRIGHT and LICENSE files for more details.
+//++
+
+import { createExtension } from '@blocknote/core';
+
+// A file block turns into "Loading..." when its upload starts and only renders again once
+// its props change. After a failed drop or paste nothing changes, so the placeholder would
+// stay stuck (https://github.com/TypeCellOS/BlockNote/issues/3246). BlockNote updates the
+// block after the upload ends, hence the timeout.
+export const FailedUploadCleanupExtension = createExtension(({ editor }) => ({
+  key: 'failedUploadCleanup',
+  mount: ({ signal }) => editor.onUploadEnd((blockId) => {
+    if (!blockId) return;
+
+    setTimeout(() => {
+      const stuck = !signal.aborted && editor.domElement?.querySelector(`[data-id="${blockId}"] .bn-file-loading-preview`);
+      if (stuck) editor.removeBlocks([blockId]);
+    });
+  }),
+}))();
diff --git a/modules/documents/spec/features/attachment_upload_spec.rb b/modules/documents/spec/features/attachment_upload_spec.rb
index bd8f294883d0..07b52ecdc906 100644
--- a/modules/documents/spec/features/attachment_upload_spec.rb
+++ b/modules/documents/spec/features/attachment_upload_spec.rb
@@ -169,6 +169,16 @@
           expect(editor.element).to have_no_css("img[alt='image.png']")
         end.not_to change { document.attachments.count }
       end
+
+      it "leaves no placeholder behind for a dropped file" do
+        expect do
+          editor.drop_file(image_fixture.path)
+          expect(page).to have_text I18n.t("activerecord.errors.models.attachment.attributes.content_type.not_allowlisted",
+                                           value: "image/png")
+          expect(editor.element).to have_no_css("[data-content-type='image']")
+          expect(editor.element).to have_no_text("Loading...")
+        end.not_to change { document.attachments.count }
+      end
     end
   end
 
diff --git a/spec/support/form_fields/primerized/block_note_editor_input.rb b/spec/support/form_fields/primerized/block_note_editor_input.rb
index 15572d2e79bf..a5ab47e182bc 100644
--- a/spec/support/form_fields/primerized/block_note_editor_input.rb
+++ b/spec/support/form_fields/primerized/block_note_editor_input.rb
@@ -163,6 +163,31 @@ def paste_links(*links)
         JS
       end
 
+      # Capybara's own `drop` sends no coordinates, and BlockNote places a dropped file
+      # by them, so it would ignore the drop.
+      def drop_file(path)
+        input_id = "block-note-drop-file"
+        page.execute_script(<<~JS, input_id)
+          const input = document.createElement('input');
+          input.type = 'file';
+          input.id = arguments[0];
+          document.body.appendChild(input);
+        JS
+        page.find_by_id(input_id, visible: :all).set(path)
+
+        page.execute_script(<<~JS, element.native, input_id)
+          const input = document.getElementById(arguments[1]);
+          const block = arguments[0].querySelector('.bn-block-content');
+          const { left, top, height } = block.getBoundingClientRect();
+          const dataTransfer = new DataTransfer();
+          dataTransfer.items.add(input.files[0]);
+          input.remove();
+          block.dispatchEvent(new DragEvent('drop', {
+            dataTransfer, clientX: left + 1, clientY: top + height / 2, bubbles: true, cancelable: true
+          }));
+        JS
+      end
+
       def element
         shadow_root.find("div[role='textbox']")
       end