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+# YouTube Upload Logic
+
+This page describes how videos are uploaded to YouTube and how metadata, playlists, thumbnails, and recording dates are handled.
+
+## Upload Function
+
+Uploads are handled by:
+```python
+upload_video(file_path, is_vertical, stream_date, description=None, private=False)
+```
+
+## Workflow
+
+1. Authenticate via OAuth
+2. Generate title and description:
+   - Uses stream date and `notes.txt` (if present)
+3. Upload video with privacy setting
+4. **If widescreen**, generate and upload thumbnail
+5. Add video to playlist:
+   - Shorts → `YT_PLAYLIST_ID_SHORTS`
+   - Clips → `YT_PLAYLIST_ID_CLIPS`
+6. Set recording date using parsed `YYYY.MM.DD`
+
+## Thumbnail Handling
+
+- Thumbnail upload occurs **after** the video is successfully uploaded
+- Thumbnail is skipped for vertical videos (Shorts)
+- Notes file is used to guide prompt generation (for future AI images)
+
+---