Per the HTML spec, each accept token must be a MIME type or start with "." (e.g. ".tgs"). The glob form ".tgs" is invalid, so Chromium discards it and builds the Windows file dialog filter from image/ and video/webm only.
Result: .tgs animated stickers are not listed in the file picker, even though the bot accepts them. The user has to manually switch the dropdown to "All Files (.)".
Steps to reproduce:
Open @Stickers on Telegram Desktop (Windows).
Open a pack, choose edit / add a sticker.
Click the button that opens the file picker.
Check the file type dropdown and the listed files.
Expected: .tgs files are listed.
Actual: only image and .webm files are listed.
Verified in DevTools (enabled via Settings > Advanced > Experimental settings > "Enable webview inspecting") by hooking HTMLInputElement.prototype.click, which logged:
[FILE PICKER] accept = "image/,video/webm,.tgs"
Removing the attribute at click time makes the dialog open with "All Files" selected and .tgs files visible, confirming the attribute is the sole cause.
Fix: change ".tgs" to ".tgs" -> accept="image/,video/webm,.tgs"
This is a Mini App (web page) issue, not a client one. The desktop client only hosts the page in WebView2 and has no API to override the dialog filter (MicrosoftEdge/WebView2Feedback#744, closed as "not planned"). Every Chromium-based Telegram client is affected.
Steps to reproduce
Open @Stickers on Telegram Desktop (Windows).
Open a pack, choose edit / add a sticker.
Click the button that opens the file picker.
Check the file type dropdown and the listed files.
Device info
Windows 11 Pro 25H2
Telegram Desktop 7.1.2
WebView2 Runtime: 151.0.4129.107