Bug relating to certain large Torrent files - specifically with 128/256mb chunks

[Ithillion]

qBittorrent & operating system versions

qBittorrent 5.1.2-5.1.3
Qt 6.9.3
LibTorrent 1.2.20.0
etc (its's a plain qBittorrent 5.1.2/3 Win 11 (25H2), x64 install)

What is the problem?

Certain large-chunk (sorry I do not know the correct term) torrent files do not open any more in the application. The best example I can give would be certain annas-archive torrents, however it appears to be the case more generally. This problem arose after 5.1.1/5.1.0

Previously there were no issues with these files. rolling back the install to 5.1.0 files still open correctly.

Steps to reproduce

To reproduce, you could attempt to use this torrent from Annas-Archive
https://annas-archive.org/dyn/small_file/torrents/managed_by_aa/annas_archive_data__aacid/annas_archive_data__aacid__ia2_acsmpdf_files__20231009T030032Z--20231009T030033Z.torrent

while there are other torrents which are available which illustrate this, this is the simplest example. The file simply no longer opens. Interestingly, those which had previously been open in the application continue to function.

Additional context

No response

Log(s) & preferences file(s)

14/11/2025 11:35 AM - Failed to add torrent. Source: "C:\Downloads\annas_archive_data__aacid__ia2_acsmpdf_files__20231009T030032Z--20231009T030033Z.torrent". Reason: "invalid piece size [libtorrent:48]"

[qBittUser]

There's 2 different installers for each version.

Maybe your v5.1.0 is using libtorrent 2.0?

[xavier2k6]

@Ithillion for torrent with 128/256MiB Piece size - you will need to use a libtorrent 2.x base build

https://sourceforge.net/projects/qbittorrent/files/qbittorrent-win32/qbittorrent-5.1.3/qbittorrent_5.1.3_qt6_lt20_x64_setup.exe/download

[stalkerok]

@Ithillion for torrent with 128/256MiB Piece size - you will need to use a libtorrent 2.x base build

https://sourceforge.net/projects/qbittorrent/files/qbittorrent-win32/qbittorrent-5.1.3/qbittorrent_5.1.3_qt6_lt20_x64_setup.exe/download

Only 256MiB

[xavier2k6]

@Ithillion for torrent with 128/256MiB Piece size - you will need to use a libtorrent 2.x base build
https://sourceforge.net/projects/qbittorrent/files/qbittorrent-win32/qbittorrent-5.1.3/qbittorrent_5.1.3_qt6_lt20_x64_setup.exe/download

Only 256MiB

guilty of copy/pasta! 😆

[Ithillion]

Oh... facepalm I feel like a goose. I had done exactly that, and installed the version with libtorrent 1.2.2. I genuinely have no idea how that happened unless it was my software update service selecting the wrong package I had always selected the LT2.0 since the option had become available.

Thanks guys!!