External Subtitles Can Lose Additional Language Information when Renamed

Is there an existing issue for this?

• I have searched the existing open and closed issues

Current Behavior

When Sonarr renames external subtitle files it will rename the language code nb to no which is wrong. I have no idea why Sonarr does this as it makes no sense at all.

For reference:

• no Norwegian
• nb Norwegian Bokmål
• nn Norwegian Nynorsk

"Norwegian" (no) is an umbrella term for the Norwegian language and should be avoided whenever possible since it is ambiguous.

I have not checked how Sonarr treats internal subs, only external.

Expected Behavior

Sonarr should never have to rename no, nb, or nn, but rather keep them as they are parsed.

nb = nb nn = nn no = no (should be avoided when possible)

The only situation where it would make sense to use no are situations where one does not know whether it is Bokmål or Nynorsk (often the case with subtitles).

Steps To Reproduce

1. Set Sonarr to "Import Extra Files"
2. Add a show with an external subtitle file that ends in nb.srt
3. Click rename files.
4. Observe nb becoming no.

Environment

- OS: Unraid 7
- Sonarr: 4.0.17.2952
- Docker Install: binhex-sonarr
- Using Reverse Proxy: No
- Browser: Firefox
- Database: Sqlite 3.51.2

What branch are you running?

Main

Trace Logs?

2026-03-31 15:04:39.6|Trace|SubtitleService|Renaming extra file: [26776] Season 05/Some Show (2002) - S01E01.nb.vtt (Norwegian.(2002) - S01E01.vtt)
2026-03-31 15:04:39.6|Trace|SubtitleService|Renaming extra file: [26776] Season 05/Some Show (2002) - S01E01.nb.vtt (Norwegian.(2002) - S01E01.vtt) to /TV_SERIES/Some Show (2002)/Season 05/Some Show (2002) - S01E01 - Pilot [HDTV-1080p][EAC3 5.1][HDR10][AV1].(2002) - S01E01.no.vtt
2026-03-31 15:04:39.6|Trace|DiskProvider|Moved '/TV_SERIES/Some Show (2002)/Season 05/Some Show (2002) - S01E01.nb.vtt' -> '/TV_SERIES/Some Show (2002)/Season 05/Some Show (2002) - S01E01 - Pilot [HDTV-1080p][EAC3 5.1][HDR10][AV1].(2002) - S01E01.no.vtt' using Syscall.rename

Anything else?

No response