A specific line disappearing entirely when font is set up to Cascadia Mono or Kawkab Mono

[asibahi]

Issue Description

In the process of writing examples for zabadi I made a script that divides lines per characters. The paragraph renders as expected (with RTL being reversed) with the default font and other fonts I tried. However, when I set the font to Cascadia Mono one of the lines just .. did not render. Note that Cascadia Mono has no Arabic support, same as JetBrains Mono, and is using the same fallback system font.

Note

I am not talking about RTL being reversed. I am talking about the line not being rendered.

Expected Behavior

The expected behaviour is that text should actually be drawn. Other lines are being rendered, this line is not.

This is how it looks with the default font. (RTL being reversed is not the point I am talking about here.)

Actual Behavior

This is how it looks with Cascadia Mono (and Cascadia Code)

This is how it looks like with Kawkab Mono, which I downloaded specifically to see how it looks and it does include English and Arabic glyphs.

For reference, tho I don't think it is relevant due to the issue showing in another font, this is the Cascadia Mono entry on ghostty +list-fonts

Cascadia Mono
  Cascadia Mono Italic Bold Italic
  Cascadia Mono Italic ExtraLight Italic
  Cascadia Mono Italic Italic
  Cascadia Mono Italic Light Italic
  Cascadia Mono Italic SemiBold Italic
  Cascadia Mono Italic SemiLight Italic
  Cascadia Mono Regular Bold
  Cascadia Mono Regular ExtraLight
  Cascadia Mono Regular Light
  Cascadia Mono Regular Regular
  Cascadia Mono Regular SemiBold
  Cascadia Mono Regular SemiLight

Reproduction Steps

This is the text in question

All human beings are born
free and equal أحرارا ومتس
اوين in dignity and rights
 في الكرامة والحقوق. They
are endowed with reason an
d conscience العقل والضمير
 and should act towards on
e another in a spirit of b
rotherhood.

The script that generated these line breaks can be found on the zabadi repo. To run it clone the repo and run zig build example.

This is the full output with the default configuration

This is the full output with font-family="Cascadia Mono" (note that in the second section, the same line is also not being rendered.)

Ghostty Logs

Filtering the log data using "subsystem == "com.mitchellh.ghostty""
Timestamp                       Thread     Type        Activity             PID    TTL  
2025-08-19 11:38:59.765184+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] ghostty version=1.1.3
2025-08-19 11:38:59.765670+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] ghostty build optimize=ReleaseFast
2025-08-19 11:38:59.765679+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] runtime=apprt.Runtime.none
2025-08-19 11:38:59.765684+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] font_backend=font.main.Backend.coretext
2025-08-19 11:38:59.765688+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] renderer=renderer.Metal
2025-08-19 11:38:59.765691+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] libxev backend=main.Backend.kqueue
2025-08-19 11:38:59.765809+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:os] setlocale from env result=en_US.UTF-8
2025-08-19 11:38:59.767715+0300 0x163f78   Info        0x0                  9855   0    ghostty: [com.mitchellh.ghostty:default] executing CLI action=cli.action.Action.version
2025-08-19 11:38:59.772303+0300 0x16392c   Error       0x0                  9794   0    ghostty: [com.mitchellh.ghostty:stream] unimplemented OSC callback: terminal.osc.Command{ .end_of_command = terminal.osc.Command.Command__struct_20675{ .exit_code = 0 } }
2025-08-19 11:38:59.772353+0300 0x16392c   Error       0x0                  9794   0    ghostty: [com.mitchellh.ghostty:stream] unimplemented OSC command: end_of_command

Ghostty Version

Ghostty 1.1.3

Version
  - version: 1.1.3
  - channel: stable
Build Config
  - Zig version: 0.13.0
  - build mode : builtin.OptimizeMode.ReleaseFast
  - app runtime: apprt.Runtime.none
  - font engine: font.main.Backend.coretext
  - renderer   : renderer.Metal
  - libxev     : main.Backend.kqueue

OS Version Information

MacBook Air M2 - macOS Tahoe beta

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

font-family="Cascadia Mono"

# also reproduced with 
font-family="Cascadia Code"

# and 
font-family="Kawkab Mono"

Additional Relevant Configuration

The Cascadia fonts and Kawkab Mono were installed from their respective repos.

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.