WSL: pane graphics render blurry — cell size is 8x16 while the terminal reports 10x21 via CSI 16t

[WakaTaira]

Is this a reproducible bug?

• I confirm this is a reproducible bug, not a feature request, idea, question, contribution proposal, or direction check.
• I reproduced this bug on the version and environment reported below using the exact steps provided.

Current behavior

Graphics panes render visibly blurry under WSL. pane.graphics.info reports {"cell_width_px":8,"cell_height_px":16}, but the outer terminal's actual cell size is 10x21 px (its CSI 16 t reply is ESC[6;21;10t). Under WSL the pty reports xpixel=0 ypixel=0 (TIOCGWINSZ).

Expected behavior

Pane graphics use the terminal's actual cell size (10x21 here) so frames match the pane's real pixel size and render crisply — as the same setup does on a native Linux host.

Reproduction

1. Windows WezTerm → wsl.exe → herdr with experimental.kitty_graphics = true
2. Open a plugin graphics pane (e.g. the herdr-browser plugin) — the image is upscaled and blurry
3. printf '{"id":"p","method":"pane.graphics.info","params":{"pane_id":"<pane>"}}\n' | nc -U ~/.config/herdr/herdr.sock → {"cell_width_px":8,"cell_height_px":16}
4. In the same terminal outside herdr: printf '\e[16t' and read the reply → ESC[6;21;10t; TIOCGWINSZ on the same tty → rows=37 cols=161 xpixel=0 ypixel=0

Impact

Every graphics pane on WSL is produced at roughly 60% of its actual pixel area and upscaled by the terminal, so browser panes and images are noticeably blurry. The identical config on native Linux (ghostty) renders crisply.

Environment

• Herdr version: 0.7.4
• Update channel (stable or preview): stable
• Operating system: NixOS 26.05 on WSL2 (Windows 11 host)
• Terminal: WezTerm 20260331-040028-577474d8 (Windows) via wsl.exe
• Shell, if relevant: zsh
• Relevant config, if any: [experimental] kitty_graphics = true