Korean caption fonts on Sume: why weight-shift needs Pretendard

On Sume, the weight-shift and korean-ad caption styles animate the wght axis, and only Pretendard has that axis. If you set font to any other Hangul face, the style keeps its color and scale emphasis but loses the weight travel. If you omit font, korean-ad and weight-shift use Pretendard. The details are on Video captions, read 2026-10-06.

Which style uses which face?

The docs give a default face per style, and font changes only the face.

What breaks if I pick the wrong font?

Two guards protect you. Korean text on slam, punch or tiktok-green returns 400 caption_hangul_text_latin_style, because those Latin display faces have no Hangul glyphs. A Hangul font on a Latin style returns 400 caption_font_requires_hangul_style. In both cases you pay nothing, because the error comes at request time and not after a render.

• Send language: "ko" as a speech-to-text hint; it never selects a style or font.
• Send style: "korean-ad" explicitly if you want the ad karaoke look; with no style, Korean text resolves to black-outline.
• editorial-emphasis always uses Black Han Sans for its emphasis line.

Does the font list change per request?

font is optional and the API rejects names outside its list instead of falling back, so a caption never silently uses a face you did not select.