Stop inlining the Newsreader faces into the render-blocking stylesheet

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/static/app.css was 305 KB because APP_CSS base64-embedded both woff2
faces into it at runtime, and the browser cannot paint until it has the
whole sheet. Lighthouse mobile put FCP and LCP at 2.4 s for it.

The inlining was justified by a Firefox font-flash theory that the later
FOUC investigation (239125a) disproved: the flash came from theme.js
running ahead of the stylesheet, not from fonts arriving late. So point
the faces back at /static/Newsreader*.woff2, versioned with ASSET_VERSION
so the immutable one-year max-age stays safe. Gzipped, the sheet goes
from 304 KB to 12 KB.

That leaves first paint waiting on a font, so switch both faces from
font-display: block to swap and give them metric-matched local fallbacks
(Georgia, Times New Roman, Noto Serif, DejaVu Serif). The overrides are
computed from Newsreader's own metrics at the body optical size against
@capsizecss/metrics widths, so the fallback occupies the same box and the
swap changes glyph shapes and nothing else: every block on the page lands
at the same y-position either way, and CLS stays at 0.001.

Preload the regular face so it starts with the stylesheet rather than
after it parses; italic stays on demand. theme.js keeps its place after
the stylesheet link.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MD4VWGq6mGcd8Bg67qyx9k

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This commit is contained in:

thallada

2026-09-04 19:58:28 +00:00

co-authored by Claude Fable 5.1

parent 239125a8e5

commit 4c8eeda147

4 changed files with 114 additions and 26 deletions

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