fix(producer): force text-rendering:geometricPrecision so headless-shell matches Chrome#985
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miguel-heygen
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May 20, 2026
…o-preview-assets The text-rendering:geometricPrecision rule injected by the previous commit shifts glyph advances by ~1% on chrome-headless-shell (was optimizeSpeed under text-rendering:auto). Two fixtures with strict gates tripped: - distributed/png-sequence: maxFrameFailures=0 byte-identity gate, all 60 frames now differ. The fixture's own meta.json already documents this as the expected response to renderer-pixel changes. - heygen-promo-preview-assets: minPsnr=30, maxFrameFailures=0; one frame dropped to 27.67 dB after the layout shift. Full local regression run (47 fixtures): 45 passed, only these 2 needed regeneration — the text-rendering change passes through the rest without PSNR impact. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
jrusso1020
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What
Inject
html, body, * { text-rendering: geometricPrecision; }into every compiled composition sochrome-headless-shell(the binary BeginFrame requires) lays out text identically to full Chrome.Why
The two Chrome binaries silently disagree on the default value of
text-rendering: auto:text-rendering: autoresolves tochrome-headless-shelloptimizeSpeed(integer-rounded advances)geometricPrecision(subpixel advances)That ~1% advance-width gap cascades:
element.offsetWidthto compute a transform scale (e.g.cardScale = targetWidth / naturalCardWidth) get a different scale per binary, which then shifts every pixel of the card.It's an intrinsic per-binary CSS default — not a Chromium-version drift — so no version pin closes it. Forcing
geometricPrecisionputs both binaries on the same subpixel glyph path that full Chrome was already using.Ported from the experiment-framework GSAP renderer fix in heygen-com/experiment-framework#37369. There it lifted worst-case PSNR from 12.56 → 24.66 dB and cut SSIM standard deviation ~3.2× across 200 production templates.
Same browser dichotomy applies in hyperframes:
packages/engine/src/services/browserManager.ts:43— BeginFrame mode launcheschrome-headless-shell.hyperframes snapshotand friends also drivechrome-headless-shellviabundleToSingleHtml, so the bundler path needs the same rule for studio/snapshot ↔ producer parity.How
Two small head-style injections, mirroring the existing
injectDeterministicFontFacespattern.packages/producer/src/services/htmlCompiler.tsinjectTextRenderingRule(html)— inserts<style data-hyperframes-text-rendering="true">html,body,*{text-rendering:geometricPrecision}</style>at the start of<head>. Idempotent.compileForRenderbetweencoalesceHeadStylesAndBodyScripts(...)andinjectDeterministicFontFaces(...), so the rule lands in the compiled HTML (and the content-addressed planDir hash) before user CSS is merged.ensureFullDocument's fallback<style>block also getstext-rendering:geometricPrecisionappended to the universal selector, so fragment compositions don't bypass the fix.packages/core/src/compiler/htmlBundler.tsbundleToSingleHtmlaftercoalesceHeadStylesAndBodyScripts. Studio runs in full Chrome so this is a visual no-op there, but it keeps the bundled HTML byte-aligned with the producer compile output, which is whatsnapshot/validate/layout(all of which feed bundled HTML into headless renders) need.Specificity is preserved:
*is (0,0,0), so any composition's class/id/element-targetedtext-renderingrule still overrides.Out of scope: residual non-text-layout divergence (SVG filter/shadow/gradient rasterization between the binaries) — same caveat called out in heygen-com/experiment-framework#37369.
Test plan
packages/producer/src/services/htmlCompiler.test.ts(full-doc + fragment paths) andpackages/core/src/compiler/htmlBundler.test.ts.bun test packages/producer/src/services/htmlCompiler.test.ts— 38 pass.bunx vitest run packages/core/src/compiler/htmlBundler.test.ts(frompackages/core) — 31 pass.bunx oxlint+bunx oxfmt --checkon all 4 changed files — clean.bun run --cwd packages/producer build+bun run --cwd packages/core build— green.bun run --cwd packages/producer docker:test:update <test-name>perDockerfile.test(not from host).hyperframes renderto confirm PSNR vs. a full-Chrome render.🤖 Generated with Claude Code