CEP panel intermittently renders as blank/grey — content composited but never presented (Illustrator 2026 / CEP 12.1 / Apple Silicon)
Environment
- Adobe Illustrator 2026 (30.6.0), CEP runtime 12.1 / Chromium 99, AdobeCEP/12.1.0
- macOS on Apple Silicon; display at fractional HiDPI (CEP logs Zoom Html 1.250000)
- Custom CEP panel extension (Angular content)
Symptom
- Intermittently, on panel open, the panel shows as an empty grey pane and never populates for the remainder of the Illustrator session.
The extension page fully loads and renders: DOM is present, correctly sized, document.visibilityState === 'visible', OnLoadEnd fires. The host bridge works — adobe_cep.evalScript('1+1') returns 2.
The rendered pixels never reach the screen: setting document.body.style.background = 'red' produces no visible change in the panel, and DevTools "Capture screenshot" returns a blank image.
With CEF logging enabled (--enable-logging --v=1 --enable-gpu-service-logging): the GL context initializes successfully and raster commands run continuously, with zero GL/GPU errors. No renderer/GPU process crash is recorded.
The failure is per-panel-instance: in the same Illustrator session, other CEP panels (a sibling extension and Adobe's own OnBoarding panel) render normally.
Not recoverable by: native content resize, forced reflow/recomposite from JS, or closing and reopening the panel. Only a full Illustrator restart clears it (the panel's CEPHtmlEngine/GPU process persists across panel close and stays wedged).
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The extension renders correctly but its composited output is never presented to the panel's surface — a compositor/present-path failure inside the CEP CEF runtime, not in the extension.
Peter Coppens
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