Regression since 0.7.38: `ctx.drawElementImage is not a function` in capture_streaming (drawElement / html-in-canvas capture path)

[johannesamee]

Summary

Rendering a composition that uses the drawElement / html-in-canvas capture path (screenshot-fallback frames) fails deterministically with ctx.drawElementImage is not a function during the capture_streaming phase. The regression was introduced between 0.7.37 and 0.7.38 and is still present on the current latest (0.7.42 as of 2026-07-08). 0.7.37 renders the same composition cleanly. Compositions that do not exercise this capture path render fine on the broken versions.

Repro

A minimal HF project (hyperframes.json + index.html) with a sub-composition block that triggers the drawElement capture path (in our case: an overlay card block combining an <img> avatar, text, and animated elements, rendered to transparent MOV):

npx hyperframes@0.7.42 render <project-dir> -c blocks/follow-card.html --format mov -o out.mov \
  --variables '{"avatarPath":"assets/avatar.jpg","displayName":"Example","handle":"@example","counterText":"","showVerified":false}'

Same failure with --format webm. Same failure via bare npx hyperframes render ... (resolves latest).

Observed

Render reaches capture_streaming, injects the drawElement canvas, then fails at 25%:

[initSession:drawelement] drawElement canvas injected (3467ms)
[initSession:drawelement] screenshot fallback: 5 clip-boundary frame(s) (3468ms)
[INFO] [Render:trace] {"phase":"capture_streaming","status":"error","message":"ctx.drawElementImage is not a function"}
██████░░░░░░░░░░░░░░░░░░░  25%  Failed: ctx.drawElementImage is not a function

Failure summary reports observedFailedPhase: "capture_streaming", isTimeout: false, 0 browser console errors. Exit code 1, no output file.

Environment: macOS (darwin arm64, Apple M3 Pro), Node v26.4.0, HeadlessChrome/140.0.7339.207, gl=angle/Metal, browserGpuMode auto → hardware.

Expected

The composition renders to a valid MOV/WebM, as it does on 0.7.37.

Bisection

• 0.7.37 — renders clean (last good)
• 0.7.38 — fails (first broken)
• 0.7.39 — fails
• 0.7.41 — fails
• 0.7.42 (current latest) — fails, re-confirmed 2026-07-08

The break is isolated to the drawElement/html-in-canvas capture path: the normal (non-drawElement) render path renders the same project cleanly on all of the versions above. Looks like the drawElement canvas shim injects a canvas whose 2D context no longer carries the drawElementImage extension the streaming capture expects.

Workaround

Pinning the affected renders to npx hyperframes@0.7.37 while tracking latest everywhere else.