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render: --variables-file (and --variables <path>) fails with "io.readFile is not a function" since 0.8.212

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@miguel-heygen is already working on this.

Since Oct 30, 2026.

  • #6831 by @miguel-heygen — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
node.js, typescript
Domain
cli

Research direction

Trace render --variables-file, --variables <path>, and --variables - into resolveVariablesArg and parseVariablesArg; the issue identifies how undefined I/O callbacks override defaults in readJsonFlagText. Read the relevant CLI implementation and its tests, then run focused tests for file and stdin inputs. Done when those inputs parse successfully while inline JSON and --batch behavior still works.

Written by the indexing model from the issue text.

Description

bug triage/needs-triage
Describe the bug

hyperframes render --variables-file <file> fails before rendering on every version from 0.8.212 to 0.8.221 (latest at the time of writing). The same failure hits --variables <path> and --variables - (stdin). Inline JSON (--variables '{"title":"x"}') and --batch <file> still work.

Minimal reproduction

Any project with data-composition-variables:

echo '{}' > /tmp/vars.json
npx -y [email protected] render . --variables-file /tmp/vars.json -o /tmp/out.mp4

✗  Could not read the variables JSON
   /tmp/vars.json: io.readFile is not a function
Version --variables-file
0.8.210, 0.8.211 reads the file, render proceeds
0.8.212, 0.8.213, 0.8.216, 0.8.221 io.readFile is not a function

Linux (WSL2 Ubuntu), Node 24.19.0.

Cause (from the published dist of 0.8.221)

resolveVariablesArg(inline, filePath) calls parseVariablesArg(inline, filePath) with no readFile / readStdin, so it passes { readFile: undefined, readStdin: undefined } to readJsonFlagText:

function readJsonFlagText(value, partialIo = {}) {
  const io = { ...defaultIO, ...partialIo };   // undefined overrides the defaults
  ...
  return trimmed === "-" ? io.readStdin() : io.readFile(value);

An object spread copies keys whose value is undefined, so io.readFile is undefined.

Steps to reproduce
echo '{}' > /tmp/vars.json
npx -y [email protected] render . --variables-file /tmp/vars.json -o /tmp/out.mp4
Expected behavior

A rendered mp4 using the variables file is created

Actual behavior

◆ Rendering variables-fixture → C:\node_projects\hftemptest\out.mp4
30fps · standard · auto workers (16 cores detected)
GPU: browser GPU (auto-detect)

✗ Could not read the variables JSON

vars.json: io.readFile is not a function

Environment
The failed checks (unzip, FFmpeg, optional tools) are unrelated: the error is thrown while the flag is parsed, before any browser or encoder is touched.


hyperframes doctor
  ✓ Version          0.8.221 (latest)
  ✓ Node.js          v24.19.0 (linux x64)
  ✓ CPU              16 cores · Intel(R) Core(TM) Ultra 7 265H
  ✓ Memory           15.6 GB total · 6.0 GB available
  ✓ Disk             925.5 GB free
  ✓ Frames cache     /tmp/hyperframes-extract-cache-1000 · 925.5 GB free at /tmp · default
  ✗ Archive extractor Not found
  ✓ Settings lock    Not locked
  ✓ /dev/shm         7995 MB
  ✓ Environment      WSL · non-TTY
  ✗ whisper-cpp      Not found (optional — needed for transcription)
  ✗ TTS (Kokoro)     Not installed (optional — local voice fallback)
  ✗ BGM (MusicGen)   Not installed (optional — local music fallback)
  ✓ onnxruntime-node Not installed (installs on first use)
  ✓ @google/genai    Not installed (installs on first use)
  ✗ FFmpeg           FFmpeg is required to encode video.
  ✗ FFprobe          FFprobe is required to probe media assets.
  ✓ Chrome           cache: ~/.cache/hyperframes/chrome/chrome-headless-shell/linux-152.0.7977.30/...
  ✓ Docker           Docker version 29.6.2, build dfc4efb
  ✗ Docker running   Not running
Additional context

No response

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Merged PRs (30d)
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