Encore.ts unit test run returning runtime panic on Actions CI

Is there an existing issue for this?

• I have searched the existing issues

What part(s) of Encore does this bug report apply to?

• Encore.ts (TypeScript)
• Encore.go (Go)
• Encore CLI
• Local Development Dashboard
• Encore Cloud

Current behavior

Minimum reproduction code

No response

Steps to reproduce

Simply run any test fixture from a sample repository that has Prisma migrations, and run an actions workflow, similar to this

name: CI

on:
  pull_request:
  push:
    branches:
      - main

permissions:
  contents: read

jobs:
  backend-unit:
    name: Backend Unit Tests
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v6

      - name: Setup Node.js
        uses: actions/setup-node@v6
        with:
          node-version: 24
          cache: npm

      - name: Install dependencies
        run: npm ci

      - name: Install Encore CLI
        run: |
          curl -L https://encore.dev/install.sh | bash
          echo "$HOME/.encore/bin" >> "$GITHUB_PATH"

      - name: Disable Encore telemetry
        run: encore telemetry disable

      - name: Export Encore runtime library
        run: echo "ENCORE_RUNTIME_LIB=$(encore daemon env | grep ENCORE_RUNTIME_LIB | cut -d'=' -f2)" >> "$GITHUB_ENV"

      - name: Run unit tests
        run: npm run test:unit

Expected behavior

Tests should run normally without any issues

Encore CLI version

1.57.6

Node.js version

Latest LTS

In which operating systems have you tested?

• macOS
• Windows
• Linux

Other

Currently our Vitest unit tests were recently failing without any more detailed logs, these were relatively unchanged and has been working fine until 1.57.6 where it worked for a period of time until we started seeing flaky builds and now an outright error.

This was reproducible on our code when run in GitHub Actions, using the recommended Vitest approach.