Deploying nextjs app with pnpm causes Webapp warmup timeout

[brianmgray]

Description
I have a Github Actions workflow that has been successfully deploying my nextjs app using npm to Azure Static Webapps for a few weeks. I migrated to pnpm for improved dependency management- it was a few lines of code to change. This builds fine locally, but on Github, the build consistently fails with this message:

Finished Upload. Polling on deployment.
Status: InProgress. Time: 0.0557385(s)
....
Status: InProgress. Time: 574.5292073(s)
Status: Failed. Time: 589.5829263(s)
Deployment Failed :(
Deployment Failure Reason: Web app warm up timed out. Please try again later.

Note: typically before this change this check would take about 20 seconds before I get a valid response from the app and the build completes.

To Reproduce

Here are the key files involved (I can't link directly to source, private repo).

# pr.yml
name: Build and deploy (PR)

on:
  pull_request:
    types: [opened, synchronize, reopened]
    branches:
      - main
  workflow_dispatch:

jobs:
  exec:
    uses: ./.github/workflows/build-and-deploy.yml
    secrets: inherit
    with:
      preview: true

# build-and-deploy.yml
name: Build and deploy
...
jobs:
  build_and_deploy:
    name: Build and Deploy
    runs-on: ubuntu-latest
    ...
    steps:
      ...
      - name: Use pnpm ${{ env.PNPM_VERSION }}
        uses: pnpm/action-setup@v3
        with:
          version: ${{ env.PNPM_VERSION }}
      - name: Use Node.js ${{ env.NODE_VERSION }}
        uses: actions/setup-node@v4
        with:
          node-version: ${{ env.NODE_VERSION }}
      - name: Install
        run: |
          # force a development install, to make sure dev dependencies are installed
          # they get filtered out by the standalone build for next
          NODE_ENV=development pnpm install

      - name: Build
        run: pnpm run build

      - name: Test
        run: pnpm run test

      - name: Deploy
        id: deploy
        if: ${{ !env.ACT || env.DEPLOY == 'true' }}
        uses: Azure/static-web-apps-deploy@v1
        with:
          azure_static_web_apps_api_token: ${{ secrets.AZURE_STATIC_WEB_APPS_API_TOKEN }}
          repo_token: ${{ secrets.GITHUB_TOKEN }} # Used for Github integrations (i.e. PR comments)
          action: "upload"
          skip_app_build: true
          skip_api_build: true
          app_location: ${{ env.APP_LOCATION }}
        env:
          skip_deploy_on_missing_secrets: true

Expected behavior
Deployment would succeed and I would be able to access the static web app at the preview URL provided by the build.

Screenshots
n/a

Device info (if applicable):
n/a

Additional context
Not sure what else would help, let me know!