Runtime Compatibility for Excel Custom Functions using a Shared Runtime

[mason-krause]

Expected behavior

Please describe the behavior you were expecting

Shared Runtime Add-in should load in Trident when WebView2 isn't available according to docs but is running is Edge Legacy

https://learn.microsoft.com/en-us/office/dev/add-ins/develop/configure-your-add-in-to-use-a-shared-runtime?tabs=jsonmanifest#about-the-shared-runtime

Current behavior

When loading my shared runtime add-in with Windows 10 w/o WebView2, it loads in Edge legacy, not Trident. It also fails to load my custom functions in Edge runtime on the first load, but it I select "Reload" from the Personality menu, everything loads properly including custom functions, and there doesn't seem to be any issue with Edge legacy compatibility.

This is just an issue with the initial load which is easily fixed. The problem was observed on a brand new Shared Runtime Custom Functions add-in from Yeoman Generator, and a completed Shared Runtime add-in I am trying to publish on the Microsoft Partner Center. My add-in keeps failing certification because it is not compatible with Edge legacy runtime. It appears to work fine though once reloaded which I've explained but it hasn't made a difference in certification process. According to the documentation, it should load in Trident anyway, so I'm not sure why this issue is happening.

I've also enabled logging with office-addin-dev-settings and attached the VS Code debugger and looked at the dev tools console and none of these three tools are giving me any output on the issue.

Steps to Reproduce

Please provide detailed steps for reproducing the issue.

1. Have Windows 10 environment w/o Webview2
2. Run npx yo office
3. Select project type: Excel Custom Functions using a JavaScript-only Runtime
4. run npm run start
5. add-in fails to load- task pane appears, but "CONTOSO.ADD", "CONTOSO.CLOCK", etc custom functions aren't available; no output is available in browser console, VS code debugger, or office-addin-dev-settings logs
6. Runs fine after reload from Personality Menu; Partner Center reviewers won't do this step however

Context

Please provide any relevant information about your setup. This is important in case the issue is not reproducible except for under certain conditions.

• Operating System: Windows 10
• Node version: 24.9.0
• Office version: Excel 2508 Build 19127.20264
• Tool version: 11.6.0

Failure Logs

Please include any relevant log snippets, screenshots or code samples here.