Excel Copilot WebView2 crashes when rendering download links - Bug

Further update with screenshots:

Excel Copilot generates a sandbox download-file reference, but the Excel Copilot UI displays the file reference as plain text rather than presenting an actionable download link/file control.

Issue:

Copilot in Excel does not render generated sandbox download files as actionable links/file controls.

Reproduction:

Ask Copilot in Excel to create a small test text file and provide the download. Copilot reports successful creation and displays Download sandbox-link-test.txt, but the displayed text is not an actionable download control. Expanding “Reasoned in 1 step” only displays the reasoning details.

Control:

Other WebView/browser links are displayed and usable.

Troubleshooting:

Windows/Excel environment rebooted and test repeated; behaviour remained the same.

Evidence:

Two screenshots showing collapsed and expanded reasoning states.

┌─────────────────────────────────────────────────────────────────┐

│ CLOUD SANDBOX                                                                                                                                          │ 

│ ┌─────────────┐                                                                                                                                 │  

│ │ Python code             │ → Creates file in sandbox                                                                                        │

│ └─────────────┘                                                                                                                                 │ └────────────────────────────┬────────────────────────────────────┘

                                                                           │

                                                                          ▼

┌─────────────────────────────────────────────────────────────────┐

│ EXCEL/OFFICE BROKER (Local)                                                                                                                        │

│ - Receives file from sandbox                                                                                                                           │

│ - Renders download link in WebView2   ← FAILURE POINT                                                                            │

│ - Saves to Documents\Copilot\Created\ ← NOT AVAILABLE                                                                          │

└─────────────────────────────────────────────────────────────────┘

Generate trivial file

        ↓

Copilot says file created

        ↓

Filename/reference appears

        ↓

No actionable download control

        ↓

Reboot Windows

        ↓

Repeat

        ↓

Same result

UPDATE - Further Debugging:

Confirmed via testing:

• Normal HTTPS links render correctly in WebView2 (not a general WebView2 failure)
• Can manually write to Documents\Copilot\Created\ via PowerShell (folder permissions OK)
• Hover states and JavaScript work normally in the panel

Conclusion: The failure is isolated to the **sandbox download broker pathway** - the component that transfers files from Copilot's cloud sandbox to local storage and renders the download link.

Suspected cause: A policy change (Defender Controlled Folder Access, Purview DLP, WebView2 GPO, or Office Connected Experiences policy) may be blocking the brokered download, and instead of showing an error, WebView2 crashes/blacks out.

IT investigation requested for: - WebView2-specific policies (separate from Edge browser GPOs) - Defender Controlled Folder Access events - ASR rules affecting EXCEL.EXE or msedgewebview2.exe - Windows Event Viewer logs for crash events