[Bugs] I'm attempting to use the "create-canvas" tool (skill? extension?), however it doesn't render anything

[trangevi]

Mood: 😔
Category: Bugs

I'm attempting to use the "create-canvas" tool (skill? extension?), however it doesn't render anything in created the in-app tab

---

Field	Value
App version	1.0.10
OS	Windows 10.0.26100
Theme	GitHub
Path	/chat
Tenure	Week 3

[trangevi]

I asked copilot to summarize what was attempted when I was trying to debug locally, please see below. As I don't have full context on how this path works, please forgive any agent hallucinations that I don't know enough to correct.

Canvas panels render blank (no content visible)

Environment

• App: GitHub Copilot App (Tauri) v1.0.65
• OS: Windows
• Platform: win32-x64

Summary

All canvas panels (extension canvases and the built-in browser canvas) render as completely blank/white pages. No content is visible. The underlying HTTP servers are confirmed working and serve correct HTML.

Steps to Reproduce

1. Create a session-scoped canvas extension via extensions_manage({ operation: "scaffold", kind: "canvas", ... })
2. Implement the extension with a loopback HTTP server (standard pattern from SDK docs)
3. Open the canvas via open_canvas
4. The panel opens with the correct title in the app chrome, but the content area is entirely blank

What We Tried

Test	URL	Result
Custom extension canvas	http://127.0.0.1:57273/	Blank
Custom extension canvas (localhost)	http://localhost:56464/	Blank
Built-in browser canvas (HTTP loopback)	http://127.0.0.1:57273/	Blank
Built-in browser canvas (HTTPS external)	Azure/azure-dev#9003	Blank
Same loopback URL in external browser	http://127.0.0.1:57273/	Works

Confirmed Working

• Extension loads successfully — extensions_manage inspect shows status: running
• HTTP server responds — Invoke-WebRequest returns HTTP 200 with correct HTML (3687 bytes)
• Canvas actions work — invoke_canvas_action("load_findings", ...) returns { ok: true, count: 2 }
• Content renders in external browser — opening the same localhost URL in Chrome/Edge shows the full page correctly
• Canvas panel chrome renders — the tab title ("PR Review Findings") appears correctly in the app; only the iframe content area is blank

Variations Tested (all blank)

• Inline <style> and <script> tags (in case CSP blocks them)
• External <link rel="stylesheet"> and <script src="..."> served from same loopback server
• Added Access-Control-Allow-Origin: * and X-Frame-Options: ALLOWALL headers
• Switched from 127.0.0.1 to localhost binding
• Minimal HTML with no CSS/JS at all
• HTTPS URL to a public site (github.com)

Conclusion

The Tauri webview used to render canvas iframe content does not display any embedded web content (HTTP or HTTPS, local or remote). This is an app-level rendering issue, not an extension or server issue. The extension code, HTTP responses, and canvas SDK integration are all correct and functional.

Possible Causes

• Tauri webview2 runtime misconfiguration or missing component
• GPU acceleration / hardware rendering issue affecting the embedded webview
• Security policy or enterprise group policy blocking webview content loading
• App-level CSP or iframe sandbox attribute preventing any content from rendering

[trangevi]

I noticed I had an app update, after installing that it seems to be working fine, although idk if that's a "have you tried turning it off and back on again" fix, or a fix in the latest update.