Microsoft Edge's built-in Copilot does not render text messages when they come from an agent

The response is reaching the conversation but failing to display specifically in Edge, so capture an Edge reproduction and submit it through Edge feedback and your Microsoft 365 administrator rather than changing the agent implementation.

The screenshot shows the agent header and response actions in Edge while the identical turn displays its text in the desktop app. That is not the documented symptom of an agent failing to generate a response, and there is no published Microsoft fix specifically for Edge 155.0.4283.62 with an Agents SDK text response.

Capture and report the Edge-only failure

1. In Edge, press Alt+Shift+I to open Send feedback.
2. Describe the issue as:
   “Published Microsoft 365 Agents SDK agent response body is blank in Edge Copilot, while the same conversation turn renders in the Microsoft 365 Copilot desktop app.”
3. Include:
   • Edge version 155.0.4283.62
   • Windows version
   • Work/school account type
   • Agent/app version and publishing scope
   • Approximate timestamp and time zone
   • Screenshot comparing both clients
   • Whether every plain-text agent reply is affected
4. Enable diagnostic-data submission and reproduce the problem while recording, if that option is offered. Edge supports direct feedback through Alt+Shift+I, including diagnostics.^1^
5. Have a Microsoft 365 Global Admin open a support request in the Microsoft 365 Admin Center and attach the same evidence. Similar channel-specific blank agent responses require tenant-level investigation when the agent succeeds in another client.^2^

Before collecting the reproduction, optional Edge diagnostics can be enabled under Settings and more → Settings → Privacy, search, and services → Privacy → Send optional diagnostic data to improve Microsoft products, followed by an Edge restart.^3^

Add high-signal diagnostic information

Collect these items for the support case:

• edge://settings/help: full Edge version.
• edge://policy: select Export to JSON and attach the exported policy list.
• edge://settings/appearance/copilotAndSidebar: screenshot the sidebar settings.
• The activity/conversation identifiers from the agent telemetry, with any secrets or personal content removed.
• A server-side trace showing the outbound activity type and text length—not the confidential response body.
• Results from the same prompt in:
  • Edge Copilot
  • Microsoft 365 Copilot desktop
  • Teams, if the agent is available there
  • Microsoft 365 Agents Playground

Microsoft’s Edge diagnostic guidance specifically requests the browser version, active policies, sidebar settings, account type, and operating-system version for support investigations.^4^ The Agents SDK documentation also provides the Agents Playground as a supported test surface.^5^

Conditional Edge policy check

This check applies only if edge://policy shows:

• EdgeSidebarAppUrlHostBlockList set to *, and
• an explicit EdgeSidebarAppUrlHostAllowList.

Because Edge 155 is later than Edge 146, the allow list must include:

• edge://discover-chat
• edge://commercial-copilot-chat
• chrome-untrusted://commercial-copilot-chat

Add missing entries through Group Policy, Intune, or the applicable MDM system, then restart Edge. Microsoft documents those additional internal URLs as required from Edge 146 onward in wildcard-block environments.^6^

However, this policy issue normally prevents Copilot Chat from loading. Since the conversation shell, agent identity, and response controls already render, it is a fallback check rather than an established explanation for the missing text.

Do not reset or republish the agent solely for this symptom: the same published response already renders in the desktop client. Also, Adaptive Card domain settings are not relevant if the failing activity is an ordinary plain-text message rather than a card or external media response.

References

1. Accessibility with the new Microsoft Edge | Microsoft Support
2. The Copilot Agent was unable to respond few times when asked from the Teams - Microsoft Q&A
3. Microsoft Edge, browsing data, and privacy | Microsoft Support
4. Copilot icon doesn't appear in Microsoft Edge sidebar
5. Microsoft 365 Agents SDK documentation | Microsoft Learn
6. Fix Copilot Chat loading issues in Edge Sidebar - Microsoft Edge