[Bug] Streamable HTTP MCP Server Use

[jsmith13]

Which Microsoft Discovery surface?

Microsoft Discovery app (Windows desktop client)

For Services bugs only — which area in this repo?

N/A — this is an app bug

Specific catalog item (Services only)

No response

Microsoft Discovery app version

No response

OS version (app only)

No response

What were you trying to do?

Connect a streamable HTTP MCP server as a tool

Steps to reproduce

1. Provide MCP endpoint to Discovery Express through the Add Tool option on the command pallet.
2. Ask the copilot panel to access it. (Similar results are seen via the Engine interface.)

Expected behavior

The tools on the server are available for use by the agent.

Actual behavior

• The copilot side panel is not able to access my MCP server after I’ve added it as a tool source.
• The MCP server uses streamable HTTP and requires authorization headers. When I attach it directly to GitHub Copilot CLI, gh cli naively pings the server, receives information on required authentication, then uses that authentication from there on out. In Discovery Express, I am not seeing this behavior.
• After providing the copilot panel a working python script for establishing the MCP connection, it successfully authenticated.
• Once auth has succeeded, there seems to be an issue interacting via the streamable HTTP MCP spec. The session id returned on initiation is not being provided in the headers of proceeding calls.

Logs and diagnostics

No response

Severity

Blocking — I cannot make progress

Confirmations

• I have searched existing Bugs discussions before posting.
• This report contains no sensitive, regulated, or proprietary data (no subscription IDs, tenant IDs, tokens, customer data, etc.).
• If this is a Services bug, it concerns catalog content in this repo (agent, starter-kit, tool, skill, docs, or utility) — not general Discovery services platform issues. (Tick N/A if this is an app bug.)

[stevetru1]

Thank you for reporting this (and the other bugs) - we are seeing some reversions in this tool system in the 0.15.0 version and I've added internal tracking bugs to resolve on each issue you reported. I don't have a fix ETA yet but we will update once resolved.

[stevetru1]

Tracking ID 2839467