[Bug]: Claude fails to connect to Blazorise mcp

[njannink]

Blazorise Version

2.2

Summary

The hosted docs MCP server at https://mcp.blazorise.com/mcp responds to JSON-RPC requests with an SSE-framed body (event: message\ndata: {…}) while setting the response header Content-Type: application/json. Clients that honor the declared content type try to JSON.parse the body, hit the leading event: token, and fail. In Claude Code this surfaces as:

Failed to reconnect to blazorise-docs: JSON Parse error: Unexpected identifier "event"

Environment

• Server: Blazorise.Docs.Mcp v1.0.0.0 (reported in serverInfo), hosted on Microsoft-IIS/10.0 / ASP.NET
• Endpoint: https://mcp.blazorise.com/mcp
• Client: Claude Code MCP client, transport type: "http" (Streamable HTTP)
• Client config (.mcp.json):
  {
  "mcpServers": {
  "blazorise-docs": { "type": "http", "url": "https://mcp.blazorise.com/mcp" }
  }
  }

Steps to reproduce

curl -i -X POST "https://mcp.blazorise.com/mcp"
-H "Content-Type: application/json"
-H "Accept: application/json, text/event-stream"
--data '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"probe","version":"0.0.0"}}}'

Actual response

HTTP/1.1 200 OK
Content-Type: application/json <-- declares JSON
Server: Microsoft-IIS/10.0
mcp-session-id: c2293eb794bf48d0a4c3d801f0f284b9
X-Powered-By: ASP.NET

event: message <-- but body is SSE framing
data: {"result":{"protocolVersion":"2025-06-18","capabilities":{"logging":{},"tools":{"listChanged":true}},"serverInfo":{"name":"Blazorise.Docs.Mcp","version":"1.0.0.0"}},"id":1,"jsonrpc":"2.0"}

The header and the body disagree: the payload is an event:/data: SSE event, but the Content-Type says application/json.

Expected behavior

Per the MCP Streamable HTTP spec, the server must make the body match the content type:

• If it streams events → set Content-Type: text/event-stream (so the client runs its SSE parser), or
• If it sets Content-Type: application/json → return the bare JSON-RPC object with no event:/data: lines.

Currently it does neither (SSE body + JSON header), so any client that picks its parser from Content-Type fails to initialize.

Suggested fix

Set the response Content-Type to text/event-stream whenever the handler emits SSE framing (this is almost certainly a content-negotiation/content-type bug in the IIS/ASP.NET MCP transport layer — the body is correct, only the header is wrong). Echoing back the Accept negotiation correctly would also resolve it.