Hi, I’m testing a remote MCP server with **ChatGPT Developer Mode** and I’m trying to understand whether the following Cloudflare Tunnel errors are expected/benign or whether they indicate a compatibility issue.
**Setup**
* ChatGPT Plus, Developer Mode
* Remote MCP server exposed over HTTPS via Cloudflare Tunnel
* Public MCP URL: `https://<my-mcp-domain>/mcp`
* Origin: Serena running locally on `http://localhost:8000`
* Serena started with `--transport streamable-http --context chatgpt`
**Observed behavior**
The MCP setup appears to work, but Cloudflare Tunnel repeatedly logs errors like:
```text
ERR error="stream <id> canceled by remote with error code 0"
ERR Request failed error="stream <id> canceled by remote with error code 0" dest=https://<my-mcp-domain>/mcp
```
I removed the exact domain name and Cloudflare edge IPs for privacy.
To clarify: I am **not** saying the connection drops or that ChatGPT disconnects. The issue is that the tunnel produces these error messages during MCP use.
**Server-side behavior**
Serena itself starts normally:
* MCP server starts
* StreamableHTTP session manager starts
* Uvicorn listens on `0.0.0.0:8000`
* language server initializes successfully
So this does not look like a basic Serena startup problem.
**Questions**
1. Are these Cloudflare Tunnel messages expected when ChatGPT Developer Mode uses a remote MCP server over `streamable-http`?
2. Are there known issues with ChatGPT Developer Mode and Cloudflare Tunnel for MCP traffic?
3. Does ChatGPT currently require or strongly depend on tool annotations such as `readOnlyHint` for custom MCP servers?
4. Is there a recommended way to distinguish harmless tunnel log noise from a real MCP transport/protocol problem?