[BUG] Claude Mobile (Android) don't sends Mcp-Session-Id in MCP Streamable HTTP Sessions

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Basically, I'm having the following problem (sorry for the way I reported it, but I couldn't find a better one). I'm testing a Remote MCP that runs on Streamable HTTP. This MCP relies heavily on the Mcp-Session-Id. In Claude Desktop, it runs without any issues. In fact, my MCP has already passed the QA tests I had prepared for it before continuing to scale it.

However, in Claude Mobile Android (I don't know if the same thing will happen on iOS), since the Mcp-Session-Id isn't sent, the tools that try to run the model, since they depend on a previous state, simply report that the state has been corrupted or that it doesn't exist at all.

What Should Happen?

Basically, in Claude Mobile Android calls, send the Mcp-Session-Id for the Stateful Remote MCPs.

Error Messages/Logs

Steps to Reproduce

• Create an MCP that depends on the Mcp-Session-Id.
• Deploy it to a URL accessible through the Claude Desktop backend and configure it in Claude Desktop.
• Go to Claude Mobile Android.
• Try to make the model run a tool that depends on the Mcp-Session-Id.
• Note that it is not actually being sent. :)

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

1.250915.17 (Android)

Platform

Anthropic API

Operating System

Other

Terminal/Shell

Other

Additional Information

_No response_