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claude-code - 💡(How to fix) Fix [BUG] Tools of a custom MCP server are visible on claude.ai/code but not via Claude Code in mobile app [1 participants]

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anthropics/claude-code#51719•Fetched 2026-04-22 07:54:40
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Preflight Checklist

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

What's Wrong?

I have a custom MCP server connected, called "woc".

It is accessible on desktop web via claude.ai/code, but appears to be inaccessible / unusable on the Claude Code mobile app.

Compare the two sessions:

  1. Desktop web https://claude.ai/code/session_01HFNQev4FAZW5TxQcvejUMo - works fine, lists the tools that the MCP server exposes.
  2. Exact same query initiated from Claude Code mobile app (on Android, Pixel 9 Pro) https://claude.ai/code/session_01H8cTx3eX74e8jzMwjQvcGG - shows that no tools from the "woc" MCP server are visible to ToolSearch.

I have tried disconnecting and reconnecting the server from my mobile app and it hasn't helped.

This appears to be an issue specific to where the session is initiated - when I pick the second session on claude.ai/code and issue a query from desktop web, it still shows no tools from the MCP server being accessible.

What Should Happen?

Tools from the connected MCP server should be accessible to sessions initiated from Claude Code in the mobile app.

Error Messages/Logs

Steps to Reproduce

  1. Create and deploy a custom MCP server with a few tools (or, I suppose, connect to any MCP server)
  2. Connect it to Claude Code
  3. Open Claude Code in the mobile app
  4. Ask what tools are available from that server

Claude Model

None

Is this a regression?

I don't know

Last Working Version

No response

Claude Code Version

Android app version 1.260416.20

Platform

Other

Operating System

Other

Terminal/Shell

Other

Additional Information

Session initiated from claude.ai/web: <img width="1048" height="860" alt="Image" src="https://github.com/user-attachments/assets/9ee0a8ef-c25c-4c70-9a9f-a068c8209016" />

Session initiated from Claude Code Android app (and then opened to take screenshot in claude.ai/web): <img width="1041" height="854" alt="Image" src="https://github.com/user-attachments/assets/34801eb5-29cd-4f8b-b7c8-d2bdd563b85e" />

extent analysis

TL;DR

The issue might be related to differences in how sessions are handled or initialized between the desktop web and mobile app versions of Claude Code, affecting the visibility of tools from a custom MCP server.

Guidance

  • Verify that the MCP server connection settings are identical for both desktop web and mobile app sessions to ensure consistency.
  • Check if there are any session-specific configurations or flags in the Claude Code mobile app that might be influencing the visibility of tools from the MCP server.
  • Compare the network requests or API calls made by the desktop web and mobile app sessions to identify any differences in how they interact with the MCP server.
  • Test if the issue persists when using a different mobile device or platform to isolate if it's specific to the Android or Pixel 9 Pro environment.

Example

No specific code example can be provided without more details on the internal workings of Claude Code or the MCP server integration. However, ensuring that the session initialization and MCP server connection logic is consistent across platforms could involve reviewing and comparing the relevant code segments for desktop web and mobile app versions.

Notes

The root cause of the issue is not immediately clear due to the lack of detailed technical information about the Claude Code architecture and the MCP server integration. Further investigation into the session management and API interactions between the desktop web, mobile app, and MCP server is necessary.

Recommendation

Apply workaround: Given the uncertainty around the root cause, a practical next step would be to apply a workaround by manually configuring or forcing the mobile app session to mimic the desktop web session settings as closely as possible, to see if this resolves the issue of tool visibility from the MCP server.

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claude-code - 💡(How to fix) Fix [BUG] Tools of a custom MCP server are visible on claude.ai/code but not via Claude Code in mobile app [1 participants]