[BUG] Ctrl+O (collapse toggle) on MCP tool calls from disconnected server removes them from display

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?

When using Ctrl+O (the expand/collapse toggle) on an MCP tool call whose MCP server has since disconnected, the tool call block and its output are completely removed from the display instead of being collapsed. Pressing Ctrl+O -> Esc twice reliably triggers this.

This makes it impossible to review what MCP tools were called or what they returned earlier in the conversation. The user has no way to verify whether the AI actually performed an action or is hallucinating results.

What Should Happen?

Ctrl+O should collapse/expand MCP tool call blocks the same way it does for built-in tools (Bash, Read, etc.), regardless of whether the originating MCP server is still connected. The tool call and its output should never be removed from the display.

Steps to Reproduce

1. Connect a streamable HTTP MCP server (tested with both firefox-mcp and thunderbird-mcp)
2. Have Claude call an MCP tool (e.g., listTabs or listAccounts)
3. Observe the tool call and output are displayed correctly
4. Disconnect the MCP server (either manually, or it may disconnect on its own)
5. Press Ctrl+O on the MCP tool call block, then Esc
6. The tool call and output vanish entirely from the display

Additional observations:

• Both MCP servers tested use the streamable HTTP transport
• Built-in tools (Bash, Read, Grep, etc.) are not affected — Ctrl+O correctly collapses/expands them
• If the MCP server is still connected, Ctrl+O works correctly on MCP tool calls too
• The bug only manifests when the MCP server has disconnected since the tool was called
• This can make it appear as though tool calls never happened, which is confusing when trying to follow what Claude did

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.85 (Claude Code)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Alacritty

Additional Information

Tested with two different streamable HTTP MCP servers (firefox-mcp and thunderbird-mcp) — the behavior is consistent across both. The Firefox MCP server also disconnects when Ctrl+O -> Esc is pressed on its tool calls, but that may be a server-side issue rather than a Claude Code bug. Not tested with stdio MCP servers.