MCP tool call parameters display characters vertically (one character per line)

[elfenlieds7]

Description

When Claude Code displays MCP tool call parameters in the terminal UI, the characters are rendered vertically (one character per line) instead of horizontally on a single line.

Steps to Reproduce

1. Configure an MCP server in .mcp.json that has a tool with parameters
2. Call the MCP tool with parameters (e.g., response_format: "markdown")
3. Observe the tool call display in the terminal

Expected Behavior

Tool call parameters should display horizontally:

my_mcp_tool {"params": {"response_format": "markdown"}}

Actual Behavior

Each character of the parameter JSON is displayed on a separate line:

my_mcp_tool {
"
p
a
r
a
m
s
"
:
 
{
"
r
e
s
p
o
n
s
e
_
f
o
r
m
a
t
"
:
 
"
m
a
r
k
d
o
w
n
"
}
}

Environment

• OS: macOS Darwin 25.1.0
• Terminal: VS Code integrated terminal

Additional Context

This appears to be a rendering issue in how Claude Code displays MCP tool invocations. The tool itself works correctly and returns expected results - only the display is affected.

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