Failed GitHub MCP tool details render the server label one character per line

[scotttesler]

Describe the bug

Expanded details for failed GitHub MCP tool rows become extremely tall and difficult to read because (MCP: github-mcp-server) renders in an approximately one-character-wide column, with one character per line. Tool arguments below the label render at normal width.

Current behavior

The same display failure appears in two unrelated failed tool calls.

Edit pull request showed an error beginning:

MCP server 'github-mcp-server': An interactive form has been shown to the user for editing pull request ...

Search code showed an error beginning:

MCP server 'github-mcp-server': failed to search code with query 'repo:xai-org/grok-build model': GET https://api.github.com/search/code?page=1...

In both cases, the expanded MCP label rendered approximately as:

(
M
C
P
:

g
i
t
h
u
b
-
m
c
p
-
s
e
r
v
e
r
)

Affected version

Copilot CLI v1.0.74-4 on macOS, but this was encountered on previous versions.

Observed 2026-07-23.

Steps to reproduce the behavior

1. Run Copilot CLI v1.0.74-4 on macOS.
2. Invoke a GitHub MCP tool that returns a failed tool row. Observed examples include Edit pull request and Search code.
3. Expand the failed tool row.
4. Observe that (MCP: github-mcp-server) wraps one character per line while the content below it retains normal width.

Expected behavior

The MCP server label should remain horizontal and readable. At constrained widths, it should truncate or otherwise preserve a single-line layout instead of wrapping one character per line.

Additional context

This issue covers only the display/rendering bug. The invisible interactive form observed during Edit pull request is a separate problem and is explicitly out of scope.

Relevant configuration

The issue occurred with these non-secret user settings from ~/.copilot/settings.json:

{
  "autoUpdatesChannel": "prerelease",
  "experimental": true,
  "githubMcpInsiders": true,
  "enableAllGithubMcpTools": true
}

These are public user-facing options. No user-forced feature-flag overrides were configured, and the built-in GitHub MCP server was used rather than a custom server entry.

• copilot-cli/README.md

  Lines 66 to 95 in 2b809c8

  	Install with [Homebrew](https://formulae.brew.sh/cask/copilot-cli) (macOS and Linux):
  	```bash
  	brew install copilot-cli
  	```
  	```bash
  	brew install copilot-cli@prerelease
  	```
  	Install with [WinGet](https://github.com/microsoft/winget-cli) (Windows):
  	```bash
  	winget install GitHub.Copilot
  	```
  	```bash
  	winget install GitHub.Copilot.Prerelease
  	```
  	Install with [npm](https://www.npmjs.com/package/@github/copilot) (macOS, Linux, and Windows):
  	```bash
  	npm install -g @github/copilot
  	```
  	```bash
  	npm install -g @github/copilot@prerelease

• copilot-cli/README.md

  Lines 124 to 131 in 2b809c8

  	### Experimental Mode
  	Experimental mode enables access to new features that are still in development. You can activate experimental mode by:
  	- Launching with the `--experimental` flag: `copilot --experimental`
  	- Using the `/experimental` slash command from within the CLI
  	Once activated, the setting is persisted in your config, so the `--experimental` flag is no longer needed on subsequent launches.

• https://github.com/github/github-mcp-server/blob/eb088dfe9d854dab6453a8d4ae5871a5ced20974/docs/server-configuration.md#L336-L397
• https://docs.github.com/en/copilot/reference/copilot-cli-reference/cli-command-reference

Acceptance criteria

• Expanded failed GitHub MCP tool details render (MCP: github-mcp-server) horizontally at the observed width.
• At narrower widths, the label truncates or otherwise remains horizontal instead of wrapping one character per line.
• Tool error details and arguments retain a usable layout.
• Regression coverage includes a failed non-form GitHub MCP call, such as Search code.
• Resolving this issue does not require changes to interactive-form behavior.