fix(stdio): always set windowsHide on Windows, not just in Electron

[felixweinberger]

Forward-port of #1640 to main. Fixes #1638.

Motivation and Context

StdioClientTransport only sets windowsHide when running in Electron, causing unwanted console windows to appear in non-Electron Windows applications when spawning stdio MCP servers.

How Has This Been Tested?

Added unit tests in crossSpawn.test.ts that mock spawn and assert the windowsHide option is set correctly per platform.

Breaking Changes

None. windowsHide is a no-op on non-Windows platforms.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

Original fix by @jnMetaCode in #1640 (v1.x). Also supersedes #1104 and #1706.

[changeset-bot]

🦋 Changeset detected

Latest commit: 8b49ceb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@modelcontextprotocol/client	Patch

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commit: 8b49ceb

[claude]

LGTM — straightforward fix removing the unnecessary Electron guard from windowsHide, with good test coverage.

Extended reasoning...

Overview

This PR makes a single-line change in packages/client/src/client/stdio.ts to always set windowsHide: true on Windows when spawning stdio server processes, rather than only doing so in Electron environments. The now-unused isElectron() helper is removed. Two new unit tests in crossSpawn.test.ts verify the behavior on both Windows and non-Windows platforms. A changeset file is included.

Security risks

None. windowsHide is a cosmetic spawn option that suppresses console window creation on Windows. It has no security implications and is a no-op on non-Windows platforms.

Level of scrutiny

Low scrutiny is appropriate. This is a minimal, well-scoped bug fix that changes one boolean expression, removes dead code, and adds tests. It is a forward-port of an already-merged fix (#1640) from the v1.x branch.

Other factors

The change is non-breaking, has proper test coverage, includes a changeset, and follows the established patterns of the codebase. No outstanding reviewer comments exist. The PR cleanly addresses a known issue (#1638) with multiple prior related PRs (#1104, #1706).