fix: Windows Claude Desktop stdio + Codex beta/timeout config #650
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The cmd.exe /c wrapper was causing stdio pipe issues on Windows, resulting in "Server disconnected" errors in Claude Desktop. Testing confirmed that calling uvx.exe directly works reliably. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Reviewer's guide (collapsed on small PRs)Reviewer's GuideThis PR simplifies how Claude Desktop MCP configs are generated on Windows by removing the special cmd.exe wrapper logic and always invoking uvx.exe directly, eliminating a problematic stdio indirection while keeping argument construction unchanged. Sequence diagram for MCP server launch without cmd.exe wrappersequenceDiagram
actor User
participant ClaudeDesktop
participant ConfigJsonBuilder
participant OSProcess
User->>ClaudeDesktop: Start MCP server
ClaudeDesktop->>ConfigJsonBuilder: Generate config for McpClient
ConfigJsonBuilder->>ConfigJsonBuilder: BuildUvxArgs(fromUrl, packageName)
ConfigJsonBuilder-->>ClaudeDesktop: command = uvxPath
ConfigJsonBuilder-->>ClaudeDesktop: args = toolArgs
ClaudeDesktop->>OSProcess: Launch uvxPath with args via stdio
OSProcess-->>ClaudeDesktop: MCP protocol over stdio
ClaudeDesktop-->>User: MCP server connected
Updated class diagram for ConfigJsonBuilder command resolutionclassDiagram
class ConfigJsonBuilder {
+PopulateUnityNode(JObject unity, string uvPath, McpClient client) void
+BuildUvxArgs(string fromUrl, string packageName) IList~string~
}
class JObject
class McpClient
ConfigJsonBuilder --> JObject : uses
ConfigJsonBuilder --> McpClient : uses
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📝 WalkthroughWalkthroughRemoved Windows-specific command-shim logic and platform-detection helpers from Unity config generation; adjusted Codex config builder to use beta/prerelease arg list and added a startup_timeout_sec entry for unityMCP in stdio paths. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Possibly related PRs
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- Use GetBetaServerFromArgsList() for consistent --prerelease handling - Add startup_timeout_sec = 60 to allow time for uvx package downloads Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
cmd.exe /cwrapper when generating Claude Desktop config on Windows--prerelease explicit)startup_timeout_sec = 60to Codex config for slower first-run package downloadsProblems Fixed
Claude Desktop on Windows
The
cmd.exe /cwrapper was causing stdio pipe issues, resulting in "Server disconnected" errors immediately after the MCP server started:Root cause:
cmd.exeinterferes with stdio piping in a way that breaks MCP protocol communication.Fix: Call
uvx.exedirectly instead of wrapping withcmd.exe /c.Codex CLI
--prerelease explicitflags for beta server mode (was manually adding--frominstead of usingGetBetaServerFromArgsList())Fix:
GetBetaServerFromArgsList()helper for consistent beta handlingstartup_timeout_sec = 60to generated configTesting
🤖 Generated with Claude Code
Summary by CodeRabbit
Refactor
New Features
Behavior Changes
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