Claude Code checks that the path to a helper program is a safe, ordinary local path. That check now also rejects paths that start with the Windows \??\ prefix (written as /??/ with forward slashes). The error message now spells out every rule. The path must be a local absolute path (Windows: C:/... or C:\...) and must not:
use ~, .., UNC paths or the \??\ prefix
contain ", %, carriage return, line feed or NUL characters
end with a dot or a space
Why
A helper path starting with \??\ is now refused. If you set one up, the error message tells you which rules the path has to follow.
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtThe finding does not say which setting supplies the helper path.
Anthropic's release notes agreeChanged Claude apps gateway to refuse to start when a managedMcpServers entry's envHelper path starts with \??\ or /??/, a path form current…
