# 6.1 Fail closed

Trax treats every gap in authorization as a reason not to start. A train that declares who may run
it with no service to check it, a junction that asks for the caller where no caller can be
resolved, a demonstration signing key outside Development: each stops the host before it takes a
request, with a message that says which line to write. This chapter meets several of them on
purpose.

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Next: [6.2 Packages](/docs/book/customers-and-staff/packages)