Config Over Constants

• Define a value once and reference it, in code, in shell scripts, in CI and in task runners
• Paths, hostnames, ports, versions and timeouts are variables, never inline literals
• When the same literal appears a second time, that is the signal to name it
• Read deployment specific values from the environment, with a documented default
• Do not duplicate a block of logic to handle a variant, parameterise the original
• Duplication in tests is acceptable when it makes the assertion clearer