Track WSDL and schema changes as operational events so regenerated SOAP clients never surprise production.
WSDL monitoring is contract observability. Capture a checksum or canonical diff of the live WSDL and any imported schemas, compare it with the version your client was generated from, and alert when the contract changes outside your planned deployment flow. That tells you whether a sudden SOAP incident is likely to be carrier drift rather than a local regression.
Diff monitoring matters most around maintenance windows, endpoint migrations, and sunset deadlines. Pair it with generated-client review and safe contract tests so one changed element name does not silently break the next scheduled job.