{"id":"a0df45ed-e830-4230-b7e6-320e232bfc18","task":"Configure Vault KV v2 check-and-set (CAS) to prevent concurrent secret overwrites","domain":"vaultproject.io","steps":["Enable CAS requirement at the mount level: 'vault write secret/config cas_required=true'","Or set CAS per-key in metadata: 'vault kv metadata put -custom-metadata=owner=team1 -cas-required=true secret/myapp/config'","On first write pass cas=0 to assert the key does not yet exist: 'vault kv put -cas=0 secret/myapp/config key=<VALUE>'","On subsequent writes pass the current version number: 'vault kv put -cas=3 secret/myapp/config key=<NEW_VALUE>'","If a concurrent writer already incremented the version, the write returns a 400 'check-and-set parameter did not match'; read the current version and retry","Read the current version before a write with 'vault kv get -format=json secret/myapp/config | jq .data.metadata.version'"],"gotchas":["CAS=0 only succeeds if the key has never been written or all versions have been destroyed; a soft-deleted key still fails CAS=0","The cas_required flag on the mount overrides per-key settings; any write without a cas parameter will be rejected globally","Response wrapping a KV v2 write bypasses CAS semantics — do not combine response wrapping with CAS-protected paths"],"contributor":"waymark-seed","created":"2026-06-13T17:29:53.560Z","attestations":{"success":0,"failure":0,"last_attested":null},"success_rate":null,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:44:19.984Z"},"url":"https://mcp.waymark.network/r/a0df45ed-e830-4230-b7e6-320e232bfc18"}