diff --git a/filters/audits/ibm-i.md b/filters/audits/ibm-i.md
new file mode 100644
index 000000000..dfbe165fe
--- /dev/null
+++ b/filters/audits/ibm-i.md
@@ -0,0 +1,40 @@
+# IBM i / AS400 normalization and rule review
+
+Keep hostnames and unspecified addresses out of the standard IP field while retaining source values.
+
+This draft targets UTMStack `v11`. It contains 1 filter changes
+and 0 rule changes for this technology only. Review covered
+1 filter configurations and 8 matching shipped rule files.
+Unchanged rules are listed in the regression manifest; they are not duplicated in the diff.
+
+## Contract and validation
+
+- Compared exact standard names/types with go-sdk v1.1.31 and the supplied UTMStack dictionaries.
+- Checked documented pipeline ordering, rename/move behavior, open vendor log fields,
+  event-side versus alert-side fields, and surviving fields used by affected rule predicates/history/grouping.
+- Strict SDK configuration decoding and actual CEL compilation pass for this scope.
+- 2 synthetic normalization cases pass, including SDK Event conversion and any
+  trigger predicate assertions recorded in the manifest.
+- The scoped alerts module tests and `git diff --check` pass with the shared contract runner applied.
+
+The shared alert-contract PR supplies the reusable Go runner for the manifest in
+`plugins/alerts/testdata/filter-contracts/ibm-i.json`. Apply that support before running `go test ./...` in `plugins/alerts`.
+
+The model starts from synthetic extraction results. It does not run complex grok,
+JSON/KV/XML/CSV extraction, time conversion, dynamic plugins, historical OpenSearch
+queries, or the closed EventProcessor. Raw vendor logs and resulting alerts must
+still be checked in staging before rollout. No customer false-positive reduction
+has been measured and no production rollout is included.
+
+
+
+## References
+
+- [SDK schema](https://github.com/threatwinds/go-sdk/blob/v1.1.31/plugins/plugins.proto)
+- [Filter steps](https://github.com/threatwinds/go-sdk/wiki/Filter-Steps-Reference)
+- [Standard event schema](https://github.com/threatwinds/go-sdk/wiki/Standard-Event-Schema)
+- [Rule implementation](https://github.com/threatwinds/go-sdk/wiki/Implementing-Rules)
+
+`afterEvents`, empty noncapturing grok names, supported numeric strings, and custom
+`log.*` fields are accepted. Existing textual protocol casing and vendor action names
+are preserved unless a concrete consumer mismatch requires correction.
diff --git a/filters/ibm/ibm_as_400.yml b/filters/ibm/ibm_as_400.yml
index 11522baef..0ccdf0ef8 100644
--- a/filters/ibm/ibm_as_400.yml
+++ b/filters/ibm/ibm_as_400.yml
@@ -85,4 +85,11 @@ pipeline:
           params:
             source: origin.ip
             destination: origin.geolocation
-          where: exists("origin.ip")
\ No newline at end of file
+          where: exists("origin.ip")
+
+      # Keep addresses in IP fields and retain other source values under log.
+      - rename:
+          from:
+          - origin.ip
+          to: log.unparsedOriginIp
+          where: exists("origin.ip") && (!(inCIDR("origin.ip","0.0.0.0/0") || inCIDR("origin.ip","::/0")) || oneOf("origin.ip",["0.0.0.0","::"]))
diff --git a/plugins/alerts/testdata/filter-contracts/ibm-i.json b/plugins/alerts/testdata/filter-contracts/ibm-i.json
new file mode 100644
index 000000000..1248b2c05
--- /dev/null
+++ b/plugins/alerts/testdata/filter-contracts/ibm-i.json
@@ -0,0 +1,48 @@
+{
+  "technology": "IBM i / AS400",
+  "filters": [
+    "filters/ibm/ibm_as_400.yml"
+  ],
+  "rules": [
+    "rules/ibm/ibm_as_400/as400_audit_journal_disable.yml",
+    "rules/ibm/ibm_as_400/as400_exit_point_tampering.yml",
+    "rules/ibm/ibm_as_400/as400_ifs_access.yml",
+    "rules/ibm/ibm_as_400/as400_job_queue_manipulation.yml",
+    "rules/ibm/ibm_as_400/as400_library_list_manipulation.yml",
+    "rules/ibm/ibm_as_400/as400_program_adopt_abuse.yml",
+    "rules/ibm/ibm_as_400/as400_remote_command.yml",
+    "rules/ibm/ibm_as_400/as400_sql_injection.yml"
+  ],
+  "fixtures": [
+    {
+      "name": "ibm_valid_source_ip",
+      "filter": "ibm/ibm_as_400.yml",
+      "input": {
+        "origin": {
+          "ip": "2001:db8::7"
+        }
+      },
+      "expected": {
+        "origin.ip": "2001:db8::7"
+      },
+      "absent": [],
+      "rules": {}
+    },
+    {
+      "name": "ibm_hostname_not_ip",
+      "filter": "ibm/ibm_as_400.yml",
+      "input": {
+        "origin": {
+          "ip": "lab-host"
+        }
+      },
+      "expected": {
+        "log.unparsedOriginIp": "lab-host"
+      },
+      "absent": [
+        "origin.ip"
+      ],
+      "rules": {}
+    }
+  ]
+}