diff --git a/security-case-types/oidc-browser-relying-party/README.md b/security-case-types/oidc-browser-relying-party/README.md
index 040e7e7..5a38071 100644
--- a/security-case-types/oidc-browser-relying-party/README.md
+++ b/security-case-types/oidc-browser-relying-party/README.md
@@ -129,6 +129,9 @@ uses them.
 
 ## History
 
+- **1.1 patch** (2026-10-10): `register-client` runs `keycape check-config`
+  (key-cape c528daa) through `keycape-client.py --check-config` on the live and
+  the proposed registry; apply refuses a registry KeyCape would refuse at start.
 - **1.1** (2026-10-10, minor): verification `consumer-enforces-groups`, and
   hand-over requires the consumer to enforce `access_groups`, because KeyCape has
   no per-client group gate (key-cape type review R2, key-cape 6038483). No new
diff --git a/security-case-types/oidc-browser-relying-party/type.yaml b/security-case-types/oidc-browser-relying-party/type.yaml
index dac9e5b..a6dbf28 100644
--- a/security-case-types/oidc-browser-relying-party/type.yaml
+++ b/security-case-types/oidc-browser-relying-party/type.yaml
@@ -219,7 +219,7 @@ spec:
         closed if the binding is missing.
     - id: register-client
       owner: net-kingdom
-      entry_point: "sso-mfa/k8s/keycape/keycape-client.py apply --client-file <client-from-case> --case-acceptance <record> (net-kingdom.keycape-client-registration)"
+      entry_point: "sso-mfa/k8s/keycape/keycape-client.py apply --client-file <client-from-case> --case-acceptance <record> --check-config <keycape binary> (net-kingdom.keycape-client-registration)"
       auth: "operator write access to the live KeyCape client registry in namespace sso"
       lane: key-cape-oidc-login
       warden_executes: false
@@ -234,8 +234,10 @@ spec:
         at startup and keeps login, authorization and handoff state in memory, so
         the restart drops in-flight logins and sessions for every client; runs go
         in a quiet window (key-cape type review R4). The rendered registry must
-        pass KeyCape's own client validation before the restart: a refused entry
-        stops the single replica and every client loses sign-in (R1).
+        pass KeyCape's own startup checks (keycape check-config, key-cape
+        c528daa, which keycape-client.py runs before it patches) before the
+        restart: a refused entry stops the single replica and every client
+        loses sign-in (R1).
     - id: hand-over
       owner: "{consumer_owner_repo}"
       entry_point: "configure {consuming_service} with issuer {issuer}, client {client_id} and custody bao:platform/workloads/keycape/{client_id}, and make it require one of {access_groups} in the groups claim before sign-in completes"
diff --git a/sso-mfa/k8s/keycape/keycape-client.py b/sso-mfa/k8s/keycape/keycape-client.py
index 64a0dae..264f6d9 100644
--- a/sso-mfa/k8s/keycape/keycape-client.py
+++ b/sso-mfa/k8s/keycape/keycape-client.py
@@ -16,6 +16,9 @@ secrets-engine-openbao-client-rollout) and keeps their safeguards:
 - compare-and-swap on the Secret's uid and resourceVersion, then read-back
 - confidential clients: the KeyCape Deployment must already bind the client's
   secret env var (delivered from custody), or the next pod start fails closed
+- KeyCape's own startup checks (keycape check-config, key-cape c528daa) on the
+  live and the proposed registry, fed on stdin and never written to disk; apply
+  refuses a registry that would stop the single replica at its next start
 - no Secret value, parser message or Kubernetes error text leaves the process
 
 Modes: inspect (default), dry-run (server-side), apply. apply requires the
@@ -25,7 +28,7 @@ was accepted under an acknowledged type.
     keycape-client.py client-from-case <case.yaml>
     keycape-client.py inspect --client-file client.yaml [--operation remove]
     keycape-client.py apply --client-file client.yaml --case-acceptance <record> \\
-        --expected-uid <uid> --expected-resource-version <rv>
+        --check-config <keycape binary> --expected-uid <uid> --expected-resource-version <rv>
 """
 from __future__ import annotations
 
@@ -35,6 +38,7 @@ import copy
 import importlib.util
 import json
 import re
+import subprocess
 import sys
 from pathlib import Path
 
@@ -194,6 +198,25 @@ def deployment_bound(deployment, client):
     return bool(matches)
 
 
+def check_config(binary, config_text, env_names, policy_store):
+    """KeyCape's startup checks on one registry: names and messages only, no values."""
+    command = [binary, 'check-config', '--config', '/dev/stdin', '--env-names', ','.join(env_names)]
+    if policy_store:
+        command.append('--policy-store')
+    result = subprocess.run(command, input=config_text.encode(), capture_output=True, timeout=60)
+    report = json.loads(result.stdout)
+    require(isinstance(report, dict) and isinstance(report.get('valid'), bool)
+            and report['valid'] == (result.returncode == 0), 'check_config_output_shape')
+    return {'valid': report['valid'], 'clients': report.get('clients'),
+            'errors': [str(e) for e in report.get('errors') or []]}
+
+
+def deployment_env_names(deployment):
+    containers = deployment['spec']['template']['spec']['containers']
+    container = next(c for c in containers if c['name'] == 'keycape')
+    return sorted(e['name'] for e in container.get('env', []))
+
+
 def run(args, client):
     kubectl = lane.kubectl
     cluster = kubectl(['get', 'namespace', 'kube-system', '-o', 'json'])
@@ -202,19 +225,27 @@ def run(args, client):
     require(not before['metadata'].get('ownerReferences'), 'controller_owned_secret')
     metadata = pin.safe_metadata(before)
     encoded, changed = (replacement if args.operation == 'add' else removal)(before, client)
-    bound = None
-    if 'secretRef' in client:
+    bound = deployment = None
+    if 'secretRef' in client or args.check_config:
         deployment = kubectl(['-n', 'sso', 'get', 'deployment', 'keycape', '-o', 'json'])
         bound = deployment_bound(deployment, client)
+    checks = None
+    if args.check_config:
+        names = deployment_env_names(deployment)
+        policy_store = 'KEYCAPE_POLICY_PATH' in names
+        checks = {stage: check_config(args.check_config, base64.b64decode(config).decode(), names, policy_store)
+                  for stage, config in (('live', before['data']['config.yaml']), ('proposed', encoded))}
     receipt = {'schema': 'netkingdom.keycape-client.v1', 'target': 'sso/keycape-config',
                'before': metadata, 'operation': args.operation, 'client_id': client['clientId'],
                'client_type': client['clientType'], 'change_needed': changed, 'mode': args.mode,
-               'deployment_env_bound': bound, 'values_emitted': False, 'changed': False}
+               'deployment_env_bound': bound, 'check_config': checks, 'values_emitted': False, 'changed': False}
     if args.mode == 'inspect':
         return receipt
     if args.mode == 'apply':
         require(bool(args.case_acceptance), 'case_acceptance_record_required')
         receipt['case_acceptance'] = args.case_acceptance
+        require(checks is not None, 'keycape_check_config_required')
+        require(checks['proposed']['valid'], 'proposed_registry_fails_keycape_check_config')
         if args.operation == 'add' and bound is not None:
             require(bound, 'deployment_env_binding_required_first')
     require(metadata == {'uid': args.expected_uid, 'resource_version': args.expected_resource_version},
@@ -251,6 +282,7 @@ def main(argv=None):
     parser.add_argument('--expected-uid')
     parser.add_argument('--expected-resource-version')
     parser.add_argument('--case-acceptance', help='the case acceptance record; required for apply')
+    parser.add_argument('--check-config', help='a keycape binary with check-config (key-cape c528daa or later); required for apply')
     args = parser.parse_args(argv)
     try:
         if args.mode == 'client-from-case':
diff --git a/sso-mfa/k8s/keycape/test_keycape_client.py b/sso-mfa/k8s/keycape/test_keycape_client.py
index d20523d..b57eb23 100644
--- a/sso-mfa/k8s/keycape/test_keycape_client.py
+++ b/sso-mfa/k8s/keycape/test_keycape_client.py
@@ -156,17 +156,53 @@ class FakeKube:
 
 
 def args(mode, **kw):
-    base = dict(mode=mode, operation='add', expected_uid=UID, expected_resource_version='7', case_acceptance=None)
+    base = dict(mode=mode, operation='add', expected_uid=UID, expected_resource_version='7', case_acceptance=None,
+                check_config='keycape')
     base.update(kw)
     return argparse.Namespace(**base)
 
 
+class FakeCheck:
+    """Stands in for keycape check-config; refuses registries naming a client in `refuse`."""
+    def __init__(self, refuse=()):
+        self.refuse = refuse
+        self.calls = []
+
+    def __call__(self, binary, config_text, env_names, policy_store):
+        self.calls.append((binary, env_names, policy_store))
+        ids = [c['clientId'] for c in yaml.safe_load(config_text)['clients']]
+        errors = [f'client {i!r}: refused' for i in ids if i in self.refuse]
+        return {'valid': not errors, 'clients': len(ids), 'errors': errors}
+
+
 class RunTests(unittest.TestCase):
     def setUp(self):
-        self.original = kc.lane.kubectl
+        self.original = kc.lane.kubectl, kc.check_config
+        kc.check_config = FakeCheck()
 
     def tearDown(self):
-        kc.lane.kubectl = self.original
+        kc.lane.kubectl, kc.check_config = self.original
+
+    def test_apply_needs_keycape_check_config(self):
+        kc.lane.kubectl = FakeKube(fixture()[0])
+        with self.assertRaises(kc.Refused):
+            kc.run(args('apply', case_acceptance='decision:x', check_config=None), FORGEJO)
+
+    def test_apply_refuses_a_registry_keycape_would_refuse(self):
+        fake = FakeKube(fixture()[0])
+        kc.lane.kubectl = fake
+        kc.check_config = FakeCheck(refuse=('forgejo',))
+        with self.assertRaises(kc.Refused):
+            kc.run(args('apply', case_acceptance='decision:x'), FORGEJO)
+        self.assertEqual([], fake.patches)
+
+    def test_inspect_reports_live_and_proposed_checks_with_deployment_env(self):
+        kc.lane.kubectl = FakeKube(fixture()[0])
+        kc.check_config = FakeCheck(refuse=('forgejo',))
+        receipt = kc.run(args('inspect'), FORGEJO)
+        self.assertTrue(receipt['check_config']['live']['valid'])
+        self.assertFalse(receipt['check_config']['proposed']['valid'])
+        self.assertEqual([kc.env_name('forgejo')], kc.check_config.calls[0][1])
 
     def test_inspect_changes_nothing_and_emits_no_values(self):
         fake = FakeKube(fixture()[0])
diff --git a/workplans/NK-WP-0048-security-case-types.md b/workplans/NK-WP-0048-security-case-types.md
index bcaa487..be2f278 100644
--- a/workplans/NK-WP-0048-security-case-types.md
+++ b/workplans/NK-WP-0048-security-case-types.md
@@ -416,6 +416,20 @@ acknowledgment intake keeps `@1.0` as the record of what was acknowledged.
 ops-mason's build and ops-warden's case-ref digest predate this and need a
 re-render.
 
+2026-10-10: ops-mason re-rendered the Forgejo case from `@1.1` (message
+`22c6bba6`; plan digest `af1f4f81…`, no collisions) and rebuilt the bundle. The
+rendered OpenBao objects are identical to 1.0, so the already applied
+CCR-2026-0041 stands; 1.1 changes only consumer-side steps. key-cape shipped
+`keycape check-config` (c528daa, message `a7b0aeff`): KeyCape's startup checks
+without secret values, including the new duplicate-clientId rule.
+`keycape-client.py --check-config <binary>` now runs it on the live and the
+proposed registry, fed on stdin, and apply refuses a proposed registry that
+fails; register-client's entry point names the option (1.1 patch). The deployed
+image predates c528daa, so the binary is built from key-cape source for now.
+Before the next KeyCape rollout (Forgejo register-client or the CCR-2026-0018
+window), the attended operator runs `inspect --check-config` so the live
+registry is checked too.
+
 ```task
 id: NK-WP-0048-T07
 status: wait