diff --git a/openespi-authserver/src/main/resources/application-prod.yml b/openespi-authserver/src/main/resources/application-prod.yml
index e54e3af7..44c474f7 100644
--- a/openespi-authserver/src/main/resources/application-prod.yml
+++ b/openespi-authserver/src/main/resources/application-prod.yml
@@ -93,6 +93,10 @@ spring:
     schemas: oauth2_authserver
     validate-on-migrate: true
     clean-disabled: true
+    # Skip V3+ pending ESPI 4.0 XSD-aligned schema repair (see issue #123).
+    # V1+V2 provide enough for OAuth2 grant + introspection; V3 onwards is
+    # seed/demo data that references columns missing from MySQL V1.
+    target: "2.0.0"
 
 # Logging Configuration - Production Levels
 logging:
diff --git a/openespi-authserver/src/main/resources/db/vendor/h2/V1_0_0__create_oauth2_schema.sql b/openespi-authserver/src/main/resources/db/vendor/h2/V1_0_0__create_oauth2_schema.sql
index bf0a1cc1..93dcdabc 100644
--- a/openespi-authserver/src/main/resources/db/vendor/h2/V1_0_0__create_oauth2_schema.sql
+++ b/openespi-authserver/src/main/resources/db/vendor/h2/V1_0_0__create_oauth2_schema.sql
@@ -64,7 +64,8 @@ CREATE TABLE oauth2_registered_client (
     scopes varchar(1000) NOT NULL,
     client_settings varchar(2000) NOT NULL,
     token_settings varchar(2000) NOT NULL,
-    PRIMARY KEY (id)
+    PRIMARY KEY (id),
+    CONSTRAINT uk_oauth2_registered_client_client_id UNIQUE (client_id)
 );
 
 -- ESPI Application Information mapping
@@ -105,7 +106,6 @@ CREATE TABLE espi_application_info (
 
 -- Create indexes for performance
 CREATE INDEX idx_oauth2_authorization_client_principal ON oauth2_authorization (registered_client_id, principal_name);
-CREATE INDEX idx_oauth2_registered_client_id ON oauth2_registered_client (client_id);
 CREATE INDEX idx_espi_application_client_id ON espi_application_info (client_id);
 
 -- Insert sample data for local development