diff --git a/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcSourceRegistry.java b/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcSourceRegistry.java
index fd00e11a..1a4e2ceb 100644
--- a/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcSourceRegistry.java
+++ b/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcSourceRegistry.java
@@ -1,23 +1,36 @@
 package com.xtrmetl.cdc.spi;
 
 import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 
 import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 
 /**
  * Registry of CDC source connector types discovered as Spring beans, plus a safe
  * fallback for unit tests without a Spring context.
+ *
+ * <p>Connector identifiers are configuration authority. Registration therefore fails closed for
+ * null connectors, blank identifiers, and duplicate identifiers instead of allowing bean order to
+ * replace the selected implementation.</p>
  */
 @Component
 public class CdcSourceRegistry {
 
     private final Map<String, CdcSourceConnector> byId = new LinkedHashMap<>();
 
+    /**
+     * Creates a registry from Spring-discovered source connectors.
+     *
+     * @param connectors ordered provider of source connector beans
+     * @throws IllegalArgumentException when a discovered connector has an invalid or duplicate id
+     */
+    @Autowired
     public CdcSourceRegistry(ObjectProvider<CdcSourceConnector> connectors) {
         connectors.orderedStream().forEach(this::register);
         if (byId.isEmpty()) {
@@ -27,7 +40,10 @@ public CdcSourceRegistry(ObjectProvider<CdcSourceConnector> connectors) {
     }
 
     /**
-     * Explicit list for tests.
+     * Creates a registry from an explicit connector list, primarily for standalone use and tests.
+     *
+     * @param connectors source connectors to register; a null list means no explicit connectors
+     * @throws IllegalArgumentException when a connector has an invalid or duplicate id
      */
     public CdcSourceRegistry(List<CdcSourceConnector> connectors) {
         if (connectors != null) {
@@ -38,19 +54,50 @@ public CdcSourceRegistry(List<CdcSourceConnector> connectors) {
         }
     }
 
+    /**
+     * Creates a registry containing the built-in PostgreSQL Debezium source connector.
+     */
     public CdcSourceRegistry() {
         this(List.of());
     }
 
+    /**
+     * Registers one source connector without allowing existing configuration identity to be replaced.
+     *
+     * @param connector source connector to register
+     * @throws IllegalArgumentException when the connector is null, its id is blank, or its id is
+     *     already registered
+     */
     public final void register(CdcSourceConnector connector) {
-        byId.put(connector.id(), connector);
+        if (connector == null) {
+            throw new IllegalArgumentException("CDC source connector must not be null");
+        }
+        String id = Objects.requireNonNullElse(connector.id(), "");
+        if (id.isBlank()) {
+            throw new IllegalArgumentException("CDC source connector id must not be blank");
+        }
+        CdcSourceConnector previous = byId.putIfAbsent(id, connector);
+        if (previous != null) {
+            throw new IllegalArgumentException("Duplicate CDC source connector id: " + id);
+        }
     }
 
+    /**
+     * Finds a source connector by its exact configuration identifier.
+     *
+     * @param id exact connector identifier
+     * @return the registered connector, or empty when the identifier is unknown
+     */
     public Optional<CdcSourceConnector> find(String id) {
         return Optional.ofNullable(byId.get(id));
     }
 
+    /**
+     * Returns an immutable insertion-ordered snapshot of registered source connectors.
+     *
+     * @return immutable connector collection detached from registry mutation authority
+     */
     public Collection<CdcSourceConnector> all() {
-        return byId.values();
+        return List.copyOf(byId.values());
     }
 }
diff --git a/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcTargetRegistry.java b/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcTargetRegistry.java
index 5d42b186..746c00db 100644
--- a/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcTargetRegistry.java
+++ b/cdc-service/src/main/java/com/xtrmetl/cdc/spi/CdcTargetRegistry.java
@@ -4,31 +4,64 @@
 
 import java.util.Collection;
 import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 
 /**
- * Registry of CDC target types (Kafka, JDBC replica, future warehouses).
+ * Registry of CDC target connector types such as Kafka and JDBC replica targets.
+ *
+ * <p>Connector identifiers are configuration authority. Invalid registration is rejected so
+ * registration order cannot silently replace a selected connector implementation.</p>
  */
 @Component
 public class CdcTargetRegistry {
 
     private final Map<String, CdcTargetConnector> byId = new LinkedHashMap<>();
 
+    /** Creates a registry containing the built-in Kafka and JDBC replica target connectors. */
     public CdcTargetRegistry() {
         register(new KafkaCdcTargetConnector());
         register(new JdbcReplicaCdcTargetConnector());
     }
 
+    /**
+     * Registers one target connector without replacing an existing connector with the same id.
+     *
+     * @param connector target connector to register
+     * @throws IllegalArgumentException when the connector is null, its id is blank, or its id is already registered
+     */
     public final void register(CdcTargetConnector connector) {
-        byId.put(connector.id(), connector);
+        if (connector == null) {
+            throw new IllegalArgumentException("CDC target connector must not be null");
+        }
+        String id = Objects.requireNonNullElse(connector.id(), "");
+        if (id.isBlank()) {
+            throw new IllegalArgumentException("CDC target connector id must not be blank");
+        }
+        CdcTargetConnector previous = byId.putIfAbsent(id, connector);
+        if (previous != null) {
+            throw new IllegalArgumentException("Duplicate CDC target connector id: " + id);
+        }
     }
 
+    /**
+     * Finds a target connector by its exact configuration identifier.
+     *
+     * @param id exact connector identifier
+     * @return the registered connector, or empty when the identifier is unknown
+     */
     public Optional<CdcTargetConnector> find(String id) {
         return Optional.ofNullable(byId.get(id));
     }
 
+    /**
+     * Returns an immutable insertion-ordered snapshot of registered target connectors.
+     *
+     * @return immutable connector collection detached from registry mutation authority
+     */
     public Collection<CdcTargetConnector> all() {
-        return byId.values();
+        return List.copyOf(byId.values());
     }
 }
diff --git a/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcRegistryIdentityTest.java b/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcRegistryIdentityTest.java
new file mode 100644
index 00000000..70c89562
--- /dev/null
+++ b/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcRegistryIdentityTest.java
@@ -0,0 +1,128 @@
+package com.xtrmetl.cdc.spi;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.ObjectProvider;
+import org.springframework.beans.factory.annotation.Autowired;
+
+import java.lang.reflect.Constructor;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Fail-first contract for CDC connector registration authority.
+ *
+ * <p>Connector identifiers select production implementations. Invalid registration must fail before
+ * registry mutation so bean order or plugin code cannot silently replace or remove that authority.</p>
+ */
+class CdcRegistryIdentityTest {
+
+    @Test
+    void duplicateSourceConnectorIdsFailClosedInsteadOfReplacingRegistration() {
+        CdcSourceConnector first = source("duplicate-source");
+        CdcSourceConnector second = source("duplicate-source");
+        CdcSourceRegistry registry = new CdcSourceRegistry(List.of(first));
+
+        IllegalArgumentException failure = assertThrows(
+                IllegalArgumentException.class,
+                () -> registry.register(second)
+        );
+
+        assertEquals("Duplicate CDC source connector id: duplicate-source", failure.getMessage());
+        assertSame(first, registry.find("duplicate-source").orElseThrow());
+    }
+
+    @Test
+    void duplicateTargetConnectorIdsFailClosedInsteadOfReplacingRegistration() {
+        CdcTargetRegistry registry = new CdcTargetRegistry();
+        CdcTargetConnector originalKafka = registry.find(KafkaCdcTargetConnector.ID).orElseThrow();
+        CdcTargetConnector duplicateKafka = target(KafkaCdcTargetConnector.ID);
+
+        IllegalArgumentException failure = assertThrows(
+                IllegalArgumentException.class,
+                () -> registry.register(duplicateKafka)
+        );
+
+        assertEquals("Duplicate CDC target connector id: kafka", failure.getMessage());
+        assertSame(originalKafka, registry.find(KafkaCdcTargetConnector.ID).orElseThrow());
+    }
+
+    @Test
+    void springDiscoveryConstructorIsExplicitlyAutowired() {
+        Constructor<?> discoveryConstructor = Arrays.stream(CdcSourceRegistry.class.getConstructors())
+                .filter(constructor -> Arrays.equals(
+                        constructor.getParameterTypes(),
+                        new Class<?>[]{ObjectProvider.class}
+                ))
+                .findFirst()
+                .orElseThrow();
+
+        assertTrue(discoveryConstructor.isAnnotationPresent(Autowired.class),
+                "Spring discovery constructor must be explicitly selected when other public constructors exist");
+    }
+
+    @Test
+    void nullSourceConnectorFailsBeforeRegistryMutation() {
+        CdcSourceRegistry registry = new CdcSourceRegistry();
+        IllegalArgumentException failure = assertThrows(IllegalArgumentException.class, () -> registry.register(null));
+        assertEquals("CDC source connector must not be null", failure.getMessage());
+    }
+
+    @Test
+    void nullTargetConnectorFailsBeforeRegistryMutation() {
+        CdcTargetRegistry registry = new CdcTargetRegistry();
+        IllegalArgumentException failure = assertThrows(IllegalArgumentException.class, () -> registry.register(null));
+        assertEquals("CDC target connector must not be null", failure.getMessage());
+    }
+
+    @Test
+    void blankSourceConnectorIdFailsBeforeRegistryMutation() {
+        CdcSourceConnector blank = source("   ");
+        IllegalArgumentException failure = assertThrows(
+                IllegalArgumentException.class,
+                () -> new CdcSourceRegistry(List.of(blank))
+        );
+        assertEquals("CDC source connector id must not be blank", failure.getMessage());
+    }
+
+    @Test
+    void blankTargetConnectorIdFailsBeforeRegistryMutation() {
+        CdcTargetRegistry registry = new CdcTargetRegistry();
+        CdcTargetConnector blank = target("");
+        IllegalArgumentException failure = assertThrows(IllegalArgumentException.class, () -> registry.register(blank));
+        assertEquals("CDC target connector id must not be blank", failure.getMessage());
+    }
+
+    @Test
+    void sourceConnectorCollectionCannotDeleteRegistrationAuthority() {
+        CdcSourceRegistry registry = new CdcSourceRegistry(List.of(source("immutable-source")));
+        assertThrows(UnsupportedOperationException.class, () -> registry.all().clear());
+        assertTrue(registry.find("immutable-source").isPresent());
+    }
+
+    @Test
+    void targetConnectorCollectionCannotDeleteRegistrationAuthority() {
+        CdcTargetRegistry registry = new CdcTargetRegistry();
+        assertThrows(UnsupportedOperationException.class, () -> registry.all().clear());
+        assertTrue(registry.find(KafkaCdcTargetConnector.ID).isPresent());
+        assertTrue(registry.find(JdbcReplicaCdcTargetConnector.ID).isPresent());
+    }
+
+    private static CdcSourceConnector source(String id) {
+        CdcSourceConnector connector = mock(CdcSourceConnector.class);
+        when(connector.id()).thenReturn(id);
+        return connector;
+    }
+
+    private static CdcTargetConnector target(String id) {
+        CdcTargetConnector connector = mock(CdcTargetConnector.class);
+        when(connector.id()).thenReturn(id);
+        return connector;
+    }
+}
diff --git a/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcSourceRegistrySpringWiringTest.java b/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcSourceRegistrySpringWiringTest.java
new file mode 100644
index 00000000..cb0e4f7d
--- /dev/null
+++ b/cdc-service/src/test/java/com/xtrmetl/cdc/spi/CdcSourceRegistrySpringWiringTest.java
@@ -0,0 +1,71 @@
+package com.xtrmetl.cdc.spi;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import java.util.Map;
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+/**
+ * Verifies that the Spring-managed source registry receives discovered connector beans.
+ *
+ * <p>This test reaches the actual Spring constructor-selection boundary instead of directly
+ * instantiating {@link CdcSourceRegistry}. It prevents a public no-argument constructor from
+ * silently bypassing the {@code ObjectProvider<CdcSourceConnector>} integration path.</p>
+ */
+class CdcSourceRegistrySpringWiringTest {
+
+    @Test
+    void springContextRegistersDiscoveredSourceConnectorBean() {
+        TestSourceConnector connector = new TestSourceConnector();
+
+        try (AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext()) {
+            context.registerBean(CdcSourceConnector.class, () -> connector);
+            context.register(CdcSourceRegistry.class);
+            context.refresh();
+
+            CdcSourceRegistry registry = context.getBean(CdcSourceRegistry.class);
+
+            assertSame(
+                    connector,
+                    registry.find(connector.id()).orElseThrow(),
+                    "Spring must construct the registry through its connector-provider constructor"
+            );
+        }
+    }
+
+    private static final class TestSourceConnector implements CdcSourceConnector {
+
+        @Override
+        public String id() {
+            return "test_source";
+        }
+
+        @Override
+        public String displayName() {
+            return "Test source";
+        }
+
+        @Override
+        public SourceCapabilities capabilities() {
+            return new SourceCapabilities("test", Set.of("test_database"), false);
+        }
+
+        @Override
+        public void validate(Map<String, String> config) {
+            // No configuration is required for this constructor-selection regression fixture.
+        }
+
+        @Override
+        public void start(Map<String, String> config) {
+            // No runtime capture is required for this constructor-selection regression fixture.
+        }
+
+        @Override
+        public void stop() {
+            // No runtime capture is started by this constructor-selection regression fixture.
+        }
+    }
+}