diff --git a/schema-validator/src/main/java/com/networknt/aws/lambda/validator/SchemaValidator.java b/schema-validator/src/main/java/com/networknt/aws/lambda/validator/SchemaValidator.java
index 52ed649..36791a0 100644
--- a/schema-validator/src/main/java/com/networknt/aws/lambda/validator/SchemaValidator.java
+++ b/schema-validator/src/main/java/com/networknt/aws/lambda/validator/SchemaValidator.java
@@ -70,12 +70,15 @@ public SchemaValidator() {
 
     /**
      * Build a new validator for the given API specification.
+     * Components are snapshotted at construction. Later changes to the API overlay are not observed;
+     * construct a new validator after changing the specification.
      *
      * @param api The API to build the validator for. If provided, is used to retrieve schemas in components
      *            for use in references.
      */
     public SchemaValidator(final OpenApi3 api) {
-        this.jsonNode = api == null ? null : Overlay.toJson((OpenApi3Impl)api).get(COMPONENTS_FIELD);
+        JsonNode components = api == null ? null : Overlay.toJson((OpenApi3Impl)api).get(COMPONENTS_FIELD);
+        this.jsonNode = components == null ? null : components.deepCopy();
         this.pathType = PathType.JSON_POINTER;
     }
 
@@ -114,10 +117,11 @@ private Status doValidate(final JsonNode value, final JsonNode schema, boolean t
 
         List<Error> processingReport = null;
         try {
+            JsonNode validationSchema = schema.deepCopy();
             if(jsonNode != null) {
-                ((ObjectNode)schema).set(COMPONENTS_FIELD, jsonNode);
+                ((ObjectNode)validationSchema).set(COMPONENTS_FIELD, jsonNode.deepCopy());
             }
-            Schema jsonSchema = getRegistry(typeLoose, nullableKeywordEnabled, validationPathType).getSchema(schema);
+            Schema jsonSchema = getRegistry(typeLoose, nullableKeywordEnabled, validationPathType).getSchema(validationSchema);
             processingReport = jsonSchema.validate(value);
         } catch (Exception e) {
             LOG.error("Unable to validate the value against the OpenAPI schema", e);
diff --git a/schema-validator/src/test/java/com/networknt/aws/lambda/validator/SchemaIsolationTest.java b/schema-validator/src/test/java/com/networknt/aws/lambda/validator/SchemaIsolationTest.java
new file mode 100644
index 0000000..9906723
--- /dev/null
+++ b/schema-validator/src/test/java/com/networknt/aws/lambda/validator/SchemaIsolationTest.java
@@ -0,0 +1,87 @@
+package com.networknt.aws.lambda.validator;
+
+import com.networknt.jackson.JacksonDefaults;
+import com.networknt.oas.OpenApiParser;
+import com.networknt.oas.model.OpenApi3;
+import org.junit.jupiter.api.Test;
+import tools.jackson.databind.JsonNode;
+
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.concurrent.Callable;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class SchemaIsolationTest {
+    private static OpenApi3 api(String type) throws Exception {
+        // Resolution base for the inline document; the parser does not read this file.
+        var documentUrl = Path.of("schema-isolation.json").toUri().toURL();
+        return (OpenApi3) new OpenApiParser().parse("""
+                {"openapi":"3.0.3","info":{"title":"isolation","version":"1"},
+                 "paths":{},"components":{"schemas":{"Value":{"type":"%s"}}}}
+                """.formatted(type), documentUrl, false);
+    }
+
+    private static JsonNode reference() {
+        return JacksonDefaults.mapper().readTree("{\"$ref\":\"#/components/schemas/Value\"}");
+    }
+
+    @Test
+    void validationNeverAddsComponentsToTheCallerSchema() throws Exception {
+        var validator = new SchemaValidator(api("integer"));
+        var schema = reference();
+        var original = schema.deepCopy();
+        assertNull(validator.validate(JacksonDefaults.mapper().readTree("7"), schema, false, false));
+        assertNotNull(validator.validate(JacksonDefaults.mapper().readTree("\"invalid\""), schema, false, false));
+        assertEquals(original, schema);
+        assertFalse(schema.has("components"));
+    }
+
+    @Test
+    void callerOwnedComponentsRemainUnchanged() throws Exception {
+        var schema = JacksonDefaults.mapper().readTree("""
+                {"$ref":"#/components/schemas/Value",
+                 "components":{"schemas":{"Value":{"type":"string"}}}}
+                """);
+        var original = schema.deepCopy();
+        var validator = new SchemaValidator(api("integer"));
+        // API components still take precedence for this validation, as before.
+        assertNull(validator.validate(JacksonDefaults.mapper().readTree("7"), schema, false, false));
+        assertEquals(original, schema);
+    }
+
+    @Test
+    void concurrentValidationKeepsCallerInputsIsolated() throws Exception {
+        var integerValidator = new SchemaValidator(api("integer"));
+        var stringValidator = new SchemaValidator(api("string"));
+        var schema = reference();
+        var original = schema.deepCopy();
+        var number = JacksonDefaults.mapper().readTree("7");
+        var text = JacksonDefaults.mapper().readTree("\"7\"");
+        var tasks = new ArrayList<Callable<Void>>();
+        for (int i = 0; i < 40; i++) {
+            tasks.add(() -> {
+                assertNull(integerValidator.validate(number, schema, false, false));
+                assertNotNull(stringValidator.validate(number, schema, false, false));
+                assertNull(stringValidator.validate(text, schema, false, false));
+                assertNotNull(integerValidator.validate(text, schema, false, false));
+                assertNull(integerValidator.validate(text, schema, true, false));
+                return null;
+            });
+        }
+        var executor = Executors.newFixedThreadPool(4);
+        try {
+            for (var future : executor.invokeAll(tasks, 10, TimeUnit.SECONDS)) future.get(1, TimeUnit.SECONDS);
+        } finally {
+            executor.shutdownNow();
+            assertTrue(executor.awaitTermination(1, TimeUnit.SECONDS));
+        }
+        assertEquals(original, schema);
+    }
+}