diff --git a/packages/core/src/tracing/google-genai/index.ts b/packages/core/src/tracing/google-genai/index.ts
index 68e4d414586a..9390a82e0e14 100644
--- a/packages/core/src/tracing/google-genai/index.ts
+++ b/packages/core/src/tracing/google-genai/index.ts
@@ -360,9 +360,16 @@ function instrumentMethod<T extends unknown[], R>(
  * Recursively instruments methods and handles special cases like chats.create
  */
 function createDeepProxy<T extends object>(target: T, currentPath = '', options: GoogleGenAIOptions): T {
+  const propertyCache = new Map<PropertyKey, { original: unknown; wrapped: unknown }>();
+
   return new Proxy(target, {
     get: (t, prop, receiver) => {
       const value = Reflect.get(t, prop, receiver);
+      const cachedEntry = propertyCache.get(prop);
+      if (cachedEntry && cachedEntry.original === value) {
+        return cachedEntry.wrapped;
+      }
+
       const methodPath = buildMethodPath(currentPath, String(prop));
 
       const instrumentedMethod: InstrumentedMethodEntry | undefined =
@@ -374,6 +381,7 @@ function createDeepProxy<T extends object>(target: T, currentPath = '', options:
           : value.bind(t);
 
         if (!instrumentedMethod.proxyResultPath) {
+          propertyCache.set(prop, { original: value, wrapped: wrappedMethod });
           return wrappedMethod;
         }
 
@@ -381,22 +389,28 @@ function createDeepProxy<T extends object>(target: T, currentPath = '', options:
         // Note: This currently only properly handles synchronous methods. For async methods,
         // the Promise itself would be proxied instead of the resolved value. Currently we
         // don't have a case where this is needed, so I'll keep it simple for now.
-        return function (...args: unknown[]): unknown {
+        const methodWithProxiedResult = function (...args: unknown[]): unknown {
           const result = wrappedMethod(...args);
           if (result && typeof result === 'object') {
             return createDeepProxy(result as object, instrumentedMethod.proxyResultPath, options);
           }
           return result;
         };
+        propertyCache.set(prop, { original: value, wrapped: methodWithProxiedResult });
+        return methodWithProxiedResult;
       }
 
       if (typeof value === 'function') {
         // Bind non-instrumented functions to preserve the original `this` context
-        return value.bind(t);
+        const boundMethod = value.bind(t);
+        propertyCache.set(prop, { original: value, wrapped: boundMethod });
+        return boundMethod;
       }
 
       if (value && typeof value === 'object') {
-        return createDeepProxy(value, methodPath, options);
+        const nestedProxy = createDeepProxy(value, methodPath, options);
+        propertyCache.set(prop, { original: value, wrapped: nestedProxy });
+        return nestedProxy;
       }
 
       return value;
diff --git a/packages/core/src/tracing/openai/index.ts b/packages/core/src/tracing/openai/index.ts
index 821e9c68e0ff..f5335253f14a 100644
--- a/packages/core/src/tracing/openai/index.ts
+++ b/packages/core/src/tracing/openai/index.ts
@@ -238,30 +238,43 @@ function instrumentMethod<T extends unknown[], R>(
  * Create a deep proxy for OpenAI client instrumentation
  */
 function createDeepProxy<T extends object>(target: T, currentPath = '', options: OpenAiOptions): T {
+  const propertyCache = new Map<PropertyKey, { original: unknown; wrapped: unknown }>();
+
   return new Proxy(target, {
-    get(obj: object, prop: string): unknown {
-      const value = (obj as Record<string, unknown>)[prop];
+    get(obj: object, prop: string | symbol): unknown {
+      const value = Reflect.get(obj, prop) as unknown;
+      const cachedEntry = propertyCache.get(prop);
+      if (cachedEntry && cachedEntry.original === value) {
+        return cachedEntry.wrapped;
+      }
+
       const methodPath = buildMethodPath(currentPath, String(prop));
 
       const instrumentedMethod = OPENAI_METHOD_REGISTRY[methodPath as keyof typeof OPENAI_METHOD_REGISTRY];
       if (typeof value === 'function' && instrumentedMethod) {
-        return instrumentMethod(
+        const wrappedMethod = instrumentMethod(
           value as (...args: unknown[]) => Promise<unknown>,
           methodPath,
           instrumentedMethod,
           obj,
           options,
         );
+        propertyCache.set(prop, { original: value, wrapped: wrappedMethod });
+        return wrappedMethod;
       }
 
       if (typeof value === 'function') {
         // Bind non-instrumented functions to preserve the original `this` context,
         // which is required for accessing private class fields (e.g. #baseURL) in OpenAI SDK v5.
-        return value.bind(obj);
+        const boundMethod = value.bind(obj);
+        propertyCache.set(prop, { original: value, wrapped: boundMethod });
+        return boundMethod;
       }
 
       if (value && typeof value === 'object') {
-        return createDeepProxy(value, methodPath, options);
+        const nestedProxy = createDeepProxy(value, methodPath, options);
+        propertyCache.set(prop, { original: value, wrapped: nestedProxy });
+        return nestedProxy;
       }
 
       return value;
diff --git a/packages/core/test/tracing/ai-integration-proxy.test.ts b/packages/core/test/tracing/ai-integration-proxy.test.ts
new file mode 100644
index 000000000000..5d36884aa757
--- /dev/null
+++ b/packages/core/test/tracing/ai-integration-proxy.test.ts
@@ -0,0 +1,37 @@
+import { describe, expect, it } from 'vitest';
+import { instrumentGoogleGenAIClient } from '../../src/tracing/google-genai';
+import { instrumentOpenAiClient } from '../../src/tracing/openai';
+
+describe('AI integration deep proxies', () => {
+  it('returns stable references for OpenAI client properties', () => {
+    const client = {
+      chat: { completions: { create: () => Promise.resolve({}) } },
+      getBaseURL: () => 'https://api.openai.com',
+    };
+
+    const instrumentedClient = instrumentOpenAiClient(client);
+    const completions = instrumentedClient.chat.completions;
+    const create = completions.create;
+    const getBaseURL = instrumentedClient.getBaseURL;
+
+    expect(instrumentedClient.chat.completions).toBe(completions);
+    expect(instrumentedClient.chat.completions.create).toBe(create);
+    expect(instrumentedClient.getBaseURL).toBe(getBaseURL);
+  });
+
+  it('returns stable references for Google GenAI client properties', () => {
+    const client = {
+      chats: { create: () => ({ sendMessage: () => Promise.resolve({}) }) },
+      getVersion: () => '1.0.0',
+    };
+
+    const instrumentedClient = instrumentGoogleGenAIClient(client);
+    const chats = instrumentedClient.chats;
+    const create = chats.create;
+    const getVersion = instrumentedClient.getVersion;
+
+    expect(instrumentedClient.chats).toBe(chats);
+    expect(instrumentedClient.chats.create).toBe(create);
+    expect(instrumentedClient.getVersion).toBe(getVersion);
+  });
+});