diff --git a/scripts/verify_test_fidelity.py b/scripts/verify_test_fidelity.py
index 63f8acc6..e559019f 100644
--- a/scripts/verify_test_fidelity.py
+++ b/scripts/verify_test_fidelity.py
@@ -45,7 +45,7 @@
     "packages/chat/src/markdown.test.ts": "tests/test_markdown_faithful.py",
     "packages/chat/src/streaming-markdown.test.ts": "tests/test_streaming_markdown.py",
     "packages/chat/src/serialization.test.ts": "tests/test_serialization.py",
-    "packages/chat/src/ai.test.ts": "tests/test_ai.py",
+    "packages/chat/src/ai.test.ts": "tests/test_ai_messages.py",
     "packages/chat/src/from-full-stream.test.ts": "tests/test_from_full_stream.py",
 }
 
diff --git a/src/chat_sdk/ai/__init__.py b/src/chat_sdk/ai/__init__.py
new file mode 100644
index 00000000..d5a874dc
--- /dev/null
+++ b/src/chat_sdk/ai/__init__.py
@@ -0,0 +1,37 @@
+"""AI SDK integration for the chat SDK.
+
+Python port of the ``chat/ai`` subpath. Mirrors the upstream structure where
+``ai.ts`` was split into ``ai/messages.ts`` (and, in later PRs, ``ai/tools.ts``)
+to make room for tool factories.
+
+Re-exports everything the former ``chat_sdk.ai`` module exposed so existing
+imports such as ``from chat_sdk.ai import to_ai_messages`` keep working.
+"""
+
+from __future__ import annotations
+
+from chat_sdk.ai.messages import (
+    TEXT_MIME_PREFIXES,
+    AiAssistantMessage,
+    AiFilePart,
+    AiImagePart,
+    AiMessage,
+    AiMessagePart,
+    AiTextPart,
+    AiUserMessage,
+    ToAiMessagesOptions,
+    to_ai_messages,
+)
+
+__all__ = [
+    "TEXT_MIME_PREFIXES",
+    "AiAssistantMessage",
+    "AiFilePart",
+    "AiImagePart",
+    "AiMessage",
+    "AiMessagePart",
+    "AiTextPart",
+    "AiUserMessage",
+    "ToAiMessagesOptions",
+    "to_ai_messages",
+]
diff --git a/src/chat_sdk/ai.py b/src/chat_sdk/ai/messages.py
similarity index 99%
rename from src/chat_sdk/ai.py
rename to src/chat_sdk/ai/messages.py
index 1fc2d500..13b27fc8 100644
--- a/src/chat_sdk/ai.py
+++ b/src/chat_sdk/ai/messages.py
@@ -1,6 +1,6 @@
 """Convert chat Messages to AI SDK format.
 
-Python port of ai.ts.
+Python port of ``ai/messages.ts``.
 """
 
 from __future__ import annotations
diff --git a/tests/test_ai.py b/tests/test_ai_messages.py
similarity index 100%
rename from tests/test_ai.py
rename to tests/test_ai_messages.py