fix(split): serialize split_class as a JSON string in multipart form data

src/landingai_ade/_client.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import os
+import json
 import importlib.metadata
 from typing import TYPE_CHECKING, Any, Dict, Union, Mapping, Iterable, Optional, cast
 from pathlib import Path
@@ -796,7 +797,7 @@ def section(
     def split(
         self,
         *,
-        split_class: Iterable[client_split_params.SplitClass],
+        split_class: Union[str, Iterable[client_split_params.SplitClass]],
         markdown: Union[FileTypes, str, None] | Omit = omit,
         markdown_url: Optional[str] | Omit = omit,
         model: Optional[str] | Omit = omit,
@@ -846,7 +847,9 @@ def split(
         original_markdown_url = markdown_url
         body = deepcopy_with_paths(
             {
-                "split_class": split_class,
+                # The API expects split_class as a single JSON string form field,
+                # not flattened multipart fields (https://github.com/landing-ai/ade-python/issues/76).
+                "split_class": split_class if isinstance(split_class, str) else json.dumps(list(split_class)),
                 "markdown": markdown,
                 "markdown_url": markdown_url,
                 "model": model,
@@ -1513,7 +1516,7 @@ async def section(
     async def split(
         self,
         *,
-        split_class: Iterable[client_split_params.SplitClass],
+        split_class: Union[str, Iterable[client_split_params.SplitClass]],
         markdown: Union[FileTypes, str, None] | Omit = omit,
         markdown_url: Optional[str] | Omit = omit,
         model: Optional[str] | Omit = omit,
@@ -1563,7 +1566,9 @@ async def split(
         original_markdown_url = markdown_url
         body = deepcopy_with_paths(
             {
-                "split_class": split_class,
+                # The API expects split_class as a single JSON string form field,
+                # not flattened multipart fields (https://github.com/landing-ai/ade-python/issues/76).
+                "split_class": split_class if isinstance(split_class, str) else json.dumps(list(split_class)),
                 "markdown": markdown,
                 "markdown_url": markdown_url,
                 "model": model,

src/landingai_ade/types/client_split_params.py

@@ -9,7 +9,7 @@
 
 
 class ClientSplitParams(TypedDict, total=False):
-    split_class: Required[Iterable[SplitClass]]
+    split_class: Required[Union[str, Iterable[SplitClass]]]
     """List of split classification options/configuration.
 
     Can be provided as JSON string in form data.

tests/test_split_params.py

@@ -0,0 +1,57 @@
+# Regression tests for https://github.com/landing-ai/ade-python/issues/76:
+# split_class must be sent as a single JSON string form field, not flattened
+# into split_class[0][name]-style multipart fields.
+from __future__ import annotations
+
+import json
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+from landingai_ade import LandingAIADE, AsyncLandingAIADE
+
+SPLIT_CLASS = [
+    {"name": "Bank Statement", "description": "Bank account activity summary."},
+    {"name": "Pay Stub", "description": "Employee earnings detail.", "identifier": "Pay Stub Date"},
+]
+
+
+def test_sync_split_class_sent_as_json_string() -> None:
+    with LandingAIADE(apikey="test-key", base_url="http://localhost") as client:
+        with patch.object(client, "post", return_value=MagicMock()) as post:
+            client.split(split_class=SPLIT_CLASS, markdown="some markdown")
+
+    body = post.call_args.kwargs["body"]
+    assert body["split_class"] == json.dumps(SPLIT_CLASS)
+    assert json.loads(body["split_class"]) == SPLIT_CLASS
+
+
+def test_sync_split_class_json_string_passed_through() -> None:
+    # An already JSON-encoded split_class (documented in the README) must not be re-serialized.
+    encoded = json.dumps(SPLIT_CLASS)
+    with LandingAIADE(apikey="test-key", base_url="http://localhost") as client:
+        with patch.object(client, "post", return_value=MagicMock()) as post:
+            client.split(split_class=encoded, markdown="some markdown")
+
+    assert post.call_args.kwargs["body"]["split_class"] == encoded
+
+
+@pytest.mark.asyncio
+async def test_async_split_class_json_string_passed_through() -> None:
+    encoded = json.dumps(SPLIT_CLASS)
+    async with AsyncLandingAIADE(apikey="test-key", base_url="http://localhost") as client:
+        with patch.object(client, "post", new_callable=AsyncMock, return_value=MagicMock()) as post:
+            await client.split(split_class=encoded, markdown="some markdown")
+
+    assert post.call_args.kwargs["body"]["split_class"] == encoded
+
+
+@pytest.mark.asyncio
+async def test_async_split_class_sent_as_json_string() -> None:
+    async with AsyncLandingAIADE(apikey="test-key", base_url="http://localhost") as client:
+        with patch.object(client, "post", new_callable=AsyncMock, return_value=MagicMock()) as post:
+            await client.split(split_class=SPLIT_CLASS, markdown="some markdown")
+
+    body = post.call_args.kwargs["body"]
+    assert body["split_class"] == json.dumps(SPLIT_CLASS)
+    assert json.loads(body["split_class"]) == SPLIT_CLASS