Fix: Handle Incomplete and Malformed JSON in Subprocess Stream Parser

src/claude_code_sdk/_internal/transport/subprocess_cli.py

@@ -3,6 +3,7 @@
 import json
 import os
 import shutil
+import logging
 from collections.abc import AsyncIterator
 from pathlib import Path
 from subprocess import PIPE
@@ -17,6 +18,9 @@
 from ...types import ClaudeCodeOptions
 from . import Transport
 
+logger = logging.getLogger(__name__)
+
+MAX_BUFFER_SIZE = 1 * 1024 * 1024  # 1 MB
 
 class SubprocessCLITransport(Transport):
     """Subprocess transport using Claude Code CLI."""
@@ -169,6 +173,7 @@ async def receive_messages(self) -> AsyncIterator[dict[str, Any]]:
             raise CLIConnectionError("Not connected")
 
         stderr_lines = []
+        json_buffer = ""
 
         async def read_stderr() -> None:
             """Read stderr in background."""
@@ -188,12 +193,36 @@ async def read_stderr() -> None:
                     if not line_str:
                         continue
 
+                    json_buffer += line_str
+                    if len(json_buffer.encode("utf-8")) > MAX_BUFFER_SIZE:
+                        logger.warning("JSON buffer exceeded 1MB limit. Discarding buffered data: %s", json_buffer[:200])
+                        json_buffer = ""
+                        continue
+
                     try:
-                        data = json.loads(line_str)
+                        data = json.loads(json_buffer)
                         yield data
+                        json_buffer = ""
+
                     except json.JSONDecodeError as e:
-                        if line_str.startswith("{") or line_str.startswith("["):
-                            raise SDKJSONDecodeError(line_str, e) from e
+                    if json_buffer.startswith("{") or json_buffer.startswith("["):
+                        open_braces = json_buffer.count("{") - json_buffer.count("}")
+                        open_brackets = json_buffer.count("[") - json_buffer.count("]")
+
+                        if open_braces == 0 and open_brackets == 0:
+                            logger.warning("Malformed JSON detected: %s", json_buffer[:200])
+                            raise SDKJSONDecodeError(json_buffer, e) from e
+
+                        logger.debug(
+                            "Buffering incomplete JSON... (braces: %d, brackets: %d)",
+                            open_braces,
+                            open_brackets
+                        )
+                        json_buffer += "\n"
+                        continue
+                    else:
+                        logger.debug("Skipping non-JSON line: %s", json_buffer[:200])
+                        json_buffer = ""
                         continue
 
             except anyio.ClosedResourceError: