diff --git a/src/claude_agent_sdk/_internal/message_parser.py b/src/claude_agent_sdk/_internal/message_parser.py
index f91081c3..e1defa66 100644
--- a/src/claude_agent_sdk/_internal/message_parser.py
+++ b/src/claude_agent_sdk/_internal/message_parser.py
@@ -157,6 +157,7 @@ def parse_message(data: dict[str, Any]) -> Message:
                     usage=data.get("usage"),
                     result=data.get("result"),
                     structured_output=data.get("structured_output"),
+                    errors=data.get("errors"),
                 )
             except KeyError as e:
                 raise MessageParseError(
diff --git a/src/claude_agent_sdk/_internal/transport/subprocess_cli.py b/src/claude_agent_sdk/_internal/transport/subprocess_cli.py
index 1f0aac58..b89c18c0 100644
--- a/src/claude_agent_sdk/_internal/transport/subprocess_cli.py
+++ b/src/claude_agent_sdk/_internal/transport/subprocess_cli.py
@@ -59,6 +59,7 @@ def __init__(
             if options.max_buffer_size is not None
             else _DEFAULT_MAX_BUFFER_SIZE
         )
+        self._stderr_lines: list[str] = []
         self._write_lock: anyio.Lock = anyio.Lock()
 
     def _find_cli(self) -> str:
@@ -357,11 +358,10 @@ async def connect(self) -> None:
             if self._cwd:
                 process_env["PWD"] = self._cwd
 
-            # Pipe stderr if we have a callback OR debug mode is enabled
-            should_pipe_stderr = (
-                self._options.stderr is not None
-                or "debug-to-stderr" in self._options.extra_args
-            )
+            # Always pipe stderr so we can capture it for error reporting.
+            # The callback and debug mode flags control whether lines are
+            # forwarded in real-time, but we always collect them.
+            should_pipe_stderr = True
 
             # For backward compat: use debug_stderr file object if no callback and debug is on
             stderr_dest = PIPE if should_pipe_stderr else None
@@ -420,6 +420,9 @@ async def _handle_stderr(self) -> None:
                 if not line_str:
                     continue
 
+                # Always collect stderr lines for error reporting
+                self._stderr_lines.append(line_str)
+
                 # Call the stderr callback if provided
                 if self._options.stderr:
                     self._options.stderr(line_str)
@@ -569,18 +572,23 @@ async def _read_messages_impl(self) -> AsyncIterator[dict[str, Any]]:
             # Client disconnected
             pass
 
-        # Check process completion and handle errors
-        try:
-            returncode = await self._process.wait()
-        except Exception:
-            returncode = -1
+        # Check process exit code (non-blocking if already exited)
+        returncode = self._process.returncode
+        if returncode is None:
+            try:
+                returncode = await self._process.wait()
+            except Exception:
+                returncode = -1
 
         # Use exit code for error detection
         if returncode is not None and returncode != 0:
+            # Give stderr reader a moment to drain remaining output
+            await anyio.sleep(0.1)
+            stderr_output = "\n".join(self._stderr_lines) if self._stderr_lines else None
             self._exit_error = ProcessError(
                 f"Command failed with exit code {returncode}",
                 exit_code=returncode,
-                stderr="Check stderr output for details",
+                stderr=stderr_output,
             )
             raise self._exit_error
 
diff --git a/src/claude_agent_sdk/types.py b/src/claude_agent_sdk/types.py
index 3ea89d5a..8c6ccd5b 100644
--- a/src/claude_agent_sdk/types.py
+++ b/src/claude_agent_sdk/types.py
@@ -681,6 +681,7 @@ class ResultMessage:
     usage: dict[str, Any] | None = None
     result: str | None = None
     structured_output: Any = None
+    errors: list[str] | None = None
 
 
 @dataclass