diff --git a/conductor/workflow.md b/conductor/workflow.md
index c4e0befc..37357bf0 100644
--- a/conductor/workflow.md
+++ b/conductor/workflow.md
@@ -9,6 +9,7 @@
 - **NO COMMENTS** unless explicitly requested
 - Type hints required for all public functions
 - **ImGui Defer Patterns:** Use `imscope` context managers or `_render_window_if_open` dispatch helpers to prevent resource leaks and keep the main loop flat. See `conductor/code_styleguides/python.md` for details.
+- **Error Handling:** All new code uses the Data-Oriented Error Handling convention. `Result[T]` dataclasses for recoverable failures; nil-sentinel dataclasses for missing data; SDK exceptions caught at the boundary and converted to `ErrorInfo`. `Optional[T]` return types are forbidden in `src/mcp_client.py`, `src/ai_client.py`, and `src/rag_engine.py`. See [Data-Oriented Error Handling](./code_styleguides/error_handling.md).
 
 ### CRITICAL: Native Edit Tool Destroys Indentation