Workflow Series (02): Design Patterns — Four-Layer Architecture, Three Context Modes, and Approval Gate Design

From Script to Engineering An early-stage workflow is often a single file: one Markdown that describes everything, with all configuration hardcoded. This works at small scale. As the workflow grows, three problems appear: Changing a timeout requires finding and updating multiple locations Subagent task prompts are scattered through the workflow definition, impossible to test independently Security policy and business logic are mixed together, making compliance review painful The four-layer…