custom-engine-implementation

# Custom Engine Implementation Use this skill when adding a new agentic engine definition or extending the behavior-defined engine infrastructure. ## Choose the smallest implementation Prefer a shared Markdown engine definition. Installation, execution, MCP configuration, provider routing, caching, manifests, plugins, network defaults, harness scripts, and log parsing can already be declared through `engine.behaviors`. Only change Go code when the engine needs a reusable behavior that the declarative model cannot express. Add a dedicated Go engine only when the shared behavior-defined runtime cannot run the engine at all. | Need | Implementation | |---|---| | Existing behaviors are sufficient | Add an imported shared engine definition | | A reusable declarative behavior is missing | Extend the definition model and behavior-defined runtime | | The shared runtime is fundamentally unsuitable | Add a dedicated Go engine and register it | The relevant implementation is in: - `pkg/workflow/engine_definition.go` for the definition model and catalog - `pkg/workflow/behavior_defined_engine.go` for the shared runtime - `pkg/workflow/engine_definition_loader.go` for embedded built-in definitions - `pkg/workflow/agentic_engine.go` for dedicated Go engine registration - `pkg/parser/schemas/main_workflow_schema.json` for the workflow schema ## Study representative engines Read the closest examples before making changes: - `.github/workflows/shared/opencode.md`: npm installation, ...