flowgraph/tasks/error-hierarchy.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
error/hierarchy	Implement FlowgraphError hierarchy with all error classes and validation result types	completed	setup/project-init	narrow	low	component	implementation

Description

Implement the complete error hierarchy per error-handling.md. This includes thrown error classes (for construction invariant violations) and structured result types (for validation functions that never throw).

Acceptance Criteria

• src/error/index.ts exports all error classes and result types
• FlowgraphError base class extending Error with name: "FlowgraphError"
• ConstructionError extending FlowgraphError — base for construction-time errors
• DuplicateNodeError extending ConstructionError — key property
• DuplicateEdgeError extending ConstructionError — source, target properties
• NodeNotFoundError extending ConstructionError — key property
• CycleError extending ConstructionError — cycles: string[][] property
• InvalidInputError extending ConstructionError — errors: ValidationError[] property
• InvalidTransitionError extending FlowgraphError — requestId, from: CallStatus, to: CallStatus properties
• ValidationError interface — { type: "schema", nodeKey, field, message, value? }
• GraphValidationError interface — { type: "graph", category: "cycle" | "dangling-reference" | "orphan-node" | "status-inconsistency", details: unknown }
• TypeIncompatError interface — { type: "type-compat", sourceKey, targetKey, compatible: false, mismatches: TypeMismatch[] }
• TypeMismatch interface — { path, expected, actual }
• AnyValidationError union type — ValidationError | GraphValidationError | TypeIncompatError
• Throwing vs returning contract clearly documented in JSDoc
• Unit tests: each error class constructs correctly, result types validate, instanceof checks work

References

• docs/architecture/error-handling.md — complete error hierarchy, throwing vs returning contract

Notes

To be filled by implementation agent

Summary

To be filled on completion