Design .NET types for performance. Seal classes, use readonly structs, prefer static pure functions, avoid premature enumeration, and choose the right collection types.

Microsoft.Extensions.Options patterns including IValidateOptions, strongly-typed settings, validation on startup, and the Options pattern for clean configuration management.

Build responsive email templates using MJML markup language. Compiles to cross-client HTML that works in Outlook, Gmail, and Apple Mail. Includes template renderer, layout patterns, and variable substitution.

Use when configuring Playwright BDD projects, setting up defineBddConfig(), configuring feature and step file paths, and integrating with Playwright config.

Choose the right serialization format for .NET applications. Prefer schema-based formats (Protobuf, MessagePack) over reflection-based (Newtonsoft.Json). Use System.Text.Json with AOT source generators for JSON scenarios.

Perform a non-destructive cross-artifact consistency and quality analysis across spec.md, plan.md, and tasks.md after task generation.

Generate a custom checklist for the current feature based on user requirements.

Identify underspecified areas in the current feature spec by asking up to 5 highly targeted clarification questions and encoding answers back into the spec.

Create or update the project constitution from interactive or provided principle inputs, ensuring all dependent templates stay in sync.

Execute the implementation plan by processing and executing all tasks defined in tasks.md

Create or update the feature specification from a natural language feature description.

Convert existing tasks into actionable, dependency-ordered GitHub issues for the feature based on available design artifacts.

Answer questions about BookWorm bookstore policies, shipping, returns, account management, loyalty programs, gift cards, and other non-book-specific services. Use when customers ask about store operations or services.