fib-with-claude

Behavior-driven design: write executable specifications BEFORE any implementation code. Reads /docs/PLAN.md for the build plan and /docs/STORIES.md for user stories, and stops to ask for either if it is missing. Generates TypeScript spec files in nested blocks — Feature > Scenario > Specification — where each Scenario arranges all of its data in a beforeAll/beforeEach, every Specification makes exactly one assertion, happy-path specs come first and exhaustively, and sad-path specs live in their own separate blocks. Auto-detects the runner: bun:test if the project uses Bun, otherwise Jest. Use when starting a new project or feature, when asked to "spec out", "write the tests first", do BDD/TDD, or turn a plan or user stories into a test suite. Ships PLAN.md and STORIES.md scaffolds plus ready-to-copy bun:test and Jest spec templates.

General object-oriented design principles for TypeScript projects that are NOT part of SOLID or the Gang of Four patterns — coupling and cohesion (incl. connascence), DRY, YAGNI, KISS, separation of concerns, encapsulation / information hiding, Tell Don't Ask, Law of Demeter, composition over inheritance, program-to-an-interface, Command–Query Separation, Principle of Least Astonishment, and fail-fast. Use when designing or refactoring modules, reviewing code for coupling/duplication/leaky-abstraction smells, deciding whether an abstraction earns its keep, or answering "is this good design / which principle applies" questions that SOLID and GoF do not cover.

Gang of Four design patterns reference for TypeScript projects. Use when choosing or implementing a design pattern, refactoring toward a known pattern, reviewing code for pattern misuse, or answering "which pattern fits here" questions. Covers all 23 creational, structural, and behavioral patterns with idiomatic TypeScript examples and guidance on when (and when not) to use each.

Idiomatic TypeScript conventions and best practices: strict compiler settings, type-level modeling (discriminated unions, branded/nominal types, `as const`/`satisfies`, exhaustiveness), `unknown` over `any`, immutability, error handling with a Result type, null/undefined hygiene, async/promise rules, module and naming conventions, and the project rule that every class exposes `toString()` and `toJSON()`. Use when writing new TypeScript, doing code review, setting up a tsconfig, modeling a domain type, or answering "what is the idiomatic TypeScript way to do this" questions. Ships ready-to- copy templates for value objects, entities, errors, Result, state machines, branded types, type guards, and a strict tsconfig.