End-to-end framework that takes one problem through every layer — Problem → Computational Model → Data Model → Data Structure → Algorithm → Invariant/Proof → Complexity → Java → OOP → Design Pattern → Runtime Flow → LLD → Concurrency → Failure → Scale → System Design → Production → Adversarial Verdict. Use when the user wants the layers connected — "end to end", "from DSA to system design", "connect the data structure to the design pattern", "how does this become a production system", "full breakdown of LRU cache / rate limiter / scheduler", "LLD with the algorithm behind it", "walk this through every layer", or names this framework file. Also for evidence-tagged answers (SOURCE-SUPPORTED / DERIVED / INFERRED). Single-layer questions go to the specialist — dsa-pattern-practice, design-pattern-practice, or system-design-architect; this skill is the spine linking them.