Discuss 'Tail-Recursive Conditional Types' and the 1000+ depth limit.

TS 4.5+ supports tail-call optimization for recursive types, allowing extremely deep type transformations.

Recursive types used to hit a hard limit around 50 levels. By ensuring the recursive call is the 'immediate' result of a conditional branch (the tail position), TypeScript can flatten the call stack. This allows for complex string parsing and massive array manipulations that previously crashed the compiler[cite: 1].