TypeScript Recursive Types in 2026: Modeling JSON, Trees, and Deep Partial Without Hitting the Limit

Short summary

A technical guide to TypeScript recursive types for modeling deeply nested structures like JSON, trees, and configuration objects. Covers the recursion depth limit (~50 expansions in TS 5.6+), tail-recursive patterns to avoid hitting it, and the importance of explicit base cases. Includes practical examples of DeepPartial and DeepReadonly utility types that compose cleanly with mapped and conditional types.

• •Recursive types let TypeScript track type safety at arbitrary depth for nested JSON, trees, and configs
• •Depth limit of ~50 expansions in TS 5.6+ is rarely hit with well-formed structures; tail-recursive patterns help
• •Base cases (primitives, null, unknown) are mandatory to terminate recursion and prevent infinite expansion

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