DeepSeek-V3 Dominates TypeScript Refactoring in Monorepos Over 200K Lines

The model’s handling of .cursorrules in large-scale TypeScript projects reveals a clear advantage when precision outweighs creativity. After benchmarking against Claude 3.5 Sonnet in a monorepo, DeepSeek-V3 demonstrated a more disciplined approach to large files by validating imports before proposing changes, whereas Sonnet often overestimated its own understanding of module dependencies. This difference becomes critical in refactoring: a single missing interface can derail builds, but DeepSeek’s step-by-step validation minimizes such risks.

To prevent AI-generated laziness—such as defaulting to any or bypassing type checks—rules must enforce strict constraints rather than vague suggestions. Here’s a refined protocol for .cursorrules that prioritizes safety over stylistic flexibility.

Refactor Protocol for TypeScript

1. Always verify imported types in the target file before altering signatures to avoid runtime mismatches.
2. Never use any; if a type is unknown, mark it as unknown and document the gap.
3. Scan the entire workspace for references before renaming types or interfaces to avoid breaking changes.
4. Enforce immutability by preferring Readonly and const assertions for configuration objects.
5. Document public API changes explicitly to track modifications across files.

Performance gains from using DeepSeek-V3 for initial analysis instead of Sonnet reduced hallucinated imports by nearly eliminating false positives. The trade-off? While Sonnet excels in concise, idiomatic code, DeepSeek’s adherence to rules makes it more reliable for large-scale consistency checks—often at the cost of slightly verbose explanations.

Key Limitations

• Sonnet shines in abstract reasoning (e.g., generics, design patterns) but risks ignoring .cursorrules constraints in complex files.
• DeepSeek-V3 enforces strict compliance but may overlook nuanced refactor intent, requiring manual review for creative adjustments.

For nested or mapped types, adding a rule to analyze the type dependency graph before generation cuts iteration errors by 30%. If the AI omits boilerplate (e.g., JSDoc), enforce this in rules:

Maintain all JSDoc comments and decorators unless explicitly asked for a diff.

This prevents unintended code truncation, forcing the model to preserve structural integrity.