Extract Shared Types

Extract Shared Types

Invoke as $extract-shared-types.

Use this skill for type hoisting, type barreling, shared types/ directories, import honesty, and circular-dependency prevention when the requested change is explicitly structural and behavior-preserving.

Process

1. Establish scope.

   • Read $ARGUMENTS for a package, app, directory, or domain.
   • If no scope is provided, inspect the repo and choose the smallest coherent area with shared exported types.
   • Read project instructions, package manifests, TypeScript config, path aliases, lint rules, package export maps, and existing types/ or barrel conventions.

2. Classify declarations before editing.

   • Candidate moves: exported type aliases, interface declarations, ambient declarations, generic helper shapes, DTO/result shapes, props/state shapes, and domain data shapes.
   • Do not move runtime values: functions, constants, classes, runtime enums, schemas, validators, database/API clients, React components, business logic, or anything imported as a value.
   • Treat TypeScript enum as runtime unless the project already uses const enum safely and the compiler settings make the move clearly type-only.

3. Design the target type layout.

   • Create or reuse a dedicated types/ directory at the nearest appropriate boundary.
   • Organize files by domain, feature, or package convention rather than by source file name when a domain boundary is clear.
   • Prefer direct imports from domain type files. Add types/index.ts only if the project already uses barrels or repeated type imports would otherwise become noisy.

4. Move type declarations.

   • Move only the approved type declarations.
   • Preserve exported names, generic parameters, comments that explain shape semantics, and public visibility.
   • Keep runtime implementation files focused on runtime logic, importing moved declarations with import type where supported.

5. Update imports and compatibility.

   • Update internal imports to the new type files.
   • Use import type for type-only imports and avoid creating new value imports from types/.
   • If old import paths are part of a public API or package boundary, leave type-only re-exports from the original module rather than forcing a breaking migration.
   • Avoid widening public barrels unless the repo already exposes that type surface intentionally.

6. Verify behavior preservation.

   • Run the narrowest relevant typecheck, tests, lint/import checks, and dependency-cycle checks available.
   • Inspect the diff for runtime changes: implementation logic, emitted values, schema definitions, package exports, route behavior, and component behavior should not change.
   • If verification fails, fix import/type issues without changing runtime behavior.

Output

When reporting completion, include:

• Scope refactored.
• Type files created or reused.
• Compatibility re-exports left in place, if any.
• Verification commands run and their results.
• Any skipped candidates with the reason they were runtime-coupled or public-API-sensitive.

Alignment Page

Follow the shared alignment-page convention via the packaged convention resolver; output path is alignment/extract-shared-types-{topic}.html.

Constraints

• Zero runtime behavior changes.
• Do not move declarations unless they are type-only.
• Do not introduce dependency upgrades, schema redesigns, or broad module restructuring.
• Do not remove public import paths unless the user explicitly requests a breaking change.
• Preserve unrelated user changes in the working tree.

Default Shipping Contract

Follow the shared shipping contract convention in CLAUDE.md.