# Pattern Doc Entity
### Scope
- **Purpose**: Document architectural patterns applied in the claude_runner_core library design.
- **Responsibility**: Index of pattern doc instances covering the builder pattern design rationale and API shape.
- **In Scope**: Builder pattern problem, solution, applicability, and consequences as applied here.
- **Out of Scope**: API surface details (→ `api/`), type definitions (→ `data_structure/`), feature behavior (→ `feature/`).
### Overview Table
| 001 | [Command Builder](001_command_builder.md) | Fluent builder pattern for Claude Code command construction | ✅ |