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@@ -4,48 +4,98 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Project Overview
 
-**Dose** is a DOS-style command shell implementation written in Rust. The project aims to recreate classic DOS commands and shell functionality in a modern Rust environment, providing a nostalgic DOS computing experience.
+**Dose** is a DOS-style command shell implementation written in Zig. Originally started in Rust, the project has been completely rewritten in Zig to provide a nostalgic DOS computing experience with modern systems programming capabilities.
 
 ## Development Commands
 
 ```bash
-# Development
-cargo run                 # Run in debug mode with REPL shell
-cargo build              # Build debug version  
-cargo check              # Fast syntax/type checking
-cargo clean              # Clean build artifacts
-
-# Release builds (heavily optimized for size)
-cargo build --release    # Optimized build with LTO and size optimization
-cargo run --release      # Run optimized version
+# Development (Zig)
+zig build                 # Build debug version
+zig build run             # Build and run in debug mode
+zig build test            # Run unit tests
+zig build -Doptimize=ReleaseFast  # Optimized build
+
+# Legacy (Original Rust - archived)
+cargo run                 # Run in debug mode with REPL shell  
+cargo build              # Build debug version
 ```
 
 ## Architecture
 
 ### Command System Design
-The application uses a type-safe command architecture with Rust enums:
+The application uses a type-safe command architecture with Zig unions and enums:
 
-- **`Command`**: Top-level enum supporting pipes, redirections, external programs, and builtins
-- **`BuiltinCommand`**: Comprehensive DOS command set covering file operations, shell control, scripting, and utilities
+- **`Command`**: Top-level union supporting pipes, redirections, external programs, and builtins
+- **`BuiltinCommand`**: Comprehensive DOS command set covering file operations, shell control, and utilities
 - **`FileSpec`**: Handles console (`Con`) vs file path targets for I/O redirection
+- **`InputSource`**: Manages input redirection from files with line-by-line processing
+- **`OutputCapture`**: Buffers command output for redirection to files
+
+### Implementation Status
+
+#### ✅ **Fully Implemented Features**
+- **Interactive REPL Shell**: Command-line interface with DOS-style prompts (`C:\PATH>`)
+- **Command Parsing**: Complete lexer/parser for DOS command syntax with quote support
+- **Built-in Commands**: Core DOS commands with authentic behavior and error messages
+- **External Command Execution**: Full process spawning with I/O redirection support
+- **I/O Redirection**: Complete input (`<`), output (`>`), and append (`>>`) redirection
+- **Error Handling**: DOS-authentic error messages and proper exit codes
+- **Path Formatting**: DOS-style path display with drive letters and 8.3 filename conversion
+
+#### 📋 **Built-in Commands Available**
+- **`ECHO`** (with ON/OFF variants) - Text output and echo state control
+- **`CLS`** - Clear screen with ANSI escape sequences
+- **`EXIT`** - Exit the shell
+- **`VER`** - Version information display
+- **`DATE`** - Current system date with proper calendar calculations
+- **`TIME`** - Current system time display
+- **`DIR`** - Directory listing with file sizes and counts
+- **`TYPE`** - Display file contents with binary character filtering
+- **`SORT`** - Alphabetical line sorting with input redirection support
+
+#### 🔧 **External Command Support**
+- **Process Spawning**: Uses `std.process.Child` for external program execution  
+- **Argument Passing**: Proper command-line argument handling
+- **I/O Redirection**: Full stdin/stdout/stderr redirection support
+- **Error Handling**: DOS-compatible "command not found" messages
+- **Exit Code Propagation**: Proper process exit code handling
 
-### Current Implementation Status
-- **Implemented**: Basic REPL shell with `rustyline` for interactive input
-- **Stubbed**: Command parsing (`parse` method returns "Not implemented")  
-- **Planned**: Full DOS command execution based on the `BuiltinCommand` enum
+#### 🔀 **Redirection System**
+- **Input Redirection** (`<`): Read file content as command input
+- **Output Redirection** (`>`): Write command output to file (overwrite)
+- **Append Redirection** (`>>`): Append command output to file
+- **Combined Redirection**: Support for both input and output redirection simultaneously
+- **Device Handling**: Proper CON/LPT/PRN device recognition and error handling
 
-### Key DOS Commands Planned
-File operations (`type`, `copy`, `xcopy`, `dir`, `tree`), shell control (`prompt`, `echo`, `set`, `chdir`), and classic utilities (`date`, `time`, `cls`, `mem`).
+### Key Technical Features
 
-### Error Handling
-Uses modern Rust error handling with `eyre::Result` and `color-eyre` for enhanced error reporting with colored output.
+#### **Memory Management**
+- **Allocator-based**: Uses Zig's `GeneralPurposeAllocator` for all dynamic memory
+- **RAII Pattern**: Proper resource cleanup with `defer` statements
+- **Leak Detection**: Built-in memory leak detection in debug builds
+
+#### **Error Handling**  
+- **Zig Error Unions**: Native `!T` error handling instead of exceptions
+- **DOS-Authentic Messages**: Faithful reproduction of classic DOS error text
+- **Graceful Degradation**: Robust error recovery and user guidance
+
+#### **Cross-Platform Support**
+- **Zig Standard Library**: Portable file system and process operations
+- **ANSI Terminal Support**: Cross-platform terminal manipulation
+- **Path Handling**: DOS-style path formatting on all platforms
 
 ### Dependencies
-- **`rustyline`**: Interactive command-line editing and history
-- **`crossterm`**: Cross-platform terminal manipulation
-- **`prettytable-rs`**: Table formatting for command output
-- **`eyre`/`color-eyre`**: Enhanced error handling and reporting
-- **`thiserror`**: Error type derivation macros
-
-## Release Optimization
-The release profile is configured for maximum size optimization with LTO, `opt-level = "z"`, symbol stripping, and single codegen unit compilation.
+
+**Zero External Dependencies** - The Zig implementation uses only the standard library:
+- **`std.process`**: External command execution and process management
+- **`std.fs`**: File system operations for I/O redirection and DIR command
+- **`std.mem`**: Memory management and string operations
+- **`std.time`**: System time access for DATE/TIME commands
+- **`std.io`**: Terminal I/O and file operations
+
+### Build Configuration
+
+The project uses Zig's standard build system with optimizations:
+- **Debug builds**: Full error checking and memory leak detection
+- **Release builds**: Size and speed optimized for production use
+- **Cross-compilation**: Native Zig cross-platform compilation support