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+# GitHub Copilot Instructions for oha
+
+## Project Overview
+
+`oha` (おはよう) is an HTTP load testing tool written in Rust, inspired by `rakyll/hey`. It provides real-time TUI (Terminal User Interface) visualization of load testing results using `ratatui`.
+
+## Key Technologies & Dependencies
+
+- **Language**: Rust (edition 2024, MSRV 1.85)
+- **Async Runtime**: `tokio` with full features
+- **HTTP Client**: `hyper` (v1.4) with HTTP/1, HTTP/2 support
+- **TUI**: `ratatui` with `crossterm` backend
+- **CLI**: `clap` with derive features
+- **Memory Allocator**: `tikv-jemallocator` (non-MSVC targets)
+- **Error Handling**: `anyhow` and `thiserror`
+- **JSON**: `serde` and `serde_json`
+- **Database**: `rusqlite` with bundled SQLite
+- **Networking**: `hickory-resolver` for DNS resolution
+
+## Project Structure
+
+```
+src/
+├── lib.rs           # Main library with CLI definitions and core logic
+├── main.rs          # Binary entry point
+├── client.rs        # HTTP client implementations (HTTP/1, HTTP/2)
+├── client_h3.rs     # HTTP/3 client (feature-gated)
+├── aws_auth.rs      # AWS signature authentication
+├── db.rs           # Database operations for storing results
+├── histogram.rs     # Statistical histogram implementation
+├── monitor.rs       # Real-time monitoring and TUI
+├── printer.rs       # Output formatting and display
+├── result_data.rs   # Data structures for test results
+├── timescale.rs     # Time-based scaling utilities
+├── tls_config.rs    # TLS configuration
+├── url_generator.rs # URL generation with patterns
+└── pcg64si.rs      # Random number generation
+```
+
+## Features & Build Configurations
+
+### Default Features
+- `rustls` - Uses rustls for TLS (default)
+
+### Optional Features
+- `native-tls` - Use native TLS instead of rustls
+- `vsock` - Enable VSOCK support for VM communication
+- `http3` - Experimental HTTP/3 support via `h3` library
+
+### Build Examples
+```bash
+# Default build with rustls
+cargo build
+
+# With native TLS
+cargo build --no-default-features --features native-tls
+
+# With HTTP/3 support
+cargo build --features http3
+
+# With VSOCK support
+cargo build --features vsock
+```
+
+## Code Style & Conventions
+
+### Error Handling
+- Use `anyhow::Result<T>` for functions that can fail
+- Use `anyhow::bail!()` for early returns with error messages
+- Use `anyhow::ensure!()` for validation with custom error messages
+- Use `thiserror` for custom error types (when needed)
+
+### Async Code
+- All async code uses `tokio`
+- Use `tokio::spawn` for concurrent tasks
+- Prefer `async/await` over manual future polling
+
+### CLI Structure
+- Use `clap` derive macros for argument parsing
+- Main configuration struct is typically in `lib.rs`
+- Support both short and long argument forms
+
+### TUI Guidelines
+- Use `ratatui` for all terminal UI components
+- Handle terminal resize events
+- Implement proper cleanup on exit
+- Use `crossterm` for terminal control
+
+### HTTP Client Patterns
+- Support HTTP/1.1, HTTP/2, and optionally HTTP/3
+- Handle connection pooling and reuse
+- Implement proper timeout handling
+- Support custom headers and authentication
+
+### Performance Considerations
+- Use `jemalloc` allocator for better memory performance
+- Leverage `tokio`'s async runtime efficiently
+- Minimize allocations in hot paths
+- Use streaming where appropriate for large responses
+- Use PCG64SI PRNG (`pcg64si.rs`) for high-performance random number generation
+
+## Testing
+
+### Test Structure
+- Integration tests in `tests/` directory
+- Use `assert_cmd` for CLI testing
+- Test server setup with `axum` and `axum-server`
+- SSL/TLS testing with provided certificates
+
+### Test Data
+- Test certificates: `tests/common/server.cert` and `tests/common/server.key`
+- Common test utilities in `tests/common/mod.rs`
+
+## Development Guidelines
+
+1. **Cross-platform**: Ensure code works on Linux, macOS, and Windows
+2. **Feature gates**: Use appropriate feature gates for optional dependencies
+3. **Documentation**: Document public APIs with rustdoc comments
+4. **Performance**: Profile and optimize hot paths
+5. **Error messages**: Provide helpful, actionable error messages
+6. **CLI UX**: Follow Unix conventions for command-line tools
+
+## Dependencies to Prefer
+
+- **HTTP**: `hyper` and `hyper-util` for HTTP client functionality
+- **TLS**: `rustls` by default, `native-tls` as fallback
+- **Async**: `tokio` ecosystem (`tokio-util`, `tokio-rustls`, etc.)
+- **CLI**: `clap` for argument parsing
+- **Serialization**: `serde` ecosystem
+- **Random**: `rand` and `rand_core` for randomization needs
+- **Time**: `chrono` for time handling
+
+## Platform-specific Code
+
+- Use `#[cfg(unix)]` for Unix-specific features (like `rlimit`)
+- Use `#[cfg(not(target_env = "msvc"))]` for non-MSVC Windows builds
+- Handle platform differences in TLS and networking code appropriately