Introduction

Radius is a daemon-based code editing toolkit designed for LLM agents. It provides semantic code operations via Language Server Protocol (LSP) integration with efficient in-memory text buffering using a Piece Tree data structure.

Why Radius?

Traditional file editing tools treat code as plain text. Radius understands your code semantically:

• Variable operations know about scopes and references
• File renames automatically update imports
• Conflict resolution understands merge markers
• All changes are tracked with undo/redo support

Architecture

radius (CLI) ─── Unix Socket IPC ───> radiusd (Daemon)
                                          │
                    ┌─────────────────────┼─────────────────────┐
                    │                     │                     │
              BufferManager          LspManager          HistoryTracker
              (Piece Tree)           (LSP clients)       (Undo/Redo)

Components

Component	Responsibility
CLI	Thin client forwarding commands to daemon
Daemon	Long-running process managing state
BufferManager	In-memory text editing with Piece Tree
LspManager	LSP client lifecycle management
HistoryTracker	Per-project undo/redo history

Key Features

Semantic Operations

Radius uses LSP to understand your code:

# Find all references to a variable
radius read-var src/main.ts --var userName

# Rename with semantic awareness
radius modify-var src/main.ts --from userName --to customerName

Efficient Buffering

The Piece Tree data structure provides:

• O(log n) insertions and deletions
• Memory-efficient representation of edits
• External change detection via mtime tracking
• LRU cache limiting memory usage

Undo/Redo

Every change is tracked:

radius str-replace file.ts --old "foo" --new "bar"
radius undo  # Restore previous state
radius redo  # Re-apply the change

Next Steps

• Installation - Set up Radius on your system
• Quick Start - Your first commands
• Commands - Full command reference