rho

A fast, extensible AI coding agent built in Rust. Rho gives an LLM a set of developer tools — file editing, shell access, web search, sub-agents — and runs an autonomous loop to complete coding tasks.

Features

• Multi-provider support — Anthropic Claude, xAI Grok, and any OpenAI-compatible API (Groq, Ollama, etc.)
• Rich tool set — Read/write/edit files, run shell commands, regex search, glob find, web fetch & search, sub-agent tasks
• LINE:HASH editing — Hash-based line anchoring for precise, resilient file edits
• Session persistence — SQLite-backed sessions with full history and resume support
• Autonomous loop — Plan and build modes for hands-off multi-step execution
• Extended thinking — First-class support for reasoning models (Claude Opus, Grok reasoning)
• Project config — Per-project settings via RHO.md or CLAUDE.md with YAML frontmatter
• Post-tool hooks — Run validation commands (tests, lints) automatically after tool use
• Skills & commands — Auto-discover project-specific skills and slash commands
• Streaming output — Text or JSON streaming for integration with other tools

Installation

From source

git clone https://github.com/pyrex41/rho.git
cd rho
cargo install --path .

Install script

curl -fsSL https://raw.githubusercontent.com/pyrex41/rho/main/install.sh | bash

This detects your OS and architecture, downloads the latest release binary, and installs it to ~/.local/bin (or a directory you specify with RHO_INSTALL_DIR).

Pre-built binaries

Download from GitHub Releases. Binaries are available for:

• Linux x86_64 / ARM64
• macOS x86_64 / ARM64 (Apple Silicon)
• Windows x86_64

Quick start

# Set your API key
export ANTHROPIC_API_KEY="sk-..."

# Run a one-shot prompt
rho-cli "add error handling to src/main.rs"

# Use a specific model
rho-cli --model claude-opus "refactor the auth module"

# Enable extended thinking
rho-cli --thinking high "design a caching layer"

# Resume a previous session interactively
rho-cli --resume <session-id>

Usage

rho-cli [OPTIONS] [PROMPT]
rho-cli loop [OPTIONS]

Options

Flag	Description	Default
--model <ID>	Model registry ID or raw model ID	claude-sonnet
--thinking <LEVEL>	Thinking level: off, minimal, low, medium, high	off
--show-thinking	Display thinking output on stderr
--api-key <KEY>	Override API key	env var / keychain
-C, --directory <PATH>	Working directory	current dir
--prompt-file <FILE>	Read prompt from file
--resume <SESSION>	Resume an existing session
--tools <LIST>	Restrict available tools (comma-separated)	all
--system-append <TEXT>	Append to the system prompt
--output-format <FMT>	text or stream-json	text

Autonomous loop

# Build mode — execute tasks from an implementation plan
rho-cli loop

# Plan mode — create or refine IMPLEMENTATION_PLAN.md
rho-cli loop --mode plan

# Custom plan file, more iterations
rho-cli loop --plan my-plan.md --max-iterations 100

Built-in tools

Tool	Description
read	Read files with LINE:HASH format, or list directories
write	Create or overwrite files
edit	Edit files using LINE:HASH anchors or text replacement
bash	Execute shell commands (PTY, up to 1 hour timeout)
grep	Search file contents with regex (respects .gitignore)
find	Find files by glob pattern (respects .gitignore)
task	Launch a sub-agent in a separate context
web_fetch	Fetch a URL and convert to markdown
web_search	Search the web via DuckDuckGo (no API key needed)

Supported models

Anthropic Claude

• claude-sonnet — Claude Sonnet 4.5 (default)
• claude-opus — Claude Opus 4.6 (with extended thinking)
• claude-haiku — Claude Haiku 4.5

xAI Grok

• grok-3, grok-3-mini, grok-2
• grok-4.20-reasoning, grok-4.20-non-reasoning (experimental)

Custom models

Add models via ~/.rho/models.toml:

[[model]]
id = "gpt-4o"
provider = "openai"
model_id = "gpt-4o"
api_key_env = "OPENAI_API_KEY"
context_window = 128000
max_tokens = 16384
thinking = false

Configuration

Create a RHO.md (or CLAUDE.md) in your project root:

---
model: claude-sonnet
thinking: high
memories: true
compact_threshold: 0.7
validation_commands: ["cargo test", "cargo clippy"]
post_tools_hooks:
  - name: tests
    command: cargo test
    timeout: 60
    inject_on_failure: true
    trigger_tools: [write, edit]
---

Additional system prompt instructions go here as markdown.

Environment variables

Variable	Description
ANTHROPIC_API_KEY	Anthropic API key
XAI_API_KEY	xAI / Grok API key
OPENAI_API_KEY	OpenAI API key
RHO_SESSION_DB	Custom path for the session database
RUST_LOG	Tracing filter (default: warn)

Project structure

crates/
├── rho-core        # Agent loop, types, config, event system
├── rho-provider    # LLM provider implementations (Anthropic, OpenAI-compat)
├── rho-tools       # Built-in tool implementations
├── rho-hashline    # LINE:HASH file anchoring
├── rho-server      # HTTP server mode
└── rho-gui         # GUI frontend (iced, in development)
src/
├── main.rs         # CLI entry point
└── loop_runner.rs  # Autonomous loop logic

License

MIT