Installation

Build Claurst from source or install a pre-built binary. Covers prerequisites, PATH setup, environment variables, and compile-time feature flags.

Prerequisites

Before installing Claurst, make sure you have the following:

• Rust 1.75 or later — Install via rustup.rs. Verify with rustc --version.
• Cargo — Included with the standard Rust toolchain.
• An Anthropic API key — Obtain one from the Anthropic console.
• Linux or macOS — Claurst uses the nix crate for process management, signal handling, and user queries. Windows support is limited.

Claurst relies on the nix crate (v0.29) with the process, signal, and user feature set. These features are Unix-only. On Windows, the BashTool falls back to cmd /C and the PowerShellTool uses pwsh, but some subsystems may not function correctly.

Build from source

1. Clone the repository

   git clone https://github.com/yocxy2/claurst
   
2. Build the release binary

   cd claurst/src-rust
   cargo build --release
   

   Cargo downloads all dependencies declared in Cargo.toml and compiles the full workspace. The first build takes a few minutes. Subsequent builds are incremental.

   The compiled binary is placed at:

   claurst/src-rust/target/release/claude
   
3. Verify the build

   ./target/release/claude --version
   

   You should see the version string printed to stdout.

Pre-built binary

Pre-built binaries are not yet published to a package registry. Until then, build from source using the steps above. Watch the GitHub releases page for binary distributions.

Add to PATH

To run claude from any directory without specifying the full path, add the binary to your PATH.

bash

# Add to ~/.bashrc
echo 'export PATH="$HOME/claurst/src-rust/target/release:$PATH"' >> ~/.bashrc
source ~/.bashrc

zsh

# Add to ~/.zshrc
echo 'export PATH="$HOME/claurst/src-rust/target/release:$PATH"' >> ~/.zshrc
source ~/.zshrc

Copy to a system directory

# Copy the binary to a directory already on your PATH
sudo cp ./target/release/claude /usr/local/bin/claude

After updating your shell profile, open a new terminal session and run:

claude --version

Environment variables

Required

Variable	Description
ANTHROPIC_API_KEY	Your Anthropic API key. Required for all API calls.

Set it in your shell profile for permanent effect:

bash / zsh

export ANTHROPIC_API_KEY="sk-ant-..."

You can also pass it at runtime with the --api-key flag:

claude --api-key "sk-ant-..." "Explain this codebase"

Optional

Variable	Description
ANTHROPIC_BASE_URL	Override the API base URL. Useful for custom endpoints or proxies. Defaults to https://api.anthropic.com.
BRAVE_SEARCH_API_KEY	Enables the Brave Search API for the WebSearch tool. Falls back to DuckDuckGo Instant Answers if not set.

The ANTHROPIC_BASE_URL variable is read by Config::resolve_api_base() at startup. If set, it overrides the compiled-in default for every API call in the session.

Feature flags

Claurst supports several compile-time feature flags that gate advanced systems. These correspond to the original Claude Code feature gates and are inactive in standard builds.

Enable a flag by passing it to Cargo at build time:

cargo build --release --features buddy

Flag	What it enables
BUDDY	Tamagotchi-style companion pet — deterministic gacha species, procedurally generated stats (DEBUGGING, PATIENCE, CHAOS, WISDOM, SNARK), and a Claude-authored personality on first hatch. Rendered as ASCII art beside your input prompt.
PROACTIVE / KAIROS	Always-on assistant mode. Maintains append-only daily log files, receives <tick> prompts at intervals, and proactively acts on observations with a 15-second blocking budget. Includes exclusive tools: SendUserFile, PushNotification, SubscribePR.
COORDINATOR_MODE	Multi-agent orchestration. Claude becomes a coordinator that spawns and directs parallel worker agents across research, synthesis, implementation, and verification phases. Activated at runtime with CLAUDE_CODE_COORDINATOR_MODE=1.

PROACTIVE / KAIROS mode gives Claude the ability to act without an explicit user prompt. Only enable it if you understand the implications. The 15-second blocking budget and append-only log design limit scope, but review the feature flags documentation before use.

Default model and token limits

Claurst ships with the following compiled-in defaults (from cc-core):

Constant	Value
Default model	claude-opus-4-6
Sonnet model	claude-sonnet-4-6
Default max tokens	32,000
Hard token limit	65,536
Auto-compact threshold	90% of context window
Max turns (default)	10

Override the model at runtime with --model or persistently via /model in the TUI. Override max tokens with --max-tokens.

System requirements

Requirement	Details
OS	Linux or macOS (primary). Windows has partial support.
Architecture	x86_64 and ARM64 supported via the Rust standard target matrix.
Rust edition	2021
Minimum Rust version	1.75
Disk space (build)	~500 MB for dependencies and build artifacts
Disk space (binary)	~20 MB for the release binary

Next steps

Quickstart

Run your first session and try the interactive TUI.

Feature flags

Full reference for compile-time and runtime feature gates.

Settings

Configure model, permissions, MCP servers, and hooks via settings.json.

CLAUDE.md

Add project-specific instructions that Claude reads at startup.