claude-rust

A Rust reimplementation of Claude Code -- the agentic tool-use loop backed by the Anthropic streaming API.

The TypeScript original has ~1,900 files. This project distills it to its essence: a multi-crate Rust workspace that streams responses from the Anthropic Messages API, detects tool-use requests, executes tools locally, feeds results back, and loops until the model is done.

Architecture

Every crate follows Clean Architecture with domain/, application/, and infrastructure/ layers.

claude-rust-auth        - Credential resolution (macOS Keychain / Linux keyring OAuth + API key fallback)
claude-rust-config      - Settings loading and merging (global + project)
claude-rust-errors      - AppError enum, axum IntoResponse impl
claude-rust-types       - Shared traits (Tool, Provider, PermissionChecker) and message types
claude-rust-tools       - Tool implementations and ToolRegistry (+ MCP support)
claude-rust-provider    - Anthropic HTTP + SSE streaming client with thinking support
claude-rust-engine      - Agentic tool-use loop with streaming callbacks, retry, and sub-agents
claude-rust-permission  - Config-aware permission checker with interactive prompts and skill scoping
claude-rust-memory      - Session persistence (JSON files)
claude-rust-commands    - Slash commands and @file references
claude-rust             - Interactive terminal REPL (the main binary)
claude-rust-server      - axum HTTP server (POST /chat, GET /health)

Core Loop

user input
  -> expand @file references + image attachments
  -> build Conversation
  -> provider.stream() (with extended thinking if enabled)
  -> accumulate StreamEvents
  -> if stop_reason == ToolUse -> check permission -> execute tools -> append results -> loop
  -> if overloaded -> retry with exponential backoff (up to 3 attempts)
  -> else -> return final text -> auto-save session

Bounded by max_turns (default 20). Tool errors are sent back as is_error: true so the model can self-correct.

Authentication

Credentials are resolved automatically in this order:

1. ANTHROPIC_API_KEY environment variable -- uses api.anthropic.com with x-api-key header.
2. System Keychain -- reads the OAuth token stored by Claude Code. Uses api.claude.ai with Authorization: Bearer header. Works on macOS (Keychain) and Linux (secret-tool/keyring).

If you already have Claude Code installed and logged in, it just works -- no extra configuration needed.

Features

Interactive CLI

• Rich terminal UI with bordered input box, permission mode badges, and git branch display
• Session persistence with resume on startup
• Streaming output with indicatif progress spinners and task progress display
• Vi mode editing (toggle with /vim)
• Command autocomplete with dropdown suggestions
• History search (Ctrl+R)
• Image paste from clipboard (Ctrl+V) with [Image #N] markers
• Background task execution (Ctrl+B)
• Stash/restore input buffer (Ctrl+S)
• @file references: type @Cargo.toml to inject file contents
• Interactive permission prompts for dangerous tool calls
• Retry with exponential backoff on API overload
• Extended thinking support (/think)

Slash Commands

Custom Skills & Commands

Load custom slash commands from markdown files with YAML frontmatter:

Skills (~/.claude/skills/ or .claude/skills/):

~/.claude/skills/
  my-skill/
    SKILL.md       # Directory format (preferred)

Legacy Commands (~/.claude/commands/ or .claude/commands/):

~/.claude/commands/
  smart-push.md    # Standalone .md format
  my-tool/
    SKILL.md       # Directory format also supported

Frontmatter Format

---
name: smart-push
description: Intelligent git workflow with grouped commits
argument-hint: [optional commit message]
allowed-tools: Bash(git add:*), Bash(git status:*), Bash(git commit:*), Bash(git push:*)
when_to_use: Use when the user wants to commit and push changes
user-invocable: true
---

Your prompt template here. Use $ARGUMENTS for user-provided arguments.

• allowed-tools: Auto-approve matching tool calls during skill execution
• when_to_use: Included in system prompt so the model can suggest the skill
• user-invocable: Set to false to hide from autocomplete (default: true)

Built-in Tools

Configuration

Settings are loaded from ~/.claude/settings.json (global) and .claude/settings.json (project), with project overriding global:

{
  "model": "claude-sonnet-4-6",
  "max_turns": 20,
  "max_tokens": 16384,
  "permissions": {
    "allow": ["read", "glob", "grep", "bash(git *)"],
    "deny": ["bash(rm -rf *)"]
  },
  "hooks": {
    "PreToolUse": [{ "matcher": "bash", "command": "echo $CLAUDE_TOOL_INPUT" }],
    "PostToolUse": [{ "command": "notify-send 'Tool done'" }],
    "SessionStart": [{ "command": "echo 'Session started'" }],
    "Stop": [{ "command": "echo 'Session ended'" }]
  }
}

CLAUDE.md

Project instructions are loaded hierarchically from CLAUDE.md and .claude/CLAUDE.md files, walking up from the current directory to ~/.claude/CLAUDE.md. All found files are concatenated into the system prompt.

MCP (Model Context Protocol)

External tool servers are configured via .mcp.json, .claude/mcp.json, or ~/.claude/mcp.json:

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "my-mcp-server"],
      "env": { "API_KEY": "..." }
    }
  }
}

HTTP Server

• GET /health -- health check
• POST /chat -- send messages and get responses

Environment Variables

Prerequisites

• Rust 1.85+ (2024 edition)
• One of:
  • An Anthropic API key, or
  • An existing Claude Code installation (credentials are read from the system keychain)

Quick Start

Install from source

git clone https://github.com/maulanasdqn/claude-rust.git
cd claude-rust
cargo install --path claude-rust

Run

# Using your existing Claude Code session (no env var needed)
claude-rust

# Or with an explicit API key
ANTHROPIC_API_KEY=sk-ant-... claude-rust

Keyboard Shortcuts

Project Structure

.
├── Cargo.toml                          Workspace root
├── claude-rust/                        CLI binary
│   └── src/
│       ├── main.rs
│       └── infrastructure/
│           ├── app_loop.rs             Main REPL loop
│           ├── skills.rs               Skill/command loader
│           ├── command_handler.rs       Slash command dispatcher
│           ├── command_extras/          Review, commit, export, memory
│           ├── run_engine.rs            Engine runner with progress display
│           ├── event_renderer/          Streaming event rendering
│           └── terminal/
│               ├── input.rs            Input box rendering
│               ├── input_raw.rs        Raw mode input + clipboard
│               ├── input_handler.rs    Key event processing + vi mode
│               ├── input_suggest.rs    Command autocomplete
│               ├── input_search.rs     History search (Ctrl+R)
│               ├── input_select.rs     Interactive list picker
│               ├── banner.rs           Startup banner
│               └── system_prompt.rs    System prompt builder
├── claude-rust-auth/                   Credential resolution
│   └── src/
│       ├── domain/credential.rs
│       ├── application/resolve_credential.rs
│       └── infrastructure/keychain_provider.rs
├── claude-rust-config/                 Settings loading + merging
│   └── src/
│       ├── domain/config.rs            Settings, Hooks, Permissions structs
│       └── application/load_config.rs  Global + project merge
├── claude-rust-errors/
│   └── src/lib.rs                      AppError, IntoResponse
├── claude-rust-types/
│   └── src/domain/
│       ├── message.rs                  Message, ContentBlock, Conversation
│       ├── tool.rs                     Tool trait, PermissionLevel
│       ├── provider.rs                 Provider trait, StreamEvent
│       └── permission.rs              PermissionChecker trait, AllowAll
├── claude-rust-tools/
│   └── src/
│       ├── application/registry.rs     ToolRegistry
│       └── infrastructure/
│           ├── bash_tool.rs            Shell execution
│           ├── read_tool.rs            File reading
│           ├── file_write_tool.rs      File creation
│           ├── file_edit_tool.rs       Find-and-replace editing
│           ├── glob_tool.rs            File pattern matching
│           ├── grep_tool.rs            Content search
│           ├── web_fetch_tool.rs       URL fetching
│           ├── web_search_tool.rs      Web search
│           ├── ask_user_tool.rs        Interactive questions
│           ├── todo_write_tool.rs      Task management
│           ├── todo_read_tool.rs       Task reading
│           ├── plan_mode_tool.rs       Plan mode enter/exit
│           ├── mcp_tool.rs             MCP external tools
│           └── todo_store.rs           Task state store
├── claude-rust-provider/
│   └── src/infrastructure/
│       ├── anthropic_provider.rs       Streaming client + thinking
│       ├── request_builder.rs          API request serialization
│       └── sse_parser.rs              Server-sent events parser
├── claude-rust-engine/
│   └── src/application/
│       ├── query_engine.rs             Agentic tool-use loop
│       ├── tool_executor.rs            Permission-checked execution
│       ├── hook_runner.rs              Pre/Post tool hooks
│       └── undo.rs                     File edit undo stack
├── claude-rust-permission/
│   └── src/infrastructure/
│       ├── config_aware_checker.rs     Config + skill-scoped permissions
│       └── terminal_checker.rs         Interactive y/n prompts
├── claude-rust-memory/
│   └── src/
│       ├── domain/session_repository.rs
│       ├── application/{save,load}_session.rs
│       └── infrastructure/file_session_repository.rs
├── claude-rust-commands/
│   └── src/
│       ├── domain/command.rs           SlashCommand enum
│       ├── application/
│       │   ├── parse_command.rs
│       │   ├── execute_command.rs
│       │   └── expand_references.rs    @file and image expansion
│       ├── infrastructure/handlers/
│       └── tests/
└── claude-rust-server/
    └── src/
        ├── main.rs
        └── infrastructure/http/
            ├── routes.rs
            ├── handlers.rs
            └── dto.rs

Dependency DAG

claude-rust-errors
  <- claude-rust-types
       <- claude-rust-tools
       <- claude-rust-permission
  <- claude-rust-auth
       <- claude-rust-provider
  <- claude-rust-config
  <- claude-rust-memory
  <- claude-rust-commands
            <- claude-rust-engine
                 <- claude-rust (CLI)
                 <- claude-rust-server

Building

cargo build --workspace
cargo build --workspace --release
cargo test --workspace

License

MIT