Open Agent SDK (Rust)

A lightweight, open-source Rust SDK for building AI agents. Run the full agent loop in-process — no CLI or subprocess required. Deploy anywhere: cloud, serverless, Docker, CI/CD.

Also available in TypeScript and Go.

Features

• Multi-Provider — Supports both Anthropic Messages API and OpenAI Chat Completions API, with auto-detection by model name
• Agent Loop — Streaming agentic loop with tool execution, multi-turn conversations, and cost tracking
• 25+ Built-in Tools — Bash, Read, Write, Edit, Glob, Grep, WebFetch, WebSearch, Agent (subagents), AskUser, Tasks, Teams, Plans, Worktrees, Todos, Cron, LSP, Config, MCP Resources, ToolSearch
• Session Persistence — Save, load, fork, and resume conversations across sessions
• MCP Support — Connect to MCP servers via stdio, HTTP, and SSE transports
• Permission System — Configurable tool approval with allow/deny rules and filesystem path validation
• Hook System — 20+ hook events: PreToolUse, PostToolUse, SessionStart/End, SubagentStart/Stop, TaskCreated/Completed, FileChanged, PreCompact/PostCompact, and more
• Extended Thinking — Support for extended thinking with budget tokens
• Cost Tracking — Per-model token usage and pricing for Anthropic, OpenAI, and DeepSeek models
• Custom Tools — Implement the Tool trait to add your own tools
• Auto-Compaction — Multi-tier context compression (micro-compact, LLM summarization, image stripping)
• Sandbox Config — Network and filesystem restrictions for tool execution
• File State Cache — LRU cache for file state tracking and staleness detection

Quick Start

[dependencies]
open-agent-sdk = "0.1.0"
tokio = { version = "1", features = ["full"] }

use open_agent_sdk::{Agent, AgentOptions, SDKMessage};
use open_agent_sdk::types;

#[tokio::main]
async fn main() {
    let mut agent = Agent::new(AgentOptions::default()).await.unwrap();

    // Streaming
    let (mut rx, handle) = agent.query("What files are in this directory?").await;
    while let Some(event) = rx.recv().await {
        match event {
            SDKMessage::Assistant { message, .. } => {
                print!("{}", types::extract_text(&message));
            }
            SDKMessage::Result { text, cost_usd, .. } => {
                println!("\nDone (${:.4})", cost_usd);
            }
            _ => {}
        }
    }
    handle.await.unwrap();

    // Or use the blocking API
    let result = agent.prompt("Count lines in Cargo.toml").await.unwrap();
    println!("{}", result.text);

    agent.close().await;
}

Examples

#	Example	Description
01	Simple Query	Streaming query with tool calls
02	Multi-Tool	Glob + Bash multi-tool orchestration
03	Multi-Turn	Multi-turn conversation with session persistence
04	Prompt API	Blocking prompt() for one-shot queries
05	Custom System Prompt	Custom system prompt for code review
06	MCP Server	MCP server integration (stdio transport)
07	Custom Tools	Define and use custom tools
08	One-shot Query	Quick one-shot agent query
09	Subagents	Specialized subagent with restricted tools
10	Permissions	Read-only agent with allowed tools
11	Web Chat	Web-based chat UI with streaming

Run any example:

export CODEANY_BASE_URL=https://openrouter.ai/api
export CODEANY_API_KEY=your-api-key
export CODEANY_MODEL=anthropic/claude-sonnet-4
cargo run --example 01-simple-query

For the web chat UI:

cargo run --example web-chat
# Open http://localhost:8082

Custom Tools

Implement the Tool trait:

use async_trait::async_trait;
use open_agent_sdk::*;
use serde_json::{json, Value};
use std::collections::HashMap;
use std::sync::Arc;

struct MyTool;

#[async_trait]
impl Tool for MyTool {
    fn name(&self) -> &str { "MyTool" }
    fn description(&self) -> &str { "Does something useful" }
    fn input_schema(&self) -> ToolInputSchema {
        ToolInputSchema {
            schema_type: "object".to_string(),
            properties: HashMap::from([(
                "input".to_string(),
                json!({"type": "string", "description": "The input"}),
            )]),
            required: vec!["input".to_string()],
            additional_properties: Some(false),
        }
    }
    fn is_read_only(&self, _: &Value) -> bool { true }
    async fn call(&self, input: Value, _ctx: &ToolUseContext) -> Result<ToolResult, ToolError> {
        Ok(ToolResult::text("result"))
    }
}

// Use it
let agent = Agent::new(AgentOptions {
    custom_tools: vec![Arc::new(MyTool)],
    ..Default::default()
}).await.unwrap();

Session Persistence

use open_agent_sdk::session::*;

// Save current session
save_session(&session_data).await.unwrap();

// List all sessions
let sessions = list_sessions().await.unwrap();

// Resume a session
let data = load_session("session-id").await.unwrap();

// Fork a session
let new_id = fork_session("session-id").await.unwrap();

MCP Servers

use open_agent_sdk::types::McpServerConfig;

let agent = Agent::new(AgentOptions {
    mcp_servers: HashMap::from([(
        "filesystem".to_string(),
        McpServerConfig::Stdio {
            command: "npx".to_string(),
            args: vec!["-y".to_string(), "@modelcontextprotocol/server-filesystem".to_string(), "/tmp".to_string()],
            env: HashMap::new(),
        },
    )]),
    ..Default::default()
}).await.unwrap();

Built-in Tools

Tool	Description	Read-Only
Bash	Execute shell commands	No
Read	Read files with line numbers	Yes
Write	Create/overwrite files	No
Edit	String replacement in files	No
Glob	File pattern matching	Yes
Grep	Regex search (ripgrep)	Yes
NotebookEdit	Edit Jupyter notebook cells	No
WebFetch	Fetch URL content	Yes
WebSearch	Web search (pluggable)	Yes
AskUserQuestion	Interactive user prompts	No
SendMessage	Inter-agent messaging	No
TeamCreate/Delete	Multi-agent team management	No
EnterPlanMode/ExitPlanMode	Structured planning mode	No
EnterWorktree/ExitWorktree	Git worktree isolation	No
TodoWrite	Session todo list	No
TaskCreate/Get/List/Update/Stop/Output	Task tracking (6 tools)	Mixed
CronCreate/Delete/List	Scheduled task management	Mixed
Config	Session configuration	Mixed
LSP	Language Server Protocol operations	Yes
ListMcpResources/ReadMcpResource	MCP resource access	Yes
ToolSearch	Discover available tools	Yes

Multi-Provider Support

The SDK automatically detects which API format to use based on the model name:

Models	API Format	Auto-detected
Claude (sonnet, opus, haiku)	Anthropic Messages	Yes
GPT-4o, O1, O3, O4	OpenAI Chat Completions	Yes
DeepSeek, Qwen, Mistral	OpenAI Chat Completions	Yes
LLaMA, Gemma, Gemini, Yi, GLM	OpenAI Chat Completions	Yes

Override with CODEANY_API_TYPE=openai-completions or CODEANY_API_TYPE=anthropic-messages.

Works with any OpenAI-compatible endpoint (OpenRouter, vLLM, Ollama, LiteLLM, etc.):

export CODEANY_BASE_URL=https://openrouter.ai/api
export CODEANY_API_KEY=your-key
export CODEANY_MODEL=anthropic/claude-sonnet-4
cargo run --example 01-simple-query

Architecture

open-agent-sdk-rust/
├── src/
│   ├── agent/          # Agent loop, query engine, options
│   ├── api/            # Multi-provider API abstraction
│   │   ├── provider.rs # LLMProvider trait + auto-detection
│   │   ├── anthropic.rs# Anthropic Messages API (SSE streaming)
│   │   └── openai.rs   # OpenAI Chat Completions API (SSE streaming)
│   ├── types/          # Core types: Message, Tool, ContentBlock, MCP, Sandbox
│   ├── tools/          # 25+ built-in tool implementations + registry + executor
│   ├── mcp/            # MCP client (stdio, HTTP, SSE) + tool wrapping
│   ├── permissions/    # Permission rules, filesystem validation
│   ├── hooks/          # 20+ hook events with pre/post tool-use lifecycle
│   ├── costtracker/    # Token usage and cost tracking (Anthropic, OpenAI, DeepSeek)
│   ├── context/        # System/user context injection (git status, AGENT.md)
│   ├── session/        # Session persistence (save, load, fork, resume)
│   └── utils/          # Token estimation, retry, messages, compaction, file cache
├── tests/              # Comprehensive test suite (116 tests)
└── examples/           # 11 runnable examples + web chat UI

Configuration

Environment variables:

Variable	Description
CODEANY_API_KEY	API key (required)
CODEANY_MODEL	Default model (default: sonnet-4-6)
CODEANY_BASE_URL	API base URL override
CODEANY_API_TYPE	Force API format: anthropic-messages or openai-completions
CODEANY_CUSTOM_HEADERS	Custom headers (comma-separated key:value)
API_TIMEOUT_MS	API request timeout in ms
HTTPS_PROXY / HTTP_PROXY	Proxy URL

Links

• Website: codeany.ai
• TypeScript SDK: github.com/codeany-ai/open-agent-sdk-typescript
• Go SDK: github.com/codeany-ai/open-agent-sdk-go
• Issues: github.com/codeany-ai/open-agent-sdk-rust/issues

License

MIT