Google Antigravity Rust SDK

Recording_2026-05-21_20-07-01_optimized.mp4

The Google Antigravity SDK is a Rust library for building AI agents powered by Antigravity and Gemini. It provides a secure, scalable, and stateful infrastructure layer that abstracts the agentic loop, letting you focus on what your agent does rather than how it runs.

Installation

Add the SDK and tokio to your project:

cargo add antigravity-sdk-rust
cargo add tokio --features full

Obtain the localharness binary: The SDK relies on a compiled native Go runtime binary (localharness) to orchestrate agent operations. You have two options to install it:
- Option A: Without Python/pip (Recommended for Rust-only environments & web servers) Run the helper installer script to download and extract the binary directly from PyPI (wheels are standard ZIP files):
```
./scripts/install_harness.sh
export ANTIGRAVITY_HARNESS_PATH="$(pwd)/bin/localharness"
```
- Option B: Using Python/pip If Python is already installed on your development machine, simply run:
```
pip install google-antigravity
```
  The Rust SDK will automatically locate the binary inside the Python package installation directory fallback.
⚠️ Platform Support Note: The upstream google-antigravity package on PyPI currently provides wheels for:
- macOS Apple Silicon (arm64) ✅
- Linux x86_64 ✅
- Linux aarch64 ✅
The following platforms are not supported — no wheels are published:
- Intel (x86_64) macOS ❌
- Windows (x86_64 and ARM64) ❌
If you are on an unsupported platform, use a Linux VM/container or an Apple Silicon Mac instead.

Quickstart

Get started by setting your API key and running the hello_world example:

export GEMINI_API_KEY="your_api_key_here"
cargo run --example hello_world

Concepts

Simple Agent

The Agent struct manages the full lifecycle — binary discovery, tool wiring, hook registration, and policy defaults.

use antigravity_sdk_rust::agent::Agent;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    // Configures and constructs the Agent using the builder pattern.
    // PhantomData guarantees compile-time verification of safety policies.
    let agent = Agent::builder()
        .allow_all()
        .build();

    // Spawns the harness session and transitions the Agent state to Started.
    let agent = agent.start().await?;

    let response = agent.chat("Say 'Hello World!'").await?;
    println!("Agent: {}", response.text);

    agent.stop().await?;
    Ok(())
}

Advanced Usage with Conversation

For full control over the connection lifecycle, use Conversation with a ConnectionStrategy directly. Conversation is a stateful session that accumulates step history:

use antigravity_sdk_rust::agent::AgentConfig;
use antigravity_sdk_rust::connection::AnyConnection;
use antigravity_sdk_rust::conversation::Conversation;
use antigravity_sdk_rust::local::LocalConnectionStrategy;
use antigravity_sdk_rust::tools::ToolRunner;
use antigravity_sdk_rust::types::GeminiConfig;
use std::sync::Arc;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    let tool_runner = ToolRunner::new();
    let strategy = LocalConnectionStrategy::new(
        "localharness".to_string(), // path to harness
        GeminiConfig {
            enable_google_search: Some(true),
            enable_url_context: Some(true),
            ..Default::default()
        },
        Default::default(),
        None,
        None,
        vec![],
        vec![],
        Some(tool_runner),
        None,
        "my_conversation_id".to_string(),
        vec![], // MCP servers
    );

    let connection = strategy.connect().await?;
    let conversation = Conversation::new(AnyConnection::Local(Arc::new(connection)), None);

    let response = conversation.chat_to_completion("What files are here?").await?;
    println!("Agent: {}", response.text);

    Ok(())
}

Features

Custom Tools

use antigravity_sdk_rust::agent::{Agent, AgentConfig};
use antigravity_sdk_rust::tools::Tool;
use serde_json::Value;

struct WeatherTool;

impl Tool for WeatherTool {
    fn name(&self) -> &str {
        "get_weather"
    }

    fn description(&self) -> &str {
        "Get the current weather for a city."
    }

    fn parameters_json_schema(&self) -> &str {
        r#"{
            "type": "object",
            "properties": {
                "city": {
                    "type": "string"
                }
            },
            "required": ["city"]
        }"#
    }

    async fn call(&self, args: Value) -> Result<Value, anyhow::Error> {
        let city = args.get("city").and_then(|c| c.as_str()).unwrap_or("Tokyo");
        Ok(serde_json::json!({ "weather": format!("It's sunny in {}", city) }))
    }
}

Hooks and Policies

Control agent behavior with a declarative policy system:

use antigravity_sdk_rust::policy::{self, Policy};

let policies = vec![
    policy::deny_all(),                          // Block all tools by default
    policy::allow("VIEW_FILE"),                  // Allow reading/viewing files
];

Error Handling

The SDK provides a typed error hierarchy via AntigravityError:

use antigravity_sdk_rust::error::AntigravityError;

// Three error categories:
// - AntigravityError::Connection(msg) — network/transport failures
// - AntigravityError::Execution(msg) — agent execution failures  
// - AntigravityError::Validation { message, errors } — input validation failures

Multimodal Content

Send images, documents, audio, and video to the agent:

use antigravity_sdk_rust::types::{Content, Media, MimeType, ImageMime};

// Text-only (backwards compatible)
let response = agent.chat("What is 2+2?").await?;

// From file (auto-detects MIME type from extension)
let content = Content::from_file("photo.jpg", Some("Describe this")).unwrap();

// From raw bytes
let media = Media {
    data: vec![0xFF, 0xD8, 0xFF],
    mime_type: MimeType::Image(ImageMime::Jpeg),
    description: Some("A photo".to_string()),
};
let content = Content::media(media);

Supported formats: BMP, JPEG, PNG, WebP (images), PDF, JSON, CSS, CSV, HTML, JS, TXT, RTF, XML (documents), WAV, MP3, AAC, OGG, FLAC, Opus, MPEG, M4A, L16 (audio), 3GPP, AVI, MP4, MPEG, MOV, WebM, WMV, FLV (video).

Lifecycle Hooks

The full hook lifecycle is available:

use antigravity_sdk_rust::hooks::Hook;
use antigravity_sdk_rust::types::{HookResult, ToolCall, ToolResult, ChatResponse};

struct MyHook;

impl Hook for MyHook {
    // Session lifecycle
    async fn on_session_start(&self) -> Result<(), anyhow::Error> { Ok(()) }
    async fn on_session_end(&self) -> Result<(), anyhow::Error> { Ok(()) }
    
    // Turn lifecycle
    async fn pre_turn(&self) -> Result<HookResult, anyhow::Error> {
        Ok(HookResult { allow: true, message: String::new() })
    }
    async fn post_turn(&self, _response: &ChatResponse) -> Result<(), anyhow::Error> { Ok(()) }
    
    // Tool lifecycle
    async fn pre_tool_call(&self, _call: &ToolCall) -> Result<HookResult, anyhow::Error> {
        Ok(HookResult { allow: true, message: String::new() })
    }
    async fn post_tool_call(&self, _result: &ToolResult) -> Result<(), anyhow::Error> { Ok(()) }
    
    // History compaction
    async fn on_compaction(&self, _summary: &str) -> Result<(), anyhow::Error> { Ok(()) }
}

Hook Context (Hierarchical State)

Hooks can share state across lifecycle events via a parent-chaining key-value store:

use antigravity_sdk_rust::context::HookContext;
use std::sync::Arc;

// Session context (root)
let session = Arc::new(HookContext::new());
session.set("user_id", "u-123");

// Turn context (inherits session)
let turn = Arc::new(HookContext::child(session));
turn.set("turn_count", 1i32);

// get() walks up the chain:
assert_eq!(turn.get::<String>("user_id"), Some("u-123".to_string()));

Context-Aware Tools

Tools can opt-in to receiving a ToolContext for session state and agent communication:

use antigravity_sdk_rust::tools::Tool;
use antigravity_sdk_rust::tool_context::ToolContext;
use serde_json::Value;

struct StatefulTool;

impl Tool for StatefulTool {
    fn name(&self) -> &str { "stateful_tool" }
    fn description(&self) -> &str { "A tool with session state" }
    fn parameters_json_schema(&self) -> &str { r#"{"type":"object"}"# }

    fn needs_context(&self) -> bool { true } // Opt-in

    async fn call(&self, args: Value) -> Result<Value, anyhow::Error> {
        Ok(Value::Null) // Fallback
    }

    async fn call_with_context(
        &self,
        args: Value,
        ctx: &ToolContext,
    ) -> Result<Value, anyhow::Error> {
        // Access session state
        let count: i32 = ctx.get_state("call_count").unwrap_or(0);
        ctx.set_state("call_count", count + 1);
        Ok(serde_json::json!({ "calls": count + 1 }))
    }
}

Trigger Helpers

Convenience factories for common trigger patterns:

use antigravity_sdk_rust::trigger_helpers::every;
use std::time::Duration;

// Periodic trigger — fires every 30 seconds
let heartbeat = every(Duration::from_secs(30), "check_status");

Interactive Loop

Built-in REPL for conversational agents:

use antigravity_sdk_rust::agent::Agent;
use antigravity_sdk_rust::interactive::run_interactive_loop;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    let agent = Agent::builder().allow_all().build().start().await?;
    run_interactive_loop(&agent).await?;
    agent.stop().await?;
    Ok(())
}

MCP Integration

Connect to external MCP servers and expose their tools to the agent:

use antigravity_sdk_rust::agent::Agent;
use antigravity_sdk_rust::types::McpServerConfig;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    let agent = Agent::builder()
        .mcp_server(McpServerConfig::Stdio {
            name: "my_server".to_string(),
            command: "npx".to_string(),
            args: vec!["my-mcp-server".to_string()],
            enabled_tools: None,
            disabled_tools: None,
        })
        .allow_all()
        .build();

    let agent = agent.start().await?;
    let response = agent.chat("Use the MCP tools to help me.").await?;
    println!("{}", response.text);
    agent.stop().await?;
    Ok(())
}

Three transport types are supported:

McpServerConfig::Stdio — launch a local subprocess (e.g., npx, uvx)
McpServerConfig::Sse — connect via Server-Sent Events
McpServerConfig::Http — connect via standard HTTP with configurable timeouts

Each variant supports enabled_tools / disabled_tools for fine-grained tool filtering.

Sugared Thoughts & Tool Call Streams (Advanced)

For more complex use cases, stream internal model reasoning/thinking and intercept tool call dispatches in real-time using StreamChunk:

use antigravity_sdk_rust::agent::Agent;
use antigravity_sdk_rust::types::StreamChunk;
use futures_util::StreamExt;

#[tokio::main]
async fn main() -> Result<(), anyhow::Error> {
    let agent = Agent::builder().allow_all().build().start().await?;
    let conversation = agent.conversation();
    let mut stream = conversation.chat("Explain quantum computing").await?;

    while let Some(chunk_res) = stream.next().await {
        match chunk_res? {
            // 1. Stream reasoning/thinking deltas
            StreamChunk::Thought { text, .. } => {
                eprint!("💭 {}", text); // show thinking in grey/stderr
            }
            // 2. Stream response text tokens
            StreamChunk::Text { text, .. } => {
                print!("{}", text);
            }
            // 3. Stream strongly-typed ToolCall events
            StreamChunk::ToolCall(call) => {
                println!("\n🔧 Executing: {} (args: {})", call.name, call.args);
            }
        }
    }
    agent.stop().await?;
    Ok(())
}

Google Search Grounding & Web Search Fallback

The SDK supports server-side Google Search grounding and provides a client-side search fallback:

Google Search Grounding: Enable Gemini's native Google Search grounding tool by setting enable_google_search: Some(true) in GeminiConfig. This enables the model to natively perform search queries server-side to return up-to-date online information.
Web Search Fallback: If the model decides to invoke a tool call named google_search or web_search and no custom search tool has been registered with ToolRunner, the SDK automatically runs a built-in search fallback. On native platforms, it spawns a python3 subprocess to scrape and parse DuckDuckGo search results. On WASM platforms, it returns an empty result block indicating search is not available.

Client-Side Tool Step Updates

When custom client-side tools are executed, the SDK connection dynamically generates and streams synthetic Step updates:

Enters ACTIVE state before executing the tool, allowing the user interface to render an active tool execution card.
Emits DONE (on success) or ERROR (on failure) once execution completes, displaying the results/error on the timeline.
To prevent collision with step indices assigned by the harness, client-side tool steps use synthetic indices starting at 50,000.

Web Integration

The SDK provides two patterns for building web applications with AI agents:

Leptos + Axum (Native)

For standard web servers (VPS, Docker, bare metal). The Agent runs in-process with full SDK features.

cd examples/leptos_axum
echo "GEMINI_API_KEY=your-key" > .env
cargo leptos serve
# Open http://localhost:3000

Leptos + Spin/WASI (Edge)

For edge/serverless deployments on Spin (formerly Fermyon Spin, now under Akamai). Since Spin components cannot make outbound TCP/WebSocket connections directly, this target runs in Sidecar Mode, where the component communicates via HTTP with a native runner process (agent_server):

# Terminal 1: Start the agent sidecar
cd examples/agent_server
GEMINI_API_KEY=your-key cargo run

# Terminal 2: Start Spin
cd examples/leptos_ssr_axum
spin build --up
# Open http://localhost:3000

See examples/README.md for detailed architecture diagrams and configuration options.

WebAssembly (WASM) & Edge Compilation

The SDK supports compiling directly to the wasm32-wasip1 WebAssembly target. This enables running agents inside sandboxed Wasm runtimes (such as Spin, Wasmtime, or Wasmer) that support WASI network sockets.

Wasm Connection Architecture

In standard native environments, the SDK spawns the localharness binary as a local subprocess. Since process spawning is not supported inside WebAssembly sandboxes, when targeting WASM, the SDK switches to Direct Network Connection Mode via WasmConnectionStrategy and WasmConnection:

Host Server: A host-side localharness WebSocket server is run on the machine/VM (configured via ANTIGRAVITY_HARNESS_HOST and ANTIGRAVITY_HARNESS_PORT).
WebSocket Handshake: The WasmConnectionStrategy opens a TCP socket to the harness server, initiates a WebSocket client handshake with the Gemini API key passed via the x-goog-api-key header, and upgrades it to a bi-directional stream.
Session Handshake: The client sends an InitializeConversationEvent containing the HarnessConfig (tools, workspaces, and system instructions) to start the stateful agent trajectory.
Asynchronous Event Loop: Two asynchronous tasks are spawned under the WASM event loop:
- Reader Loop: Continuously reads WebSocket frames, parses incoming OutputEvent messages (including StepUpdate and TrajectoryStateUpdate), maps them to SDK Step types, dispatches lifecycle hooks, and routes tool calls.
- Sender Loop: Buffers and sends outgoing InputEvent messages (user messages, tool responses, question replies, etc.) back to the harness.

Running the WASM Mock Test Suite

The mock and unit test suite in src/wasm.rs validates WASM-specific functionality (connection lifecycle, event loops, tool call/result extraction, and idle state transitions). Since it uses a standard WebSocket framework, you can run the suite natively on your host machine without a full WebAssembly runner:

# Run all unit tests including the WASM mock connection tests
cargo test wasm::tests

This mock test suite programmatically binds a local WebSocket server to a dynamically allocated free port, completes the initialization handshake, feeds mock trajectory state updates/step updates, and asserts that WasmConnection correctly receives messages, invokes callback hooks, and cleanly terminates the stream upon transitioning to the idle state.

Rust 2024 and Native Async Traits

The SDK has been fully refactored to use native async traits (stable since Rust 1.75 / Rust 2024), completely removing the dependency on the #[async_trait] macro.

Native Async Traits: Custom implementations of Connection, Hook, Tool, and Trigger now use standard async function definitions returning impl Future<Output = ...> + Send where necessary to maintain compile-time thread safety bounds.
Dynamic Dispatch via Blanket Impls: Because native async traits are not directly object-safe (dyn Trait compatible) without manual workarounds, the SDK defines companion traits DynConnection, DynHook, DynTool, and DynTrigger which are object-safe and automatically implemented via blanket implementations for any type implementing the base trait. This allows clean, zero-overhead dynamic dispatch (e.g. Arc<dyn DynHook>).

Local Development

This project uses just to manage development tasks.

Help / List Commands: List all available just recipes.
```
just
# or
just help
```

Run SDK Examples: Start any of the SDK examples by directory or file name (handles both file and folder examples, converting dashes to underscores automatically).

# Run the hello_world.rs console example
just example hello_world

# Run the agent_server HTTP sidecar example
just example agent_server

# Run the leptos_ssr_axum edge web example
just example leptos_ssr_axum

Check Code Quality: Run all style, lint, and test checks.
```
just check
```
Install Local Harness: Download and configure the required localharness binary.
```
just install
```
Bump version & Release tag: Bump the package version, update Cargo.lock, commit using --no-verify (skipping git hooks), and tag the release.
```
# Auto-bump patch version (e.g., 0.1.0 -> 0.1.1)
just version

# Or force/override with a specific version
just version 0.2.0
```
Publish to Crates.io: Manually publish the package to crates.io (runs just check first).
```
just publish
```

Component Documentation

For more detailed documentation on specific components, see:

Agent — High-level, batteries-included entry point.
Connections — Transport and backend abstraction.
Conversation — Stateful session management.
Hooks — Agent lifecycle interception and policies.
MCP — Model Context Protocol integration.
Tools — In-process tool execution.
Triggers — Background tasks and external events.

Architecture

For more information, see ARCHITECTURE.md.

License

This project is licensed under the MIT License.

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Google Antigravity Rust SDK

Installation

Quickstart

Concepts

Simple Agent

Advanced Usage with Conversation

Features

Custom Tools

Hooks and Policies

Error Handling

Multimodal Content

Lifecycle Hooks

Hook Context (Hierarchical State)

Context-Aware Tools

Trigger Helpers

Interactive Loop

MCP Integration

Sugared Thoughts & Tool Call Streams (Advanced)

Google Search Grounding & Web Search Fallback

Client-Side Tool Step Updates

Web Integration

Leptos + Axum (Native)

Leptos + Spin/WASI (Edge)

WebAssembly (WASM) & Edge Compilation

Wasm Connection Architecture

Running the WASM Mock Test Suite

Rust 2024 and Native Async Traits

Local Development

Component Documentation

Architecture

License

FilesExpand file tree

README.md

Latest commit

History

README.md

File metadata and controls

Google Antigravity Rust SDK

Installation

Quickstart

Concepts

Simple Agent

Advanced Usage with Conversation

Features

Custom Tools

Hooks and Policies

Error Handling

Multimodal Content

Lifecycle Hooks

Hook Context (Hierarchical State)

Context-Aware Tools

Trigger Helpers

Interactive Loop

MCP Integration

Sugared Thoughts & Tool Call Streams (Advanced)

Google Search Grounding & Web Search Fallback

Client-Side Tool Step Updates

Web Integration

Leptos + Axum (Native)

Leptos + Spin/WASI (Edge)

WebAssembly (WASM) & Edge Compilation

Wasm Connection Architecture

Running the WASM Mock Test Suite

Rust 2024 and Native Async Traits

Local Development

Component Documentation

Architecture

License