Cersei

Cersei

The complete Rust SDK for building coding agents.

Cersei gives you every building block of a production coding agent — tool execution, LLM streaming, sub-agent orchestration, persistent memory, skills, MCP integration — as composable library functions. Build a Claude Code replacement, embed an agent in your app, or create something entirely new.

use cersei::prelude::*;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let output = Agent::builder()
        .provider(Anthropic::from_env()?)
        .tools(cersei::tools::coding())
        .permission_policy(AllowAll)
        .run_with("Fix the failing tests in src/")
        .await?;

    println!("{}", output.text());
    Ok(())
}

**MIT License** | Built by [Adib Mohsin](https://github.com/pacifio) | [Docs](https://cersei.pacifio.dev/docs) | [GitHub](https://github.com/pacifio/cersei)

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Why Cersei

	Claude Code	OpenCode	Cersei SDK	Abstract CLI
Form factor	CLI app	CLI app	Library	CLI app
Embeddable	No	No	Yes	No (uses SDK)
Provider	Anthropic only	Multi-provider	Multi-provider	Multi-provider
Language	TypeScript	TypeScript	Rust	Rust
Custom tools	Plugins	Plugins	impl Tool / #[derive(Tool)]	Via SDK
Startup	~269ms	~300ms	N/A (library)	~34ms
Binary / RSS	174MB / 330MB	—	N/A	5.8MB / 4.9MB
Memory	File-based	SQLite	File + Graph	File + Graph
Skills	.claude/commands/	.claude/skills/	Both formats	Both formats

Cersei is built from the architecture of Claude Code (reverse-engineered Rust port) and designed so that anyone can build a complete, drop-in replacement for Claude Code, OpenCode, or any coding agent — as a library call.

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Abstract — The CLI

**Abstract** is a complete CLI coding agent built on Cersei. One binary, zero runtime dependencies, graph memory by default.

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