Nanocodex

Building blocks for frontier OpenAI agents.

Install · Agent API · Thesis · Components · VM-backed tools · Documentation

Install

Install the Nanocodex CLI on macOS or Linux:

curl -fsSL https://nanocodex.paradigm.xyz | bash

Or add the Rust SDK to an application:

cargo add nanocodex

Switch the installed CLI between builds:

nanocodex update                 # latest stable release
nanocodex update 0.2.0           # exact release, including downgrades
nanocodex update --nightly       # latest nightly
nanocodex update --pr 50         # verified on-demand PR artifact
nanocodex update --path ./nanocodex  # trusted local binary

Downloaded builds are retained under ~/.nanocodex/versions. Running nanocodex update 0.2.0 again switches to the cached binary without another download. A stable launcher keeps nanocodex update available even while an older binary is active, and ~/.nanocodex/current points to the selected version.

PR artifacts require an authenticated gh CLI and an already completed on-demand artifact workflow for that PR.

Minimal API Example

use nanocodex::{Nanocodex, OpenAi};

let openai = OpenAi::new(std::env::var("OPENAI_API_KEY")?)?;
let (agent, mut events) = Nanocodex::builder(openai)
    .instructions(
        "You are a Rust coding agent. Make focused changes, preserve unrelated work, \
         and run relevant tests before finishing.",
    )
    .workspace(std::env::current_dir()?)
    .build()?;

let event_task = tokio::spawn(async move {
    while let Some(event) = events.recv().await {
        eprintln!("event {}: {:?}", event.seq, event.kind);
        if event.kind.is_terminal() {
            break;
        }
    }
});

// Alternative: stream this turn's response as it arrives:
// use futures_util::StreamExt;
// use nanocodex::agent::events::{AgentEventData, AssistantEvent};
// let mut turn = agent.prompt("Find and fix the failing parser test.").await?;
// while let Some(event) = turn.next().await {
//     if let AgentEventData::Assistant(AssistantEvent::Delta(delta)) = event.data()? {
//         print!("{}", delta.text);
//     }
// }
let result = agent
    .prompt("Find and fix the failing parser test.")
    .await?
    .await?;

event_task.await?;
println!("{}", result.final_message());

The first await accepts and orders the prompt. The second waits for its typed TurnResult. Follow-on prompts automatically reuse the agent's retained history, WebSocket, tools, shell sessions, and prompt-cache identity. agent.clone() is a cheap handle to that same session; the independently returned AgentEvents stream is the session-wide event firehose.

Thesis

Small, excellent building blocks

Agent infrastructure is easier to understand and reuse when each piece has a sharp owner and a useful API of its own. An OpenAI client should work without an agent loop. Tools should work without a CLI. The high-level agent should compose those pieces rather than hide another implementation of them.

Nanocodex makes a small number of deliberate choices—Rust, Tower, typed protocols, owned lifecycle state, and builder APIs—then keeps the boundaries boring.

The model and harness are co-designed

We do not try to outsmart behavior that frontier models and Codex already make explicit. Context management, AGENTS.md, compaction, cache identity, tool shapes, continuation, reconnect replay, cancellation, and process cleanup are parts of the model-facing contract.

Nanocodex carries those invariants into a smaller, library-first API while leaving application policy with the caller.

Evidence over intuition

Representative cargo bench workloads, OpenTelemetry traces, differential tests, and end-to-end evals keep the harness honest. The goal is simple: normal agent turns should be model- and network-latency bound, with token usage and estimated USD cost visible at the same typed boundary as the result.

Components

nanocodex                         Alloy-style facade and prelude
├── agent                         nanocodex-agent
│   ├── oai                       nanocodex-oai-api
│   └── tools                     nanocodex-tools
│       └── macros                nanocodex-tools-macros
├── oai                           nanocodex-oai-api
├── tools                         nanocodex-tools
└── observability                 nanocodex-observability (optional)

The facade provides the canonical common imports. Each lower crate is also designed to be useful directly, without importing the higher orchestration layer.

nanocodex

The thin facade reexports the golden agent path at the crate root and keeps detailed APIs under nanocodex::agent, nanocodex::oai, and nanocodex::tools. Its prelude contains only the common types needed to build an agent.

Facade guide · API documentation

nanocodex-agent

The batteries-included lifecycle: an owned private driver, a cheap cloneable Nanocodex handle, typed Turn and TurnResult values, and an optional event stream. It owns prompt ordering, the tool loop, AGENTS.md discovery, compaction timing, cancellation, snapshots, and branching through spawn, fork, and fork_from.

Callers never pass previous messages, response IDs, or tool results back into the agent.

Agent guide · API documentation

nanocodex-oai-api

The complete OpenAI boundary: API-key and ChatGPT authentication, typed Responses protocol values, a persistent WebSocket transport, client-owned context, continuation and replay, automatic pricing, and a generic Tower client.

Its standalone OpenAi -> Session -> ResponseTurn -> Response path provides a managed conversation without taking on agent policy. Custom Tower layers and services remain concrete and nameable—no boxing or global client is required.

OpenAI API guide · API documentation

nanocodex-tools

The model-facing tool runtime: the Tool contract, heterogeneous Tools registry, standard workspace tools, shell and process lifecycle, Code Mode, deferred tool_search, remote dispatch, and MCP. MCP is always available on native targets.

Applications can implement Tool directly or use the reexported #[tool] macro. The separate nanocodex-tools-macros package exists only for Rust's procedural-macro boundary.

Tools guide · API documentation

nanocodex-observability

Application-owned tracing and OpenTelemetry setup for the data already flowing through the agent. It provides structured lifecycle, model, tool, usage, cost, cache, and latency telemetry without changing the core runtime path.

Enable the facade's observability feature or depend on the component directly.

Observability guide · API documentation

Experimental systems components

VM components live under crates/experimental/ while their public contracts mature:

Package	Responsibility
nanocodex-vm	VM lifecycle and images plus retained guest-backed workspace tools

The CLI is a consumer of this crate. VM-backed tools remain opt-in for normal agent sessions.

CLI and language bindings

The CLI/TUI, Python package, Node/browser package, React bindings, and examples are thin consumers of the same owned session API. They do not define a second agent protocol.

Examples · JavaScript · Python · Web

VM-backed tools

Normal TUI and one-shot sessions keep host workspace tools by default. They can instead route exec_command, write_stdin, apply_patch, and view_image through one retained VM:

just build-vm-guest
nanocodex \
  --vm .nanocodex/vm/session-rootfs.ext4 \
  --vm-guest-runtime target/aarch64-unknown-linux-musl/debug/nanocodex-vm-guest \
  --vm-workspace /app
nanocodex run "inspect the repository" \
  --vm .nanocodex/vm/session-rootfs.ext4 \
  --vm-guest-runtime target/aarch64-unknown-linux-musl/debug/nanocodex-vm-guest \
  --vm-workspace /app

Directory roots may instead contain /usr/local/bin/nanocodex-vm-guest. See the VM guide for image preparation, lifecycle, egress, Linux requirements, and macOS signing.

Documentation

• Facade API
• Migration from 0.2.x
• Examples
• Benchmarks and retained measurements
• VM-backed tools and egress

License

Licensed under either of:

• Apache License, Version 2.0
• MIT License

at your option.