Astrid

A portable, capability-secure operating system for composable software.


Astrid treats a component the way an operating system treats a process. Every
ability is a sealed WebAssembly capsule: it can be composed with other
capsules, granted only explicit authority, and replaced without expanding its
reach. Astrid is independent of any particular product, model provider, agent
loop, user interface, or distribution.

The kernel underneath is small and deliberately dumb. It routes events,
enforces capabilities, runs the sandbox, and records the audit trail; it holds
no model, tool schema, or business logic. A jailbreak, poisoned tool, or plain
bug still cannot read a file, reach a network, or spawn a process outside its
grant. Authority is a capability the kernel enforces, not an instruction the
model is trusted to follow.

Quick start

brew tap astrid-runtime/tap && brew install astrid
astrid init --distro @yourorg/your-distro
astrid start
astrid status
astrid capsule list

Astrid Runtime does not select or bundle a product distro. Choose a distro you
trust and pass its name, repository, local Distro.toml, or signed .shuttle
archive explicitly with --distro. Operators running an uncomposed runtime can
skip init and start the daemon directly.

Start with the Book for the
architecture or the Contributor Handbook
to contribute.

Why Astrid exists

Agent frameworks put trust in the prompt. Astrid puts it in the runtime. An agent is untrusted code
executing on your machine with access to your files, your network, and your credentials. Telling it
to behave is not a security boundary. An OS-grade boundary is.

• Cryptographic capability model. Every file path, network host, and tool is a signed ed25519

grant scoped to a resource pattern, principal-bound, expiry-checked, and globally revocable. No
grant, no access.

• WASM sandbox with no ambient authority. Capsules run in Wasmtime with no syscalls, no file

descriptors, and no host memory. Every external effect is a capability-checked host call over a
WIT-typed ABI.

• The kernel is dumb. It instantiates an event bus, loads capsules, and routes IPC bytes under a

capability ACL. It has no LLM handles, no conversation state, and no tool registry. All
intelligence lives in capsules, so a capsule bug cannot corrupt shared kernel state.

• Per-principal everything. Each identity gets isolated capsule access, KV data, secrets, home

directory, quotas, and audit chain. One principal can never read another's namespace, and it fails
closed if the caller cannot be resolved.

• Signed, hash-linked audit chain. Each entry seals the hash of the one before it and is signed.

Break the chain and the tampering shows.

• Live capsule lifecycle. Install, upgrade, and remove capsules on a running daemon. No restart.

How it works

Frontends (the CLI, the HTTP gateway, Discord, and so on) are uplinks: protocol clients that
connect to the daemon over a Unix domain socket and speak in IPC events. There is no Frontend
trait. An uplink publishes events and receives responses like any other bus participant.

flowchart TB
    CLI[CLI] -->|IPC events over Unix socket| Kernel
    HTTP[HTTP gateway] -->|IPC events| Kernel
    Discord[Discord] -->|IPC events| Kernel
    Uplinks[Other uplinks] -->|IPC events| Kernel

    subgraph Runtime[Astrid]
        Kernel[Kernel: astrid-daemon<br/>dumb event router<br/>event bus - capability ACL - audit chain - Wasmtime sandbox]
        Capsules[WASM Component capsules: wasm32-unknown-unknown<br/>providers - orchestrators - tools - fs - http - sessions - registry - identity]
    end

    Kernel -->|capability-checked host calls<br/>astrid:* WIT ABI| Capsules

Capsules communicate exclusively through the bus. Each declares what it needs and what it provides
in a Capsule.toml manifest with typed [imports]/[exports] tables; the kernel resolves the
dependency graph by topological sort and boots capsules in order. Tools are an IPC convention, not a
kernel concept: a tool capsule intercepts tool.v1.execute., and the kernel never sees a tool
schema.

The host ABI is the WebAssembly component model with versioned astrid:* WIT packages:
fs, io, kv, ipc, net, http, sys, process, approval, identity, elicit, and
uplink. Guests import only what their manifest allows, and every call is capability-gated at the
boundary.

The security model

Astrid's security is decomposed. There is no single gate every action funnels through. A capsule has
no ambient authority, and authorization is enforced by independent, per-area mechanisms, each
fail-closed and each enforced where the effect actually happens.

flowchart TB
    Action[A capsule action] --> Sandbox[WASM sandbox<br/>no syscalls, file descriptors, or host memory<br/>external resources are capability-checked host calls]
    Action --> Manifest[Manifest gate<br/>declared file, network, and process allow-list<br/>empty is deny-all; path traversal and SSRF defenses]
    Action --> IPC[IPC ACL<br/>declared publish and subscribe topics only<br/>per-principal routing]
    Action --> Capability[Capability token<br/>ed25519, principal-bound, scoped, expiring, revocable<br/>per-device tokens can be subset-scoped]
    Action --> Approval[Approval gate<br/>once - session - always - deny<br/>allow always mints a token; local egress elicits consent]
    Action --> OS[OS sandbox<br/>bwrap on Linux - seatbelt on macOS for native subprocesses]
    Action --> Audit[Audit chain<br/>signed, hash-linked JSONL decisions and calls<br/>split per principal and independently verifiable]

These mechanisms are real and independently tested. There is no unified interceptor orchestrating
them. The five-layer gate chapter of The Astrid Book walks
each layer against the source.

Install

Homebrew (macOS and Linux):

brew tap astrid-runtime/tap
brew install astrid

From crates.io (requires Rust 1.95+):

cargo install astrid

From source:

git clone https://github.com/astrid-runtime/astrid
cd astrid && cargo build --release   # binary at ./target/release/astrid

Astrid installs four binaries that work together. You only ever invoke astrid; it starts and
manages the rest.

| Binary | Role |
|---|---|
| astrid | CLI uplink. Connects to the daemon over the Unix socket. TUI, headless mode, capsule and agent management. |
| astrid-daemon | The kernel process. Loads capsules, routes IPC, enforces capabilities, runs the sandbox. |
| astrid-build | Capsule compiler and packager. Builds to wasm32-unknown-unknown. |
| astrid-emit | Stdio-to-bus bridge for external hook producers. |

Initial setup

astrid init --distro fetches a distro (a curated capsule bundle), presents any selection
groups declared by that distro, and prompts for its required configuration. Secrets are stored per
principal in the secret store, never passed on the command line. init writes a Distro.lock
pinning every capsule by BLAKE3 hash, so the same explicit distro input reproduces the same fleet.

astrid init --distro @yourorg/your-distro          # repository distro
astrid init --distro ./Distro.toml                  # local manifest
astrid init --distro ./bundle.shuttle --offline     # signed bundle, no network
astrid init --distro @yourorg/your-distro --yes     # non-interactive defaults

When a distro includes an LLM provider, onboarding can discover that provider's live model list from
its /v1/models endpoint. If the distro also includes an agent loop, confirm that it is ready before
starting a session:

astrid doctor    # daemon up? capsules ready? an LLM available?
astrid chat      # interactive session; the daemon auto-starts on first use
astrid models    # list the current provider's models (a registry-capsule verb)

Headless and scripting

astrid -p "summarize the git log"                    # single prompt, prints and exits
git diff HEAD~1 | astrid -p "write a commit message" # stdin is appended to the prompt
astrid -p "fix all failing tests" --yes              # auto-approve tool requests
astrid -p "continue" --session "$SID"                # resume by id or name

Daemon lifecycle

astrid start     # persistent daemon (survives terminal close)
astrid status    # PID, uptime, connected clients, loaded capsules
astrid ps        # loaded capsules and their lifecycle state
astrid stop      # graceful shutdown
astrid update    # authenticate, verify, and install the latest release

Per-principal isolation

Each principal (agent identity) is a fully isolated tenant: its own capsule access, KV namespace,
secrets, home directory, quotas, and audit chain. New principals inherit nothing by default.

astrid agent create ci-bot                     # clean-slate, least-privilege agent
astrid agent create staging --clone production # full profile + state replica
astrid agent modify ci-bot 
  --add-capsule astrid-capsule-fs              # grant access to a capsule's tools
astrid caps show ci-bot                        # inspect capability grants
astrid quota set -a ci-bot --memory 128MB      # per-principal resource limits
astrid pair-device issue --scope use-only      # scope a device token to a subset

Capsule access is enforced kernel-side at dispatch. A principal can only invoke capsules explicitly
granted to it, and two principals installing the same capsule bytes share one content-addressed
on-disk artifact while getting separate in-memory runtime instances.

Write a capsule

A capsule is a WASM process described by a manifest. The scaffold generates a first-try-compiling
project targeting wasm32-unknown-unknown, plus an AUTHORING.md guide.

astrid capsule new my-capsule    # scaffold Capsule.toml, Cargo.toml, src/lib.rs, .cargo/config.toml
cd my-capsule
astrid capsule build             # compile and package
astrid capsule install .         # hot-loaded into the running daemon, no restart

Capsule authors depend on <code class="ra0-md-code">astrid-sdk</code>, which mirrors
the std module layout (fs, net, process, env, time, log) and adds Astrid modules
(ipc, kv, http, hooks, uplink, identity, approval). The #[capsule] proc macro
generates the WASM ABI boilerplate: exports, serialization, and dispatch for tools, commands, hooks,
and lifecycle entry points.

use astrid_sdk::prelude::*;

#[derive(Default)]
struct Weather;

#[capsule]
impl Weather {
    #[astrid::tool]
    fn forecast(&self, args: ForecastArgs) -> Result<Forecast, SysError> {
        let key = env::var("WEATHER_API_KEY")?;
        let body = http::get(&format!("https://api.example.com/wx?q={}", args.city))?;
        Ok(serde_json::from_slice(&body)?)
    }
}

Building capsules is a first-class workflow in Astrid. The Forge (astrid capsule new plus authoring
tools and runtime-served guidance) is the on-ramp; the direction is an agent that writes, builds, and
installs its own capsules within the capability sandbox.

Reproducible builds and deterministic tests are consumers of
Muninn's verified computation memory: complete source and toolchain
closures become derivation inputs, so an unchanged fleet build is a verified lookup while install,
signing, and publication remain fresh authorized effects.

Live capsule lifecycle

astrid capsule install @org/capsule-name   # install and hot-load
astrid capsule update my-capsule           # hot-swap the running instance
astrid capsule remove my-capsule           # live-unload, no restart
astrid capsule list --verbose              # installed capsules with capability metadata
astrid capsule tree                        # imports/exports dependency graph

What's new in 0.9

Five bodies of work plus a security-hardening pass. See CHANGELOG.md for the full
list.

• Live capsule lifecycle. Hot-load on install, hot-swap on upgrade, live-unload on remove, all

without a daemon restart.

• Per-principal isolation, hardened end-to-end. Principal-view-aware capsule loading with

content-addressed artifact reuse, kernel-side tool-surface access enforcement, and per-device
capability scope threaded through the HTTP gateway.

• LLM provider and model binding. Multi-provider onboarding with live model discovery, plus

gateway routes and astrid models / astrid doctor for per-principal model management and
loop-readiness checks.

• Conversation threads over the HTTP gateway. List, fetch, update, delete, and full-text search

threads, plus a per-principal live conversation feed with cross-principal isolation enforced at the
bus.

• astrid:http@1.1.0 and operator-configurable limits. Per-request timeouts, redirect policy,

body caps, https-only, and subresource integrity; seven previously-hardcoded ceilings become
operator knobs.

• Security. Local-egress consent (transport-origin marker, runtime elicitation, per-capsule and

per-principal grants), an SSRF airlock that closes IP-literal and redirect bypasses, and a hardened
supply-chain path (Sigstore attestation, CodeQL, pinned Action SHAs, least-privilege tokens).

Documentation

• The Astrid Book is the canonical reference: the

kernel, the capsule model, the host ABI, the bus, and the security model, grounded in the source
with file and line anchors. Start with Getting Started
to go from nothing to a working agent in a few minutes.

• Operator guides live in <code class="ra0-md-code">docs/</code>: the unified config schema,

LLM model selection, distro signing, the
gateway deployment runbook, and
generating a gateway client. Architecture programs include
conservation of computation,
Muninn, Huginn, and the
Refinery.

Development

cargo build --workspace
cargo test --workspace -- --quiet
cargo clippy --workspace --all-features -- -D warnings
cargo fmt --all -- --check

All crates enforce #![deny(unsafe_code)] except astrid-sys and astrid-sdk, where WASM FFI
requires it. Clippy runs at pedantic level and integer-overflow arithmetic is a lint error. Release
binaries for macOS and GNU/musl Linux (x86_64 and aarch64) are built on tag push and signed with keyless
Sigstore. Self-managed updates authenticate the exact archive and its pinned Astrid release-workflow
identity before independently checking the BLAKE3 manifest and extracting any bytes. Homebrew and
Cargo remain responsible for updates they install; signed SHA-256 manifests remain available for
their compatibility requirements. GitHub build-provenance attestations are published as additional
evidence and are not substituted for the updater's release-archive signature. See the
self-update security model.

Contributing

Contributions are welcome. Astrid uses a tiered contributor system that protects security-critical
code while keeping the door open to new contributors. Every pull request must be linked to a GitHub
issue. See CONTRIBUTING.md for the issue-first workflow and tier descriptions.

Changes to any contract surface (the host ABI, the IPC protocol, the capability model, the manifest
schema, or the SDK public API) go through the RFC process in the
RFCs repository before implementation.

License

Dual-licensed under MIT and Apache 2.0, at your option.

Copyright (c) 2025-2026 Joshua J. Bouw and Unicity Labs.