runa/README.md

# Runa — Rune Actors

Runa (short for **Rune Actors**) is an experimental project to build a
persistent, live programming world around isolated actors written in Rune.
The long-term vision combines an inspectable graphical environment with a
programmatic API and a VS Code extension, all connected to the same running
image.

## Status

Runa is at an early prototype stage. The executable runs a Phase 0 feasibility
experiment using Rune 0.14.2: script execution, native calls, async suspension,
instruction budgets, stepping, and compiled-code sharing. It also runs a minimal
single-worker actor demonstration with bounded mailboxes and explicit message
effects. Source and compiled implementation identities are BLAKE3 content
addresses with an in-memory compile cache. Persistence, canonicalization,
remote network access, graphical world, and VS Code extension are not
implemented yet. The code library now supports an in-memory versioned behavior
registry, and the CLI exposes publishing, history, rollback, safe-boundary
installation, pause/resume, and cancellation through a trusted in-process image
API. A versioned transport-neutral protocol contract is now defined, but no
authentication is implemented. The dispatcher is available through local
JSON-lines stdio and an unauthenticated TCP listener restricted to localhost;
both use a bounded request size. The interactive CLI connects to the localhost
server over TCP, so multiple clients operate on the same server-owned image.

The prototype uses worker-local invocation stacks and cooperative instruction
slices, and actor snapshots report basic active-execution progress. Native
callbacks are not preemptible; source-level debugging and persistent storage
are not implemented.

## Design goals

- Keep actor identity, mailbox, private state, behavior, and incarnation
  separate.
- Use message passing rather than shared mutable state for actor interaction.
- Keep behavior implementations immutable and support safe, versioned updates.
- Expose the same runtime capabilities to in-world tools and external clients.
- Be explicit about execution, delivery, and persistence guarantees.

See [the architecture spec](docs/architecture.md) for the full vision,
architecture, roadmap, and open questions.

## Getting started

You need a Rust toolchain that supports the workspace's Rust 2024 edition.

Start the live image from the repository root:

```sh
mise run serve-network
```

In another terminal, connect the REPL:

```sh
mise run start
```

The REPL defaults to `127.0.0.1:3737`. To select another loopback endpoint,
use `cargo run -p runa -- --connect 127.0.0.1:4000` and start the server with
the corresponding `--listen` address. Quitting the REPL disconnects only that
client; actors and published behaviors survive until the server exits.
Reconnect and use `actors` to recover their references. REPL bindings and
command history are session-local and are not restored on reconnect.

For a local child-process protocol endpoint, run `mise run serve` and exchange
one JSON request per line on stdin; responses are written to stdout. Request
lines are limited to 1 MiB.

For a TCP endpoint, run `mise run serve-network`. It listens on
`127.0.0.1:3737` and accepts the same JSON-lines protocol, with up to 16
simultaneous clients sharing one live image. The listener rejects non-loopback
addresses and has no authentication; any local process that can connect has
full access to the development API. Use it only on a trusted local machine.

The `runa-client` crate can launch the stdio process or connect over loopback
TCP and exchange typed protocol requests with request/response correlation.
TCP connection establishment is limited to 5 seconds and reads/writes to 30
seconds. Transport failures disconnect the client and are never automatically
retried: an operation may have committed even if its response was lost.
The VS Code extension is
intended to connect over the network to this same live image; actors remain in
the image regardless of how clients connect. Remote network access requires
authentication and authorization, which are not implemented.

The TCP server publishes the bundled `counter` behavior once at startup;
connecting a client does not publish or reset behavior revisions:

```text
runa> let sender = spawn counter 0
sender = @<actor-reference>
runa> let receiver = spawn counter 10
receiver = @<actor-reference>
runa> send sender {"op": "send", "value": 5, "target": {"$actor": "receiver"}}
message queued
runa> tick 100
runa> inspect sender
runa> inspect receiver
runa> events
```

Actor references are generated NanoIDs rather than sequential numbers. The
`let` form binds each spawned actor to a local name; references can also be
entered directly with an `@` prefix. The sender commits state `1` and sends a
message to the receiver, which commits state `15`. The REPL provides Tab
completion and Up/Down command history. It also supports publishing Rune source
files as named, versioned behaviors, viewing history, rolling back a behavior
reference, installing the current version on an idle actor, and cooperatively
pausing and resuming or cancelling actor invocations between scheduler ticks.
Runtime users can also supply an explicit state migration closure during
installation; the CLI's install command preserves state as-is. Use `help` in
the session for the complete command list.
State and messages support null, booleans, signed 64-bit integers, strings,
lists, records, and distinct actor-reference values. `spawn <behavior> <json>`
sets initial state; `send <actor> <json>` sends any supported value. JSON
objects of the form `{"$actor": "name-or-@reference"}` embed an actor reference,
including inside a record or list. See the [runtime guide](docs/runtime.md)
for Rune conversions and value limits. This is protocol version 3; old
four-argument Rune handlers and kind/value/target message envelopes must be
updated to the two-argument handler contract.

See [the feasibility report](docs/rune-feasibility.md) for verified Rune
capabilities and limitations, and [the runtime guide](docs/runtime.md) for
the runtime contract.

## Development

Install [mise](https://mise.jdx.dev/) and run `mise install` to install Tombi.
Rust, rustfmt, and Clippy must also be available on your PATH.

```sh
mise run format
mise run lint
mise run test
mise run pre-commit
```

The pre-commit task runs formatting, linting, and tests in that order, stopping
on the first failure. Run it successfully before committing and review any
formatter changes. This is a task, not an automatically installed Git hook.

Tombi formats TOML files offline; rustfmt formats all workspace Rust code.
Clippy checks all workspace targets with warnings treated as errors, and the
test task runs `cargo test --workspace`.

## Project structure

```text
.
├── Cargo.toml
├── crates/
│   ├── runa/             # Main binary
│   ├── runa-core/        # Shared stable identities and portable actor values
│   ├── runa-actor/       # Actor value contracts
│   ├── runa-code/        # Source identities and compile cache
│   ├── runa-rune/        # Phase 0 Rune experiments
│   ├── runa-runtime/     # Single-worker actor prototype
│   ├── runa-image-api/   # Trusted in-process image operations
│   ├── runa-protocol/    # Versioned transport-neutral wire DTOs
│   ├── runa-server/      # Protocol dispatcher and local JSON-lines transport
│   └── runa-client/      # Stdio child-process and loopback TCP clients
├── docs/
│   ├── architecture.md
│   ├── protocol.md
│   └── decisions/
├── runa-std/
│   ├── core/
│   ├── actors/
│   ├── ui/
│   └── tools/
├── scripts/
├── vscode/
├── examples/
└── tests/
```

`runa-std/` is reserved for the default Rune scripts loaded into an image.
`scripts/` is for general-purpose development automation. Root-level `tests/`
is reserved for system and end-to-end tests; it is not automatically discovered
by Cargo. Add an explicit runner when those tests are introduced, keeping Rust
crate integration tests within each crate.

Only the Phase 0 and minimal Phase 1 crates are present. Remaining crates will
be added as their functionality is implemented.