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, and the graphical world are not implemented yet. A minimal VS Code extension can connect to the local image, list actors, and inspect state, queued/reserved messages, and execution telemetry in read-only documents. 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 runa server provides an unauthenticated WebSocket listener restricted to localhost, with bounded request sizes. The runa-cli REPL and VS Code connect with the runa-debug WebSocket subprotocol, so clients share one server-owned image. Server change notifications automatically refresh VS Code's actor tree and inspectors.

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 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:

mise run start

In another terminal, connect the REPL:

mise run cli

The REPL defaults to 127.0.0.1:3737. To select another loopback endpoint, use cargo run -p runa-cli -- --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.

Both executables use Clap for --help, --version, and argument validation. runa listens on 127.0.0.1:3737 without arguments. Set RUNA_LISTEN to change the server address and RUNA_CONNECT to change the REPL address; explicit --listen and --connect flags override their respective environment variables. For example:

RUNA_LISTEN=127.0.0.1:4000 mise run start
RUNA_CONNECT=127.0.0.1:4000 mise run cli

The server is WebSocket-only; stdio transport has been removed. By default it listens on ws://127.0.0.1:3737/ and requires the runa-debug subprotocol, 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 connects over loopback WebSockets and exchange typed protocol requests with request/response correlation. Network connection establishment is limited to 5 seconds and response waits/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 connects 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 WebSocket server publishes the bundled counter behavior once at startup; connecting a client does not publish or reset behavior revisions:

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 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 for verified Rune capabilities and limitations, and the runtime guide for the runtime contract.

VS Code client

With Node.js 22+ and npm installed, run npm --prefix vscode ci. In VS Code, open this repository and launch Run Runa Extension from Run and Debug (F5). Start mise run start, then use Runa: Connect to Local Image in the Extension Development Host. The Runa Actors view in Explorer lists actors created through the REPL or another client. Click an actor to inspect it. Server notifications automatically refresh the tree and open snapshots; Runa: Refresh Actors is also available on demand.

The extension does not start, tick, or stop the image. Disconnecting leaves actors running in the server. Editing, spawn/send controls, and detailed runtime event subscriptions are not implemented yet. See the extension guide for connection restrictions, snapshot semantics, and tests.

Development

Install mise and run mise install to install Tombi. Rust, rustfmt, Clippy, Node.js 22+, and npm must also be available on your PATH. Install the extension's locked dependencies with npm --prefix vscode ci.

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; Prettier formats the extension. Clippy checks all workspace targets with warnings treated as errors. Extension checks include strict TypeScript and Prettier. The test task runs the Rust workspace tests, extension unit tests, and a TypeScript-to-Rust WebSocket interoperability test. mise run test-extension-host additionally downloads VS Code 1.96.4 into an ignored test cache and tests the actual inspector commands in an isolated Extension Development Host. It requires a graphical display; on headless Linux, use xvfb-run -a mise run test-extension-host.

Project structure

.
├── Cargo.toml
├── crates/
│   ├── runa/             # Image server, protocol dispatcher, WebSocket transport
│   ├── runa-cli/         # Interactive REPL client
│   ├── 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-client/      # Loopback WebSocket client
├── 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.