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. Automatic crash recovery, 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. Inspection JSON is editable for inactive paused/failed actors; saving restores protected fields with a warning. The image owns mutable, directory-based Rune source files with independent commit history. The CLI exposes source writes, commit/history/rollback, reload/become, graceful shutdown, kill, restart, pause/resume, and cancellation through a trusted 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. The debugger foundation exposes bounded active Rune stack frames and exact loaded source through read-only protocol inspection and VS Code's Inspect Execution Stack... actor action. Actor-local source breakpoints and bounded step-into/over/out are implemented through the protocol and VS Code actor actions. Debug Actor attaches a native VS Code debug session with gutter breakpoints, the call-stack view, and bounded toolbar stepping. Continue resumes the actor; scheduler ticks remain explicit. The Variables view exposes a read-only committed actor snapshot with expandable state and mailbox. Watch and Debug Console accept snapshot paths such as actor/committed_state; they never execute actor code. Frame locals and Rune expression evaluation remain unimplemented. Failed actors can also be attached for exception details and retained-snapshot inspection without restarting them; post-mortem stacks are not retained. Explicit disk image save/restore is implemented at handler boundaries, including sources/history, actor identities, committed state, mailboxes and retained logs.

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 repl

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 repl and start the server with the corresponding --listen address. Quitting the REPL disconnects only that client; actors and source files survive until the server exits. Ctrl+C and Ctrl+D also exit the REPL and complete the WebSocket close handshake. Reconnect and use ps to recover their references. REPL bindings and command history are session-local and are not restored on reconnect.

Save and restore an image

cargo run -p runa-cli -- save /path/to/image.runa.json
cargo run -p runa-cli -- restore /path/to/image.runa.json

The REPL also accepts save <file> and restore <file>. VS Code provides Runa: Save Image... and Runa: Restore Image.... Paths refer to the server's filesystem, not the client's. Saving requires a new destination file. The server captures all actors at a handler boundary and leaves runnable actors paused after a successful save. Saving is rejected without changing the image if any handler is unfinished, including paused or awaiting execution.

Restore replaces the whole image after validating and recompiling the snapshot. Actors that were runnable when saved resume scheduling eligibility; previously paused and failed actors stay that way. Execution still requires explicit ticks. Actor references survive, but incarnations advance and old debug sessions end. Restore also refuses to replace an image with unfinished handlers. Only saved data survives server exit; this is not an automatic checkpoint, durable per-message transaction log, or execution-stack serialization. See runtime persistence guarantees.

Commands and connections

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 repl

runa-cli requires a subcommand. Use runa-cli repl for an interactive session, or run an image operation directly:

cargo run -p runa-cli -- ps
actor=$(cargo run -p runa-cli -- spawn actors/counter)
cargo run -p runa-cli -- send "$actor" '{"op":"inc"}'
cargo run -p runa-cli -- tick 100

Each image operation in the REPL has a matching subcommand; use runa-cli <command> --help for arguments. Quote JSON as a single shell argument. One-shot commands use actor references rather than session-local bindings, print results without a REPL banner, and exit unsuccessfully on errors. let name = spawn ... is session-local REPL syntax. quit (alias exit) exits either interface without stopping the image. cancel is no longer a REPL command; the underlying runtime cancellation API remains available.

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 server loads the bundled source/actors/counter.rn working file at startup. Connecting a client does not modify source or create a commit:

runa> let counter = spawn actors/counter
counter = @<actor-reference>
runa> send counter {"op": "inc"}
message queued
runa> tick 100
runa> pause counter
runa> inspect counter
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 counter treats missing/null state as zero on its first message, increments and logs its value, then queues another inc message to itself. It runs only when ticks advance; pause/resume controls its loop. An explicit integer initial state is preserved. The REPL provides Tab completion and Up/Down command history. write actors/counter <local-file> updates the image's working source. commit actors/counter records a snapshot with an automatically generated readable revision ID; history actors/counter lists commits and rollback actors/counter <revision> restores a working file. Committing is version control only: spawn always compiles the current image file, including uncommitted changes. Invalid working code fails spawn without creating an actor; commits can preserve invalid work in progress. reload <actor> loads current source at its existing path, and become <actor> <path> switches scripts, preserving state and queued messages after the active handler completes. stop runs optional on_shutdown(state) after the active handler and then removes the actor; kill removes it immediately without shutdown. Removal discards identity, state, mailbox, and retained logs. Failed actors remain inspectable until killed. restart creates a new incarnation with the same state and loaded script, without reloading. Restart is independent of stop/kill; a removed actor cannot be restarted. Pause/resume remain cooperative controls between scheduler slices. 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 <path> <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. Protocol version 5 uses handle(ctx, state, sender, message) -> new_state; ctx.send(recipient, message) records sends with the calling actor as sender, and ctx.send_from(sender, recipient, message) supports forwarding. Returning state is optional: an omitted return, return;, or () retains the previously committed state, discarding invocation-local state mutations. Valid sends still commit and the message is acknowledged. The same rule applies to on_shutdown(state). To replace state, return a non-unit portable value. Unit can no longer be used to reset state to null; use host state editing instead. Sender metadata is separate from message data; host-originated messages have unit/null sender. System messages are trusted runtime commands, not data an actor can construct.

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. Open the Runa Activity Bar sidebar. Its Actors view lists actors created through the REPL or another client as expandable directories. Open meta.json for read-only identity/status/behavior-path metadata, config.json for live log-level configuration, state.json for natural JSON state, mailbox.json for reserved/queued messages, or actor.log for retained logs. State and mailbox JSON use two-space indentation and preserve exact integers. The .log file uses syslog-style lines and VS Code's built-in log highlighting. State and mailbox files are writable only for inactive paused/failed actors. Server notifications automatically refresh the tree and open files; Runa: Refresh Image is also available on demand.

The Image Sources view in the Runa sidebar automatically shows the image's virtual filesystem beneath source, including actors/counter.rn, without adding a workspace folder. Open a file and save edits to update the image without committing. Right-click a source file to Spawn (null state) or Spawn with State (which prompts for JSON), or to commit, browse history, and roll back. Historical revisions remain read-only. The source toolbar and context menus support creating, renaming/moving, and deleting files. Renaming an in-use behavior asks to update every actor using its path; declining cancels the rename. Deleting a source used by a running actor is rejected with a stop-first error.

Edit Current Behavior on an actor opens its loaded script (or existing temporary script). Saving compiles an actor-specific override and installs it at the next handler boundary without changing shared source, state, or mailbox. A behavior file then appears inside the actor directory. Reload Actor Source clears the override, Go to Behavior opens the shared source, and Update Behavior asks before copying the temporary text into shared working source without committing.

Use Runa: Spawn Actor to choose a source path and supply JSON initial state. Actor context menus offer structured messages and system lifecycle commands. Runa: Advance Scheduler explicitly executes ticks; sending alone only queues a message. The extension does not start or shut down the image. Disconnecting leaves actors in the server. Detailed runtime event subscriptions and source-level debugging are not implemented yet. Rune compilation errors and warnings appear inline and in Problems for open image sources and actor-specific behavior documents, including unsaved edits. Validation does not save, commit, or install the editor text. See the extension guide for connection restrictions, snapshot semantics, and tests.

Repairing actors and reading logs

State and messages can be edited only on paused or failed actors with no active invocation. An active handler must finish or be cancelled through the runtime cancellation API; kill removes the actor rather than making it editable. State edits preserve messages; message edits preserve state. Neither restarts an actor. Reserved messages are retried first on restart; clearing the reserved array removes the failed input.

set-state @<actor-ref> 1
set-messages @<actor-ref> {"reserved":[],"queued":[{"op":"add","value":2}]}
log-level @<actor-ref> debug
logs @<actor-ref>
logs -f

These are REPL commands and runa-cli subcommands (quote JSON when using a shell). REPL log filters also accept session-local actor names. Omitting the filter selects all actors. logs prints retained history; logs -f additionally subscribes to future entries until Ctrl+C, which returns to the REPL or closes a one-shot CLI. In VS Code, actor context menus offer Edit Actor State..., Edit Reserved and Queued Messages..., and Set Actor Log Level.... The actor directory provides editable state/mailbox files and a config.json that remains writable while running. The Inspect Actor command also retains the combined JSON editor; protected fields there are restored with a warning. The Actors toolbar advances the scheduler, and Copy Actor Reference copies a reference from the actor context menu.

Rune handlers can call ctx.log("info", "message"), or ctx.trace, ctx.debug, ctx.info, ctx.warn, ctx.error, and ctx.fatal with a string message. Severity order is trace < debug < info < warn < error < fatal; the default threshold is info. Only entries at or above the actor's threshold are retained or emitted. Logs are immediate diagnostics, not transactional effects: they survive handler failure and may repeat on retries. Each actor keeps its latest 1,000 accepted messages in memory, each limited to 512 UTF-8 bytes. Restart preserves logs and the threshold. Server exit loses them. Rebuild the server, CLI, and extension together for protocol v5.

The read-only ctx.this field is the current actor's typed reference: ctx.send(ctx.this, message) queues a normal transactional message to itself.

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.