# Runa VS Code client This is a development client for a trusted localhost Runa image. It uses the [version 3 protocol](../docs/protocol.md) over WebSockets with the `runa-debug` subprotocol, not Rust APIs, and never hosts actors or starts its own image. ## Run from source Requirements: VS Code 1.96+, Node.js 22+, npm, and the repository's Rust toolchain. From the repository root: ```sh npm --prefix vscode ci mise run start ``` Open the repository in VS Code. In Run and Debug, select **Run Runa Extension** and press F5. The launch task compiles TypeScript before opening an Extension Development Host. In that host: 1. Run **Runa: Connect to Local Image**. The default is `127.0.0.1:3737`; `runa.address` changes the suggested endpoint. 2. Expand **Runa Actors** in Explorer. Use its **+** button or **Runa: Spawn Actor** to choose a published behavior, then enter JSON initial state (for example `0` for `counter`). There is no default behavior or implicit state. The command reports and returns the new actor reference. Mailbox capacity is 64. 3. Click an actor or run **Runa: Inspect Actor** to open its JSON snapshot. 4. Right-click an actor to send a JSON message or pause/resume/stop/restart it. These actions are also available in the Command Palette with an actor picker. 5. Use **Runa: Advance Scheduler** to execute an explicit number of ticks (instruction budget 32 per actor). Send only queues a message; it does not execute it. For the counter, send `{"op":"add","value":7}`, then advance. 6. Run **Runa: Disconnect** to close only this client connection. JSON input supports null, booleans, signed 64-bit integers, strings, arrays, and objects. Floats and out-of-range integers are rejected rather than rounded. Use `{"$actor":"@<21-character-reference>"}` for a typed actor reference and `{"$record":{"$actor":"literal"}}` to escape a marker-shaped object. REPL-local names are not shared with the extension. Input uses the same depth/node/string limits as the runtime; the full wire request must also fit 1 MiB. Cancelling a prompt sends no mutation. Changing connections during a prompt rejects the action instead of applying it to the new image. Connection prompts accept numeric IPv4 loopback addresses (`127.x.x.x`) or `[::1]:port`. DNS names, wildcard addresses, remote addresses, and IPv4-mapped IPv6 addresses are rejected. There is no authentication: connect only to a trusted local server. In a remote VS Code window, localhost refers to the machine running the extension host, not necessarily the desktop. ## Snapshot semantics - The tree shows actor references, lifecycle status, and queued/reserved counts. Tooltips include implementation ID, incarnation, and failure text. - Inspect fetches a fresh snapshot through `inspect_actor`. Documents show committed state, FIFO queued messages, the reserved message, status, and active-execution telemetry. Tagged values distinguish actor references from strings and preserve signed 64-bit integers exactly. - Documents are read-only snapshots, not editable actor state or live VM frames. The timestamp records when this client received the data, not a runtime clock. Server `image_changed` notifications automatically update the tree and open documents. Bursts are coalesced, and changes arriving during a fetch trigger a follow-up fetch. **Refresh Actors** is also available on demand. - Open documents are retained and marked `connected: false` on disconnect. Each connection gets distinct document URIs; reconnecting never replaces snapshots from an earlier connection or another image. Closing a document releases its cache; snapshots are not persisted across VS Code restarts. - There is no auto-connect, polling, automatic reconnect, or request retry. Timeout, peer disconnect, malformed data, and version/correlation failures invalidate the connection and are surfaced in a notification and the **Runa** output channel. Server-reported operation errors leave the connection usable. - The client never ticks the scheduler implicitly or drains `get_events`. Behavior publication/installation still requires the REPL or another client. Notifications are non-destructive invalidations, not a replayable runtime event stream; reconnect fetches the current image rather than replaying history. For automation, the `runa.connect` command also accepts an explicit endpoint string, and `runa.inspect` accepts an object with an `actor_ref` field. `runa.spawn` accepts `{ behavior: string, state: string }`, where state is natural JSON text, and resolves to the new reference. `runa.send` accepts `{ actor_ref: string }` and JSON message text. `runa.pause`, `runa.resume`, `runa.stop`, and `runa.restart` accept `{ actor_ref: string }`. `runa.tick` accepts a positive integer tick count. Command failures are reported in the Runa output channel and an error notification; commands are never retried. ## Development and validation From the repository root: ```sh mise run format mise run lint mise run test mise run test-extension-host ``` The normal test task covers portable-value validation, framing and UTF-8 fragmentation, subprotocol negotiation, interleaved notifications, refresh coalescing, timeout/disconnect behavior, exact 64-bit integer display, and interoperation with the real Rust server on an ephemeral loopback port. The separate host test downloads VS Code 1.96.4 to the ignored `.vscode-test/` cache and runs spawn/send/lifecycle/tick, connection, inspection, disconnect, and reconnect commands against a test-owned Rust server. It verifies automatic document updates after another client sends messages, pauses, and advances an actor into failure, as well as session isolation. On headless Linux: ```sh xvfb-run -a mise run test-extension-host ``` Behavior/source browsing and editing, compilation diagnostics, detailed runtime event subscriptions, packaging for distribution, and debugging remain future work.