NATS Client for VS Code

A VS Code workflow inspired by the HTTP Client: author .nats files, run CodeLens actions, visualize replies, and manage connection variables without leaving the editor.

Highlights

• NATS-native scripts – Parse SUBSCRIBE, PUBLISH, REQUEST, REPLY, and JETSTREAM blocks with headers, payloads, and metadata via src/core/nats-document-parser.ts.
• One-click execution – src/features/code-lens attaches CodeLens controls that start or stop subscriptions, fire requests, publish payloads, and pull JetStream batches without switching focus.
• Structured logging – OutputChannelRegistry multiplexes per-subject logs while appendLogBlock groups meta data, headers, and payload previews in the primary output channel.
• JetStream tooling – The nats.jetStreamPull command (see register-jetstream-pull-command.ts) hydrates durable pullers that honor timeout and batch headers.
• Environment-aware variables – Manage secrets and templated tokens via the NATS Variables tree view backed by VariableStore, including {{token}} substitutions and {{env:NAME}} lookups.
• Status-aware sessions – StatusBarController keeps an at-a-glance connection count, while NatsSession tracks active subscriptions and reply handlers so you can tear them down quickly.

Script format

Each action block mimics the HTTP Client grammar:

REQUEST nats://localhost:4222/lab.echo
NATS-Timeout: 5000
Trace-Id: randomId()

{
	"id": randomId(),
	"subject": "cpu"
}

• Headers prefixed with NATS- configure connection metadata (server overrides, JetStream durable names, batch sizes, etc.).
• Trace headers (Trace-Id, Responder-Id, …) are forwarded to the server.
• Variables defined in the tree view can be referenced via {{token}}; environment variables use {{env:NAME}}.
• Use triple hashes (###) to separate multiple actions inside the same document.

Examples

Ready-to-run flows live under examples/:

• examples/pub-sub.nats – two concurrent subscriptions plus matching publish blocks for quick smoke tests.
• examples/request-reply.nats – combines reply handlers with literal and JSON requests, showing how $msg templates render responses.
• examples/jetstream-pull.nats – demonstrates durable JetStream pulls (NATS-Stream, NATS-Durable, and NATS-Batch).

Open an example, hover the CodeLens for the action you want, and execute the command to stream results into the output channel.

Variables and templating

• The NATS Variables tree appears in the Explorer view (NATS Variables). Use the view title buttons and the item/context menus to add, edit, delete, copy, and set the active environment.
• The tree stores named variables per environment; the active environment is used when resolving tokens before requests, publishes, subscriptions, and reply handlers.
• Reference variables using {{name}}; use {{env:NAME}} to read OS environment variables.
• Built-in helpers include randomId() and $json.* / $msg.* shortcuts evaluated by nats-actions and nats-session for templated replies.

Features

The extension contributes the following entry points:

• Inline CodeLens controls appear above action blocks in .nats files; these are the primary way to run subscriptions, requests, publishes, and reply handlers.
• A NATS Variables Explorer view provides add/edit/delete and copy actions for environments and variables via view title buttons and context menus.
• The status bar shows the current active connection count. A connection management QuickPick is available via the NATS: Manage Connections command (registered by the extension).
• Status bar indicator that surfaces active connection counts.

Configuration

Development workflow

bun install
bun run watch                 # incremental builds while editing
bun run verify                # format, lint, typecheck, and unit tests
bun run test:e2e              # Vitest e2e suite
bun run integration:test      # VS Code harness (xvfb on CI)

Contributing & support

• Issues: github.com/mfahmialkautsar/vscode-nats-client/issues
• Discussions and feature requests are welcome—attach example .nats files when possible so we can reproduce flows quickly.