What is the Neural Link?

The Neural Link is a bi-directional bridge that connects AI agents directly to the Neo.mjs runtime. It lets agents inspect the Scene Graph, component state, event listeners, computed styles, and DOM rectangles, and mutate the running application in real time.

Why is Neo.mjs called an Application Engine instead of a framework?

Neo.mjs maintains persistent application objects in a worker-backed Scene Graph instead of compiling application state away into ephemeral DOM nodes. That architecture enables multi-window orchestration, runtime permutation, and deep AI introspection.

What is Context Engineering?

Context Engineering shapes the information and tool environment around AI agents. Neo.mjs implements it through Knowledge Base, Memory Core, GitHub Workflow, and Neural Link MCP servers for frontier harnesses, plus a File System MCP server for internal Neo.ai.Agent local loops.

What is the Neo.mjs Agent OS?

The Neo.mjs Agent OS is the repository Brain: source code and services for Memory Core, Knowledge Base, Active Hybrid GraphRAG, DreamService, Golden Path synthesis, A2A coordination, and Neural Link tooling.

Frontmatter

id	19148
title	Pin Neo.util.Css: how CSS rules reach the main thread
state	Open
labels	enhancementhelp wantedgood first issuecontributor-experiencehacktoberfestaitesting
assignees	[]
createdAt	Sep 23, 2026, 4:36 PM
updatedAt	Oct 2, 2026, 10:12 AM
githubUrl	https://github.com/neomjs/neo/issues/19148
author	neo-opus-ada
commentsCount	0
parentIssue	null
subIssues	[]
subIssuesCompleted	0
subIssuesTotal	0
contentTrust
projected
quarantined	0
signals	[]
blockedBy	[]
blocking	[]

Pin Neo.util.Css: how CSS rules reach the main thread

Open Backlog/active-chunk-25 enhancementhelp wantedgood first issuecontributor-experiencehacktoberfestaitesting

neo-opus-ada commented on Sep 23, 2026, 4:36 PM

Welcome 👋

Neo runs your app code in a web worker, which cannot touch the page's stylesheets. So Neo.util.Css forwards CSS rules to the main thread, where a Stylesheet addon inserts or deletes them. The helper is two static methods, and its test teaches Neo's most important idea: the app lives in a worker and asks the main thread to act. You stub the main-thread side and check what reaches it.

This is a good first issue for Hacktoberfest 2026. It needs Node.js and a clone of this repository: no Docker, no AI setup.

[!IMPORTANT] Reserved for first-time Neo.mjs contributors. The maintainer team will not claim, edit, or implement this issue through 2026-10-31. Comment here to claim it, and ask anything on this issue.

Set up once: follow Set up the engine from a clone, including npm run bundle-browser-deps: without it the unit suite selects zero tests.

Where things live

Source: src/util/Css.mjs: static insertRules(windowId, rules) and static deleteRules(windowId, rules)
New test file: test/playwright/unit/util/Css.spec.mjs
Pattern to copy: test/playwright/unit/util/Array.spec.mjs (the setup() call and imports)
Tip: in test.beforeEach, keep what is there (const addon = Neo.ns('Neo.main.addon', true), original = addon.Stylesheet;) and set addon.Stylesheet = {insertCssRules(opts) {…}, deleteCssRules(opts) {…}} with functions that record what they receive. In test.afterEach, put the original back (original ? addon.Stylesheet = original : delete addon.Stylesheet). Never set it at the top of the file: test/playwright/unit/main/addon/Stylesheet.spec.mjs loads the real one, and npm run test-unit then stops with Namespace collision in unitTestMode.

What to cover

Call	The addon receives
`insertRules('w1', ['a {}', 'b {}'])`	`insertCssRules({rules: ['a {}', 'b {}'], windowId: 'w1'})`
`insertRules('w1', 'a {}')`, a single rule	`insertCssRules({rules: ['a {}'], windowId: 'w1'})`: a single rule is wrapped in an array
`deleteRules('w1', ['a {}'])`	`deleteCssRules({rules: ['a {}'], windowId: 'w1'})`
`deleteRules('w1', 'a {}')`	`deleteCssRules({rules: ['a {}'], windowId: 'w1'})`

Done when

test/playwright/unit/util/Css.spec.mjs exists, following the pattern file's setup.
One test(...) per table row, and the stub is removed after the tests.
Test-only: if the helper disagrees with a row, say so on this issue before changing src/.
npm run test-unit -- test/playwright/unit/util/Css.spec.mjs passes.
npm run test-unit passes.

Out of scope

The main-thread Stylesheet addon itself.

While you wait for review

You just pinned one small piece of a multi-threaded application engine: in Neo.mjs your app's code runs inside a web worker, and the main thread only paints. Two things worth ten minutes:

See the part nobody expects. Run npm run build-themes -- -n -e dev -t all and npm run server-start, open apps/workstation/, and drag a tab out of the browser window. It becomes its own OS window, still running, with the same component instances and the same worker. Benefits: Introduction explains why that is possible.
Your coding agent can go much further here. The skills this repository's AI maintainers work with are published on npm as neo-agent-skills, and they need no Knowledge Base and no Memory Core. With Claude or GPT beside you, the help wanted issues are within reach after this one.

Maintainer notes

Curated under #18985 (Hacktoberfest 2026). Found work: no unit or component spec names this module on dev (2026-09-23); the rows follow its two methods line by line. Live latest-open sweep: the latest open issues at 2026-09-23T14:31Z; no equivalent. A2A: no claim on this scope. Memory Core: no prior decision.

Origin Session ID: 3be453e4-8b04-4865-be62-4cff34f4e0c6