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	19134
title	Pin the ways ClassSystem.beforeSetInstance turns a config into an instance
state	Open
labels	enhancementhelp wantedgood first issuecontributor-experiencehacktoberfestaitesting
assignees	[]
createdAt	Sep 23, 2026, 4:27 PM
updatedAt	Sep 24, 2026, 4:56 PM
githubUrl	https://github.com/neomjs/neo/issues/19134
author	neo-opus-ada
commentsCount	0
parentIssue	null
subIssues	[]
subIssuesCompleted	0
subIssuesTotal	0
contentTrust
projected
quarantined	0
signals	[]
blockedBy	[]
blocking	[]

Pin the ways ClassSystem.beforeSetInstance turns a config into an instance

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

neo-opus-ada commented on Sep 23, 2026, 4:27 PM

Welcome 👋

Many Neo configs accept almost anything: a class, a class name, a config object, an object with an ntype, or a ready instance. They all end up as one instance. That conversion is a single static method, Neo.util.ClassSystem.beforeSetInstance(). It is used across the engine, it is short, and it has no test. Pinning it is a great way to learn how Neo creates things.

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/ClassSystem.mjs, static beforeSetInstance(config, DefaultClass = null, defaultValues = {})
New test file: test/playwright/unit/util/ClassSystem.spec.mjs
Pattern to copy: test/playwright/unit/util/Array.spec.mjs (the setup() call and imports)
Tip: define a tiny test class in the spec (extend Neo.core.Base, give it a className and an ntype, register it with Neo.setupClass) so every row has something to create. Give it static observable = true, as src/util/HashHistory.mjs does: core.Base has no on() of its own, and the row that passes listeners needs one.

What to cover

`config`	`DefaultClass`	Returns
`null`	a class	a new `DefaultClass` instance built with `defaultValues`
`null`	a class name string	the name is resolved with `Neo.ns()`, then as above
a class	—	`Neo.create(config, defaultValues)`
`{ntype: '…', …}`	—	`Neo.ntype({...defaultValues, ...config})`: keys in `config` win over defaults
`{…}` without `ntype`	a class	`Neo.create({module: DefaultClass, ...defaultValues, ...config})`
an existing instance	—	the same instance; when `defaultValues.listeners` is given, those listeners are attached with `on()`
`null`	none	`null`, returned unchanged

Done when

test/playwright/unit/util/ClassSystem.spec.mjs exists, following the pattern file's setup.
One test(...) per table row, each checking the class of what comes back (and identity for the instance row).
Test-only: if the method disagrees with a row, say so on this issue before changing src/.
npm run test-unit -- test/playwright/unit/util/ClassSystem.spec.mjs passes.
npm run test-unit passes.

Out of scope

The callers of beforeSetInstance and Neo.create 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). Live latest-open sweep: the latest 20 open issues at 2026-09-23T14:24Z; no equivalent (the ClassSystem title search returns closed history only). A2A: no claim on this scope. Memory Core: no prior decision.

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