What is the 'Neural Link'?

The Neural Link is a bi-directional bridge that connects AI agents (like Gemini or Claude) directly to the Neo.mjs runtime. It allows agents to 'see' the application's Scene Graph, inspect component state, verify event listeners, and even mutate the running application in real-time. This turns the application into a 'glass box' for AI, enabling autonomous debugging and feature development.

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

Traditional frameworks are general-purpose libraries (like a Toyota) that help you organize code, but they compile away into ephemeral DOM nodes. Neo.mjs is a precision-engineered runtime (like an F1 car), similar to Unreal Engine for games. It maintains a persistent 'Scene Graph' of objects in a separate worker thread. These objects retain their identity, state, and relationships, allowing for advanced capabilities like multi-window orchestration, runtime permutation, and deep AI introspection that are impossible with 'melted plastic' DOM-based frameworks.

What is 'Context Engineering'?

Context Engineering is the practice of curating the environment and information flow for AI agents to maximize their autonomy. In Neo.mjs, this is implemented via three Model Context Protocol (MCP) servers: a Knowledge Base for semantic code understanding, a Memory Core for learning from past sessions, and a GitHub Workflow server for project management. This ecosystem allows agents to work as fully integrated members of the development team.

What is 'Object Permanence' in the context of Neo.mjs?

In Neo.mjs, UI components are persistent JavaScript objects living in the App Worker, not just transient rendering results. This 'Object Permanence' means a component (like a Dashboard) maintains its state (scroll position, user input, internal logic) even if it is detached from the DOM or moved to a different browser window. This is the 'Lego Technic' approach versus the 'Duplo' approach of traditional frameworks.

What is an 'Agent Operating System'?

Neo.mjs v11 introduced the concept of an Agent OS, where the platform itself provides the tools and interfaces for AI agents to operate. It combines a standalone, type-safe AI SDK for autonomous 'Code Execution' with the Neural Link for runtime control. This enables agents to monitor, debug, and heal the application autonomously, effectively acting as an operating system for synthetic intelligence.

How does Neo.mjs handle multi-window applications?

Neo.mjs uses shared web workers to run a single application instance across multiple browser windows. All windows share the same application state and data in real-time. Components can even move between windows while retaining their JavaScript instances. This enables desktop-class experiences like multi-window IDEs, browser-based email clients, and multi-screen control rooms.

What makes Neo.mjs different from React, Angular, or Vue?

Neo.mjs is fundamentally different in its architecture: (1) It uses True Multithreading via web workers to prevent UI jank, (2) It is an AI-Native Application Engine with built-in bridges for AI collaboration, and (3) It treats components as persistent objects in a Scene Graph, enabling native multi-window support and runtime permutation.

Frontmatter

id	9402
title	Performance: Eliminate Main Thread Layout Thrashing in getTargetData
state	Closed
labels	enhancementaiperformance
assignees	tobiu
createdAt	Mar 8, 2026, 11:27 PM
updatedAt	Mar 8, 2026, 11:46 PM
githubUrl	https://github.com/neomjs/neo/issues/9402
author	tobiu
commentsCount	1
parentIssue	null
subIssues	[]
subIssuesCompleted	0
subIssuesTotal	0
blockedBy	[]
blocking	[]
closedAt	Mar 8, 2026, 11:46 PM

Performance: Eliminate Main Thread Layout Thrashing in getTargetData

Name: Neo.mjs Application Engine
Author: Neo.mjs

Closed v12.1.0 enhancementaiperformance

tobiu commented on Mar 8, 2026, 11:27 PM

Problem: Profiling the Main Thread during rapid Grid scrolling reveals a massive layout thrashing penalty:

Recalculate style: 38.5% total time
get scrollTop & getBoundingClientRect: ~9% total time

This occurs because the generic src/main/DomEvents.mjs listener intercepts highly frequent scroll and wheel events and calls getTargetData(target) to build the event payload. getTargetData unconditionally reads node.getBoundingClientRect(), node.offsetHeight, node.scrollHeight, etc., for every node in the event path. When these reads occur immediately after the Main Thread has applied VDOM deltas (e.g., updating transforms for row recycling), the browser is forced to synchronously flush the layout queue and recalculate all styles just to return the unused rect data.

Proposed Solution: Pass the event.type into getTargetData(). If the event is a high-frequency continuous event that does not rely on bounding rects (specifically scroll and wheel), skip the getBoundingClientRect() and offset/client/scrollHeight reads entirely.

This prevents forced synchronous layouts and reclaims nearly 40% of the Main Thread's blocking overhead during scrolling.

DX Tradeoff Note: We must heavily document this change. Developers relying on data.path[n].rect inside onScroll handlers will now receive an empty object or null. This is an intentional architectural safeguard. If rects are truly needed during scrolling, they must be requested explicitly via Neo.main.DomAccess.getBoundingClientRect().

tobiu added the enhancement label on Mar 8, 2026, 11:27 PM

tobiu added the ai label on Mar 8, 2026, 11:27 PM

tobiu added the performance label on Mar 8, 2026, 11:27 PM

tobiu referenced in commit 067c823 - "perf: Eliminate Main Thread Layout Thrashing in getTargetData (#9402)" on Mar 8, 2026, 11:36 PM

tobiu assigned to @tobiu on Mar 8, 2026, 11:36 PM

tobiu Mar 8, 2026, 11:46 PM

Input from Gemini 3.1 Pro:

✦ Task Completed:

Added eventName to getTargetData and getSelectionPath in src/main/DomEvents.mjs.

Implemented a fast path: If eventName === 'scroll' || eventName === 'wheel', the framework no longer calls node.getBoundingClientRect() or reads offsetHeight/scrollHeight in getTargetData.

Retained these properties for all other events (clicks, dragging, selection) and addons (IntersectionObserver, ResizeObserver) by passing undefined by default.

Benchmark Review Note: Subsequent performance tracing revealed that while this successfully eliminated getBoundingClientRect overhead, the browser's forced synchronous layout simply shifted to the next geometric read: node.scrollTop (consuming 13.1% of Main Thread time).

This confirms the necessity of this initial pruning, but also proves we need a follow-up ticket to aggressively prune scrollTop/scrollLeft reads for ancestor path elements.

Closing this ticket as the specific getBoundingClientRect and dimension stripping has been implemented.

tobiu closed this issue on Mar 8, 2026, 11:46 PM