Introduction

Modern JavaScript codebases are massive.

Monorepos, micro-frontends, shared UI kits, Node services, lambdas, build scripts, and a maze of configuration files. Even experienced engineers open a new repo and think:

Where do I even start?

We throw tools at the problem: code search, static analysis, AI assistants, better IDEs. They help, but they don’t solve the root issue:

We’re missing context.

You shouldn’t need to read half the repository to understand where to add a feature or fix a bug. That’s where a one-page context anchor comes in.

A one-page context anchor is a concise, living document that gives a high-level snapshot of a codebase:

• What this system does
• How it’s organized (modules, directories, domains)
• The most important architectural decisions (and why they were made)
• Where to go to change specific behavior

It doesn’t replace full documentation. It prevents you from getting lost before you even know what you should be reading.

In this post, we’ll explore what a context anchor is, how it connects to module organization and Architecture Decision Records (ADRs), and how it helps both humans and AI agents work effectively in complex JavaScript projects.

The Problem: Code Without Context

In a large JavaScript project, a new (or returning) developer typically:

1. Clones the repo
2. Runs ls or opens the folder in their editor
3. Starts randomly clicking through src/, packages/, or apps/
4. Slowly builds a mental model from scattered clues

This is fragile and expensive:

• Confusion: You’re never sure if you’re editing the “right” module.
• Bugs: You change code in one place, not realizing a different module is the actual source of truth.
• Time waste: You spend hours scanning files instead of shipping features.

AI coding tools experience the same problem. Without clear context, they:

• Suggest changes in the wrong layer
• Miss existing utilities or abstractions
• Propose designs that conflict with decisions you already made

Context is now a first-class concern. If we don’t manage it deliberately, the complexity of our systems manages us.

The One-Page Context Anchor: A Simple Snapshot

A context anchor is a single, high-signal page that answers:

What is this system, how is it structured, and where should I work for a given kind of change?

It doesn’t capture everything. It captures just enough for you to:

• Build a rough mental map in a few minutes
• Know where to look next
• Avoid wandering through unrelated modules

A good one-page context anchor typically includes:

1. System overview
   A short paragraph describing what this repo or app does and how it fits into the bigger picture.

2. High-level architecture

   • Main subsystems or bounded contexts (e.g., auth, billing, ui, api, background-jobs)
   • How they communicate (HTTP, events, message queues, shared libraries)

3. Module organization
   A map of:

   • Key directories or packages
   • What they’re responsible for
   • What they must not do (important boundaries)

4. Key Architecture Decision Records (ADRs)

   • A list of the most important decisions with one-line summaries
   • Links to the full ADR files

5. Change entry points
   Quick instructions like:

   • “To add a new endpoint, go to apps/api/src/routes/*.ts.”
   • “To add a new feature flag, see packages/config/featureFlags.ts.”

6. Operational notes (optional but powerful)

   • How to run, test, and debug the system in the most common scenarios.

When someone joins the project—or returns after six months—they read this page first. The same goes for AI tools: you can feed this page as context to guide automated refactoring or code generation.

Why Module Organization Matters So Much in JavaScript

JavaScript projects are particularly prone to chaos:

• Multiple runtimes (browser, Node.js, serverless)
• Multiple build tools (Webpack, Vite, Rollup, esbuild, Turborepo)
• Mixed paradigms (React, vanilla, Node services, scripts)

Without clear module organization patterns, everything blurs together.

Effective patterns often include:

• Feature-first structure instead of tech-first

  src/
    auth/
      api/
      ui/
      domain/
    billing/
    shared/
  

  Better than scattering all components/, stores/, and hooks/ in global buckets.

• Bounded contexts for large domains
  Separate admin, customer, public, or internal spaces instead of one giant src/.

• Clear ownership of responsibilities

  • ui/ renders views, no business rules
  • domain/ owns domain logic, no HTTP or DOM
  • infra/ talks to databases, APIs, queues, not business decisions

Your one-page context anchor should name and explain these patterns explicitly:

“This repo is organized by domain. Each domain (auth, orders, billing) has domain, infra, and ui layers. Domain modules must not import from ui or infra.”

That single paragraph can save hours of misdirected effort and subtle bugs.

Architecture Decision Records: The Missing Backstory

Even with good structure, developers still ask:

• Why did we choose this framework?
• Why do we use events here instead of direct calls?
• Why do we keep user data split across services?

That’s where Architecture Decision Records (ADRs) shine.

An ADR is a lightweight, one-page document that captures:

• Title: A clear decision name
• Context: The situation and constraints
• Decision: What was chosen
• Alternatives: What was rejected
• Consequences: Tradeoffs and impacts

Example (abridged):

# ADR-003: Use Event-Based Communication Between Billing and Orders

## Context
We need billing and orders to stay decoupled so we can scale them independently.

## Decision
Use a message bus with domain events (`OrderCreated`, `PaymentReceived`).

## Alternatives
- Direct HTTP calls from Orders to Billing
- Shared database tables

## Consequences
- Pros: Loose coupling, easier independent deployment
- Cons: Harder debugging, eventual consistency

Your one-page context anchor doesn’t repeat every ADR. Instead, it:

• Lists the most critical ADRs
• Summarizes them in a single line each
• Links to the full ADR files for deep dives

Example block in the anchor:

### Key Architecture Decisions

- ADR-003: Event-based communication between billing and orders (via message bus)
- ADR-005: React Query for server state, Redux Toolkit only for global UI state
- ADR-007: Feature-first module structure by domain (auth, billing, orders)

Now when someone wonders “Why is this so decoupled and event-driven?”, they have a direct answer and a link.

Centralizing Context: Architecture, Modules, Decisions

The real strength of the context anchor is centralization.

Instead of scattering:

• Architecture diagrams in a slide deck
• Module explanations in random READMEs
• Decisions in forgotten docs folders

…you surface the entry points on a single page.

That page becomes the table of contents for understanding the system:

• Architecture section → “How does this thing hang together?”
• Module map → “Where should I look for X?”
• ADR summary → “Why is it like this?”
• Change entry points → “What file do I open to get started?”

For AI workflows, this is gold. You can:

• Paste the context anchor as the first part of a prompt
• Ask the AI to respect module boundaries and decisions listed there
• Get changes localized to the right module, not scattered across the repo

This mirrors how you’d onboard a human teammate: start with context, then point them to the right spot.

Context as a First-Class Tool in Modern Workflows

Both humans and AI struggle with the same limitation: they can’t read everything first.

• Developers don’t have days to scan every folder
• AI models have token limits and context windows

Effective work today requires localized, high-quality context:

• “Here’s how this system is organized.”
• “Here’s where you should make this change.”
• “Here are the constraints that must be respected.”

A one-page context anchor operationalizes this idea.

It turns context into a tool rather than an accident:

• Easy to update when architecture changes
• Easy to share with new team members
• Easy to feed into AI tools

And because it’s short and focused, it’s much more likely to stay up to date than sprawling documentation.

How to Create Your Own One-Page Context Anchor

You can start small and iterate. A simple template:

# Project Context Anchor

## 1. What this system does
One short paragraph.

## 2. High-level architecture
- Main subsystems
- How they communicate

## 3. Module organization
- Key directories / packages and what they own
- Important boundaries and “must nots”

## 4. Key architecture decisions
- Bullet list of ADRs with one-line summaries + links

## 5. Common changes and where to make them
- “To change X, go to Y and do Z.”

## 6. Run & test (optional)
- The 2–3 most common commands and scenarios.

Put this file somewhere obvious, like CONTEXT.md or ARCHITECTURE.md in the repo root, and link to it from README.md.

Update it when:

• You introduce a new domain or subsystem
• You significantly rearrange modules
• You add a major ADR

Tiny updates keep it trustworthy and invaluable.

Conclusion

Complex JavaScript codebases aren’t going away. But getting lost in them doesn’t have to be part of the job.

A one-page context anchor gives you:

• A quick, high-level snapshot of the system
• A clear map of modules and responsibilities
• A curated view of critical architectural decisions
• Direct guidance on where to work for common changes

By centralizing architecture, module organization, and ADRs in one place, you enable both developers and AI tools to operate productively without reading everything first.

Treat context as a first-class citizen in your workflow. Start with a single page. Keep it sharp, honest, and current.

Your future self—and your teammates—will thank you every time they open a new repo and don’t get lost.