A good internal dev-doc structure could be:

Internal Developer Documentation

1. Overview

Purpose of the system, who it is for, and the main mental model.

Include:

What the product/system does

Key domains/concepts

High-level architecture diagram

Main repositories/services/packages

Links to local setup, production dashboards, and issue trackers

2. Architecture

This should be near the top, as you suggested.

2.1 System Architecture

Explain the system at a high level:

Major apps/services

Client/server boundaries

Storage layers

External dependencies

Runtime environments

2.2 Dataflows

Very useful as its own major subsection.

Examples:

“User creates a document”

“Content syncs between peers”

“Identity/auth flow”

“Publishing flow”

“Search/indexing flow”

“Import/export flow”

Each dataflow should ideally include:

Trigger

Components involved

Step-by-step sequence

Data written/read

Failure cases

Relevant files/modules

2.3 Components

Component-by-component reference.

For each component:

## Component Name

### Responsibility
What this component owns.

### Inputs
What it receives.

### Outputs
What it produces.

### Dependencies
Other components/services it relies on.

### Key files
Important files/directories.

### Lifecycle
When/how it starts, updates, shuts down.

### Known gotchas
Things future devs should know.

3. Development Setup

Practical onboarding section.

Include:

Prerequisites

Installing dependencies

Environment variables

Running locally

Common dev commands

Resetting local state

Seeding test data

Troubleshooting setup issues

4. Codebase Guide

A map of the repository.

Example:

/apps
  /desktop
  /web
/packages
  /core
  /ui
  /sync
  /db
/tools
/docs

For each major directory, explain:

What belongs here

What should not go here

Important conventions

Entry points

5. Core Concepts

This is where you define project-specific ideas.

For Seed Hypermedia, this might include things like:

Documents

Blocks

Entities

Accounts/identity

Hypermedia links

Versions/history

Sync state

Local-first state

Publishing

Each concept should answer:

What is it?

Why does it exist?

Where is it represented in code?

How does it move through the system?

6. APIs and Interfaces

Document internal and external APIs.

Include:

Public APIs

Internal service interfaces

RPC methods

Event/message schemas

Database schemas

Type definitions

Error formats

Good pattern:

## API / Method Name

### Purpose
### Request/input
### Response/output
### Side effects
### Errors
### Example
### Related files

7. Storage and Data Model

A dedicated section for persistence.

Include:

Database schema

Local storage layout

File storage

Cache layers

Indexes

Migrations

Backup/restore

Data ownership rules

8. Sync, Networking, and State

Especially important if the system is distributed or local-first.

Include:

Source of truth

Conflict resolution

Offline behavior

Peer/server communication

Retry behavior

Consistency guarantees

Debugging sync issues

9. Testing

Include:

Test strategy

Unit tests

Integration tests

End-to-end tests

Fixtures

Mocks

How to run tests

How to add tests

Known gaps

10. Debugging and Observability

Practical operational docs.

Include:

Logs

Metrics

Tracing

Debug flags

Devtools

Common failure modes

How to inspect local DB/state

Production debugging checklist

11. Build, Release, and Deployment

Include:

Build pipeline

CI/CD

Versioning

Release checklist

Deployment environments

Rollback process

Feature flags

Platform-specific notes

12. Security and Permissions

Include:

Auth model

Permissions model

Secrets

Sensitive data handling

Threat model notes

Common security mistakes

13. Conventions and Patterns

This keeps the codebase consistent.

Include:

Naming conventions

Error handling

State management patterns

Logging conventions

Folder conventions

Dependency rules

UI patterns

API design rules

14. Runbooks

For recurring operational tasks.

Examples:

“How to debug broken sync”

“How to recover from corrupted local state”

“How to inspect a user document”

“How to rotate credentials”

“How to ship a release”

“How to migrate data”

15. Decision Records

Use ADRs: Architecture Decision Records.

Structure:

# ADR 001: Use X for Y

## Status
Accepted / Proposed / Deprecated

## Context
## Decision
## Consequences
## Alternatives considered

This is valuable because internal docs should explain why things are the way they are, not only what exists.

Suggested top-level order

Your instinct is good. I’d structure it like this:

# Internal Dev Documentation

1. Overview
2. Architecture
   2.1 System Architecture
   2.2 Dataflows
   2.3 Components
3. Development Setup
4. Codebase Guide
5. Core Concepts
6. APIs and Interfaces
7. Storage and Data Model
8. Sync, Networking, and State
9. Testing
10. Debugging and Observability
11. Build, Release, and Deployment
12. Security and Permissions
13. Conventions and Patterns
14. Runbooks
15. Architecture Decision Records

For the top of the docs, I’d use this exact order:

# Internal Dev Documentation

## Overview
## Architecture
## Dataflows
## Components

But I’d make Dataflows and Components subsections under Architecture unless they become large enough to deserve their own top-level pages.