<!--
title: Config schema defaults
domain: devtools
topic: Configurations
language: Yaml
source: mermaid-js/mermaid
updated: 2024-02-01
url: https://awesomereviewers.com/reviewers/mermaid-config-schema-defaults/
-->

When updating configuration schemas, ensure each config option is fully specified and not redundantly redefined.

Apply these rules:
1) **Always set `type` and `default` for new properties** so downstream consumers get predictable behavior and the schema remains type-correct.
2) **Use inheritance from base config definitions** (`$defs` / `allOf`) and **remove redundant properties** that are already provided by the base schema—only override when behavior truly differs.
3) **Keep `default` consistent with the declared `type`** and (when you’re standardizing UX) align defaults across related diagram configs.

Example (pattern):
```yaml
properties:
  markdownAutoWrap:
    type: boolean
    default: true

BlockDiagramConfig:
  title: Block Diagram Config
  allOf: [{ $ref: '#/$defs/BaseDiagramConfig' }]
  description: The object containing configurations specific for block diagrams.
  type: object
  unevaluatedProperties: false
  properties:
    padding:
      type: number
      default: 8
# Note: don’t re-declare useMaxWidth here if BaseDiagramConfig already defines it with the desired default.
```