E802 - Undefined template variable

Cause

Rendering a template hit a variable (or a key/attribute on a nested structure) that is not defined. Rendering is strict: undefined values are errors, never silent empty output.

Example

{ template_file: "header.elements.json.j2", with: { titel: "oops" } }

(Declared params catch this typo earlier as E804; E802 fires for undeclared variables and for missing keys inside nested with: values, e.g. {{ team.members }} when an item has no members.)

How to fix

Add the variable to the with: block, give the param a default in the template's front-matter, or fix the structure of the nested value passed in.