Zola "Failed to render" Tera template error in CI

Zola uses the Tera template engine. A "Failed to render" Reason means Tera hit an undefined variable, an unknown filter, or a bad block while producing a page, and the build stops.

What this error means

zola build reports "Reason: Failed to render 'X.html'" with a Tera message such as "Variable Y not found in context" or "Filter Z not found".

zola

Reason: Failed to render 'page.html'
Reason: Variable `page.autor` not found in context while rendering 'page.html'

Common causes

An undefined variable in the template

The template reads a field (a typo like autor, or optional frontmatter) that is not in the render context.

An unknown or misspelled filter

The template pipes through a filter name Tera does not provide, so rendering fails.

How to fix it

Default the variable or fix the name

Use a default filter or correct the field name so Tera always resolves it.

templates/page.html

{{ page.author | default(value=config.author) }}

Use a filter Tera supports

Check the filter name against Tera's built-ins or your registered ones.
Replace the unknown filter with a valid one.
Re-run zola build to confirm the render succeeds.

How to prevent it

Default optional frontmatter in templates.
Verify filter names against Tera built-ins.
Keep frontmatter field names consistent across content.