Discourse Horizon Topic Thumbnails

[satonotdead]

	Summary	Adds topic thumbnails to Horizon’s high context topic cards
	Repository	GitHub - criptonautas/discourse-horizon-topic-thumbnails: Topic thumbnails on Horizon's high context topic cards · GitHub
	Install Guide	How to install a theme or theme component
	New to Discourse Themes?	Beginner’s guide to using Discourse Themes

Install this theme component

Adds thumbnails to Horizon’s high context topic cards without forking or editing Horizon. Disabling or removing the component fully reverts the change.

Live screenshots

Desktop with the setting compact last reply enabled:

Mobile with the image on top:

What it does

• Shows the topic’s image on the trailing edge of each card.
• On phones, shows it as a banner above the card.
• Keeps a placeholder for topics with no image, so cards stay uniform.
• Optionally moves the last-reply pill into the footer row to keep cards shorter.
• Loads a size that fits the screen, so a topic list doesn’t download every original image.

It also works alongside Horizon AI Gists.

Requirements

• Horizon with high context topic cards enabled
• Site setting create thumbnails enabled
• Discourse 2026.5.0 or later

Don’t install it alongside the official Topic List Thumbnails component: it’s not needed, and the two conflict on Horizon’s cards.

Settings

Setting	Default
thumbnail_size	240	Thumbnail column width, from 100 to 400 px
mobile_thumbnails	true	Show the banner on phones
placeholder_icon	comments	Icon for topics with no image
placeholder_background	none	Image behind the placeholder
compact_last_reply	true	Keep cards shorter by moving the last-reply pill
enabled_categories	empty	Limit thumbnails to these categories; subcategories aren’t included

Known limits

• It depends on Horizon’s class and column names. If those change, thumbnails may stop showing or parts of the card may shift until the component is updated.
• Existing topics may show the original image or the placeholder until their sizes are generated in the background.

Tested with a Meta member’s feedback and privately in our commmunity. Bug reports and PRs are welcome.