You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
ArtifactsArea: what it touches
New FeaturesKind: in v2.1.251,
New FeaturesSection of the release
What
The instructions Claude follows when publishing an artifact now list a Thumbnail field, and the tool's summary counts how many were supplied, so a publish reports back that it included "a custom thumbnail image" or "two custom thumbnail images".
Details
Sits behind an internal capability check, so the field is only advertised when that check passes.
The count covers both the light and dark thumbnail.
Evidence
a custom thumbnail image
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
