When updating an artifact that has been shared (via the claude.ai share menu) but the shared version is not the latest, Claude now surfaces a warning in the tool result:
"This artifact is shared, and viewers are pinned to an older version — they will not see this update until the user moves the shared version forward from the page's share menu."
Evidence
Shared artifact notice (search for "viewers are pinned to an older version")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.