Short answer: No—this tag is valid in Prefect 3.x. Prefect tags are plain strings with no character restrictions, so spaces, ampersands (&), parentheses, periods, and colons are all allowed. The exact string you provided would be treated as-is. A couple of practical notes: - If you use this tag in the CLI, wrap it in quotes so the shell doesn’t interpret characters like

&

or spaces: - Example:

"2010 West End & Retail (55a834e3-84aa-4cc9-b58b-22108e6269da).xlsx"

- If you literally include the leading

tag:

(as in

tag:2010 West End & Retail (...)

), that prefix becomes part of the tag value. Tags are matched exactly. If you’re seeing an error when adding it, can you share where (UI, API, or CLI) and the exact message?