Shared fields

These limits apply when a topic is published and when it is edited. The screen is Add topic / branch. Which type may omit a field is Topic types.

Field	Rule
topic_type	One of the eight slugs.
title	15–280 characters. Unique.
subtitle	15–280 characters. Unique.
body	Prose 50–5000 characters. Argument and graph 50–20000. Unique. Whitespace does not count toward a minimum.
tags	Exactly 3. After normalize: lowercase letters and digits, length 1–40, duplicates dropped.
branches	Seeded array. options is accepted as the same key. Branch body is 1–280 characters. Branch description is 0–2000. A context index title uses a product minimum of 10.
expires_at	A duration token: 7d, 13d, 30d, 90d, 180d, 365d, 730d. Poll stops at 30d.

A URL is not a length field. Adding one is Context links.