X_ISLAND_NOT_HYDRATED
Means
a page renders an island nothing would boot
Typical cause
three causes, and the cause says which. (1) the route states hydrate: 'never' beside an island — a contradiction the author wrote on purpose, since a route carrying one otherwise derives its own. (2) the island() call sits below the defineRoute that drains it, so the declaration had not happened yet. (3) the page was rendered outside a render that collects islands, so no hydration runtime is emitted and the chunk is never requested — this is the host's wiring, not the author's page
Fix
(1) drop the explicit hydrate: 'never' and let it derive · (2) move the island() call above defineRoute · (3) render through renderToHtml(tree, { islands: islandCollector({ file, hydrate }) }) so the island is counted, booted and budgeted