X_TEST_ISLAND_NOT_BUILT

the island build produced no chunk for the file the test named

mountIsland was given a file the builder never produced — a path relative to the test instead of to the app root, a typo, or an island outside apps/*/{site,app,shared}/**/*.island.tsx. One symptom, three different edits, so cause lists what the build DID produce; an empty list means the glob found nothing under this root at all

copy a path the cause lists into file: — it is app-root-relative — or, when nothing was built, x g island <name> --at apps/web/site and point root at the directory holding apps/