All three @corbits cores mounted on one Interchange host, sharing one database, one connection pool, and one identity decision. This is the configuration a real adopter reaches for, and the one the per-core reference hosts never covered.

The checks are about coexistence rather than per-core behaviour — the other module examples cover that:

• Migrations coexist. Three independent runners, three separate ledgers (corbits_mailbox_core_migrations, corbits_artifact_core_migrations, corbits_analytics_core_migrations), no shared table names. Order is not load-bearing: none of the three has a foreign key into another or into the host, so they can run in whatever order boot reaches them.
• One identity decision satisfies all three seams. The host answers "who is this request?" once. Note the two spellings: @corbits/mailbox-core takes { tenantId, principalId }, the other two still take { tenant, principal }. That is one decision rendered twice, not two decisions — see resolvePrincipal and resolveTenantPrincipal in @corbits/example-kit.
• Route surfaces do not collide. /api/me/inbox, /api/artifacts and /api/analytics/* each keep their own payloads after all three mounts, and the host's own /status still answers.
• A cross-core flow works. An agent's work is counted by analytics, its output is stored as an artifact, and a mailbox message announces it carrying the artifact id as a ref.

Only the migration ledgers are namespaced. The data tables are plain, unprefixed nouns — artifact, upload, analytics_event, principal_mail, mailbox. What keeps three cores from colliding is that they picked disjoint names, not a prefix convention protecting you. If your host already owns an artifact or an upload, that is a real conflict — and shared-schema-host shows the fix.

Where a core lands decides who gates it. Interchange declares app.use("/api/me/*", requireAuth), so the mailbox is refused by the host with a 401 that never reaches the core. Artifacts and analytics land on ungated prefixes and answer their own no-principal behaviour: an empty 200 on an aggregate read, 403 on anything naming a specific identity.

bun install                 # from the repo root
bun run start               # asserts, then exits
bun run serve               # the same app on a port

EXAMPLES_DATABASE_URL overrides the database. bun run start truncates all three cores' tables on every run.