diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 07cfed4..7e575b0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -122,13 +122,18 @@ jobs:
       - name: Build
         run: npm run build
 
-      # NODE_ENV=test keeps the dev-session bypass available on a production
-      # build (see allowDevBypass in src/lib/config.ts), so the authenticated
-      # sweep still runs instead of skipping itself.
+      # NODE_ENV stays "development" so the dev-session bypass is available on
+      # a production build (allowDevBypass in src/lib/config.ts) and the
+      # authenticated sweep runs instead of skipping itself.
+      #
+      # Not "test": Next deliberately skips .env.local under NODE_ENV=test, so
+      # the same command run on a developer's machine would start a server with
+      # no DATABASE_URL and report every migration missing — a confusing false
+      # failure. CI passes its database in through the job env either way.
       - name: Run E2E smoke suite
         run: npm run e2e
         env:
-          NODE_ENV: test
+          NODE_ENV: development
           E2E_SERVER_COMMAND: npm run start
 
       - name: Upload Playwright report
diff --git a/README.md b/README.md
index 5ec8d72..5862a59 100644
--- a/README.md
+++ b/README.md
@@ -702,9 +702,43 @@ Local demo mode is only available when `ESTATEOS_ENABLE_DEV_BYPASS=true`. It is
 Local development keeps the central-auth architecture easy to test:
 
 - `NEXT_PUBLIC_APP_URL`, `NEXT_PUBLIC_PLATFORM_BASE_URL`, and `NEXT_PUBLIC_PORTAL_BASE_URL` can all stay on localhost.
-- tenant public pages can still use `DEFAULT_COMPANY_SLUG` in development without requiring multi-domain DNS.
+- `DEFAULT_COMPANY_SLUG` gives signed-in areas (`/admin`, `/portal`) a tenant without multi-domain DNS. It does **not** apply to public pages — see below.
 - central auth redirect helpers collapse back to the same localhost origin when portal and platform share the same dev host.
 
+### Opening A Tenant Site Locally
+
+`npm run dev` and then http://localhost:3000 renders the **platform** marketing
+page, not a tenant site. That is correct behavior, not a broken database:
+public pages resolve the tenant from the **host**, and `DEFAULT_COMPANY_SLUG`
+is deliberately not consulted for them, so a fallback can never serve one
+tenant's public site on another host in production.
+
+Use either of these instead (the dev server also prints this hint, naming the
+companies present in your database, whenever it falls back to the platform page):
+
+```bash
+# 1. Query parameter — needs DEV_ACCESS_MODE=true in .env.local
+http://localhost:3000/?devTenant=acme-realty
+
+# 2. Tenant host — no env flag needed; *.localhost resolves to loopback in
+#    most browsers, otherwise add "127.0.0.1 acme-realty.localhost" to your
+#    hosts file
+http://acme-realty.localhost:3000
+```
+
+Option 1 is the intended day-to-day workflow. Option 2 is the closer match to
+production, because it exercises the same host-based resolution that a real
+tenant domain uses, and it is what the E2E suite drives.
+
+If the hint reports that no companies exist, the database simply has not been
+seeded:
+
+```bash
+createdb estateos_dev          # or: psql -c "CREATE DATABASE estateos_dev"
+npm run db:migrate:deploy      # applies prisma/migrations to that database
+npm run db:seed                # creates the acme-realty demo tenant
+```
+
 ## Database Setup (Supabase)
 
 ### 1. Create A Supabase Project
diff --git a/src/lib/tenancy/context.ts b/src/lib/tenancy/context.ts
index 85d5baf..b41a285 100644
--- a/src/lib/tenancy/context.ts
+++ b/src/lib/tenancy/context.ts
@@ -100,6 +100,70 @@ async function lookupCompany(
   return null;
 }
 
+/**
+ * Development-only guidance for the single most common local confusion:
+ * `npm run dev` + http://localhost:3000 renders the PLATFORM marketing site,
+ * not a tenant site, and the log line above ("no-tenant-host-match") does not
+ * say what to do about it.
+ *
+ * The reason is deliberate and must not be softened: public pages resolve the
+ * tenant from the HOST. DEFAULT_COMPANY_SLUG is applied to authenticated areas
+ * only (see `resolvedCompany` above), so it can never leak one tenant's public
+ * site onto another host in production. Locally that means the host has to
+ * name the tenant.
+ *
+ * Logged once per host per server process so it guides without spamming, and
+ * it names the companies actually present so a missing seed is obvious.
+ */
+const loggedTenantFallbackHosts = new Set<string>();
+
+async function logLocalTenantFallbackHint(host: string | null, devTenantSlug: string | null) {
+  if (featureFlags.isProduction) {
+    return;
+  }
+
+  const key = host ?? "(no host)";
+  if (loggedTenantFallbackHosts.has(key)) {
+    return;
+  }
+  loggedTenantFallbackHosts.add(key);
+
+  let knownSlugs: string[] = [];
+  if (featureFlags.hasDatabase) {
+    try {
+      const companies = await prisma.company.findMany({
+        select: { slug: true },
+        orderBy: { createdAt: "asc" },
+        take: 5,
+      });
+      knownSlugs = companies.map((company) => company.slug);
+    } catch {
+      // The hint is best-effort; a database problem is reported elsewhere.
+    }
+  }
+
+  const example = devTenantSlug ?? knownSlugs[0] ?? "<company-slug>";
+  const nextStep =
+    knownSlugs.length === 0
+      ? "This database has no companies yet — run `npm run db:seed` first."
+      : `Companies in this database: ${knownSlugs.join(", ")}.`;
+
+  logWarn(
+    `No tenant site matched host "${key}", so the platform marketing page is being rendered. ` +
+      "Public pages resolve the tenant from the host; DEFAULT_COMPANY_SLUG applies to signed-in areas only, " +
+      "which is why plain localhost never shows a tenant site. " +
+      `${nextStep} ` +
+      `To open a tenant site locally use http://localhost:3000/?devTenant=${example} ` +
+      `(needs DEV_ACCESS_MODE=true) or http://${example}.localhost:3000.`,
+    {
+      route: "/",
+      host: key,
+      step: "tenant-host-resolution",
+      knownCompanySlugs: knownSlugs,
+    },
+  );
+}
+
 export async function resolveCompanyForTenantHint(input: {
   companySlug?: string | null;
   host?: string | null;
@@ -285,6 +349,10 @@ async function resolveTenantContextUncached(
             ? "no-tenant-host-match"
             : null,
     });
+
+    if (!resolvedCompany) {
+      await logLocalTenantFallbackHint(host, devTenantSlug);
+    }
   }
 
   if (!session) {