diff --git a/src/README.md b/src/README.md
index 286560135..cb2f9fc7c 100644
--- a/src/README.md
+++ b/src/README.md
@@ -29,7 +29,7 @@ Mintlify-flavoured MDX build (see `src/plugins/vite-mintlify-snippets.ts` and
 | `DOCS_LOCALE` | A singular locale build (`en`, `es`, `pt-BR`, and so on); normally set only by the Vercel shard orchestrator. |
 | `DOCS_LOCALES` | Translations included in a `translations` or legacy `combined` artifact: `none`, `all`, or a comma-separated list such as `es,fr`. The translations project uses `all`. |
 | `DOCS_REMOTES` | Registered remote-source scope: `none` for an ordinary base-repository preview and `all` for source previews, production, and a base preview carrying `docs-preview-show-remotes`. |
-| `DOCS_REMOTE_NAME`, `DOCS_REMOTE_REPOSITORY`, `DOCS_REMOTE_REF` | CI-only tuple selecting one registered remote at an immutable commit for an English pull-request preview. |
+| `DOCS_REMOTE_NAME`, `DOCS_REMOTE_REPOSITORY`, `DOCS_REMOTE_REF` | CI-only tuple selecting one registered remote at an immutable commit for an English source pull-request preview. Required for that `connect-preview` mode; a trusted base preview with `docs-preview-show-remotes` instead uses `DOCS_REMOTES=all`. |
 | `DOCS_REMOTE_SOURCE_REPOSITORY` | CI-derived PR-head repository, retained only for preview attribution and edit links. It defaults to the registered repository. |
 | `DOCS_REMOTE_PULL_REQUEST_REF` | CI-only base-repository PR ref (`refs/pull/<number>/head`) to fetch and verify against `DOCS_REMOTE_REF`. |
 | `DOCS_REMOTES_PREFETCHED=1` | Requires the remote mounts and fetch-state files supplied by the credentialed CI fetch job. |
diff --git a/src/lib/scope.ts b/src/lib/scope.ts
index d7150ce95..d74c4c157 100644
--- a/src/lib/scope.ts
+++ b/src/lib/scope.ts
@@ -299,6 +299,16 @@ export function readScope(root = process.cwd()): BuildScope {
       )
     : parseRemotePreview(fileScope?.remotePreview, ".preview-scope.json remotePreview");
 
+  // connect-preview has two trusted modes: a source-PR preview with one
+  // immutable remote tuple, or a base-repository preview that explicitly
+  // requests every registered remote through its workflow-controlled scope.
+  const showAllRemotesPreview =
+    !hasRemoteEnvironment && envRemotes.toLowerCase() === "all";
+  if (vercelTarget === "connect-preview" && !remotePreview && !showAllRemotesPreview) {
+    throw new Error(
+      "Vercel connect-preview builds require DOCS_REMOTE_NAME, DOCS_REMOTE_REPOSITORY and DOCS_REMOTE_REF, or DOCS_REMOTES=all",
+    );
+  }
   if (remotePreview && (locale !== "en" || locales.length > 0)) {
     throw new Error("Remote pull-request previews are English-only; omit DOCS_LOCALES");
   }