diff --git a/src/lib/onboard.ts b/src/lib/onboard.ts
index e983b712d5c..7f156a8279b 100644
--- a/src/lib/onboard.ts
+++ b/src/lib/onboard.ts
@@ -4327,6 +4327,11 @@ async function onboard(opts = {}) {
   if (!noticeAccepted) {
     process.exit(1);
   }
+  // Validate NEMOCLAW_PROVIDER early so invalid values fail before
+  // preflight (Docker/OpenShell checks). Without this, users see a
+  // misleading 'Docker is not reachable' error instead of the real
+  // problem: an unsupported provider value.
+  getRequestedProviderHint();
   const lockResult = onboardSession.acquireOnboardLock(
     `nemoclaw onboard${resume ? " --resume" : ""}${isNonInteractive() ? " --non-interactive" : ""}${requestedFromDockerfile ? ` --from ${requestedFromDockerfile}` : ""}`,
   );