diff --git a/headless/lib/browser/protocol/target_handler.cc b/headless/lib/browser/protocol/target_handler.cc
index 548be825e526b..55f3054bc4a45 100644
--- a/headless/lib/browser/protocol/target_handler.cc
+++ b/headless/lib/browser/protocol/target_handler.cc
@@ -8,6 +8,9 @@
 #include <string_view>
 
 #include "build/build_config.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents.h"
 #include "headless/lib/browser/headless_browser_context_impl.h"
 #include "headless/lib/browser/headless_browser_impl.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
@@ -110,6 +113,19 @@ Response TargetHandler::CreateTarget(
     HeadlessWebContentsImpl* web_contents_impl = HeadlessWebContentsImpl::From(
         context->CreateWebContentsBuilder().SetInitialURL(gurl).Build());
 
+    // The hidden target hosts a `window.cdp` binding wired to a trusted
+    // browser-level DevTools session. Its siteless about:blank navigation
+    // never reaches SetIsUsed(), so the process would otherwise be treated as
+    // a freely-reusable allows-any-site host and unrelated web content could
+    // be co-scheduled with it at the process limit. Mark the process used so
+    // IsSuitableHost() rejects it for sites that require a dedicated process.
+    // (Mirrors content::HiddenTargetManager, which the headless embedder layer
+    // bypasses by handling Target.createTarget itself.)
+    web_contents_impl->web_contents()
+        ->GetPrimaryMainFrame()
+        ->GetProcess()
+        ->SetIsUsed();
+
     *out_target_id = content::DevToolsAgentHost::GetOrCreateFor(
                          web_contents_impl->web_contents())
                          ->GetId();