diff --git a/extensions/browser/script_executor.cc b/extensions/browser/script_executor.cc
index ea557e103e17e..a47ab472680fe 100644
--- a/extensions/browser/script_executor.cc
+++ b/extensions/browser/script_executor.cc
@@ -14,6 +14,7 @@
 #include "base/dcheck_is_on.h"
 #include "base/functional/bind.h"
 #include "base/hash/hash.h"
+#include "base/logging.h"
 #include "base/memory/raw_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/pickle.h"
@@ -208,6 +209,13 @@ class Handler : public content::WebContentsObserver {
       return content::RenderFrameHost::FrameIterationAction::kContinue;
     }
 
+    // ---- POC instrumentation (observation only, does not change logic) ----
+    LOG(ERROR) << "[POC][MaybeAddSubFrame] ext=" << host_id_.id
+               << " process=" << frame->GetProcess()->GetDeprecatedID()
+               << " url=" << frame->GetLastCommittedURL()
+               << " is_error_doc=" << frame->IsErrorDocument();
+    // ----------------------------------------------------------------------
+
     if (!is_web_view_ &&
         host_id_.type == mojom::HostID::HostType::kExtensions) {
       // TODO(crbug.com/502262220): We do permission checks in at least three
@@ -216,10 +224,13 @@ class Handler : public content::WebContentsObserver {
       std::string error;
       if (!scripting::HasPermissionToInjectIntoFrame(
               *extension->permissions_data(), tab_id, frame, &error)) {
+        LOG(ERROR) << "[POC][MaybeAddSubFrame]   -> DENIED (no host perm): "
+                   << error;
         return content::RenderFrameHost::FrameIterationAction::kContinue;
       }
     }
 
+    LOG(ERROR) << "[POC][MaybeAddSubFrame]   -> PUSHED to pending_render_frames_";
     PushPendingRenderFrame(frame, ExtensionApiFrameIdMap::GetFrameId(frame));
     return content::RenderFrameHost::FrameIterationAction::kContinue;
   }
diff --git a/extensions/browser/script_injection_tracker.cc b/extensions/browser/script_injection_tracker.cc
index 282701b10bf17..7a3b2ef75fc80 100644
--- a/extensions/browser/script_injection_tracker.cc
+++ b/extensions/browser/script_injection_tracker.cc
@@ -8,6 +8,7 @@
 
 #include "base/check_is_test.h"
 #include "base/debug/crash_logging.h"
+#include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/raw_ref.h"
 #include "base/strings/string_number_conversions.h"
@@ -286,6 +287,17 @@ void HandleProgrammaticScriptInjection(
       RenderProcessHostUserData::GetOrCreate(*frame->GetProcess());
   process_data.AddScript(script_type, extension.id());
 
+  // ---- POC instrumentation (observation only) ----
+  LOG(ERROR) << "[POC][ScriptInjectionTracker] AddScript(ext="
+             << extension.id()
+             << ", process=" << frame->GetProcess()->GetDeprecatedID()
+             << ") via frame url=" << frame->GetLastCommittedURL()
+             << " is_error_doc=" << frame->IsErrorDocument()
+             << " -> DidProcessRunContentScriptFromExtension="
+             << ScriptInjectionTracker::DidProcessRunContentScriptFromExtension(
+                    *frame->GetProcess(), extension.id());
+  // ------------------------------------------------
+
   URLLoaderFactoryManager::WillProgrammaticallyInjectContentScript(
       pass_key, frame, extension);
 }