diff --git a/chrome/browser/chrome_browser_interface_binders.cc b/chrome/browser/chrome_browser_interface_binders.cc
index 7e78d75860689..5d822606d5df5 100644
--- a/chrome/browser/chrome_browser_interface_binders.cc
+++ b/chrome/browser/chrome_browser_interface_binders.cc
@@ -121,6 +121,17 @@
 #include "third_party/blink/public/mojom/webshare/webshare.mojom.h"
 #endif
 
+// --- POC INSTRUMENTATION (observation only) --------------------------------
+// On Linux there is no production ShareService receiver. Register a logging
+// stub so we can OBSERVE that an http(s) page sends a file: URL across the
+// renderer→browser Mojo boundary. This does not change any check; it only
+// records what the unmodified renderer sends.
+#if BUILDFLAG(IS_LINUX)
+#include "mojo/public/cpp/bindings/self_owned_receiver.h"
+#include "third_party/blink/public/mojom/webshare/webshare.mojom.h"
+#endif
+// ---------------------------------------------------------------------------
+
 #if BUILDFLAG(ENABLE_SPEECH_SERVICE)
 #include "chrome/browser/accessibility/live_caption/live_caption_speech_recognition_host.h"
 #include "chrome/browser/accessibility/live_caption/live_caption_unavailability_notifier.h"
@@ -361,6 +372,38 @@ void BindOnDeviceSpeechRecognitionHandler(
       ->Bind(std::move(receiver));
 }
 
+// --- POC INSTRUMENTATION (observation only) --------------------------------
+#if BUILDFLAG(IS_LINUX)
+class PocLinuxShareServiceLogger : public blink::mojom::ShareService {
+ public:
+  explicit PocLinuxShareServiceLogger(content::RenderFrameHost* rfh)
+      : last_committed_(rfh ? rfh->GetLastCommittedURL() : GURL()) {}
+  void Share(const std::string& title,
+             const std::string& text,
+             const GURL& share_url,
+             std::vector<blink::mojom::SharedFilePtr> files,
+             ShareCallback callback) override {
+    LOG(ERROR) << "POC-OBSERVE [browser process] ShareService::Share"
+               << " from page=" << last_committed_
+               << " share_url=" << share_url
+               << " scheme=" << share_url.scheme()
+               << " SchemeIsFile=" << share_url.SchemeIsFile();
+    std::move(callback).Run(blink::mojom::ShareError::CANCELED);
+  }
+
+ private:
+  const GURL last_committed_;
+};
+
+void BindPocLinuxShareServiceLogger(
+    content::RenderFrameHost* rfh,
+    mojo::PendingReceiver<blink::mojom::ShareService> receiver) {
+  mojo::MakeSelfOwnedReceiver(
+      std::make_unique<PocLinuxShareServiceLogger>(rfh), std::move(receiver));
+}
+#endif  // BUILDFLAG(IS_LINUX)
+// ---------------------------------------------------------------------------
+
 #if BUILDFLAG(IS_WIN)
 void BindMediaFoundationPreferences(
     content::RenderFrameHost* frame_host,
@@ -529,6 +572,11 @@ void PopulateChromeFrameBinders(
   map->Add<blink::mojom::ShareService>(
       &ForwardToJavaWebContents<blink::mojom::ShareService>);
 #endif
+// --- POC INSTRUMENTATION (observation only) --------------------------------
+#if BUILDFLAG(IS_LINUX)
+  map->Add<blink::mojom::ShareService>(&BindPocLinuxShareServiceLogger);
+#endif
+// ---------------------------------------------------------------------------
 
   map->Add<network_hints::mojom::NetworkHintsHandler>(&BindNetworkHintsHandler);
   map->Add<media::mojom::OnDeviceSpeechRecognition>(