diff --git a/Cargo.toml b/Cargo.toml
index 267e1e81..5929c968 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -92,6 +92,7 @@ web-sys = { version = "=0.3.85", features = [
     "Document",
     "Element",
     "HtmlAnchorElement",
+    "HtmlIFrameElement",
     "Blob",
     "File",
     "FileSystemDirectoryHandle",
diff --git a/src/app/update/mod.rs b/src/app/update/mod.rs
index dfc7f9e5..ff942962 100644
--- a/src/app/update/mod.rs
+++ b/src/app/update/mod.rs
@@ -877,19 +877,26 @@ impl OpenCADStudio {
                     // Reply with the active drawing as ASCII DXF (the editor's
                     // export format regardless of the on-disk format). An empty
                     // reply tells the CMMS read tool the buffer isn't ready.
-                    let dxf = self
-                        .tabs
-                        .get(self.active_tab)
-                        .and_then(|tab| {
-                            crate::io::save_to_bytes(
-                                &tab.scene.document,
-                                "dxf",
-                                tab.scene.document.version,
-                            )
-                            .ok()
-                        })
-                        .map(|bytes| String::from_utf8_lossy(&bytes).into_owned())
-                        .unwrap_or_default();
+                    let dxf = match self.tabs.get(self.active_tab).map(|tab| {
+                        crate::io::save_to_bytes(
+                            &tab.scene.document,
+                            "dxf",
+                            tab.scene.document.version,
+                        )
+                    }) {
+                        Some(Ok(bytes)) => String::from_utf8_lossy(&bytes).into_owned(),
+                        Some(Err(e)) => {
+                            self.command_line.push_error(
+                                crate::tf!("AI Assistant: could not read the drawing: {e}").as_ref(),
+                            );
+                            String::new()
+                        }
+                        None => String::new(),
+                    };
+                    web_sys::console::log_1(&wasm_bindgen::JsValue::from_str(&format!(
+                        "[cmms-ai-bridge] poll: want_read, replying {} bytes DXF",
+                        dxf.len()
+                    )));
                     crate::sys::reply_ai_editor_buffer(&dxf);
                 }
                 if let Some(dxf) = apply {
diff --git a/src/sys.rs b/src/sys.rs
index 30ee3c48..e80a947d 100644
--- a/src/sys.rs
+++ b/src/sys.rs
@@ -560,7 +560,11 @@ mod ai_editor_bridge {
 
     struct State {
         listener: Option<Closure<dyn FnMut(web_sys::MessageEvent)>>,
-        reply_to: Option<web_sys::Window>,
+        // The chat iframe's Window, kept as a raw JsValue: it comes from
+        // another realm (the <iframe>), so `instanceof Window` / `dyn_into`
+        // would fail - we only ever call `.postMessage()` on it, which works
+        // cross-realm.
+        reply_to: Option<JsValue>,
         want_read: bool,
         pending_apply: Option<String>,
     }
@@ -574,6 +578,10 @@ mod ai_editor_bridge {
         }) };
     }
 
+    fn log(msg: &str) {
+        web_sys::console::log_1(&JsValue::from_str(&format!("[cmms-ai-bridge] {msg}")));
+    }
+
     fn str_field(obj: &JsValue, key: &str) -> Option<String> {
         js_sys::Reflect::get(obj, &JsValue::from_str(key))
             .ok()?
@@ -601,7 +609,8 @@ mod ai_editor_bridge {
                             &JsValue::from_str("source"),
                         )
                         .ok()
-                        .and_then(|s| s.dyn_into::<web_sys::Window>().ok());
+                        .filter(|s| !s.is_null() && !s.is_undefined());
+                        log(&format!("get-buffer received (source={})", source.is_some()));
                         STATE.with(|state| {
                             let mut state = state.borrow_mut();
                             state.reply_to = source;
@@ -613,6 +622,7 @@ mod ai_editor_bridge {
                             return;
                         }
                         if let Some(new_source) = str_field(&data, "new_source") {
+                            log(&format!("apply received ({} bytes)", new_source.len()));
                             STATE.with(|state| {
                                 state.borrow_mut().pending_apply = Some(new_source);
                             });
@@ -625,6 +635,7 @@ mod ai_editor_bridge {
                 .add_event_listener_with_callback("message", cb.as_ref().unchecked_ref());
             state.listener = Some(cb);
         });
+        log("message listener installed");
     }
 
     /// Drain any queued bridge requests: `(a read was asked for, a buffer to apply)`.
@@ -639,27 +650,45 @@ mod ai_editor_bridge {
     }
 
     /// Post the current drawing (ASCII DXF) back to the chat iframe that asked.
+    /// Also broadcasts to the embedded chat iframe found in the DOM, in case
+    /// `event.source` was unusable.
     pub fn reply_buffer(dxf: &str) {
-        STATE.with(|state| {
-            let Some(target) = state.borrow_mut().reply_to.take() else {
-                return;
-            };
-            let message = js_sys::Object::new();
-            let _ = js_sys::Reflect::set(
-                &message,
-                &JsValue::from_str("type"),
-                &JsValue::from_str("cmms-ai-editor-buffer"),
-            );
-            let _ = js_sys::Reflect::set(
-                &message,
-                &JsValue::from_str("buffer"),
-                &JsValue::from_str(dxf),
-            );
-            let origin = web_sys::window()
-                .and_then(|w| w.location().origin().ok())
-                .unwrap_or_else(|| "*".to_string());
-            let _ = target.post_message(&message, &origin);
-        });
+        let message = js_sys::Object::new();
+        let _ = js_sys::Reflect::set(
+            &message,
+            &JsValue::from_str("type"),
+            &JsValue::from_str("cmms-ai-editor-buffer"),
+        );
+        let _ = js_sys::Reflect::set(
+            &message,
+            &JsValue::from_str("buffer"),
+            &JsValue::from_str(dxf),
+        );
+        let origin = web_sys::window()
+            .and_then(|w| w.location().origin().ok())
+            .unwrap_or_else(|| "*".to_string());
+
+        let mut posted = false;
+        if let Some(target) = STATE.with(|state| state.borrow_mut().reply_to.take()) {
+            if target
+                .unchecked_ref::<web_sys::Window>()
+                .post_message(&message, &origin)
+                .is_ok()
+            {
+                posted = true;
+            }
+        }
+        // Fallback: post straight to the embedded chat iframe's contentWindow.
+        if let Some(frame_win) = web_sys::window()
+            .and_then(|w| w.document())
+            .and_then(|d| d.query_selector("#ai-assistant-editor-embed iframe").ok().flatten())
+            .and_then(|el| el.dyn_into::<web_sys::HtmlIFrameElement>().ok())
+            .and_then(|f| f.content_window())
+        {
+            let _ = frame_win.post_message(&message, &origin);
+            posted = true;
+        }
+        log(&format!("reply_buffer: {} bytes, delivered={}", dxf.len(), posted));
     }
 }