Keep proactive MCP image sanitization and restore InvalidImageRequest fallback

codex-rs/core/src/codex.rs

@@ -3937,10 +3937,7 @@ pub(crate) async fn run_turn(
                 error_or_panic(
                     "Invalid image detected; sanitizing tool output to prevent poisoning",
                 );
-                if state
-                    .history
-                    .replace_last_turn_images(NON_MULTIMODAL_IMAGE_PLACEHOLDER)
-                {
+                if state.history.replace_last_turn_images("Invalid image") {
                     continue;
                 }
                 let event = EventMsg::Error(ErrorEvent {

codex-rs/core/tests/suite/view_image.rs

@@ -597,9 +597,7 @@ async fn replaces_invalid_local_image_after_bad_request() -> anyhow::Result<()>
         "second request should replace the invalid image"
     );
     let user_texts = second_request.message_input_texts("user");
-    assert!(user_texts.iter().any(|text| {
-        text == "[there was an image here but it was removed for non-multimodal models]"
-    }));
+    assert!(user_texts.iter().any(|text| text == "Invalid image"));
 
     Ok(())
 }