diff --git a/rust/strawcore/src/net.rs b/rust/strawcore/src/net.rs
index b95a13424..18ae2c6d9 100644
--- a/rust/strawcore/src/net.rs
+++ b/rust/strawcore/src/net.rs
@@ -80,9 +80,14 @@ pub(crate) async fn read_capped_body(resp: reqwest::Response, cap: usize) -> Opt
         }
         buf.extend_from_slice(&chunk);
     }
-    // Lossy decode: a strict from_utf8 would drop the whole response on a
-    // single mojibake byte; serde_json tolerates U+FFFD in string values.
-    Some(String::from_utf8_lossy(&buf).into_owned())
+    // Prefer a zero-copy move on valid UTF-8 (the common case); fall back to a
+    // lossy copy only on a mojibake byte (a strict from_utf8 would otherwise
+    // drop the whole response — serde_json tolerates U+FFFD in string values).
+    // Mirrors the core downloader's default_impl fast path (S4).
+    Some(match String::from_utf8(buf) {
+        Ok(s) => s,
+        Err(e) => String::from_utf8_lossy(e.as_bytes()).into_owned(),
+    })
 }
 
 // ---------------------------------------------------------------------------