--- a/src/whitenoise/event_processor/account_event_processor.rs
+++ b/src/whitenoise/event_processor/account_event_processor.rs
@@ -178,7 +178,22 @@
             }
             Err(e) => {
                 // Handle retry logic for actual processing errors
-                if retry_info.should_retry() {
+                // marmot-interop-headless patch: MLS errors that come from
+                // mdk are ALREADY terminal — mdk doesn't retry internally, so
+                // any Err it returns (Unprocessable, PreviouslyFailed, decrypt
+                // failure, group-not-found, etc.) is provably permanent.
+                // Retrying those 10 times with exponential backoff (total
+                // ~17 min) just blocks later decryptable commits behind a
+                // queue of doomed retries, so every later join / rename /
+                // leave propagation races the test timeout. Treat them all
+                // as one-shot: log once, move on.
+                let is_terminal = matches!(
+                    e,
+                    WhitenoiseError::MlsMessageUnprocessable(_)
+                        | WhitenoiseError::MlsMessagePreviouslyFailed
+                        | WhitenoiseError::MdkCoreError(_),
+                );
+                if !is_terminal && retry_info.should_retry() {
                     self.schedule_retry(event, source, retry_info, e);
                 } else {
                     tracing::error!(