The edge posts the open batch before a failed stream gives the group back

A plain stop and a chunk that doesn't inflate already posted the batch so far,
so the stop snapshot stood at a stored resume point; a failed stream (the
stalled one's "Peer disconnected") skipped the post, left the batch open and
lost the window with the snapshot refused. Now only a batch the coordinator
refused stays open.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

REBUILD.md

@@ -557,7 +557,10 @@ releases, a third of them one poster's image dump (27.7 M rows, LOG.md
    them in the corpus only, and the run leaves them there; a stream that
    looked at the corpus once, seconds before that store, waited its whole
    hour on the spool and the worker lost the group and its open batch
-   (three groups on the first morning).
+   (three groups on the first morning). A failed stream now posts the
+   open batch before the group goes back, like a stop does, so the
+   window's snapshot survives it; only a batch the coordinator refused
+   (lease lost, too large) still loses the window.
 
 6. **The corpus stays as it is.** Measured on 300 unfiltered chunks
    (30 M lines, LOG.md (102)): 43% of lines lack a "(k/N)" counter, and of

edge/README.md

@@ -248,8 +248,11 @@ COORDINATOR_URL=http://coordinator:3334 NODE_TOKEN=… ./target/release/edge-nod
   snapshot (bincode, gzip) goes to the coordinator every
   `--snapshot-minutes` (EDGE_SNAPSHOT_MINUTES, 30) right after a batch,
   and when the group is given back: caught up (`next` answers 204: the
-  tail), a stop, a lost lease or a failure; the next holder restores it
-  (`GET groups/:id/snapshot`) and continues at its article. `--groups N`
+  tail), a stop, a lost lease or a failure; a stop or a failed stream
+  posts the open batch first, so the snapshot stands at its resume point
+  (a batch the coordinator refused can't, and that window is lost); the
+  next holder restores it (`GET groups/:id/snapshot`) and continues at
+  its article. `--groups N`
   stops after N groups; `--ranges N` is the old per-range lease
   (`POST lease`), one range per thread without a carried window.
 - **As `commands/edge_node.ts`:** retries for network trouble and 5xx;

edge/src/bin/edge-node.rs

@@ -629,9 +629,10 @@ fn run_group_range(api: &Arc<Api>, group_id: i64, group_name: &str, range: Range
             }
         }
     }
-    // Stopped mid-range (or at a chunk that doesn't inflate): the batch so far goes out, so the snapshot stands at
-    // a stored resume point, and a chunk reported corrupt is read again from its own start.
-    if !reached_end && failure.is_none() && post_error.lock().unwrap().is_none() && indexer.next() > batch_from {
+    // Stopped mid-range (a stop, a stream that failed, a chunk that doesn't inflate): the batch so far goes out,
+    // so the snapshot stands at a stored resume point and the window survives the group going back; a chunk
+    // reported corrupt is read again from its own start. Only a batch the coordinator refused stays open.
+    if !reached_end && post_error.lock().unwrap().is_none() && indexer.next() > batch_from {
         let _ = post_tx.send(indexer.take());
     }
     drop(post_tx);