Normalize recoverable rejection acknowledgements

tests/test_sync_error_classification.py

@@ -23,14 +23,18 @@ class SyncErrorClassificationTest(unittest.TestCase):
                 "generation_id TEXT,producer_peer_id TEXT,consumer_peer_id TEXT,"
                 "consumed_at TEXT,result TEXT,ack_json TEXT)"
             )
-            for generation, result in (("gen_consumed", "consumed"),
-                                       ("gen_rejected", "rejected"),
-                                       ("gen_other", "consumed")):
+            for generation, result, diagnostic in (
+                ("gen_consumed", "consumed", ""),
+                ("gen_rejected", "rejected", "bounded rejection"),
+                ("gen_legacy", "rejected", "legacy/path"),
+                ("gen_other", "consumed", ""),
+            ):
                 database.execute(
                     "INSERT INTO sync_consumed_generations VALUES(?,?,?,?,?,?)",
                     (generation, "android" if generation != "gen_other" else "other",
                      "desktop", generation, result,
-                     json.dumps({"generation_id": generation, "result": result})),
+                     json.dumps({"generation_id": generation, "result": result,
+                                 "diagnostic": diagnostic})),
                 )
 
             acknowledgements = sync_peer_worker.recovery_acknowledgements(

tools/sync_generation_exchange.py

@@ -566,6 +566,11 @@ def record_consumed(db: sqlite3.Connection, manifest: dict, manifest_digest: str
 
 
 def record_rejected(database: Path, manifest: dict, manifest_digest: str, diagnostic: str) -> dict:
+    # Android's platform JSON quoter escapes solidus characters while the
+    # desktop canonical encoder does not. Rejection diagnostics are bounded
+    # presentation text, so normalize that separator before hashing the ACK;
+    # identities and protocol fields remain untouched.
+    diagnostic = diagnostic.replace("/", ":")
     diagnostic = diagnostic.encode("utf-8")[:MAX_DIAGNOSTIC].decode("utf-8", "ignore")
     with closing(connect_database(database)) as db:
         require_schema(db); db.execute("BEGIN IMMEDIATE")

tools/sync_peer_worker.py

@@ -75,7 +75,15 @@ def recovery_acknowledgements(db, producer_peer_id: str, consumer_peer_id: str)
         "ORDER BY consumed_at,generation_id LIMIT 32",
         (producer_peer_id, consumer_peer_id),
     ).fetchall()
-    return [json.loads(row[0]) for row in rows]
+    acknowledgements = [json.loads(row[0]) for row in rows]
+    # ACKs created before rejection diagnostics were normalized may contain a
+    # solidus that Android's platform JSON canonicalizer hashes differently.
+    # They remain durable evidence but cannot close a peer row, so do not let
+    # one legacy object block recovery of later compatible conversations.
+    return [
+        value for value in acknowledgements
+        if value.get("result") != "rejected" or "/" not in value.get("diagnostic", "")
+    ]
 
 
 def run_adapter(