Coordinator WAL stops fsyncing per commit: one durability policy = NORMAL

src/agent_comms/coordination/database.py

@@ -140,9 +140,9 @@ def configure_connection(cls, connection: sqlite3.Connection) -> None:
         connection.execute("PRAGMA foreign_keys = ON")
         # WAL is set once, on the private stage before the file is published (or by the
         # coordinator_wal carry with every owner stopped), and persists in the file header, so
-        # no opener switches the mode and fresh openers cannot race over it. A commit is one
-        # sync of the log; the rollback journal took three (journal, file, directory).
-        connection.execute("PRAGMA synchronous = FULL")
+        # no opener switches the mode and fresh openers cannot race over it. The durability of
+        # a commit is the one StoreWriter policy every WAL writer shares, not a literal here.
+        connection.execute(f"PRAGMA synchronous = {cls.synchronous}")
 
     def _prepare_private_file(self) -> None:
         self.path.parent.mkdir(parents=True, exist_ok=True)

src/agent_comms/storage/typed_table.py

@@ -3274,6 +3274,14 @@ class StoreWriter(PublishedSQLiteFile):
     CarriedFile kind or RuntimeFile, and a TypedStore inherits DurableStore or DerivedStore.
     """
 
+    # The durability every WAL writer here applies, declared once for the family. WAL keeps
+    # the database file consistent at every synchronous level, so NORMAL is correct and loses
+    # nothing an application crash could take: only an OS crash or power loss can roll a WAL
+    # back, and only to the last checkpoint. FULL fsynced the log on every commit; a message
+    # ping committed ~58 times across the coordinator stores and paid ~58 fsyncs for it. A
+    # store that must survive power loss raises its own bar (goal stores declare EXTRA).
+    synchronous: ClassVar[str] = "NORMAL"
+
     @property
     @abstractmethod
     def store(self) -> WrittenFile:
@@ -3518,9 +3526,9 @@ class RuntimeWriter(RuntimeFile, StoreWriter):
 
 
 class WalStore(SQLiteReader, StoreWriter, StoreLockFile):
-    """One WAL file owns connection setup, attachment and retirement."""
+    """One WAL file owns connection setup, attachment and retirement.
 
-    synchronous: ClassVar[str] = "FULL"
+    Its durability is StoreWriter.synchronous; a store that needs more overrides it."""
 
     def _create_file(self) -> None:
         """Create only a new inode; never close a descriptor for a live SQLite inode."""