P264: rebind checked bus copies without a cold rebuild

src/agent_comms/checkpoint_seals.py

@@ -10,7 +10,7 @@
 from .declared_family import DeclaredFamily
 from .errors import CheckpointNeedsRepairError, RelationViolationError
 from .field_codec import Id128Text, Sha256Text
-from .private_path import FileRevision
+from .private_path import FileIdentity, FileRevision
 
 if TYPE_CHECKING:
     import os
@@ -66,7 +66,14 @@ def recover(
         path: Path,
         saved: PrefixWitness,
         info: os.stat_result,
-    ) -> PrefixWitness | None: ...
+    ) -> PrefixWitness:
+        return saved.index_tail(bus, marker, db, path, info)
+
+    @abstractmethod
+    def recovery_end(self, info: os.stat_result) -> int: ...
+
+    @abstractmethod
+    def chunk_complete(self, offset: int, size: int, rows: int) -> bool: ...
 
     def check_final(self, saved: PrefixWitness, db_path: Path) -> None:
         raise RelationViolationError("Private bus checkpoint index seal changed or is pending.")
@@ -100,8 +107,24 @@ def recover(
         path: Path,
         saved: PrefixWitness,
         info: os.stat_result,
-    ) -> None:
-        self.check_final(saved, path)
+    ) -> PrefixWitness:
+        if saved.revision.identity != FileIdentity.from_stat(info):
+            self.require_rebuilt(saved, saved)
+            copied = FileRevision.from_stat(path.stat())
+            if (copied.size, copied.mtime_ns) != (self.db_revision.size, self.db_revision.mtime_ns):
+                raise RelationViolationError("Private bus copied index content revision changed.")
+            saved = saved.rebind_source(bus, marker, db, info)
+        else:
+            self.check_final(saved, path)
+        if saved.revision == FileRevision.from_stat(info):
+            return saved
+        return super().recover(bus, marker, db, path, saved, info)
+
+    def recovery_end(self, info: os.stat_result) -> int:
+        return info.st_size
+
+    def chunk_complete(self, offset: int, size: int, rows: int) -> bool:
+        return size >= 16 * 1024 * 1024 or rows >= 10_000
 
     def require_rebuilt(self, saved: PrefixWitness, rebuilt: PrefixWitness) -> None:
         if self.witness != saved.seal():
@@ -129,15 +152,18 @@ def recover(
         saved: PrefixWitness,
         info: os.stat_result,
     ) -> PrefixWitness:
-        from .private_bus_checkpoint import _rebuild_checkpoint_unlocked
-
-        if (
-            saved.seal() not in (self.prior, self.expected)
-            or self.expected.revision != FileRevision.from_stat(info)
-            or self.prior.root_id != marker.root_id
-        ):
+        if (saved.seal() not in (self.prior, self.expected)
+                or not self.expected.revision.holds_cut(
+                    FileRevision.from_stat(info), self.expected.revision.size)
+                or self.prior.root_id != marker.root_id):
             raise RelationViolationError("Private bus checkpoint pending intent is inconsistent.")
-        return _rebuild_checkpoint_unlocked(bus, marker, db, path, info, self)
+        return super().recover(bus, marker, db, path, saved, info)
+
+    def recovery_end(self, info: os.stat_result) -> int:
+        return self.expected.revision.size
+
+    def chunk_complete(self, offset: int, size: int, rows: int) -> bool:
+        return offset == self.expected.revision.size
 
     def require_rebuilt(self, saved: PrefixWitness, rebuilt: PrefixWitness) -> None:
         if (