diff --git a/picopt/config/__init__.py b/picopt/config/__init__.py
index d3d3cde..ac16fca 100644
--- a/picopt/config/__init__.py
+++ b/picopt/config/__init__.py
@@ -16,7 +16,6 @@
 
 from confuse import Configuration, MappingTemplate
 from confuse.templates import (
-    AttrDict,
     Choice,
     Integer,
     Optional,
@@ -214,9 +213,6 @@ def get_config(
         self._set_timestamps(config_program)
         self.set_format_handler_map(config_program)
         ad = config.get(_build_template())
-        if not isinstance(ad, AttrDict):
-            msg = f"Expected AttrDict from confuse, got {type(ad).__name__}"
-            raise TypeError(msg)
         return _settings_from_attrdict(ad.picopt)
 
 
diff --git a/picopt/walk/scheduler.py b/picopt/walk/scheduler.py
index f2a8bed..eb8a31b 100644
--- a/picopt/walk/scheduler.py
+++ b/picopt/walk/scheduler.py
@@ -339,20 +339,25 @@ def _inflight_count(self) -> int:
             + len(self._inflight_repack)
         )
 
-    def _submit_ready_job(self) -> None:
-        """Pop and submit one job from the ready dequeue."""
-        job, node = self._ready.popleft()
-        # Skip jobs whose owning node got cancelled while they were queued.
-        if node is not None and node.state is NodeState.CANCELLED:
-            match job:
-                case UnpackJob() | RepackJob():
-                    # node's own job — the cancel walk already decremented
-                    # the parent counter, nothing to do.
-                    pass
-                case _:
-                    node.pending = max(0, node.pending - 1)
-            return
-        fut = self._executor.submit(job.run)
+    @staticmethod
+    def _drop_cancelled_ready_job(job: Job, node: ContainerNode) -> None:
+        """
+        Decrement parent pending counter for a leaf of a cancelled subtree.
+
+        UnpackJob/RepackJob jobs belong to ``node`` itself; the cancel walk
+        already decremented the parent's pending counter for them, so they
+        need no further bookkeeping.
+        """
+        match job:
+            case UnpackJob() | RepackJob():
+                pass
+            case _:
+                node.pending = max(0, node.pending - 1)
+
+    def _track_submitted_job(
+        self, fut: Future, job: Job, node: ContainerNode | None
+    ) -> None:
+        """Record an in-flight future under the right map and update state."""
         match job:
             case UnpackJob():
                 assert node is not None
@@ -367,6 +372,16 @@ def _submit_ready_job(self) -> None:
                 node.state = NodeState.REPACKING
                 self._inflight_repack[fut] = node
 
+    def _submit_ready_job(self) -> None:
+        """Pop and submit one job from the ready dequeue."""
+        job, node = self._ready.popleft()
+        # Skip jobs whose owning node got cancelled while they were queued.
+        if node is not None and node.state is NodeState.CANCELLED:
+            self._drop_cancelled_ready_job(job, node)
+            return
+        fut = self._executor.submit(job.run)
+        self._track_submitted_job(fut, job, node)
+
     def _submit_ready(self) -> None:
         """Submit ready jobs up to the backpressure cap."""
         cap = 2 * self._max_workers