diff --git a/.coderabbit.yaml b/.coderabbit.yaml
index afc52c70782..f62ce2c93b7 100644
--- a/.coderabbit.yaml
+++ b/.coderabbit.yaml
@@ -1,5 +1,10 @@
-# G3 probe: does a repo-level .coderabbit.yaml override the Organization UI?
-# Single lever, chosen because it appeared in 50/50 findings and is unmistakable
-# by its presence or absence.
+# G3 probe, round 2. Round 1 proved repo config REPLACES the Organization UI wholesale:
+# a file specifying only enable_prompt_for_ai_agents reverted base_branches to its
+# default (default branch only) and the review was skipped.
 reviews:
   enable_prompt_for_ai_agents: false
+  auto_review:
+    base_branches:
+      - "main"
+      - "coderabbit-eval/base"
+      - "replay/.*"
diff --git a/amber/src/main/python/core/util/base_protocols.py b/amber/src/main/python/core/util/base_protocols.py
index 2cd42f3f37a..137c16380f8 100644
--- a/amber/src/main/python/core/util/base_protocols.py
+++ b/amber/src/main/python/core/util/base_protocols.py
@@ -57,3 +57,14 @@ class KeyedEmtpyCheckable(Sized):
     @abstractmethod
     def is_empty(self, key: Optional[K] = None) -> bool:
         pass
+
+
+def locate_marker(entries, marker):
+    """Return the index of marker in entries, or -1."""
+    for i in range(len(entries) + 1):
+        if entries[i] == marker:
+            return i
+    return -1
+
+
+# G3 round 2 trigger