diff --git a/role_session_router.py b/role_session_router.py
index b9a0406..23eb945 100644
--- a/role_session_router.py
+++ b/role_session_router.py
@@ -5,12 +5,14 @@ returns a route result before any downstream mutation tools run.
 """
 
 from __future__ import annotations
+import os
 
 ROUTE_ALLOWED = "allowed_current_session"
 ROUTE_WRONG_ROLE = "wrong_role_stop"
 ROUTE_TO_AUTHOR = "route_to_author_session"
 ROUTE_TO_REVIEWER = "route_to_reviewer_session"
 ROUTE_AMBIGUOUS = "ambiguous_task_stop"
+ROUTE_INFRA_STOP = "infra_stop"
 
 REVIEWER_TASKS = frozenset({
     "review_pr",
@@ -93,6 +95,23 @@ def route_task_session(
         _record_route(result)
         return result
 
+    if required_role == "reviewer" and check_mid_merge():
+        result = {
+            "task_type": task_type,
+            "required_role": required_role,
+            "active_role": active_role_kind,
+            "active_profile": active_profile,
+            "route_result": ROUTE_INFRA_STOP,
+            "downstream_allowed": False,
+            "reasons": [
+                "infra_stop: Unresolved merge conflict or mid-merge state detected in MCP runtime source.",
+                "Please resolve all conflicts manually, finish/abort the merge, restart the MCP server, and retry."
+            ],
+            "message": "infra_stop: Unresolved merge conflict or mid-merge state detected in MCP runtime source.",
+        }
+        _record_route(result)
+        return result
+
     if allowed_in_current_session:
         result = {
             "task_type": task_type,
@@ -192,4 +211,37 @@ def check_author_mutation_after_reviewer_stop(mutation_task: str) -> tuple[bool,
             "task and relaunches an author MCP session.",
             f"Attempted fallback mutation: {mutation_task}",
         ]
-    return True, []
\ No newline at end of file
+    return True, []
+
+
+def check_mid_merge() -> bool:
+    """Return True if the repository is mid-merge, mid-rebase, or has conflict markers."""
+    project_root = os.path.dirname(os.path.abspath(__file__))
+    git_dir = os.path.join(project_root, ".git")
+    if os.path.exists(git_dir):
+        if (os.path.exists(os.path.join(git_dir, "MERGE_HEAD"))
+                or os.path.exists(os.path.join(git_dir, "rebase-merge"))
+                or os.path.exists(os.path.join(git_dir, "rebase-apply"))):
+            return True
+
+    # Scan python files for conflict markers
+    conflict_patterns = [
+        b"<" * 7 + b" ",
+        b"=" * 7 + b"\n",
+        b"=" * 7 + b"\r\n",
+        b">" * 7 + b" "
+    ]
+    for root, dirs, files in os.walk(project_root):
+        if any(p in root for p in ("venv", ".git", ".pytest_cache", "branches")):
+            continue
+        for file in files:
+            if file.endswith(".py"):
+                file_path = os.path.join(root, file)
+                try:
+                    with open(file_path, "rb") as f:
+                        content = f.read()
+                        if any(pattern in content for pattern in conflict_patterns):
+                            return True
+                except Exception:
+                    pass
+    return False
\ No newline at end of file