diff --git a/constitution.py b/constitution.py
index 7b7a61de87f7872ff9c66755200cf5103920eec6..09cee4db64af5a0677ae9baf11fd553f80db97b6 100644
--- a/constitution.py
+++ b/constitution.py
@@ -1264,7 +1264,7 @@ async def pairwise_rank(n: int, compare_fn, progress_fn=None) -> list:
     # There is exactly one logical pass; step is how far down the ranking we
     # had to scan to find the first uncovered adjacent pair (1 = top of zip).
     while True:
-        scores = rank_centrality(pairs)
+        scores = await asyncio.to_thread(rank_centrality, pairs)
         ranking = sorted(range(n), key=lambda idx: scores[idx], reverse=True)
 
         target = None
@@ -2462,7 +2462,7 @@ async def rank_commits(commits: list[dict], *, epoch: int = -1):
     if not pairs:
         commit_score_list = [Decimal("1")]
     else:
-        scores = rank_centrality(pairs)
+        scores = await asyncio.to_thread(rank_centrality, pairs)
         commit_score_list = [Decimal(str(scores[i])) for i in range(len(ordered))]
 
     commit_ranking = {
diff --git a/tests/test_pair_selection.py b/tests/test_pair_selection.py
index 8a5614da2ba6062af961f2bb942af70fd7c69813..49ddca99fdf1c5fa7a5ca2c9cca600cefbef214d 100644
--- a/tests/test_pair_selection.py
+++ b/tests/test_pair_selection.py
@@ -14,7 +14,9 @@ progress_fn(event: dict) -> None
 """
 
 import asyncio
+import time
 import pytest
+import constitution as c
 from constitution import UnionFind, pairwise_rank, rank_centrality
 
 
@@ -353,6 +355,37 @@ def test_cached_comparisons_yield_to_other_event_loop_work():
     assert run(scenario()) >= 19
 
 
+def test_rank_centrality_solve_runs_off_the_event_loop(monkeypatch):
+    original = c.rank_centrality
+
+    def slow_rank_centrality(pairs):
+        time.sleep(0.05)
+        return original(pairs)
+
+    monkeypatch.setattr(c, "rank_centrality", slow_rank_centrality)
+
+    async def scenario():
+        heartbeat_ticks = 0
+        ranking_done = False
+
+        async def cached_compare(i, j):
+            return [(min(i, j), max(i, j), 2.0, 1.0)]
+
+        async def heartbeat():
+            nonlocal heartbeat_ticks
+            while not ranking_done:
+                heartbeat_ticks += 1
+                await asyncio.sleep(0.001)
+
+        heartbeat_task = asyncio.create_task(heartbeat())
+        await c.pairwise_rank(3, cached_compare)
+        ranking_done = True
+        await heartbeat_task
+        return heartbeat_ticks
+
+    assert run(scenario()) >= 5
+
+
 # ---------------------------------------------------------------------------
 # rank_centrality accumulates (no overwrite bug)
 # ---------------------------------------------------------------------------