diff --git a/tests/test_s3_integration.py b/tests/test_s3_integration.py
index 7276101b..05185499 100644
--- a/tests/test_s3_integration.py
+++ b/tests/test_s3_integration.py
@@ -5,11 +5,13 @@
 
 from uuid import uuid4
 
+import obstore
 import pytest
 
 from haiku.rag.app import HaikuRAGApp
 from haiku.rag.client import HaikuRAG
 from haiku.rag.config.models import AppConfig, LanceDBConfig
+from haiku.rag.s3 import make_s3_store
 from haiku.rag.store.engine import Store
 from tests.services import reachable
 
@@ -43,11 +45,28 @@ def _make_config() -> AppConfig:
     )
 
 
+@pytest.fixture
+def config():
+    """A config pointing at a unique S3 prefix, cleaned up after the test.
+
+    SeaweedFS reclaims volume space lazily, so leaving each run's data behind
+    eventually fills the volume server and seals its volumes read-only, which
+    makes every subsequent write block forever.
+    """
+    config = _make_config()
+    yield config
+
+    bucket, _, prefix = config.lancedb.uri.removeprefix("s3://").partition("/")
+    store = make_s3_store(bucket, S3_STORAGE_OPTIONS)
+    paths = [obj["path"] for batch in store.list(prefix=f"{prefix}/") for obj in batch]
+    if paths:
+        obstore.delete(store, paths)
+
+
 @pytest.mark.asyncio
-async def test_store_connect_and_create(tmp_path):
+async def test_store_connect_and_create(tmp_path, config):
     from haiku.rag.store.engine import get_database_stats
 
-    config = _make_config()
     async with Store(tmp_path / "unused", config=config, create=True) as store:
         stats = await get_database_stats(store.db)
         assert stats["documents"]["exists"]
@@ -55,17 +74,15 @@ async def test_store_connect_and_create(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_store_vacuum(tmp_path):
-    config = _make_config()
+async def test_store_vacuum(tmp_path, config):
     async with Store(tmp_path / "unused", config=config, create=True) as store:
         await store.vacuum()
 
 
 @pytest.mark.asyncio
-async def test_store_add_document(tmp_path):
+async def test_store_add_document(tmp_path, config):
     from haiku.rag.store.engine import DocumentRecord, get_database_stats
 
-    config = _make_config()
     async with Store(tmp_path / "unused", config=config, create=True) as store:
         doc = DocumentRecord(content="The quick brown fox jumps over the lazy dog.")
         await store.documents_table.add([doc])
@@ -75,8 +92,7 @@ async def test_store_add_document(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_client_create_document(tmp_path):
-    config = _make_config()
+async def test_client_create_document(tmp_path, config):
     async with HaikuRAG(tmp_path / "unused", config=config, create=True) as rag:
         doc = await rag.create_document(
             "Python is a programming language.", uri="test://python"
@@ -86,8 +102,7 @@ async def test_client_create_document(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_client_list_documents(tmp_path):
-    config = _make_config()
+async def test_client_list_documents(tmp_path, config):
     async with HaikuRAG(tmp_path / "unused", config=config, create=True) as rag:
         await rag.create_document("First document.", uri="test://first")
         await rag.create_document("Second document.", uri="test://second")
@@ -97,8 +112,7 @@ async def test_client_list_documents(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_client_search(tmp_path):
-    config = _make_config()
+async def test_client_search(tmp_path, config):
     async with HaikuRAG(tmp_path / "unused", config=config, create=True) as rag:
         await rag.create_document(
             "The Eiffel Tower is located in Paris, France.", uri="test://eiffel"
@@ -109,8 +123,7 @@ async def test_client_search(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_client_delete_document(tmp_path):
-    config = _make_config()
+async def test_client_delete_document(tmp_path, config):
     async with HaikuRAG(tmp_path / "unused", config=config, create=True) as rag:
         doc = await rag.create_document("Temporary document.", uri="test://temp")
         await rag.delete_document(doc.id)
@@ -119,8 +132,7 @@ async def test_client_delete_document(tmp_path):
 
 
 @pytest.mark.asyncio
-async def test_app_info(tmp_path, capsys):
-    config = _make_config()
+async def test_app_info(tmp_path, capsys, config):
     async with HaikuRAG(tmp_path / "unused", config=config, create=True) as rag:
         await rag.create_document("Info test document.", uri="test://info")
 
@@ -134,8 +146,7 @@ async def test_app_info(tmp_path, capsys):
 
 
 @pytest.mark.asyncio
-async def test_app_info_empty_db(tmp_path, capsys):
-    config = _make_config()
+async def test_app_info_empty_db(tmp_path, capsys, config):
     app = HaikuRAGApp(db_path=tmp_path / "unused", config=config)
     await app.info()