diff --git a/haiku_rag_slim/haiku/rag/client/__init__.py b/haiku_rag_slim/haiku/rag/client/__init__.py
index 70a7ad21..c69240c7 100644
--- a/haiku_rag_slim/haiku/rag/client/__init__.py
+++ b/haiku_rag_slim/haiku/rag/client/__init__.py
@@ -127,8 +127,12 @@ class HaikuRAG:
 
     @property
     def is_read_only(self) -> bool:
-        """Whether the client is in read-only mode."""
-        return self.store.is_read_only
+        """Whether the client is in read-only mode.
+
+        The mode the client was opened with, which is the mode every database it
+        covers is opened with. A client covering a set has no store to ask.
+        """
+        return self._read_only
 
     @property
     def embedder(self) -> "EmbedderWrapper":
diff --git a/haiku_rag_slim/haiku/rag/config/models.py b/haiku_rag_slim/haiku/rag/config/models.py
index 06074531..83e05eee 100644
--- a/haiku_rag_slim/haiku/rag/config/models.py
+++ b/haiku_rag_slim/haiku/rag/config/models.py
@@ -123,6 +123,13 @@ class LanceDBConfig(ConfigModel):
                 "lancedb.uri and lancedb.databases are mutually exclusive: "
                 "use uri for one database, databases for several"
             )
+        for name, location in self.databases.items():
+            # A blank name is falsy, so source routing reads it as absent; a
+            # blank location resolves to the working directory.
+            if not name.strip():
+                raise ValueError("lancedb.databases has an entry with no name")
+            if not location.strip():
+                raise ValueError(f"lancedb.databases[{name}] has no location")
         return self
 
 
diff --git a/tests/test_multi_db.py b/tests/test_multi_db.py
index b0a7d135..86b5dda9 100644
--- a/tests/test_multi_db.py
+++ b/tests/test_multi_db.py
@@ -28,6 +28,23 @@ class TestConfig:
         assert LanceDBConfig(uri="s3://b/one.lancedb").databases == {}
 
 
+class TestNamingIsRequired:
+    def test_a_blank_name_is_rejected(self):
+        """An unnamed database is unreachable: every source check reads the
+        empty name as no name at all."""
+        with pytest.raises(ValidationError, match="entry with no name"):
+            LanceDBConfig(databases={"": "/tmp/a.lancedb"})
+        with pytest.raises(ValidationError, match="entry with no name"):
+            LanceDBConfig(databases={"   ": "/tmp/a.lancedb"})
+
+    def test_a_blank_location_is_rejected(self):
+        """A blank location resolves to the working directory."""
+        with pytest.raises(
+            ValidationError, match=r"databases\[alpha\] has no location"
+        ):
+            LanceDBConfig(databases={"alpha": ""})
+
+
 def _config(tmp_path, names) -> AppConfig:
     return AppConfig(
         lancedb=LanceDBConfig(
@@ -279,6 +296,20 @@ class TestLookupByIdentifier:
             assert await rag.get_document_by_uri("test://nowhere") is None
 
 
+class TestReadOnlyMode:
+    @pytest.mark.asyncio
+    async def test_a_client_covering_a_set_reports_its_mode(self, tmp_path):
+        """A client covering a set has no store of its own to ask."""
+        config = _config(tmp_path, ["alpha", "beta"])
+        await _seed(config, "alpha", ["alpha one"])
+        await _seed(config, "beta", ["beta one"])
+
+        async with HaikuRAG(config=config, read_only=True) as rag:
+            assert rag.is_read_only is True
+        async with HaikuRAG(config=config) as rag:
+            assert rag.is_read_only is False
+
+
 class TestDocumentsNameTheirDatabase:
     """A listing that spans databases is unreadable when the documents do not
     say which one they came from, the same reason a search result carries one."""