feat: add session titles and migration

tests/unit/test_sqlite_store.py

@@ -1,3 +1,4 @@
+import sqlite3
 import tempfile
 import unittest
 from pathlib import Path
@@ -21,6 +22,8 @@ class SQLiteSessionStoreTests(unittest.TestCase):
         self.assertEqual(loaded.id, created.id)
         self.assertEqual(loaded.provider, "ollama")
         self.assertEqual(loaded.model, "test-model")
+        self.assertEqual(loaded.title, "Neue Sitzung")
+        self.assertEqual(loaded.last_provider, "ollama")
         self.assertEqual(self.store.list_sessions()[0].id, created.id)
 
     def test_messages_keep_exchange_order(self) -> None:
@@ -53,6 +56,69 @@ class SQLiteSessionStoreTests(unittest.TestCase):
         self.assertEqual(self.store.get_messages(session.id), [])
         self.assertEqual(self.store.get_session(session.id).message_count, 0)
 
+    def test_first_exchange_sets_title_and_last_provider_atomically(self) -> None:
+        session = self.store.create_session("hybrid", "auto")
+
+        self.store.append_exchange(
+            session.id,
+            "Frage",
+            "Antwort",
+            title_if_first="Kurzer Titel",
+            last_provider="gemini",
+        )
+        self.store.append_exchange(
+            session.id,
+            "Noch eine Frage",
+            "Noch eine Antwort",
+            title_if_first="Darf Titel nicht ersetzen",
+            last_provider="ollama",
+        )
+
+        loaded = self.store.get_session(session.id)
+        self.assertEqual(loaded.title, "Kurzer Titel")
+        self.assertEqual(loaded.last_provider, "ollama")
+
+    def test_old_database_is_migrated_idempotently_without_data_loss(self) -> None:
+        database = Path(self.temporary_directory.name) / "legacy.sqlite3"
+        with sqlite3.connect(database) as connection:
+            connection.executescript(
+                """
+                CREATE TABLE sessions (
+                    id TEXT PRIMARY KEY,
+                    created_at TEXT NOT NULL,
+                    updated_at TEXT NOT NULL,
+                    provider TEXT NOT NULL,
+                    model TEXT NOT NULL
+                );
+                CREATE TABLE messages (
+                    id INTEGER PRIMARY KEY AUTOINCREMENT,
+                    session_id TEXT NOT NULL,
+                    position INTEGER NOT NULL,
+                    role TEXT NOT NULL,
+                    content TEXT NOT NULL,
+                    created_at TEXT NOT NULL,
+                    UNIQUE (session_id, position)
+                );
+                INSERT INTO sessions VALUES
+                    ('legacy', '2026-01-01', '2026-01-02', 'ollama', 'old-model');
+                INSERT INTO messages
+                    (session_id, position, role, content, created_at)
+                VALUES ('legacy', 0, 'user', 'Alte Nachricht', '2026-01-02');
+                """
+            )
+        connection.close()
+
+        migrated = SQLiteSessionStore(database)
+        migrated_again = SQLiteSessionStore(database)
+
+        session = migrated_again.get_session("legacy")
+        self.assertEqual(session.title, "Neue Sitzung")
+        self.assertEqual(session.last_provider, "ollama")
+        self.assertEqual(
+            [message.content for message in migrated.get_messages("legacy")],
+            ["Alte Nachricht"],
+        )
+
 
 if __name__ == "__main__":
     unittest.main()