diff --git a/bunfig.toml b/bunfig.toml
new file mode 100644
--- /dev/null
+++ b/bunfig.toml
@@ -0,0 +1,2 @@
+[test]
+preload = ["./test/preload.ts"]
diff --git a/test/preload.ts b/test/preload.ts
new file mode 100644
--- /dev/null
+++ b/test/preload.ts
@@ -0,0 +1,8 @@
+// Force tests onto an in-memory database BEFORE any src/ module is imported.
+//
+// This MUST run as a bunfig [test] preload. Setting the env var inside
+// test/helpers/db.ts is too late: test files statically import src/ routes
+// (which import src/db) before the helper body runs, so src/db would already
+// have opened the real data/indiko.db. A preload runs first, guaranteeing
+// src/db sees :memory: on its very first evaluation.
+process.env.DATABASE_URL = ":memory:";