diff --git a/psf-memo-db/acceptance/acceptance.js b/psf-memo-db/acceptance/acceptance.js
index 2d28f96..cf4b13d 100644
--- a/psf-memo-db/acceptance/acceptance.js
+++ b/psf-memo-db/acceptance/acceptance.js
@@ -33,7 +33,19 @@ function ensureAps () {
     'https://github.com/unclebob/Acceptance-Pipeline-Specification.git', apsDir])
 }
 
+// Each scenario opens an isolated LevelDB directory under tmp/acceptance.
+// Remove leftovers from earlier runs (including pre-fix runs that leaked them)
+// so the directory cannot grow without bound.
+function cleanStaleWorlds () {
+  try {
+    fs.rmSync(path.join(root, 'tmp', 'acceptance'), { recursive: true, force: true })
+  } catch (err) {
+    // ignore cleanup errors
+  }
+}
+
 function main () {
+  cleanStaleWorlds()
   ensureAps()
 
   const features = fs
diff --git a/psf-memo-db/acceptance/lib/handlers.js b/psf-memo-db/acceptance/lib/handlers.js
index 5fcb71c..0030719 100644
--- a/psf-memo-db/acceptance/lib/handlers.js
+++ b/psf-memo-db/acceptance/lib/handlers.js
@@ -152,6 +152,13 @@ async function createWorld () {
       } catch (err) {
         // ignore close errors
       }
+      // Each scenario opens an isolated LevelDB directory. Remove it here so
+      // tmp/acceptance cannot grow without bound across runs.
+      try {
+        fs.rmSync(levelDir, { recursive: true, force: true })
+      } catch (err) {
+        // ignore cleanup errors
+      }
     }
   }
 }