diff --git a/.changeset/green-socks-occur.md b/.changeset/green-socks-occur.md
new file mode 100644
index 0000000000..4072de30bf
--- /dev/null
+++ b/.changeset/green-socks-occur.md
@@ -0,0 +1,5 @@
+---
+"@effect/platform-browser": patch
+---
+
+ensure last port in browser worker closes naturally with the outer scope
diff --git a/packages/platform-browser/src/internal/workerRunner.ts b/packages/platform-browser/src/internal/workerRunner.ts
index bc7cc1f675..fc29cb1a44 100644
--- a/packages/platform-browser/src/internal/workerRunner.ts
+++ b/packages/platform-browser/src/internal/workerRunner.ts
@@ -59,13 +59,14 @@ export const make = (self: MessagePort | Window) =>
                   FiberSet.unsafeAdd(fiberSet, fiber)
                 } else {
                   const port = ports.get(portId)
-                  if (port) {
-                    Effect.runFork(Scope.close(port[1], Exit.void))
+                  if (!port) {
+                    return
+                  } else if (ports.size === 1) {
+                    // let the last port close with the outer scope
+                    return Deferred.unsafeDone(closeLatch, Exit.void)
                   }
                   ports.delete(portId)
-                  if (ports.size === 0) {
-                    Deferred.unsafeDone(closeLatch, Exit.void)
-                  }
+                  Effect.runFork(Scope.close(port[1], Exit.void))
                 }
               }
             }