diff --git a/.github/workflows/test-unit-proxy-mgmt-behavior.yml b/.github/workflows/test-unit-proxy-mgmt-behavior.yml
index 49ab9894190..e73997323a4 100644
--- a/.github/workflows/test-unit-proxy-mgmt-behavior.yml
+++ b/.github/workflows/test-unit-proxy-mgmt-behavior.yml
@@ -22,7 +22,12 @@ jobs:
     uses: ./.github/workflows/_test-unit-services-base.yml
     with:
       test-path: tests/proxy_behavior
-      workers: 2
+      # workers=0 (no xdist): the world seed is a single shared Postgres
+      # state — two xdist workers both call seed_world() and race on the
+      # ``behavior-pin-budget`` row, producing UniqueViolation + cascading
+      # missing-membership FK failures. The whole suite is ~7s sequentially,
+      # so the cost of disabling parallelism here is negligible.
+      workers: 0
       reruns: 0
       enable-postgres: true
       artifact-name: proxy-mgmt-behavior