diff --git a/apps/server-nestjs/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql b/apps/server-nestjs/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql
new file mode 100644
index 0000000000..013e336c08
--- /dev/null
+++ b/apps/server-nestjs/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql
@@ -0,0 +1,37 @@
+-- Tighten the 20260907170000_backfill_project_roles anti-join to the role
+-- level: the original matches on projectId only, so any project owning at
+-- least one ProjectRole row never receives its missing system roles.
+-- Mirrors generateProjectCreateInput (apps/server-nestjs/src/modules/project/project.utils.ts):
+--   Administrateur  = MANAGE                                                       = 2
+--   DevOps          = MANAGE_ENVIRONMENTS | MANAGE_REPOSITORIES | REPLAY_HOOKS
+--                     | SEE_SECRETS | LIST_ENVIRONMENTS | LIST_REPOSITORIES        = 984
+--   Développeur     = MANAGE_REPOSITORIES | LIST_ENVIRONMENTS | LIST_REPOSITORIES = 784
+--   Lecture seule   = LIST_ENVIRONMENTS | LIST_REPOSITORIES                       = 768
+-- Anti-join on projectId + name + position + oidcGroup + permissions makes
+-- the INSERT idempotent: each absent system role is inserted individually,
+-- existing rows of any kind are untouched, a retry is a no-op.
+INSERT INTO "ProjectRole" ("id", "name", "permissions", "position", "oidcGroup", "type", "projectId")
+SELECT
+  gen_random_uuid(),
+  r."name",
+  r."permissions",
+  r."position",
+  '/' || p."slug" || r."groupSuffix",
+  'system:managed',
+  p."id"
+FROM "Project" p
+CROSS JOIN (VALUES
+  ('Administrateur', 2::bigint, 0, '/console/admin'),
+  ('DevOps', 984::bigint, 1, '/console/devops'),
+  ('Développeur', 784::bigint, 2, '/console/developer'),
+  ('Lecture seule', 768::bigint, 3, '/console/readonly')
+) AS r("name", "permissions", "position", "groupSuffix")
+WHERE NOT EXISTS (
+  SELECT 1
+  FROM "ProjectRole" existing
+  WHERE existing."projectId" = p."id"
+    AND existing."name" = r."name"
+    AND existing."position" = r."position"
+    AND existing."oidcGroup" = '/' || p."slug" || r."groupSuffix"
+    AND existing."permissions" = r."permissions"
+);
diff --git a/apps/server/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql b/apps/server/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql
new file mode 100644
index 0000000000..013e336c08
--- /dev/null
+++ b/apps/server/src/prisma/migrations/20261005155118_tighten_role_backfill/migration.sql
@@ -0,0 +1,37 @@
+-- Tighten the 20260907170000_backfill_project_roles anti-join to the role
+-- level: the original matches on projectId only, so any project owning at
+-- least one ProjectRole row never receives its missing system roles.
+-- Mirrors generateProjectCreateInput (apps/server-nestjs/src/modules/project/project.utils.ts):
+--   Administrateur  = MANAGE                                                       = 2
+--   DevOps          = MANAGE_ENVIRONMENTS | MANAGE_REPOSITORIES | REPLAY_HOOKS
+--                     | SEE_SECRETS | LIST_ENVIRONMENTS | LIST_REPOSITORIES        = 984
+--   Développeur     = MANAGE_REPOSITORIES | LIST_ENVIRONMENTS | LIST_REPOSITORIES = 784
+--   Lecture seule   = LIST_ENVIRONMENTS | LIST_REPOSITORIES                       = 768
+-- Anti-join on projectId + name + position + oidcGroup + permissions makes
+-- the INSERT idempotent: each absent system role is inserted individually,
+-- existing rows of any kind are untouched, a retry is a no-op.
+INSERT INTO "ProjectRole" ("id", "name", "permissions", "position", "oidcGroup", "type", "projectId")
+SELECT
+  gen_random_uuid(),
+  r."name",
+  r."permissions",
+  r."position",
+  '/' || p."slug" || r."groupSuffix",
+  'system:managed',
+  p."id"
+FROM "Project" p
+CROSS JOIN (VALUES
+  ('Administrateur', 2::bigint, 0, '/console/admin'),
+  ('DevOps', 984::bigint, 1, '/console/devops'),
+  ('Développeur', 784::bigint, 2, '/console/developer'),
+  ('Lecture seule', 768::bigint, 3, '/console/readonly')
+) AS r("name", "permissions", "position", "groupSuffix")
+WHERE NOT EXISTS (
+  SELECT 1
+  FROM "ProjectRole" existing
+  WHERE existing."projectId" = p."id"
+    AND existing."name" = r."name"
+    AND existing."position" = r."position"
+    AND existing."oidcGroup" = '/' || p."slug" || r."groupSuffix"
+    AND existing."permissions" = r."permissions"
+);