diff --git a/scripts/compute_affected_sublibraries.jl b/scripts/compute_affected_sublibraries.jl
index 7fb18dc..90a00b1 100644
--- a/scripts/compute_affected_sublibraries.jl
+++ b/scripts/compute_affected_sublibraries.jl
@@ -14,7 +14,10 @@
 #   versions = ["lts", "1", "pre"]
 #
 #   [QA]
-#   versions = ["lts", "1"]
+#   versions = ["lts", "1"]   # NOTE: ignored — QA always runs once on "1".
+#                             # Aqua/JET/ExplicitImports are version-agnostic, so
+#                             # the QA group is centrally clamped to ["1"] (see
+#                             # QA_VERSIONS); no need to trim this per repo.
 #
 #   [GPU]
 #   versions = ["1"]
@@ -39,7 +42,7 @@
 #
 # If no test/test_groups.toml exists, the default is:
 #   Core on ["lts", "1", "pre"]
-#   QA on ["lts", "1"]
+#   QA on ["1"]
 #
 # A group that needs test-only deps beyond the sublibrary's [targets].test list should
 # carry an isolated environment at test/<group>/Project.toml that runtests.jl activates
@@ -76,7 +79,7 @@ using TOML
 
 const DEFAULT_TEST_GROUPS = Dict(
     "Core" => ["lts", "1", "pre"],
-    "QA" => ["lts", "1"],
+    "QA" => ["1"],
 )
 
 function build_dependency_graph(lib_dir::String)
@@ -241,6 +244,13 @@ const EXCLUDES = Set(
 
 const DOWNSTREAM_VERSION = "1"
 
+# QA (Aqua/JET/ExplicitImports) is version-agnostic, so running it per declared
+# version just doubles the job count with no added signal — and the lts half is
+# where the <1.11 [sources]-backport QA failures bite. Central policy: the QA
+# group always runs once, on the latest stable, regardless of the per-repo
+# [QA] versions. Repos therefore needn't trim [QA] versions in test_groups.toml.
+const QA_VERSIONS = ["1"]
+
 function build_matrix(
         direct::Set{String}, transitive::Set{String}, lib_dir::String
     )
@@ -255,7 +265,8 @@ function build_matrix(
             is_downstream && config.local_only && continue
             ci_group = group_name == "Core" ? pkg : "$(pkg)_$(group_name)"
             # Downstream (transitive) deps only run on latest stable.
-            versions = is_downstream ? [DOWNSTREAM_VERSION] : config.versions
+            versions = group_name == "QA" ? QA_VERSIONS :
+                is_downstream ? [DOWNSTREAM_VERSION] : config.versions
             for ver in versions
                 (ci_group, ver) in EXCLUDES && continue
                 push!(
@@ -313,7 +324,8 @@ function build_projects_matrix(
             config = groups[group_name]
             is_downstream && config.local_only && continue
             ci_group = group_name == "Core" ? pkg : "$(pkg)_$(group_name)"
-            versions = is_downstream ? [DOWNSTREAM_VERSION] : config.versions
+            versions = group_name == "QA" ? QA_VERSIONS :
+                is_downstream ? [DOWNSTREAM_VERSION] : config.versions
             for ver in versions
                 (ci_group, ver) in EXCLUDES && continue
                 push!(
@@ -370,7 +382,8 @@ function build_root_matrix(repo_root::String)
     for group_name in sort!(collect(keys(groups)))
         config = groups[group_name]
         runners = isempty(config.os) ? Any[config.runner] : Any[o for o in config.os]
-        for ver in config.versions
+        vers = group_name == "QA" ? QA_VERSIONS : config.versions
+        for ver in vers
             for runner in runners
                 push!(
                     entries,
diff --git a/test/runtests.jl b/test/runtests.jl
index 444566f..586cfe6 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -82,10 +82,10 @@ end
     @testset "projects-matrix: default groups + downstream→v1" begin
         direct, trans = compute_affected(["lib/A/src/A.jl"], graph, rev)
         m = build_projects_matrix(direct, trans, lib)
-        # A is directly changed: default Core on lts,1,pre + QA on lts,1
+        # A is directly changed: default Core on lts,1,pre + QA on 1 (QA defaults to v1 only)
         a = filter(e -> e.project == "lib/A", m)
         @test Set((e.group, e.version) for e in a) ==
-              Set([("Core", "lts"), ("Core", "1"), ("Core", "pre"), ("QA", "lts"), ("QA", "1")])
+              Set([("Core", "lts"), ("Core", "1"), ("Core", "pre"), ("QA", "1")])
         # B and C are downstream: version "1" only
         for p in ("lib/B", "lib/C")
             ds = filter(e -> e.project == p, m)
@@ -210,7 +210,8 @@ end
     m = build_root_matrix(d)
     cells = Set((e.group, e.version) for e in m)
     @test ("AD", "1") ∉ cells && ("AD", "pre") ∉ cells && ("AD", "lts") in cells
-    @test ("QA", "pre") ∉ cells && ("QA", "lts") in cells && ("QA", "1") in cells
+    # QA is centrally clamped to v1 only, regardless of the per-group `versions`.
+    @test ("QA", "pre") ∉ cells && ("QA", "lts") ∉ cells && ("QA", "1") in cells
     # continue_on_error rides only on the Downstream group.
     @test all(e -> e.continue_on_error, filter(e -> e.group == "Downstream", m))
     @test all(e -> !e.continue_on_error, filter(e -> e.group != "Downstream", m))
@@ -252,8 +253,8 @@ end
 
 @testset "root matrix faithfully reproduces OrdinaryDiffEq's embedded matrix" begin
     # ODE's root CI.yml is 17 groups × [lts,1,pre] minus excludes (AD->lts only,
-    # QA->lts/1, ODEInterfaceRegression->lts only). Per-group `versions`
-    # expresses the same 46 cells, which is the migration this enables.
+    # ODEInterfaceRegression->lts only). QA is centrally clamped to v1 only (see
+    # QA_VERSIONS), so it intentionally diverges from ODE's old QA-on-lts/1: 45 cells.
     base = [
         "InterfaceI", "InterfaceII", "InterfaceIII", "InterfaceIV", "InterfaceV",
         "Integrators_I", "Integrators_II", "AlgConvergence_I", "AlgConvergence_II",
@@ -273,11 +274,11 @@ end
     cells = Set((e.group, e.version) for e in build_root_matrix(d))
     groups17 = vcat(base, ["AD", "QA", "ODEInterfaceRegression"])
     expected = Set((g, v) for g in groups17 for v in ["lts", "1", "pre"])
-    for ex in [("AD", "1"), ("AD", "pre"), ("QA", "pre"), ("ODEInterfaceRegression", "1"), ("ODEInterfaceRegression", "pre")]
+    for ex in [("AD", "1"), ("AD", "pre"), ("QA", "pre"), ("QA", "lts"), ("ODEInterfaceRegression", "1"), ("ODEInterfaceRegression", "pre")]
         delete!(expected, ex)
     end
     @test cells == expected
-    @test length(cells) == 46
+    @test length(cells) == 45
 end
 
 @testset "--root-matrix CLI (no lib/ required) + JSON shape" begin