diff --git a/MobileGL/MG_IntegrationTest/CMakeLists.txt b/MobileGL/MG_IntegrationTest/CMakeLists.txt
index 859a10e2..54c37301 100644
--- a/MobileGL/MG_IntegrationTest/CMakeLists.txt
+++ b/MobileGL/MG_IntegrationTest/CMakeLists.txt
@@ -3125,13 +3125,23 @@ if (MOBILEGL_BUILD_DISAGGREGATED)
             PROPERTIES LABELS "${mglItestMagmaLabels}" TIMEOUT ${MGL_ITEST_TIMEOUT}
                 ${mglItestArmProperties}
                 ENVIRONMENT "${mglItestMagmaWireEnvironment}\;MOBILEGL_LOG_FILE_PATH=${CMAKE_CURRENT_BINARY_DIR}/p7-streamedsubdata${mglItestArmLogTag}.log")
-        gtest_discover_tests(MobileGLIntegrationTest
-            TEST_PREFIX "DirectVulkan.${mglItestArm}.StaleSerial."
-            TEST_FILTER "F1WireScenario.StreamedBufferSubDataBeforeEachDrawIsOrdered"
-            DISCOVERY_TIMEOUT 30
-            PROPERTIES LABELS "${mglItestMagmaLabels}" TIMEOUT ${MGL_ITEST_TIMEOUT}
-                ${mglItestArmProperties}
-                ENVIRONMENT "${mglItestMagmaWireEnvironment}\;MGITEST_MAGMA_FORCE_STALE_BUFFER_SERIAL=1\;MOBILEGL_LOG_FILE_PATH=${CMAKE_CURRENT_BINARY_DIR}/p7-streamedsubdata-stale${mglItestArmLogTag}.log")
+        # SPLIT AND SPAWN ONLY - a parity exception, named in scripts/ci/spawn_lane_parity.py
+        # (MAGMA_SERVER_ENV_KNOB_NO_TCP, the same list as the B2 knobs above), not an omission.
+        # The knob is read by the SERVER, and the tcp arm's server is the lane fixture
+        # (scripts/ci/tcp_server_fixture.py) started once from its own environment: an
+        # entry-level ENVIRONMENT never reaches it, so a Tcp.StaleSerial. entry would run the
+        # plain Fm case under a name that claims the knob, and could never red. The inproc arm
+        # hosts the server in the test process and the spawn arm's server inherits the client's
+        # environment, so on those two the knob is real.
+        if(mglItestServerEnvKnobArm)
+            gtest_discover_tests(MobileGLIntegrationTest
+                TEST_PREFIX "DirectVulkan.${mglItestArm}.StaleSerial."
+                TEST_FILTER "F1WireScenario.StreamedBufferSubDataBeforeEachDrawIsOrdered"
+                DISCOVERY_TIMEOUT 30
+                PROPERTIES LABELS "${mglItestMagmaLabels}" TIMEOUT ${MGL_ITEST_TIMEOUT}
+                    ${mglItestArmProperties}
+                    ENVIRONMENT "${mglItestMagmaWireEnvironment}\;MGITEST_MAGMA_FORCE_STALE_BUFFER_SERIAL=1\;MOBILEGL_LOG_FILE_PATH=${CMAKE_CURRENT_BINARY_DIR}/p7-streamedsubdata-stale${mglItestArmLogTag}.log")
+        endif()
         # `default-color-blit-shape@P7`'s retirement. TWO ENTRIES OVER ONE CASE, and the second
         # is the only way its arm is reachable here: every surface this lane creates reports
         # VK_SURFACE_TRANSFORM_IDENTITY, so the scratch path that exists FOR rotation would
diff --git a/scripts/ci/spawn_lane_parity.py b/scripts/ci/spawn_lane_parity.py
index 2e48d630..a6243c8e 100644
--- a/scripts/ci/spawn_lane_parity.py
+++ b/scripts/ci/spawn_lane_parity.py
@@ -72,8 +72,12 @@ MAGMA_INPROC_ONLY = ("MagmaRunAheadScenario.", "MagmaWireCacheScenario.")
 # These are TAILS, not scenarios - the normaliser above keeps the sub-lane tail for the Magma
 # tier on purpose, so `.MsResolve1.` names the knob entry and `.MsResolve0.` (the default, which
 # does keep its tcp entry) is untouched.
+#
+# P7 wave 2-B3 (ID-P7-34) adds `.StaleSerial.`: MGITEST_MAGMA_FORCE_STALE_BUFFER_SERIAL is read by
+# the server too (VkBufferManager.cpp), so the streamed subdata-then-draw red-once has the same
+# two arms and the same tcp absence. One list, one mechanism, for every server-side knob.
 MAGMA_SERVER_ENV_KNOB_NO_TCP = (".ShaderMip1.", ".ShaderMip2.", ".DepthMip.",
-                                ".DefaultBlitShape1.", ".MsResolve1.")
+                                ".DefaultBlitShape1.", ".MsResolve1.", ".StaleSerial.")
 
 
 def lane_names(build_dir, label):
@@ -103,6 +107,7 @@ def compare_arms(build_dir, tier, labels, inproc_only=(), no_tcp=()):
     it on spawn, which is where it does most of its work.
 
     Returns True on failure, the way main() below counts them."""
+    not_on_arm = not_on_arm or {}
     sets = {}
     for arm, label in labels.items():
         names = lane_names(build_dir, label) - FIXTURE_ENTRIES