diff --git a/fifa17-recon/tools/test_capability_negotiation.py b/fifa17-recon/tools/test_capability_negotiation.py
index f4ad645..1c6c6f2 100755
--- a/fifa17-recon/tools/test_capability_negotiation.py
+++ b/fifa17-recon/tools/test_capability_negotiation.py
@@ -28,6 +28,7 @@ Matrix (docs/plans/FIFA17_PATCHED_CLIENT_CAPABILITY.md):
   O session cleanup / TTL expiry                 -> capability gone, sentinel
   P duplicate registration for a session         -> idempotent; no post-freeze change
   Q register-before-login (pending consumed)     -> clean
+  R topology freeze immutable per SID            -> no flip either way; new SID fresh
 
 Standalone unit test in the project style: `python3 test_capability_negotiation.py`.
 """
@@ -266,10 +267,33 @@ def main():
             assert mode_of("sidQ") == CLEAN
             print("Q register-before-login pending consumed -> clean: OK")
 
+            # ---- R. topology freeze immutable per SID; new SID decides fresh ----
+            # F3 invariant: once a SID's store topology is decided it NEVER flips,
+            # in either direction, and a different SID may decide differently.
+            reset_state(); set_zero_packs()
+            IP = "10.0.2.8"
+            # frozen Sentinel never becomes Clean, even if a capability appears later
+            auth("sidR_s", IP)
+            assert SENTINEL_ID in store("sidR_s", IP)            # freeze Sentinel
+            register(IP, 1)
+            us._FIFA17_SESSIONS["sidR_s"]["resolver"] = 1        # force-present capability
+            assert SENTINEL_ID in store("sidR_s", IP)            # STILL Sentinel
+            assert mode_of("sidR_s") == SENT
+            # frozen Clean never becomes Sentinel, even if the capability is wiped
+            auth("sidR_c", IP); register(IP, 1)
+            assert SENTINEL_ID not in store("sidR_c", IP)        # freeze Clean
+            us._FIFA17_SESSIONS["sidR_c"]["resolver"] = None     # capability vanishes
+            assert SENTINEL_ID not in store("sidR_c", IP)        # STILL Clean
+            assert mode_of("sidR_c") == CLEAN
+            # a fresh SID (same IP) decides independently
+            auth("sidR_new", IP)
+            assert SENTINEL_ID in store("sidR_new", IP)
+            print("R topology freeze immutable per SID; new SID fresh: OK")
+
         finally:
             us.visible_unopened_packs = _orig_visible
 
-    print("capability negotiation matrix A-Q: OK")
+    print("capability negotiation matrix A-R: OK")
     return 0