diff --git a/common_libs/gun_harness/selector.nim b/common_libs/gun_harness/selector.nim
index c784948..a9dd2b3 100644
--- a/common_libs/gun_harness/selector.nim
+++ b/common_libs/gun_harness/selector.nim
@@ -44,10 +44,10 @@ import virtual_bullets
 # transition the radar uses.
 
 const
-  RackGunNames*: array[15, string] = [
+  RackGunNames*: array[16, string] = [
     "HEADON", "LINEAR", "TSETLIN", "CIRCULAR", "GUESSFACTOR", "PATTERN",
     "WALLBOUNCE", "ACCEL", "STOPSHOT", "DISPLACE", "AVGLEAD", "DECAYGF",
-    "KNN", "TMSELECT", "TMPATTERN"]
+    "KNN", "TMSELECT", "TMPATTERN", "TMHORIZON"]
   RackEnvPrefix* = "TR_RACK_"
   ## SHIPPED DEFAULT: `onlyPattern`. Pattern (id 5) is admitted in both racks;
   ## every other gun is `off`. The selection mechanism is untouched and remains
@@ -57,7 +57,7 @@ const
   ## it never spawns a virtual bullet unless explicitly enabled, so the shared
   ## VirtualTracker ring head — and every other gun's learning order — is
   ## unchanged.
-  DefaultRackMembership*: array[15, RackMembership] = [
+  DefaultRackMembership*: array[16, RackMembership] = [
     rmOff,  # 0  HEADON      — off (measured: worst over-selected gun)
     rmOff,  # 1  LINEAR      — off
     rmOff,  # 2  TSETLIN     — off
@@ -72,7 +72,8 @@ const
     rmOff,  # 11 DECAYGF     — off
     rmOff,  # 12 KNN         — off
     rmOff,  # 13 TMSELECT    — off
-    rmOff]  # 14 TMPATTERN   — off (already shipped off; TM pattern gun)
+    rmOff,  # 14 TMPATTERN   — off (already shipped off; TM pattern gun)
+    rmOff]  # 15 TMHORIZON   — off (horizon-based TM corrector; expected to lose)
 
 proc parseRackMembership*(value: string): RackMembership =
   ## Parse a `TR_RACK_<GUN>` value. Empty / unknown values fall back to the
diff --git a/common_libs/tests/test_rack_membership.nim b/common_libs/tests/test_rack_membership.nim
index 95ea0de..38a1369 100644
--- a/common_libs/tests/test_rack_membership.nim
+++ b/common_libs/tests/test_rack_membership.nim
@@ -164,8 +164,8 @@ proc testDefaultsOnlyPattern() =
   let loaded = loadRackMembership()
   check "defaults: with a clean environment loadRackMembership() == shipped table",
         loaded == DefaultRackMembership
-  check "defaults: RackGunNames covers the shipped 15-gun rack",
-        RackGunNames.len == 15 and DefaultRackMembership.len == 15
+  check "defaults: RackGunNames covers the shipped 16-gun rack",
+        RackGunNames.len == 16 and DefaultRackMembership.len == 16
 
 proc testFloorRespectsAdmission() =
   ## The FLOOR path (`bestRate <= 0` or below the floor rate) historically fell
diff --git a/common_libs/tests/test_tm_pattern_registration.nim b/common_libs/tests/test_tm_pattern_registration.nim
index 692e9d8..f447059 100644
--- a/common_libs/tests/test_tm_pattern_registration.nim
+++ b/common_libs/tests/test_tm_pattern_registration.nim
@@ -62,7 +62,7 @@ proc seedOldRack(t: var VirtualTracker, targetId: int) =
 # ── registration table ────────────────────────────────────────────────────────
 
 proc testTable() =
-  check "rack: RackGunNames has 15 entries", RackGunNames.len == 15
+  check "rack: RackGunNames has 16 entries", RackGunNames.len == 16
   check "rack: the new gun is named TMPATTERN at id 14",
         RackGunNames[TmPatternId] == "TMPATTERN"
   check "rack: the new gun defaults to `off`",