diff --git a/bench/jit_trace.lua b/bench/jit_trace.lua
index ce852452b7ac9ba2a14a58cdaba45e65f020f10b..4fdca356af61e4ceca31423e281b234e398337bc 100644
--- a/bench/jit_trace.lua
+++ b/bench/jit_trace.lua
@@ -1,5 +1,5 @@
 #!/usr/bin/env tarantool
--- Trace-stability gate (PLAN.md M6).
+-- Trace-stability gate for protobuf encode/decode hot paths.
 --
 -- For each hot encode/decode path, run a few thousand iterations with
 -- a `trace` listener attached and assert that no trace aborts in
@@ -30,6 +30,15 @@     .. './examples/expected/?.lua;./examples/expected/?/init.lua;'
     .. package.path
 
 jit.on()
+-- macOS arm64 mcode arena hardening: the default sizemcode/maxmcode are too
+-- small for our combined hot-path codegen footprint, and the allocator
+-- intermittently fails to find an executable page within the signed-32-bit
+-- offset window. When that happens the gate reports every check as
+-- 'stops=0' with no diagnostic — indistinguishable from a real JIT
+-- topology regression. Raising the arena past our peak need eliminates
+-- the failure mode and keeps the gate's pass/fail signal load-bearing.
+jit.opt.start('sizemcode=64', 'maxmcode=4096')
+
 local vmdef = require('jit.vmdef')
 
 -- Codes from jit.vmdef.traceerr (1-indexed). We treat these as fatal —
@@ -94,6 +103,16 @@                 }
             end
         end
     end
+    -- Defensive: keep the listener out of the JIT. If the callback ever
+    -- becomes hot enough to be traced, recording the cb while recording
+    -- the function-under-test races and stop events are dropped (starts
+    -- still fire, but most traces never finish recording). The current
+    -- cb body branches enough to dodge this organically, but any future
+    -- extension (per-event timing, pc context capture, etc.) would
+    -- re-trigger it silently. Reproducible in a few lines: a fat cb
+    -- that appends event tuples to a table drops Person_encode's stop
+    -- count from ~9 to 0 on this codebase.
+    jit.off(cb)
     jit.attach(cb, 'trace')
     for _ = 1, measured_iters do fn() end
     jit.attach(cb)