row 269 (264b, #1774): the M6 halt test halts after mayLaunch answers

A halt inside the op reaches the bus's own fence first (runtime.mjs:564-566,
processingWork at :352-356), so the launcher refused limit-check-failed
(launcher.mjs:389-391) before its recheck admission() at :397. First-run red of
a new test on 6d9ab3503 early signal, placed under mos-1272.

packages/cli/tests/session-launch.test.mjs

@@ -372,8 +372,8 @@ test("REQ-THREAD-2 REQ-LAUNCH-1 a symlinked session store refuses thread-store-r
 // T2, M6 and the halt fence (C2). The credentialStatus op runs in start() after check() returned.
 // Its first call halts and resumes, a new generation with no halt, so only start()'s own
 // admission(admissionGeneration) refuses, before the session workspace is made. On the retry,
-// the recheck's mayLaunch op (inside check(), after the lock is taken) halts, and the recheck
-// refuses processing-halted. Neither attempt spawns, and the second releases its lock.
+// the recheck's mayLaunch op (inside check(), after the lock is taken) halts once it has answered,
+// and the recheck's admission() refuses processing-halted. Neither attempt spawns, and the second releases its lock.
 test("REQ-THREAD-2 REQ-LAUNCH-1 a named session's start refuses processing-generation-changed, then processing-halted, after check() and before any spawn", { skip, timeout: 60000 }, async (t) => {
   const prepared = prepare(t);
   const { f } = prepared;
@@ -389,12 +389,15 @@ test("REQ-THREAD-2 REQ-LAUNCH-1 a named session's start refuses processing-gener
         }
         return runtime.credentialStatus(m.business, m.role);
       },
-      mayLaunch: (m) => {
+      // The halt lands after the op answers: halted inside it, the bus's own fence
+      // (runtime.mjs processingWork) throws and the launcher refuses limit-check-failed.
+      mayLaunch: async (m) => {
+        const may = await runtime.mayLaunch(m);
         if (m.instance === "assistant" && credentials === 2 && halts === 1) {
           halt();
           halts++;
         }
-        return runtime.mayLaunch(m);
+        return may;
       },
     }),
   });