diff --git a/docs/sbl-bringup.md b/docs/sbl-bringup.md
index ea1627d..8c2b819 100644
--- a/docs/sbl-bringup.md
+++ b/docs/sbl-bringup.md
@@ -91,3 +91,15 @@
 - b23: 2M инстр. без падений (sp здоров), sbl_main идёт дальше
   (`0x80164C4`-subtree → прыжок в OCIMEM-нули `0x222F84` — фронт PBL-данных).
   QEMU-паритет: R15=0x223000, sp=0x85FFF00, lr=0x80164CB — там же.
+
+## b24: world-switch stub, clock S11 (2026-09-12)
+- Диспетчер (`0x80164C4`-subtree) зовёт ARM jump-table `0x8007158`
+  (`ldr pc`), та — в OCIMEM-трамплин world-switch `0x221EF8`
+  (ARM: save regs, `cps MON`, `mrc`, `ldr sp/pc` из PBL-таблиц
+  `[0x221F6C]=0x223620`/`[0x221F70]=0x223930` → вызов TZ; TZ не загружен).
+  Вход получается в Thumb → b24-стаб (4B `movs r0,#0; bx lr`):
+  возврат 0 в диспетчер (TZ deferred). Перезаписывает голову ARM'а
+  (восстановимо из ELF).
+- Дальше: clock-fn `0x800E960` (udiv-подсчёты) с голым выходом
+  `pop{r4,pc}` (без push, tail-chain через NOP-идиому) → S11 (b24):
+  вход → `bx lr` (lr = брошенный-но-валидный `0x80076CD`).
diff --git a/qemu/saimaa.c b/qemu/saimaa.c
index 4d62a50..0585bcf 100644
--- a/qemu/saimaa.c
+++ b/qemu/saimaa.c
@@ -698,6 +698,13 @@ static void saimaa_machine_init(MachineState *machine)
                 uint32_t v = 0x08006B8D;
                 cpu_physical_memory_write(0x080528D0, &v, 4);
             }
+            /* PBL world-switch Thumb-stub (b24, 4B @0x00221EF8):
+             * movs r0,#0; bx lr (return 0 to dispatcher, TZ deferred).
+             * Overwrites ARM trampoline head (recoverable from ELF). */
+            {
+                uint32_t v = 0x47702000;
+                cpu_physical_memory_write(0x00221EF8, &v, 4);
+            }
             {
                 uint32_t fill = 0x08006B8D;
                 uint32_t a;
diff --git a/tools/sbl_patch.py b/tools/sbl_patch.py
index b8663f5..6cd5a5e 100644
--- a/tools/sbl_patch.py
+++ b/tools/sbl_patch.py
@@ -874,6 +874,87 @@ def main():
 
     save(d, 'img0_b23.elf')
 
+    # b24 = b23 + S11 (clock-fn naked-exit fix):
+    # 0x800E988 pop{r4,pc} has no matching push (naked tail-chain worker:
+    # bl 0x8006684-idiom tail-jumps to the clock fn, abandoning lr).
+    # Each dispatcher pass eats 0x8+ ([sp] -> wild 0x902FC506).
+    # S11 turns the exit into bx lr (lr = abandoned-but-valid resumption
+    # 0x80076CD/0x80076D3 in the caller). 2B patch, like S8.
+    d = bytearray(base)
+
+    for va, (a, b) in BLX2BL.items():
+
+        set4(d, va, b)
+
+    for va, exp, new in [
+
+        (0x802F664, 'e4f77efc', 'c046c046'),
+
+        (0x802F672, 'e6f7bbfa', 'c046c046'),
+
+        (0x802F678, 'e9f7fef9', 'c046c046'),
+
+        (0x801B71E, '9847fee7', 'c046c046'),
+
+        (0x8008396, 'fef780f9', 'c046c046'),
+
+        (0x8016184, 'fdf790fc', 'c046c046'),
+
+        (0x801B76C, '280b0508', '00000708'),
+
+        (0x8017AFC, 'bde8fc87', 'eef74fb8'),
+
+        (0x802F690, '9847fee7', 'c046c046'),
+
+        (0x801671C, '9847fee7', 'c046c046'),
+
+        (0x8013BAC, 'f8bd0a4a', 'f3f730b8'),
+
+        (0x801B6BE, 'bde8f081', 'ebf7c3ba'),
+
+        (0x8016720, '10bd0000', 'f0f7b2ba'),
+
+    ]:
+
+        assert hx(d, va) == exp, (hex(va), hx(d, va))
+
+        set4(d, va, new)
+
+    # Full bl idiom at 0x8006682 (bl + pop, 6B) -> NOPs (see b18).
+    o = off(0x8006682)
+
+    assert d[o:o + 6].hex() == '00f001f807bd', hx(d, 0x8006682, 6)
+
+    d[o:o + 6] = bytes.fromhex('c046c046c046')
+
+    o = off(0x8013AA8)
+
+    assert d[o:o + 4].hex() == '07f026be', hx(d, 0x8013AA8)
+
+    d[o:o + 4] = bytes.fromhex('c046c046')
+
+    o = off(0x8013BA6)
+
+    assert d[o:o + 2].hex() == 'b888', (hex(0x8013BA6), hx(d, 0x8013BA6, 2))
+
+    d[o:o + 2] = bytes.fromhex('ff20')
+
+    # Logger S8 (see b21).
+    o = off(0x8034810)
+
+    assert d[o:o + 4].hex() == 'bde8fc87', hx(d, 0x8034810)
+
+    d[o:o + 2] = bytes.fromhex('7047')
+
+    # Clock S11: pop{r4,pc} (2B 10bd) -> bx lr (2B 7047).
+    o = off(0x800E988)
+
+    assert d[o:o + 2].hex() == '10bd', hx(d, 0x800E988, 2)
+
+    d[o:o + 2] = bytes.fromhex('7047')
+
+    save(d, 'img0_b24.elf')
+
 
 
 
diff --git a/tools/sbl_uni.py b/tools/sbl_uni.py
index 92fec15..c0e36f7 100644
--- a/tools/sbl_uni.py
+++ b/tools/sbl_uni.py
@@ -158,7 +158,11 @@ def main():
                 inside = _elo <= addr < _ehi
                 if inside and not _inrng[_i]:
                     if len(elog) < 20000:
-                        elog.append((count[0], _prev[0], addr))
+                        try:
+                            _th = (mu.reg_read(_CPSR) >> 5) & 1
+                        except Exception:
+                            _th = -1
+                        elog.append((count[0], _prev[0], addr, _th))
                 _inrng[_i] = inside
             _prev[0] = addr
         if calls is not None and size in (2, 4):
@@ -331,6 +335,12 @@ def main():
     # PBL version-table fabrication (b23): [0x080528D0] = STUBV so the
     # rollback query's blx calls maze (returns 0 = versions OK).
     W32(0x080528D0, STUBV)
+    # PBL world-switch Thumb-stub (b24): the ARM trampoline at 0x221EF8
+    # is entered in Thumb (mode confusion at dispatch); real ARM would
+    # save regs/CPS to MON and call TZ (not loaded yet). Stub returns 0
+    # to the dispatcher via stale lr (TZ bringup deferred).
+    # NOTE: overwrites 4B of real ARM trampoline (recoverable from ELF).
+    mu.mem_write(0x00221EF8, bytes([0x00, 0x20, 0x70, 0x47]))
     # stack zone fill (STUBV odd)
     mu.mem_write(0x085F0000, struct.pack("<I", STUBV) * (0x10000 // 4))
     # pop-site slots (sp values from traces)
@@ -435,7 +445,7 @@ def main():
                 wlolog.append((pc, addr, size, value))
 
         mu.hook_add(UC_HOOK_MEM_WRITE, hook_wlo,
-                    begin=0x08000000, end=0x085FFFFF)
+                    begin=0x00200000, end=0x085FFFFF)
         import atexit as _ax2
 
         def _dwlo():
@@ -479,10 +489,10 @@ def main():
         print("hist:", [hex(pc) for pc, _ in list(hist)[-12:]])
     if elog is not None:
         print(f"entries: {len(elog)}")
-        for n, prev, cur in elog[:10]:
-            print(f"  FIRST insn#{n} {prev:#x} -> {cur:#x}")
-        for n, prev, cur in elog[-10:]:
-            print(f"  LAST insn#{n} {prev:#x} -> {cur:#x}")
+        for n, prev, cur, th in elog[:10]:
+            print(f"  FIRST insn#{n} {prev:#x} -> {cur:#x}{'t' if th == 1 else ('a' if th == 0 else '?')}")
+        for n, prev, cur, th in elog[-10:]:
+            print(f"  LAST insn#{n} {prev:#x} -> {cur:#x}{'t' if th == 1 else ('a' if th == 0 else '?')}")
     if _splog is not None:
         print(f"sp-highs: {len(_splog)}")
         for n, pc, sp in _splog: