diff --git a/emulator/firmware-decomp/emu860.py b/emulator/firmware-decomp/emu860.py
index 0a8c501..c822800 100644
--- a/emulator/firmware-decomp/emu860.py
+++ b/emulator/firmware-decomp/emu860.py
@@ -126,6 +126,7 @@ class I860:
         self.stop = False
         self.stopmsg = ''
         self._branch = None               # (target, delayed?)
+        self._squash = False              # annul the next delay slot (bc.t/bnc.t not taken)
         self.tailn = 60                   # ring buffer of last-N executed
         self.tail = []
         self.stopat = set()               # halt when pc first reaches one of these
@@ -211,6 +212,7 @@ class I860:
             self.log(f"{pc:#010x}: {w:08x}  {m:<10} {ops}")
         dim_at_fetch = self._dim          # DIM-ness of a branch's slot is fixed at
         self._branch = None               # fetch (pair membership), not post-exec
+        self._squash = False              # cleared each fetch; set by a not-taken .t
         self.execute(w, pc)
         self.steps += 1
         self._dim_track(w, pc)
@@ -241,6 +243,14 @@ class I860:
             else:
                 self.pc = target
                 self._dim_half = 0
+        elif self._squash:
+            # bc.t / bnc.t NOT taken: the i860 annuls the delay-slot instruction
+            # (whole next PAIR in DIM). Skip it -- executing it corrupts loops whose
+            # exit relies on the slot NOT running (e.g. the registry tail-find walk,
+            # which only chains -- and only breaks -- above 512 live objects).
+            nslots = 2 if dim_at_fetch else 1
+            self._squash = False
+            self.pc = pc + 4 + nslots * 4
         else:
             self.pc = pc + 4
         return not self.stop
@@ -371,11 +381,17 @@ class I860:
             self.wr(1, pc + 8); self.branch(pc + 4 + s26(w & 0x03ffffff) * 4); return
         if op in (0x1c, 0x1d):            # bc / bc.t  (branch if CC)
             tgt = pc + 4 + s26(w & 0x03ffffff) * 4
-            if self.cc(): self.branch(tgt, delayed=(op == 0x1d))
+            if self.cc():
+                self.branch(tgt, delayed=(op == 0x1d))
+            elif op == 0x1d:              # bc.t not taken: i860 ANNULS the delay slot
+                self._squash = True
             return
         if op in (0x1e, 0x1f):            # bnc / bnc.t (branch if !CC)
             tgt = pc + 4 + s26(w & 0x03ffffff) * 4
-            if not self.cc(): self.branch(tgt, delayed=(op == 0x1f))
+            if not self.cc():
+                self.branch(tgt, delayed=(op == 0x1f))
+            elif op == 0x1f:              # bnc.t not taken: i860 ANNULS the delay slot
+                self._squash = True
             return
         if op in (0x14, 0x15, 0x16, 0x17):   # btne / bte  (compare & branch)
             broff = s16(((dest << 11) | (w & 0x7ff)) & 0xffff)