diff --git a/docs/v4.0.0/DECOMPOSITION.md b/docs/v4.0.0/DECOMPOSITION.md
index 3bb171be..8c66fa0f 100644
--- a/docs/v4.0.0/DECOMPOSITION.md
+++ b/docs/v4.0.0/DECOMPOSITION.md
@@ -379,8 +379,8 @@ Section numbers match the v3 primitive reference.
 | `OR` | CAP | §4 |
 | `INVERT` | OP | `inv` |
 | `NOT` | CAP | `0=` (FORTH-79 logical not, as in v3) |
-| `LSHIFT` | CAP | `BEGIN dup WHILE 1- SWAP 2* SWAP REPEAT drop` |
-| `RSHIFT` | CAP | `BEGIN dup WHILE 1- SWAP 2/ MSB inv and SWAP REPEAT drop` (clears the sign bit each step; `MSB` is the cell-width top-bit constant) |
+| `LSHIFT` | CAP | `BEGIN dup WHILE 1- SWAP 2* SWAP REPEAT drop` — executed on the golden model (2026-10-03). |
+| `RSHIFT` | CAP | `BEGIN dup WHILE 1- SWAP 2/ MSB inv and SWAP REPEAT drop` (clears the sign bit each step; `MSB` is the cell-width top-bit constant) — executed on the golden model (2026-10-03). |
 | `0=` `0<` | CAP | §4 |
 | `0<>` | CAP | `0= 0=` |
 | `0>` | CAP | `dup 0< SWAP 0= OR 0=` (correct for the most negative number) |
diff --git a/v4/tests/test_foundation.c b/v4/tests/test_foundation.c
index c6b0b1d9..991b0482 100644
--- a/v4/tests/test_foundation.c
+++ b/v4/tests/test_foundation.c
@@ -81,7 +81,8 @@ static v4_cell w_nip, w_swap, w_or, w_negate, w_rot, w_zless, w_zequal,
                w_qfromint, w_qtoint, w_less, w_equal, w_dless, w_2swap, w_2over,
                w_dmax, w_dmin, w_qgt_doc, w_qgt, w_dltkeep, w_qstar, w_d2starc, w_uqdiv, w_qslash, w_qexp, w_qsqrt, w_qlog,
                w_qreduce, w_qsin, l_trig, w_qcos,
-               w_q1, w_q0, w_qscale, w_q1_times, w_q0_plus, w_q1_toint, w_one_fromint;
+               w_q1, w_q0, w_qscale, w_q1_times, w_q0_plus, w_q1_toint, w_one_fromint,
+               w_lshift, w_rshift;
 
 #define O(name)  v4_asm_op(&as, V4_OP_##name)
 #define LIT(v)   v4_asm_lit(&as, (v4_cell)(v))
@@ -1325,6 +1326,32 @@ static void build(void)
 #undef Q_ZERO
 #undef Q_ONE
 
+    /* : LSHIFT ( x n -- x<<n )  BEGIN dup WHILE 1- SWAP 2* SWAP REPEAT drop ;      5.5
+     * : RSHIFT ( x n -- x>>n )  BEGIN dup WHILE 1- SWAP 2/ MSB inv and SWAP REPEAT drop ;
+     * As written.  Section 2 expands BEGIN ... WHILE ... REPEAT as it does IF:
+     *   L0: dup if L1  drop <body> jump L0   L1: drop
+     * 1- is in line (-1 +); SWAP is a call. */
+    {
+        v4_cell l0;
+        v4_asm_ref l1;
+        w_lshift = v4_asm_label(&as);
+        l0 = v4_asm_label(&as);
+        O(DUP); l1 = v4_asm_branch_fwd(&as, V4_OP_IF);
+        O(DROP); LIT(-1); O(ADD); CALL(w_swap); O(TWO_STAR); CALL(w_swap);
+        v4_asm_branch(&as, V4_OP_JUMP, l0);
+        v4_asm_resolve(&as, l1, v4_asm_label(&as));
+        O(DROP); O(DROP); O(SEMI);
+
+        w_rshift = v4_asm_label(&as);
+        l0 = v4_asm_label(&as);
+        O(DUP); l1 = v4_asm_branch_fwd(&as, V4_OP_IF);
+        O(DROP); LIT(-1); O(ADD); CALL(w_swap);
+        O(TWO_SLASH); LIT((v4_cell)V4_MSB); O(INV); O(AND); CALL(w_swap);
+        v4_asm_branch(&as, V4_OP_JUMP, l0);
+        v4_asm_resolve(&as, l1, v4_asm_label(&as));
+        O(DROP); O(DROP); O(SEMI);
+    }
+
     CHECK(v4_asm_ok(&as), "foundation words assemble");
 }
 
@@ -2589,6 +2616,17 @@ int main(void)
         }
     }
 
+    /* LSHIFT and RSHIFT as written, against C, for every count 0 .. N (a
+     * count of N must give 0). */
+    for (unsigned i = 0; i < NVEC; i++)
+        for (unsigned c = 0; c <= V4_CELL_BITS; c++) {
+            v4_ucell u = (v4_ucell)vec[i];
+            v4_ucell l = c < V4_CELL_BITS ? u << c : 0u;
+            v4_ucell r = c < V4_CELL_BITS ? u >> c : 0u;
+            CHECK(call(w_lshift, 2, vec[i], (v4_cell)c, 0) && left1((v4_cell)l), "LSHIFT [%u,%u]", i, c);
+            CHECK(call(w_rshift, 2, vec[i], (v4_cell)c, 0) && left1((v4_cell)r), "RSHIFT [%u,%u]", i, c);
+        }
+
     /* Q./ at the overflow boundary: |a| * 2^16 against |b| * 2^(2N-1), for
      * divisors around 2^16 and 2^17, every sign. */
     {
@@ -2717,6 +2755,9 @@ int main(void)
             CHECK(dh >= 2 && rh >= 2, "Q.SIN leaves room");
             headroom("Q.COS", w_qcos, 2, qtrig_args, 6, 2, &dh, &rh);
             CHECK(dh >= 2 && rh >= 2, "Q.COS leaves room");
+            static const v4_cell shift_args[][4] = { { -1, 0, 0, 0 }, { -1, 5, 0, 0 }, { 12345, 31, 0, 0 } };
+            headroom("LSHIFT", w_lshift, 2, shift_args, 3, 1, &dh, &rh);
+            headroom("RSHIFT", w_rshift, 2, shift_args, 3, 1, &dh, &rh);
             headroom("SM/REM", w_smrem, 3, smrem_args, 5, 2, &dh, &rh);
             CHECK(rh >= 1, "SM/REM leaves room for /MOD's return address");
             headroom("/MOD", w_slashmod, 2, slashmod_args, 4, 2, &dh, &rh);