diff --git a/apps/tests/phase100_mutable_accumulator_min.hako b/apps/tests/phase100_mutable_accumulator_min.hako
new file mode 100644
index 00000000..58e63832
--- /dev/null
+++ b/apps/tests/phase100_mutable_accumulator_min.hako
@@ -0,0 +1,16 @@
+static box Main {
+    main() {
+        local out = ""
+        local count = 0
+        local i = 0
+        loop(i < 10) {
+            if i >= 3 { break }
+            local ch = "x"
+            out = out + ch
+            count = count + 1
+            i = i + 1
+        }
+        print(count)
+        return 0
+    }
+}
diff --git a/tools/smokes/v2/profiles/integration/apps/phase100_mutable_accumulator_vm.sh b/tools/smokes/v2/profiles/integration/apps/phase100_mutable_accumulator_vm.sh
new file mode 100644
index 00000000..5becfe32
--- /dev/null
+++ b/tools/smokes/v2/profiles/integration/apps/phase100_mutable_accumulator_vm.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+# Phase 100 P2 - Mutable Accumulator (VM backend)
+# Tests: out = out + ch (string accumulator) and count = count + 1 (integer accumulator)
+
+HAKO_FILE="apps/tests/phase100_mutable_accumulator_min.hako"
+BACKEND="vm"
+EXPECTED_OUTPUT="3"
+
+ACTUAL_OUTPUT=$(HAKO_JOINIR_STRICT=1 ./target/release/hakorune --backend "$BACKEND" "$HAKO_FILE" 2>&1 | grep -E '^[0-9]+$')
+
+if [ "$ACTUAL_OUTPUT" = "$EXPECTED_OUTPUT" ]; then
+    echo "✅ PASS: phase100_mutable_accumulator_vm"
+    exit 0
+else
+    echo "❌ FAIL: phase100_mutable_accumulator_vm"
+    echo "Expected:"
+    echo "$EXPECTED_OUTPUT"
+    echo "Got:"
+    echo "$ACTUAL_OUTPUT"
+    echo "---Full output (last 80 lines):---"
+    HAKO_JOINIR_STRICT=1 ./target/release/hakorune --backend "$BACKEND" "$HAKO_FILE" 2>&1 | tail -n 80
+    exit 1
+fi