diff --git a/test-linuxcnc-source-link.sh b/test-linuxcnc-source-link.sh
index da48530..40382bf 100755
--- a/test-linuxcnc-source-link.sh
+++ b/test-linuxcnc-source-link.sh
@@ -1423,6 +1423,25 @@ if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
 fi
 grep -q "Cannot wait for digital input with cutter radius compensation on" \
     "$output_dir/cnc_sim_linuxcnc_source_cutter_comp_wait_input_error.err"
+# Source basis: LinuxCNC src/emc/rs274ngc/interp_convert.cc
+# convert_m() rejects M63/M67/M49 while cutter radius compensation is active
+# before enqueueing digital/analog output or override canon side effects.
+cutter_comp_m_error_cases=(
+    "linuxcnc_cutter_comp_m63_error|Cannot set motion digital output with cutter radius compensation on"
+    "linuxcnc_cutter_comp_m67_error|Cannot set motion analog output with cutter radius compensation on"
+    "linuxcnc_cutter_comp_m49_error|Cannot disable overrides with cutter radius compensation on"
+)
+for case in "${cutter_comp_m_error_cases[@]}"; do
+    fixture=${case%%|*}
+    expected=${case#*|}
+    if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
+        "$build_dir/linuxcnc_rs274_source_dump" "tests/gcode/$fixture.ngc" \
+        >"$output_dir/cnc_sim_linuxcnc_source_$fixture.json" 2>"$output_dir/cnc_sim_linuxcnc_source_$fixture.err"; then
+        echo "expected $fixture.ngc to fail" >&2
+        exit 1
+    fi
+    grep -Fq "$expected" "$output_dir/cnc_sim_linuxcnc_source_$fixture.err"
+done
 if CNC_SIM_RS274_FILE_MODE=1 CNC_SIM_RS274_VAR="$var_file" \
     "$build_dir/linuxcnc_rs274_source_dump" tests/gcode/linuxcnc_cutter_comp_g71_error.ngc \
     >"$output_dir/cnc_sim_linuxcnc_source_cutter_comp_g71_error.json" 2>"$output_dir/cnc_sim_linuxcnc_source_cutter_comp_g71_error.err"; then
diff --git a/tests/gcode/linuxcnc_cutter_comp_m49_error.ngc b/tests/gcode/linuxcnc_cutter_comp_m49_error.ngc
new file mode 100644
index 0000000..2c38813
--- /dev/null
+++ b/tests/gcode/linuxcnc_cutter_comp_m49_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G41 D1
+M49
diff --git a/tests/gcode/linuxcnc_cutter_comp_m63_error.ngc b/tests/gcode/linuxcnc_cutter_comp_m63_error.ngc
new file mode 100644
index 0000000..bd70518
--- /dev/null
+++ b/tests/gcode/linuxcnc_cutter_comp_m63_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G41 D1
+M63 P1
diff --git a/tests/gcode/linuxcnc_cutter_comp_m67_error.ngc b/tests/gcode/linuxcnc_cutter_comp_m67_error.ngc
new file mode 100644
index 0000000..533094c
--- /dev/null
+++ b/tests/gcode/linuxcnc_cutter_comp_m67_error.ngc
@@ -0,0 +1,3 @@
+G21 G90 G17
+G41 D1
+M67 E0 Q1