diff --git a/wasm-port/docs/compatibility-validation.md b/wasm-port/docs/compatibility-validation.md
index 49efeab..f9bf129 100644
--- a/wasm-port/docs/compatibility-validation.md
+++ b/wasm-port/docs/compatibility-validation.md
@@ -67,6 +67,7 @@ Positive G-code fixtures currently cover:
 - position parameters
 - canned cycles
 - coordinate offsets
+- G53 machine-coordinate motion
 - feed and motion control modes
 - probing
 - threading and rigid tap
@@ -84,6 +85,7 @@ Negative fixtures currently cover:
 - zero-feed `G1`
 - arc radius mismatch
 - zero-radius arc
+- G53 incremental-mode rejection
 - read-only named parameter writes
 - read-only numbered parameter writes
 - missing tool
diff --git a/wasm-port/docs/porting-steps-standalone.md b/wasm-port/docs/porting-steps-standalone.md
index abff659..a2dea1f 100644
--- a/wasm-port/docs/porting-steps-standalone.md
+++ b/wasm-port/docs/porting-steps-standalone.md
@@ -402,6 +402,13 @@ Current verified progress:
   `tests/fixtures/canon/cutter_comp_motion.events` pin positive `G41.1`/`G40`
   compensated straight-feed output through vendored `interp_convert.cc` and
   `interp_queue.cc`.
+- `tests/fixtures/gcode/g53_machine_coordinates.ngc` and
+  `tests/fixtures/canon/g53_machine_coordinates.events` pin `G53` machine
+  coordinate straight-traverse behavior through vendored
+  `interp_find.cc::find_ends()` and `interp_convert.cc::convert_straight()`.
+  `tests/fixtures/gcode_errors/g53_incremental.ngc` and
+  `tests/fixtures/canon_errors/g53_incremental.expected` pin the LinuxCNC
+  rejection path for `G53` while incremental distance mode is active.
 - `runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp` now records
   feed/control canonical boundary calls emitted by vendored LinuxCNC
   conversion and queue code: `SET_TRAVERSE_RATE`, `SET_FEED_REFERENCE`,
diff --git a/wasm-port/docs/scope-and-baseline.md b/wasm-port/docs/scope-and-baseline.md
index 5a560cf..e38f814 100644
--- a/wasm-port/docs/scope-and-baseline.md
+++ b/wasm-port/docs/scope-and-baseline.md
@@ -40,6 +40,7 @@ G-code fixture coverage includes:
 - position parameters
 - canned cycles
 - coordinate offsets
+- G53 machine-coordinate motion
 - feed and motion control modes
 - cutter compensation motion
 - probe semantics
@@ -58,6 +59,7 @@ Negative fixture coverage includes:
 - arc radius mismatch
 - zero-radius arc
 - cutter compensation plane-change rejection
+- G53 incremental-mode rejection
 - read-only named parameter writes
 - read-only numbered parameter writes
 - missing tool
diff --git a/wasm-port/tests/fixtures/canon/g53_machine_coordinates.events b/wasm-port/tests/fixtures/canon/g53_machine_coordinates.events
new file mode 100644
index 0000000..ce98524
--- /dev/null
+++ b/wasm-port/tests/fixtures/canon/g53_machine_coordinates.events
@@ -0,0 +1,5 @@
+canon_event=SELECT_PLANE plane=1
+canon_event=STRAIGHT_TRAVERSE line=1 x=5 y=5 z=5 a=0 b=0 c=0 u=0 v=0 w=0
+canon_event=STRAIGHT_TRAVERSE line=2 x=1 y=2 z=3 a=0 b=0 c=0 u=0 v=0 w=0
+canon_event=SET_FEED_RATE rate=90
+canon_event=STRAIGHT_FEED line=3 x=4 y=5 z=6 a=0 b=0 c=0 u=0 v=0 w=0
diff --git a/wasm-port/tests/fixtures/canon_errors/g53_incremental.expected b/wasm-port/tests/fixtures/canon_errors/g53_incremental.expected
new file mode 100644
index 0000000..b157c9b
--- /dev/null
+++ b/wasm-port/tests/fixtures/canon_errors/g53_incremental.expected
@@ -0,0 +1,5 @@
+execute_line_1=0
+execute_line_2=5
+error_text=Cannot use g53 incremental
+canon_event=COMMENT: interpreter: distance mode changed to incremental
+absent=canon_event=STRAIGHT_TRAVERSE line=2
diff --git a/wasm-port/tests/fixtures/gcode/g53_machine_coordinates.ngc b/wasm-port/tests/fixtures/gcode/g53_machine_coordinates.ngc
new file mode 100644
index 0000000..ef92e6c
--- /dev/null
+++ b/wasm-port/tests/fixtures/gcode/g53_machine_coordinates.ngc
@@ -0,0 +1,3 @@
+G90 G17 G0 X5 Y5 Z5
+G53 G0 X1 Y2 Z3
+G1 X4 Y5 Z6 F90
diff --git a/wasm-port/tests/fixtures/gcode_errors/g53_incremental.ngc b/wasm-port/tests/fixtures/gcode_errors/g53_incremental.ngc
new file mode 100644
index 0000000..6c4a1f5
--- /dev/null
+++ b/wasm-port/tests/fixtures/gcode_errors/g53_incremental.ngc
@@ -0,0 +1,2 @@
+G91
+G53 G0 X1