diff --git a/wasm-port/docs/compatibility-validation.md b/wasm-port/docs/compatibility-validation.md
index c8db8bf..94fa335 100644
--- a/wasm-port/docs/compatibility-validation.md
+++ b/wasm-port/docs/compatibility-validation.md
@@ -195,10 +195,11 @@ INI parser smoke harness and an initial interpreter-core canonical event smoke
 for `minimal_linear`, `arc_semantics`, `length_units`, `modal_incremental`,
 `plane_selection`, `coordinate_offsets`, `g53_machine_coordinates`,
 `feed_control_modes`, `position_params`, `probe_semantics`, `spindle_orient`,
-`comment_logging`, and `numbered_params`. OPFS validation is limited to the
-JavaScript host-boundary adapter plus the INI browser smoke harness. Full
-browser coverage, full SDK coverage, and full machine-session validation remain
-future work.
+`comment_logging`, and `numbered_params`, plus the `g1_zero_feed`,
+`arc_radius_mismatch`, `arc_zero_radius`, and `g53_incremental` negative
+fixtures. OPFS validation is limited to the JavaScript host-boundary adapter
+plus the INI browser smoke harness. Full browser coverage, full SDK coverage,
+and full machine-session validation remain future work.
 
 The current fixture expectations validate standalone behavior against both the
 vendored LinuxCNC source path and an upstream `rs274` side-by-side baseline for
diff --git a/wasm-port/tests/wasm/node/verify_interp_wasm.mjs b/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
index c1fab56..b517a37 100644
--- a/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
+++ b/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
@@ -27,6 +27,28 @@ function runProgram(mod, programText) {
   }
 }
 
+function verifyExpectedOutput(fixtureName, output, expectedText) {
+  const expectedLines = expectedText.split("\n").filter(Boolean);
+
+  for (const expectedLine of expectedLines) {
+    if (expectedLine.startsWith("absent=")) {
+      const forbidden = expectedLine.slice("absent=".length);
+      assert.equal(
+        output.includes(forbidden),
+        false,
+        `${fixtureName}: unexpected ${forbidden}`,
+      );
+      continue;
+    }
+
+    assert.equal(
+      output.includes(expectedLine),
+      true,
+      `${fixtureName}: ${expectedLine}`,
+    );
+  }
+}
+
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
 const rootDir = resolve(__dirname, "../../..");
@@ -66,16 +88,26 @@ for (const fixtureName of fixtureNames) {
     "utf8",
   ).trimEnd();
 
-  const output = runProgram(interp, programText);
-  const actualLineSet = new Set(output.split("\n").filter(Boolean));
-  const expectedLines = expectedEvents.split("\n").filter(Boolean);
+  verifyExpectedOutput(fixtureName, runProgram(interp, programText), expectedEvents);
+}
 
-  for (const expectedLine of expectedLines) {
-    assert.equal(
-      actualLineSet.has(expectedLine),
-      true,
-      `${fixtureName}: ${expectedLine}`,
-    );
-  }
+const errorFixtureNames = [
+  "g1_zero_feed",
+  "arc_radius_mismatch",
+  "arc_zero_radius",
+  "g53_incremental",
+];
+
+for (const fixtureName of errorFixtureNames) {
+  const programText = readFileSync(
+    resolve(rootDir, `tests/fixtures/gcode_errors/${fixtureName}.ngc`),
+    "utf8",
+  );
+  const expectedOutput = readFileSync(
+    resolve(rootDir, `tests/fixtures/canon_errors/${fixtureName}.expected`),
+    "utf8",
+  ).trimEnd();
+
+  verifyExpectedOutput(fixtureName, runProgram(interp, programText), expectedOutput);
 }
 console.log("interp_wasm_node_smoke=ok");