diff --git a/wasm-port/docs/compatibility-validation.md b/wasm-port/docs/compatibility-validation.md
index bc7eaf6..2240f2c 100644
--- a/wasm-port/docs/compatibility-validation.md
+++ b/wasm-port/docs/compatibility-validation.md
@@ -93,7 +93,10 @@ Emscripten filesystem through the SDK and runs them through LinuxCNC
 file execution path. The same Node smoke writes LinuxCNC-format parameter
 files into the Emscripten filesystem and validates vendored
 `Interp::restore_parameters()` and `Interp::save_parameters()`, including the
-saved parameter values and `.bak` backup file boundary.
+saved parameter values and `.bak` backup file boundary. It also writes the
+negative G-code fixtures into the Emscripten filesystem and verifies their
+LinuxCNC-produced error text through the `Interp::open()`/`read()`/`execute()`
+file path.
 
 The OPFS host-boundary script validates the JavaScript file-service adapter
 with a Node mock of the browser File System Access handles. It covers nested
@@ -260,6 +263,9 @@ path additionally covers the same canonical-event fixture group, plus
 `position_params` uses a dedicated file-path expectation under
 `tests/fixtures/canon_file/` because LinuxCNC file execution advances the
 post-execute position parameters differently than the line-by-line MDI smoke.
+The same Node WASM file-path smoke also covers the negative fixture group and
+checks the LinuxCNC file-execution error text plus absent canonical motion
+constraints where applicable.
 The Node WASM interpreter smoke also covers LinuxCNC parameter-file
 restore/save behavior through the exported C ABI, including out-of-order file
 rejection, missing-file success, required numeric parameter writeback, removal
@@ -356,6 +362,19 @@ Node WASM file-path coverage currently includes:
 - `position_params` through the dedicated `canon_file/` expectation
 - `namedparam_semantics` through the INI-aware file ABI
 
+Node WASM file-path negative coverage currently includes every fixture under
+`tests/fixtures/gcode_errors/`:
+
+- `g1_zero_feed`
+- `arc_radius_mismatch`
+- `arc_zero_radius`
+- `cutter_comp_plane_change`
+- `g53_incremental`
+- `namedparam_readonly`
+- `numbered_param_readonly`
+- `tool_length_offset_not_found`
+- `tool_not_found`
+
 Browser interpreter `Interp::execute()` coverage currently includes:
 
 - `minimal_linear`
diff --git a/wasm-port/tests/wasm/node/verify_interp_wasm.mjs b/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
index 62b1e8e..0895230 100644
--- a/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
+++ b/wasm-port/tests/wasm/node/verify_interp_wasm.mjs
@@ -34,6 +34,45 @@ function verifyExpectedOutput(fixtureName, output, expectedText) {
   }
 }
 
+function verifyExpectedFileError(fixtureName, output, expectedText) {
+  assert.equal(
+    output.includes("file_open=0"),
+    true,
+    `${fixtureName}: file open`,
+  );
+
+  const expectedLines = expectedText.split("\n").filter(Boolean);
+  for (const expectedLine of expectedLines) {
+    if (expectedLine.startsWith("absent=")) {
+      const forbidden = expectedLine.slice("absent=".length);
+      assert.equal(
+        output.includes(forbidden),
+        false,
+        `${fixtureName}: unexpected ${forbidden}`,
+      );
+      continue;
+    }
+
+    if (expectedLine.startsWith("error_text=")) {
+      const message = expectedLine.slice("error_text=".length);
+      assert.equal(
+        output.includes(`file_error_text=${message}`),
+        true,
+        `${fixtureName}: ${message}`,
+      );
+      continue;
+    }
+
+    if (expectedLine.startsWith("canon_event=")) {
+      assert.equal(
+        output.includes(expectedLine),
+        true,
+        `${fixtureName}: ${expectedLine}`,
+      );
+    }
+  }
+}
+
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
 const rootDir = resolve(__dirname, "../../..");
@@ -92,6 +131,21 @@ for (const fixtureName of INTERP_ERROR_FIXTURES) {
   verifyExpectedOutput(fixtureName, interp.runProgram(programText), expectedOutput);
 }
 
+for (const fixtureName of INTERP_ERROR_FIXTURES) {
+  const programPath = `/work/${fixtureName}-error.ngc`;
+  const programText = readFileSync(
+    resolve(rootDir, `tests/fixtures/gcode_errors/${fixtureName}.ngc`),
+    "utf8",
+  );
+  const expectedOutput = readFileSync(
+    resolve(rootDir, `tests/fixtures/canon_errors/${fixtureName}.expected`),
+    "utf8",
+  ).trimEnd();
+
+  interp.writeTextFile(programPath, programText);
+  verifyExpectedFileError(fixtureName, interp.runFile(programPath), expectedOutput);
+}
+
 for (const fixtureName of INTERP_FILE_FIXTURES) {
   const programPath = `/work/${fixtureName}.ngc`;
   const programText = readFileSync(