diff --git a/wasm-port/docs/compatibility-validation.md b/wasm-port/docs/compatibility-validation.md
index fc8a922..7021d6f 100644
--- a/wasm-port/docs/compatibility-validation.md
+++ b/wasm-port/docs/compatibility-validation.md
@@ -296,7 +296,9 @@ rejection, missing-file success, missing required numeric parameter defaulting,
 required numeric parameter writeback, removal of named-parameter-only lines
 from saved output, and the `.bak` backup produced by vendored
 `save_parameters()`, including browser OPFS readback of the backup text after
-the host bridge writes it to persistent storage. It also covers LinuxCNC tool-table
+the host bridge writes it to persistent storage, plus explicit host
+parameter-file override paths saved back to OPFS with their LinuxCNC-produced
+backup text. It also covers LinuxCNC tool-table
 load/save behavior through vendored `tooldata_common.cc`, including the
 non-random and random-toolchanger `tooldata_init()` branches, with the SDK
 only copying text into the Emscripten filesystem and calling the exported C
diff --git a/wasm-port/tests/browser/interp_smoke.html b/wasm-port/tests/browser/interp_smoke.html
index f4ced92..e079e90 100644
--- a/wasm-port/tests/browser/interp_smoke.html
+++ b/wasm-port/tests/browser/interp_smoke.html
@@ -703,6 +703,64 @@
           "tool_1.comment=browser explicit tool",
         ].join("\n"),
       );
+      const savedExplicitParameters = await saveMachineParametersToOpfs(
+        interp,
+        "browser-ini-override-session",
+        {
+          5161: 51.25,
+          5162: 102.5,
+          5220: 1.0,
+          5221: 7.5,
+          5399: 202,
+        },
+        {
+          opfsPath: loadedIniOverrideSession.parameters.opfsPath,
+          wasmPath: loadedIniOverrideSession.parameters.wasmPath,
+        },
+      );
+      if (
+        savedExplicitParameters.opfsPath !==
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit.var"
+      ) {
+        throw new Error(`unexpected explicit saved parameter path: ${savedExplicitParameters.opfsPath}`);
+      }
+      if (
+        savedExplicitParameters.backupOpfsPath !==
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit.var.bak"
+      ) {
+        throw new Error(`unexpected explicit backup path: ${savedExplicitParameters.backupOpfsPath}`);
+      }
+      verifyExpectedOutput(
+        "opfs_save_explicit_parameter_file",
+        savedExplicitParameters.result,
+        [
+          "save_parameters=0",
+          "parameter_5161=51.25",
+          "parameter_5162=102.5",
+          "parameter_5221=7.5",
+          "parameter_5399=202",
+        ].join("\n"),
+      );
+      verifyExpectedOutput(
+        "opfs_saved_explicit_parameter_text",
+        await loadTextFile(loadedIniOverrideSession.parameters.opfsPath),
+        [
+          "5161\t51.250000",
+          "5162\t102.500000",
+          "5221\t7.500000",
+          "5399\t202.000000",
+        ].join("\n"),
+      );
+      verifyExpectedOutput(
+        "opfs_saved_explicit_parameter_backup_text",
+        await loadTextFile(savedExplicitParameters.backupOpfsPath),
+        [
+          "5161 41.25",
+          "5162 82.5",
+          "5221 6.5",
+          "5399 101",
+        ].join("\n"),
+      );
 
       await saveMachineTextFiles("browser-invalid-param-file-session", {
         ini: [