diff --git a/web/src/wasm-core.js b/web/src/wasm-core.js
index c5ce82e..19debbe 100644
--- a/web/src/wasm-core.js
+++ b/web/src/wasm-core.js
@@ -499,6 +499,7 @@ function installOpfsWorkspace(module, options) {
       assertRelativePath(path);
       try {
         const data = await readOpfsFile(workspacePath, path);
+        cleanupLinuxCncParameterFiles(module);
         writeWasmFileReplacingPath(module, LINUXCNC_DEFAULT_PARAMETER_FILE, data);
         writeWasmFileReplacingPath(module, `/${LINUXCNC_DEFAULT_PARAMETER_FILE}`, data);
         return data;
diff --git a/web/test-browser-wasm-smoke-opfs-parameter-sections.js b/web/test-browser-wasm-smoke-opfs-parameter-sections.js
index 0b8dee8..643e74f 100644
--- a/web/test-browser-wasm-smoke-opfs-parameter-sections.js
+++ b/web/test-browser-wasm-smoke-opfs-parameter-sections.js
@@ -3,6 +3,7 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     expectErrorContaining,
     expectEvent,
     expectIncludes,
+    expectLinuxCncParameterScratchMissing,
     expectMissingOpfsFile,
     expectMissingWasmPath,
     expectNoEvent,
@@ -11,12 +12,19 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
     expectWasmFilesMissing,
     near,
     readOpfsText,
+    readWasmText,
     removeWasmPathIfExists,
     runSection,
     withSmokeSimulator,
   } = context;
   const backend = { backend: "linuxcnc-rs274" };
   const parseWithParameters = (program, path) => simulator.parseWithParameterFile(program, path, "linuxcnc", backend);
+  const g28BranchProgram = "G21 G90\nF100\nO10 if [#5161 EQ 1]\nG1 X9\nO10 endif\n";
+  const writeDefaultScratch = (main, temporary, backup) => {
+    simulator.fs.module.FS.writeFile("rs274ngc.var", main);
+    simulator.fs.module.FS.writeFile("rs274ngc.var.new", temporary);
+    simulator.fs.module.FS.writeFile("rs274ngc.var.bak", backup);
+  };
 
   await runSection("opfs parameter save", async () => {
     await simulator.parseWithParameterFile("G21 G90\nG0 X1\nG28.1\nM30\n", "parameters/rs274ngc.var", "linuxcnc", backend);
@@ -263,37 +271,23 @@ export async function runBrowserOpfsParameterSections(context, simulator) {
 
   await runSection("opfs stale parameter state cleanup", async () => {
     await simulator.fs.opfs.writeFile("parameters/stale-state.var", "5161\t1.000000\n");
-    const staleStateEvents = await simulator.parseWithParameterFile(
-      "G21 G90\nF100\nO10 if [#5161 EQ 1]\nG1 X9\nO10 endif\n",
-      "parameters/stale-state.var",
-      "linuxcnc",
-      backend,
-    );
-    expectEvent(staleStateEvents, (event) => event.type === "linear-feed" && near(event.end.x, 9),
-      "LinuxCNC did not honor the loaded OPFS parameter state");
+    const staleStateEvents = await simulator.parseWithParameterFile(g28BranchProgram, "parameters/stale-state.var", "linuxcnc", backend);
+    expectEvent(staleStateEvents, (event) => event.type === "linear-feed" && near(event.end.x, 9), "LinuxCNC did not honor the loaded OPFS parameter state");
     await simulator.fs.opfs.removeFile("parameters/stale-state.var");
-    const missingStateEvents = await simulator.parseWithParameterFile(
-      "G21 G90\nF100\nO10 if [#5161 EQ 1]\nG1 X9\nO10 endif\n",
-      "parameters/stale-state.var",
-      "linuxcnc",
-      backend,
-    );
-    expectNoEvent(missingStateEvents, (event) => event.type === "linear-feed" && near(event.end.x, 9),
-      "LinuxCNC stale OPFS parameter state was not cleared when the file was missing");
-    // LinuxCNC source basis: rs274ngc_pre.cc restore_parameters()
-    // treats a missing parameter file as OK; the browser OPFS bridge
-    // must not leave stale default parameter files in the WASM mirror.
-    simulator.fs.module.FS.writeFile("rs274ngc.var", "5161\t1.000000\n");
-    simulator.fs.module.FS.writeFile("rs274ngc.var.new", "stale temporary parameter file\n");
-    simulator.fs.module.FS.writeFile("rs274ngc.var.bak", "stale backup parameter file\n");
+    const missingStateEvents = await simulator.parseWithParameterFile(g28BranchProgram, "parameters/stale-state.var", "linuxcnc", backend);
+    expectNoEvent(missingStateEvents, (event) => event.type === "linear-feed" && near(event.end.x, 9), "LinuxCNC stale OPFS parameter state was not cleared when the file was missing");
+    // LinuxCNC source basis: rs274ngc_pre.cc restore_parameters() ignores
+    // missing files and reads only the configured parameter file.
+    writeDefaultScratch("5161\t1.000000\n", "stale temporary parameter file\n", "stale backup parameter file\n");
     const missingLoad = await simulator.fs.opfs.loadParameterFile("parameters/load-missing.var");
     if (missingLoad !== null) {
       throw new Error("missing OPFS parameter file did not return null");
     }
-    expectWasmFilesMissing(
-      simulator.fs.module.FS,
-      ["rs274ngc.var", "rs274ngc.var.new", "rs274ngc.var.bak"],
-      (parameterPath) => `missing OPFS parameter load left stale WASM file ${parameterPath}`,
-    );
+    expectLinuxCncParameterScratchMissing(simulator, (parameterPath) => `missing OPFS parameter load left stale WASM file ${parameterPath}`);
+    writeDefaultScratch("5161\t7.000000\n", "stale successful-load temporary parameter file\n", "stale successful-load backup parameter file\n");
+    await simulator.fs.opfs.writeFile("parameters/load-existing.var", "5161\t2.000000\n");
+    await simulator.fs.opfs.loadParameterFile("parameters/load-existing.var");
+    expectText(readWasmText(simulator, "rs274ngc.var"), "5161\t2.000000\n", "existing OPFS parameter load did not replace the LinuxCNC default parameter file");
+    expectWasmFilesMissing(simulator.fs.module.FS, ["rs274ngc.var.new", "rs274ngc.var.bak"], (parameterPath) => `existing OPFS parameter load left stale WASM file ${parameterPath}`);
   });
 }