diff --git a/wasm-port/docs/compatibility-validation.md b/wasm-port/docs/compatibility-validation.md
index 159e9c8..0126e1d 100644
--- a/wasm-port/docs/compatibility-validation.md
+++ b/wasm-port/docs/compatibility-validation.md
@@ -105,7 +105,9 @@ OPFS-to-WASM parameter-file bridge with a mock interpreter SDK to ensure the
 host boundary copies text into and out of the WASM filesystem without defining
 parameter semantics, and that INI-derived machine file names are still
 rejected by the OPFS path model when they contain traversal or nested path
-segments.
+segments. The same Node smoke also validates that explicit session file-name
+options take precedence over INI-derived parameter and tool-table file names,
+keeping host override policy outside CNC semantics.
 
 The browser INI/OPFS smoke script serves `wasm-port/` over localhost and runs
 Chromium headless against a test page that imports the JS SDK, loads the INI
@@ -125,7 +127,10 @@ storage plus the interpreter SDK to restore and save a LinuxCNC parameter file
 through vendored `Interp::restore_parameters()` and `Interp::save_parameters()`,
 to load/save LinuxCNC tool tables through vendored `tooldata_common.cc`, and
 to reject invalid INI-derived parameter/tool-table file names through the OPFS
-path model after the names are parsed by the LinuxCNC-backed INI WASM SDK.
+path model after the names are parsed by the LinuxCNC-backed INI WASM SDK. It
+also verifies that explicit session parameter/tool-table file-name options
+override INI-derived names before OPFS text is copied into the LinuxCNC-backed
+WASM filesystem.
 
 The aggregate host smoke script builds the INI and interpreter-core WASM
 artifacts once, then runs the Node WASM smokes, the Node OPFS mock smoke, and
@@ -262,9 +267,10 @@ groups INI, parameter, and tool-table loading, the random-toolchanger flag
 derived from vendored LinuxCNC INI boolean parsing, INI-derived
 `[RS274NGC]PARAMETER_FILE` and `[EMCIO]TOOL_TABLE` file names mapped to OPFS
 machine files, OPFS path-model rejection of invalid INI-derived file names,
-and a browser interpreter smoke that uses the same session bridge with real
-LinuxCNC INI WASM parsing before saving OPFS-backed parameter and tool-table
-text through vendored LinuxCNC file APIs.
+explicit host session file-name overrides taking precedence over INI-derived
+names, and a browser interpreter smoke that uses the same session bridge with
+real LinuxCNC INI WASM parsing before saving OPFS-backed parameter and
+tool-table text through vendored LinuxCNC file APIs.
 Full browser coverage, full SDK coverage, and richer machine-state validation
 remain future work.
 
diff --git a/wasm-port/docs/drift-report.md b/wasm-port/docs/drift-report.md
index 2cfbb3b..db18a01 100644
--- a/wasm-port/docs/drift-report.md
+++ b/wasm-port/docs/drift-report.md
@@ -44,7 +44,7 @@ semantic rewrites:
 | Kinematics component lifecycle | Kinematics modules are initialized through LinuxCNC module entry points where native runtime probes exist, while HAL component init/ready/exit, HAL pin allocation, and RTAPI module metadata are handled by standalone shims. |
 | Go math C/C++ linkage | `genserkins` runtime probing compiles vendored `gomath.c` through a narrow C++ wrapper so LinuxCNC `genserfuncs.c` can link to the upstream Go math symbols without editing vendored source. |
 | Switchkins iterative forward | `genhexkins` runtime probing follows LinuxCNC switchkins iterative-forward behavior, including the first-call warmup path before asserting roundtrip convergence. |
-| Browser storage | OPFS remains outside the native core; `runtime/opfs/file-service.js` owns browser text-file persistence, `runtime/opfs/path-model.js` owns host-side storage paths for INI, tool table, parameter, G-code, preview-cache, and session-snapshot content, `runtime/opfs/snapshot-store.js` owns generic JSON session snapshot persistence, `runtime/opfs/machine-file-store.js` owns pure-text machine-file and G-code persistence, `runtime/opfs/linuxcnc-parameter-bridge.js` only copies parameter files between OPFS text storage and the LinuxCNC-backed WASM parameter-file ABI, `runtime/opfs/linuxcnc-tool-table-bridge.js` only copies tool tables between OPFS text storage and the LinuxCNC-backed WASM tool-table ABI, and `runtime/opfs/linuxcnc-machine-session-bridge.js` groups INI, parameter, and tool-table loading while using the LinuxCNC-backed INI SDK for `[EMCIO]RANDOM_TOOLCHANGER`, `[RS274NGC]PARAMETER_FILE`, and `[EMCIO]TOOL_TABLE` when available; path validation remains owned by the OPFS path model, including rejection of traversal or nested path segments from INI-derived file names. |
+| Browser storage | OPFS remains outside the native core; `runtime/opfs/file-service.js` owns browser text-file persistence, `runtime/opfs/path-model.js` owns host-side storage paths for INI, tool table, parameter, G-code, preview-cache, and session-snapshot content, `runtime/opfs/snapshot-store.js` owns generic JSON session snapshot persistence, `runtime/opfs/machine-file-store.js` owns pure-text machine-file and G-code persistence, `runtime/opfs/linuxcnc-parameter-bridge.js` only copies parameter files between OPFS text storage and the LinuxCNC-backed WASM parameter-file ABI, `runtime/opfs/linuxcnc-tool-table-bridge.js` only copies tool tables between OPFS text storage and the LinuxCNC-backed WASM tool-table ABI, and `runtime/opfs/linuxcnc-machine-session-bridge.js` groups INI, parameter, and tool-table loading while using the LinuxCNC-backed INI SDK for `[EMCIO]RANDOM_TOOLCHANGER`, `[RS274NGC]PARAMETER_FILE`, and `[EMCIO]TOOL_TABLE` when available; explicit host session file-name options take precedence over INI-derived file names, and path validation remains owned by the OPFS path model, including rejection of traversal or nested path segments from INI-derived file names. |
 
 ## Enforced Non-Drift Rules
 
@@ -69,9 +69,9 @@ semantic rewrites:
 - OPFS validation covers a Node mock of the file-service adapter, the
   host-side path model, generic session snapshot storage, pure-text machine
   file and G-code storage, parameter/tool-table bridge copying into the
-  interpreter SDK filesystem, grouped machine-session loading, invalid
-  INI-derived machine file names, and a Chromium localhost round trip for those
-  persistence paths.
+  interpreter SDK filesystem, grouped machine-session loading, explicit
+  session file-name overrides, invalid INI-derived machine file names, and a
+  Chromium localhost round trip for those persistence paths.
 - Host-side smoke validation is aggregated by
   `tests/host/verify_host_smokes.sh` so Node, WASM, OPFS, and browser checks
   run from one command.
diff --git a/wasm-port/docs/source-reuse-map.md b/wasm-port/docs/source-reuse-map.md
index 9354db3..a3771ab 100644
--- a/wasm-port/docs/source-reuse-map.md
+++ b/wasm-port/docs/source-reuse-map.md
@@ -54,7 +54,7 @@ Current validation is intentionally mechanical:
 
 | Dependency | LinuxCNC files that expose it | Standalone treatment |
 | --- | --- | --- |
-| Native file IO | `inifile.cc`, `rs274ngc_pre.cc`, `tooldata_common.cc`, parameter file paths, tool table paths | Allowed in native probes; the interpreter WASM C ABI validates parameter-file restore/save by calling vendored `Interp::restore_parameters()` and `Interp::save_parameters()` and tool-table load/save by calling vendored `tooldata_load()` and `tooldata_save()` against Emscripten filesystem paths; browser OPFS remains a host-side adapter under `runtime/opfs/`, with path ownership in `runtime/opfs/path-model.js`, generic snapshot persistence in `runtime/opfs/snapshot-store.js`, pure-text machine-file persistence in `runtime/opfs/machine-file-store.js`, OPFS-to-WASM parameter-file copying in `runtime/opfs/linuxcnc-parameter-bridge.js`, OPFS-to-WASM tool-table copying in `runtime/opfs/linuxcnc-tool-table-bridge.js`, and grouped INI/parameter/tool-table session loading in `runtime/opfs/linuxcnc-machine-session-bridge.js`, including INI-derived `[RS274NGC]PARAMETER_FILE` and `[EMCIO]TOOL_TABLE` OPFS filename selection through the LinuxCNC-backed INI SDK; OPFS path validation rejects traversal and nested segments before host storage access |
+| Native file IO | `inifile.cc`, `rs274ngc_pre.cc`, `tooldata_common.cc`, parameter file paths, tool table paths | Allowed in native probes; the interpreter WASM C ABI validates parameter-file restore/save by calling vendored `Interp::restore_parameters()` and `Interp::save_parameters()` and tool-table load/save by calling vendored `tooldata_load()` and `tooldata_save()` against Emscripten filesystem paths; browser OPFS remains a host-side adapter under `runtime/opfs/`, with path ownership in `runtime/opfs/path-model.js`, generic snapshot persistence in `runtime/opfs/snapshot-store.js`, pure-text machine-file persistence in `runtime/opfs/machine-file-store.js`, OPFS-to-WASM parameter-file copying in `runtime/opfs/linuxcnc-parameter-bridge.js`, OPFS-to-WASM tool-table copying in `runtime/opfs/linuxcnc-tool-table-bridge.js`, and grouped INI/parameter/tool-table session loading in `runtime/opfs/linuxcnc-machine-session-bridge.js`, including INI-derived `[RS274NGC]PARAMETER_FILE` and `[EMCIO]TOOL_TABLE` OPFS filename selection through the LinuxCNC-backed INI SDK; explicit host session file-name options take precedence over INI-derived names, and OPFS path validation rejects traversal and nested segments before host storage access |
 | RTAPI | `rtapi_*.h`, TP, posemath, motion headers | Minimal standalone shim in `runtime/core/shims/rtapi.h` |
 | NML transport | `emc.hh`, motion/NML type headers | Transport is not ported; only the status/type edges needed by vendored compute code are exposed through standalone shims and probes |
 | HAL runtime | named parameter lookup, kinematics component lifecycle, and runtime status edges | Standalone HAL adapter under `runtime/core/linuxcnc_wrap/` |
@@ -95,7 +95,9 @@ Current validation is intentionally mechanical:
   tool-table loading into one host-side session load boundary and can derive
   the random-toolchanger tooldata mode from `[EMCIO]RANDOM_TOOLCHANGER` plus
   parameter/tool-table OPFS file names from `[RS274NGC]PARAMETER_FILE` and
-  `[EMCIO]TOOL_TABLE` through the LinuxCNC-backed INI SDK, with invalid
-  traversal or nested file names rejected by `runtime/opfs/path-model.js`.
-  Full machine-state restoration remains future work.
+  `[EMCIO]TOOL_TABLE` through the LinuxCNC-backed INI SDK. Explicit host
+  session file-name options take precedence over those INI-derived names, with
+  invalid traversal or nested file names rejected by
+  `runtime/opfs/path-model.js`. Full machine-state restoration remains future
+  work.
 - Native LinuxCNC GUI code remains out of scope for implementation.
diff --git a/wasm-port/tests/browser/interp_smoke.html b/wasm-port/tests/browser/interp_smoke.html
index ff27744..30e6db8 100644
--- a/wasm-port/tests/browser/interp_smoke.html
+++ b/wasm-port/tests/browser/interp_smoke.html
@@ -412,6 +412,82 @@
         ].join("\n"),
       );
 
+      await saveMachineTextFiles("browser-ini-override-session", {
+        ini: [
+          "[EMC]",
+          "MACHINE = browser-ini-override-session",
+          "",
+          "[RS274NGC]",
+          "PARAMETER_FILE = browser-ignored.var",
+          "",
+          "[EMCIO]",
+          "TOOL_TABLE = browser-ignored-tool.tbl",
+          "",
+        ].join("\n"),
+      });
+      await saveTextFile(
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit.var",
+        [
+          "5161 41.25",
+          "5162 82.5",
+          "5220 1",
+          "5221 6.5",
+          "5399 101",
+          "",
+        ].join("\n"),
+      );
+      await saveTextFile(
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit-tool.tbl",
+        "T9 P9 Z5.5 D0.625 ;browser explicit tool\n",
+      );
+      const loadedIniOverrideSession = await loadMachineSessionFromOpfs(
+        interp,
+        "browser-ini-override-session",
+        {
+          iniSdk: ini,
+          iniWasmPath: "/work/browser-ini-override-session.ini",
+          parameterFilename: "browser-explicit.var",
+          parameterWasmPath: "/work/browser-explicit.var",
+          toolTableFilename: "browser-explicit-tool.tbl",
+          toolTableWasmPath: "/work/browser-explicit-tool.tbl",
+        },
+      );
+      if (
+        loadedIniOverrideSession.parameters.opfsPath !==
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit.var"
+      ) {
+        throw new Error(`unexpected explicit parameter path: ${loadedIniOverrideSession.parameters.opfsPath}`);
+      }
+      if (
+        loadedIniOverrideSession.toolTable.opfsPath !==
+        "linuxcnc/machines/browser-ini-override-session/browser-explicit-tool.tbl"
+      ) {
+        throw new Error(`unexpected explicit tool path: ${loadedIniOverrideSession.toolTable.opfsPath}`);
+      }
+      verifyExpectedOutput(
+        "opfs_load_explicit_parameter_file",
+        loadedIniOverrideSession.parameters.result,
+        [
+          "restore_parameters=0",
+          "parameter_5161=41.25",
+          "parameter_5162=82.5",
+          "parameter_5221=6.5",
+          "parameter_5399=101",
+        ].join("\n"),
+      );
+      verifyExpectedOutput(
+        "opfs_load_explicit_tool_table",
+        loadedIniOverrideSession.toolTable.result,
+        [
+          "tooldata_load=0",
+          "tool_1.toolno=9",
+          "tool_1.pocketno=9",
+          "tool_1.z=5.5",
+          "tool_1.diameter=0.625",
+          "tool_1.comment=browser explicit tool",
+        ].join("\n"),
+      );
+
       await saveMachineTextFiles("browser-invalid-param-file-session", {
         ini: [
           "[EMC]",
diff --git a/wasm-port/tests/opfs/node/verify_file_service.mjs b/wasm-port/tests/opfs/node/verify_file_service.mjs
index 5713a4e..8617bc3 100644
--- a/wasm-port/tests/opfs/node/verify_file_service.mjs
+++ b/wasm-port/tests/opfs/node/verify_file_service.mjs
@@ -209,6 +209,13 @@ const bridgeIniSdk = {
     ) {
       return "custom.var";
     }
+    if (
+      path === "/work/ini-override-session.ini" &&
+      section === "RS274NGC" &&
+      tag === "PARAMETER_FILE"
+    ) {
+      return "ignored.var";
+    }
     if (
       path === "/work/invalid-ini-file-session.ini" &&
       section === "RS274NGC" &&
@@ -223,6 +230,13 @@ const bridgeIniSdk = {
     ) {
       return "custom-tool.tbl";
     }
+    if (
+      path === "/work/ini-override-session.ini" &&
+      section === "EMCIO" &&
+      tag === "TOOL_TABLE"
+    ) {
+      return "ignored-tool.tbl";
+    }
     if (
       path === "/work/invalid-tool-file-session.ini" &&
       section === "EMCIO" &&
@@ -430,6 +444,53 @@ assert.equal(
   "tooldata_load=0\nload_tool_path=/work/ini-file-session-tool.tbl\nrandom_toolchanger=0\n",
 );
 
+await saveMachineTextFiles("ini-override-session", {
+  ini: [
+    "[EMC]",
+    "MACHINE = ini-override-session",
+    "",
+    "[RS274NGC]",
+    "PARAMETER_FILE = ignored.var",
+    "",
+    "[EMCIO]",
+    "TOOL_TABLE = ignored-tool.tbl",
+    "",
+  ].join("\n"),
+}, { storage });
+await saveTextFile(
+  "linuxcnc/machines/ini-override-session/explicit.var",
+  "5161 11.0\n5162 22.0\n",
+  storage,
+);
+await saveTextFile(
+  "linuxcnc/machines/ini-override-session/explicit-tool.tbl",
+  "T3 P3 Z1.75 D0.375\n",
+  storage,
+);
+const loadedIniOverrideSession = await loadMachineSessionFromOpfs(
+  bridgeInterp,
+  "ini-override-session",
+  {
+    storage,
+    iniSdk: bridgeIniSdk,
+    iniWasmPath: "/work/ini-override-session.ini",
+    parameterFilename: "explicit.var",
+    parameterWasmPath: "/work/ini-override-session.var",
+    toolTableFilename: "explicit-tool.tbl",
+    toolTableWasmPath: "/work/ini-override-session-tool.tbl",
+  },
+);
+assert.equal(
+  loadedIniOverrideSession.parameters.opfsPath,
+  "linuxcnc/machines/ini-override-session/explicit.var",
+);
+assert.equal(
+  loadedIniOverrideSession.toolTable.opfsPath,
+  "linuxcnc/machines/ini-override-session/explicit-tool.tbl",
+);
+assert.equal(bridgeFiles.get("/work/ini-override-session.var"), "5161 11.0\n5162 22.0\n");
+assert.equal(bridgeFiles.get("/work/ini-override-session-tool.tbl"), "T3 P3 Z1.75 D0.375\n");
+
 await saveMachineTextFiles("invalid-ini-file-session", {
   ini: [
     "[EMC]",