diff --git a/src/js/w-axis-view.js b/src/js/a-axis-view.js
similarity index 66%
rename from src/js/w-axis-view.js
rename to src/js/a-axis-view.js
index d4a4360..132ec4d 100644
--- a/src/js/w-axis-view.js
+++ b/src/js/a-axis-view.js
@@ -1,16 +1,16 @@
 "use strict";
 
-// V09 W-axis page \u2014 mounts the existing WAxisSettings Svelte component
+// V09 A-axis page — mounts the AAxisSettings Svelte component
 // inside the settings shell so it gets a real top-level rail entry
 // instead of being a soft-link anchor inside Display & Units.
 
 module.exports = {
-    template: "#w-axis-view-template",
+    template: "#a-axis-view-template",
 
     attached: function () {
         this.svelteComponent = SvelteComponents.createComponent(
-            "WAxisSettings",
-            document.getElementById("w-axis-mount")
+            "AAxisSettings",
+            document.getElementById("a-axis-mount")
         );
     },
 
diff --git a/src/js/app.js b/src/js/app.js
index b0acb98..f8d54f9 100644
--- a/src/js/app.js
+++ b/src/js/app.js
@@ -369,7 +369,7 @@ module.exports = new Vue({
     ready: function() {
         window.onhashchange = () => this.parse_hash();
 
-        // Embedded Svelte subviews (W axis settings, etc.) signal
+        // Embedded Svelte subviews (A axis settings, etc.) signal
         // unsaved changes via this event. The master Save button
         // highlights when modified is true.
         window.addEventListener("onefin:dirty", () => {
@@ -391,7 +391,7 @@ module.exports = new Vue({
             "admin-general", "admin-network",
             "motor", "tool", "io", "macros",
             "help", "cheat-sheet",
-            "w-axis",
+            "a-axis",
         ];
         const initialHead = (location.hash || "").replace(/^#/, "").split(":")[0];
         if (settingsFamily.indexOf(initialHead) === -1) {
@@ -627,7 +627,7 @@ module.exports = new Vue({
                 "admin-general", "admin-network",
                 "motor", "tool", "io", "macros",
                 "help", "cheat-sheet",
-                "w-axis",
+                "a-axis",
             ];
 
             if (head == "control") {
@@ -690,7 +690,7 @@ module.exports = new Vue({
             try {
                 await api.put("config/save", this.config);
                 // Notify any embedded Svelte subviews that own their
-                // own persistence (W axis -> aux.json, etc.) that
+                // own persistence (A axis -> aux.json, etc.) that
                 // the user just hit the master Save button. They
                 // listen for `onefin:save-all` and PUT their state.
                 try {
diff --git a/src/js/settings-shell-view.js b/src/js/settings-shell-view.js
index 1c0bea4..299b9d6 100644
--- a/src/js/settings-shell-view.js
+++ b/src/js/settings-shell-view.js
@@ -24,7 +24,7 @@ module.exports = {
     "io-view":                 require("./io-view"),
     "macros-view":             require("./macros"),
     "help-view":               require("./help-view"),
-    "w-axis-view":             require("./w-axis-view"),
+    "a-axis-view":             require("./a-axis-view"),
     "cheat-sheet-view": {
       template: "#cheat-sheet-view-template",
       data: function () {
@@ -58,10 +58,8 @@ module.exports = {
         { sub: "motor", motor: 2, href: "#motor:2", icon: "fa-arrows-up-down-left-right", label: "Motor 2" },
         { sub: "motor", motor: 3, href: "#motor:3", icon: "fa-arrows-up-down-left-right", label: "Motor 3" },
         // Auxiliary axis (auxcnc ESP32 - exposed to gplan as A).
-        // Mounts the WAxisSettings Svelte component on its own page.
-        // The route slug stays "#w-axis" for back-compat with any
-        // bookmarks; the visible label and tab content say "A Axis".
-        { sub: "w-axis", href: "#w-axis", icon: "fa-arrows-up-down", label: "A Axis" },
+        // Mounts the AAxisSettings Svelte component on its own page.
+        { sub: "a-axis", href: "#a-axis", icon: "fa-arrows-up-down", label: "A Axis" },
         { section: " " },
         { sub: "help",           href: "#help",           icon: "fa-circle-question", label: "Help" },
       ],
@@ -139,7 +137,7 @@ module.exports = {
         // layout, which under tablet mode pulls the fixed header out
         // of view.
         if (location.hash !== item.href) location.hash = item.href;
-        this._w_axis_focus = (item.sub === "w-axis");
+        this._a_axis_focus = (item.sub === "a-axis");
         const reset = () => {
           // Force any inadvertent ancestor scroll back to 0 before
           // we move .settings-content explicitly.
@@ -162,7 +160,7 @@ module.exports = {
           requestAnimationFrame(reset);
         }, 320);
       } else {
-        this._w_axis_focus = false;
+        this._a_axis_focus = false;
         if (location.hash !== item.href) location.hash = item.href;
         // Reset .app-body scroll so each route starts at the top.
         const body = document.querySelector(".app-body");
diff --git a/src/pug/templates/a-axis-view.pug b/src/pug/templates/a-axis-view.pug
new file mode 100644
index 0000000..2e61cc4
--- /dev/null
+++ b/src/pug/templates/a-axis-view.pug
@@ -0,0 +1,4 @@
+script#a-axis-view-template(type="text/x-template")
+  #a-axis-page
+    h1 A Axis (auxcnc)
+    #a-axis-mount
diff --git a/src/pug/templates/control-view.pug b/src/pug/templates/control-view.pug
index 4a4d8b7..0e082e3 100644
--- a/src/pug/templates/control-view.pug
+++ b/src/pug/templates/control-view.pug
@@ -249,7 +249,7 @@ script#control-view-template(type="text/x-template")
                   @click=`home('${axis}')`)
                   .fa.fa-home
 
-          // Legacy W axis row - shown only when the auxcnc stepper is
+          // Legacy auxiliary-axis row - shown only when the auxcnc stepper is
           // *not* exposed as a virtual A axis. After v2 the standard
           // A row above renders this axis natively (with full offset
           // + set-position support); this row only appears on legacy
diff --git a/src/pug/templates/settings-shell.pug b/src/pug/templates/settings-shell.pug
index 091068a..a889b38 100644
--- a/src/pug/templates/settings-shell.pug
+++ b/src/pug/templates/settings-shell.pug
@@ -46,7 +46,7 @@ script#settings-shell-view-template(type="text/x-template")
         :index="index", :config="config", :template="template", :state="state")
       io-view(v-if="sub === 'io' && config_ready",
         :index="index", :config="config", :template="template", :state="state")
-      w-axis-view(v-if="sub === 'w-axis' && config_ready",
+      a-axis-view(v-if="sub === 'a-axis' && config_ready",
         :index="index", :config="config", :template="template", :state="state")
       macros-view(v-if="sub === 'macros' && config_ready",
         :index="index", :config="config", :template="template", :state="state")
diff --git a/src/pug/templates/w-axis-view.pug b/src/pug/templates/w-axis-view.pug
deleted file mode 100644
index 8b5728f..0000000
--- a/src/pug/templates/w-axis-view.pug
+++ /dev/null
@@ -1,4 +0,0 @@
-script#w-axis-view-template(type="text/x-template")
-  #w-axis-page
-    h1 W Axis (auxcnc)
-    #w-axis-mount
diff --git a/src/py/bbctrl/AuxAxis.py b/src/py/bbctrl/AuxAxis.py
index 1ba39e0..d0d16ba 100644
--- a/src/py/bbctrl/AuxAxis.py
+++ b/src/py/bbctrl/AuxAxis.py
@@ -40,8 +40,8 @@ DEFAULTS = {
     # 4th axis). gcode uses A for moves; the host ExternalAxis layer
     # forks A motion to the ESP transparently.
     'axis_letter':       'a',
-    'min_w':             0.0,     # soft limit min (mm), exposed as 4tn
-    'max_w':             100.0,   # soft limit max (mm), exposed as 4tm
+    'min_mm':            0.0,     # soft limit min (mm), exposed as 4tn
+    'max_mm':            100.0,   # soft limit max (mm), exposed as 4tm
     # Per-axis kinematic limits used to populate the planner's config.
     # Units match the bbctrl/onefinity per-motor convention so the
     # values are directly comparable to motors 0-3:
@@ -120,23 +120,61 @@ class AuxAxis(object):
     def _config_path(self):
         return self.ctrl.get_path(filename='aux.json')
 
+    # Legacy aux.json fields that have been renamed for clarity.
+    # Loaded values are migrated up on every load/save so existing
+    # installs keep working without operator intervention.
+    _LEGACY_FIELD_MAP = {
+        'min_w': 'min_mm',
+        'max_w': 'max_mm',
+    }
+
+    def _migrate_legacy_fields(self, cfg):
+        """In-place rename of legacy keys in `cfg` (dict). Returns
+        True if anything was migrated, so callers can decide whether
+        to persist the upgraded form.
+        """
+        migrated = False
+        for old, new in self._LEGACY_FIELD_MAP.items():
+            if old in cfg:
+                if new not in cfg:
+                    cfg[new] = cfg[old]
+                del cfg[old]
+                migrated = True
+        return migrated
+
     def _load_config(self):
         path = self._config_path()
         if os.path.exists(path):
             try:
                 with open(path) as f:
                     user = json.load(f)
+                migrated = self._migrate_legacy_fields(user)
                 # Be permissive; ignore unknown keys.
                 for k, v in user.items():
                     if k in self._cfg:
                         self._cfg[k] = v
                 self.log.info('Loaded aux config from %s' % path)
+                if migrated:
+                    # Persist the upgraded form so future restarts
+                    # see the new field names directly.
+                    try:
+                        self.save_config(self._cfg)
+                        self.log.info(
+                            'Migrated aux.json legacy fields '
+                            '(min_w/max_w -> min_mm/max_mm)')
+                    except Exception:
+                        self.log.warning(
+                            'Could not persist aux.json migration')
             except Exception:
                 self.log.error('Failed to read aux.json: %s'
                                % traceback.format_exc())
 
     def save_config(self, cfg):
         merged = dict(DEFAULTS)
+        # Accept legacy keys from callers that may still send the
+        # old names (older UI bundles, hand-edited POSTs).
+        cfg = dict(cfg)
+        self._migrate_legacy_fields(cfg)
         for k, v in cfg.items():
             if k in DEFAULTS:
                 merged[k] = v
@@ -317,8 +355,8 @@ class AuxAxis(object):
             raise AuxAxisError('Aux axis not connected')
 
     def _check_limits(self, target_mm):
-        lo = float(self._cfg['min_w'])
-        hi = float(self._cfg['max_w'])
+        lo = float(self._cfg['min_mm'])
+        hi = float(self._cfg['max_mm'])
         if hi <= lo:
             return  # no limits
         if target_mm < lo - 1e-6 or target_mm > hi + 1e-6:
diff --git a/src/py/bbctrl/Config.py b/src/py/bbctrl/Config.py
index 53118f2..173c88a 100644
--- a/src/py/bbctrl/Config.py
+++ b/src/py/bbctrl/Config.py
@@ -216,6 +216,32 @@ class Config(object):
                 defaults = json.load(f)
                 config['selected-tool-settings'] = defaults['selected-tool-settings'];
 
+        # Auxiliary axis nomenclature: rename W -> A in macro names and
+        # filenames. The auxcnc-driven stepper has been integrated into
+        # gplan as A since the option-b migration; old configs may
+        # still carry W Down/W Up macro entries pointing at
+        # w_down.nc/w_up.nc which were renamed on disk to a_down.nc /
+        # a_up.nc. Migrate idempotently on every load so a stale
+        # in-memory copy can never reintroduce the old names.
+        macros = config.get('macros') if isinstance(config, dict) else None
+        if isinstance(macros, list):
+            renames = {
+                'w_down.nc': 'a_down.nc',
+                'w_up.nc':   'a_up.nc',
+            }
+            display_renames = {
+                'W Down': 'A Down',
+                'W Up':   'A Up',
+            }
+            for m in macros:
+                if not isinstance(m, dict): continue
+                fn = m.get('file_name')
+                if isinstance(fn, str) and fn in renames:
+                    m['file_name'] = renames[fn]
+                nm = m.get('name')
+                if isinstance(nm, str) and nm in display_renames:
+                    m['name'] = display_renames[nm]
+
         config['version'] = self.version.split('b')[0]
         config['full_version'] = self.version
 
diff --git a/src/py/bbctrl/ExternalAxis.py b/src/py/bbctrl/ExternalAxis.py
index 4cca7b9..ac2c691 100644
--- a/src/py/bbctrl/ExternalAxis.py
+++ b/src/py/bbctrl/ExternalAxis.py
@@ -146,8 +146,8 @@ class ExternalAxis(object):
         """Return (min_mm, max_mm) in machine coords, or (None, None)
         if soft limits are disabled (max <= min)."""
         try:
-            lo = float(self.aux._cfg.get('min_w', 0.0))
-            hi = float(self.aux._cfg.get('max_w', 0.0))
+            lo = float(self.aux._cfg.get('min_mm', 0.0))
+            hi = float(self.aux._cfg.get('max_mm', 0.0))
         except Exception:
             return (None, None)
         if hi <= lo:
@@ -230,8 +230,8 @@ class ExternalAxis(object):
 
         # Soft limits in machine units (mm). State.get_soft_limit_vector
         # returns these directly, no scaling.
-        st.set(i + 'tn', float(cfg.get('min_w', 0.0)))
-        st.set(i + 'tm', float(cfg.get('max_w', 0.0)))
+        st.set(i + 'tn', float(cfg.get('min_mm', 0.0)))
+        st.set(i + 'tm', float(cfg.get('max_mm', 0.0)))
 
         # home_position / home_travel are exposed as callbacks for
         # motors 0..3 (see State.__init__). Register the same lazy
@@ -242,7 +242,7 @@ class ExternalAxis(object):
             i + 'home_position', lambda name: self.home_position_mm)
         st.set_callback(
             i + 'home_travel',
-            lambda name: float(self.aux._cfg.get('max_w', 0.0))
+            lambda name: float(self.aux._cfg.get('max_mm', 0.0))
                        - self.home_position_mm)
 
         # Misc fields that other code paths might query. Defaults
diff --git a/src/svelte-components/src/components/WAxisSettings.svelte b/src/svelte-components/src/components/AAxisSettings.svelte
similarity index 95%
rename from src/svelte-components/src/components/WAxisSettings.svelte
rename to src/svelte-components/src/components/AAxisSettings.svelte
index afed7fa..9c8c02f 100644
--- a/src/svelte-components/src/components/WAxisSettings.svelte
+++ b/src/svelte-components/src/components/AAxisSettings.svelte
@@ -6,9 +6,9 @@
     // Mirrors the DEFAULTS in src/py/bbctrl/AuxAxis.py. The "enabled"
     // flag is read-only here; toggling the auxiliary A axis on/off
     // is done via aux.json on disk, so adding/removing the hardware
-    // doesn't have a surprise UI that bricks bring-up. Field names
-    // (min_w/max_w) keep the historical "w" prefix for back-compat
-    // with existing aux.json files - rename happens at display only.
+    // doesn't have a surprise UI that bricks bring-up. Legacy aux.json
+    // files using min_w/max_w are migrated up to min_mm/max_mm by
+    // AuxAxis._migrate_legacy_fields on load.
     type AuxConfig = {
         enabled: boolean;
         port: string;
@@ -16,8 +16,8 @@
         steps_per_mm: number;
         dir_sign: number;
         axis_letter: string;
-        min_w: number;
-        max_w: number;
+        min_mm: number;
+        max_mm: number;
         max_feed_mm_min: number;
         max_velocity_m_per_min: number;
         max_accel_km_per_min2: number;
@@ -88,9 +88,9 @@
     }
 </script>
 
-<div class="w-axis-settings">
+<div class="a-axis-settings">
     {#if !cfg}
-        <p class="tip">Loading auxiliary A axis configuration...</p>
+        <p class="tip">Loading A axis configuration...</p>
     {:else}
         <div class="status">
             {#if status}
@@ -154,14 +154,14 @@
                 </div>
 
                 <div class="pure-control-group" title="Soft-limit minimum in mm.">
-                    <label for="min_w">soft min</label>
-                    <input id="min_w" type="number" bind:value={cfg.min_w} step="any" />
+                    <label for="min_mm">soft min</label>
+                    <input id="min_mm" type="number" bind:value={cfg.min_mm} step="any" />
                     <label for="" class="units">mm</label>
                 </div>
 
                 <div class="pure-control-group" title="Soft-limit maximum in mm.">
-                    <label for="max_w">soft max</label>
-                    <input id="max_w" type="number" bind:value={cfg.max_w} step="any" />
+                    <label for="max_mm">soft max</label>
+                    <input id="max_mm" type="number" bind:value={cfg.max_mm} step="any" />
                     <label for="" class="units">mm</label>
                 </div>
             </fieldset>
@@ -273,7 +273,7 @@
 </div>
 
 <style lang="scss">
-    .w-axis-settings {
+    .a-axis-settings {
         .status {
             margin-bottom: 1em;
             font-size: 90%;
diff --git a/src/svelte-components/src/components/SettingsView.svelte b/src/svelte-components/src/components/SettingsView.svelte
index 3a424b3..40c0012 100644
--- a/src/svelte-components/src/components/SettingsView.svelte
+++ b/src/svelte-components/src/components/SettingsView.svelte
@@ -2,10 +2,10 @@
     import configTemplate from "../../../resources/config-template.json";
     import ScreenRotationDialog from "$dialogs/ScreenRotationDialog.svelte";
     import ConfigTemplatedInput from "./ConfigTemplatedInput.svelte";
-    // WAxisSettings is mounted directly by the V09 settings shell at
-    // #w-axis instead of being embedded here — see
-    // src/pug/templates/w-axis-view.pug.
-    // import WAxisSettings from "./WAxisSettings.svelte";
+    // AAxisSettings is mounted directly by the V09 settings shell at
+    // #a-axis instead of being embedded here — see
+    // src/pug/templates/a-axis-view.pug.
+    // import AAxisSettings from "./AAxisSettings.svelte";
     import SetTimeDialog from "$dialogs/SetTimeDialog.svelte";
     import Button, { Label } from "@smui/button";
 
@@ -99,7 +99,7 @@
         </fieldset>
 
         <!-- W Axis (auxcnc) is now its own routed page in the V09
-             settings shell (#w-axis). Keep the SettingsView free of
+             settings shell (#a-axis). Keep the SettingsView free of
              that section so we don't render it twice. -->
 
         <h2 id="sec-path-accuracy" data-sec="gcode">Path Accuracy</h2>
diff --git a/src/svelte-components/src/main.ts b/src/svelte-components/src/main.ts
index 14d3d61..cf077fa 100644
--- a/src/svelte-components/src/main.ts
+++ b/src/svelte-components/src/main.ts
@@ -6,7 +6,7 @@ matchAll.shim();
 import AdminNetworkView from "$components/AdminNetworkView.svelte";
 import SettingsView from "$components/SettingsView.svelte";
 import HelpView from "$components/HelpView.svelte";
-import WAxisSettings from "$components/WAxisSettings.svelte";
+import AAxisSettings from "$components/AAxisSettings.svelte";
 import DialogHost, { showDialog } from "$dialogs/DialogHost.svelte";
 import { handleConfigUpdate, setDisplayUnits } from "$lib/ConfigStore";
 import { handleControllerStateUpdate } from "$lib/ControllerState";
@@ -23,8 +23,8 @@ export function createComponent(component: string, target: HTMLElement, props: R
         case "HelpView":
             return new HelpView({ target, props });
 
-        case "WAxisSettings":
-            return new WAxisSettings({ target, props });
+        case "AAxisSettings":
+            return new AAxisSettings({ target, props });
 
         case "DialogHost":
             return new DialogHost({ target, props });