diff --git a/measurement.html b/measurement.html
index a80bc50..31c5594 100644
--- a/measurement.html
+++ b/measurement.html
@@ -74,44 +74,50 @@
     oneditprepare: function() {
         const node = this;
 
-        // === Mode selector — TOP-LEVEL hierarchy ===
-        // The Input Mode drives whether analog-pipeline fields or the
-        // digital channels editor are shown. Initialize the <select> from
-        // the saved node value, fall back to 'analog' for legacy nodes
-        // that were saved before the mode field existed.
-        const modeSelect = document.getElementById('node-input-mode');
-        const initialMode = (node.mode === 'digital' || node.mode === 'analog') ? node.mode : 'analog';
-        modeSelect.value = initialMode;
+        // === Asset / logger / position placeholders (dynamic menus) ===
+        // Kick these off FIRST so that any error in the downstream mode
+        // logic can never block the shared menus. Historical regression:
+        // a ReferenceError in the mode block aborted oneditprepare and
+        // stopped the asset menu from rendering at all.
+        const waitForMenuData = () => {
+            if (window.EVOLV?.nodes?.measurement?.initEditor) {
+                window.EVOLV.nodes.measurement.initEditor(node);
+            } else {
+                setTimeout(waitForMenuData, 50);
+            }
+        };
+        waitForMenuData();
 
+        // IMPORTANT: all DOM references are resolved up front so helper
+        // functions called during initial applyMode() don't trip over the
+        // Temporal Dead Zone on later `const` declarations.
+
+        const modeSelect   = document.getElementById('node-input-mode');
         const analogBlock  = document.getElementById('analog-only-fields');
         const digitalBlock = document.getElementById('digital-only-fields');
         const modeHint     = document.getElementById('mode-hint');
+        const channelsArea = document.getElementById('node-input-channels');
+        const channelsHint = document.getElementById('channels-validation');
 
-        function applyMode(mode) {
-            const isDigital = mode === 'digital';
-            analogBlock.style.display  = isDigital ? 'none' : 'block';
-            digitalBlock.style.display = isDigital ? 'block' : 'none';
-            if (modeHint) {
-                modeHint.textContent = isDigital
-                    ? 'msg.payload must be an OBJECT, e.g. {"temperature": 22.5, "humidity": 45}. Define each key below.'
-                    : 'msg.payload must be a NUMBER (or numeric string). Configure scaling/smoothing below.';
-            }
-            validateChannelsJson();
-        }
+        // Initialise the mode <select> from the saved node.mode. Legacy
+        // nodes (saved before the mode field existed) fall back to
+        // 'analog' so they keep behaving exactly like before.
+        const initialMode = (node.mode === 'digital' || node.mode === 'analog') ? node.mode : 'analog';
+        if (modeSelect) modeSelect.value = initialMode;
 
-        modeSelect.addEventListener('change', (e) => applyMode(e.target.value));
-        applyMode(initialMode);
-
-        // === Channels JSON live validation (digital only) ===
-        const channelsArea  = document.getElementById('node-input-channels');
-        const channelsHint  = document.getElementById('channels-validation');
+        // Populate the channels textarea from the saved node.channels
+        // (stored as a raw JSON string; parsing happens server-side).
         if (channelsArea && typeof node.channels === 'string') {
             channelsArea.value = node.channels;
         }
+
         function validateChannelsJson() {
             if (!channelsHint) return;
-            if (modeSelect.value !== 'digital') { channelsHint.textContent = ''; return; }
-            const raw = (channelsArea.value || '').trim();
+            if (!modeSelect || modeSelect.value !== 'digital') {
+                channelsHint.textContent = '';
+                return;
+            }
+            const raw = (channelsArea && channelsArea.value || '').trim();
             if (!raw || raw === '[]') {
                 channelsHint.innerHTML = '<span style="color:#b45309;">Digital mode with no channels — no measurements will be emitted.</span>';
                 return;
@@ -120,7 +126,7 @@
                 const parsed = JSON.parse(raw);
                 if (!Array.isArray(parsed)) throw new Error('must be an array');
                 const missing = parsed
-                    .map((c, i) => (c && c.key && c.type ? null : `entry ${i}: missing key or type`))
+                    .map((c, i) => (c && c.key && c.type ? null : 'entry ' + i + ': missing key or type'))
                     .filter(Boolean);
                 if (missing.length) {
                     channelsHint.innerHTML = '<span style="color:#b45309;">' + missing.join('; ') + '</span>';
@@ -131,17 +137,24 @@
                 channelsHint.innerHTML = '<span style="color:#b91c1c;">Invalid JSON: ' + e.message + '</span>';
             }
         }
-        if (channelsArea) channelsArea.addEventListener('input', validateChannelsJson);
 
-        // === Asset / logger / position placeholders (dynamic menus) ===
-        const waitForMenuData = () => {
-            if (window.EVOLV?.nodes?.measurement?.initEditor) {
-                window.EVOLV.nodes.measurement.initEditor(node);
-            } else {
-                setTimeout(waitForMenuData, 50);
+        function applyMode(mode) {
+            const isDigital = mode === 'digital';
+            if (analogBlock)  analogBlock.style.display  = isDigital ? 'none' : 'block';
+            if (digitalBlock) digitalBlock.style.display = isDigital ? 'block' : 'none';
+            if (modeHint) {
+                modeHint.textContent = isDigital
+                    ? 'msg.payload must be an OBJECT, e.g. {"temperature": 22.5, "humidity": 45}. Define each key below.'
+                    : 'msg.payload must be a NUMBER (or numeric string). Configure scaling/smoothing below.';
             }
-        };
-        waitForMenuData();
+            validateChannelsJson();
+        }
+
+        if (modeSelect) modeSelect.addEventListener('change', (e) => applyMode(e.target.value));
+        if (channelsArea) channelsArea.addEventListener('input', validateChannelsJson);
+        try { applyMode(initialMode); } catch (e) {
+            console.error('measurement: applyMode failed', e);
+        }
 
         // === Smoothing method dropdown (analog only) ===
         const smoothMethodSelect = document.getElementById('node-input-smooth_method');