diff --git a/classifier/js/app.js b/classifier/js/app.js
index f3ebfe9..5612465 100644
--- a/classifier/js/app.js
+++ b/classifier/js/app.js
@@ -145,6 +145,7 @@
             hideCompliantLabel: document.getElementById('hideCompliantLabel'),
             classifyFilters: document.getElementById('classifyFilters'),
             showUnassignedCheckbox: document.getElementById('showUnassignedCheckbox'),
+            showPartialCheckbox: document.getElementById('showPartialCheckbox'),
             showAssignedCheckbox: document.getElementById('showAssignedCheckbox'),
             showExcludedCheckbox: document.getElementById('showExcludedCheckbox'),
             showEmptyCheckbox: document.getElementById('showEmptyCheckbox'),
@@ -354,13 +355,14 @@
             if (app.modules.tree && app.modules.tree.setShowFilters) {
                 app.modules.tree.setShowFilters({
                     unassigned: app.dom.showUnassignedCheckbox.checked,
+                    partial: app.dom.showPartialCheckbox.checked,
                     assigned: app.dom.showAssignedCheckbox.checked,
                     excluded: app.dom.showExcludedCheckbox.checked,
                     empty: app.dom.showEmptyCheckbox.checked,
                 });
             }
         }
-        [app.dom.showUnassignedCheckbox, app.dom.showAssignedCheckbox, app.dom.showExcludedCheckbox, app.dom.showEmptyCheckbox]
+        [app.dom.showUnassignedCheckbox, app.dom.showPartialCheckbox, app.dom.showAssignedCheckbox, app.dom.showExcludedCheckbox, app.dom.showEmptyCheckbox]
             .forEach(function (cb) { if (cb) cb.addEventListener('change', pushClassifyFilters); });
 
         // Collapse tree button
diff --git a/classifier/js/tree.js b/classifier/js/tree.js
index b2a37e7..2c90106 100644
--- a/classifier/js/tree.js
+++ b/classifier/js/tree.js
@@ -41,29 +41,35 @@
     // excluded — and three "Show …" toggles control which buckets are visible
     // (so unchecking Assigned+Excluded leaves only what's left to do). A folder
     // whose whole scanned subtree is filtered away is itself hidden.
-    var showFilters = { unassigned: true, assigned: true, excluded: true };
+    var showFilters = { unassigned: true, partial: true, assigned: true, excluded: true };
     var showEmpty = true;   // show folders that contain no files
     function setShowFilters(f) {
         showFilters = {
             unassigned: f.unassigned !== false,
+            partial: f.partial !== false,
             assigned: f.assigned !== false,
             excluded: f.excluded !== false,
         };
         showEmpty = f.empty !== false;
         render();
     }
-    function allFiltersOn() { return showFilters.unassigned && showFilters.assigned && showFilters.excluded; }
+    function allFiltersOn() { return showFilters.unassigned && showFilters.partial && showFilters.assigned && showFilters.excluded; }
     function activeAxis() {
         var tt = window.app.modules.targetTree;
         return (tt && tt.activeAxis) ? tt.activeAxis() : 'tracking';
     }
-    // Bucket a file relative to the active axis: 'excluded' | 'assigned' | 'unassigned'.
+    // Bucket a file relative to the active axis:
+    //   'excluded' | 'assigned' (on this axis) | 'partial' (assigned on the OTHER
+    //   axis only — the to-do for this tab) | 'unassigned' (neither axis).
     function fileCategory(file) {
         var c = window.app.modules.classify;
         var a = c.getAssignment(c.srcKeyForFile(file));
         if (a && a.excluded) return 'excluded';
-        var assigned = a && (activeAxis() === 'transmittal' ? a.transmittalNodeId : a.trackingNodeId);
-        return assigned ? 'assigned' : 'unassigned';
+        var onTransmittal = activeAxis() === 'transmittal';
+        var here = a && (onTransmittal ? a.transmittalNodeId : a.trackingNodeId);
+        if (here) return 'assigned';
+        var other = a && (onTransmittal ? a.trackingNodeId : a.transmittalNodeId);
+        return other ? 'partial' : 'unassigned';
     }
     function classifyAllows(file) { return !classifyOn() || !!showFilters[fileCategory(file)]; }
 
@@ -142,9 +148,9 @@
     }
     function updateFilterCounts() {
         if (!classifyOn()) return;
-        var n = { unassigned: 0, assigned: 0, excluded: 0 };
+        var n = { unassigned: 0, partial: 0, assigned: 0, excluded: 0 };
         allClassifyFiles().forEach(function (f) { n[fileCategory(f)]++; });
-        ['unassigned', 'assigned', 'excluded'].forEach(function (k) {
+        ['unassigned', 'partial', 'assigned', 'excluded'].forEach(function (k) {
             var el = document.getElementById('show' + k.charAt(0).toUpperCase() + k.slice(1) + 'Count');
             if (el) el.textContent = '(' + n[k] + ')';
         });
diff --git a/classifier/template.html b/classifier/template.html
index f5c63a8..b093d74 100644
--- a/classifier/template.html
+++ b/classifier/template.html
@@ -65,11 +65,15 @@
                     </div>
                     <div id="classifyFilters" class="classify-filters tree-toolbar" hidden>
                         <span class="tree-toolbar__label">Show</span>
-                        <label class="checkbox-label" title="Files not yet assigned in the active tab">
+                        <label class="checkbox-label" title="Not assigned on either axis">
                             <input type="checkbox" id="showUnassignedCheckbox" checked>
                             Unassigned <span class="filter-count" id="showUnassignedCount"></span>
                         </label>
-                        <label class="checkbox-label" title="Files already assigned in the active tab">
+                        <label class="checkbox-label" title="Assigned in the OTHER tab but not this one — the to-do for this tab">
+                            <input type="checkbox" id="showPartialCheckbox" checked>
+                            Partial <span class="filter-count" id="showPartialCount"></span>
+                        </label>
+                        <label class="checkbox-label" title="Already assigned in the active tab">
                             <input type="checkbox" id="showAssignedCheckbox" checked>
                             Assigned <span class="filter-count" id="showAssignedCount"></span>
                         </label>
diff --git a/tests/classify.spec.js b/tests/classify.spec.js
index 024fc0f..d55117f 100644
--- a/tests/classify.spec.js
+++ b/tests/classify.spec.js
@@ -1007,3 +1007,24 @@ test('revision cell links to preview its file and shows no count bubble', async
     expect(r.previewKey).toBe('foundation.pdf');
     expect(r.hasBadge).toBe(false);           // no count bubble
 });
+
+test('Show Partial surfaces files assigned in the other tab only', async ({ page }) => {
+    await page.click('#modeClassifyBtn');
+    const r = await page.evaluate(() => {
+        const c = window.app.modules.classify, tree = window.app.modules.tree, tt = window.app.modules.targetTree;
+        c.reset();
+        const f = { originalFilename: 'a', extension: 'pdf', folderPath: 'Docs' };
+        window.app.folderTree = [{ name: 'Docs', path: 'Docs', expanded: true, scanState: 'done', children: [], files: [f] }];
+        // Assign tracking only, then view the TRANSMITTAL tab → it reads as "partial" there.
+        const leaf = c.addTrackingPath(null, c.parseFolderLevels('ACME-MECH-0001_A (IFR)'));
+        c.place([c.srcKeyForFile(f)], leaf, 'tracking');
+        tt.showTab('transmittal');
+        tree.render();
+        const withPartial = !!document.querySelector('#folderTree .file-item');
+        tree.setShowFilters({ unassigned: true, partial: false, assigned: true, excluded: true });
+        const withoutPartial = !!document.querySelector('#folderTree .file-item');
+        return { withPartial, withoutPartial };
+    });
+    expect(r.withPartial).toBe(true);     // shown while Partial is on (to-do for this tab)
+    expect(r.withoutPartial).toBe(false); // hidden once Partial is off
+});