diff --git a/dist/chromium/content.js b/dist/chromium/content.js
index c9f97ff..8de02dc 100644
--- a/dist/chromium/content.js
+++ b/dist/chromium/content.js
@@ -2601,6 +2601,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedCustomerFilter = true;
       saveFilterPreferences();
       renderCustomerFilter();
+      renderOwnerFilter();
       renderOpportunitiesTable();
     });
 
@@ -2661,6 +2662,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedOwnerFilter = true;
       saveFilterPreferences();
       renderOwnerFilter();
+      renderCustomerFilter();
       renderOpportunitiesTable();
     });
 
@@ -7053,21 +7055,35 @@ function createOpportunitiesFilters({
     }
   }
 
+  // Keep stored selections intact: narrowing a menu must not turn an implicit
+  // "all" into a second filter that prevents expanding the original selection.
+  function getAvailableCustomerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allOwners = getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key));
+    return getCustomerOptions(allOwners ? items : items.filter(item => opportunitiesFilterState.selectedOwnerKeys.has(getOwnerKey(item))));
+  }
+
+  function getAvailableOwnerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allCustomers = getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key));
+    return getOwnerOptions(allCustomers ? items : items.filter(item => opportunitiesFilterState.selectedCustomerKeys.has(getCustomerKey(item))));
+  }
+
   function renderCustomerFilter() {
     const trigger = document.getElementById(CUSTOMER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(CUSTOMER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(CUSTOMER_FILTER_SELECT_ALL_ID);
-    const customerOptions = getCustomerOptions();
+    const customerOptions = getAvailableCustomerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = customerOptions.filter((customer) => opportunitiesFilterState.selectedCustomerKeys.has(customer.key)).length;
-    trigger.disabled = customerOptions.length === 0;
+    trigger.disabled = getCustomerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(customerOptions.length, selectedCount);
     searchInput.value = opportunitiesFilterState.customerSearch;
-    selectAllCheckbox.disabled = customerOptions.length === 0;
+    selectAllCheckbox.disabled = getCustomerOptions().length === 0;
     selectAllCheckbox.checked = customerOptions.length > 0 && selectedCount === customerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < customerOptions.length;
     renderCustomerFilterList();
@@ -7081,7 +7097,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.customerSearch.trim().toLocaleLowerCase();
-    const customerOptions = getCustomerOptions().filter((customer) => {
+    const customerOptions = getAvailableCustomerOptions().filter((customer) => {
       return customer.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -7103,7 +7119,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedCustomerKeys.has(customer.key);
       checkbox.addEventListener("change", () => {
-        if (getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
+        if (getAvailableCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
           opportunitiesFilterState.selectedCustomerKeys.clear();
           opportunitiesFilterState.selectedCustomerKeys.add(customer.key);
         } else if (checkbox.checked) {
@@ -7115,6 +7131,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedCustomerFilter = true;
         saveFilterPreferences();
         renderCustomerFilter();
+        renderOwnerFilter();
         renderOpportunitiesTable();
       });
 
@@ -7129,18 +7146,18 @@ function createOpportunitiesFilters({
     const trigger = document.getElementById(OWNER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(OWNER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(OWNER_FILTER_SELECT_ALL_ID);
-    const ownerOptions = getOwnerOptions();
+    const ownerOptions = getAvailableOwnerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = ownerOptions.filter((owner) => opportunitiesFilterState.selectedOwnerKeys.has(owner.key)).length;
-    trigger.disabled = ownerOptions.length === 0;
+    trigger.disabled = getOwnerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(ownerOptions.length, selectedCount)
       .replace("customer", "owner");
     searchInput.value = opportunitiesFilterState.ownerSearch;
-    selectAllCheckbox.disabled = ownerOptions.length === 0;
+    selectAllCheckbox.disabled = getOwnerOptions().length === 0;
     selectAllCheckbox.checked = ownerOptions.length > 0 && selectedCount === ownerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < ownerOptions.length;
     renderOwnerFilterList();
@@ -7154,7 +7171,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.ownerSearch.trim().toLocaleLowerCase();
-    const ownerOptions = getOwnerOptions().filter((owner) => {
+    const ownerOptions = getAvailableOwnerOptions().filter((owner) => {
       return owner.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -7176,7 +7193,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedOwnerKeys.has(owner.key);
       checkbox.addEventListener("change", () => {
-        if (getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
+        if (getAvailableOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
           opportunitiesFilterState.selectedOwnerKeys.clear();
           opportunitiesFilterState.selectedOwnerKeys.add(owner.key);
         } else if (checkbox.checked) {
@@ -7188,6 +7205,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedOwnerFilter = true;
         saveFilterPreferences();
         renderOwnerFilter();
+        renderCustomerFilter();
         renderOpportunitiesTable();
       });
 
@@ -7269,7 +7287,7 @@ function createOpportunitiesFilters({
     return opportunitiesFilterState.selectedStatuses.has(statusCode);
   }
 
-  return { resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
+  return { getAvailableCustomerOptions, getAvailableOwnerOptions, resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
 }
 
 // Source: src/features/opportunities/formatters.js
diff --git a/dist/firefox/content.js b/dist/firefox/content.js
index c9f97ff..8de02dc 100644
--- a/dist/firefox/content.js
+++ b/dist/firefox/content.js
@@ -2601,6 +2601,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedCustomerFilter = true;
       saveFilterPreferences();
       renderCustomerFilter();
+      renderOwnerFilter();
       renderOpportunitiesTable();
     });
 
@@ -2661,6 +2662,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedOwnerFilter = true;
       saveFilterPreferences();
       renderOwnerFilter();
+      renderCustomerFilter();
       renderOpportunitiesTable();
     });
 
@@ -7053,21 +7055,35 @@ function createOpportunitiesFilters({
     }
   }
 
+  // Keep stored selections intact: narrowing a menu must not turn an implicit
+  // "all" into a second filter that prevents expanding the original selection.
+  function getAvailableCustomerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allOwners = getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key));
+    return getCustomerOptions(allOwners ? items : items.filter(item => opportunitiesFilterState.selectedOwnerKeys.has(getOwnerKey(item))));
+  }
+
+  function getAvailableOwnerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allCustomers = getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key));
+    return getOwnerOptions(allCustomers ? items : items.filter(item => opportunitiesFilterState.selectedCustomerKeys.has(getCustomerKey(item))));
+  }
+
   function renderCustomerFilter() {
     const trigger = document.getElementById(CUSTOMER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(CUSTOMER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(CUSTOMER_FILTER_SELECT_ALL_ID);
-    const customerOptions = getCustomerOptions();
+    const customerOptions = getAvailableCustomerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = customerOptions.filter((customer) => opportunitiesFilterState.selectedCustomerKeys.has(customer.key)).length;
-    trigger.disabled = customerOptions.length === 0;
+    trigger.disabled = getCustomerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(customerOptions.length, selectedCount);
     searchInput.value = opportunitiesFilterState.customerSearch;
-    selectAllCheckbox.disabled = customerOptions.length === 0;
+    selectAllCheckbox.disabled = getCustomerOptions().length === 0;
     selectAllCheckbox.checked = customerOptions.length > 0 && selectedCount === customerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < customerOptions.length;
     renderCustomerFilterList();
@@ -7081,7 +7097,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.customerSearch.trim().toLocaleLowerCase();
-    const customerOptions = getCustomerOptions().filter((customer) => {
+    const customerOptions = getAvailableCustomerOptions().filter((customer) => {
       return customer.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -7103,7 +7119,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedCustomerKeys.has(customer.key);
       checkbox.addEventListener("change", () => {
-        if (getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
+        if (getAvailableCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
           opportunitiesFilterState.selectedCustomerKeys.clear();
           opportunitiesFilterState.selectedCustomerKeys.add(customer.key);
         } else if (checkbox.checked) {
@@ -7115,6 +7131,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedCustomerFilter = true;
         saveFilterPreferences();
         renderCustomerFilter();
+        renderOwnerFilter();
         renderOpportunitiesTable();
       });
 
@@ -7129,18 +7146,18 @@ function createOpportunitiesFilters({
     const trigger = document.getElementById(OWNER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(OWNER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(OWNER_FILTER_SELECT_ALL_ID);
-    const ownerOptions = getOwnerOptions();
+    const ownerOptions = getAvailableOwnerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = ownerOptions.filter((owner) => opportunitiesFilterState.selectedOwnerKeys.has(owner.key)).length;
-    trigger.disabled = ownerOptions.length === 0;
+    trigger.disabled = getOwnerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(ownerOptions.length, selectedCount)
       .replace("customer", "owner");
     searchInput.value = opportunitiesFilterState.ownerSearch;
-    selectAllCheckbox.disabled = ownerOptions.length === 0;
+    selectAllCheckbox.disabled = getOwnerOptions().length === 0;
     selectAllCheckbox.checked = ownerOptions.length > 0 && selectedCount === ownerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < ownerOptions.length;
     renderOwnerFilterList();
@@ -7154,7 +7171,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.ownerSearch.trim().toLocaleLowerCase();
-    const ownerOptions = getOwnerOptions().filter((owner) => {
+    const ownerOptions = getAvailableOwnerOptions().filter((owner) => {
       return owner.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -7176,7 +7193,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedOwnerKeys.has(owner.key);
       checkbox.addEventListener("change", () => {
-        if (getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
+        if (getAvailableOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
           opportunitiesFilterState.selectedOwnerKeys.clear();
           opportunitiesFilterState.selectedOwnerKeys.add(owner.key);
         } else if (checkbox.checked) {
@@ -7188,6 +7205,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedOwnerFilter = true;
         saveFilterPreferences();
         renderOwnerFilter();
+        renderCustomerFilter();
         renderOpportunitiesTable();
       });
 
@@ -7269,7 +7287,7 @@ function createOpportunitiesFilters({
     return opportunitiesFilterState.selectedStatuses.has(statusCode);
   }
 
-  return { resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
+  return { getAvailableCustomerOptions, getAvailableOwnerOptions, resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
 }
 
 // Source: src/features/opportunities/formatters.js
diff --git a/src/content/modal.js b/src/content/modal.js
index d8b9120..0772e0b 100644
--- a/src/content/modal.js
+++ b/src/content/modal.js
@@ -310,6 +310,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedCustomerFilter = true;
       saveFilterPreferences();
       renderCustomerFilter();
+      renderOwnerFilter();
       renderOpportunitiesTable();
     });
 
@@ -370,6 +371,7 @@ function createContentModal({
       opportunitiesFilterState.hasSavedOwnerFilter = true;
       saveFilterPreferences();
       renderOwnerFilter();
+      renderCustomerFilter();
       renderOpportunitiesTable();
     });
 
diff --git a/src/features/opportunities/filters.js b/src/features/opportunities/filters.js
index c53c225..05c90fd 100644
--- a/src/features/opportunities/filters.js
+++ b/src/features/opportunities/filters.js
@@ -202,21 +202,35 @@ function createOpportunitiesFilters({
     }
   }
 
+  // Keep stored selections intact: narrowing a menu must not turn an implicit
+  // "all" into a second filter that prevents expanding the original selection.
+  function getAvailableCustomerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allOwners = getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key));
+    return getCustomerOptions(allOwners ? items : items.filter(item => opportunitiesFilterState.selectedOwnerKeys.has(getOwnerKey(item))));
+  }
+
+  function getAvailableOwnerOptions() {
+    const items = opportunitiesTableState.opportunitiesTableState.items;
+    const allCustomers = getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key));
+    return getOwnerOptions(allCustomers ? items : items.filter(item => opportunitiesFilterState.selectedCustomerKeys.has(getCustomerKey(item))));
+  }
+
   function renderCustomerFilter() {
     const trigger = document.getElementById(CUSTOMER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(CUSTOMER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(CUSTOMER_FILTER_SELECT_ALL_ID);
-    const customerOptions = getCustomerOptions();
+    const customerOptions = getAvailableCustomerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = customerOptions.filter((customer) => opportunitiesFilterState.selectedCustomerKeys.has(customer.key)).length;
-    trigger.disabled = customerOptions.length === 0;
+    trigger.disabled = getCustomerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(customerOptions.length, selectedCount);
     searchInput.value = opportunitiesFilterState.customerSearch;
-    selectAllCheckbox.disabled = customerOptions.length === 0;
+    selectAllCheckbox.disabled = getCustomerOptions().length === 0;
     selectAllCheckbox.checked = customerOptions.length > 0 && selectedCount === customerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < customerOptions.length;
     renderCustomerFilterList();
@@ -230,7 +244,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.customerSearch.trim().toLocaleLowerCase();
-    const customerOptions = getCustomerOptions().filter((customer) => {
+    const customerOptions = getAvailableCustomerOptions().filter((customer) => {
       return customer.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -252,7 +266,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedCustomerKeys.has(customer.key);
       checkbox.addEventListener("change", () => {
-        if (getCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
+        if (getAvailableCustomerOptions().every(option => opportunitiesFilterState.selectedCustomerKeys.has(option.key))) {
           opportunitiesFilterState.selectedCustomerKeys.clear();
           opportunitiesFilterState.selectedCustomerKeys.add(customer.key);
         } else if (checkbox.checked) {
@@ -264,6 +278,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedCustomerFilter = true;
         saveFilterPreferences();
         renderCustomerFilter();
+        renderOwnerFilter();
         renderOpportunitiesTable();
       });
 
@@ -278,18 +293,18 @@ function createOpportunitiesFilters({
     const trigger = document.getElementById(OWNER_FILTER_BUTTON_ID);
     const searchInput = document.getElementById(OWNER_FILTER_SEARCH_ID);
     const selectAllCheckbox = document.getElementById(OWNER_FILTER_SELECT_ALL_ID);
-    const ownerOptions = getOwnerOptions();
+    const ownerOptions = getAvailableOwnerOptions();
 
     if (!trigger || !searchInput || !selectAllCheckbox) {
       return;
     }
 
     const selectedCount = ownerOptions.filter((owner) => opportunitiesFilterState.selectedOwnerKeys.has(owner.key)).length;
-    trigger.disabled = ownerOptions.length === 0;
+    trigger.disabled = getOwnerOptions().length === 0;
     trigger.textContent = getCustomerFilterSummary(ownerOptions.length, selectedCount)
       .replace("customer", "owner");
     searchInput.value = opportunitiesFilterState.ownerSearch;
-    selectAllCheckbox.disabled = ownerOptions.length === 0;
+    selectAllCheckbox.disabled = getOwnerOptions().length === 0;
     selectAllCheckbox.checked = ownerOptions.length > 0 && selectedCount === ownerOptions.length;
     selectAllCheckbox.indeterminate = selectedCount > 0 && selectedCount < ownerOptions.length;
     renderOwnerFilterList();
@@ -303,7 +318,7 @@ function createOpportunitiesFilters({
     }
 
     const normalizedSearch = opportunitiesFilterState.ownerSearch.trim().toLocaleLowerCase();
-    const ownerOptions = getOwnerOptions().filter((owner) => {
+    const ownerOptions = getAvailableOwnerOptions().filter((owner) => {
       return owner.label.toLocaleLowerCase().includes(normalizedSearch);
     });
 
@@ -325,7 +340,7 @@ function createOpportunitiesFilters({
       checkbox.type = "checkbox";
       checkbox.checked = opportunitiesFilterState.selectedOwnerKeys.has(owner.key);
       checkbox.addEventListener("change", () => {
-        if (getOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
+        if (getAvailableOwnerOptions().every(option => opportunitiesFilterState.selectedOwnerKeys.has(option.key))) {
           opportunitiesFilterState.selectedOwnerKeys.clear();
           opportunitiesFilterState.selectedOwnerKeys.add(owner.key);
         } else if (checkbox.checked) {
@@ -337,6 +352,7 @@ function createOpportunitiesFilters({
         opportunitiesFilterState.hasSavedOwnerFilter = true;
         saveFilterPreferences();
         renderOwnerFilter();
+        renderCustomerFilter();
         renderOpportunitiesTable();
       });
 
@@ -418,5 +434,5 @@ function createOpportunitiesFilters({
     return opportunitiesFilterState.selectedStatuses.has(statusCode);
   }
 
-  return { resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
+  return { getAvailableCustomerOptions, getAvailableOwnerOptions, resetCustomerAndOwnerFiltersForPeriod, renderStageFilterButtons, toggleStageFilter, renderStatusFilterButtons, toggleStatusFilter, toggleCustomerFilterPanel, closeCustomerFilterPanel, toggleOwnerFilterPanel, closeOwnerFilterPanel, resetCustomerFilter, resetOwnerFilter, renderCustomerFilter, renderCustomerFilterList, renderOwnerFilter, renderOwnerFilterList, getSortedOpportunities, matchesTableSearch, matchesSelectedStatus };
 }
diff --git a/tests/dependentFilters.test.cjs b/tests/dependentFilters.test.cjs
new file mode 100644
index 0000000..6ed7dab
--- /dev/null
+++ b/tests/dependentFilters.test.cjs
@@ -0,0 +1,43 @@
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const { loadApplication } = require('./support/application.cjs');
+function setup() {
+  const app = loadApplication('content');
+  const items = [['A', 'X'], ['A', 'Y'], ['B', 'Y'], ['C', 'Z'], ['A', 'X']].map(([customer, owner]) => ({
+    CustomerAccount: { PartyId: customer, PartyUniqueName: customer }, Owner: owner
+  }));
+  app.opportunitiesTableState.opportunitiesTableState.items = items;
+  app.opportunitiesFilters.resetCustomerFilter(items);
+  app.opportunitiesFilters.resetOwnerFilter(items);
+  return { filters: app.opportunitiesFilters, state: app.opportunitiesFilterState };
+}
+const labels = options => Array.from(options, option => option.label);
+test('customers narrow owners without losing all-owner selection; widening restores options', () => {
+  const { filters, state } = setup();
+  state.selectedCustomerKeys = new Set(['party:A']);
+  assert.deepEqual(labels(filters.getAvailableOwnerOptions()), ['X', 'Y']);
+  assert.deepEqual(labels(filters.getAvailableCustomerOptions()), ['A', 'B', 'C']);
+  state.selectedCustomerKeys.add('party:C');
+  assert.deepEqual(labels(filters.getAvailableOwnerOptions()), ['X', 'Y', 'Z']);
+  assert.equal(state.selectedOwnerKeys.size, 3);
+});
+test('owners narrow customers and multi-selection combines their customers', () => {
+  const { filters, state } = setup();
+  state.selectedOwnerKeys = new Set(['name:Y']);
+  assert.deepEqual(labels(filters.getAvailableCustomerOptions()), ['A', 'B']);
+  assert.deepEqual(labels(filters.getAvailableOwnerOptions()), ['X', 'Y', 'Z']);
+  state.selectedOwnerKeys.add('name:Z');
+  assert.deepEqual(labels(filters.getAvailableCustomerOptions()), ['A', 'B', 'C']);
+});
+test('both filters use the opposite selection, independent of search and stage', () => {
+  const { filters, state } = setup();
+  state.selectedOwnerKeys = new Set(['name:Y']);
+  state.selectedCustomerKeys = new Set(['party:A']);
+  state.tableSearch = 'no match';
+  state.selectedStages.clear();
+  assert.deepEqual(labels(filters.getAvailableCustomerOptions()), ['A', 'B']);
+  assert.deepEqual(labels(filters.getAvailableOwnerOptions()), ['X', 'Y']);
+  state.selectedCustomerKeys.clear();
+  assert.deepEqual(labels(filters.getAvailableOwnerOptions()), []);
+  assert.deepEqual(labels(filters.getAvailableCustomerOptions()), ['A', 'B']);
+});