@@ -0,0 +1,6 @@
+---
+'@hyperdx/app': patch
+'@hyperdx/common-utils': patch
+---
+
+feat: Support dependent variable value queries
@@ -3178,6 +3178,7 @@ function DBDashboardPage({ presetConfig }: { presetConfig?: Dashboard }) {
           filterValues={filterValues}
           onSetFilterValue={setFilterValue}
           dateRange={searchedTimeRange}
+          variables={showFilterVariableOptions ? variables : undefined}
         />
       )}
       {/* Selection indicator */}
@@ -3354,6 +3355,7 @@ function DBDashboardPage({ presetConfig }: { presetConfig?: Dashboard }) {
           onRemoveFilter={handleRemoveFilter}
           isLoading={isSavingDashboard || isFetchingDashboard}
           showVariableOptions={showFilterVariableOptions}
+          variables={showFilterVariableOptions ? variables : undefined}
         />
       )}
     </>
 
@@ -2,10 +2,14 @@ import { useMemo, useState } from 'react';
 import {
   FilterState,
   getFilterVariableName,
+  getPendingFilterValuesVariables,
   isFilterBroadcastEnabled,
   isFilterVariableEnabled,
 } from '@hyperdx/common-utils/dist/filters';
-import { DashboardFilter } from '@hyperdx/common-utils/dist/types';
+import {
+  ChartVariable,
+  DashboardFilter,
+} from '@hyperdx/common-utils/dist/types';
 import { Group, Stack, Text, Tooltip } from '@mantine/core';
 import { IconAlertTriangle, IconHelp, IconRefresh } from '@tabler/icons-react';
 
@@ -20,8 +24,29 @@ interface DashboardFilterSelectProps {
   values?: string[];
   isLoading?: boolean;
   isError?: boolean;
+  /** Shown instead of the generic message when the query's failure is known. */
+  errorMessage?: string;
+  /**
+   * Variables this filter's dropdown query needs a selection for before it can
+   * match any rows.
+   */
+  pendingVariables?: string[];
 }
 
+/**
+ * Explain a dropdown query that may list nothing until one of the variables it
+ * depends on is selected. Only the bare SQL reference form gets here — the
+ * macros and Lucene both have an empty state that lists every value.
+ */
+export const getPendingVariablesTooltip = (
+  pendingVariables: string[],
+): string => {
+  const names = pendingVariables.map(name => `$${name}`).join(', ');
+  return `Filter depends on ${names}, which ${
+    pendingVariables.length === 1 ? 'has' : 'have'
+  } no selected value.`;
+};
+
 /**
  * Describe what a filter does with the value you pick: broadcast it as a
  * condition, expose it as a variable, both, or neither.
@@ -66,6 +91,8 @@ const DashboardFilterSelect = ({
   values,
   isLoading,
   isError,
+  errorMessage,
+  pendingVariables,
 }: DashboardFilterSelectProps) => {
   const valuesOrEmptyMemo = useMemo(() => values ?? [], [values]);
   const effect = getFilterEffect(filter);
@@ -91,10 +118,29 @@ const DashboardFilterSelect = ({
             />
           )}
         </Tooltip>
+        {!!pendingVariables?.length && (
+          <Tooltip
+            label={getPendingVariablesTooltip(pendingVariables)}
+            withinPortal
+            multiline
+            maw={400}
+          >
+            <IconAlertTriangle
+              size={12}
+              color="var(--color-text-warning)"
+              data-testid={`dashboard-filter-pending-variable-${filter.name}`}
+            />
+          </Tooltip>
+        )}
         {isError && (
           <Tooltip
-            label="Filter values query failed. The filter's query may be invalid."
+            label={
+              errorMessage ??
+              "Filter values query failed. The filter's query may be invalid."
+            }
             withinPortal
+            multiline
+            maw={400}
           >
             <IconAlertTriangle
               size={12}
@@ -126,13 +172,20 @@ interface DashboardFilterProps {
   filterValues: FilterState;
   onSetFilterValue: (expression: string, values: string[]) => void;
   dateRange: [Date, Date];
+  /**
+   * The dashboard's variables and their current selections. Defined only when
+   * filters on this dashboard can be exposed as variables at all, so it doubles
+   * as the gate for variable-specific copy.
+   */
+  variables?: ChartVariable[];
 }
 
 const DashboardFilters = ({
   filters,
   dateRange,
   filterValues,
   onSetFilterValue,
+  variables,
 }: DashboardFilterProps) => {
   // "Link" mode (opt-in, off by default): each dropdown's values are narrowed by
   // the others' selections. Off by default because contingent value lookups
@@ -143,10 +196,12 @@ const DashboardFilters = ({
   const {
     data: filterValuesById,
     erroredFilterIds,
+    filterErrorMessages,
     isFetching,
   } = useDashboardFilterValues({
     filters,
     dateRange,
+    variables,
     // Only narrow by sibling selections when linked.
     filterValues: linked ? filterValues : {},
   });
@@ -171,6 +226,11 @@ const DashboardFilters = ({
             filter={filter}
             isLoading={isLoadingValues}
             isError={erroredFilterIds?.has(filter.id) ?? false}
+            errorMessage={filterErrorMessages?.get(filter.id)}
+            pendingVariables={getPendingFilterValuesVariables(
+              filter,
+              variables,
+            )}
             onChange={values => onSetFilterValue(filter.expression, values)}
             values={queriedFilterValues?.values}
             value={selectedValues}
@@ -186,6 +246,7 @@ const DashboardFilters = ({
           <FilterLinkToggle
             linked={linked}
             onChange={setLinked}
+            showVariableNote={variables !== undefined}
             data-testid="dashboard-filters-link-toggle"
           />
         </Stack>
 
@@ -10,12 +10,14 @@ import {
   validateVariableName,
 } from '@hyperdx/common-utils/dist/filters';
 import {
+  ChartVariable,
   DashboardFilter,
   MetricsDataType,
   SourceKind,
   TSource,
 } from '@hyperdx/common-utils/dist/types';
 import {
+  Alert,
   Box,
   Button,
   Center,
@@ -33,6 +35,7 @@ import {
   UnstyledButton,
 } from '@mantine/core';
 import {
+  IconAlertTriangle,
   IconFilter,
   IconInfoCircle,
   IconPencil,
@@ -46,6 +49,7 @@ import SearchWhereInput, {
   getStoredLanguage,
 } from '@/components/SearchInput/SearchWhereInput';
 import { SQLInlineEditorControlled } from '@/components/SQLEditor/SQLInlineEditor';
+import { SqlVariablesProvider } from '@/components/SQLEditor/variableCompletions';
 
 import { SourceMultiSelectControlled } from './components/SourceMultiSelect';
 import SourceSchemaPreview, {
@@ -158,11 +162,30 @@ const DashboardFilterEditForm = ({
     [filters, filter.id],
   );
 
-  const [formFilterName, formIsBroadCastEnabled, formIsVariableEnabled] =
-    useWatch({
-      control,
-      name: ['name', 'isBroadcastEnabled', 'isVariableEnabled'],
-    });
+  const [
+    formFilterName,
+    formIsBroadCastEnabled,
+    formIsVariableEnabled,
+    formAppliesToSourceIds,
+  ] = useWatch({
+    control,
+    name: [
+      'name',
+      'isBroadcastEnabled',
+      'isVariableEnabled',
+      'appliesToSourceIds',
+    ],
+  });
+
+  // Both modes on with an unrestricted broadcast is almost always a mistake:
+  // broadcast already reaches every tile, so the variable adds nothing and the
+  // tiles that reference it get filtered twice over. Scoping the broadcast is
+  // what makes the pair meaningful, so nudge toward "Applies to sources".
+  const showUnscopedBroadcastWarning =
+    showVariableOptions &&
+    formIsBroadCastEnabled !== false &&
+    formIsVariableEnabled === true &&
+    !formAppliesToSourceIds?.some(id => !!id?.length);
 
   const derivedVariableName = deriveVariableName(formFilterName ?? '');
 
@@ -359,7 +382,7 @@ const DashboardFilterEditForm = ({
 
             <CustomInputWrapper
               label="Dropdown values filter"
-              tooltipText="Optional condition used to filter the rows from which available filter values are queried"
+              tooltipText="Optional condition used to filter the rows from which available filter values are queried. May reference the dashboard's other variables."
             >
               <SearchWhereInput
                 tableConnection={tableConnection}
@@ -371,6 +394,7 @@ const DashboardFilterEditForm = ({
                 allowMultiline={true}
                 sqlPlaceholder="Filter for dropdown values"
                 lucenePlaceholder="Filter for dropdown values"
+                enableVariables={showVariableOptions}
               />
             </CustomInputWrapper>
 
@@ -382,7 +406,7 @@ const DashboardFilterEditForm = ({
                   name="isBroadcastEnabled"
                   size="xs"
                   label="Broadcast filter condition"
-                  description="Apply the selected value as a filter condition on each tile."
+                  description="Automatically apply the selected value to every query builder tile, and to every Raw SQL tile that uses the $__filters macro. Optionally, narrow to tiles that use specific sources."
                   data-testid="filter-broadcast-checkbox"
                 />
               </>
@@ -396,7 +420,7 @@ const DashboardFilterEditForm = ({
                 <Box ml={showVariableOptions ? 'xl' : undefined}>
                   <CustomInputWrapper
                     label="Applies to sources"
-                    tooltipText="Leave empty to apply to all tiles. Selecting one or more sources restricts the filter to only tiles using those sources."
+                    tooltipText="Which tiles the broadcast reaches. Leave empty to broadcast to all tiles. Selecting one or more sources restricts the broadcast to tiles using those sources."
                   >
                     <SourceMultiSelectControlled
                       control={control}
@@ -422,7 +446,7 @@ const DashboardFilterEditForm = ({
                   name="isVariableEnabled"
                   size="xs"
                   label="Available as variable"
-                  description="Expose the selected value a $variable."
+                  description="Expose the selected value as a $variable. Selections only affect tiles that reference the variable explicitly, typically via the $__filter or $__conditionalAll macros."
                   data-testid="filter-variable-enabled-checkbox"
                   rules={{ validate: validateFilterModes }}
                 />
@@ -444,6 +468,19 @@ const DashboardFilterEditForm = ({
                     </CustomInputWrapper>
                   </Box>
                 )}
+                {showUnscopedBroadcastWarning && (
+                  <Alert
+                    variant="warning"
+                    icon={<IconAlertTriangle size={16} />}
+                    data-testid="filter-unscoped-broadcast-warning"
+                  >
+                    Broadcast already applies this filter to every tile,
+                    including the ones that reference the variable. Set “Applies
+                    to sources” to limit which tiles the broadcast reaches, or
+                    turn off broadcast so only tiles that reference the variable
+                    are filtered.
+                  </Alert>
+                )}
               </>
             )}
 
@@ -652,6 +689,8 @@ interface DashboardFiltersEditModalProps {
   source?: TSource;
   /** Whether to offer the broadcast / variable controls. */
   showVariableOptions: boolean;
+  /** The dashboard's variables, if any */
+  variables?: ChartVariable[];
   onClose: () => void;
   onSaveFilter: (filter: DashboardFilter) => void;
   onRemoveFilter: (id: string) => void;
@@ -665,6 +704,7 @@ const DashboardFiltersModal = ({
   isLoading,
   source,
   showVariableOptions,
+  variables,
   onClose,
   onSaveFilter,
   onRemoveFilter,
@@ -694,10 +734,7 @@ const DashboardFiltersModal = ({
       where: '',
       whereLanguage: getStoredLanguage() ?? 'sql',
       isBroadcastEnabled: true,
-      // New filters are variable-enabled wherever the controls are available, so
-      // the checkbox is controlled from the first render. Callers that hide the
-      // controls get false, since their UI offers no way to turn it back off.
-      isVariableEnabled: showVariableOptions,
+      isVariableEnabled: false,
     });
   };
 
@@ -719,16 +756,18 @@ const DashboardFiltersModal = ({
     return <EmptyState onCreateFilter={handleAddNewFilter} onClose={onClose} />;
   } else if (selectedFilter) {
     return (
-      <DashboardFilterEditForm
-        filter={selectedFilter}
-        onSave={handleSaveFilter}
-        onCancel={() => setSelectedFilter(undefined)}
-        onClose={onClose}
-        isNew={selectedFilter.id === NEW_FILTER_ID}
-        source={source}
-        filters={filters}
-        showVariableOptions={showVariableOptions}
-      />
+      <SqlVariablesProvider variables={variables}>
+        <DashboardFilterEditForm
+          filter={selectedFilter}
+          onSave={handleSaveFilter}
+          onCancel={() => setSelectedFilter(undefined)}
+          onClose={onClose}
+          isNew={selectedFilter.id === NEW_FILTER_ID}
+          source={source}
+          filters={filters}
+          showVariableOptions={showVariableOptions}
+        />
+      </SqlVariablesProvider>
     );
   } else {
     return (
 
@@ -1,16 +1,19 @@
 import { DashboardFilter } from '@hyperdx/common-utils/dist/types';
 
-import { getFilterEffect } from '@/DashboardFilters';
+import {
+  getFilterEffect,
+  getPendingVariablesTooltip,
+} from '@/DashboardFilters';
 
-describe('getFilterEffect', () => {
-  const baseFilter: DashboardFilter = {
-    id: 'filter1',
-    type: 'QUERY_EXPRESSION',
-    name: 'Service Name',
-    expression: 'ServiceName',
-    source: 'logs',
-  };
+const baseFilter: DashboardFilter = {
+  id: 'filter1',
+  type: 'QUERY_EXPRESSION',
+  name: 'Service Name',
+  expression: 'ServiceName',
+  source: 'logs',
+};
 
+describe('getFilterEffect', () => {
   it('describes both effects when broadcast and variable are on', () => {
     expect(
       getFilterEffect({
@@ -97,3 +100,17 @@ describe('getFilterEffect', () => {
     ).toEqual('Available as variable ($svc)');
   });
 });
+
+describe('getPendingVariablesTooltip', () => {
+  it('names the variable that has no selected value', () => {
+    expect(getPendingVariablesTooltip(['svc'])).toBe(
+      'Filter depends on $svc, which has no selected value.',
+    );
+  });
+
+  it('agrees with more than one pending variable', () => {
+    expect(getPendingVariablesTooltip(['svc', 'env'])).toContain(
+      '$svc, $env, which have no selected value',
+    );
+  });
+});