fix(frontend): keep zonal EC2 AZ in purchase variant identity and cell key

frontend/src/__tests__/purchase-modal-submit.test.ts

@@ -492,6 +492,8 @@ describe('Issue #1903: purchase modal re-prices on Term/Payment change', () => {
   test.each<[string, string, string, Record<string, unknown>, unknown]>([
     ['ec2', 'platform', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' }, 'Windows'],
     ['ec2', 'tenancy', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' }, 'dedicated'],
+    ['ec2', 'availability_zone', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Availability Zone', availability_zone: 'us-east-1a' }, 'us-east-1b'],
+    ['compute', 'availability_zone', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Availability Zone', availability_zone: 'us-east-1a' }, 'us-east-1b'],
     ['ec2', 'scope', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' }, 'Availability Zone'],
     ['compute', 'platform', 'm5.large', { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' }, 'Windows'],
     ['rds', 'az_config', 'db.r5.large', { engine: 'postgres', az_config: 'single-az' }, 'multi-az'],
@@ -547,6 +549,18 @@ describe('Issue #1903: purchase modal re-prices on Term/Payment change', () => {
     ]);
   });
 
+  test('purchase identity keeps a regional EC2 rec (no AZ) matching its own variants', async () => {
+    const details = { instance_type: 'm5.large', platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' };
+    const original = { ...buildRows()[0]!, details };
+    const sibling = { ...original, id: 'regional-1-all', term: 1, upfront_cost: 12000 };
+    (state.getRecommendations as jest.Mock).mockReturnValue([sibling, original]);
+
+    await openPurchaseModal([original]);
+
+    expect(Array.from(document.querySelector<HTMLSelectElement>('.purchase-row-term')!.options, (option) => option.value).sort())
+      .toEqual(['1', '3']);
+  });
+
   test.each([undefined, null, [], 'invalid', { platform: 1 }, {}])('purchase identity does not match populated EC2 details to %j', async (otherDetails) => {
     const original = { ...buildRows()[0]!, details: { platform: 'Linux/UNIX', tenancy: 'default', scope: 'Region' } };
     const other = { ...original, id: 'missing-identity', term: 1, details: otherDetails };

frontend/src/__tests__/recommendations.test.ts

@@ -5155,6 +5155,17 @@ describe('Issues #225 + #226: cell grouping with savings range and collapse/expa
       const groups = groupRecsByCell([rec1, rec2]);
       expect(groups.size).toBe(2);
     });
+
+    test('zonal EC2 recs differing only by AZ are separate cells; regional recs are unchanged (issue #792)', () => {
+      const a = mkRec({ availability_zone: 'us-east-1a' });
+      const b = mkRec({ availability_zone: 'us-east-1b' });
+      const a2 = mkRec({ availability_zone: 'us-east-1a', term: 3 });
+      const regional1 = mkRec({});
+      const regional2 = mkRec({ term: 3 });
+      const groups = groupRecsByCell([a, b, a2, regional1, regional2]);
+      expect(groups.size).toBe(3);
+      expect(Array.from(groups.keys())).toContain('aws||ec2|us-east-1|m5.large|');
+    });
   });
 
   describe('cellSummary (pure helper)', () => {

frontend/src/api/types.ts

@@ -128,6 +128,8 @@ export interface Recommendation {
   region: string;
   resource_type: string;
   engine?: string;
+  // Zonal EC2 reservation AZ name; absent for regional recs (issue #792).
+  availability_zone?: string;
   // Opaque ServiceDetails payload from the backend (json.RawMessage).
   // The frontend treats this as a pass-through blob: it is stashed when
   // the GET /api/recommendations response is parsed and forwarded unchanged

frontend/src/recommendations.ts

@@ -988,7 +988,10 @@ const SORTABLE_STRING_COLUMNS: Record<string, (r: LocalRecommendation) => string
 // Used by issue #224's radio enforcement: at most one variant per cell
 // can be selected at any time.
 function cellKey(rec: LocalRecommendation): string {
-  return `${rec.provider}|${rec.cloud_account_id ?? ''}|${rec.service}|${rec.region}|${rec.resource_type}|${rec.engine ?? ''}`;
+  const key = `${rec.provider}|${rec.cloud_account_id ?? ''}|${rec.service}|${rec.region}|${rec.resource_type}|${rec.engine ?? ''}`;
+  // Zonal EC2 recs in different AZs are distinct purchasable cells (issue #792);
+  // the suffix is added only for them so every other cell key is unchanged.
+  return rec.availability_zone ? `${key}|${rec.availability_zone}` : key;
 }
 
 // issues #225 + #226: cell-grouping helpers.
@@ -1020,7 +1023,7 @@ function samePurchaseVariantIdentity(a: LocalRecommendation, b: LocalRecommendat
   switch (a.service) {
     case 'ec2':
     case 'compute':
-      fields = ['platform', 'tenancy', 'scope'];
+      fields = ['platform', 'tenancy', 'scope', 'availability_zone'];
       break;
     case 'rds':
     case 'relational-db':

frontend/src/types.ts

@@ -70,6 +70,8 @@ export interface LocalRecommendation {
   service: string;
   resource_type: string;
   engine?: string;
+  // Zonal EC2 reservation AZ name; absent for regional recs (issue #792).
+  availability_zone?: string;
   // Opaque ServiceDetails payload from the backend (json.RawMessage).
   // Stashed when the GET /api/recommendations response is parsed and
   // forwarded unchanged in the POST /api/purchases/execute body so the