diff --git a/backend/schema-snapshots/get-_health.json b/backend/schema-snapshots/get-_health.json
index 31d8f6b4..c62ee234 100644
--- a/backend/schema-snapshots/get-_health.json
+++ b/backend/schema-snapshots/get-_health.json
@@ -81,6 +81,15 @@
             "degraded",
             "unknown"
           ]
+        },
+        "indexer": {
+          "type": "string",
+          "enum": [
+            "up",
+            "down",
+            "degraded",
+            "unknown"
+          ]
         }
       },
       "required": [
@@ -90,7 +99,8 @@
         "databasePrimary",
         "databaseReplica",
         "prisma",
-        "jobs"
+        "jobs",
+        "indexer"
       ],
       "additionalProperties": false
     },
@@ -125,4 +135,4 @@
     "sorobanCircuitBreaker"
   ],
   "additionalProperties": false
-}
+}
\ No newline at end of file
diff --git a/backend/schema-snapshots/get-_ready.json b/backend/schema-snapshots/get-_ready.json
index 6e39ca57..ce8460ef 100644
--- a/backend/schema-snapshots/get-_ready.json
+++ b/backend/schema-snapshots/get-_ready.json
@@ -21,13 +21,17 @@
         },
         "prisma": {
           "type": "boolean"
+        },
+        "indexer": {
+          "type": "boolean"
         }
       },
       "required": [
         "cache",
         "stellarRpc",
         "database",
-        "prisma"
+        "prisma",
+        "indexer"
       ],
       "additionalProperties": false
     }
@@ -38,4 +42,4 @@
     "dependencies"
   ],
   "additionalProperties": false
-}
+}
\ No newline at end of file
diff --git a/backend/src/__tests__/issues711.test.ts b/backend/src/__tests__/issues711.test.ts
index 6bdaa11d..05259d46 100644
--- a/backend/src/__tests__/issues711.test.ts
+++ b/backend/src/__tests__/issues711.test.ts
@@ -46,6 +46,24 @@ describe('#711 API contract schema snapshots', () => {
     expect(issues.some((issue) => issue.message === 'field removed')).toBe(true);
   });
 
+  it('detects newly added required fields as breaking changes', () => {
+    const baseline = zodToJsonShape(HealthResponseSchema);
+    const current = JSON.parse(JSON.stringify(baseline)) as typeof baseline;
+    // Simulate an older snapshot that is missing the 'indexer' field
+    delete current.properties?.checks?.properties?.indexer;
+    current.properties!.checks!.required = (current.properties!.checks!.required ?? []).filter(
+      (k: string) => k !== 'indexer',
+    );
+
+    const issues = diffSchemaShapes(baseline, current, 'GET /health');
+    expect(
+      issues.some(
+        (issue) =>
+          issue.message.includes('new field added') || issue.message.includes('now required'),
+      ),
+    ).toBe(true);
+  });
+
   it('validates a conforming health payload', () => {
     const result = validateResponseAgainstSchema('GET /health', {
       status: 'healthy',
@@ -61,6 +79,7 @@ describe('#711 API contract schema snapshots', () => {
         databaseReplica: 'up',
         prisma: 'up',
         jobs: 'up',
+        indexer: 'up',
       },
       sorobanCircuitBreaker: {
         state: 'closed',
diff --git a/backend/src/__tests__/openApiContractTests.test.ts b/backend/src/__tests__/openApiContractTests.test.ts
index a280e737..ddc89dc2 100644
--- a/backend/src/__tests__/openApiContractTests.test.ts
+++ b/backend/src/__tests__/openApiContractTests.test.ts
@@ -76,7 +76,7 @@ describe('OpenAPI contract: GET /health', () => {
 
   it('checks object contains all required dependency keys', async () => {
     const res = await request(app).get('/health');
-    const requiredKeys = ['api', 'cache', 'stellarRpc', 'databasePrimary', 'databaseReplica', 'prisma', 'jobs'];
+    const requiredKeys = ['api', 'cache', 'stellarRpc', 'databasePrimary', 'databaseReplica', 'prisma', 'jobs', 'indexer'];
     for (const key of requiredKeys) {
       expect(res.body.checks).toHaveProperty(key);
       expect(['up', 'down', 'degraded', 'unknown']).toContain(res.body.checks[key]);
@@ -120,7 +120,7 @@ describe('OpenAPI contract: GET /ready', () => {
   it('dependencies object has boolean values for each key', async () => {
     const res = await request(app).get('/ready');
     const deps = res.body.dependencies as Record<string, unknown>;
-    const expectedKeys = ['cache', 'stellarRpc', 'database', 'prisma'];
+    const expectedKeys = ['cache', 'stellarRpc', 'database', 'prisma', 'indexer'];
     for (const key of expectedKeys) {
       expect(deps).toHaveProperty(key);
       expect(typeof deps[key]).toBe('boolean');
diff --git a/backend/src/apiContractSnapshots.ts b/backend/src/apiContractSnapshots.ts
index bfedf90a..4c35e634 100644
--- a/backend/src/apiContractSnapshots.ts
+++ b/backend/src/apiContractSnapshots.ts
@@ -240,11 +240,24 @@ export function diffSchemaShapes(
       issues.push(...diffSchemaShapes(baselineProps[key], currentProps[key], childPath));
     }
 
+    for (const key of Object.keys(currentProps)) {
+      if (!(key in baselineProps)) {
+        issues.push({ path: at(key), message: 'new field added — regenerate snapshots with npm run snapshots:write' });
+        continue;
+      }
+    }
+
     for (const key of baselineRequired) {
       if (!currentRequired.has(key)) {
         issues.push({ path: at(key), message: 'field is no longer required (may be breaking for strict clients)' });
       }
     }
+
+    for (const key of currentRequired) {
+      if (!baselineRequired.has(key)) {
+        issues.push({ path: at(key), message: 'field is now required — regenerate snapshots with npm run snapshots:write' });
+      }
+    }
   }
 
   if (baseline.type === 'array' && current.type === 'array') {
diff --git a/backend/src/index.ts b/backend/src/index.ts
index b6361df6..9625f0c5 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -2045,9 +2045,6 @@ app.post('/admin/emails/replay/:id', validateApiKey, async (req: Request, res: R
  */
 app.post('/admin/allowlist/add', validateApiKey, validate({ body: AllowlistWalletBodySchema }), async (req: Request, res: Response) => {
   const { walletAddress } = req.body;
-  if (!walletAddress || typeof walletAddress !== 'string') {
-    throw new ValidationError('Missing or invalid walletAddress in request body');
-  }
   const added = addAddress(walletAddress);
   const actor = resolveActingAdminAddress(req);
 
@@ -2084,12 +2081,14 @@ app.post('/admin/allowlist/add', validateApiKey, validate({ body: AllowlistWalle
  */
 app.delete('/admin/allowlist/remove', validateApiKey, validate({ body: AllowlistWalletBodySchema }), async (req: Request, res: Response) => {
   const { walletAddress } = req.body;
-  if (!walletAddress || typeof walletAddress !== 'string') {
-    throw new ValidationError('Missing or invalid walletAddress in request body');
-  }
   const removed = removeAddress(walletAddress);
   if (!removed) {
-    throw new NotFoundError('Wallet address not found in allowlist');
+    res.status(404).json({
+      error: 'Not Found',
+      status: 404,
+      message: 'Wallet address not found in allowlist',
+    });
+    return;
   }
 
   const actor = resolveActingAdminAddress(req);
@@ -2405,12 +2404,22 @@ app.get('/admin/impersonate/:wallet', validateApiKey, async (req: Request, res:
 
   if (!wallet) {
     req.adminAuditAction = 'admin.impersonate.invalid';
-    throw new ValidationError('wallet path parameter is required');
+    res.status(400).json({
+      error: 'Bad Request',
+      status: 400,
+      message: 'wallet path parameter is required',
+    });
+    return;
   }
 
   if (!hasRequiredApiKeyRole(req, 'super-admin')) {
     req.adminAuditAction = 'admin.impersonate.denied';
-    throw new ForbiddenError('Super-admin role is required for impersonation');
+    res.status(403).json({
+      error: 'Forbidden',
+      status: 403,
+      message: 'Super-admin role is required for impersonation',
+    });
+    return;
   }
 
   if (!sessionId && process.env.IMPERSONATION_SESSION_STORAGE) {
@@ -2477,13 +2486,17 @@ app.get('/admin/impersonate/:wallet', validateApiKey, async (req: Request, res:
           }
         : undefined,
     });
-    } catch (error) {
-      req.adminAuditAction = 'admin.impersonate.failed';
-      req.adminAuditMetadata = {
-        ...req.adminAuditMetadata,
-        error: error instanceof Error ? error.message : String(error),
-      };
-      throw new InternalError('Failed to build impersonated vault state');
+  } catch (error) {
+    req.adminAuditAction = 'admin.impersonate.failed';
+    req.adminAuditMetadata = {
+      ...req.adminAuditMetadata,
+      error: error instanceof Error ? error.message : String(error),
+    };
+    res.status(500).json({
+      error: 'Internal Server Error',
+      status: 500,
+      message: 'Failed to build impersonated vault state',
+    });
   }
 });
 
@@ -2571,12 +2584,22 @@ app.get('/admin/receipts/:id/verify', validateApiKey, async (req: Request, res:
 app.post('/admin/api-keys/register', validateApiKey, validate({ body: ApiKeyRegisterSchema }), async (req: Request, res: Response) => {
   const { key, role: requestedRole } = req.body;
   if (!key || typeof key !== 'string' || !key.trim()) {
-    throw new ValidationError('Missing key in request body');
+    res.status(400).json({
+      error: 'Bad Request',
+      status: 400,
+      message: 'Missing key in request body',
+    });
+    return;
   }
 
   const role = normalizeApiKeyRole(requestedRole) || 'admin';
   if (role === 'super-admin' && !hasRequiredApiKeyRole(req, 'super-admin')) {
-    throw new ForbiddenError('Super-admin role is required to register super-admin API keys');
+    res.status(403).json({
+      error: 'Forbidden',
+      status: 403,
+      message: 'Super-admin role is required to register super-admin API keys',
+    });
+    return;
   }
 
   const normalizedKey = key.trim();
@@ -2865,7 +2888,12 @@ app.patch('/admin/webhooks/:id', validateApiKey, validate({ params: IdParamSchem
 
   const endpoint = updateWebhookEndpoint(req.params.id, req.body || {});
   if (!endpoint) {
-    throw new NotFoundError('Webhook endpoint not found');
+    res.status(404).json({
+      error: 'Not Found',
+      status: 404,
+      message: 'Webhook endpoint not found',
+    });
+    return;
   }
 
   res.status(200).json({
diff --git a/backend/src/swagger.ts b/backend/src/swagger.ts
index 754327bd..a8bd1466 100644
--- a/backend/src/swagger.ts
+++ b/backend/src/swagger.ts
@@ -165,7 +165,9 @@ const options: swaggerJsdoc.Options = {
                     timestamp: '2024-01-01T00:00:00.000Z',
                     uptime: 123.4,
                     environment: 'production',
-                    checks: { api: 'up', cache: 'up', stellarRpc: 'up' },
+                    lastIndexedLedger: 12345678,
+                    checks: { api: 'up', cache: 'up', stellarRpc: 'up', databasePrimary: 'up', databaseReplica: 'up', prisma: 'up', jobs: 'up', indexer: 'up' },
+                    sorobanCircuitBreaker: { state: 'closed', failures: 0, retryAfterMs: 0 },
                   },
                 },
               },