diff --git a/clients/client-appconfig/src/protocols/Aws_restJson1.ts b/clients/client-appconfig/src/protocols/Aws_restJson1.ts
index 329b8bf0833c..631c98c714e7 100644
--- a/clients/client-appconfig/src/protocols/Aws_restJson1.ts
+++ b/clients/client-appconfig/src/protocols/Aws_restJson1.ts
@@ -326,7 +326,7 @@ export const se_CreateHostedConfigurationVersionCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_CT]! || "application/octet-stream",
+    [_ct]: input[_CT] || "application/octet-stream",
     [_d]: input[_D]!,
     [_lvn]: [() => isSerializableHeaderValue(input[_LVN]), () => input[_LVN]!.toString()],
     [_v]: input[_VL]!,
diff --git a/clients/client-bedrock-runtime/src/protocols/Aws_restJson1.ts b/clients/client-bedrock-runtime/src/protocols/Aws_restJson1.ts
index bd6ec3bedb60..ee3b3fbc1cfb 100644
--- a/clients/client-bedrock-runtime/src/protocols/Aws_restJson1.ts
+++ b/clients/client-bedrock-runtime/src/protocols/Aws_restJson1.ts
@@ -150,7 +150,7 @@ export const se_InvokeModelCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
     [_a]: input[_a]!,
     [_xabt]: input[_t]!,
     [_xabg]: input[_gI]!,
@@ -175,7 +175,7 @@ export const se_InvokeModelWithResponseStreamCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
     [_xaba]: input[_a]!,
     [_xabt]: input[_t]!,
     [_xabg]: input[_gI]!,
diff --git a/clients/client-billingconductor/src/protocols/Aws_restJson1.ts b/clients/client-billingconductor/src/protocols/Aws_restJson1.ts
index b559573a077d..501b51296898 100644
--- a/clients/client-billingconductor/src/protocols/Aws_restJson1.ts
+++ b/clients/client-billingconductor/src/protocols/Aws_restJson1.ts
@@ -258,7 +258,7 @@ export const se_CreateBillingGroupCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/create-billing-group");
   let body: any;
@@ -286,7 +286,7 @@ export const se_CreateCustomLineItemCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/create-custom-line-item");
   let body: any;
@@ -315,7 +315,7 @@ export const se_CreatePricingPlanCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/create-pricing-plan");
   let body: any;
@@ -341,7 +341,7 @@ export const se_CreatePricingRuleCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/create-pricing-rule");
   let body: any;
diff --git a/clients/client-cloudsearch-domain/src/protocols/Aws_restJson1.ts b/clients/client-cloudsearch-domain/src/protocols/Aws_restJson1.ts
index 3c9d2bc8a0b6..861642aa9d0d 100644
--- a/clients/client-cloudsearch-domain/src/protocols/Aws_restJson1.ts
+++ b/clients/client-cloudsearch-domain/src/protocols/Aws_restJson1.ts
@@ -89,7 +89,7 @@ export const se_UploadDocumentsCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/2013-01-01/documents/batch");
   const query: any = map({
diff --git a/clients/client-codeguruprofiler/src/protocols/Aws_restJson1.ts b/clients/client-codeguruprofiler/src/protocols/Aws_restJson1.ts
index dbd23d3eac7e..98ce96dcb4a6 100644
--- a/clients/client-codeguruprofiler/src/protocols/Aws_restJson1.ts
+++ b/clients/client-codeguruprofiler/src/protocols/Aws_restJson1.ts
@@ -437,7 +437,7 @@ export const se_PostAgentProfileCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cTo]! || "application/octet-stream",
+    [_ct]: input[_cTo] || "application/octet-stream",
   });
   b.bp("/profilingGroups/{profilingGroupName}/agentProfile");
   b.p("profilingGroupName", () => input.profilingGroupName!, "{profilingGroupName}", false);
diff --git a/clients/client-deadline/src/protocols/Aws_restJson1.ts b/clients/client-deadline/src/protocols/Aws_restJson1.ts
index 8bf66e163caf..dfa683677256 100644
--- a/clients/client-deadline/src/protocols/Aws_restJson1.ts
+++ b/clients/client-deadline/src/protocols/Aws_restJson1.ts
@@ -703,7 +703,7 @@ export const se_CreateBudgetCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/budgets");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -740,7 +740,7 @@ export const se_CreateFarmCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms");
   let body: any;
@@ -774,7 +774,7 @@ export const se_CreateFleetCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/fleets");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -812,7 +812,7 @@ export const se_CreateJobCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/jobs");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -853,7 +853,7 @@ export const se_CreateLicenseEndpointCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/license-endpoints");
   let body: any;
@@ -887,7 +887,7 @@ export const se_CreateMonitorCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/monitors");
   let body: any;
@@ -921,7 +921,7 @@ export const se_CreateQueueCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -961,7 +961,7 @@ export const se_CreateQueueEnvironmentCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/environments");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -1028,7 +1028,7 @@ export const se_CreateStorageProfileCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/storage-profiles");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -1062,7 +1062,7 @@ export const se_CreateWorkerCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/fleets/{fleetId}/workers");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -1143,7 +1143,7 @@ export const se_DeleteFleetCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/fleets/{fleetId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -2935,7 +2935,7 @@ export const se_UpdateBudgetCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/budgets/{budgetId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3006,7 +3006,7 @@ export const se_UpdateFleetCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/fleets/{fleetId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3044,7 +3044,7 @@ export const se_UpdateJobCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/jobs/{jobId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3115,7 +3115,7 @@ export const se_UpdateQueueCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3157,7 +3157,7 @@ export const se_UpdateQueueEnvironmentCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/environments/{queueEnvironmentId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3226,7 +3226,7 @@ export const se_UpdateSessionCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/jobs/{jobId}/sessions/{sessionId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3261,7 +3261,7 @@ export const se_UpdateStepCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/jobs/{jobId}/steps/{stepId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3296,7 +3296,7 @@ export const se_UpdateStorageProfileCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/storage-profiles/{storageProfileId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
@@ -3332,7 +3332,7 @@ export const se_UpdateTaskCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2023-10-12/farms/{farmId}/queues/{queueId}/jobs/{jobId}/steps/{stepId}/tasks/{taskId}");
   b.p("farmId", () => input.farmId!, "{farmId}", false);
diff --git a/clients/client-lex-runtime-service/src/protocols/Aws_restJson1.ts b/clients/client-lex-runtime-service/src/protocols/Aws_restJson1.ts
index 0f1ed44995f3..96eace9d38d1 100644
--- a/clients/client-lex-runtime-service/src/protocols/Aws_restJson1.ts
+++ b/clients/client-lex-runtime-service/src/protocols/Aws_restJson1.ts
@@ -99,7 +99,7 @@ export const se_PostContentCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "x-amz-content-sha256": "UNSIGNED-PAYLOAD",
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
     [_xalsa]: [
       () => isSerializableHeaderValue(input[_sA]),
       () => context.base64Encoder(Buffer.from(__LazyJsonString.fromObject(input[_sA]!))),
diff --git a/clients/client-lex-runtime-v2/src/protocols/Aws_restJson1.ts b/clients/client-lex-runtime-v2/src/protocols/Aws_restJson1.ts
index 18db24c80674..cc122e53322f 100644
--- a/clients/client-lex-runtime-v2/src/protocols/Aws_restJson1.ts
+++ b/clients/client-lex-runtime-v2/src/protocols/Aws_restJson1.ts
@@ -180,7 +180,7 @@ export const se_RecognizeUtteranceCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "x-amz-content-sha256": "UNSIGNED-PAYLOAD",
-    [_ct]: input[_rCTe]! || "application/octet-stream",
+    [_ct]: input[_rCTe] || "application/octet-stream",
     [_xalss]: input[_sS]!,
     [_xalra]: input[_rA]!,
     [_rct]: input[_rCT]!,
diff --git a/clients/client-lookoutvision/src/protocols/Aws_restJson1.ts b/clients/client-lookoutvision/src/protocols/Aws_restJson1.ts
index 282a082ff5bf..f940c8a6ce08 100644
--- a/clients/client-lookoutvision/src/protocols/Aws_restJson1.ts
+++ b/clients/client-lookoutvision/src/protocols/Aws_restJson1.ts
@@ -108,7 +108,7 @@ export const se_CreateDatasetCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/datasets");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -133,7 +133,7 @@ export const se_CreateModelCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/models");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -160,7 +160,7 @@ export const se_CreateProjectCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects");
   let body: any;
@@ -182,7 +182,7 @@ export const se_DeleteDatasetCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/datasets/{DatasetType}");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -201,7 +201,7 @@ export const se_DeleteModelCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/models/{ModelVersion}");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -220,7 +220,7 @@ export const se_DeleteProjectCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -305,7 +305,7 @@ export const se_DetectAnomaliesCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_CTo]! || "application/octet-stream",
+    [_ct]: input[_CTo] || "application/octet-stream",
   });
   b.bp("/2020-11-20/projects/{ProjectName}/models/{ModelVersion}/detect");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -429,7 +429,7 @@ export const se_StartModelCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/models/{ModelVersion}/start");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -455,7 +455,7 @@ export const se_StartModelPackagingJobCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/modelpackagingjobs");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -481,7 +481,7 @@ export const se_StopModelCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/models/{ModelVersion}/stop");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
@@ -546,7 +546,7 @@ export const se_UpdateDatasetEntriesCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-11-20/projects/{ProjectName}/datasets/{DatasetType}/entries");
   b.p("ProjectName", () => input.ProjectName!, "{ProjectName}", false);
diff --git a/clients/client-mediapackagev2/src/protocols/Aws_restJson1.ts b/clients/client-mediapackagev2/src/protocols/Aws_restJson1.ts
index 3679c7f36929..5a38088603ea 100644
--- a/clients/client-mediapackagev2/src/protocols/Aws_restJson1.ts
+++ b/clients/client-mediapackagev2/src/protocols/Aws_restJson1.ts
@@ -121,7 +121,7 @@ export const se_CreateChannelCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/channelGroup/{ChannelGroupName}/channel");
   b.p("ChannelGroupName", () => input.ChannelGroupName!, "{ChannelGroupName}", false);
@@ -148,7 +148,7 @@ export const se_CreateChannelGroupCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/channelGroup");
   let body: any;
@@ -173,7 +173,7 @@ export const se_CreateOriginEndpointCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_CT]!,
+    [_xact]: input[_CT] ?? generateIdempotencyToken(),
   });
   b.bp("/channelGroup/{ChannelGroupName}/channel/{ChannelName}/originEndpoint");
   b.p("ChannelGroupName", () => input.ChannelGroupName!, "{ChannelGroupName}", false);
diff --git a/clients/client-mediastore-data/src/protocols/Aws_restJson1.ts b/clients/client-mediastore-data/src/protocols/Aws_restJson1.ts
index af325571e236..c99bad268fbb 100644
--- a/clients/client-mediastore-data/src/protocols/Aws_restJson1.ts
+++ b/clients/client-mediastore-data/src/protocols/Aws_restJson1.ts
@@ -121,7 +121,7 @@ export const se_PutObjectCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "x-amz-content-sha256": "UNSIGNED-PAYLOAD",
-    [_ct]: input[_CT]! || "application/octet-stream",
+    [_ct]: input[_CT] || "application/octet-stream",
     [_cc]: input[_CC]!,
     [_xasc]: input[_SC]!,
     [_xaua]: input[_UA]!,
diff --git a/clients/client-nimble/src/protocols/Aws_restJson1.ts b/clients/client-nimble/src/protocols/Aws_restJson1.ts
index 8e6e508846d6..92869a485440 100644
--- a/clients/client-nimble/src/protocols/Aws_restJson1.ts
+++ b/clients/client-nimble/src/protocols/Aws_restJson1.ts
@@ -214,7 +214,7 @@ export const se_AcceptEulasCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/eula-acceptances");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -238,7 +238,7 @@ export const se_CreateLaunchProfileCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -268,7 +268,7 @@ export const se_CreateStreamingImageCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-images");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -295,7 +295,7 @@ export const se_CreateStreamingSessionCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-sessions");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -323,7 +323,7 @@ export const se_CreateStreamingSessionStreamCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-sessions/{sessionId}/streams");
   b.p("sessionId", () => input.sessionId!, "{sessionId}", false);
@@ -348,7 +348,7 @@ export const se_CreateStudioCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios");
   let body: any;
@@ -376,7 +376,7 @@ export const se_CreateStudioComponentCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/studio-components");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -409,7 +409,7 @@ export const se_DeleteLaunchProfileCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles/{launchProfileId}");
   b.p("launchProfileId", () => input.launchProfileId!, "{launchProfileId}", false);
@@ -428,7 +428,7 @@ export const se_DeleteLaunchProfileMemberCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles/{launchProfileId}/membership/{principalId}");
   b.p("launchProfileId", () => input.launchProfileId!, "{launchProfileId}", false);
@@ -448,7 +448,7 @@ export const se_DeleteStreamingImageCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-images/{streamingImageId}");
   b.p("streamingImageId", () => input.streamingImageId!, "{streamingImageId}", false);
@@ -467,7 +467,7 @@ export const se_DeleteStreamingSessionCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-sessions/{sessionId}");
   b.p("sessionId", () => input.sessionId!, "{sessionId}", false);
@@ -486,7 +486,7 @@ export const se_DeleteStudioCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -504,7 +504,7 @@ export const se_DeleteStudioComponentCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/studio-components/{studioComponentId}");
   b.p("studioComponentId", () => input.studioComponentId!, "{studioComponentId}", false);
@@ -523,7 +523,7 @@ export const se_DeleteStudioMemberCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/membership/{principalId}");
   b.p("principalId", () => input.principalId!, "{principalId}", false);
@@ -975,7 +975,7 @@ export const se_PutLaunchProfileMembersCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles/{launchProfileId}/membership");
   b.p("launchProfileId", () => input.launchProfileId!, "{launchProfileId}", false);
@@ -1001,7 +1001,7 @@ export const se_PutStudioMembersCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/membership");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -1026,7 +1026,7 @@ export const se_StartStreamingSessionCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-sessions/{sessionId}/start");
   b.p("sessionId", () => input.sessionId!, "{sessionId}", false);
@@ -1050,7 +1050,7 @@ export const se_StartStudioSSOConfigurationRepairCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/sso-configuration");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -1069,7 +1069,7 @@ export const se_StopStreamingSessionCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-sessions/{sessionId}/stop");
   b.p("sessionId", () => input.sessionId!, "{sessionId}", false);
@@ -1139,7 +1139,7 @@ export const se_UpdateLaunchProfileCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles/{launchProfileId}");
   b.p("launchProfileId", () => input.launchProfileId!, "{launchProfileId}", false);
@@ -1168,7 +1168,7 @@ export const se_UpdateLaunchProfileMemberCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/launch-profiles/{launchProfileId}/membership/{principalId}");
   b.p("launchProfileId", () => input.launchProfileId!, "{launchProfileId}", false);
@@ -1194,7 +1194,7 @@ export const se_UpdateStreamingImageCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/streaming-images/{streamingImageId}");
   b.p("streamingImageId", () => input.streamingImageId!, "{streamingImageId}", false);
@@ -1220,7 +1220,7 @@ export const se_UpdateStudioCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}");
   b.p("studioId", () => input.studioId!, "{studioId}", false);
@@ -1246,7 +1246,7 @@ export const se_UpdateStudioComponentCommand = async (
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
     "content-type": "application/json",
-    [_xact]: input[_cT]!,
+    [_xact]: input[_cT] ?? generateIdempotencyToken(),
   });
   b.bp("/2020-08-01/studios/{studioId}/studio-components/{studioComponentId}");
   b.p("studioComponentId", () => input.studioComponentId!, "{studioComponentId}", false);
diff --git a/clients/client-s3/src/protocols/Aws_restXml.ts b/clients/client-s3/src/protocols/Aws_restXml.ts
index b60534c5a66b..e7b56ec4af38 100644
--- a/clients/client-s3/src/protocols/Aws_restXml.ts
+++ b/clients/client-s3/src/protocols/Aws_restXml.ts
@@ -2618,7 +2618,7 @@ export const se_PutObjectCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_CT]! || "application/octet-stream",
+    [_ct]: input[_CT] || "application/octet-stream",
     [_xaa]: input[_ACL]!,
     [_cc]: input[_CC]!,
     [_cd]: input[_CD]!,
diff --git a/clients/client-sagemaker-runtime/src/protocols/Aws_restJson1.ts b/clients/client-sagemaker-runtime/src/protocols/Aws_restJson1.ts
index b3ac0fc4406e..cefe9e07b98d 100644
--- a/clients/client-sagemaker-runtime/src/protocols/Aws_restJson1.ts
+++ b/clients/client-sagemaker-runtime/src/protocols/Aws_restJson1.ts
@@ -54,7 +54,7 @@ export const se_InvokeEndpointCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_CT]! || "application/octet-stream",
+    [_ct]: input[_CT] || "application/octet-stream",
     [_a]: input[_A]!,
     [_xasca]: input[_CA]!,
     [_xastm]: input[_TM]!,
@@ -107,7 +107,7 @@ export const se_InvokeEndpointWithResponseStreamCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_CT]! || "application/octet-stream",
+    [_ct]: input[_CT] || "application/octet-stream",
     [_xasa]: input[_A]!,
     [_xasca]: input[_CA]!,
     [_xastv]: input[_TV]!,
diff --git a/clients/client-tnb/src/protocols/Aws_restJson1.ts b/clients/client-tnb/src/protocols/Aws_restJson1.ts
index be13975d1b59..5eb097e547c1 100644
--- a/clients/client-tnb/src/protocols/Aws_restJson1.ts
+++ b/clients/client-tnb/src/protocols/Aws_restJson1.ts
@@ -606,7 +606,7 @@ export const se_PutSolFunctionPackageContentCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/sol/vnfpkgm/v1/vnf_packages/{vnfPkgId}/package_content");
   b.p("vnfPkgId", () => input.vnfPkgId!, "{vnfPkgId}", false);
@@ -627,7 +627,7 @@ export const se_PutSolNetworkPackageContentCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/sol/nsd/v1/ns_descriptors/{nsdInfoId}/nsd_content");
   b.p("nsdInfoId", () => input.nsdInfoId!, "{nsdInfoId}", false);
@@ -787,7 +787,7 @@ export const se_ValidateSolFunctionPackageContentCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/sol/vnfpkgm/v1/vnf_packages/{vnfPkgId}/package_content/validate");
   b.p("vnfPkgId", () => input.vnfPkgId!, "{vnfPkgId}", false);
@@ -808,7 +808,7 @@ export const se_ValidateSolNetworkPackageContentCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/sol/nsd/v1/ns_descriptors/{nsdInfoId}/nsd_content/validate");
   b.p("nsdInfoId", () => input.nsdInfoId!, "{nsdInfoId}", false);
diff --git a/private/aws-protocoltests-restjson/src/protocols/Aws_restJson1.ts b/private/aws-protocoltests-restjson/src/protocols/Aws_restJson1.ts
index 92dad884b5cf..7bdb8a5be0e4 100644
--- a/private/aws-protocoltests-restjson/src/protocols/Aws_restJson1.ts
+++ b/private/aws-protocoltests-restjson/src/protocols/Aws_restJson1.ts
@@ -2484,7 +2484,7 @@ export const se_TestPayloadBlobCommand = async (
 ): Promise<__HttpRequest> => {
   const b = rb(input, context);
   const headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   b.bp("/blob_payload");
   let body: any;
diff --git a/private/aws-restjson-server/src/protocols/Aws_restJson1.ts b/private/aws-restjson-server/src/protocols/Aws_restJson1.ts
index 644bc1729827..2ba6f6bdb57c 100644
--- a/private/aws-restjson-server/src/protocols/Aws_restJson1.ts
+++ b/private/aws-restjson-server/src/protocols/Aws_restJson1.ts
@@ -7448,7 +7448,7 @@ export const serializeTestPayloadBlobResponse = async (
   };
   const statusCode = 200;
   let headers: any = map({}, isSerializableHeaderValue, {
-    [_ct]: input[_cT]! || "application/octet-stream",
+    [_ct]: input[_cT] || "application/octet-stream",
   });
   let body: any;
   if (input.data !== undefined) {