diff --git a/.projenrc.ts b/.projenrc.ts
index 319a7b950..43286463c 100644
--- a/.projenrc.ts
+++ b/.projenrc.ts
@@ -863,7 +863,7 @@ cli.gitignore.addPatterns('build-info.json');
 const cliPackageJson = `${cli.workspaceDirectory}/package.json`;
 
 cli.preCompileTask.prependExec('./generate.sh');
-cli.preCompileTask.prependExec('ts-node scripts/user-input-gen.ts');
+cli.preCompileTask.prependExec('ts-node --prefer-ts-exts scripts/user-input-gen.ts');
 
 const includeCliResourcesCommands = [
   'cp $(node -p \'require.resolve("cdk-from-cfn/index_bg.wasm")\') ./lib/',
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts b/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
index e79757154..85c4b2d2d 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
@@ -8,29 +8,27 @@ export { Settings } from '../../../../aws-cdk/lib/api/settings';
 export { tagsForStack } from '../../../../aws-cdk/lib/api/tags';
 export { DEFAULT_TOOLKIT_STACK_NAME } from '../../../../aws-cdk/lib/api/toolkit-info';
 export { ResourceMigrator } from '../../../../aws-cdk/lib/api/resource-import';
+export { StackActivityProgress } from '../../../../aws-cdk/lib/api/stack-events';
+export { CloudWatchLogEventMonitor, findCloudWatchLogGroups } from '../../../../aws-cdk/lib/api/logs';
+export { WorkGraph, WorkGraphBuilder, AssetBuildNode, AssetPublishNode, StackNode, Concurrency } from '../../../../aws-cdk/lib/api/work-graph';
 
 // Context Providers
 export * as contextproviders from '../../../../aws-cdk/lib/context-providers';
 
+// utils
+export { formatTime } from '../../../../aws-cdk/lib/util/string-manipulation';
+export { formatErrorMessage } from '../../../../aws-cdk/lib/util/format-error';
+export { obscureTemplate, serializeStructure } from '../../../../aws-cdk/lib/util/serialize';
+export { validateSnsTopicArn } from '../../../../aws-cdk/lib/util/cloudformation';
+export { splitBySize } from '../../../../aws-cdk/lib/util/objects';
+
 // @todo APIs not clean import
 export { HotswapMode } from '../../../../aws-cdk/lib/api/hotswap/common';
-export { StackActivityProgress } from '../../../../aws-cdk/lib/api/util/cloudformation/stack-activity-monitor';
+export { HotswapPropertyOverrides, EcsHotswapProperties } from '../../../../aws-cdk/lib/api/hotswap/common';
 export { RWLock, type ILock } from '../../../../aws-cdk/lib/api/util/rwlock';
-export { formatTime } from '../../../../aws-cdk/lib/api/util/string-manipulation';
 
 // @todo Not yet API probably should be
-export { formatErrorMessage } from '../../../../aws-cdk/lib/util/error';
-export { obscureTemplate, serializeStructure } from '../../../../aws-cdk/lib/serialize';
 export { loadTree, some } from '../../../../aws-cdk/lib/tree';
-export { splitBySize } from '../../../../aws-cdk/lib/util';
-export { validateSnsTopicArn } from '../../../../aws-cdk/lib/util/validate-notification-arn';
-export { WorkGraph } from '../../../../aws-cdk/lib/util/work-graph';
-export type { Concurrency } from '../../../../aws-cdk/lib/util/work-graph';
-export { WorkGraphBuilder } from '../../../../aws-cdk/lib/util/work-graph-builder';
-export type { AssetBuildNode, AssetPublishNode, StackNode } from '../../../../aws-cdk/lib/util/work-graph-types';
-export { CloudWatchLogEventMonitor } from '../../../../aws-cdk/lib/api/logs/logs-monitor';
-export { findCloudWatchLogGroups } from '../../../../aws-cdk/lib/api/logs/find-cloudwatch-logs';
-export { HotswapPropertyOverrides, EcsHotswapProperties } from '../../../../aws-cdk/lib/api/hotswap/common';
 
 // @todo Cloud Assembly and Executable - this is a messy API right now
 export { CloudAssembly, sanitizePatterns, type StackDetails, StackCollection, ExtendedStackSelection } from '../../../../aws-cdk/lib/api/cxapp/cloud-assembly';
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/private/context-aware-source.ts b/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/private/context-aware-source.ts
index f4d0e2d2e..e39bc8d4f 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/private/context-aware-source.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/private/context-aware-source.ts
@@ -1,7 +1,7 @@
 import type { MissingContext } from '@aws-cdk/cloud-assembly-schema';
 import * as cxapi from '@aws-cdk/cx-api';
 import { ToolkitServices } from '../../../toolkit/private';
-import { Context, contextproviders, PROJECT_CONTEXT } from '../../aws-cdk';
+import { type Context, contextproviders, PROJECT_CONTEXT } from '../../aws-cdk';
 import { ToolkitError } from '../../errors';
 import { ActionAwareIoHost, debug } from '../../io/private';
 import { ICloudAssemblySource } from '../types';
diff --git a/packages/aws-cdk/.projen/tasks.json b/packages/aws-cdk/.projen/tasks.json
index 49151b887..eff3eee71 100644
--- a/packages/aws-cdk/.projen/tasks.json
+++ b/packages/aws-cdk/.projen/tasks.json
@@ -165,7 +165,7 @@
       "description": "Prepare the project for compilation",
       "steps": [
         {
-          "exec": "ts-node scripts/user-input-gen.ts"
+          "exec": "ts-node --prefer-ts-exts scripts/user-input-gen.ts"
         },
         {
           "exec": "./generate.sh"
diff --git a/packages/aws-cdk/lib/api/aws-auth/credential-plugins.ts b/packages/aws-cdk/lib/api/aws-auth/credential-plugins.ts
index 6f70ab67b..8342f5142 100644
--- a/packages/aws-cdk/lib/api/aws-auth/credential-plugins.ts
+++ b/packages/aws-cdk/lib/api/aws-auth/credential-plugins.ts
@@ -4,7 +4,7 @@ import type { AwsCredentialIdentity, AwsCredentialIdentityProvider } from '@smit
 import { credentialsAboutToExpire, makeCachingProvider } from './provider-caching';
 import { debug, warning } from '../../logging';
 import { AuthenticationError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import { Mode } from '../plugin/mode';
 import { PluginHost } from '../plugin/plugin';
 
diff --git a/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts b/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
index 4ac90ad16..2a3d8230c 100644
--- a/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
+++ b/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
@@ -1,7 +1,7 @@
 import { inspect, format } from 'util';
 import { Logger } from '@smithy/types';
-import { replacerBufferWithInfo } from '../../serialize';
 import type { IIoHost } from '../../toolkit/cli-io-host';
+import { replacerBufferWithInfo } from '../../util/serialize';
 
 export class SdkToCliLogger implements Logger {
   private readonly ioHost: IIoHost;
diff --git a/packages/aws-cdk/lib/api/aws-auth/sdk-provider.ts b/packages/aws-cdk/lib/api/aws-auth/sdk-provider.ts
index 8b5025088..55ea6fd00 100644
--- a/packages/aws-cdk/lib/api/aws-auth/sdk-provider.ts
+++ b/packages/aws-cdk/lib/api/aws-auth/sdk-provider.ts
@@ -13,7 +13,7 @@ import { SDK } from './sdk';
 import { callTrace, traceMemberMethods } from './tracing';
 import { debug, warning } from '../../logging';
 import { AuthenticationError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import { Mode } from '../plugin/mode';
 
 export type AssumeRoleAdditionalOptions = Partial<Omit<AssumeRoleCommandInput, 'ExternalId' | 'RoleArn'>>;
diff --git a/packages/aws-cdk/lib/api/aws-auth/sdk.ts b/packages/aws-cdk/lib/api/aws-auth/sdk.ts
index d544021ae..5c6c3302a 100644
--- a/packages/aws-cdk/lib/api/aws-auth/sdk.ts
+++ b/packages/aws-cdk/lib/api/aws-auth/sdk.ts
@@ -321,7 +321,7 @@ import { traceMemberMethods } from './tracing';
 import { defaultCliUserAgent } from './user-agent';
 import { debug } from '../../logging';
 import { AuthenticationError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 
 export interface S3ClientOptions {
   /**
diff --git a/packages/aws-cdk/lib/api/bootstrap/bootstrap-environment.ts b/packages/aws-cdk/lib/api/bootstrap/bootstrap-environment.ts
index 4d8547d73..fd3e45a2c 100644
--- a/packages/aws-cdk/lib/api/bootstrap/bootstrap-environment.ts
+++ b/packages/aws-cdk/lib/api/bootstrap/bootstrap-environment.ts
@@ -5,10 +5,10 @@ import type { BootstrapEnvironmentOptions, BootstrappingParameters } from './boo
 import { BootstrapStack, bootstrapVersionFromTemplate } from './deploy-bootstrap';
 import { legacyBootstrapTemplate } from './legacy-template';
 import { warn } from '../../cli/messages';
-import { loadStructuredFile, serializeStructure } from '../../serialize';
 import { IoMessaging } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
 import { rootDir } from '../../util/directories';
+import { loadStructuredFile, serializeStructure } from '../../util/serialize';
 import type { SDK, SdkProvider } from '../aws-auth';
 import type { SuccessfulDeployStackResult } from '../deployments';
 import { Mode } from '../plugin/mode';
diff --git a/packages/aws-cdk/lib/api/deployments/cloudformation.ts b/packages/aws-cdk/lib/api/deployments/cloudformation.ts
index f3892e701..56a16830a 100644
--- a/packages/aws-cdk/lib/api/deployments/cloudformation.ts
+++ b/packages/aws-cdk/lib/api/deployments/cloudformation.ts
@@ -12,14 +12,14 @@ import {
 } from '@aws-sdk/client-cloudformation';
 import { AssetManifest, FileManifestEntry } from 'cdk-assets';
 import { AssetManifestBuilder } from './asset-manifest-builder';
+import type { Deployments } from './deployments';
 import { debug } from '../../cli/messages';
-import { deserializeStructure } from '../../serialize';
 import { IoMessaging } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
+import { deserializeStructure } from '../../util/serialize';
 import type { ICloudFormationClient, SdkProvider } from '../aws-auth';
-import type { Deployments } from './deployments';
-import { StackStatus } from '../util/cloudformation/stack-status';
+import { StackStatus } from '../stack-events';
 import { makeBodyParameter, TemplateBodyParameter } from '../util/template-body-parameter';
 
 export type ResourcesToImport = ResourceToImport[];
diff --git a/packages/aws-cdk/lib/api/deployments/deploy-stack.ts b/packages/aws-cdk/lib/api/deployments/deploy-stack.ts
index 2280cfbf3..2d7e81a13 100644
--- a/packages/aws-cdk/lib/api/deployments/deploy-stack.ts
+++ b/packages/aws-cdk/lib/api/deployments/deploy-stack.ts
@@ -31,12 +31,12 @@ import { tryHotswapDeployment } from './hotswap-deployments';
 import { debug, info, warn } from '../../cli/messages';
 import { IIoHost, IoMessaging, ToolkitAction } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import type { SDK, SdkProvider, ICloudFormationClient } from '../aws-auth';
 import type { EnvironmentResources } from '../environment';
 import { CfnEvaluationException } from '../evaluate-cloudformation-template';
 import { HotswapMode, HotswapPropertyOverrides, ICON } from '../hotswap/common';
-import { StackActivityMonitor, type StackActivityProgress } from '../util/cloudformation/stack-activity-monitor';
+import { StackActivityMonitor, type StackActivityProgress } from '../stack-events';
 import { StringWithoutPlaceholders } from '../util/placeholders';
 import { type TemplateBodyParameter, makeBodyParameter } from '../util/template-body-parameter';
 
diff --git a/packages/aws-cdk/lib/api/deployments/deployments.ts b/packages/aws-cdk/lib/api/deployments/deployments.ts
index ca8a33e62..a9cc3b00e 100644
--- a/packages/aws-cdk/lib/api/deployments/deployments.ts
+++ b/packages/aws-cdk/lib/api/deployments/deployments.ts
@@ -27,15 +27,13 @@ import {
 import { debug, warn } from '../../cli/messages';
 import { IIoHost, IoMessaging, ToolkitAction } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import type { SdkProvider } from '../aws-auth/sdk-provider';
 import { type EnvironmentResources, EnvironmentAccess } from '../environment';
 import { HotswapMode, HotswapPropertyOverrides } from '../hotswap/common';
+import { StackActivityMonitor, StackActivityProgress, StackEventPoller, RollbackChoice } from '../stack-events';
 import type { Tag } from '../tags';
 import { DEFAULT_TOOLKIT_STACK_NAME } from '../toolkit-info';
-import { StackActivityMonitor, StackActivityProgress } from '../util/cloudformation/stack-activity-monitor';
-import { StackEventPoller } from '../util/cloudformation/stack-event-poller';
-import { RollbackChoice } from '../util/cloudformation/stack-status';
 import { makeBodyParameter } from '../util/template-body-parameter';
 
 const BOOTSTRAP_STACK_VERSION_FOR_ROLLBACK = 23;
diff --git a/packages/aws-cdk/lib/api/deployments/hotswap-deployments.ts b/packages/aws-cdk/lib/api/deployments/hotswap-deployments.ts
index 6fa5617e1..2066ea82a 100644
--- a/packages/aws-cdk/lib/api/deployments/hotswap-deployments.ts
+++ b/packages/aws-cdk/lib/api/deployments/hotswap-deployments.ts
@@ -8,7 +8,7 @@ import type { CloudFormationStack } from './cloudformation';
 import { NestedStackTemplates, loadCurrentTemplateWithNestedStacks } from './nested-stack-helpers';
 import { info } from '../../cli/messages';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import { EvaluateCloudFormationTemplate } from '../evaluate-cloudformation-template';
 import { isHotswappableAppSyncChange } from '../hotswap/appsync-mapping-templates';
 import { isHotswappableCodeBuildProjectChange } from '../hotswap/code-build-projects';
diff --git a/packages/aws-cdk/lib/api/deployments/nested-stack-helpers.ts b/packages/aws-cdk/lib/api/deployments/nested-stack-helpers.ts
index cb3fc1c75..09d6445f8 100644
--- a/packages/aws-cdk/lib/api/deployments/nested-stack-helpers.ts
+++ b/packages/aws-cdk/lib/api/deployments/nested-stack-helpers.ts
@@ -3,7 +3,7 @@ import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
 import * as fs from 'fs-extra';
 import type { SDK } from '../aws-auth';
 import { CloudFormationStack, type Template } from './cloudformation';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import { LazyListStackResources, type ListStackResources } from '../evaluate-cloudformation-template';
 
 export interface NestedStackTemplates {
diff --git a/packages/aws-cdk/lib/api/environment/environment-access.ts b/packages/aws-cdk/lib/api/environment/environment-access.ts
index 309d2dd55..2d3fe1288 100644
--- a/packages/aws-cdk/lib/api/environment/environment-access.ts
+++ b/packages/aws-cdk/lib/api/environment/environment-access.ts
@@ -4,7 +4,7 @@ import { EnvironmentResources, EnvironmentResourcesRegistry } from './environmen
 import { warn } from '../../cli/messages';
 import { IoMessaging } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import { CredentialsOptions, SdkForEnvironment, SdkProvider } from '../aws-auth/sdk-provider';
 import { Mode } from '../plugin/mode';
 import { replaceEnvPlaceholders, StringWithoutPlaceholders } from '../util/placeholders';
diff --git a/packages/aws-cdk/lib/api/environment/environment-resources.ts b/packages/aws-cdk/lib/api/environment/environment-resources.ts
index 084296830..df4155592 100644
--- a/packages/aws-cdk/lib/api/environment/environment-resources.ts
+++ b/packages/aws-cdk/lib/api/environment/environment-resources.ts
@@ -3,7 +3,7 @@ import { debug, warn } from '../../cli/messages';
 import { Notices } from '../../notices';
 import { IoMessaging } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import type { SDK } from '../aws-auth';
 import { type EcrRepositoryInfo, ToolkitInfo } from '../toolkit-info';
 
diff --git a/packages/aws-cdk/lib/api/logs/find-cloudwatch-logs.ts b/packages/aws-cdk/lib/api/logs/find-cloudwatch-logs.ts
index f2317200b..194a8003b 100644
--- a/packages/aws-cdk/lib/api/logs/find-cloudwatch-logs.ts
+++ b/packages/aws-cdk/lib/api/logs/find-cloudwatch-logs.ts
@@ -2,7 +2,7 @@ import type { CloudFormationStackArtifact, Environment } from '@aws-cdk/cx-api';
 import type { StackResourceSummary } from '@aws-sdk/client-cloudformation';
 import { debug } from '../../logging';
 import { IoMessaging } from '../../toolkit/cli-io-host';
-import { formatErrorMessage } from '../../util/error';
+import { formatErrorMessage } from '../../util/format-error';
 import type { SDK, SdkProvider } from '../aws-auth';
 import { EnvironmentAccess } from '../environment';
 import { EvaluateCloudFormationTemplate, LazyListStackResources } from '../evaluate-cloudformation-template';
diff --git a/packages/aws-cdk/lib/api/logs/index.ts b/packages/aws-cdk/lib/api/logs/index.ts
new file mode 100644
index 000000000..4475be9a7
--- /dev/null
+++ b/packages/aws-cdk/lib/api/logs/index.ts
@@ -0,0 +1,2 @@
+export * from './logs-monitor';
+export * from './find-cloudwatch-logs';
diff --git a/packages/aws-cdk/lib/api/resource-import/importer.ts b/packages/aws-cdk/lib/api/resource-import/importer.ts
index 3246aa4fc..894113315 100644
--- a/packages/aws-cdk/lib/api/resource-import/importer.ts
+++ b/packages/aws-cdk/lib/api/resource-import/importer.ts
@@ -9,8 +9,8 @@ import { error, info, warn } from '../../cli/messages';
 import { IIoHost, ToolkitAction } from '../../toolkit/cli-io-host';
 import { ToolkitError } from '../../toolkit/error';
 import { assertIsSuccessfulDeployStackResult, type Deployments, DeploymentMethod, ResourceIdentifierProperties, ResourcesToImport } from '../deployments';
-import { Tag } from '../tags';
-import { StackActivityProgress } from '../util/cloudformation/stack-activity-monitor';
+import type { StackActivityProgress } from '../stack-events';
+import type { Tag } from '../tags';
 
 export interface ResourceImporterProps {
   deployments: Deployments;
diff --git a/packages/aws-cdk/lib/api/resource-import/migrator.ts b/packages/aws-cdk/lib/api/resource-import/migrator.ts
index 06e2b5208..e0f2e421a 100644
--- a/packages/aws-cdk/lib/api/resource-import/migrator.ts
+++ b/packages/aws-cdk/lib/api/resource-import/migrator.ts
@@ -4,9 +4,9 @@ import * as fs from 'fs-extra';
 import { ImportDeploymentOptions, ResourceImporter } from './importer';
 import { info } from '../../cli/messages';
 import type { IIoHost, ToolkitAction } from '../../toolkit/cli-io-host';
+import { formatTime } from '../../util/string-manipulation';
 import { StackCollection } from '../cxapp/cloud-assembly';
 import type { Deployments, ResourcesToImport } from '../deployments';
-import { formatTime } from '../util/string-manipulation';
 
 export interface ResourceMigratorProps {
   deployments: Deployments;
diff --git a/packages/aws-cdk/lib/api/util/display.ts b/packages/aws-cdk/lib/api/stack-events/display.ts
similarity index 100%
rename from packages/aws-cdk/lib/api/util/display.ts
rename to packages/aws-cdk/lib/api/stack-events/display.ts
diff --git a/packages/aws-cdk/lib/api/stack-events/index.ts b/packages/aws-cdk/lib/api/stack-events/index.ts
new file mode 100644
index 000000000..831096516
--- /dev/null
+++ b/packages/aws-cdk/lib/api/stack-events/index.ts
@@ -0,0 +1,3 @@
+export * from './stack-activity-monitor';
+export * from './stack-event-poller';
+export * from './stack-status';
diff --git a/packages/aws-cdk/lib/api/util/cloudformation/stack-activity-monitor.ts b/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
similarity index 99%
rename from packages/aws-cdk/lib/api/util/cloudformation/stack-activity-monitor.ts
rename to packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
index de46599ce..962b505dd 100644
--- a/packages/aws-cdk/lib/api/util/cloudformation/stack-activity-monitor.ts
+++ b/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
@@ -3,10 +3,10 @@ import { ArtifactMetadataEntryType, type MetadataEntry } from '@aws-cdk/cloud-as
 import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
 import * as chalk from 'chalk';
 import { ResourceEvent, StackEventPoller } from './stack-event-poller';
-import { error, info } from '../../../logging';
-import { CliIoHost, IoMessageLevel } from '../../../toolkit/cli-io-host';
-import type { ICloudFormationClient } from '../../aws-auth';
-import { RewritableBlock } from '../display';
+import { error, info } from '../../logging';
+import { CliIoHost, IoMessageLevel } from '../../toolkit/cli-io-host';
+import type { ICloudFormationClient } from '../aws-auth';
+import { RewritableBlock } from './display';
 
 export interface StackActivity extends ResourceEvent {
   readonly metadata?: ResourceMetadata;
diff --git a/packages/aws-cdk/lib/api/util/cloudformation/stack-event-poller.ts b/packages/aws-cdk/lib/api/stack-events/stack-event-poller.ts
similarity index 98%
rename from packages/aws-cdk/lib/api/util/cloudformation/stack-event-poller.ts
rename to packages/aws-cdk/lib/api/stack-events/stack-event-poller.ts
index d0a688e32..02f93970d 100644
--- a/packages/aws-cdk/lib/api/util/cloudformation/stack-event-poller.ts
+++ b/packages/aws-cdk/lib/api/stack-events/stack-event-poller.ts
@@ -1,6 +1,6 @@
 import type { StackEvent } from '@aws-sdk/client-cloudformation';
-import { formatErrorMessage } from '../../../util/error';
-import type { ICloudFormationClient } from '../../aws-auth';
+import { formatErrorMessage } from '../../util/format-error';
+import type { ICloudFormationClient } from '../aws-auth';
 
 export interface StackEventPollerProps {
   /**
diff --git a/packages/aws-cdk/lib/api/util/cloudformation/stack-status.ts b/packages/aws-cdk/lib/api/stack-events/stack-status.ts
similarity index 100%
rename from packages/aws-cdk/lib/api/util/cloudformation/stack-status.ts
rename to packages/aws-cdk/lib/api/stack-events/stack-status.ts
diff --git a/packages/aws-cdk/lib/api/util/template-body-parameter.ts b/packages/aws-cdk/lib/api/util/template-body-parameter.ts
index 4e80b43f9..ca9b5ab02 100644
--- a/packages/aws-cdk/lib/api/util/template-body-parameter.ts
+++ b/packages/aws-cdk/lib/api/util/template-body-parameter.ts
@@ -5,9 +5,9 @@ import { getEndpointFromInstructions } from '@smithy/middleware-endpoint';
 import * as chalk from 'chalk';
 import * as fs from 'fs-extra';
 import { debug, error } from '../../logging';
-import { toYAML } from '../../serialize';
 import { ToolkitError } from '../../toolkit/error';
 import { contentHash } from '../../util/content-hash';
+import { toYAML } from '../../util/serialize';
 import { type AssetManifestBuilder } from '../deployments';
 import { EnvironmentResources } from '../environment';
 
diff --git a/packages/aws-cdk/lib/api/work-graph/index.ts b/packages/aws-cdk/lib/api/work-graph/index.ts
new file mode 100644
index 000000000..f06d9a3b5
--- /dev/null
+++ b/packages/aws-cdk/lib/api/work-graph/index.ts
@@ -0,0 +1,3 @@
+export * from './work-graph';
+export * from './work-graph-builder';
+export * from './work-graph-types';
diff --git a/packages/aws-cdk/lib/util/work-graph-builder.ts b/packages/aws-cdk/lib/api/work-graph/work-graph-builder.ts
similarity index 98%
rename from packages/aws-cdk/lib/util/work-graph-builder.ts
rename to packages/aws-cdk/lib/api/work-graph/work-graph-builder.ts
index 1c6888754..f7ce8c6b6 100644
--- a/packages/aws-cdk/lib/util/work-graph-builder.ts
+++ b/packages/aws-cdk/lib/api/work-graph/work-graph-builder.ts
@@ -1,9 +1,9 @@
 import * as cxapi from '@aws-cdk/cx-api';
 import { AssetManifest, type IManifestEntry } from 'cdk-assets';
-import { contentHashAny } from './content-hash';
 import { WorkGraph } from './work-graph';
 import { DeploymentState, AssetBuildNode, WorkNode } from './work-graph-types';
-import { ToolkitError } from '../toolkit/error';
+import { ToolkitError } from '../../toolkit/error';
+import { contentHashAny } from '../../util/content-hash';
 
 export class WorkGraphBuilder {
   /**
diff --git a/packages/aws-cdk/lib/util/work-graph-types.ts b/packages/aws-cdk/lib/api/work-graph/work-graph-types.ts
similarity index 100%
rename from packages/aws-cdk/lib/util/work-graph-types.ts
rename to packages/aws-cdk/lib/api/work-graph/work-graph-types.ts
diff --git a/packages/aws-cdk/lib/util/work-graph.ts b/packages/aws-cdk/lib/api/work-graph/work-graph.ts
similarity index 98%
rename from packages/aws-cdk/lib/util/work-graph.ts
rename to packages/aws-cdk/lib/api/work-graph/work-graph.ts
index ad5d4065a..451cf6386 100644
--- a/packages/aws-cdk/lib/util/work-graph.ts
+++ b/packages/aws-cdk/lib/api/work-graph/work-graph.ts
@@ -1,7 +1,7 @@
-import { parallelPromises } from './parallel';
 import { WorkNode, DeploymentState, StackNode, AssetBuildNode, AssetPublishNode } from './work-graph-types';
-import { debug, trace } from '../logging';
-import { ToolkitError } from '../toolkit/error';
+import { debug, trace } from '../../logging';
+import { ToolkitError } from '../../toolkit/error';
+import { parallelPromises } from '../../util/parallel';
 
 export type Concurrency = number | Record<WorkNode['type'], number>;
 
diff --git a/packages/aws-cdk/lib/cli/cdk-toolkit.ts b/packages/aws-cdk/lib/cli/cdk-toolkit.ts
index 53fc91273..1909023d9 100644
--- a/packages/aws-cdk/lib/cli/cdk-toolkit.ts
+++ b/packages/aws-cdk/lib/cli/cdk-toolkit.ts
@@ -25,9 +25,10 @@ import { HotswapMode, HotswapPropertyOverrides, EcsHotswapProperties } from '../
 import { findCloudWatchLogGroups } from '../api/logs/find-cloudwatch-logs';
 import { CloudWatchLogEventMonitor } from '../api/logs/logs-monitor';
 import { ResourceImporter, removeNonImportResources, ResourceMigrator } from '../api/resource-import';
+import { StackActivityProgress } from '../api/stack-events';
 import { tagsForStack, type Tag } from '../api/tags';
-import { StackActivityProgress } from '../api/util/cloudformation/stack-activity-monitor';
-import { formatTime } from '../api/util/string-manipulation';
+import { type AssetBuildNode, type AssetPublishNode, type Concurrency, type StackNode, WorkGraph } from '../api/work-graph';
+import { WorkGraphBuilder } from '../api/work-graph/work-graph-builder';
 import {
   generateCdkApp,
   generateStack,
@@ -49,15 +50,13 @@ import {
 import { printSecurityDiff, printStackDiff, RequireApproval } from '../diff';
 import { listStacks } from '../list-stacks';
 import { result as logResult, debug, error, highlight, info, success, warning } from '../logging';
-import { deserializeStructure, obscureTemplate, serializeStructure } from '../serialize';
 import { CliIoHost } from '../toolkit/cli-io-host';
 import { ToolkitError } from '../toolkit/error';
 import { numberFromBool, partition } from '../util';
-import { formatErrorMessage } from '../util/error';
-import { validateSnsTopicArn } from '../util/validate-notification-arn';
-import { Concurrency, WorkGraph } from '../util/work-graph';
-import { WorkGraphBuilder } from '../util/work-graph-builder';
-import { AssetBuildNode, AssetPublishNode, StackNode } from '../util/work-graph-types';
+import { validateSnsTopicArn } from '../util/cloudformation';
+import { formatErrorMessage } from '../util/format-error';
+import { deserializeStructure, obscureTemplate, serializeStructure } from '../util/serialize';
+import { formatTime } from '../util/string-manipulation';
 
 // Must use a require() otherwise esbuild complains about calling a namespace
 // eslint-disable-next-line @typescript-eslint/no-require-imports
diff --git a/packages/aws-cdk/lib/cli/cli-config.ts b/packages/aws-cdk/lib/cli/cli-config.ts
index 2bed63e1b..200305095 100644
--- a/packages/aws-cdk/lib/cli/cli-config.ts
+++ b/packages/aws-cdk/lib/cli/cli-config.ts
@@ -1,7 +1,7 @@
 // eslint-disable-next-line import/no-extraneous-dependencies
 import { CliHelpers, type CliConfig } from '@aws-cdk/user-input-gen';
 import * as cdk_from_cfn from 'cdk-from-cfn';
-import { StackActivityProgress } from '../api/util/cloudformation/stack-activity-monitor';
+import { StackActivityProgress } from '../api/stack-events';
 import { RequireApproval } from '../diff';
 import { availableInitLanguages } from '../init';
 
diff --git a/packages/aws-cdk/lib/util/tables.ts b/packages/aws-cdk/lib/cli/tables.ts
similarity index 100%
rename from packages/aws-cdk/lib/util/tables.ts
rename to packages/aws-cdk/lib/cli/tables.ts
diff --git a/packages/aws-cdk/lib/commands/context.ts b/packages/aws-cdk/lib/commands/context.ts
index f2a6f1a19..9b7f7f4fd 100644
--- a/packages/aws-cdk/lib/commands/context.ts
+++ b/packages/aws-cdk/lib/commands/context.ts
@@ -1,11 +1,11 @@
 import * as chalk from 'chalk';
 import { minimatch } from 'minimatch';
 import { Context } from '../api/context';
+import { renderTable } from '../cli/tables';
 import { PROJECT_CONFIG, PROJECT_CONTEXT, USER_DEFAULTS } from '../cli/user-configuration';
 import * as version from '../cli/version';
 import { error, warning, info, result } from '../logging';
 import { ToolkitError } from '../toolkit/error';
-import { renderTable } from '../util';
 
 /**
  * Options for the context command
diff --git a/packages/aws-cdk/lib/context-providers/index.ts b/packages/aws-cdk/lib/context-providers/index.ts
index f385aa505..ed5ae723a 100644
--- a/packages/aws-cdk/lib/context-providers/index.ts
+++ b/packages/aws-cdk/lib/context-providers/index.ts
@@ -16,7 +16,7 @@ import { ContextProviderPlugin } from '../api/plugin/context-provider-plugin';
 import { replaceEnvPlaceholders } from '../api/util/placeholders';
 import { debug } from '../logging';
 import { ContextProviderError } from '../toolkit/error';
-import { formatErrorMessage } from '../util/error';
+import { formatErrorMessage } from '../util/format-error';
 
 export type ContextProviderFactory = ((sdk: SdkProvider) => ContextProviderPlugin);
 export type ProviderMap = {[name: string]: ContextProviderFactory};
diff --git a/packages/aws-cdk/lib/init-hooks.ts b/packages/aws-cdk/lib/init-hooks.ts
index 14e2c4c09..ec2306150 100644
--- a/packages/aws-cdk/lib/init-hooks.ts
+++ b/packages/aws-cdk/lib/init-hooks.ts
@@ -1,7 +1,7 @@
 import * as path from 'path';
 import { shell } from './os';
 import { ToolkitError } from './toolkit/error';
-import { formatErrorMessage } from './util/error';
+import { formatErrorMessage } from './util/format-error';
 
 export type SubstitutePlaceholders = (...fileNames: string[]) => Promise<void>;
 
diff --git a/packages/aws-cdk/lib/init.ts b/packages/aws-cdk/lib/init.ts
index 7e3d496e2..ab3e3a5df 100644
--- a/packages/aws-cdk/lib/init.ts
+++ b/packages/aws-cdk/lib/init.ts
@@ -7,7 +7,7 @@ import { invokeBuiltinHooks } from './init-hooks';
 import { error, info, warning } from './logging';
 import { ToolkitError } from './toolkit/error';
 import { cdkHomeDir, rootDir } from './util/directories';
-import { formatErrorMessage } from './util/error';
+import { formatErrorMessage } from './util/format-error';
 import { rangeFromSemver } from './util/version-range';
 
 /* eslint-disable @typescript-eslint/no-var-requires */ // Packages don't have @types module
diff --git a/packages/aws-cdk/lib/legacy-exports-source.ts b/packages/aws-cdk/lib/legacy-exports-source.ts
index c7c3bf043..4182ebbef 100644
--- a/packages/aws-cdk/lib/legacy-exports-source.ts
+++ b/packages/aws-cdk/lib/legacy-exports-source.ts
@@ -17,7 +17,7 @@ export { Bootstrapper } from './api/bootstrap';
 export { CloudExecutable } from './api/cxapp/cloud-executable';
 export { execProgram } from './api/cxapp/exec';
 export { RequireApproval } from './diff';
-export { leftPad } from './api/util/string-manipulation';
+export { leftPad } from './util/string-manipulation';
 export { formatAsBanner } from './cli/util/console-formatters';
 export { setSdkTracing as enableTracing } from './api/aws-auth/tracing';
 export { aliases, command, describe } from './commands/docs';
diff --git a/packages/aws-cdk/lib/notices.ts b/packages/aws-cdk/lib/notices.ts
index 3939ae5c6..ebeec4d06 100644
--- a/packages/aws-cdk/lib/notices.ts
+++ b/packages/aws-cdk/lib/notices.ts
@@ -14,7 +14,7 @@ import { ToolkitError } from './toolkit/error';
 import { loadTreeFromDir, some } from './tree';
 import { flatMap } from './util';
 import { cdkCacheDir } from './util/directories';
-import { formatErrorMessage } from './util/error';
+import { formatErrorMessage } from './util/format-error';
 
 const CACHE_FILE_PATH = path.join(cdkCacheDir(), 'notices.json');
 
diff --git a/packages/aws-cdk/lib/util/archive.ts b/packages/aws-cdk/lib/util/archive.ts
index c5f1b74b0..8e502d198 100644
--- a/packages/aws-cdk/lib/util/archive.ts
+++ b/packages/aws-cdk/lib/util/archive.ts
@@ -2,7 +2,7 @@ import { error } from 'console';
 import { createWriteStream, promises as fs } from 'fs';
 import * as path from 'path';
 import * as glob from 'glob';
-import { formatErrorMessage } from './error';
+import { formatErrorMessage } from './format-error';
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 const archiver = require('archiver');
diff --git a/packages/aws-cdk/lib/util/validate-notification-arn.ts b/packages/aws-cdk/lib/util/cloudformation.ts
similarity index 100%
rename from packages/aws-cdk/lib/util/validate-notification-arn.ts
rename to packages/aws-cdk/lib/util/cloudformation.ts
diff --git a/packages/aws-cdk/lib/util/error.ts b/packages/aws-cdk/lib/util/format-error.ts
similarity index 100%
rename from packages/aws-cdk/lib/util/error.ts
rename to packages/aws-cdk/lib/util/format-error.ts
diff --git a/packages/aws-cdk/lib/util/index.ts b/packages/aws-cdk/lib/util/index.ts
index 5597b4b21..32db74c09 100644
--- a/packages/aws-cdk/lib/util/index.ts
+++ b/packages/aws-cdk/lib/util/index.ts
@@ -1,5 +1,15 @@
+export * from './archive';
 export * from './arrays';
 export * from './bool';
+export * from './bytes';
+export * from './cloudformation';
+export * from './content-hash';
+export * from './format-error';
 export * from './objects';
+export * from './parallel';
+export * from './serialize';
+export * from './string-manipulation';
+export * from './type-brands';
 export * from './types';
-export * from './tables';
+export * from './version-range';
+export * from './yaml-cfn';
diff --git a/packages/aws-cdk/lib/serialize.ts b/packages/aws-cdk/lib/util/serialize.ts
similarity index 96%
rename from packages/aws-cdk/lib/serialize.ts
rename to packages/aws-cdk/lib/util/serialize.ts
index 7a6e83626..c46b24001 100644
--- a/packages/aws-cdk/lib/serialize.ts
+++ b/packages/aws-cdk/lib/util/serialize.ts
@@ -1,6 +1,6 @@
 import * as fs from 'fs-extra';
-import { formatBytes } from './util/bytes';
-import * as yaml_cfn from './util/yaml-cfn';
+import { formatBytes } from './bytes';
+import * as yaml_cfn from './yaml-cfn';
 
 /**
  * Stringify to YAML
diff --git a/packages/aws-cdk/lib/api/util/string-manipulation.ts b/packages/aws-cdk/lib/util/string-manipulation.ts
similarity index 100%
rename from packages/aws-cdk/lib/api/util/string-manipulation.ts
rename to packages/aws-cdk/lib/util/string-manipulation.ts
diff --git a/packages/aws-cdk/test/api/console-listener.ts b/packages/aws-cdk/test/api/_helpers/console-listener.ts
similarity index 100%
rename from packages/aws-cdk/test/api/console-listener.ts
rename to packages/aws-cdk/test/api/_helpers/console-listener.ts
diff --git a/packages/aws-cdk/test/api/fake-cloudformation-stack.ts b/packages/aws-cdk/test/api/_helpers/fake-cloudformation-stack.ts
similarity index 82%
rename from packages/aws-cdk/test/api/fake-cloudformation-stack.ts
rename to packages/aws-cdk/test/api/_helpers/fake-cloudformation-stack.ts
index cb41f5004..63c53db3b 100644
--- a/packages/aws-cdk/test/api/fake-cloudformation-stack.ts
+++ b/packages/aws-cdk/test/api/_helpers/fake-cloudformation-stack.ts
@@ -1,7 +1,7 @@
-import { ICloudFormationClient } from '../../lib/api';
-import { CloudFormationStack, Template } from '../../lib/api/deployments';
-import { StackStatus } from '../../lib/api/util/cloudformation/stack-status';
-import { MockSdk } from '../util/mock-sdk';
+import { ICloudFormationClient } from '../../../lib/api';
+import { CloudFormationStack, Template } from '../../../lib/api/deployments';
+import { StackStatus } from '../../../lib/api/stack-events';
+import { MockSdk } from '../../util/mock-sdk';
 
 export interface FakeCloudFormationStackProps {
   readonly stackName: string;
diff --git a/packages/aws-cdk/test/api/hotswap/hotswap-test-setup.ts b/packages/aws-cdk/test/api/_helpers/hotswap-test-setup.ts
similarity index 98%
rename from packages/aws-cdk/test/api/hotswap/hotswap-test-setup.ts
rename to packages/aws-cdk/test/api/_helpers/hotswap-test-setup.ts
index 6272b9f05..5ea31c57d 100644
--- a/packages/aws-cdk/test/api/hotswap/hotswap-test-setup.ts
+++ b/packages/aws-cdk/test/api/_helpers/hotswap-test-setup.ts
@@ -14,7 +14,7 @@ import {
   restoreSdkMocksToDefault,
   setDefaultSTSMocks,
 } from '../../util/mock-sdk';
-import { FakeCloudformationStack } from '../fake-cloudformation-stack';
+import { FakeCloudformationStack } from './fake-cloudformation-stack';
 
 const STACK_NAME = 'withouterrors';
 export const STACK_ID = 'stackId';
diff --git a/packages/aws-cdk/test/api/aws-auth/fake-sts.ts b/packages/aws-cdk/test/api/aws-auth/fake-sts.ts
index 3b82986c9..d93a7ff77 100644
--- a/packages/aws-cdk/test/api/aws-auth/fake-sts.ts
+++ b/packages/aws-cdk/test/api/aws-auth/fake-sts.ts
@@ -2,7 +2,7 @@ import { Tag } from '@aws-sdk/client-sts';
 import * as nock from 'nock';
 import * as uuid from 'uuid';
 import * as xmlJs from 'xml-js';
-import { formatErrorMessage } from '../../../lib/util/error';
+import { formatErrorMessage } from '../../../lib/util/format-error';
 
 interface RegisteredIdentity {
   readonly account: string;
diff --git a/packages/aws-cdk/test/api/bootstrap/bootstrap.test.ts b/packages/aws-cdk/test/api/bootstrap/bootstrap.test.ts
index 8975b75fb..6c0777dae 100644
--- a/packages/aws-cdk/test/api/bootstrap/bootstrap.test.ts
+++ b/packages/aws-cdk/test/api/bootstrap/bootstrap.test.ts
@@ -12,7 +12,7 @@ import {
 import { parse } from 'yaml';
 import { Bootstrapper } from '../../../lib/api/bootstrap';
 import { legacyBootstrapTemplate } from '../../../lib/api/bootstrap/legacy-template';
-import { deserializeStructure, serializeStructure, toYAML } from '../../../lib/serialize';
+import { deserializeStructure, serializeStructure, toYAML } from '../../../lib/util/serialize';
 import { CliIoHost } from '../../../lib/toolkit/cli-io-host';
 import { MockSdkProvider, mockCloudFormationClient, restoreSdkMocksToDefault } from '../../util/mock-sdk';
 
diff --git a/packages/aws-cdk/test/api/assembly-versions.ts b/packages/aws-cdk/test/api/cxapp/assembly-versions.ts
similarity index 95%
rename from packages/aws-cdk/test/api/assembly-versions.ts
rename to packages/aws-cdk/test/api/cxapp/assembly-versions.ts
index ae2ffe955..bea78a77f 100644
--- a/packages/aws-cdk/test/api/assembly-versions.ts
+++ b/packages/aws-cdk/test/api/cxapp/assembly-versions.ts
@@ -1,6 +1,6 @@
 import * as fs from 'fs';
 import * as cxapi from '@aws-cdk/cx-api';
-import { CloudAssembly } from '../../lib/api/cxapp/cloud-assembly';
+import { CloudAssembly } from '../../../lib/api/cxapp/cloud-assembly';
 
 /**
  * The cloud-assembly-schema in the new monorepo will use its own package version as the schema version, which is always `0.0.0` when tests are running.
diff --git a/packages/aws-cdk/test/api/cloud-assembly.test.ts b/packages/aws-cdk/test/api/cxapp/cloud-assembly.test.ts
similarity index 98%
rename from packages/aws-cdk/test/api/cloud-assembly.test.ts
rename to packages/aws-cdk/test/api/cxapp/cloud-assembly.test.ts
index 3000646a1..03daf6b9d 100644
--- a/packages/aws-cdk/test/api/cloud-assembly.test.ts
+++ b/packages/aws-cdk/test/api/cxapp/cloud-assembly.test.ts
@@ -1,7 +1,7 @@
 /* eslint-disable import/order */
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
-import { DefaultSelection } from '../../lib/api/cxapp/cloud-assembly';
-import { MockCloudExecutable } from '../util';
+import { DefaultSelection } from '../../../lib/api/cxapp/cloud-assembly';
+import { MockCloudExecutable } from '../../util';
 import { cliAssemblyWithForcedVersion } from './assembly-versions';
 
 test('select all top level stacks in the presence of nested assemblies', async () => {
diff --git a/packages/aws-cdk/test/api/cloud-executable.test.ts b/packages/aws-cdk/test/api/cxapp/cloud-executable.test.ts
similarity index 93%
rename from packages/aws-cdk/test/api/cloud-executable.test.ts
rename to packages/aws-cdk/test/api/cxapp/cloud-executable.test.ts
index 796ea7181..33f6881f4 100644
--- a/packages/aws-cdk/test/api/cloud-executable.test.ts
+++ b/packages/aws-cdk/test/api/cxapp/cloud-executable.test.ts
@@ -1,8 +1,8 @@
 /* eslint-disable import/order */
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
-import { DefaultSelection } from '../../lib/api/cxapp/cloud-assembly';
-import { registerContextProvider } from '../../lib/context-providers';
-import { MockCloudExecutable } from '../util';
+import { DefaultSelection } from '../../../lib/api/cxapp/cloud-assembly';
+import { registerContextProvider } from '../../../lib/context-providers';
+import { MockCloudExecutable } from '../../util';
 
 describe('AWS::CDK::Metadata', () => {
   test('is not generated for new frameworks', async () => {
diff --git a/packages/aws-cdk/test/api/exec.test.ts b/packages/aws-cdk/test/api/cxapp/exec.test.ts
similarity index 95%
rename from packages/aws-cdk/test/api/exec.test.ts
rename to packages/aws-cdk/test/api/cxapp/exec.test.ts
index 7c5241fd7..5eb6471e8 100644
--- a/packages/aws-cdk/test/api/exec.test.ts
+++ b/packages/aws-cdk/test/api/cxapp/exec.test.ts
@@ -6,14 +6,14 @@ import * as cdk from 'aws-cdk-lib';
 import * as semver from 'semver';
 import * as sinon from 'sinon';
 import { ImportMock } from 'ts-mock-imports';
-import { execProgram } from '../../lib/api/cxapp/exec';
-import { Configuration } from '../../lib/cli/user-configuration';
-import { testAssembly } from '../util';
-import { mockSpawn } from '../util/mock-child_process';
-import { MockSdkProvider } from '../util/mock-sdk';
-import { RWLock } from '../../lib/api/util/rwlock';
+import { execProgram } from '../../../lib/api/cxapp/exec';
+import { Configuration } from '../../../lib/cli/user-configuration';
+import { testAssembly } from '../../util';
+import { mockSpawn } from '../../util/mock-child_process';
+import { MockSdkProvider } from '../../util/mock-sdk';
+import { RWLock } from '../../../lib/api/util/rwlock';
 import { rewriteManifestVersion } from './assembly-versions';
-import { CliIoHost } from '../../lib/toolkit/cli-io-host';
+import { CliIoHost } from '../../../lib/toolkit/cli-io-host';
 
 let sdkProvider: MockSdkProvider;
 let config: Configuration;
diff --git a/packages/aws-cdk/test/api/deployments/cloudformation-deployments.test.ts b/packages/aws-cdk/test/api/deployments/cloudformation-deployments.test.ts
index 0cfaf945a..4043a7163 100644
--- a/packages/aws-cdk/test/api/deployments/cloudformation-deployments.test.ts
+++ b/packages/aws-cdk/test/api/deployments/cloudformation-deployments.test.ts
@@ -27,7 +27,7 @@ import {
   restoreSdkMocksToDefault,
   setDefaultSTSMocks,
 } from '../../util/mock-sdk';
-import { FakeCloudformationStack } from '../fake-cloudformation-stack';
+import { FakeCloudformationStack } from '../_helpers/fake-cloudformation-stack';
 
 jest.mock('../../../lib/api/deployments/deploy-stack');
 jest.mock('../../../lib/api/deployments/asset-publishing');
diff --git a/packages/aws-cdk/test/util/cloudformation.test.ts b/packages/aws-cdk/test/api/deployments/cloudformation.test.ts
similarity index 96%
rename from packages/aws-cdk/test/util/cloudformation.test.ts
rename to packages/aws-cdk/test/api/deployments/cloudformation.test.ts
index 841bba1df..47d0b4070 100644
--- a/packages/aws-cdk/test/util/cloudformation.test.ts
+++ b/packages/aws-cdk/test/api/deployments/cloudformation.test.ts
@@ -1,8 +1,8 @@
 import { SSMPARAM_NO_INVALIDATE } from '@aws-cdk/cx-api';
 import { DescribeStacksCommand, GetTemplateCommand, StackStatus } from '@aws-sdk/client-cloudformation';
-import { MockSdk, mockCloudFormationClient } from './mock-sdk';
-import type { ICloudFormationClient } from '../../lib/api/aws-auth';
-import { CloudFormationStack, TemplateParameters } from '../../lib/api/deployments';
+import { MockSdk, mockCloudFormationClient } from '../../util/mock-sdk';
+import type { ICloudFormationClient } from '../../../lib/api/aws-auth';
+import { CloudFormationStack, TemplateParameters } from '../../../lib/api/deployments';
 
 const PARAM = 'TheParameter';
 const DEFAULT = 'TheDefault';
diff --git a/packages/aws-cdk/test/api/deployments/hotswap-deployments.test.ts b/packages/aws-cdk/test/api/deployments/hotswap-deployments.test.ts
index 4ec540e8a..b43c8ca90 100644
--- a/packages/aws-cdk/test/api/deployments/hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/deployments/hotswap-deployments.test.ts
@@ -5,7 +5,7 @@ import { CfnEvaluationException } from '../../../lib/api/evaluate-cloudformation
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { MockSdk, mockCloudFormationClient, mockLambdaClient, mockStepFunctionsClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
-import * as setup from '../hotswap/hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 
 jest.mock('@aws-sdk/client-lambda', () => {
   const original = jest.requireActual('@aws-sdk/client-lambda');
diff --git a/packages/aws-cdk/test/api/garbage-collection.test.ts b/packages/aws-cdk/test/api/garbage-collection/garbage-collection.test.ts
similarity index 98%
rename from packages/aws-cdk/test/api/garbage-collection.test.ts
rename to packages/aws-cdk/test/api/garbage-collection/garbage-collection.test.ts
index d43e95828..1315721b4 100644
--- a/packages/aws-cdk/test/api/garbage-collection.test.ts
+++ b/packages/aws-cdk/test/api/garbage-collection/garbage-collection.test.ts
@@ -6,8 +6,8 @@ import {
   ListStacksCommand,
   Stack,
 } from '@aws-sdk/client-cloudformation';
-import { ECR_ISOLATED_TAG, GarbageCollector, S3_ISOLATED_TAG, ToolkitInfo } from '../../lib/api';
-import { mockBootstrapStack, mockCloudFormationClient, mockECRClient, mockS3Client, MockSdk, MockSdkProvider } from '../util/mock-sdk';
+import { ECR_ISOLATED_TAG, GarbageCollector, S3_ISOLATED_TAG, ToolkitInfo } from '../../../lib/api';
+import { mockBootstrapStack, mockCloudFormationClient, mockECRClient, mockS3Client, MockSdk, MockSdkProvider } from '../../util/mock-sdk';
 import {
   DeleteObjectsCommand,
   DeleteObjectTaggingCommand,
@@ -19,8 +19,8 @@ import {
   ActiveAssetCache,
   BackgroundStackRefresh,
   BackgroundStackRefreshProps,
-} from '../../lib/api/garbage-collection/stack-refresh';
-import { ProgressPrinter } from '../../lib/api/garbage-collection/progress-printer';
+} from '../../../lib/api/garbage-collection/stack-refresh';
+import { ProgressPrinter } from '../../../lib/api/garbage-collection/progress-printer';
 import {
   BatchDeleteImageCommand,
   BatchGetImageCommand,
@@ -28,7 +28,7 @@ import {
   ListImagesCommand,
   PutImageCommand,
 } from '@aws-sdk/client-ecr';
-import { CliIoHost } from '../../lib/toolkit/cli-io-host';
+import { CliIoHost } from '../../../lib/toolkit/cli-io-host';
 
 let garbageCollector: GarbageCollector;
 
diff --git a/packages/aws-cdk/test/api/hotswap/appsync-mapping-templates-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/appsync-mapping-templates-hotswap-deployments.test.ts
index f4c89d634..ddae8d7fd 100644
--- a/packages/aws-cdk/test/api/hotswap/appsync-mapping-templates-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/appsync-mapping-templates-hotswap-deployments.test.ts
@@ -9,7 +9,7 @@ import {
 } from '@aws-sdk/client-appsync';
 import { GetObjectCommand } from '@aws-sdk/client-s3';
 import { sdkStreamMixin } from '@smithy/util-stream';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockAppSyncClient, mockS3Client } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/code-build-projects-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/code-build-projects-hotswap-deployments.test.ts
index 42bf66af2..371d1b76f 100644
--- a/packages/aws-cdk/test/api/hotswap/code-build-projects-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/code-build-projects-hotswap-deployments.test.ts
@@ -1,5 +1,5 @@
 import { UpdateProjectCommand } from '@aws-sdk/client-codebuild';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockCodeBuildClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/ecs-services-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/ecs-services-hotswap-deployments.test.ts
index f80efa385..8ee2a4aac 100644
--- a/packages/aws-cdk/test/api/hotswap/ecs-services-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/ecs-services-hotswap-deployments.test.ts
@@ -1,5 +1,5 @@
 import { DescribeServicesCommand, RegisterTaskDefinitionCommand, UpdateServiceCommand } from '@aws-sdk/client-ecs';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { EcsHotswapProperties, HotswapMode, HotswapPropertyOverrides } from '../../../lib/api/hotswap/common';
 import { Configuration } from '../../../lib/cli/user-configuration';
 import { mockECSClient } from '../../util/mock-sdk';
diff --git a/packages/aws-cdk/test/api/hotswap/iam-policy-hotswap-deployment.test.ts b/packages/aws-cdk/test/api/hotswap/iam-policy-hotswap-deployment.test.ts
index ee454ec40..4371c4ad0 100644
--- a/packages/aws-cdk/test/api/hotswap/iam-policy-hotswap-deployment.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/iam-policy-hotswap-deployment.test.ts
@@ -1,5 +1,5 @@
 import { StackStatus } from '@aws-sdk/client-cloudformation';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { silentTest } from '../../util/silent';
 
diff --git a/packages/aws-cdk/test/api/hotswap/lambda-functions-docker-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/lambda-functions-docker-hotswap-deployments.test.ts
index 855c33f0a..df4e5c23f 100644
--- a/packages/aws-cdk/test/api/hotswap/lambda-functions-docker-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/lambda-functions-docker-hotswap-deployments.test.ts
@@ -9,7 +9,7 @@ jest.mock('@aws-sdk/client-lambda', () => {
 });
 
 import { UpdateFunctionCodeCommand, waitUntilFunctionUpdatedV2 } from '@aws-sdk/client-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockLambdaClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/lambda-functions-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/lambda-functions-hotswap-deployments.test.ts
index cf354a1aa..74906bf9c 100644
--- a/packages/aws-cdk/test/api/hotswap/lambda-functions-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/lambda-functions-hotswap-deployments.test.ts
@@ -3,7 +3,7 @@ import {
   UpdateFunctionConfigurationCommand,
   waitUntilFunctionUpdatedV2,
 } from '@aws-sdk/client-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockLambdaClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/lambda-functions-inline-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/lambda-functions-inline-hotswap-deployments.test.ts
index 7c9cfdbe3..7adc4c007 100644
--- a/packages/aws-cdk/test/api/hotswap/lambda-functions-inline-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/lambda-functions-inline-hotswap-deployments.test.ts
@@ -1,6 +1,6 @@
 import { UpdateFunctionCodeCommand } from '@aws-sdk/client-lambda';
 import { Runtime } from 'aws-cdk-lib/aws-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockLambdaClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/lambda-versions-aliases-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/lambda-versions-aliases-hotswap-deployments.test.ts
index 4356124de..5524339c7 100644
--- a/packages/aws-cdk/test/api/hotswap/lambda-versions-aliases-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/lambda-versions-aliases-hotswap-deployments.test.ts
@@ -1,5 +1,5 @@
 import { PublishVersionCommand, UpdateAliasCommand } from '@aws-sdk/client-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockLambdaClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/hotswap/nested-stacks-hotswap.test.ts b/packages/aws-cdk/test/api/hotswap/nested-stacks-hotswap.test.ts
index 37c142996..2235832a5 100644
--- a/packages/aws-cdk/test/api/hotswap/nested-stacks-hotswap.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/nested-stacks-hotswap.test.ts
@@ -1,5 +1,5 @@
 import { PublishVersionCommand, UpdateFunctionCodeCommand } from '@aws-sdk/client-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { testStack } from '../../util';
 import { mockLambdaClient } from '../../util/mock-sdk';
diff --git a/packages/aws-cdk/test/api/hotswap/s3-bucket-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/s3-bucket-hotswap-deployments.test.ts
index e27c92062..f6db9495f 100644
--- a/packages/aws-cdk/test/api/hotswap/s3-bucket-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/s3-bucket-hotswap-deployments.test.ts
@@ -1,5 +1,5 @@
 import { InvokeCommand } from '@aws-sdk/client-lambda';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { REQUIRED_BY_CFN } from '../../../lib/api/hotswap/s3-bucket-deployments';
 import { mockLambdaClient } from '../../util/mock-sdk';
diff --git a/packages/aws-cdk/test/api/hotswap/state-machine-hotswap-deployments.test.ts b/packages/aws-cdk/test/api/hotswap/state-machine-hotswap-deployments.test.ts
index bff830e00..60427a458 100644
--- a/packages/aws-cdk/test/api/hotswap/state-machine-hotswap-deployments.test.ts
+++ b/packages/aws-cdk/test/api/hotswap/state-machine-hotswap-deployments.test.ts
@@ -1,5 +1,5 @@
 import { UpdateStateMachineCommand } from '@aws-sdk/client-sfn';
-import * as setup from './hotswap-test-setup';
+import * as setup from '../_helpers/hotswap-test-setup';
 import { HotswapMode } from '../../../lib/api/hotswap/common';
 import { mockStepFunctionsClient } from '../../util/mock-sdk';
 import { silentTest } from '../../util/silent';
diff --git a/packages/aws-cdk/test/api/util/display.test.ts b/packages/aws-cdk/test/api/stack-events/display.test.ts
similarity index 93%
rename from packages/aws-cdk/test/api/util/display.test.ts
rename to packages/aws-cdk/test/api/stack-events/display.test.ts
index 2473bb891..9bd375e48 100644
--- a/packages/aws-cdk/test/api/util/display.test.ts
+++ b/packages/aws-cdk/test/api/stack-events/display.test.ts
@@ -1,6 +1,6 @@
 /* eslint-disable import/order */
-import { RewritableBlock } from '../../../lib/api/util/display';
-import { stderr } from '../console-listener';
+import { RewritableBlock } from '../../../lib/api/stack-events/display';
+import { stderr } from '../_helpers/console-listener';
 
 describe('Rewritable Block Tests', () => {
   let block: RewritableBlock;
diff --git a/packages/aws-cdk/test/api/stack-activity-monitor.test.ts b/packages/aws-cdk/test/api/stack-events/stack-activity-monitor.test.ts
similarity index 98%
rename from packages/aws-cdk/test/api/stack-activity-monitor.test.ts
rename to packages/aws-cdk/test/api/stack-events/stack-activity-monitor.test.ts
index 9bed97683..b760dda02 100644
--- a/packages/aws-cdk/test/api/stack-activity-monitor.test.ts
+++ b/packages/aws-cdk/test/api/stack-events/stack-activity-monitor.test.ts
@@ -1,9 +1,9 @@
 /* eslint-disable import/order */
 import * as chalk from 'chalk';
-import { stderr } from './console-listener';
-import { HistoryActivityPrinter } from '../../lib/api/util/cloudformation/stack-activity-monitor';
+import { stderr } from '../_helpers/console-listener';
+import { HistoryActivityPrinter } from '../../../lib/api/stack-events';
 import { ResourceStatus } from '@aws-sdk/client-cloudformation';
-import { CliIoHost } from '../../lib/toolkit/cli-io-host';
+import { CliIoHost } from '../../../lib/toolkit/cli-io-host';
 
 let TIMESTAMP: number;
 let HUMAN_TIME: string;
diff --git a/packages/aws-cdk/test/api/util/cloudformation/stack-event-poller.test.ts b/packages/aws-cdk/test/api/stack-events/stack-event-poller.test.ts
similarity index 92%
rename from packages/aws-cdk/test/api/util/cloudformation/stack-event-poller.test.ts
rename to packages/aws-cdk/test/api/stack-events/stack-event-poller.test.ts
index 6ff65e4eb..1c4abd3fd 100644
--- a/packages/aws-cdk/test/api/util/cloudformation/stack-event-poller.test.ts
+++ b/packages/aws-cdk/test/api/stack-events/stack-event-poller.test.ts
@@ -1,6 +1,6 @@
 import { DescribeStackEventsCommand, DescribeStackEventsCommandInput, StackEvent } from '@aws-sdk/client-cloudformation';
-import { StackEventPoller } from '../../../../lib/api/util/cloudformation/stack-event-poller';
-import { MockSdk, mockCloudFormationClient } from '../../../util/mock-sdk';
+import { StackEventPoller } from '../../../lib/api/stack-events';
+import { MockSdk, mockCloudFormationClient } from '../../util/mock-sdk';
 
 beforeEach(() => {
   jest.resetAllMocks();
diff --git a/packages/aws-cdk/test/util/stack-monitor.test.ts b/packages/aws-cdk/test/api/stack-events/stack-monitor.test.ts
similarity index 98%
rename from packages/aws-cdk/test/util/stack-monitor.test.ts
rename to packages/aws-cdk/test/api/stack-events/stack-monitor.test.ts
index ef01a30ad..50a8ab4df 100644
--- a/packages/aws-cdk/test/util/stack-monitor.test.ts
+++ b/packages/aws-cdk/test/api/stack-events/stack-monitor.test.ts
@@ -4,12 +4,12 @@ import {
   type StackEvent,
   StackStatus,
 } from '@aws-sdk/client-cloudformation';
-import { MockSdk, mockCloudFormationClient, restoreSdkMocksToDefault } from './mock-sdk';
+import { MockSdk, mockCloudFormationClient, restoreSdkMocksToDefault } from '../../util/mock-sdk';
 import {
   StackActivityMonitor,
   type IActivityPrinter,
   type StackActivity,
-} from '../../lib/api/util/cloudformation/stack-activity-monitor';
+} from '../../../lib/api/stack-events';
 
 let sdk: MockSdk;
 let printer: FakePrinter;
diff --git a/packages/aws-cdk/test/work-graph-builder.test.ts b/packages/aws-cdk/test/api/work-graph/work-graph-builder.test.ts
similarity index 98%
rename from packages/aws-cdk/test/work-graph-builder.test.ts
rename to packages/aws-cdk/test/api/work-graph/work-graph-builder.test.ts
index eb40873d3..6154515b1 100644
--- a/packages/aws-cdk/test/work-graph-builder.test.ts
+++ b/packages/aws-cdk/test/api/work-graph/work-graph-builder.test.ts
@@ -5,9 +5,8 @@ import * as cxapi from '@aws-cdk/cx-api';
 import { CloudAssemblyBuilder } from '@aws-cdk/cx-api';
 // eslint-disable-next-line import/no-extraneous-dependencies
 import { expect } from '@jest/globals';
-import { WorkGraph } from '../lib/util/work-graph';
-import { WorkGraphBuilder } from '../lib/util/work-graph-builder';
-import { AssetBuildNode, AssetPublishNode, StackNode, WorkNode } from '../lib/util/work-graph-types';
+import { WorkGraph, WorkGraphBuilder } from '../../../lib/api/work-graph';
+import type { AssetBuildNode, AssetPublishNode, StackNode, WorkNode } from '../../../lib/api/work-graph';
 
 let rootBuilder: CloudAssemblyBuilder;
 beforeEach(() => {
diff --git a/packages/aws-cdk/test/work-graph.test.ts b/packages/aws-cdk/test/api/work-graph/work-graph.test.ts
similarity index 99%
rename from packages/aws-cdk/test/work-graph.test.ts
rename to packages/aws-cdk/test/api/work-graph/work-graph.test.ts
index 0ac789729..301850b8d 100644
--- a/packages/aws-cdk/test/work-graph.test.ts
+++ b/packages/aws-cdk/test/api/work-graph/work-graph.test.ts
@@ -1,5 +1,5 @@
-import { WorkGraph } from '../lib/util/work-graph';
-import { AssetBuildNode, AssetPublishNode, DeploymentState, StackNode } from '../lib/util/work-graph-types';
+import { WorkGraph, DeploymentState } from '../../../lib/api/work-graph';
+import type { AssetBuildNode, AssetPublishNode, StackNode } from '../../../lib/api/work-graph';
 
 const DUMMY: any = 'DUMMY';
 
diff --git a/packages/aws-cdk/test/util/yargs-helpers.test.ts b/packages/aws-cdk/test/cli/yargs-helpers.test.ts
similarity index 100%
rename from packages/aws-cdk/test/util/yargs-helpers.test.ts
rename to packages/aws-cdk/test/cli/yargs-helpers.test.ts
diff --git a/packages/aws-cdk/test/serialize.test.ts b/packages/aws-cdk/test/serialize.test.ts
deleted file mode 100644
index e465f1c8f..000000000
--- a/packages/aws-cdk/test/serialize.test.ts
+++ /dev/null
@@ -1,36 +0,0 @@
-/* eslint-disable import/order */
-import { toYAML, obscureTemplate } from '../lib/serialize';
-
-describe(toYAML, () => {
-  test('does not wrap lines', () => {
-    const longString = 'Long string is long!'.repeat(1_024);
-    expect(toYAML({ longString })).toEqual(`longString: ${longString}\n`);
-  });
-});
-
-describe(obscureTemplate, () => {
-  test('removes CheckBootstrapVersion rule only', () => {
-    const template = {
-      Rules: {
-        CheckBootstrapVersion: { Assertions: [{ AssertDescription: 'bootstrap' }] },
-        MyOtherRule: { Assertions: [{ AssertDescription: 'other' }] },
-      },
-    };
-
-    const obscured = obscureTemplate(template);
-    expect(obscured).not.toHaveProperty('Rules.CheckBootstrapVersion');
-    expect(obscured).toHaveProperty('Rules.MyOtherRule.Assertions.0.AssertDescription', 'other');
-  });
-
-  test('removes all rules when CheckBootstrapVersion is the only rule', () => {
-    const template = {
-      Rules: {
-        CheckBootstrapVersion: { Assertions: [{ AssertDescription: 'bootstrap' }] },
-      },
-    };
-
-    const obscured = obscureTemplate(template);
-    expect(obscured).not.toHaveProperty('Rules.CheckBootstrapVersion');
-    expect(obscured).not.toHaveProperty('Rules');
-  });
-});
diff --git a/packages/aws-cdk/test/util.ts b/packages/aws-cdk/test/util.ts
index b9552bf77..3b23cdaa4 100644
--- a/packages/aws-cdk/test/util.ts
+++ b/packages/aws-cdk/test/util.ts
@@ -2,7 +2,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import { ArtifactMetadataEntryType, ArtifactType, type AssetManifest, type AssetMetadataEntry, type AwsCloudFormationStackProperties, type MetadataEntry, type MissingContext } from '@aws-cdk/cloud-assembly-schema';
 import { type CloudAssembly, CloudAssemblyBuilder, type CloudFormationStackArtifact, type StackMetadata } from '@aws-cdk/cx-api';
-import { cxapiAssemblyWithForcedVersion } from './api/assembly-versions';
+import { cxapiAssemblyWithForcedVersion } from './api/cxapp/assembly-versions';
 import { MockSdkProvider } from './util/mock-sdk';
 import { CloudExecutable } from '../lib/api/cxapp/cloud-executable';
 import { Configuration } from '../lib/cli/user-configuration';
diff --git a/packages/aws-cdk/test/api/util/error.test.ts b/packages/aws-cdk/test/util/error.test.ts
similarity index 92%
rename from packages/aws-cdk/test/api/util/error.test.ts
rename to packages/aws-cdk/test/util/error.test.ts
index 2454e74c6..3735357fc 100644
--- a/packages/aws-cdk/test/api/util/error.test.ts
+++ b/packages/aws-cdk/test/util/error.test.ts
@@ -1,4 +1,4 @@
-import { formatErrorMessage } from '../../../lib/util/error';
+import { formatErrorMessage } from '../../lib/util/format-error';
 
 describe('formatErrorMessage', () => {
   test('should return the formatted message for a regular Error object', () => {
diff --git a/packages/aws-cdk/test/util/serialize.test.ts b/packages/aws-cdk/test/util/serialize.test.ts
index 65eab98b0..a5b605c21 100644
--- a/packages/aws-cdk/test/util/serialize.test.ts
+++ b/packages/aws-cdk/test/util/serialize.test.ts
@@ -1,7 +1,41 @@
-import { replacerBufferWithInfo } from '../../lib/serialize';
+import { toYAML, obscureTemplate, replacerBufferWithInfo } from '../../lib/util/serialize';
 
+describe(toYAML, () => {
+  test('does not wrap lines', () => {
+    const longString = 'Long string is long!'.repeat(1_024);
+    expect(toYAML({ longString })).toEqual(`longString: ${longString}\n`);
+  });
+});
+
+describe(obscureTemplate, () => {
+  test('removes CheckBootstrapVersion rule only', () => {
+    const template = {
+      Rules: {
+        CheckBootstrapVersion: { Assertions: [{ AssertDescription: 'bootstrap' }] },
+        MyOtherRule: { Assertions: [{ AssertDescription: 'other' }] },
+      },
+    };
+
+    const obscured = obscureTemplate(template);
+    expect(obscured).not.toHaveProperty('Rules.CheckBootstrapVersion');
+    expect(obscured).toHaveProperty('Rules.MyOtherRule.Assertions.0.AssertDescription', 'other');
+  });
+
+  test('removes all rules when CheckBootstrapVersion is the only rule', () => {
+    const template = {
+      Rules: {
+        CheckBootstrapVersion: { Assertions: [{ AssertDescription: 'bootstrap' }] },
+      },
+    };
+
+    const obscured = obscureTemplate(template);
+    expect(obscured).not.toHaveProperty('Rules.CheckBootstrapVersion');
+    expect(obscured).not.toHaveProperty('Rules');
+  });
+});
 test('converts buffer to information', () => {
   const res = JSON.stringify({ data: Buffer.from('test data') }, replacerBufferWithInfo);
 
   expect(res).toEqual('{"data":"<Buffer: 9 Bytes>"}');
 });
+
diff --git a/packages/aws-cdk/test/util/validate-notification-arn.test.ts b/packages/aws-cdk/test/util/validate-notification-arn.test.ts
index d418546ed..d8bd5b3f7 100644
--- a/packages/aws-cdk/test/util/validate-notification-arn.test.ts
+++ b/packages/aws-cdk/test/util/validate-notification-arn.test.ts
@@ -1,5 +1,5 @@
 /* eslint-disable import/order */
-import { validateSnsTopicArn } from '../../lib/util/validate-notification-arn';
+import { validateSnsTopicArn } from '../../lib/util/cloudformation';
 
 describe('validate sns arns', () => {
   test('empty string', () => {
diff --git a/packages/aws-cdk/test/yaml.test.ts b/packages/aws-cdk/test/util/yaml.test.ts
similarity index 96%
rename from packages/aws-cdk/test/yaml.test.ts
rename to packages/aws-cdk/test/util/yaml.test.ts
index f7cfc8fd7..33a7b66c7 100644
--- a/packages/aws-cdk/test/yaml.test.ts
+++ b/packages/aws-cdk/test/util/yaml.test.ts
@@ -1,5 +1,5 @@
 /* eslint-disable import/order */
-import { deserializeStructure, toYAML } from '../lib/serialize';
+import { deserializeStructure, toYAML } from '../../lib/util/serialize';
 
 // Preferred quote of the YAML library
 const q = '"';