diff --git a/tools/@aws-cdk/spec2cdk/lib/cdk/ast.ts b/tools/@aws-cdk/spec2cdk/lib/cdk/ast.ts
index 035b8548c2688..51e7484b39b18 100644
--- a/tools/@aws-cdk/spec2cdk/lib/cdk/ast.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/cdk/ast.ts
@@ -1,3 +1,4 @@
+/* eslint-disable @cdklabs/no-throw-default-error */
 import { SpecDatabase, Resource, Service } from '@aws-cdk/service-spec-types';
 import { Module } from '@cdklabs/typewriter';
 import { AugmentationsModule } from './augmentation-generator';
@@ -5,32 +6,9 @@ import { CannedMetricsModule } from './canned-metrics';
 import { CDK_CORE, CONSTRUCTS, ModuleImportLocations } from './cdk';
 import { SelectiveImport } from './relationship-decider';
 import { ResourceClass } from './resource-class';
+import { FilePatternValues, IWriter, substituteFilePattern } from '../util';
 
-/**
- * A module containing a single resource
- */
-export class ResourceModule extends Module {
-  public constructor(public readonly service: string, public readonly resource: string) {
-    super(`@aws-cdk/${service}/${resource}-l1`);
-  }
-}
-
-/**
- * A module containing a service
- */
-export class ServiceModule extends Module {
-  public constructor(public readonly service: string, public readonly shortName: string) {
-    super(`@aws-cdk/${service}`);
-  }
-}
-
-export interface AstBuilderProps {
-  readonly db: SpecDatabase;
-  /**
-   * Override the locations modules are imported from
-   */
-  readonly importLocations?: ModuleImportLocations;
-
+export interface AddServiceProps {
   /**
    * Append a suffix at the end of generated names.
    */
@@ -42,82 +20,133 @@ export interface AstBuilderProps {
    * @default - not deprecated
    */
   readonly deprecated?: string;
-}
 
-export class AstBuilder<T extends Module> {
   /**
-   * Build a module for all resources in a service
+   * The target submodule we want to generate these resources into
+   *
+   * Practically, only used to render CloudFormation resources into the `core` module, and as a failed
+   * experiment to emit `aws-kinesisanalyticsv2` into `aws-kinesisanalytics`.
    */
-  public static forService(service: Service, props: AstBuilderProps): AstBuilder<ServiceModule> {
-    const scope = new ServiceModule(service.name, service.shortName);
-    const aug = new AugmentationsModule(props.db, service.name, props.importLocations?.cloudwatch);
-    const metrics = CannedMetricsModule.forService(props.db, service);
+  readonly destinationSubmodule?: string;
 
-    const ast = new AstBuilder(scope, props, aug, metrics);
+  /**
+   * Override the locations modules are imported from
+   */
+  readonly importLocations?: ModuleImportLocations;
+}
 
-    const resources = props.db.follow('hasResource', service);
+export interface AstBuilderProps {
+  readonly db: SpecDatabase;
 
-    for (const link of resources) {
-      ast.addResource(link.entity);
-    }
-    ast.renderImports();
-    return ast;
-  }
+  readonly modulesRoot?: string;
+
+  readonly filePatterns?: Partial<GenerateFilePatterns>;
+}
 
+export interface GenerateFilePatterns {
   /**
-   * Build an module for a single resource
+   * The pattern used to name resource files.
+   * @default "%serviceName%/%serviceShortName%.generated.ts"
    */
-  public static forResource(resource: Resource, props: AstBuilderProps): AstBuilder<ResourceModule> {
-    const parts = resource.cloudFormationType.toLowerCase().split('::');
-    const scope = new ResourceModule(parts[1], parts[2]);
-    const aug = new AugmentationsModule(props.db, parts[1], props.importLocations?.cloudwatch);
-    const metrics = CannedMetricsModule.forResource(props.db, resource);
+  readonly resources: string;
 
-    const ast = new AstBuilder(scope, props, aug, metrics);
-    ast.addResource(resource);
-    ast.renderImports();
-
-    return ast;
-  }
+  /**
+   * The pattern used to name augmentations.
+   * @default "%serviceName%/%serviceShortName%-augmentations.generated.ts"
+   */
+  readonly augmentations: string;
 
-  public readonly db: SpecDatabase;
   /**
-   * Map of CloudFormation resource name to generated class name
+   * The pattern used to name canned metrics.
+   * @default "%serviceName%/%serviceShortName%-canned-metrics.generated.ts"
    */
-  public readonly resources: Record<string, string> = {};
-  private nameSuffix?: string;
-  private deprecated?: string;
+  readonly cannedMetrics: string;
+}
+
+export function makeNames(patterns: GenerateFilePatterns, values: FilePatternValues): { [k in keyof GenerateFilePatterns]: string } {
+  return Object.fromEntries(Object.entries(patterns)
+    .map(([name, pattern]) => [name, substituteFilePattern(pattern, values)] as const)) as any;
+}
+
+export const DEFAULT_FILE_PATTERNS: GenerateFilePatterns = {
+  resources: '%moduleName%/%serviceShortName%.generated.ts',
+  augmentations: '%moduleName%/%serviceShortName%-augmentations.generated.ts',
+  cannedMetrics: '%moduleName%/%serviceShortName%-canned-metrics.generated.ts',
+};
+
+export class AstBuilder {
+  public readonly db: SpecDatabase;
+  public readonly modules = new Map<string, Module>();
+
   public readonly selectiveImports = new Array<SelectiveImport>();
+
+  public readonly serviceModules = new Map<string, SubmoduleInfo>();
   private readonly modulesRootLocation: string;
+  private readonly filePatterns: GenerateFilePatterns;
 
-  protected constructor(
-    public readonly module: T,
+  constructor(
     props: AstBuilderProps,
-    public readonly augmentations?: AugmentationsModule,
-    public readonly cannedMetrics?: CannedMetricsModule,
   ) {
     this.db = props.db;
-    this.nameSuffix = props.nameSuffix;
-    this.deprecated = props.deprecated;
-    this.modulesRootLocation = props.importLocations?.modulesRoot ?? '../..';
-
-    CDK_CORE.import(this.module, 'cdk', { fromLocation: props.importLocations?.core });
-    CONSTRUCTS.import(this.module, 'constructs');
-    CDK_CORE.helpers.import(this.module, 'cfn_parse', { fromLocation: props.importLocations?.coreHelpers });
-    CDK_CORE.errors.import(this.module, 'cdk_errors', { fromLocation: props.importLocations?.coreErrors });
+    this.modulesRootLocation = props.modulesRoot ?? '../..';
+    this.filePatterns = {
+      ...DEFAULT_FILE_PATTERNS,
+      ...noUndefined(props?.filePatterns ?? {}),
+    };
+  }
+
+  /**
+   * Add all resources in a service
+   */
+  public addService(service: Service, props?: AddServiceProps) {
+    const resources = this.db.follow('hasResource', service);
+    // Sometimes we emit multiple services into the same submodule
+    // (aws-kinesisanalyticsv2 gets emitted into aws-kinesisanalytics with a
+    // suffix. This was a failed experiment we still need to maintain.)
+    const submod = this.createSubmodule(service, props?.destinationSubmodule, props?.importLocations);
+
+    for (const { entity: resource } of resources) {
+      this.addResourceToSubmodule(submod, resource, props);
+    }
+
+    this.renderImports(submod);
+    return submod;
   }
 
-  public addResource(resource: Resource) {
-    const resourceClass = new ResourceClass(this.module, this.db, resource, {
-      suffix: this.nameSuffix,
-      deprecated: this.deprecated,
+  /**
+   * Build an module for a single resource (only used for testing)
+   */
+  public addResource(resource: Resource, props?: AddServiceProps) {
+    const service = this.db.incoming('hasResource', resource).only().entity;
+    const submod = this.createSubmodule(service, props?.destinationSubmodule, props?.importLocations);
+
+    this.addResourceToSubmodule(submod, resource, props);
+
+    this.renderImports(submod);
+    return submod;
+  }
+
+  public writeAll(writer: IWriter) {
+    for (const [fileName, module] of this.modules.entries()) {
+      if (shouldRender(module)) {
+        writer.write(module, fileName);
+      }
+    }
+  }
+
+  private addResourceToSubmodule(submodule: SubmoduleInfo, resource: Resource, props?: AddServiceProps) {
+    const resourceModule = submodule.resourcesMod.module;
+
+    const resourceClass = new ResourceClass(resourceModule, this.db, resource, {
+      suffix: props?.nameSuffix,
+      deprecated: props?.deprecated,
     });
-    this.resources[resource.cloudFormationType] = resourceClass.spec.name;
+    submodule.resources[resource.cloudFormationType] = resourceClass.spec.name;
 
     resourceClass.build();
 
     this.addImports(resourceClass);
-    this.augmentations?.augmentResource(resource, resourceClass);
+    submodule.augmentations.module.augmentResource(resource, resourceClass);
   }
 
   private addImports(resourceClass: ResourceClass) {
@@ -140,11 +169,124 @@ export class AstBuilder<T extends Module> {
     }
   }
 
-  public renderImports() {
+  private renderImports(serviceModules: SubmoduleInfo) {
     const sortedImports = this.selectiveImports.sort((a, b) => a.moduleName.localeCompare(b.moduleName));
     for (const selectiveImport of sortedImports) {
       const sourceModule = new Module(selectiveImport.moduleName);
-      sourceModule.importSelective(this.module, selectiveImport.types.map((t) => `${t.originalType} as ${t.aliasedType}`), { fromLocation: `${this.modulesRootLocation}/${sourceModule.name}` });
+      sourceModule.importSelective(serviceModules.resourcesMod.module, selectiveImport.types.map((t) => `${t.originalType} as ${t.aliasedType}`), {
+        fromLocation: `${this.modulesRootLocation}/${sourceModule.name}`,
+      });
+    }
+  }
+
+  private createSubmodule(service: Service, targetSubmodule?: string, importLocations?: ModuleImportLocations): SubmoduleInfo {
+    const submoduleName = targetSubmodule ?? service.name;
+    const key = `${submoduleName}/${service.name}`;
+
+    const submod = this.serviceModules.get(key);
+    if (submod) {
+      return submod;
     }
+
+    // ResourceModule and AugmentationsModule starts out empty and needs to be filled on a resource-by-resource basis
+    const names = makeNames(this.filePatterns, { moduleName: submoduleName, serviceShortName: service.shortName });
+    const resourcesMod = this.rememberModule(this.createResourceModule(submoduleName, service.name, importLocations), names.resources);
+    const augmentations = this.rememberModule(
+      new AugmentationsModule(this.db, service.shortName, importLocations?.cloudwatch),
+      names.augmentations,
+    );
+
+    // CannedMetricsModule fill themselves upon construction
+    const cannedMetrics = this.rememberModule(CannedMetricsModule.forService(this.db, service), names.cannedMetrics);
+
+    const ret: SubmoduleInfo = {
+      service,
+      submoduleName: submoduleName,
+      resourcesMod,
+      augmentations,
+      cannedMetrics,
+      resources: {},
+    };
+
+    this.serviceModules.set(key, ret);
+    return ret;
   }
+
+  private createResourceModule(moduleName: string, serviceName: string, importLocations?: ModuleImportLocations) {
+    const resourceModule = new Module(`@aws-cdk/${moduleName}/${serviceName}`);
+    CDK_CORE.import(resourceModule, 'cdk', { fromLocation: importLocations?.core });
+    CONSTRUCTS.import(resourceModule, 'constructs');
+    CDK_CORE.helpers.import(resourceModule, 'cfn_parse', { fromLocation: importLocations?.coreHelpers });
+    CDK_CORE.errors.import(resourceModule, 'cdk_errors', { fromLocation: importLocations?.coreErrors });
+    return resourceModule;
+  }
+
+  public module(key: string) {
+    const ret = this.modules.get(key);
+    if (!ret) {
+      throw new Error(`No such module: ${key}`);
+    }
+    return ret;
+  }
+
+  private rememberModule<M extends Module>(
+    module: M,
+    filePath: string,
+  ): LocatedModule<M> {
+    if (this.modules.has(filePath)) {
+      throw new Error(`Duplicate module key: ${filePath}`);
+    }
+    this.modules.set(filePath, module);
+
+    return { module, filePath };
+  }
+}
+
+/**
+ * Bookkeeping around submodules, mostly used to report on what the generator did
+ *
+ * (This will be used by cfn2ts later to generate all kinds of codegen metadata)
+ */
+export interface SubmoduleInfo {
+  /**
+   * The name of the submodule of aws-cdk-lib where these service resources got written
+   */
+  readonly submoduleName: string;
+
+  readonly service: Service;
+
+  readonly resourcesMod: LocatedModule<Module>;
+  readonly augmentations: LocatedModule<AugmentationsModule>;
+  readonly cannedMetrics: LocatedModule<CannedMetricsModule>;
+
+  /**
+   * Map of CloudFormation resource name to generated class name
+   */
+  readonly resources: Record<string, string>;
+}
+
+interface LocatedModule<T extends Module> {
+  readonly module: T;
+  readonly filePath: string;
+}
+
+function noUndefined<A extends object>(x: A | undefined): A | undefined {
+  if (!x) {
+    return undefined;
+  }
+  return Object.fromEntries(Object.entries(x).filter(([, v]) => v !== undefined)) as any;
+}
+
+export function submoduleFiles(x: SubmoduleInfo): string[] {
+  const ret = [];
+  for (const mod of [x.resourcesMod, x.augmentations, x.cannedMetrics]) {
+    if (shouldRender(mod.module)) {
+      ret.push(mod.filePath);
+    }
+  }
+  return ret;
+}
+
+function shouldRender(m: Module) {
+  return m.types.length > 0 || m.initialization.length > 0;
 }
diff --git a/tools/@aws-cdk/spec2cdk/lib/cdk/canned-metrics.ts b/tools/@aws-cdk/spec2cdk/lib/cdk/canned-metrics.ts
index 9a87c2ceed871..0d61673ce4dee 100644
--- a/tools/@aws-cdk/spec2cdk/lib/cdk/canned-metrics.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/cdk/canned-metrics.ts
@@ -36,14 +36,13 @@ export class CannedMetricsModule extends Module {
 
   private metrics: Record<string, MetricsClass> = {};
   private _hasCannedMetrics: boolean = false;
+  private _returnType: MetricsReturnType | undefined;
 
   private constructor(private readonly db: SpecDatabase, service: Service, namespaces: string[]) {
     super(`${service.name}.canned-metrics`);
 
-    const returnType = new MetricsReturnType(this);
-
     for (const namespace of namespaces) {
-      this.metrics[namespace] = new MetricsClass(this, namespace, returnType);
+      this.metrics[namespace] = new MetricsClass(this, namespace, this.returnType());
     }
   }
 
@@ -59,6 +58,18 @@ export class CannedMetricsModule extends Module {
     const dimensions = this.db.follow('usesDimensionSet', metric).map((m) => m.entity);
     this.metrics[metric.namespace].addMetricWithDimensions(metric, dimensions);
   }
+
+  /**
+   * Create and return the ReturnType class
+   *
+   * Do this only once, and lazily so we don't generate the type if it goes unused.
+   */
+  private returnType() {
+    if (!this._returnType) {
+      this._returnType = new MetricsReturnType(this);
+    }
+    return this._returnType;
+  }
 }
 
 export class MetricsReturnType extends InterfaceType {
diff --git a/tools/@aws-cdk/spec2cdk/lib/cfn2ts/index.ts b/tools/@aws-cdk/spec2cdk/lib/cfn2ts/index.ts
index 1fed27e369b0e..21ea09397aa72 100644
--- a/tools/@aws-cdk/spec2cdk/lib/cfn2ts/index.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/cfn2ts/index.ts
@@ -1,7 +1,6 @@
 import { loadAwsServiceSpec } from '@aws-cdk/aws-service-spec';
 import { Service } from '@aws-cdk/service-spec-types';
 import * as fs from 'fs-extra';
-import * as pLimit from 'p-limit';
 import * as pkglint from './pkglint';
 import { CodeGeneratorOptions, GenerateAllOptions, ModuleMap, ModuleMapScope } from './types';
 import type { ModuleImportLocations } from '../cdk/cdk';
@@ -10,11 +9,6 @@ import { log } from '../util';
 
 export * from './types';
 
-interface GenerateOutput {
-  outputFiles: string[];
-  resources: Record<string, string>;
-}
-
 let serviceCache: Service[];
 
 async function getAllScopes(field: keyof Service = 'name'): Promise<ModuleMapScope[]> {
@@ -30,7 +24,7 @@ export default async function generate(
   scopes: string | string[],
   outPath: string,
   options: CodeGeneratorOptions = {},
-): Promise<GenerateOutput> {
+): Promise<void> {
   const coreImport = options.coreImport ?? 'aws-cdk-lib';
   let moduleScopes: ModuleMapScope[] = [];
   if (scopes === '*') {
@@ -40,7 +34,7 @@ export default async function generate(
   }
 
   log.info(`cfn-resources: ${moduleScopes.map(s => s.namespace).join(', ')}`);
-  const generated = await generateModules(
+  await generateModules(
     {
       'aws-cdk-lib': {
         services: options.autoGenerateSuffixes ? computeServiceSuffixes(moduleScopes) : moduleScopes,
@@ -50,9 +44,9 @@ export default async function generate(
       outputPath: outPath ?? 'lib',
       clearOutput: false,
       filePatterns: {
-        resources: ({ serviceShortName }) => `${serviceShortName}.generated.ts`,
-        augmentations: ({ serviceShortName }) => `${serviceShortName}-augmentations.generated.ts`,
-        cannedMetrics: ({ serviceShortName }) => `${serviceShortName}-canned-metrics.generated.ts`,
+        resources: '%serviceShortName%.generated.ts',
+        augmentations: '%serviceShortName%-augmentations.generated.ts',
+        cannedMetrics: '%serviceShortName%-canned-metrics.generated.ts',
       },
       importLocations: {
         core: coreImport,
@@ -61,8 +55,6 @@ export default async function generate(
       },
     },
   );
-
-  return generated;
 }
 
 /**
@@ -163,9 +155,9 @@ export async function generateAll(
       outputPath: outPath,
       clearOutput: false,
       filePatterns: {
-        resources: ({ moduleName: m, serviceShortName: s }) => `${m}/lib/${s}.generated.ts`,
-        augmentations: ({ moduleName: m, serviceShortName: s }) => `${m}/lib/${s}-augmentations.generated.ts`,
-        cannedMetrics: ({ moduleName: m, serviceShortName: s }) => `${m}/lib/${s}-canned-metrics.generated.ts`,
+        resources: '%moduleName%/lib/%serviceShortName%.generated.ts',
+        augmentations: '%moduleName%/lib/%serviceShortName%-augmentations.generated.ts',
+        cannedMetrics: '%moduleName%/lib/%serviceShortName%-canned-metrics.generated.ts',
       },
       importLocations: {
         core: options.coreImport,
@@ -176,13 +168,11 @@ export async function generateAll(
     },
   );
 
-  const limit = pLimit(20);
-  // eslint-disable-next-line @cdklabs/promiseall-no-unbounded-parallelism
-  await Promise.all(Object.keys(moduleMap).map((moduleName) => limit(async () => {
+  Object.keys(moduleMap).forEach((moduleName) => {
     // Add generated resources and files to module in map
     moduleMap[moduleName].resources = generated.modules[moduleName].map((m) => m.resources).reduce(mergeObjects, {});
     moduleMap[moduleName].files = generated.modules[moduleName].flatMap((m) => m.outputFiles);
-  })));
+  });
 
   return moduleMap;
 }
diff --git a/tools/@aws-cdk/spec2cdk/lib/cli/cli.ts b/tools/@aws-cdk/spec2cdk/lib/cli/cli.ts
index ed9b451b94274..93c146e7b5409 100644
--- a/tools/@aws-cdk/spec2cdk/lib/cli/cli.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/cli/cli.ts
@@ -1,8 +1,8 @@
 import * as path from 'node:path';
 import { parseArgs } from 'node:util';
 import { PositionalArg, showHelp } from './help';
-import { GenerateModuleMap, PatternKeys, generate, generateAll } from '../generate';
-import { log, parsePattern } from '../util';
+import { GenerateModuleMap, GenerateOptions, generate, generateAll } from '../generate';
+import { log } from '../util';
 
 const command = 'spec2cdk';
 const args: PositionalArg[] = [{
@@ -22,17 +22,14 @@ const config = {
   },
   'pattern': {
     type: 'string',
-    default: '%moduleName%/%serviceShortName%.generated.ts',
     description: 'File and path pattern for generated files',
   },
   'augmentations': {
     type: 'string',
-    default: '%moduleName%/%serviceShortName%-augmentations.generated.ts',
     description: 'File and path pattern for generated augmentations files',
   },
   'metrics': {
     type: 'string',
-    default: '%moduleName%/%serviceShortName%-canned-metrics.generated.ts',
     description: 'File and path pattern for generated canned metrics files ',
   },
   'service': {
@@ -89,30 +86,13 @@ export async function main(argv: string[]) {
     throw new EvalError('Please specify the output-path');
   }
 
-  const pss: Record<PatternKeys, true> = { moduleName: true, serviceName: true, serviceShortName: true };
-
   const outputPath = outputDir ?? path.join(__dirname, '..', 'services');
-  const resourceFilePattern = parsePattern(
-    stringOr(options.pattern, path.join('%moduleName%', '%serviceShortName%.generated.ts')),
-    pss,
-  );
-
-  const augmentationsFilePattern = parsePattern(
-    stringOr(options.augmentations, path.join('%moduleName%', '%serviceShortName%-augmentations.generated.ts')),
-    pss,
-  );
-
-  const cannedMetricsFilePattern = parsePattern(
-    stringOr(options.metrics, path.join('%moduleName%', '%serviceShortName%-canned-metrics.generated.ts')),
-    pss,
-  );
-
-  const generatorOptions = {
+  const generatorOptions: GenerateOptions = {
     outputPath,
     filePatterns: {
-      resources: resourceFilePattern,
-      augmentations: augmentationsFilePattern,
-      cannedMetrics: cannedMetricsFilePattern,
+      resources: options.pattern,
+      augmentations: options.augmentations,
+      cannedMetrics: options.metrics,
     },
     clearOutput: options['clear-output'],
     augmentationsSupport: options['augmentations-support'],
@@ -133,14 +113,3 @@ export async function main(argv: string[]) {
 
   await generateAll(generatorOptions);
 }
-
-function stringOr(pat: unknown, def: string) {
-  if (!pat) {
-    return def;
-  }
-  if (typeof pat !== 'string') {
-    // eslint-disable-next-line @cdklabs/no-throw-default-error
-    throw new Error(`Expected string, got: ${JSON.stringify(pat)}`);
-  }
-  return pat;
-}
diff --git a/tools/@aws-cdk/spec2cdk/lib/generate.ts b/tools/@aws-cdk/spec2cdk/lib/generate.ts
index f68d6ef3cadfb..191944f02fa3b 100644
--- a/tools/@aws-cdk/spec2cdk/lib/generate.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/generate.ts
@@ -2,13 +2,11 @@ import * as path from 'path';
 import { loadAwsServiceSpec } from '@aws-cdk/aws-service-spec';
 import { DatabaseBuilder } from '@aws-cdk/service-spec-importers';
 import { SpecDatabase } from '@aws-cdk/service-spec-types';
-import { TypeScriptRenderer } from '@cdklabs/typewriter';
+import { Module, TypeScriptRenderer } from '@cdklabs/typewriter';
 import * as fs from 'fs-extra';
-import { AstBuilder, ServiceModule } from './cdk/ast';
+import { AstBuilder, DEFAULT_FILE_PATTERNS, GenerateFilePatterns, submoduleFiles } from './cdk/ast';
 import { ModuleImportLocations } from './cdk/cdk';
-import { queryDb, log, PatternedString, TsFileWriter } from './util';
-
-export type PatternKeys = 'moduleName' | 'serviceName' | 'serviceShortName';
+import { queryDb, log, TsFileWriter } from './util';
 
 export interface GenerateServiceRequest {
   /**
@@ -49,26 +47,6 @@ export interface GenerateModuleOptions {
   readonly moduleImportLocations?: ModuleImportLocations;
 }
 
-export interface GenerateFilePatterns {
-  /**
-   * The pattern used to name resource files.
-   * @default "%module.name%/%service.short%.generated.ts"
-   */
-  readonly resources?: PatternedString<PatternKeys>;
-
-  /**
-   * The pattern used to name augmentations.
-   * @default "%module.name%/%service.short%-augmentations.generated.ts"
-   */
-  readonly augmentations?: PatternedString<PatternKeys>;
-
-  /**
-   * The pattern used to name canned metrics.
-   * @default "%module.name%/%service.short%-canned-metrics.generated.ts"
-   */
-  readonly cannedMetrics?: PatternedString<PatternKeys>;
-}
-
 export interface GenerateOptions {
   /**
    * Default location for module imports
@@ -78,7 +56,7 @@ export interface GenerateOptions {
   /**
    * Configure where files are created exactly
    */
-  readonly filePatterns?: GenerateFilePatterns;
+  readonly filePatterns?: Partial<GenerateFilePatterns>;
 
   /**
    * Base path for generated files
@@ -118,9 +96,9 @@ export interface GenerateOutput {
   resources: Record<string, string>;
   modules: {
     [name: string]: Array<{
-      module: AstBuilder<ServiceModule>;
+      module: Module;
       options: GenerateModuleOptions;
-      resources: AstBuilder<ServiceModule>['resources'];
+      resources: Record<string, string>;
       outputFiles: string[];
     }>;
   };
@@ -163,7 +141,7 @@ export async function generateAll(options: GenerateOptions) {
     };
   }
 
-  return generator(db, modules, options);
+  await generator(db, modules, options);
 }
 
 function enableDebug(options: GenerateOptions) {
@@ -180,8 +158,7 @@ async function generator(
   const timeLabel = '🐢  Completed in';
   log.time(timeLabel);
   log.debug('Options', options);
-  const { augmentationsSupport, clearOutput, outputPath = process.cwd() } = options;
-  const filePatterns = ensureFilePatterns(options.filePatterns);
+  const { clearOutput, outputPath = process.cwd() } = options;
 
   const renderer = new TypeScriptRenderer();
 
@@ -193,57 +170,46 @@ async function generator(
     fs.removeSync(outputPath);
   }
 
+  const ast = new AstBuilder({
+    db,
+    modulesRoot: options.importLocations?.modulesRoot,
+    filePatterns: {
+      ...DEFAULT_FILE_PATTERNS,
+      ...noUndefined(options.filePatterns),
+    },
+  });
+
   // Go through the module map
   log.info('Generating %i modules...', Object.keys(modules).length);
   for (const [moduleName, moduleOptions] of Object.entries(modules)) {
-    const { moduleImportLocations: importLocations = options.importLocations, services } = moduleOptions;
-    moduleMap[moduleName] = queryDb.getServicesByGenerateServiceRequest(db, services).map(([req, s]) => {
+    const services = queryDb.getServicesByGenerateServiceRequest(db, moduleOptions.services);
+
+    moduleMap[moduleName] = services.map(([req, s]) => {
       log.debug(moduleName, s.name, 'ast');
-      const ast = AstBuilder.forService(s, {
-        db,
-        importLocations,
+
+      const submod = ast.addService(s, {
+        destinationSubmodule: moduleName,
         nameSuffix: req.suffix,
         deprecated: req.deprecated,
+        importLocations: moduleOptions.moduleImportLocations ?? options.importLocations,
       });
 
-      log.debug(moduleName, s.name, 'render');
-      const writer = new TsFileWriter(outputPath, renderer, {
-        ['moduleName']: moduleName,
-        ['serviceName']: ast.module.service.toLowerCase(),
-        ['serviceShortName']: ast.module.shortName.toLowerCase(),
-      });
-
-      // Resources
-      writer.write(ast.module, filePatterns.resources);
-
-      if (ast.augmentations?.hasAugmentations) {
-        const augFile = writer.write(ast.augmentations, filePatterns.augmentations);
-
-        if (augmentationsSupport) {
-          const augDir = path.dirname(augFile);
-          for (const supportMod of ast.augmentations.supportModules) {
-            writer.write(supportMod, path.resolve(augDir, `${supportMod.importName}.ts`));
-          }
-        }
-      }
-
-      if (ast.cannedMetrics?.hasCannedMetrics) {
-        writer.write(ast.cannedMetrics, filePatterns.cannedMetrics);
-      }
-
       return {
-        module: ast,
+        module: submod.resourcesMod.module,
         options: moduleOptions,
-        resources: ast.resources,
-        outputFiles: writer.outputFiles,
-      };
+        resources: submod.resources,
+        outputFiles: submoduleFiles(submod).map((x) => path.resolve(x)),
+      } satisfies GenerateOutput['modules'][string][number];
     });
   }
 
-  const result = {
+  const writer = new TsFileWriter(outputPath, renderer);
+  ast.writeAll(writer);
+
+  const result: GenerateOutput = {
     modules: moduleMap,
     resources: Object.values(moduleMap).flat().map(pick('resources')).reduce(mergeObjects, {}),
-    outputFiles: Object.values(moduleMap).flat().flatMap(pick('outputFiles')),
+    outputFiles: writer.outputFiles,
   };
 
   log.info('Summary:');
@@ -254,15 +220,6 @@ async function generator(
   return result;
 }
 
-function ensureFilePatterns(patterns: GenerateFilePatterns = {}): Required<GenerateFilePatterns> {
-  return {
-    resources: ({ serviceShortName }) => `${serviceShortName}.generated.ts`,
-    augmentations: ({ serviceShortName }) => `${serviceShortName}-augmentations.generated.ts`,
-    cannedMetrics: ({ serviceShortName }) => `${serviceShortName}-canned-metrics.generated.ts`,
-    ...patterns,
-  };
-}
-
 function pick<T>(property: keyof T) {
   type x = typeof property;
   return (obj: Record<x, any>): any => {
@@ -276,3 +233,10 @@ function mergeObjects<T>(all: T, res: T) {
     ...res,
   };
 }
+
+function noUndefined<A extends object>(x: A | undefined): A | undefined {
+  if (!x) {
+    return undefined;
+  }
+  return Object.fromEntries(Object.entries(x).filter(([, v]) => v !== undefined)) as any;
+}
diff --git a/tools/@aws-cdk/spec2cdk/lib/util/patterned-name.ts b/tools/@aws-cdk/spec2cdk/lib/util/patterned-name.ts
index 88e4e1d708c83..c921bfa092b18 100644
--- a/tools/@aws-cdk/spec2cdk/lib/util/patterned-name.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/util/patterned-name.ts
@@ -1,10 +1,14 @@
-export function parsePattern<A extends string>(pattern: string, fields: { [k in A]: unknown }): PatternedString<A> {
-  const placeholders = Object.keys(fields);
-  if (!placeholders.some((param) => pattern.includes(param))) {
-    throw new Error(`--pattern must contain one of [${placeholders.join(', ')}]`);
+export const PATTERN_FIELDS = ['moduleName', 'serviceName', 'serviceShortName'];
+
+export type FilePatternKeys = (typeof PATTERN_FIELDS)[number];
+
+export function parseFilePattern(pattern: string): FilePatternFormatter {
+  if (!PATTERN_FIELDS.some((param) => pattern.includes(param))) {
+    // eslint-disable-next-line @cdklabs/no-throw-default-error
+    throw new Error(`--pattern must contain one of [${PATTERN_FIELDS.join(', ')}]`);
   }
 
-  return (values: { [k in A]: string }) => {
+  return (values: { [k in FilePatternKeys]: string }) => {
     let ret = pattern;
     for (const [k, v] of Object.entries(values)) {
       ret = ret.replace(`%${k}%`, String(v));
@@ -13,6 +17,10 @@ export function parsePattern<A extends string>(pattern: string, fields: { [k in
   };
 }
 
-export type PatternValues<A extends string> = { [k in A]: string };
+export type FilePatternValues = { [k in FilePatternKeys]: string };
+
+export function substituteFilePattern(pattern: string, values: FilePatternValues): string {
+  return parseFilePattern(pattern)(values);
+}
 
-export type PatternedString<A extends string> = (values: PatternValues<A>) => string;
+export type FilePatternFormatter = (values: FilePatternValues) => string;
diff --git a/tools/@aws-cdk/spec2cdk/lib/util/ts-file-writer.ts b/tools/@aws-cdk/spec2cdk/lib/util/ts-file-writer.ts
index 298cf97ce5f45..4a085fa95f178 100644
--- a/tools/@aws-cdk/spec2cdk/lib/util/ts-file-writer.ts
+++ b/tools/@aws-cdk/spec2cdk/lib/util/ts-file-writer.ts
@@ -1,29 +1,23 @@
 import * as path from 'node:path';
 import { Module, TypeScriptRenderer } from '@cdklabs/typewriter';
 import * as fs from 'fs-extra';
-import { PatternValues, PatternedString } from './patterned-name';
-import { PatternKeys } from '../generate';
 
-export class TsFileWriter {
+export interface IWriter {
+  write(module: Module, filePath: string): string;
+}
+
+export class TsFileWriter implements IWriter {
   public outputFiles = new Array<string>();
 
   constructor(
-    private readonly outputPath: string,
+    private readonly rootDir: string,
     private readonly renderer: TypeScriptRenderer,
-    private readonly values: PatternValues<PatternKeys>,
   ) {}
 
-  public write(module: Module, filePath: string | PatternedString<PatternKeys>): string {
-    const output = this.resolveFilePath(filePath);
-    fs.outputFileSync(output, this.renderer.render(module));
-    this.outputFiles.push(output);
-    return output;
-  }
-
-  private resolveFilePath(filePath: string | PatternedString<PatternKeys>): string {
-    if (typeof filePath === 'function') {
-      return path.join(this.outputPath, filePath(this.values));
-    }
-    return filePath;
+  public write(module: Module, filePath: string): string {
+    const fullPath = path.join(this.rootDir, filePath);
+    fs.outputFileSync(fullPath, this.renderer.render(module));
+    this.outputFiles.push(fullPath);
+    return fullPath;
   }
 }
diff --git a/tools/@aws-cdk/spec2cdk/test/cli.test.ts b/tools/@aws-cdk/spec2cdk/test/cli.test.ts
index 0a2dc78d9946f..34df28fe5af79 100644
--- a/tools/@aws-cdk/spec2cdk/test/cli.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/cli.test.ts
@@ -8,8 +8,11 @@ describe('cli', () => {
     await withTemporaryDirectory(async ({ testDir }) => {
       await main([testDir, '--service', 'AWS::S3', '--service', 'AWS::SNS']);
 
-      expect(fs.existsSync(path.join(testDir, 'aws-s3', 's3.generated.ts'))).toBe(true);
-      expect(fs.existsSync(path.join(testDir, 'aws-sns', 'sns.generated.ts'))).toBe(true);
+      const generated = await deepListDir(testDir);
+
+      expect(generated).toContainEqual('aws-s3/s3.generated.ts');
+      expect(generated).toContainEqual('aws-sns/sns.generated.ts');
+      expect(generated).toContainEqual('aws-sns/sns-canned-metrics.generated.ts');
     });
   });
 });
@@ -31,3 +34,21 @@ async function withTemporaryDirectory(block: (context: TemporaryDirectoryContext
     });
   }
 }
+
+async function deepListDir(root: string): Promise<string[]> {
+  const result = new Array<string>();
+  const queue = [root];
+  while (queue.length > 0) {
+    const dir = queue.shift()!;
+    const entries = await fs.promises.readdir(dir, { withFileTypes: true });
+    for (const entry of entries) {
+      const fullPath = path.join(dir, entry.name);
+      if (entry.isDirectory()) {
+        queue.push(fullPath);
+      } else {
+        result.push(path.relative(root, fullPath));
+      }
+    }
+  }
+  return result;
+}
diff --git a/tools/@aws-cdk/spec2cdk/test/fake-services.test.ts b/tools/@aws-cdk/spec2cdk/test/fake-services.test.ts
index 50ae934cd560e..9dd06fc44708e 100644
--- a/tools/@aws-cdk/spec2cdk/test/fake-services.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/fake-services.test.ts
@@ -33,8 +33,9 @@ test('can codegen deprecated service', () => {
   });
   db.link('hasResource', service, resource);
 
-  const ast = AstBuilder.forService(service, { db, deprecated: 'in favour of something else' });
+  const ast = new AstBuilder({ db });
+  const info = ast.addService(service, { deprecated: 'in favour of something else' });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(info.resourcesMod.module);
   expect(rendered).toMatchSnapshot();
 });
diff --git a/tools/@aws-cdk/spec2cdk/test/history.test.ts b/tools/@aws-cdk/spec2cdk/test/history.test.ts
index 9bc4ee0f3fab9..9b0531c798646 100644
--- a/tools/@aws-cdk/spec2cdk/test/history.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/history.test.ts
@@ -13,8 +13,10 @@ beforeAll(async () => {
 // To ensure backwards compatibility we will render previous types
 test('Previous types are rendered', () => {
   const resource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::CloudFormation::StackSet')[0];
-  const ast = AstBuilder.forResource(resource, { db });
-  const stackSet = ast.module?.tryFindType('@aws-cdk/cloudformation/stackset-l1.CfnStackSet') as unknown as IScope;
+  const info = new AstBuilder({ db }).addResource(resource);
 
-  expect(stackSet.tryFindType('@aws-cdk/cloudformation/stackset-l1.CfnStackSet.ManagedExecutionProperty')).toBeTruthy();
+  const modName = '@aws-cdk/aws-cloudformation/aws-cloudformation';
+  const stackSet = info.resourcesMod.module.tryFindType(`${modName}.CfnStackSet`) as unknown as IScope;
+
+  expect(stackSet.tryFindType(`${modName}.CfnStackSet.ManagedExecutionProperty`)).toBeTruthy();
 });
diff --git a/tools/@aws-cdk/spec2cdk/test/relationships.test.ts b/tools/@aws-cdk/spec2cdk/test/relationships.test.ts
index b127d8f4386ee..2d44fbe0ca800 100644
--- a/tools/@aws-cdk/spec2cdk/test/relationships.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/relationships.test.ts
@@ -53,8 +53,9 @@ maybeTest('resource with relationship reference', () => {
   });
   db.link('hasResource', service, sourceResource);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -109,8 +110,9 @@ maybeTest('resource with multiple relationship references', () => {
   });
   db.link('hasResource', service, policyResource);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -157,8 +159,9 @@ maybeTest('resource with nested relationship requiring flattening', () => {
   db.link('hasResource', service, taskResource);
   db.link('usesType', taskResource, configType);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -205,8 +208,9 @@ maybeTest('resource with array of nested properties with relationship', () => {
   db.link('hasResource', service, resourceResource);
   db.link('usesType', resourceResource, permissionType);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -272,8 +276,9 @@ maybeTest('resource with nested relationship with type history', () => {
   db.link('usesType', jobResource, configType);
   db.link('usesType', jobResource, oldConfigType);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -327,8 +332,9 @@ maybeTest('relationship have arns appear first in the constructor chain', () =>
   db.link('hasResource', service, taskResource);
   db.link('usesType', taskResource, configType);
 
-  const ast = AstBuilder.forService(service, { db });
-  const rendered = renderer.render(ast.module);
+  const module = new AstBuilder({ db }).addService(service).resourcesMod.module;
+
+  const rendered = renderer.render(module);
 
   const chain = '"roleArn": (props.roleArn as IRoleRef)?.roleRef?.roleArn ?? (props.roleArn as IRoleRef)?.roleRef?.roleName ?? (props.roleArn as IRoleRef)?.roleRef?.otherPrimaryId ?? props.roleArn';
 
diff --git a/tools/@aws-cdk/spec2cdk/test/resources.test.ts b/tools/@aws-cdk/spec2cdk/test/resources.test.ts
index ae41761690096..6fa4881faffcf 100644
--- a/tools/@aws-cdk/spec2cdk/test/resources.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/resources.test.ts
@@ -1,6 +1,6 @@
-import { Service, SpecDatabase, emptyDatabase } from '@aws-cdk/service-spec-types';
+import { Resource, Service, SpecDatabase, emptyDatabase } from '@aws-cdk/service-spec-types';
 import { TypeScriptRenderer } from '@cdklabs/typewriter';
-import { AstBuilder } from '../lib/cdk/ast';
+import { AstBuilder, AstBuilderProps } from '../lib/cdk/ast';
 
 const renderer = new TypeScriptRenderer();
 let db: SpecDatabase;
@@ -36,9 +36,9 @@ test('resource interface when primaryIdentifier is a property', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -63,9 +63,9 @@ test('resource with arnTemplate', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -89,9 +89,9 @@ test('resource with optional primary identifier gets property from ref', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -119,9 +119,9 @@ test('resource with multiple primaryIdentifiers as properties', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -145,9 +145,9 @@ test('resource interface when primaryIdentifier is an attribute', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -175,9 +175,9 @@ test('resource interface with multiple primaryIdentifiers', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -205,9 +205,9 @@ test('resource interface with "Arn"', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -235,9 +235,9 @@ test('resource interface with "<Resource>Arn"', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Something').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -266,9 +266,9 @@ test('resource interface with Arn as a property and not a primaryIdentifier', ()
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
@@ -292,9 +292,15 @@ test('resource interface with Arn as primaryIdentifier', () => {
   // THEN
   const foundResource = db.lookup('resource', 'cloudFormationType', 'equals', 'AWS::Some::Resource').only();
 
-  const ast = AstBuilder.forResource(foundResource, { db });
+  const module = moduleForResource(foundResource, { db });
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   expect(rendered).toMatchSnapshot();
 });
+
+function moduleForResource(resource: Resource, props: AstBuilderProps) {
+  const ast = new AstBuilder(props);
+  const info = ast.addResource(resource);
+  return info.resourcesMod.module;
+}
diff --git a/tools/@aws-cdk/spec2cdk/test/services.test.ts b/tools/@aws-cdk/spec2cdk/test/services.test.ts
index 677a0cdc62eea..8633072e2820e 100644
--- a/tools/@aws-cdk/spec2cdk/test/services.test.ts
+++ b/tools/@aws-cdk/spec2cdk/test/services.test.ts
@@ -13,9 +13,9 @@ beforeAll(async () => {
 test('can codegen service with arbitrary suffix', () => {
   const service = db.lookup('service', 'name', 'equals', 'aws-kinesisanalyticsv2').only();
 
-  const ast = AstBuilder.forService(service, { db, nameSuffix: 'V2' });
+  const module = new AstBuilder({ db }).addService(service, { nameSuffix: 'V2' }).resourcesMod.module;
 
-  const rendered = renderer.render(ast.module);
+  const rendered = renderer.render(module);
 
   // Snapshot tests will fail every time the docs get updated
   // expect(rendered).toMatchSnapshot();