diff --git a/packages/core/schematics/migrations/document-core/document_core_migration.ts b/packages/core/schematics/migrations/document-core/document_core_migration.ts
index 63a2253af1d..4fb71f3b473 100644
--- a/packages/core/schematics/migrations/document-core/document_core_migration.ts
+++ b/packages/core/schematics/migrations/document-core/document_core_migration.ts
@@ -91,6 +91,6 @@ export class DocumentCoreMigration extends TsurgeFunnelMigration<
   }
 
   override async stats() {
-    return {counters: {}};
+    return confirmAsSerializable({});
   }
 }
diff --git a/packages/core/schematics/migrations/inject-flags/inject_flags_migration.ts b/packages/core/schematics/migrations/inject-flags/inject_flags_migration.ts
index 9de9d3a39cd..ce46ebefdcb 100644
--- a/packages/core/schematics/migrations/inject-flags/inject_flags_migration.ts
+++ b/packages/core/schematics/migrations/inject-flags/inject_flags_migration.ts
@@ -153,7 +153,7 @@ export class InjectFlagsMigration extends TsurgeFunnelMigration<
   }
 
   override async stats() {
-    return {counters: {}};
+    return confirmAsSerializable({});
   }
 }
 
diff --git a/packages/core/schematics/migrations/output-migration/output-migration.spec.ts b/packages/core/schematics/migrations/output-migration/output-migration.spec.ts
index fc9f059c8ee..fd29b798d56 100644
--- a/packages/core/schematics/migrations/output-migration/output-migration.spec.ts
+++ b/packages/core/schematics/migrations/output-migration/output-migration.spec.ts
@@ -678,9 +678,9 @@ describe('outputs', () => {
       ]);
 
       const stats = await runResults.getStatistics();
-      expect(stats.counters['detectedOutputs']).toBe(4);
-      expect(stats.counters['problematicOutputs']).toBe(2);
-      expect(stats.counters['successRate']).toBe(0.5);
+      expect(stats['detectedOutputs']).toBe(4);
+      expect(stats['problematicOutputs']).toBe(2);
+      expect(stats['successRate']).toBe(0.5);
     });
 
     it('should capture migration statistics without problematic usages', async () => {
@@ -696,9 +696,9 @@ describe('outputs', () => {
       ]);
 
       const stats = await runResults.getStatistics();
-      expect(stats.counters['detectedOutputs']).toBe(2);
-      expect(stats.counters['problematicOutputs']).toBe(0);
-      expect(stats.counters['successRate']).toBe(1);
+      expect(stats['detectedOutputs']).toBe(2);
+      expect(stats['problematicOutputs']).toBe(0);
+      expect(stats['successRate']).toBe(1);
     });
   });
 
diff --git a/packages/core/schematics/migrations/output-migration/output-migration.ts b/packages/core/schematics/migrations/output-migration/output-migration.ts
index 3a34dca85b6..fd2c376f17d 100644
--- a/packages/core/schematics/migrations/output-migration/output-migration.ts
+++ b/packages/core/schematics/migrations/output-migration/output-migration.ts
@@ -9,7 +9,6 @@
 import ts from 'typescript';
 import {
   confirmAsSerializable,
-  MigrationStats,
   ProgramInfo,
   projectFile,
   ProjectFile,
@@ -384,7 +383,7 @@ export class OutputMigration extends TsurgeFunnelMigration<
     return confirmAsSerializable(combinedData);
   }
 
-  override async stats(globalMetadata: CompilationUnitData): Promise<MigrationStats> {
+  override async stats(globalMetadata: CompilationUnitData) {
     const detectedOutputs =
       new Set(Object.keys(globalMetadata.outputFields)).size +
       globalMetadata.problematicDeclarationCount;
@@ -395,13 +394,11 @@ export class OutputMigration extends TsurgeFunnelMigration<
     const successRate =
       detectedOutputs > 0 ? (detectedOutputs - problematicOutputs) / detectedOutputs : 1;
 
-    return {
-      counters: {
-        detectedOutputs,
-        problematicOutputs,
-        successRate,
-      },
-    };
+    return confirmAsSerializable({
+      detectedOutputs,
+      problematicOutputs,
+      successRate,
+    });
   }
 
   override async migrate(globalData: CompilationUnitData) {
diff --git a/packages/core/schematics/migrations/self-closing-tags-migration/self-closing-tags-migration.ts b/packages/core/schematics/migrations/self-closing-tags-migration/self-closing-tags-migration.ts
index e3ffe0f5e10..8191c066cbc 100644
--- a/packages/core/schematics/migrations/self-closing-tags-migration/self-closing-tags-migration.ts
+++ b/packages/core/schematics/migrations/self-closing-tags-migration/self-closing-tags-migration.ts
@@ -9,7 +9,6 @@
 import ts from 'typescript';
 import {
   confirmAsSerializable,
-  MigrationStats,
   ProgramInfo,
   projectFile,
   ProjectFile,
@@ -128,21 +127,17 @@ export class SelfClosingTagsMigration extends TsurgeFunnelMigration<
     return confirmAsSerializable(globalMeta);
   }
 
-  override async stats(
-    globalMetadata: SelfClosingTagsCompilationUnitData,
-  ): Promise<MigrationStats> {
+  override async stats(globalMetadata: SelfClosingTagsCompilationUnitData) {
     const touchedFilesCount = globalMetadata.tagReplacements.length;
     const replacementCount = globalMetadata.tagReplacements.reduce(
       (acc, cur) => acc + cur.replacementCount,
       0,
     );
 
-    return {
-      counters: {
-        touchedFilesCount,
-        replacementCount,
-      },
-    };
+    return confirmAsSerializable({
+      touchedFilesCount,
+      replacementCount,
+    });
   }
 
   override async migrate(globalData: SelfClosingTagsCompilationUnitData) {
diff --git a/packages/core/schematics/migrations/signal-migration/src/migration.ts b/packages/core/schematics/migrations/signal-migration/src/migration.ts
index 476b7d0eedc..ccd5c48ac7d 100644
--- a/packages/core/schematics/migrations/signal-migration/src/migration.ts
+++ b/packages/core/schematics/migrations/signal-migration/src/migration.ts
@@ -231,15 +231,13 @@ export class SignalInputMigration extends TsurgeComplexMigration<
       }
     }
 
-    return {
-      counters: {
-        fullCompilationInputs,
-        sourceInputs,
-        incompatibleInputs,
-        ...fieldIncompatibleCounts,
-        ...classIncompatibleCounts,
-      },
-    };
+    return confirmAsSerializable({
+      fullCompilationInputs,
+      sourceInputs,
+      incompatibleInputs,
+      ...fieldIncompatibleCounts,
+      ...classIncompatibleCounts,
+    });
   }
 }
 
diff --git a/packages/core/schematics/migrations/signal-queries-migration/migration.spec.ts b/packages/core/schematics/migrations/signal-queries-migration/migration.spec.ts
index a6bdc549ef2..93f017b285e 100644
--- a/packages/core/schematics/migrations/signal-queries-migration/migration.spec.ts
+++ b/packages/core/schematics/migrations/signal-queries-migration/migration.spec.ts
@@ -1586,14 +1586,14 @@ describe('signal queries migration', () => {
       ],
     );
 
-    expect(await getStatistics()).toEqual({
-      counters: {
-        queriesCount: 3,
-        multiQueries: 2,
-        incompatibleQueries: 2,
-        'incompat-field-Accessor': 1,
-        'incompat-field-WriteAssignment': 1,
-      },
+    // Cast as we dynamically add fields to the stats. This can be improved in follow-ups
+    // when stats for this migration are leveraging more complex data structures.
+    expect((await getStatistics()) as object).toEqual({
+      queriesCount: 3,
+      multiQueries: 2,
+      incompatibleQueries: 2,
+      'incompat-field-Accessor': 1,
+      'incompat-field-WriteAssignment': 1,
     });
   });
 
diff --git a/packages/core/schematics/migrations/signal-queries-migration/migration.ts b/packages/core/schematics/migrations/signal-queries-migration/migration.ts
index 94473c36360..0defafc6110 100644
--- a/packages/core/schematics/migrations/signal-queries-migration/migration.ts
+++ b/packages/core/schematics/migrations/signal-queries-migration/migration.ts
@@ -644,15 +644,13 @@ export class SignalQueriesMigration extends TsurgeComplexMigration<
       }
     }
 
-    return {
-      counters: {
-        queriesCount,
-        multiQueries,
-        incompatibleQueries,
-        ...fieldIncompatibleCounts,
-        ...classIncompatibleCounts,
-      },
-    };
+    return confirmAsSerializable({
+      queriesCount,
+      multiQueries,
+      incompatibleQueries,
+      ...fieldIncompatibleCounts,
+      ...classIncompatibleCounts,
+    });
   }
 }
 
diff --git a/packages/core/schematics/migrations/test-bed-get/test_bed_get_migration.ts b/packages/core/schematics/migrations/test-bed-get/test_bed_get_migration.ts
index e252eae2dc8..64e8554733f 100644
--- a/packages/core/schematics/migrations/test-bed-get/test_bed_get_migration.ts
+++ b/packages/core/schematics/migrations/test-bed-get/test_bed_get_migration.ts
@@ -110,6 +110,6 @@ export class TestBedGetMigration extends TsurgeFunnelMigration<
   }
 
   override async stats() {
-    return {counters: {}};
+    return confirmAsSerializable({});
   }
 }
diff --git a/packages/core/schematics/ng-generate/cleanup-unused-imports/index.ts b/packages/core/schematics/ng-generate/cleanup-unused-imports/index.ts
index b04e3b2cf01..9f35647d9a4 100644
--- a/packages/core/schematics/ng-generate/cleanup-unused-imports/index.ts
+++ b/packages/core/schematics/ng-generate/cleanup-unused-imports/index.ts
@@ -28,8 +28,7 @@ export function migrate(): Rule {
       afterAnalysisFailure: () => {
         context.logger.error('Schematic failed unexpectedly with no analysis data');
       },
-      whenDone: (stats) => {
-        const {removedImports, changedFiles} = stats.counters;
+      whenDone: ({removedImports, changedFiles}) => {
         let statsMessage: string;
 
         if (removedImports === 0) {
diff --git a/packages/core/schematics/ng-generate/cleanup-unused-imports/unused_imports_migration.ts b/packages/core/schematics/ng-generate/cleanup-unused-imports/unused_imports_migration.ts
index 924ed5380be..e17a6ebc6f4 100644
--- a/packages/core/schematics/ng-generate/cleanup-unused-imports/unused_imports_migration.ts
+++ b/packages/core/schematics/ng-generate/cleanup-unused-imports/unused_imports_migration.ts
@@ -10,7 +10,6 @@ import ts from 'typescript';
 import {
   BaseProgramInfo,
   confirmAsSerializable,
-  MigrationStats,
   ProgramInfo,
   projectFile,
   ProjectFileID,
@@ -163,13 +162,11 @@ export class UnusedImportsMigration extends TsurgeFunnelMigration<
     return confirmAsSerializable(combinedData);
   }
 
-  override async stats(globalMetadata: CompilationUnitData): Promise<MigrationStats> {
-    return {
-      counters: {
-        removedImports: globalMetadata.removedIdentifiers.length,
-        changedFiles: globalMetadata.changedFiles,
-      },
-    };
+  override async stats(globalMetadata: CompilationUnitData) {
+    return confirmAsSerializable({
+      removedImports: globalMetadata.removedIdentifiers.length,
+      changedFiles: globalMetadata.changedFiles,
+    });
   }
 
   /** Gets an ID that can be used to look up a node based on its location. */
diff --git a/packages/core/schematics/ng-generate/output-migration/index.ts b/packages/core/schematics/ng-generate/output-migration/index.ts
index 9f7c2613c01..9293b4daa5a 100644
--- a/packages/core/schematics/ng-generate/output-migration/index.ts
+++ b/packages/core/schematics/ng-generate/output-migration/index.ts
@@ -57,8 +57,7 @@ export function migrate(options: Options): Rule {
       afterAnalysisFailure: () => {
         context.logger.error('Migration failed unexpectedly with no analysis data');
       },
-      whenDone: ({counters}) => {
-        const {detectedOutputs, problematicOutputs, successRate} = counters;
+      whenDone: ({detectedOutputs, problematicOutputs, successRate}) => {
         const migratedOutputs = detectedOutputs - problematicOutputs;
         const successRatePercent = (successRate * 100).toFixed(2);
 
diff --git a/packages/core/schematics/ng-generate/self-closing-tags-migration/index.ts b/packages/core/schematics/ng-generate/self-closing-tags-migration/index.ts
index 5b9109b12ff..789852800f6 100644
--- a/packages/core/schematics/ng-generate/self-closing-tags-migration/index.ts
+++ b/packages/core/schematics/ng-generate/self-closing-tags-migration/index.ts
@@ -46,8 +46,7 @@ export function migrate(options: Options): Rule {
       afterAnalysisFailure: () => {
         context.logger.error('Migration failed unexpectedly with no analysis data');
       },
-      whenDone: ({counters}) => {
-        const {touchedFilesCount, replacementCount} = counters;
+      whenDone: ({touchedFilesCount, replacementCount}) => {
         context.logger.info('');
         context.logger.info(`Successfully migrated to self-closing tags 🎉`);
         context.logger.info(
diff --git a/packages/core/schematics/ng-generate/signal-input-migration/index.ts b/packages/core/schematics/ng-generate/signal-input-migration/index.ts
index e6a49fd8a1b..8330d732a9d 100644
--- a/packages/core/schematics/ng-generate/signal-input-migration/index.ts
+++ b/packages/core/schematics/ng-generate/signal-input-migration/index.ts
@@ -61,8 +61,7 @@ export function migrate(options: Options): Rule {
       afterAnalysisFailure: () => {
         context.logger.error('Migration failed unexpectedly with no analysis data');
       },
-      whenDone: ({counters}) => {
-        const {sourceInputs, incompatibleInputs} = counters;
+      whenDone: ({sourceInputs, incompatibleInputs}) => {
         const migratedInputs = sourceInputs - incompatibleInputs;
 
         context.logger.info('');
diff --git a/packages/core/schematics/ng-generate/signal-queries-migration/index.ts b/packages/core/schematics/ng-generate/signal-queries-migration/index.ts
index b13fa85aa15..ac0b63515bc 100644
--- a/packages/core/schematics/ng-generate/signal-queries-migration/index.ts
+++ b/packages/core/schematics/ng-generate/signal-queries-migration/index.ts
@@ -61,11 +61,10 @@ export function migrate(options: Options): Rule {
         context.logger.info(`Processing analysis data between targets...`);
         context.logger.info(``);
       },
-      whenDone: ({counters}) => {
+      whenDone: ({queriesCount, incompatibleQueries}) => {
         context.logger.info('');
         context.logger.info(`Successfully migrated to signal queries 🎉`);
 
-        const {queriesCount, incompatibleQueries} = counters;
         const migratedQueries = queriesCount - incompatibleQueries;
 
         context.logger.info('');
diff --git a/packages/core/schematics/test/BUILD.bazel b/packages/core/schematics/test/BUILD.bazel
index 6d26d3f3f53..d41b8309bcc 100644
--- a/packages/core/schematics/test/BUILD.bazel
+++ b/packages/core/schematics/test/BUILD.bazel
@@ -32,6 +32,7 @@ jasmine_node_test(
         "//packages/core/schematics/ng-generate/signals:static_files",
         "//packages/core/schematics/ng-generate/standalone-migration:static_files",
     ],
+    shard_count = 4,
     deps = [
         ":test_lib",
         "@npm//shelljs",
diff --git a/packages/core/schematics/utils/tsurge/base_migration.ts b/packages/core/schematics/utils/tsurge/base_migration.ts
index 516d5cf9d9f..f01dbc83e73 100644
--- a/packages/core/schematics/utils/tsurge/base_migration.ts
+++ b/packages/core/schematics/utils/tsurge/base_migration.ts
@@ -14,15 +14,9 @@ import {BaseProgramInfo, ProgramInfo} from './program_info';
 import {Serializable} from './helpers/serializable';
 import {createBaseProgramInfo} from './helpers/create_program';
 
-/**
- * Type describing statistics that could be tracked
- * by migrations.
- *
- * Statistics may be tracked depending on the runner.
- */
-export interface MigrationStats {
-  counters: Record<string, number>;
-}
+/** Type helper extracting the stats type of a migration. */
+export type MigrationStats<T> =
+  T extends TsurgeBaseMigration<unknown, unknown, infer Stats> ? Stats : never;
 
 /**
  * @private
@@ -32,7 +26,12 @@ export interface MigrationStats {
  * For example, this class exposes methods to conveniently create
  * TypeScript programs, while also allowing migration authors to override.
  */
-export abstract class TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMetadata> {
+export abstract class TsurgeBaseMigration<
+  UnitAnalysisMetadata,
+  CombinedGlobalMetadata,
+  // Note: Even when optional, they can be inferred from implementations.
+  Stats = unknown,
+> {
   /**
    * Advanced Tsurge users can override this method, but most of the time,
    * overriding {@link prepareProgram} is more desirable.
@@ -103,5 +102,5 @@ export abstract class TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMe
   ): Promise<Serializable<CombinedGlobalMetadata>>;
 
   /** Extract statistics based on the global metadata. */
-  abstract stats(globalMetadata: CombinedGlobalMetadata): Promise<MigrationStats>;
+  abstract stats(globalMetadata: CombinedGlobalMetadata): Promise<Serializable<Stats>>;
 }
diff --git a/packages/core/schematics/utils/tsurge/executors/analyze_exec.ts b/packages/core/schematics/utils/tsurge/executors/analyze_exec.ts
index 892dece28a7..5f51b302cc6 100644
--- a/packages/core/schematics/utils/tsurge/executors/analyze_exec.ts
+++ b/packages/core/schematics/utils/tsurge/executors/analyze_exec.ts
@@ -16,7 +16,7 @@ import {Serializable} from '../helpers/serializable';
  * @returns the serializable migration unit data.
  */
 export async function executeAnalyzePhase<UnitData, GlobalData>(
-  migration: TsurgeMigration<UnitData, GlobalData>,
+  migration: TsurgeMigration<UnitData, GlobalData, unknown>,
   tsconfigAbsolutePath: string,
 ): Promise<Serializable<UnitData>> {
   const baseInfo = migration.createProgram(tsconfigAbsolutePath);
diff --git a/packages/core/schematics/utils/tsurge/executors/combine_exec.ts b/packages/core/schematics/utils/tsurge/executors/combine_exec.ts
index 09c21477997..bc354e83f29 100644
--- a/packages/core/schematics/utils/tsurge/executors/combine_exec.ts
+++ b/packages/core/schematics/utils/tsurge/executors/combine_exec.ts
@@ -16,7 +16,7 @@ import {TsurgeMigration} from '../migration';
  * @returns the serializable combined unit data.
  */
 export async function executeCombinePhase<UnitData, GlobalData>(
-  migration: TsurgeMigration<UnitData, GlobalData>,
+  migration: TsurgeMigration<UnitData, GlobalData, unknown>,
   unitA: UnitData,
   unitB: UnitData,
 ): Promise<Serializable<UnitData>> {
diff --git a/packages/core/schematics/utils/tsurge/executors/global_meta_exec.ts b/packages/core/schematics/utils/tsurge/executors/global_meta_exec.ts
index 950f0ebcb3a..0566b85ad68 100644
--- a/packages/core/schematics/utils/tsurge/executors/global_meta_exec.ts
+++ b/packages/core/schematics/utils/tsurge/executors/global_meta_exec.ts
@@ -16,7 +16,7 @@ import {TsurgeMigration} from '../migration';
  * @returns the serializable global meta.
  */
 export async function executeGlobalMetaPhase<UnitData, GlobalData>(
-  migration: TsurgeMigration<UnitData, GlobalData>,
+  migration: TsurgeMigration<UnitData, GlobalData, unknown>,
   combinedUnitData: UnitData,
 ): Promise<Serializable<GlobalData>> {
   return await migration.globalMeta(combinedUnitData);
diff --git a/packages/core/schematics/utils/tsurge/executors/migrate_exec.ts b/packages/core/schematics/utils/tsurge/executors/migrate_exec.ts
index 3a64e820415..268eba95069 100644
--- a/packages/core/schematics/utils/tsurge/executors/migrate_exec.ts
+++ b/packages/core/schematics/utils/tsurge/executors/migrate_exec.ts
@@ -21,7 +21,7 @@ import {Replacement} from '../replacement';
  *   absolute project directory path (to allow for applying).
  */
 export async function executeMigratePhase<UnitData, GlobalData>(
-  migration: TsurgeMigration<UnitData, GlobalData>,
+  migration: TsurgeMigration<UnitData, GlobalData, unknown>,
   globalMetadata: GlobalData,
   tsconfigAbsolutePath: string,
 ): Promise<{replacements: Replacement[]; projectRoot: AbsoluteFsPath}> {
diff --git a/packages/core/schematics/utils/tsurge/helpers/angular_devkit/run_in_devkit.ts b/packages/core/schematics/utils/tsurge/helpers/angular_devkit/run_in_devkit.ts
index 8b4f51566e8..8c231969db9 100644
--- a/packages/core/schematics/utils/tsurge/helpers/angular_devkit/run_in_devkit.ts
+++ b/packages/core/schematics/utils/tsurge/helpers/angular_devkit/run_in_devkit.ts
@@ -27,9 +27,9 @@ export enum MigrationStage {
 }
 
 /** Information necessary to run a Tsurge migration in the devkit. */
-export interface TsurgeDevkitMigration {
+export interface TsurgeDevkitMigration<Stats> {
   /** Instantiates the migration. */
-  getMigration: (fs: FileSystem) => TsurgeMigration<unknown, unknown>;
+  getMigration: (fs: FileSystem) => TsurgeMigration<unknown, unknown, Stats>;
 
   /** File tree of the schematic. */
   tree: Tree;
@@ -53,11 +53,13 @@ export interface TsurgeDevkitMigration {
   afterAnalysisFailure?: () => void;
 
   /** Called when the migration is done running and stats are available. Useful for logging. */
-  whenDone?: (stats: MigrationStats) => void;
+  whenDone?: (stats: Stats) => void;
 }
 
 /** Runs a Tsurge within an Angular Devkit context. */
-export async function runMigrationInDevkit(config: TsurgeDevkitMigration): Promise<void> {
+export async function runMigrationInDevkit<Stats>(
+  config: TsurgeDevkitMigration<Stats>,
+): Promise<void> {
   const {buildPaths, testPaths} = await getProjectTsConfigPaths(config.tree);
 
   if (!buildPaths.length && !testPaths.length) {
diff --git a/packages/core/schematics/utils/tsurge/helpers/combine_units.ts b/packages/core/schematics/utils/tsurge/helpers/combine_units.ts
index 2405dfb6a39..10ae8b280dd 100644
--- a/packages/core/schematics/utils/tsurge/helpers/combine_units.ts
+++ b/packages/core/schematics/utils/tsurge/helpers/combine_units.ts
@@ -16,7 +16,7 @@ import {TsurgeMigration} from '../migration';
  * prefer parallel execution of combining via e.g. Beam combiners.
  */
 export async function synchronouslyCombineUnitData<UnitData>(
-  migration: TsurgeMigration<UnitData, unknown>,
+  migration: TsurgeMigration<UnitData, unknown, unknown>,
   unitDatas: UnitData[],
 ): Promise<UnitData | null> {
   if (unitDatas.length === 0) {
diff --git a/packages/core/schematics/utils/tsurge/migration.ts b/packages/core/schematics/utils/tsurge/migration.ts
index 3787977d921..3a074841d29 100644
--- a/packages/core/schematics/utils/tsurge/migration.ts
+++ b/packages/core/schematics/utils/tsurge/migration.ts
@@ -39,9 +39,9 @@ interface MigrateResult {
  *
  *  TODO: Link design doc
  */
-export type TsurgeMigration<UnitAnalysisMetadata, CombinedGlobalMetadata> =
-  | TsurgeComplexMigration<UnitAnalysisMetadata, CombinedGlobalMetadata>
-  | TsurgeFunnelMigration<UnitAnalysisMetadata, CombinedGlobalMetadata>;
+export type TsurgeMigration<UnitAnalysisMetadata, CombinedGlobalMetadata, Stats> =
+  | TsurgeComplexMigration<UnitAnalysisMetadata, CombinedGlobalMetadata, Stats>
+  | TsurgeFunnelMigration<UnitAnalysisMetadata, CombinedGlobalMetadata, Stats>;
 
 /**
  * A simpler variant of a {@link TsurgeComplexMigration} that does not
@@ -58,7 +58,8 @@ export type TsurgeMigration<UnitAnalysisMetadata, CombinedGlobalMetadata> =
 export abstract class TsurgeFunnelMigration<
   UnitAnalysisMetadata,
   CombinedGlobalMetadata,
-> extends TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMetadata> {
+  Stats = unknown,
+> extends TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMetadata, Stats> {
   /**
    * Finalizes the migration result.
    *
@@ -83,7 +84,8 @@ export abstract class TsurgeFunnelMigration<
 export abstract class TsurgeComplexMigration<
   UnitAnalysisMetadata,
   CombinedGlobalMetadata,
-> extends TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMetadata> {
+  Stats = unknown,
+> extends TsurgeBaseMigration<UnitAnalysisMetadata, CombinedGlobalMetadata, Stats> {
   /**
    * Migration phase. Workers will be started for every compilation unit again,
    * instantiating a new program for every unit to compute the final migration
diff --git a/packages/core/schematics/utils/tsurge/test/output_migration.spec.ts b/packages/core/schematics/utils/tsurge/test/output_migration.spec.ts
index 7ad37460af5..39a766243ab 100644
--- a/packages/core/schematics/utils/tsurge/test/output_migration.spec.ts
+++ b/packages/core/schematics/utils/tsurge/test/output_migration.spec.ts
@@ -97,10 +97,8 @@ describe('output migration', () => {
     ]);
 
     expect(await getStatistics()).toEqual({
-      counters: {
-        allOutputs: 2,
-        migratedOutputs: 1,
-      },
+      allOutputs: 2,
+      migratedOutputs: 1,
     });
   });
 });
diff --git a/packages/core/schematics/utils/tsurge/test/output_migration.ts b/packages/core/schematics/utils/tsurge/test/output_migration.ts
index 24f6d4be6ac..00296110d75 100644
--- a/packages/core/schematics/utils/tsurge/test/output_migration.ts
+++ b/packages/core/schematics/utils/tsurge/test/output_migration.ts
@@ -14,7 +14,6 @@ import {ProgramInfo} from '../program_info';
 import {Replacement, TextUpdate} from '../replacement';
 import {findOutputDeclarationsAndReferences, OutputID} from './output_helpers';
 import {projectFile} from '../project_paths';
-import {MigrationStats} from '../base_migration';
 
 type AnalysisUnit = {[id: OutputID]: {seenProblematicUsage: boolean}};
 type GlobalMetadata = {[id: OutputID]: {canBeMigrated: boolean}};
@@ -120,7 +119,7 @@ export class OutputMigration extends TsurgeComplexMigration<AnalysisUnit, Global
     return {replacements};
   }
 
-  override async stats(globalMetadata: GlobalMetadata): Promise<MigrationStats> {
+  override async stats(globalMetadata: GlobalMetadata) {
     let allOutputs = 0;
     let migratedOutputs = 0;
 
@@ -131,11 +130,9 @@ export class OutputMigration extends TsurgeComplexMigration<AnalysisUnit, Global
       }
     }
 
-    return {
-      counters: {
-        allOutputs,
-        migratedOutputs,
-      },
-    };
+    return confirmAsSerializable({
+      allOutputs,
+      migratedOutputs,
+    });
   }
 }
diff --git a/packages/core/schematics/utils/tsurge/testing/run_single.ts b/packages/core/schematics/utils/tsurge/testing/run_single.ts
index 1e5a1c5271e..6c7eb02be21 100644
--- a/packages/core/schematics/utils/tsurge/testing/run_single.ts
+++ b/packages/core/schematics/utils/tsurge/testing/run_single.ts
@@ -29,11 +29,11 @@ import {TestRun} from './test_run';
  *
  * @returns a mock file system with the applied replacements of the migration.
  */
-export async function runTsurgeMigration<UnitData, GlobalData>(
-  migration: TsurgeMigration<UnitData, GlobalData>,
+export async function runTsurgeMigration<Stats>(
+  migration: TsurgeMigration<unknown, unknown, Stats>,
   files: {name: AbsoluteFsPath; contents: string; isProgramRootFile?: boolean}[],
   compilerOptions: ts.CompilerOptions = {},
-): Promise<TestRun> {
+): Promise<TestRun<Stats>> {
   const mockFs = getFileSystem();
   if (!(mockFs instanceof MockFileSystem)) {
     throw new Error('Expected a mock file system for `runTsurgeMigration`.');
diff --git a/packages/core/schematics/utils/tsurge/testing/test_run.ts b/packages/core/schematics/utils/tsurge/testing/test_run.ts
index 45a0eebfe0d..3be526ce6f9 100644
--- a/packages/core/schematics/utils/tsurge/testing/test_run.ts
+++ b/packages/core/schematics/utils/tsurge/testing/test_run.ts
@@ -7,12 +7,11 @@
  */
 
 import {MockFileSystem} from '../../../../../compiler-cli/src/ngtsc/file_system/testing';
-import {MigrationStats} from '../base_migration';
 
 /** Type describing results of a Tsurge migration test run. */
-export interface TestRun {
+export interface TestRun<Stats> {
   /** File system that can be used to read migrated file contents. */
   fs: MockFileSystem;
   /** Function that can be invoked to compute migration statistics. */
-  getStatistics: () => Promise<MigrationStats>;
+  getStatistics: () => Promise<Stats>;
 }