diff --git a/packages/app/src/cli/models/extensions/extension-instance.test.ts b/packages/app/src/cli/models/extensions/extension-instance.test.ts
index 5a808958df9..dbafca2026a 100644
--- a/packages/app/src/cli/models/extensions/extension-instance.test.ts
+++ b/packages/app/src/cli/models/extensions/extension-instance.test.ts
@@ -72,10 +72,10 @@ describe('keepBuiltSourcemapsLocally', async () => {
 
         await extensionInstance.keepBuiltSourcemapsLocally(bundleDirectory)
 
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js.map'))).toBe(true)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js.map'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'uid1', 'scriptToMove.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'uid1', 'scriptToMove.js.map'))).toBe(true)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js.map'))).toBe(false)
       })
     })
   })
@@ -103,10 +103,10 @@ describe('keepBuiltSourcemapsLocally', async () => {
 
         await extensionInstance.keepBuiltSourcemapsLocally(bundleInputPath)
 
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js.map'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js.map'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'wrongUID', 'scriptToMove.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'wrongUID', 'scriptToMove.js.map'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js.map'))).toBe(false)
       })
     })
   })
@@ -133,10 +133,10 @@ describe('keepBuiltSourcemapsLocally', async () => {
 
         await extensionInstance.keepBuiltSourcemapsLocally(bundleDirectory)
 
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToMove.js.map'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js'))).toBe(false)
-        expect(fileExistsSync(joinPath(outputPath, 'dist', 'scriptToIgnore.js.map'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'uid1', 'scriptToMove.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'uid1', 'scriptToMove.js.map'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js'))).toBe(false)
+        expect(fileExistsSync(joinPath(outputPath, 'otherUID', 'scriptToIgnore.js.map'))).toBe(false)
       })
     })
   })
diff --git a/packages/app/src/cli/models/extensions/extension-instance.ts b/packages/app/src/cli/models/extensions/extension-instance.ts
index c292a95f8b2..ebc742ad74a 100644
--- a/packages/app/src/cli/models/extensions/extension-instance.ts
+++ b/packages/app/src/cli/models/extensions/extension-instance.ts
@@ -27,7 +27,7 @@ import {ok} from '@shopify/cli-kit/node/result'
 import {constantize, slugify} from '@shopify/cli-kit/common/string'
 import {hashString, nonRandomUUID} from '@shopify/cli-kit/node/crypto'
 import {partnersFqdn} from '@shopify/cli-kit/node/context/fqdn'
-import {joinPath, basename, normalizePath, resolvePath} from '@shopify/cli-kit/node/path'
+import {joinPath, normalizePath, resolvePath, relativePath, basename} from '@shopify/cli-kit/node/path'
 import {fileExists, touchFile, moveFile, writeFile, glob, copyFile, globSync} from '@shopify/cli-kit/node/fs'
 import {getPathValue} from '@shopify/cli-kit/common/object'
 import {outputDebug} from '@shopify/cli-kit/node/output'
@@ -143,14 +143,11 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
   }
 
   get outputFileName() {
-    const mode = this.specification.buildConfig.mode
-    if (mode === 'copy_files' || mode === 'theme') {
-      return ''
-    } else if (mode === 'function') {
-      return 'index.wasm'
-    } else {
-      return `${this.handle}.js`
-    }
+    return basename(this.outputRelativePath)
+  }
+
+  get outputRelativePath() {
+    return this.specification.getOutputRelativePath?.(this) ?? ''
   }
 
   constructor(options: {
@@ -168,19 +165,9 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
     this.handle = this.buildHandle()
     this.localIdentifier = this.handle
     this.idEnvironmentVariableName = `SHOPIFY_${constantize(this.localIdentifier)}_ID`
-    this.outputPath = this.directory
+    this.outputPath = joinPath(this.directory, this.outputRelativePath)
     this.uid = this.buildUIDFromStrategy()
     this.devUUID = `dev-${this.uid}`
-
-    if (this.features.includes('esbuild') || this.type === 'tax_calculation') {
-      this.outputPath = joinPath(this.directory, 'dist', this.outputFileName)
-    }
-
-    if (this.isFunctionExtension) {
-      const config = this.configuration as unknown as FunctionConfigType
-      const defaultPath = joinPath('dist', 'index.wasm')
-      this.outputPath = joinPath(this.directory, config.build?.path ?? defaultPath)
-    }
   }
 
   get draftMessages() {
@@ -253,7 +240,7 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
     const pathToMove = pathsToMove[0]
     if (pathToMove === undefined) return Promise.resolve()
 
-    const outputPath = joinPath(this.directory, 'dist', basename(pathToMove))
+    const outputPath = joinPath(this.directory, relativePath(inputPath, pathToMove))
     await moveFile(pathToMove, outputPath, {overwrite: true})
     outputDebug(`Source map for ${this.localIdentifier} created: ${outputPath}`)
   }
@@ -377,6 +364,7 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
           this.specification.buildConfig.filePatterns,
           this.specification.buildConfig.ignoredFilePatterns,
         )
+      case 'hosted_app_home':
       case 'none':
         break
     }
@@ -384,7 +372,6 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
 
   async buildForBundle(options: ExtensionBuildOptions, bundleDirectory: string, outputId?: string) {
     this.outputPath = this.getOutputPathForDirectory(bundleDirectory, outputId)
-
     await this.build(options)
 
     const bundleInputPath = joinPath(bundleDirectory, this.getOutputFolderId(outputId))
@@ -414,8 +401,7 @@ export class ExtensionInstance<TConfiguration extends BaseConfigType = BaseConfi
 
   getOutputPathForDirectory(directory: string, outputId?: string) {
     const id = this.getOutputFolderId(outputId)
-    const outputFile = this.outputFileName === '' ? '' : joinPath('dist', this.outputFileName)
-    return joinPath(directory, id, outputFile)
+    return joinPath(directory, id, this.outputRelativePath)
   }
 
   get singleTarget() {
diff --git a/packages/app/src/cli/models/extensions/specification.ts b/packages/app/src/cli/models/extensions/specification.ts
index fe1545edbc8..a2ba6b65750 100644
--- a/packages/app/src/cli/models/extensions/specification.ts
+++ b/packages/app/src/cli/models/extensions/specification.ts
@@ -1,6 +1,7 @@
 import {ZodSchemaType, BaseConfigType, BaseSchema} from './schemas.js'
 import {ExtensionInstance} from './extension-instance.js'
 import {blocks} from '../../constants.js'
+import {ClientSteps} from '../../services/build/client-steps.js'
 
 import {Flag} from '../../utilities/developer-platform-client.js'
 import {AppConfiguration} from '../app/app.js'
@@ -60,6 +61,7 @@ export interface BuildAsset {
 type BuildConfig =
   | {mode: 'ui' | 'theme' | 'function' | 'tax_calculation' | 'none'}
   | {mode: 'copy_files'; filePatterns: string[]; ignoredFilePatterns?: string[]}
+
 /**
  * Extension specification with all the needed properties and methods to load an extension.
  */
@@ -73,9 +75,11 @@ export interface ExtensionSpecification<TConfiguration extends BaseConfigType =
   surface: string
   registrationLimit: number
   experience: ExtensionExperience
+  clientSteps?: ClientSteps
   buildConfig: BuildConfig
   dependency?: string
   graphQLType?: string
+  getOutputRelativePath?: (extension: ExtensionInstance<TConfiguration>) => string
   getBundleExtensionStdinContent?: (config: TConfiguration) => {main: string; assets?: Asset[]}
   deployConfig?: (
     config: TConfiguration,
@@ -207,6 +211,7 @@ export function createExtensionSpecification<TConfiguration extends BaseConfigTy
     experience: spec.experience ?? 'extension',
     uidStrategy: spec.uidStrategy ?? (spec.experience === 'configuration' ? 'single' : 'uuid'),
     getDevSessionUpdateMessages: spec.getDevSessionUpdateMessages,
+    clientSteps: spec.clientSteps,
     buildConfig: spec.buildConfig ?? {mode: 'none'},
   }
   const merged = {...defaults, ...spec}
@@ -255,6 +260,8 @@ export function createExtensionSpecification<TConfiguration extends BaseConfigTy
 export function createConfigExtensionSpecification<TConfiguration extends BaseConfigType = BaseConfigType>(spec: {
   identifier: string
   schema: ZodSchemaType<TConfiguration>
+  clientSteps?: ClientSteps
+  buildConfig?: BuildConfig
   appModuleFeatures?: (config?: TConfiguration) => ExtensionFeature[]
   transformConfig: TransformationConfig | CustomTransformationConfig
   uidStrategy?: UidStrategy
@@ -272,6 +279,8 @@ export function createConfigExtensionSpecification<TConfiguration extends BaseCo
     transformRemoteToLocal: resolveReverseAppConfigTransform(spec.schema, spec.transformConfig),
     experience: 'configuration',
     uidStrategy: spec.uidStrategy ?? 'single',
+    clientSteps: spec.clientSteps,
+    buildConfig: spec.buildConfig ?? {mode: 'none'},
     getDevSessionUpdateMessages: spec.getDevSessionUpdateMessages,
     patchWithAppDevURLs: spec.patchWithAppDevURLs,
   })
@@ -287,6 +296,7 @@ export function createContractBasedModuleSpecification<TConfiguration extends Ba
     identifier: spec.identifier,
     schema: zod.any({}) as unknown as ZodSchemaType<TConfiguration>,
     appModuleFeatures: spec.appModuleFeatures,
+    clientSteps: spec.clientSteps,
     buildConfig: spec.buildConfig ?? {mode: 'none'},
     uidStrategy: spec.uidStrategy,
     deployConfig: async (config, directory) => {
diff --git a/packages/app/src/cli/models/extensions/specifications/app_config_privacy_compliance_webhooks.ts b/packages/app/src/cli/models/extensions/specifications/app_config_privacy_compliance_webhooks.ts
index fbeada25f8c..3139ad3c0e6 100644
--- a/packages/app/src/cli/models/extensions/specifications/app_config_privacy_compliance_webhooks.ts
+++ b/packages/app/src/cli/models/extensions/specifications/app_config_privacy_compliance_webhooks.ts
@@ -77,13 +77,13 @@ function relativeUri(uri?: string, appUrl?: string) {
 }
 
 function getCustomersDeletionUri(webhooks: WebhooksConfig) {
-  return getComplianceUri(webhooks, 'customers/redact') || webhooks?.privacy_compliance?.customer_deletion_url
+  return getComplianceUri(webhooks, 'customers/redact') ?? webhooks?.privacy_compliance?.customer_deletion_url
 }
 
 function getCustomersDataRequestUri(webhooks: WebhooksConfig) {
-  return getComplianceUri(webhooks, 'customers/data_request') || webhooks?.privacy_compliance?.customer_data_request_url
+  return getComplianceUri(webhooks, 'customers/data_request') ?? webhooks?.privacy_compliance?.customer_data_request_url
 }
 
 function getShopDeletionUri(webhooks: WebhooksConfig) {
-  return getComplianceUri(webhooks, 'shop/redact') || webhooks?.privacy_compliance?.shop_deletion_url
+  return getComplianceUri(webhooks, 'shop/redact') ?? webhooks?.privacy_compliance?.shop_deletion_url
 }
diff --git a/packages/app/src/cli/models/extensions/specifications/checkout_post_purchase.ts b/packages/app/src/cli/models/extensions/specifications/checkout_post_purchase.ts
index 616adf80b73..cbae1290736 100644
--- a/packages/app/src/cli/models/extensions/specifications/checkout_post_purchase.ts
+++ b/packages/app/src/cli/models/extensions/specifications/checkout_post_purchase.ts
@@ -1,9 +1,11 @@
+import {ExtensionInstance} from '../extension-instance.js'
 import {BaseSchema, MetafieldSchema} from '../schemas.js'
 import {createExtensionSpecification} from '../specification.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 
 const dependency = '@shopify/post-purchase-ui-extensions'
 
+type CheckoutPostPurchaseConfigType = zod.infer<typeof CheckoutPostPurchaseSchema>
 const CheckoutPostPurchaseSchema = BaseSchema.extend({
   metafields: zod.array(MetafieldSchema).optional(),
 })
@@ -15,6 +17,8 @@ const checkoutPostPurchaseSpec = createExtensionSpecification({
   schema: CheckoutPostPurchaseSchema,
   appModuleFeatures: (_) => ['ui_preview', 'cart_url', 'esbuild', 'single_js_entry_path'],
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<CheckoutPostPurchaseConfigType>) =>
+    `dist/${extension.handle}.js`,
   deployConfig: async (config, _) => {
     return {metafields: config.metafields ?? []}
   },
diff --git a/packages/app/src/cli/models/extensions/specifications/checkout_ui_extension.ts b/packages/app/src/cli/models/extensions/specifications/checkout_ui_extension.ts
index f08dfd97c40..ab37ad6a44f 100644
--- a/packages/app/src/cli/models/extensions/specifications/checkout_ui_extension.ts
+++ b/packages/app/src/cli/models/extensions/specifications/checkout_ui_extension.ts
@@ -1,10 +1,12 @@
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema, MetafieldSchema} from '../schemas.js'
 import {loadLocalesConfig} from '../../../utilities/extensions/locales-configuration.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 
 const dependency = '@shopify/checkout-ui-extensions'
 
+type CheckoutConfigType = zod.infer<typeof CheckoutSchema>
 const CheckoutSchema = BaseSchema.extend({
   name: zod.string(),
   extension_points: zod.array(zod.string()).optional(),
@@ -22,6 +24,7 @@ const checkoutSpec = createExtensionSpecification({
   schema: CheckoutSchema,
   appModuleFeatures: (_) => ['ui_preview', 'cart_url', 'esbuild', 'single_js_entry_path', 'generates_source_maps'],
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<CheckoutConfigType>) => `dist/${extension.handle}.js`,
   deployConfig: async (config, directory) => {
     return {
       extension_points: config.extension_points,
diff --git a/packages/app/src/cli/models/extensions/specifications/function.ts b/packages/app/src/cli/models/extensions/specifications/function.ts
index ce6d2ec5a5d..c1f80ee796e 100644
--- a/packages/app/src/cli/models/extensions/specifications/function.ts
+++ b/packages/app/src/cli/models/extensions/specifications/function.ts
@@ -1,6 +1,7 @@
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema} from '../schemas.js'
 import {loadLocalesConfig} from '../../../utilities/extensions/locales-configuration.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 import {joinPath} from '@shopify/cli-kit/node/path'
 import {fileExists, readFile} from '@shopify/cli-kit/node/fs'
@@ -88,6 +89,8 @@ const functionSpec = createExtensionSpecification({
   schema: FunctionExtensionSchema,
   appModuleFeatures: (_) => ['function'],
   buildConfig: {mode: 'function'},
+  getOutputRelativePath: (extension: ExtensionInstance<FunctionConfigType>) =>
+    extension.configuration.build?.path ?? joinPath('dist', 'index.wasm'),
   deployConfig: async (config, directory, apiKey) => {
     let inputQuery: string | undefined
     const moduleId = randomUUID()
diff --git a/packages/app/src/cli/models/extensions/specifications/payments_app_extension.ts b/packages/app/src/cli/models/extensions/specifications/payments_app_extension.ts
index 33dfeda8b2e..e27aaab8655 100644
--- a/packages/app/src/cli/models/extensions/specifications/payments_app_extension.ts
+++ b/packages/app/src/cli/models/extensions/specifications/payments_app_extension.ts
@@ -69,6 +69,7 @@ const paymentExtensionSpec = createExtensionSpecification({
         )
       case CARD_PRESENT_TARGET:
         return cardPresentPaymentsAppExtensionDeployConfig(config as CardPresentPaymentsAppExtensionConfigType)
+      case undefined:
       default:
         return {}
     }
diff --git a/packages/app/src/cli/models/extensions/specifications/pos_ui_extension.ts b/packages/app/src/cli/models/extensions/specifications/pos_ui_extension.ts
index 33962306a24..2d9dc37b4ee 100644
--- a/packages/app/src/cli/models/extensions/specifications/pos_ui_extension.ts
+++ b/packages/app/src/cli/models/extensions/specifications/pos_ui_extension.ts
@@ -1,17 +1,22 @@
 import {getDependencyVersion} from '../../app/app.js'
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema} from '../schemas.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {BugError} from '@shopify/cli-kit/node/error'
 import {zod} from '@shopify/cli-kit/node/schema'
 
 const dependency = '@shopify/retail-ui-extensions'
 
+type PosUIConfigType = zod.infer<typeof PosUISchema>
+const PosUISchema = BaseSchema.extend({name: zod.string()})
+
 const posUISpec = createExtensionSpecification({
   identifier: 'pos_ui_extension',
   dependency,
-  schema: BaseSchema.extend({name: zod.string()}),
+  schema: PosUISchema,
   appModuleFeatures: (_) => ['ui_preview', 'esbuild', 'single_js_entry_path'],
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<PosUIConfigType>) => `dist/${extension.handle}.js`,
   deployConfig: async (config, directory) => {
     const result = await getDependencyVersion(dependency, directory)
     if (result === 'not_found') throw new BugError(`Dependency ${dependency} not found`)
diff --git a/packages/app/src/cli/models/extensions/specifications/product_subscription.ts b/packages/app/src/cli/models/extensions/specifications/product_subscription.ts
index ba807e409f6..2497a236130 100644
--- a/packages/app/src/cli/models/extensions/specifications/product_subscription.ts
+++ b/packages/app/src/cli/models/extensions/specifications/product_subscription.ts
@@ -1,10 +1,14 @@
 import {getDependencyVersion} from '../../app/app.js'
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema} from '../schemas.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {BugError} from '@shopify/cli-kit/node/error'
+import {zod} from '@shopify/cli-kit/node/schema'
 
 const dependency = '@shopify/admin-ui-extensions'
 
+type ProductSubscriptionConfigType = zod.infer<typeof BaseSchema>
+
 const productSubscriptionSpec = createExtensionSpecification({
   identifier: 'product_subscription',
   additionalIdentifiers: ['subscription_management'],
@@ -13,6 +17,7 @@ const productSubscriptionSpec = createExtensionSpecification({
   schema: BaseSchema,
   appModuleFeatures: (_) => ['ui_preview', 'esbuild', 'single_js_entry_path'],
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<ProductSubscriptionConfigType>) => `dist/${extension.handle}.js`,
   deployConfig: async (_, directory) => {
     const result = await getDependencyVersion(dependency, directory)
     if (result === 'not_found') throw new BugError(`Dependency ${dependency} not found`)
diff --git a/packages/app/src/cli/models/extensions/specifications/tax_calculation.ts b/packages/app/src/cli/models/extensions/specifications/tax_calculation.ts
index 1e97e577bb6..e7d09509939 100644
--- a/packages/app/src/cli/models/extensions/specifications/tax_calculation.ts
+++ b/packages/app/src/cli/models/extensions/specifications/tax_calculation.ts
@@ -1,11 +1,13 @@
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema, MetafieldSchema} from '../schemas.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 
 const CartLinePropertySchema = zod.object({
   key: zod.string(),
 })
 
+type TaxCalculationsConfigType = zod.infer<typeof TaxCalculationsSchema>
 const TaxCalculationsSchema = BaseSchema.extend({
   production_api_base_url: zod.string(),
   benchmark_api_base_url: zod.string().optional(),
@@ -29,6 +31,7 @@ const spec = createExtensionSpecification({
   schema: TaxCalculationsSchema,
   appModuleFeatures: (_) => [],
   buildConfig: {mode: 'tax_calculation'},
+  getOutputRelativePath: (extension: ExtensionInstance<TaxCalculationsConfigType>) => `dist/${extension.handle}.js`,
   deployConfig: async (config, _) => {
     return {
       production_api_base_url: config.production_api_base_url,
diff --git a/packages/app/src/cli/models/extensions/specifications/ui_extension.ts b/packages/app/src/cli/models/extensions/specifications/ui_extension.ts
index f3e04cbeab9..8f8dc83d02a 100644
--- a/packages/app/src/cli/models/extensions/specifications/ui_extension.ts
+++ b/packages/app/src/cli/models/extensions/specifications/ui_extension.ts
@@ -36,6 +36,7 @@ export interface BuildManifest {
 
 const missingExtensionPointsMessage = 'No extension targets defined, add a `targeting` field to your configuration'
 
+type UIExtensionConfigType = zod.infer<typeof UIExtensionSchema>
 export const UIExtensionSchema = BaseSchema.extend({
   name: zod.string(),
   type: zod.literal('ui_extension'),
@@ -102,6 +103,7 @@ const uiExtensionSpec = createExtensionSpecification({
   dependency,
   schema: UIExtensionSchema,
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<UIExtensionConfigType>) => `dist/${extension.handle}.js`,
   appModuleFeatures: (config) => {
     const basic: ExtensionFeature[] = ['ui_preview', 'esbuild', 'generates_source_maps']
     const needsCart =
diff --git a/packages/app/src/cli/models/extensions/specifications/web_pixel_extension.ts b/packages/app/src/cli/models/extensions/specifications/web_pixel_extension.ts
index 298a18d876b..e512e66e5f4 100644
--- a/packages/app/src/cli/models/extensions/specifications/web_pixel_extension.ts
+++ b/packages/app/src/cli/models/extensions/specifications/web_pixel_extension.ts
@@ -1,5 +1,6 @@
 import {createExtensionSpecification} from '../specification.js'
 import {BaseSchema} from '../schemas.js'
+import {ExtensionInstance} from '../extension-instance.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 import {AbortError} from '@shopify/cli-kit/node/error'
 import {fileSize} from '@shopify/cli-kit/node/fs'
@@ -10,6 +11,7 @@ const BUNDLE_SIZE_LIMIT = BUNDLE_SIZE_LIMIT_KB * kilobytes
 
 const dependency = '@shopify/web-pixels-extension'
 
+type WebPixelConfigType = zod.infer<typeof WebPixelSchema>
 const WebPixelSchema = BaseSchema.extend({
   runtime_context: zod.string(),
   version: zod.string().optional(),
@@ -32,6 +34,7 @@ const webPixelSpec = createExtensionSpecification({
   schema: WebPixelSchema,
   appModuleFeatures: (_) => ['esbuild', 'single_js_entry_path'],
   buildConfig: {mode: 'ui'},
+  getOutputRelativePath: (extension: ExtensionInstance<WebPixelConfigType>) => `dist/${extension.handle}.js`,
   deployConfig: async (config, _) => {
     return {
       runtime_context: config.runtime_context,
diff --git a/packages/app/src/cli/services/build/client-steps.test.ts b/packages/app/src/cli/services/build/client-steps.test.ts
new file mode 100644
index 00000000000..3c33e94891b
--- /dev/null
+++ b/packages/app/src/cli/services/build/client-steps.test.ts
@@ -0,0 +1,76 @@
+import {executeStep, BuildContext, LifecycleStep} from './client-steps.js'
+import * as stepsIndex from './steps/index.js'
+import {ExtensionInstance} from '../../models/extensions/extension-instance.js'
+import {beforeEach, describe, expect, test, vi} from 'vitest'
+
+vi.mock('./steps/index.js')
+
+describe('executeStep', () => {
+  let mockContext: BuildContext
+
+  beforeEach(() => {
+    mockContext = {
+      extension: {
+        directory: '/test/dir',
+        outputPath: '/test/output/index.js',
+      } as ExtensionInstance,
+      options: {
+        stdout: {write: vi.fn()} as any,
+        stderr: {write: vi.fn()} as any,
+        app: {} as any,
+        environment: 'production' as const,
+      },
+      stepResults: new Map(),
+    }
+  })
+
+  const step: LifecycleStep = {
+    id: 'test-step',
+    name: 'Test Step',
+    type: 'include_assets',
+    config: {},
+  }
+
+  describe('success', () => {
+    test('returns a successful StepResult with output', async () => {
+      vi.mocked(stepsIndex.executeStepByType).mockResolvedValue({filesCopied: 3})
+
+      const result = await executeStep(step, mockContext)
+
+      expect(result.id).toBe('test-step')
+      expect(result.success).toBe(true)
+      if (result.success) expect(result.output).toEqual({filesCopied: 3})
+      expect(result.duration).toBeGreaterThanOrEqual(0)
+    })
+
+    test('logs step execution to stdout', async () => {
+      vi.mocked(stepsIndex.executeStepByType).mockResolvedValue({})
+
+      await executeStep(step, mockContext)
+
+      expect(mockContext.options.stdout.write).toHaveBeenCalledWith('Executing step: Test Step\n')
+    })
+  })
+
+  describe('failure', () => {
+    test('throws a wrapped error when the step fails', async () => {
+      vi.mocked(stepsIndex.executeStepByType).mockRejectedValue(new Error('something went wrong'))
+
+      await expect(executeStep(step, mockContext)).rejects.toThrow(
+        'Build step "Test Step" failed: something went wrong',
+      )
+    })
+
+    test('returns a failure result and logs a warning when continueOnError is true', async () => {
+      vi.mocked(stepsIndex.executeStepByType).mockRejectedValue(new Error('something went wrong'))
+
+      const result = await executeStep({...step, continueOnError: true}, mockContext)
+
+      expect(result.success).toBe(false)
+      if (!result.success) expect(result.error?.message).toBe('something went wrong')
+      expect(mockContext.options.stderr.write).toHaveBeenCalledWith(
+        'Warning: Step "Test Step" failed but continuing: something went wrong\n',
+      )
+    })
+  })
+})
diff --git a/packages/app/src/cli/services/build/client-steps.ts b/packages/app/src/cli/services/build/client-steps.ts
new file mode 100644
index 00000000000..b84b6bbc35a
--- /dev/null
+++ b/packages/app/src/cli/services/build/client-steps.ts
@@ -0,0 +1,103 @@
+import {executeStepByType} from './steps/index.js'
+import type {ExtensionInstance} from '../../models/extensions/extension-instance.js'
+import type {ExtensionBuildOptions} from './extension.js'
+
+/**
+ * LifecycleStep represents a single step in the client-side build pipeline.
+ * Pure configuration object — execution logic is separate (router pattern).
+ */
+export interface LifecycleStep {
+  /** Unique identifier, used as the key in the stepResults map */
+  readonly id: string
+
+  /** Human-readable name for logging */
+  readonly name: string
+
+  /** Step type (determines which executor handles it) */
+  readonly type:
+    | 'include_assets'
+    | 'build_theme'
+    | 'bundle_theme'
+    | 'bundle_ui'
+    | 'copy_static_assets'
+    | 'build_function'
+    | 'create_tax_stub'
+
+  /** Step-specific configuration */
+  readonly config: {[key: string]: unknown}
+
+  /** Whether to continue on error (default: false) */
+  readonly continueOnError?: boolean
+}
+
+/**
+ * A group of steps scoped to a specific lifecycle phase.
+ * Allows executing only the steps relevant to a given lifecycle (e.g. 'deploy').
+ */
+interface ClientLifecycleGroup {
+  readonly lifecycle: 'deploy'
+  readonly steps: ReadonlyArray<LifecycleStep>
+}
+
+/**
+ * The full client steps configuration for an extension.
+ * Replaces the old buildConfig contract.
+ */
+export type ClientSteps = ReadonlyArray<ClientLifecycleGroup>
+
+/**
+ * Context passed through the step pipeline.
+ * Each step can read from and write to the context.
+ */
+export interface BuildContext {
+  readonly extension: ExtensionInstance
+  readonly options: ExtensionBuildOptions
+  readonly stepResults: Map<string, StepResult>
+}
+
+type StepResult = {
+  readonly id: string
+  readonly duration: number
+} & (
+  | {
+      readonly success: false
+      readonly error: Error
+    }
+  | {
+      readonly success: true
+      readonly output: never
+    }
+)
+
+/**
+ * Executes a single client step with error handling.
+ */
+export async function executeStep(step: LifecycleStep, context: BuildContext): Promise<StepResult> {
+  const startTime = Date.now()
+
+  try {
+    context.options.stdout.write(`Executing step: ${step.name}\n`)
+    const output = await executeStepByType(step, context)
+
+    return {
+      id: step.id,
+      success: true,
+      duration: Date.now() - startTime,
+      output: output as never,
+    }
+  } catch (error) {
+    const stepError = error as Error
+
+    if (step.continueOnError) {
+      context.options.stderr.write(`Warning: Step "${step.name}" failed but continuing: ${stepError.message}\n`)
+      return {
+        id: step.id,
+        success: false,
+        duration: Date.now() - startTime,
+        error: stepError,
+      }
+    }
+
+    throw new Error(`Build step "${step.name}" failed: ${stepError.message}`)
+  }
+}
diff --git a/packages/app/src/cli/services/build/extension.ts b/packages/app/src/cli/services/build/extension.ts
index 21072a23f66..d1000080051 100644
--- a/packages/app/src/cli/services/build/extension.ts
+++ b/packages/app/src/cli/services/build/extension.ts
@@ -150,8 +150,7 @@ export async function buildFunctionExtension(
 
   try {
     const bundlePath = extension.outputPath
-    const relativeBuildPath =
-      (extension as ExtensionInstance<FunctionConfigType>).configuration.build?.path ?? joinPath('dist', 'index.wasm')
+    const relativeBuildPath = extension.specification.getOutputRelativePath?.(extension) ?? ''
 
     extension.outputPath = joinPath(extension.directory, relativeBuildPath)
 
diff --git a/packages/app/src/cli/services/build/steps/index.ts b/packages/app/src/cli/services/build/steps/index.ts
new file mode 100644
index 00000000000..846a4d4147b
--- /dev/null
+++ b/packages/app/src/cli/services/build/steps/index.ts
@@ -0,0 +1,27 @@
+import type {LifecycleStep, BuildContext} from '../client-steps.js'
+
+/**
+ * Routes step execution to the appropriate handler based on step type.
+ * This implements the Command Pattern router, dispatching to type-specific executors.
+ *
+ * @param step - The build step configuration
+ * @param context - The build context
+ * @returns The output from the step execution
+ * @throws Error if the step type is not implemented or unknown
+ */
+export async function executeStepByType(step: LifecycleStep, _context: BuildContext): Promise<unknown> {
+  switch (step.type) {
+    // Future step types (not implemented yet):
+    case 'include_assets':
+    case 'build_theme':
+    case 'bundle_theme':
+    case 'bundle_ui':
+    case 'copy_static_assets':
+    case 'build_function':
+    case 'create_tax_stub':
+      throw new Error(`Build step type "${step.type}" is not yet implemented.`)
+
+    default:
+      throw new Error(`Unknown build step type: ${(step as {type: string}).type}`)
+  }
+}
diff --git a/packages/app/src/cli/services/dev/extension/server/middlewares.ts b/packages/app/src/cli/services/dev/extension/server/middlewares.ts
index 7bf8116bc11..9cec5a369c4 100644
--- a/packages/app/src/cli/services/dev/extension/server/middlewares.ts
+++ b/packages/app/src/cli/services/dev/extension/server/middlewares.ts
@@ -5,7 +5,7 @@ import {getHTML} from '../templates.js'
 import {getWebSocketUrl} from '../../extension.js'
 import {fileExists, isDirectory, readFile, findPathUp} from '@shopify/cli-kit/node/fs'
 import {IncomingMessage, ServerResponse, sendRedirect, send} from 'h3'
-import {joinPath, extname, moduleDirectory} from '@shopify/cli-kit/node/path'
+import {joinPath, dirname, extname, moduleDirectory} from '@shopify/cli-kit/node/path'
 import {outputDebug} from '@shopify/cli-kit/node/output'
 
 export function corsMiddleware(_request: IncomingMessage, response: ServerResponse, next: (err?: Error) => unknown) {
@@ -90,7 +90,7 @@ export function getExtensionAssetMiddleware({devOptions, getExtensions}: GetExte
     const bundlePath = devOptions.appWatcher.buildOutputPath
     const extensionOutputPath = extension.getOutputPathForDirectory(bundlePath)
 
-    const buildDirectory = extensionOutputPath.replace(extension.outputFileName, '')
+    const buildDirectory = dirname(extensionOutputPath)
 
     return fileServerMiddleware(request, response, next, {
       filePath: joinPath(buildDirectory, assetPath),