diff --git a/napi/angular-compiler/package.json b/napi/angular-compiler/package.json
index 7039d5dd6..b441d4083 100644
--- a/napi/angular-compiler/package.json
+++ b/napi/angular-compiler/package.json
@@ -75,6 +75,7 @@
     "@playwright/test": "^1.58.0",
     "@types/node": "catalog:",
     "oxfmt": "catalog:",
+    "sass": "^1.93.2",
     "typescript": "catalog:",
     "vite": "catalog:",
     "vitest": "catalog:"
diff --git a/napi/angular-compiler/test/style-deps-hmr.test.ts b/napi/angular-compiler/test/style-deps-hmr.test.ts
new file mode 100644
index 000000000..e0286c892
--- /dev/null
+++ b/napi/angular-compiler/test/style-deps-hmr.test.ts
@@ -0,0 +1,203 @@
+/**
+ * Tests HMR for transitive style dependencies.
+ *
+ * A component styleUrl compiled through a CSS preprocessor can pull in shared
+ * files (Sass partials via `@use` / `@import` / `meta.load-css`, Less imports,
+ * ...). `preprocessCSS` reports them in `deps`; the plugin must invalidate the
+ * compiled style and dispatch component HMR when one of them changes, for every
+ * component whose style is built on top of it.
+ */
+import { mkdirSync, mkdtempSync, realpathSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+
+import type { Plugin, ModuleNode, HmrContext } from 'vite'
+import { resolveConfig } from 'vite'
+import { afterAll, beforeAll, describe, it, expect, vi } from 'vitest'
+
+import { angular } from '../vite-plugin/index.js'
+
+let tempDir: string
+let appDir: string
+let sharedScssPath: string
+let firstComponentPath: string
+let secondComponentPath: string
+
+const componentSource = (selector: string, styleUrl: string) => `
+  import { Component } from '@angular/core';
+
+  @Component({
+    selector: '${selector}',
+    template: '<h1>Hello</h1>',
+    styleUrls: ['./${styleUrl}'],
+  })
+  export class AppComponent {}
+`
+
+beforeAll(() => {
+  // realpath: Sass canonicalizes loaded URLs (macOS /var -> /private/var),
+  // and watcher events use canonical paths too.
+  tempDir = realpathSync(mkdtempSync(join(tmpdir(), 'style-deps-hmr-test-')))
+  appDir = join(tempDir, 'src', 'app')
+  mkdirSync(appDir, { recursive: true })
+
+  sharedScssPath = join(appDir, '_shared.scss')
+  firstComponentPath = join(appDir, 'first.component.ts')
+  secondComponentPath = join(appDir, 'second.component.ts')
+
+  writeFileSync(sharedScssPath, 'h1 { color: red; }')
+  writeFileSync(join(appDir, 'first.component.scss'), "@use './shared';")
+  writeFileSync(join(appDir, 'second.component.scss'), "@use './shared';")
+  writeFileSync(firstComponentPath, componentSource('app-first', 'first.component.scss'))
+  writeFileSync(secondComponentPath, componentSource('app-second', 'second.component.scss'))
+})
+
+afterAll(() => {
+  rmSync(tempDir, { recursive: true, force: true })
+})
+
+function getAngularPlugin() {
+  const plugin = angular({ liveReload: true }).find(
+    (candidate) => candidate.name === '@oxc-angular/vite',
+  )
+
+  if (!plugin) {
+    throw new Error('Failed to find @oxc-angular/vite plugin')
+  }
+
+  return plugin
+}
+
+function createMockServer() {
+  const wsMessages: any[] = []
+
+  return {
+    watcher: {
+      unwatch: vi.fn(),
+      on: vi.fn(),
+      emit: vi.fn(),
+    },
+    ws: {
+      send(msg: any) {
+        wsMessages.push(msg)
+      },
+      on: vi.fn(),
+    },
+    moduleGraph: {
+      getModuleById: vi.fn(() => null),
+      invalidateModule: vi.fn(),
+    },
+    middlewares: {
+      use: vi.fn(),
+    },
+    config: {
+      root: tempDir,
+    },
+    _wsMessages: wsMessages,
+  }
+}
+
+function createMockHmrContext(file: string, server: any): HmrContext {
+  return {
+    file,
+    timestamp: Date.now(),
+    modules: [{ id: file } as ModuleNode],
+    read: async () => '',
+    server,
+  } as HmrContext
+}
+
+async function callPluginHook<TArgs extends unknown[], TResult>(
+  hook:
+    | {
+        handler: (...args: TArgs) => TResult
+      }
+    | ((...args: TArgs) => TResult)
+    | undefined,
+  ...args: TArgs
+): Promise<TResult | undefined> {
+  if (!hook) return undefined
+  if (typeof hook === 'function') return hook(...args)
+  return hook.handler(...args)
+}
+
+async function setupPluginWithServer(plugin: Plugin) {
+  const mockServer = createMockServer()
+
+  await callPluginHook(
+    plugin.config as Plugin['config'],
+    {} as any,
+    {
+      command: 'serve',
+      mode: 'development',
+    } as any,
+  )
+
+  // A real resolved config: preprocessCSS needs one to run Sass and report
+  // the partials it loaded in `deps`.
+  const resolved = await resolveConfig(
+    { configFile: false, root: tempDir, logLevel: 'silent' },
+    'serve',
+  )
+  await callPluginHook(plugin.configResolved as Plugin['configResolved'], resolved as any)
+
+  if (typeof plugin.configureServer === 'function') {
+    await (plugin.configureServer as Function)(mockServer)
+  }
+
+  ;(mockServer as any).__angularWatchTemplate = () => {}
+
+  return mockServer
+}
+
+async function transformComponent(plugin: Plugin, source: string, path: string) {
+  if (!plugin.transform || typeof plugin.transform === 'function') {
+    throw new Error('Expected plugin transform handler')
+  }
+
+  await plugin.transform.handler.call({ error() {}, warn() {} } as any, source, path)
+}
+
+describe('handleHotUpdate for transitive style dependencies', () => {
+  it('dispatches HMR to every component whose style uses a changed Sass partial', async () => {
+    const plugin = getAngularPlugin()
+    const mockServer = await setupPluginWithServer(plugin)
+
+    await transformComponent(
+      plugin,
+      componentSource('app-first', 'first.component.scss'),
+      firstComponentPath,
+    )
+    await transformComponent(
+      plugin,
+      componentSource('app-second', 'second.component.scss'),
+      secondComponentPath,
+    )
+
+    const ctx = createMockHmrContext(sharedScssPath, mockServer)
+    const result = await (plugin.handleHotUpdate as Function).call(plugin, ctx)
+
+    // Handled by the plugin: no modules left for Vite's default pipeline.
+    expect(result).toEqual([])
+
+    // Both owning components received a component-update event.
+    const updates = mockServer._wsMessages.filter(
+      (msg) => msg?.event === 'angular:component-update',
+    )
+    const updatedIds = updates.map((msg) => decodeURIComponent(msg.data.id))
+    expect(updatedIds.some((id) => id.startsWith(firstComponentPath))).toBe(true)
+    expect(updatedIds.some((id) => id.startsWith(secondComponentPath))).toBe(true)
+  })
+
+  it('leaves untracked stylesheets to Vite', async () => {
+    const plugin = getAngularPlugin()
+    const mockServer = await setupPluginWithServer(plugin)
+
+    const untracked = join(appDir, 'not-a-dep.scss')
+    writeFileSync(untracked, 'h2 { color: blue; }')
+    const ctx = createMockHmrContext(untracked, mockServer)
+    const result = await (plugin.handleHotUpdate as Function).call(plugin, ctx)
+
+    expect(result).toBe(ctx.modules)
+  })
+})
diff --git a/napi/angular-compiler/vite-plugin/index.ts b/napi/angular-compiler/vite-plugin/index.ts
index 31df1f320..ae54d182a 100644
--- a/napi/angular-compiler/vite-plugin/index.ts
+++ b/napi/angular-compiler/vite-plugin/index.ts
@@ -245,6 +245,14 @@ export function angular(options: PluginOptions = {}): Plugin[] {
   // Cache for resolved resources
   const resourceCache = new Map<string, string>()
 
+  // Preprocessor dependencies of each compiled style (Sass partials pulled in
+  // through `@use`/`@import`/`meta.load-css`, Less imports, ...), plus the
+  // reverse map from each dependency to the styles compiled from it, so that
+  // editing a shared partial invalidates and re-dispatches every component
+  // style built on top of it.
+  const styleDepsCache = new Map<string, string[]>()
+  const styleDepOwners = new Map<string, Set<string>>()
+
   // Component IDs (`filePath@ClassName`) queued for HMR delivery. Populated by
   // `handleHotUpdate` when an external resource or inline template/style change
   // is detected, and consumed by the `@ng/component` HTTP endpoint, which reads
@@ -336,6 +344,10 @@ export function angular(options: PluginOptions = {}): Plugin[] {
             try {
               const processed = await preprocessCSS(content, stylePath, resolvedConfig as any)
               content = processed.code
+              styleDepsCache.set(
+                stylePath,
+                processed.deps ? Array.from(processed.deps, (dep) => normalizePath(dep)) : [],
+              )
             } catch (e) {
               console.warn(`Failed to preprocess style: ${stylePath}`, e)
             }
@@ -346,6 +358,16 @@ export function angular(options: PluginOptions = {}): Plugin[] {
           continue
         }
       }
+
+      const normalizedStylePath = normalizePath(stylePath)
+      for (const dep of styleDepsCache.get(stylePath) ?? []) {
+        if (dep === normalizedStylePath) continue
+        dependencies.push(dep)
+        let owners = styleDepOwners.get(dep)
+        if (!owners) styleDepOwners.set(dep, (owners = new Set()))
+        owners.add(stylePath)
+      }
+
       styles[styleUrl] = [content]
     }
 
@@ -834,9 +856,27 @@ export function angular(options: PluginOptions = {}): Plugin[] {
         // Vite's default CSS HMR pipeline so PostCSS/Tailwind etc. still
         // process them.
         if (/\.(html?|css|scss|sass|less)$/.test(ctx.file)) {
+          // Shared preprocessor dependency (e.g. a Sass partial): rebuild every
+          // style compiled from it and HMR each owning component.
+          if (styleDepOwners.has(normalizedFile)) {
+            let handled = false
+            for (const stylePath of styleDepOwners.get(normalizedFile)!) {
+              resourceCache.delete(stylePath)
+              styleDepsCache.delete(stylePath)
+              const componentFile = resourceToComponent.get(normalizePath(stylePath))
+              if (componentFile && dispatchAllComponentsInFile(componentFile)) {
+                debugHmr('style dep HMR: %s -> %s -> %s', normalizedFile, stylePath, componentFile)
+                handled = true
+              }
+            }
+            if (handled) {
+              return []
+            }
+          }
           if (resourceToComponent.has(normalizedFile)) {
             const componentFile = resourceToComponent.get(normalizedFile)!
             resourceCache.delete(normalizedFile)
+            styleDepsCache.delete(ctx.file)
             // resourceToComponent only tracks one owner per resource; if a
             // templateUrl/styleUrl is shared across multiple components in
             // the same file, only the registered owner receives HMR.
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0fd9c8b37..84eb3e32c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -90,6 +90,9 @@ importers:
       oxfmt:
         specifier: 'catalog:'
         version: 0.60.0
+      sass:
+        specifier: ^1.93.2
+        version: 1.101.7
       typescript:
         specifier: 'catalog:'
         version: 6.0.3