fix: correctly parse package name for scoped packages

server/api/registry/analysis/[...pkg].get.ts

@@ -41,7 +41,7 @@ export default defineCachedEventHandler(
 
     try {
       const { packageName, version } = v.parse(PackageRouteParamsSchema, {
-        packageName: rawPackageName,
+        packageName: decodeURIComponent(rawPackageName),
         version: rawVersion,
       })
 

server/api/registry/install-size/[...pkg].get.ts

@@ -18,7 +18,7 @@ export default defineCachedEventHandler(
 
     try {
       const { packageName, version: requestedVersion } = v.parse(PackageRouteParamsSchema, {
-        packageName: rawPackageName,
+        packageName: decodeURIComponent(rawPackageName),
         version: rawVersion,
       })
 

test/e2e/interactions.spec.ts

@@ -47,6 +47,48 @@ test.describe('Compare Page', () => {
     const noDepColumn = grid.locator('.comparison-cell-nodep')
     await expect(noDepColumn).toBeVisible()
   })
+
+  test('loads install-size data for a scoped package', async ({ page, goto }) => {
+    // Intercept the internal API call the browser makes for install-size.
+    // The browser will request /api/registry/install-size/@nuxt%2Fkit (encoded slash).
+    // Before the fix this would fail to parse and return an error; after it returns 200.
+    const installSizeResponse = page.waitForResponse(
+      res =>
+        res.url().includes('/api/registry/install-size/') &&
+        res.url().includes('nuxt') &&
+        res.request().method() === 'GET',
+      { timeout: 20_000 },
+    )
+
+    await goto('/compare?packages=@nuxt/kit,vue', { waitUntil: 'hydration' })
+
+    const response = await installSizeResponse
+    expect(response.status()).toBe(200)
+
+    const body = await response.json()
+    // The API should return a valid install size object, not an error
+    expect(body).toHaveProperty('selfSize')
+    expect(body).toHaveProperty('totalSize')
+  })
+
+  test('loads analysis data for a scoped package', async ({ page, goto }) => {
+    const analysisResponse = page.waitForResponse(
+      res =>
+        res.url().includes('/api/registry/analysis/') &&
+        res.url().includes('nuxt') &&
+        res.request().method() === 'GET',
+      { timeout: 20_000 },
+    )
+
+    await goto('/compare?packages=@nuxt/kit,vue', { waitUntil: 'hydration' })
+
+    const response = await analysisResponse
+    expect(response.status()).toBe(200)
+
+    const body = await response.json()
+    expect(body).toHaveProperty('package', '@nuxt/kit')
+    expect(body).toHaveProperty('moduleFormat', 'esm')
+  })
 })
 
 test.describe('Search Pages', () => {

test/unit/server/utils/parse-package-params.spec.ts

@@ -0,0 +1,53 @@
+import { describe, expect, it } from 'vitest'
+import { parsePackageParams } from '#server/utils/parse-package-params'
+
+describe('parsePackageParams', () => {
+  describe('unscoped packages', () => {
+    it('parses package name without version', () => {
+      const segments = ['vue']
+      const result = parsePackageParams(segments)
+      expect(result).toEqual({
+        rawPackageName: 'vue',
+        rawVersion: undefined,
+      })
+    })
+
+    it('parses package name with version', () => {
+      const segments = ['vue', 'v', '3.4.0']
+      const result = parsePackageParams(segments)
+      expect(result).toEqual({
+        rawPackageName: 'vue',
+        rawVersion: '3.4.0',
+      })
+    })
+
+    it('parses package name with prerelease version', () => {
+      const segments = ['nuxt', 'v', '4.0.0-rc.1']
+      const result = parsePackageParams(segments)
+      expect(result).toEqual({
+        rawPackageName: 'nuxt',
+        rawVersion: '4.0.0-rc.1',
+      })
+    })
+  })
+
+  describe('scoped packages', () => {
+    it('parses scoped package name without version', () => {
+      const segments = ['@nuxt', 'kit']
+      const result = parsePackageParams(segments)
+      expect(result).toEqual({
+        rawPackageName: '@nuxt/kit',
+        rawVersion: undefined,
+      })
+    })
+
+    it('parses scoped package name with version', () => {
+      const segments = ['@nuxt', 'kit', 'v', '1.0.0']
+      const result = parsePackageParams(segments)
+      expect(result).toEqual({
+        rawPackageName: '@nuxt/kit',
+        rawVersion: '1.0.0',
+      })
+    })
+  })
+})