fix: rewrite {version}/assets/ requests to the sidecar's flat assets/ lane

Explorer requests v49+ scene bundles by their digest-bearing file name under
the CDN's shared {version}/assets/ prefix (unity-explorer#9442). abgen serves
those files through its flat /assets/{file} lane (bundle-index lookup) but has
no version-prefixed route, so the proxy strips the version segment on the way
through. Drop once abgen serves GET /{version}/assets/{file} natively.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dalkia

packages/@dcl/sdk-commands/src/commands/start/server/asset-bundles-proxy.ts

@@ -39,7 +39,17 @@ export function setupAssetBundlesProxy(
     delete requestHeaders['content-length']
     delete requestHeaders['accept-encoding']
 
-    const response = await components.fetch.fetch(`${sidecarUrl}/${ctx.params.path}${ctx.url.search}`, {
+    // The route pattern types :path+ as string[], but the runtime hands it over as one string.
+    const rawPath = Array.isArray(ctx.params.path) ? ctx.params.path.join('/') : ctx.params.path
+
+    // Explorer requests v49+ scene bundles by their digest-bearing file name under the
+    // CDN's shared {version}/assets/ prefix (unity-explorer#9442). The sidecar serves
+    // those same files through its flat /assets/{file} lane (bundle-index lookup) but
+    // has no version-prefixed route, so strip the version segment on the way through.
+    // TODO: drop once abgen serves GET /{version}/assets/{file} natively.
+    const path = rawPath.replace(/^v\d+\/assets\//, 'assets/')
+
+    const response = await components.fetch.fetch(`${sidecarUrl}/${path}${ctx.url.search}`, {
       headers: requestHeaders,
       method,
       body: method === 'GET' || method === 'HEAD' ? undefined : (ctx.request.body as any),

test/sdk-commands/commands/start/asset-bundles-proxy.spec.ts

@@ -68,6 +68,18 @@ describe('start/server/asset-bundles-proxy', () => {
     await expect(readBody(response.body)).resolves.toBe('bundle-bytes')
   })
 
+  it('rewrites the version-prefixed assets/ shape to the flat assets/ lane the sidecar serves', async () => {
+    const { fetch, dispatch } = makeProxy(() => 'http://127.0.0.1:53211')
+    fetch.mockResolvedValue(new Response('bundle-bytes', { status: 200 }))
+
+    await dispatch('GET', 'v49/assets/b64-abc_7580fefaf1c77b8b771687a8a4f86063_mac')
+
+    expect(fetch).toHaveBeenCalledWith(
+      'http://127.0.0.1:53211/assets/b64-abc_7580fefaf1c77b8b771687a8a4f86063_mac',
+      expect.anything()
+    )
+  })
+
   it('forwards non-GET methods with their body and the sidecar status', async () => {
     const { fetch, dispatch } = makeProxy(() => 'http://127.0.0.1:53211')
     fetch.mockResolvedValue(new Response('nope', { status: 404 }))