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feat: add pre-built compression and code splitting for frontend assets #2705

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feat: add pre-built compression and code splitting for frontend assets
Sumeet213 Dec 1, 2025
6f45e56
Merge branch 'main' into feat/prebuilt-compression
hayescode Dec 4, 2025
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38 changes: 36 additions & 2 deletions backend/chainlit/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -275,37 +275,71 @@ async def serve_public_file(
raise HTTPException(status_code=404, detail="File not found")


def get_precompressed_response(
file_path: Path, accept_encoding: str
) -> Optional[FileResponse]:
content_type = mimetypes.guess_type(str(file_path))[0] or "application/octet-stream"

if "br" in accept_encoding:
br_path = file_path.with_suffix(file_path.suffix + ".br")
if br_path.is_file():
return FileResponse(
br_path,
media_type=content_type,
headers={"Content-Encoding": "br", "Vary": "Accept-Encoding"},
)

if "gzip" in accept_encoding:
gz_path = file_path.with_suffix(file_path.suffix + ".gz")
if gz_path.is_file():
return FileResponse(
gz_path,
media_type=content_type,
headers={"Content-Encoding": "gzip", "Vary": "Accept-Encoding"},
)

return None
Comment on lines +283 to +301
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@cubic-dev-ai cubic-dev-ai bot Dec 4, 2025 •
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P2: Accept-Encoding quality values are ignored, so a client that explicitly disallows gzip/Brotli (q=0) will still receive that encoding. Parse the header and only serve a precompressed file when the requested encoding’s q-value is greater than 0.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At backend/chainlit/server.py, line 283:

<comment>`Accept-Encoding` quality values are ignored, so a client that explicitly disallows gzip/Brotli (q=0) will still receive that encoding. Parse the header and only serve a precompressed file when the requested encoding’s q-value is greater than 0.</comment>

<file context>
@@ -275,37 +275,71 @@ async def serve_public_file(
+) -&gt; Optional[FileResponse]:
+    content_type = mimetypes.guess_type(str(file_path))[0] or &quot;application/octet-stream&quot;
+
+    if &quot;br&quot; in accept_encoding:
+        br_path = file_path.with_suffix(file_path.suffix + &quot;.br&quot;)
+        if br_path.is_file():
</file context>
Suggested change
if "br" in accept_encoding:
br_path = file_path.with_suffix(file_path.suffix + ".br")
if br_path.is_file():
return FileResponse(
br_path,
media_type=content_type,
headers={"Content-Encoding": "br", "Vary": "Accept-Encoding"},
)
if "gzip" in accept_encoding:
gz_path = file_path.with_suffix(file_path.suffix + ".gz")
if gz_path.is_file():
return FileResponse(
gz_path,
media_type=content_type,
headers={"Content-Encoding": "gzip", "Vary": "Accept-Encoding"},
)
return None
encodings: dict[str, float] = {}
for value in accept_encoding.lower().split(","):
token = value.strip()
if not token:
continue
parts = token.split(";")
encoding = parts[0]
q = 1.0
for part in parts[1:]:
if part.strip().startswith("q="):
try:
q = float(part.split("=", 1)[1])
except ValueError:
q = 0.0
encodings[encoding] = q
if encodings.get("br", 0) > 0:
br_path = file_path.with_suffix(file_path.suffix + ".br")
if br_path.is_file():
return FileResponse(
br_path,
media_type=content_type,
headers={"Content-Encoding": "br", "Vary": "Accept-Encoding"},
)
if encodings.get("gzip", 0) > 0:
gz_path = file_path.with_suffix(file_path.suffix + ".gz")
if gz_path.is_file():
return FileResponse(
gz_path,
media_type=content_type,
headers={"Content-Encoding": "gzip", "Vary": "Accept-Encoding"},
)
return None
Fix with Cubic



@router.get("/assets/{filename:path}")
async def serve_asset_file(
request: Request,
filename: str,
):
"""Serve a file from assets dir."""

base_path = Path(os.path.join(build_dir, "assets"))
file_path = (base_path / filename).resolve()

if not is_path_inside(file_path, base_path):
raise HTTPException(status_code=400, detail="Invalid filename")

if file_path.is_file():
accept_encoding = request.headers.get("accept-encoding", "")
precompressed = get_precompressed_response(file_path, accept_encoding)
if precompressed:
return precompressed
return FileResponse(file_path)
else:
raise HTTPException(status_code=404, detail="File not found")


@router.get("/copilot/{filename:path}")
async def serve_copilot_file(
request: Request,
filename: str,
):
"""Serve a file from assets dir."""

base_path = Path(copilot_build_dir)
file_path = (base_path / filename).resolve()

if not is_path_inside(file_path, base_path):
raise HTTPException(status_code=400, detail="Invalid filename")

if file_path.is_file():
accept_encoding = request.headers.get("accept-encoding", "")
precompressed = get_precompressed_response(file_path, accept_encoding)
if precompressed:
return precompressed
return FileResponse(file_path)
else:
raise HTTPException(status_code=404, detail="File not found")
Expand Down
1 change: 1 addition & 0 deletions frontend/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,7 @@
"tslib": "^2.6.2",
"typescript": "^5.2.2",
"vite": "^5.4.14",
"vite-plugin-compression": "^0.5.1",
"vite-plugin-svgr": "^4.2.0",
"vite-tsconfig-paths": "^4.2.0",
"vitest": "^0.34.4"
Expand Down
42 changes: 42 additions & 0 deletions frontend/pnpm-lock.yaml
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52 changes: 50 additions & 2 deletions frontend/vite.config.ts
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Original file line number Diff line number Diff line change
@@ -1,15 +1,63 @@
import react from '@vitejs/plugin-react-swc';
import path from 'path';
import { defineConfig } from 'vite';
import viteCompression from 'vite-plugin-compression';
import svgr from 'vite-plugin-svgr';
import tsconfigPaths from 'vite-tsconfig-paths';

// https://vitejs.dev/config/
export default defineConfig({
build: {
sourcemap: true
sourcemap: true,
rollupOptions: {
output: {
manualChunks: {
'vendor-react': ['react', 'react-dom', 'react-router-dom'],
'vendor-ui': [
'@radix-ui/react-dialog',
'@radix-ui/react-dropdown-menu',
'@radix-ui/react-popover',
'@radix-ui/react-select',
'@radix-ui/react-tabs',
'@radix-ui/react-tooltip',
'@radix-ui/react-accordion',
'@radix-ui/react-checkbox',
'@radix-ui/react-switch',
'@radix-ui/react-slider',
'@radix-ui/react-scroll-area',
'lucide-react'
],
'vendor-markdown': [
'react-markdown',
'rehype-katex',
'rehype-raw',
'remark-gfm',
'remark-math',
'remark-directive',
'highlight.js'
],
'vendor-utils': ['lodash', 'uuid', 'zod', 'i18next', 'react-i18next']
}
}
}
},
plugins: [react(), tsconfigPaths(), svgr()],
plugins: [
react(),
tsconfigPaths(),
svgr(),
viteCompression({
algorithm: 'gzip',
ext: '.gz',
threshold: 1024,
deleteOriginFile: false
}),
viteCompression({
algorithm: 'brotliCompress',
ext: '.br',
threshold: 1024,
deleteOriginFile: false
})
],
resolve: {
alias: {
'@': path.resolve(__dirname, './src'),
Expand Down
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