Merging this PR will not alter performance

✅ 24 untouched benchmarks

_{Comparing FarhanAliRaza:lighthouse-compression (64b84a5) with main (5d65aa9)}

Greptile Summary

This PR adds build-time pre-compression of frontend static assets (gzip, brotli, zstd) via a new Node.js script (compress-static.js) and a PrecompressedStaticFiles Starlette handler that serves the best sidecar based on Accept-Encoding content negotiation. The test harness (AppHarnessProd) is also upgraded from the stdlib http.server to a real Uvicorn/Starlette server, so integration tests exercise the same stack as production.

• A new frontend_compression_formats config option (default ["gzip"]) controls which sidecar formats are generated; it is comma-parseable from the environment and validated against a hard set of supported names.
• PrecompressedStaticFiles extends Starlette's StaticFiles with Accept-Encoding-aware sidecar selection, emits Vary: Accept-Encoding unconditionally when encodings are configured, and re-routes the HTML 404-fallback path through file_response so compressed 404 pages are served correctly.
• The test harness switch to Uvicorn means precompressed serving is exercised end-to-end in integration tests, which is a meaningful fidelity improvement over the old stdlib server.

Confidence Score: 4/5

Core compression and serving logic is correct; the main risk area is the test harness rewrite, not the feature itself.

The PrecompressedStaticFiles handler and compression pipeline are well-structured and thoroughly tested. The AppHarnessProd rewrite reads uvicorn's internal .servers[0].sockets to discover the bound port and mutates the process-global config.deploy_url — neither breaks the feature itself, but both add fragility to the test harness that could surface as confusing failures on a uvicorn upgrade or in long pytest sessions.

reflex/testing.py — the uvicorn internals access and global config mutation deserve a second look before this pattern is copied elsewhere in the test suite.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant Dev as Developer
    participant Build as build.py
    participant JS as compress-static.js
    participant Server as PrecompressedStaticFiles
    participant Browser as Browser

    Dev->>Build: reflex export
    Build->>JS: node compress-static.js static_dir gzip brotli zstd
    JS->>JS: Walk files matching COMPRESSIBLE_EXTENSIONS
    JS->>JS: Write .gz .br .zst sidecars for each file

    Browser->>Server: GET /assets/app.js with Accept-Encoding br,gzip
    Server->>Server: _parse_accept_encoding header
    Server->>Server: _select_sidecar picks best quality on disk
    Server-->>Browser: 200 Content-Encoding br Vary Accept-Encoding

    Browser->>Server: GET /missing-route
    Server->>Server: super get_response returns FileResponse 404.html
    Server->>Server: Intercept and re-route through file_response
    Server-->>Browser: 404 Content-Encoding br compressed 404.html

_{Reviews (1): Last reviewed commit: "feat: pre-compress frontend assets at bu..." | Re-trigger Greptile}

Nice!