perf: wire node-stream-helpers into render pipeline behind useNodeStreams flag#91583
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benfavre wants to merge 3 commits intovercel:canaryfrom
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perf: wire node-stream-helpers into render pipeline behind useNodeStreams flag#91583benfavre wants to merge 3 commits intovercel:canaryfrom
benfavre wants to merge 3 commits intovercel:canaryfrom
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…eams flag Add `experimental.useNodeStreams` config flag that switches the stream operations module (stream-ops.ts) to load native Node.js implementations for hot-path functions: - chainStreams: uses chainNodeStreams (PassThrough-based sequential piping) - streamToBuffer: uses nodeStreamToBuffer (for-await on Node Readable) - streamToString: uses nodeStreamToString (streaming TextDecoder) - renderToFizzStream: uses renderToPipeableStream instead of renderToReadableStream, avoiding web→node conversion overhead in React Complex transform chains (continueFizzStream, prerender continuations) still delegate to the web implementation as a stopgap — the native buffering and data inlining transforms from node-stream-helpers will be wired in a follow-up once the web transform chain is decomposed. Includes the node-stream-helpers module from PR vercel#91580 which provides the underlying native stream utilities. References: vercel#91580, vercel#89566, vercel#90500 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Replace the web stream delegation in stream-ops.node.ts with a native Node.js Transform pipeline for continueFizzStream. This eliminates the 6-8 web TransformStream objects (plus their internal ReadableStream/ WritableStream pairs) that were created per request — the single most CPU-intensive function in the SSR hot path. New native Node.js Transform equivalents added to node-stream-helpers.ts: - createDeferredSuffixTransformNode (suffix injection after first chunk) - createHeadInsertionTransformNode (server HTML in <head>) - createMoveSuffixTransformNode (move </body></html> to end) - createHtmlDataDplIdTransformNode (data-dpl-id on <html>) - createMetadataTransformNode (icon mark removal + metadata insertion) - createRootLayoutValidatorTransformNode (html/body tag validation) All transforms use: - bindSnapshot() for ALS context propagation - Pre-computed Buffer constants for fast C++ Buffer.indexOf() - Lazy getNodeStream() require for Edge/DCE safety Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This was referenced Mar 18, 2026
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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
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Summary
Adds
experimental.useNodeStreamsconfig flag that wires our native Node.js stream helpers into the render pipeline:stream-ops.tsbecomes a runtime switcher: when__NEXT_USE_NODE_STREAMSis set, it loadsstream-ops.node.tsinstead ofstream-ops.web.tschainStreams,streamToBuffer,streamToString, andrenderToFizzStream(viarenderToPipeableStream)continueFizzStream, prerender continuations) still delegate to the web implementation as a stopgap — the native buffering and data inlining transforms will be wired in a follow-upnode-stream-helpers.tsmodule from PR feat: add Node.js native stream helpers for render pipeline #91580 which provides the underlying native stream utilitiesMotivation
Profiling shows that WhatWG stream polyfills and the web-to-node conversion layer account for 35%+ of CPU time in SSR workloads (see #89566). By using Node.js native streams on the server, we can eliminate this overhead. This PR establishes the switching infrastructure and implements the easy wins; the complex transform chain migration is a follow-up.
How to enable
What's native vs delegated
chainStreamschainNodeStreamsvia PassThroughstreamToBufferfor awaiton Node ReadablestreamToStringrenderToFizzStreamrenderToPipeableStreamnodeReadableToWebReadable.toWeb()continueFizzStreamcontinueStaticPrerendercontinueDynamic*renderToFlightStreamresumeAndAbortresume()produces web streamsReferences
Test plan
experimental.useNodeStreams: trueand run the app-render test suiterenderToFizzStreamproduces correct HTML viarenderToPipeableStreamchainStreamscorrectly concatenates multiple streamsstreamToBuffer/streamToStringproduce correct output🤖 Generated with Claude Code