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fixtures/flight-ssr-bench/README.md

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+# Flight SSR Benchmark
+
+Measures the performance overhead of the React Server Components (RSC) Flight pipeline compared to plain Fizz server-side rendering, across both Node and Edge (web streams) APIs.
+
+## Prerequisites
+
+Build React from the repo root first:
+
+```sh
+yarn build-for-flight-prod
+```
+
+Then install the fixture's dependencies:
+
+```sh
+cd fixtures/flight-ssr-bench
+yarn install
+```
+
+## Scripts
+
+| Script | Purpose |
+| --- | --- |
+| `yarn bench` | Sequential benchmark with Flight script injection (realistic framework pipeline). Best for measuring Edge vs Node overhead. |
+| `yarn bench:bare` | Sequential benchmark without script injection. Best for measuring React-internal changes (e.g. Flight serialization optimizations) with less noise from stream plumbing. |
+| `yarn bench:server` | HTTP server benchmark using autocannon at c=1 and c=10. Best for measuring real-world req/s. The c=1 results are also useful for tracking React-internal changes. |
+| `yarn bench:concurrent` | In-process concurrent benchmark (50 in-flight renders). Measures throughput under load without HTTP overhead. |
+| `yarn bench:profile` | CPU profiling via V8 inspector. Saves `.cpuprofile` files to `build/profiles/`. |
+| `yarn start` | Starts the HTTP server for manual browser testing at `http://localhost:3001`. Append `.rsc` to any Flight URL to see the raw Flight payload. |
+
+## What it measures
+
+Each script benchmarks 8 render variants:
+
+- **Fizz (Node, sync/async)** -- plain `renderToPipeableStream`, no RSC
+- **Fizz (Edge, sync/async)** -- plain `renderToReadableStream`, no RSC
+- **Flight + Fizz (Node, sync/async)** -- full RSC pipeline: Flight server (`renderToPipeableStream`) -> Flight client (`createFromNodeStream`) -> Fizz (`renderToPipeableStream`)
+- **Flight + Fizz (Edge, sync/async)** -- full RSC pipeline: Flight server (`renderToReadableStream`) -> Flight client (`createFromReadableStream`) -> Fizz (`renderToReadableStream`)
+
+The "sync" variants use a fully synchronous app (no Suspense boundaries). The "async" variants use per-row async components with staggered delays and individual Suspense boundaries (~250 boundaries per render).
+
+### Script injection
+
+The `yarn bench` and `yarn bench:server` scripts simulate what real frameworks do: tee the Flight stream and inject `<script>` hydration tags into the HTML output. This uses a `setTimeout(0)`-buffered Transform/TransformStream to avoid splitting mid-HTML-tag. `yarn bench:bare` skips this for cleaner React-internal measurement.
+
+## Test app
+
+A dashboard with ~25 components (16 client components), rendering:
+
+- 200 product rows with nested reviews, specifications, and supplier data (~325KB Flight payload)
+- 50 activity feed items
+- Stats grid with 24-month chart data
+- Sidebar with navigation and recent activity
+
+## Output
+
+The overhead tables show two comparisons:
+
+1. **Flight overhead** -- Flight+Fizz vs Fizz-only (how much RSC adds)
+2. **Edge vs Node** -- web streams vs Node streams (stream implementation cost)
+
+Delta is shown as percentage change plus a factor (e.g. `+120% 2.20x` means 2.2x slower).