Benchmarks

Streaming performance benchmarks

Use reproducible harnesses, then validate in-browser behavior with live delta-by-delta comparisons against alternative renderers.

Fixture: naive-bayes.mdScenario: S2_typical (50ms)Mode: incrementalRenderer: V2Methodology documentation

Live renderer comparison lab (sequential)

Renderers run one-by-one to minimize CPU contention. Each engine gets an unscored warmup pass before the scored pass. Metrics split into first-visible commit vs final-stable commit.

State: idle

Active engine: -

Phase: warmup

Run: 0 / 1

Measured passes: 3

Total passes incl. warmup: 6

Delta: 0 / 195

Chars: 0 / 8,165

Throughput: 0 chars/s

1. StreamMDX2. Streamdown3. react-markdown

Current order: -

Methodology mode

Freeform tuning enabled for diagnosis.

Active profile snapshot: chunk=42, interval=32ms, repeats=16, runs=1, order=fixed, workload=parity-gfm. Differs from CI profile.

A scored run is one full cycle across all renderers (then repeated for the configured run count).

Chunk size (chars)42

Emit interval (ms)32

Fixture repeats16

Scored run cycles1

Order mode

Benchmark profile

Chart metric

Split mode shows both metrics.

Chart layout

Per-delta latency (first visible commit - emit time)

Y max: 10 ms

Per-delta latency (final stable commit - emit time)

Y max: 10 ms

StreamMDXStreamdownreact-markdown

Renderer	First paint p50	First paint p95	Final stable p50	Final stable p95	Run p50	Throughput p50
StreamMDX	-	-	-	-	-	-
Streamdown	-	-	-	-	-	-
react-markdown	-	-	-	-	-	-

Metric leaders

First paint p50: -Final stable p50: -Run p50: -Throughput p50: -

StreamMDX: 0 / 4 metric winsStreamdown: 0 / 4 metric winsreact-markdown: 0 / 4 metric wins

CI gate (StreamMDX vs Streamdown)

PENDING • pass=0 fail=0 pending=4Run in CI locked mode before claiming results

First paint p50 <= StreamdownFinal stable p50 <= StreamdownRun p50 <= StreamdownThroughput p50 >= Streamdown

Renderer	Emit→ingest p50	Ingest→commit p50	Emit→commit p50	Append overhead p50	Timer drift p50 / p95
StreamMDX	-	-	-	-	- / -
Streamdown	-	-	-	-	- / -
react-markdown	-	-	-	-	- / -

StreamMDX

Incremental worker parser + patch renderer

No stream data yet.

Streamdown

Drop-in streaming replacement for react-markdown

No stream data yet.

react-markdown

Baseline markdown renderer (full re-render on updates)

No stream data yet.

Method note: each engine runs warmup then scored pass in isolation. Commit timing capture is unified across engines via layout-effect commit hooks to avoid instrumentation bias. Use CI locked mode for claim-grade runs; use explore mode to diagnose bottlenecks. \"First paint\" measures earliest visible commit; \"final stable\" reflects how quickly each delta settles after downstream formatting/render passes.

Static render comparison (content types)

Measures one-shot static rendering across prose, tables, code, and mixed markdown fixtures. Times are captured per engine as first mutation and final settled mutation.

State: idle

Iterations: 3

Progress: 0 / 0

Active fixture: -

Active engine: -

Timeouts: 0

Iterations per fixture3

Prose heavyTable heavyCode heavyMixed rich markdown

Content type	Description	StreamMDX first/final p50	Streamdown first/final p50	react-markdown first/final p50	Final p50 winner
Prose heavy	Long narrative text with headings, lists, and inline formatting.	- / -n=0	- / -n=0	- / -n=0	-
Table heavy	Large table blocks with short explanatory text.	- / -n=0	- / -n=0	- / -n=0	-
Code heavy	Multiple fenced code blocks with surrounding markdown.	- / -n=0	- / -n=0	- / -n=0	-
Mixed rich markdown	Lists, quotes, links, tasks, and tables in one document.	- / -n=0	- / -n=0	- / -n=0	-

StreamMDX

Streamdown

react-markdown

Reproduce

Run the harness locally with the same fixture and scenario.

NEXT_PUBLIC_STREAMING_DEMO_API=true npm run docs:dev

npm run perf:harness -- --fixture naive-bayes --scenario S2_typical --runs 3 --warmup 1 --out tmp/perf-baselines

npm run perf:compare -- --base tmp/perf-baselines/<base> --candidate tmp/perf-baselines/<candidate>

Renderer model comparison

Renderer	Update model	Best fit
StreamMDX	Incremental patch apply	Streaming UIs + deterministic replay
Streamdown	React re-render on content updates	Drop-in migration from react-markdown
react-markdown	React re-render on content updates	Simple static markdown content

Perf quality changelog