5.0.0-beta.2 · Published beta · 13f4954c. Published on npm. Match your installed version.

Performance measurements#

Marionette v5 is still changing. Bundle sizes and hosted timings inform review; they do not impose a release budget during alpha development. Adding an optional adapter or reorganizing an export does not require a performance approval record.

What we measure#

npm run size builds the packages and reports Brotli-compressed artifacts, production module graphs, representative consumer bundles, and deterministic public instance-construction and retention observations. Core, data, and adapter packages are measured separately. ESM, CommonJS, and UMD are alternative distributions, not bytes every application downloads together.

The current consumer-bundle authority is fixture v2. It retains the v1 full-root and optional-adapter entries unchanged and adds named-import applications for View plus Region, native CollectionView data, and Application plus state. Changing fixture versions makes the resulting report non-comparable with older bundle evidence; the old fixture remains available for replay rather than being silently rewritten.

CI compares the exact PR base with the candidate. Each checkout uses its own measurement script, configuration, package exports, and built files. The report labels new and removed paths explicitly; a renamed adapter appears as one removed path and one new path. It does not claim those paths are comparable. The report and underlying JSON measurements are attached to the CI run. When consumer fixtures or their tooling change, their sizes are labeled non-comparable rather than presented as a regression.

The historical Phase 0 values remain available as context. They are not ceilings. Past budget-amendment evidence is retained under evidence/ for provenance, but its approval process is retired.

Resource schema 2 counts consumer-observed View, Region, Behavior, and CollectionView initializations, plus external subscriptions, DOM listeners, callbacks, DOM connectivity, and public ownership after teardown. It does not inspect private instance fields, internal indexes, or allocation shapes. These metrics are not directly comparable with earlier private-representation counts; the report identifies that schema change.

What still fails#

Reporting-only size does not mean accepting broken packages. Checks still reject:

• Missing built artifacts or exported entry points omitted from the measurement inventory.
• Production graphs that cannot be measured or include forbidden development files or dependencies.
• Consumer fixtures that unexpectedly import optional adapters or their peers.
• Invalid measurement fixtures or a mismatched measurement toolchain.

Normal runtime, browser, type, and package tests remain required. Resource changes are review observations; an extra property or allocation is not automatically a bug. Lifecycle tests establish the supported cleanup behavior.

Adding an adapter#

Add its public exports, build outputs, and measurement entries alongside its implementation and tests. config/performance.json lists the runtime artifacts and production graphs; scripts/performance/adapters-package-size.mjs checks the adapter's external dependencies and measures its published formats. No frozen baseline, relocation ledger, special approval comment, or ceiling increase is needed.

Optional adapters must stay out of consumers that do not import them. The consumer-bundle fixtures in benchmarks/consumer-bundles/ exercise selected public imports and report each application's resulting bundle. Extend those fixtures when a new consumer scenario is useful; installing the adapters package is not itself evidence that all adapters ship to the browser.

Timing and reproducibility#

npm run performance:timing records hosted timing samples. CI reports median and p95 changes and identifies changed workloads as non-comparable. Hosted timings are noisy: investigate meaningful changes with matched builds and repeated, alternating runs before attributing them to a code change. Do not replace a full benchmark result with an unlabeled targeted retry.

That command remains the active CI-comparable jsdom and Backbone adapter-backed series retained for matched historical comparisons. Its workload IDs, environment, and results should be interpreted on those terms. It does not measure browser layout or paint, native @mnjs/data, or Application/state composition.

The separate browser runner exercises representative v5 public APIs in a real browser:

node scripts/performance/browser.mjs --profile validation
node scripts/performance/browser.mjs --profile baseline \
  --runner-note "exclusive quiet host; no other builds or tests"

The validation profile runs one warmup and two retained samples. It is a bounded functional check and is always labeled ineligible as a baseline. The baseline profile runs five warmups and 25 retained samples in headless Chromium. Its defaults may be inspected or varied with --browser chromium|firefox|webkit, --headed, --samples <count>, --warmups <count>, --output <path>, and --runner-note <text>. Any baseline profile override is labeled ineligible for the canonical baseline comparison. A matching command still requires the operator to confirm an exclusive quiet-host window; the runner records that note but cannot prove host isolation.

CI and npm run verify -- --full run the validation profile through npm run test:browser-performance. Its public-behavior assertions are required; timings remain report-only and do not fail a build for being slow.

The initial local desktop samples are retained in benchmarks/browser-performance/results/2026-09-09/, including raw outcomes, reproduction hashes and the recorded background-activity limitation. They are a starting point for matched local measurements, not a cross-host performance claim.

The browser fixture covers three bounded workloads in a fixed order:

• Native-data list update, same-position replacement, and reorder with 250 rows. It also asserts that an unrelated survivor keeps its View, DOM node, focus, selection, and unsaved input value. A layout read and animation-frame boundary include browser rendering work in the sample.
• Application startup superseded by restart, followed by successful destruction, over 25 cycles. It asserts cancellation, absence of stale start events, and consumer-owned lifecycle resource release.
• Forty alternating borrowed/owned state mounts and destructions. A consumer-owned external source records subscription removal, owned disposal ordering, late callbacks, delegated DOM callbacks, and remaining managed DOM.

The JSON report retains every warmup duration, every raw sample and its observable outcomes, median/p95/min/max summaries, workload configuration and order, source commit and dirty state, fixture and built-artifact SHA-256 values, browser version and mode, Node/npm/Playwright versions, host details, lifecycle monitoring, and whether accessibility instrumentation was enabled. Source and artifact fingerprints are captured before launch and verified again after all samples; input drift fails the run instead of producing a mislabeled report. Each workload has a ten-second deadline so a stalled browser operation still reaches browser/server cleanup. The default report path is test/tmp/performance/browser-report.json.

These successful teardown observations establish the documented public cleanup outcomes for the measured operations. They do not establish garbage collection or heap reachability. No counter, listener set, lifecycle event, or DOM observation is reported as GC evidence. The separate retention probe below supplies direct reachability observations; timing still has no pass/fail budget.

The release profile pins the build toolchain. Reports retain the measured artifact inventory and timing workload metadata so comparisons can be assessed. A measurement failure remains a failure; it must not appear as a zero-size artifact or a passing benchmark.

Revisit budgets after v5 stabilizes#

Once the API and package boundaries settle, choose representative consumer bundles and record a stable baseline. Any future budget should protect a useful user outcome, account for optional dependencies, and distinguish intentional features from unexplained regressions. Do not automatically reactivate the old Phase 0 ceiling or per-PR approval threshold at release time.

Direct browser retention evidence#

npm run performance:retention builds the local packages and runs the bounded Chromium probe in benchmarks/browser-performance/retention/workloads.js. It performs two warmup batches and six recorded batches, each with 50 cycles of native CollectionView mutation/render/destruction, replacement Region detach/adopt, Application cancellation/restart/child teardown, and shared/owned state disposal. --cycles (1–100), --batches (1–10) and --output can narrow a reproduction; retain those choices with its result. The default run has a 120-second deadline.

Only consumer-held public objects and roots are tracked with WeakRef. A positive control must remain reachable while strongly held and disappear after release. CDP forces collection in separate browser jobs. External data sources and borrowed Regions remain strongly reachable while destroyed owners are checked; they are then destroyed/released and checked too. This prevents an unreachable source/owner cycle from hiding a leaked subscription. Any retained tracked owner, root or released input fails this finite probe. No framework private member is inspected.

The report retains source/artifact hashes, dirty state, browser and host identity, counts for each batch, CDP heap usage and DOM counters. Heap sizes are contextual observations, not portable thresholds. This demonstrates collection for the tested successful workflows, not universal absence of leaks or support for synchronous recovery. The runner is maintainer tooling and never enters production imports.

The manual Browser performance evidence workflow fixes the runner to ubuntu-24.04, builds once, then runs three sequential baseline blocks with no concurrent build or test steps. It runs retention after timing and retains all three raw reports plus the retention report for 90 days, including partial output on failure. Compare the blocks' medians and p95 values to characterize variance; do not select the fastest block. The source/artifact hashes must match across blocks. A fresh hosted job controls our workload scheduling, not the underlying shared hardware, so persistent variance needs a dedicated runner before setting performance budgets. This workflow does not run paid agent benchmarks or publish.