benchmark_large_house.mjs exercises the deterministic large-house-v1 fixture. The fixture has 60 rooms, 200 devices, 100 openings, 60 partitions, 40 columns and 500 decor objects on three floors.

The runner records seven measured samples after one discarded warm-up. With this intentionally small CI sample, the nearest-rank p95 is the observed maximum; reports keep the conventional field name but should be read as a high-tail guard rather than a population estimate:

model readiness and first stable render;
space switch, HA state update, pan/zoom and opening the settings dialog;
a shared-wall room-resize preview which is cancelled before persistence;
a twelve-switch navigation cycle;
Long Tasks for every measured window;
heap growth after four additional navigation rounds with forced GC;
hot-cache size and growth after the same warmed cycles.

Every report is tied to the source fingerprint embedded by Rollup. A stale bundle is a hard failure.

CI contract

The performance job checks out the candidate and its base SHA, builds both, and runs them sequentially with the same Node.js 22 process family, pinned Playwright Chromium and hosted runner. compare.mjs then applies two limits:

a relative regression allowance against the base-SHA report;
an absolute safety ceiling from budgets.json.

The tighter limit wins. The absolute values are catastrophic safety ceilings, not normal-performance targets; the base-relative comparison catches smaller regressions. Small fast operations receive an absolute noise allowance so normal scheduler jitter does not become a false regression. Heap, Long Tasks, warmed-cache growth and the expected rendered-device count are gated separately. Long-Task maximum/count/total checks use the same relative-plus-absolute policy as timings. Both raw reports and the comparison are always uploaded as the large-house-performance artifact, and the table is written to the GitHub job summary.

This base-vs-candidate design intentionally does not compare timings captured on different machines or different Chromium builds. A runtime/profile mismatch fails closed.

Before the base checkout, CI fetches the complete commit graph and verifies the requested comparison revision. A push github.event.before must both exist and remain an ancestor of the candidate; this catches the unreachable SHA left by a force-push. For that rewritten-push case, CI warns and prefers the candidate's direct parent as the closest honest comparison. An unusable PR base or another case without a safe parent falls back, with a warning, to the newest semver release tag reachable from the candidate and excludes a tag on the candidate itself. If no safe comparison exists, the job fails closed instead of comparing against an arbitrary commit.

Private card contract

The candidate benchmark runner is also executed against the base bundle, so every private houseplan-card field or method it reads is an explicit API of the performance harness. card-contract.mjs lists that surface for the large-house and Glow profiles. Each runner verifies it immediately after card creation and fails with the exact missing names or invalid runtime types before waiting for readiness or recording timings. Required caches must be real Map instances and must never be converted from missing/invalid values to plausible zeroes.

fields are required in every supported comparison base. optionalFields are newer members whose absence has an explicit safe fallback in the runner; if an optional member exists, its declared fieldTypes contract still applies. Add a new safely degradable field to optionalFields until every supported base has it, then promote it to fields. A member without a truthful fallback must be introduced through a compatibility revision before the benchmark consumes it.

Rename a consumed private member in two revisions:

teach the contract and every reader to understand both the old and proposed name while production still exposes the old name; land that compatibility revision so it can become a comparison base;
rename the production member and prefer the new name while retaining the old reader fallback. Remove the fallback only after all supported comparison bases expose the new member.

This sequencing keeps the current harness capable of profiling both source trees. A one-step rename that merely edits the candidate reader is forbidden: it would make the same runner incompatible with its base bundle.

Local diagnostics

Build and copy a fresh demo bundle first, then run:

npm run benchmark:large-house -- --samples=7 --warmups=1 --output=artifacts/performance/local.json

A local report is diagnostic only; it cannot replace the CI comparison.

To reproduce the comparison against another checkout using one harness and one browser installation:

npm run benchmark:large-house -- --target-root=../base --samples=7 --output=artifacts/performance/baseline.json
npm run benchmark:large-house -- --target-root=. --samples=7 --output=artifacts/performance/candidate.json
npm run benchmark:compare

Changing budgets

Budget changes require an explicit review of recent CI artifacts and a written rationale in the change. Do not loosen a threshold merely to make a single red run pass. A new fixture profile gets a new profile id instead of silently changing the meaning of large-house-v1.

The cleanFloor entry ceiling is 160: the reviewed fixture currently warms 120 deterministic room/physical-body entries, and the extra 40 slots allow a legitimate fixture extension without weakening the separate zero-growth gate.

Glow profiles

Both Glow profiles run deterministic 1/10/30/60-pool variants at DPR 1 and Chromium CPU throttling x4, but deliberately exercise different fixtures:

large-light-blend-v1 compares the isolated screen group with the previous normal-layer implementation on the shared frontend/backend schema fixture test/fixtures/glow/additive-pools.json;
large-house-glow-overlay-v1 measures simultaneous temperature fill and independent Glow on the existing 60-room/200-device large-house fixture, without changing large-house-v1.

npm run benchmark:glow -- --profile=large-light-blend-v1 --output=artifacts/performance/glow.json
npm run benchmark:glow -- --profile=large-house-glow-overlay-v1 --output=artifacts/performance/overlay.json

Reports include per-variant state-update timings, render/pool counts, Long Tasks, screenshot time, heap and cache growth. The first CI comparison against a base SHA that predates glow_enabled bootstraps only the overlay profile's relative baseline from the candidate; its absolute ceilings still gate that introduction. Every subsequent revision compares both profiles to the real base SHA.

The initial absolute ceilings are intentionally conservative bootstrap limits; they must be reviewed against the first paired Ubuntu artifacts before the feature is promoted from beta. Same-runner relative checks remain the primary candidate-only regression signal.