The r1 diagnosis was wrong, and the measurement in the code review proved
it: removing the two declarations from `static properties` left the cold
start at 19 update cycles, 4 model builds and 4 config epochs, exactly the
numbers of the bug. Lit's forced first-update change does mark `_serverCfg`
changed, but at that moment the body and `_cfgEpochPreservedConfig` are both
null, `preserveGeometry` is true and the epoch does not move. The comment
above `static properties` now says that; the declaration still stays out,
because two owners of one reactivity is what #500 removed.
The real cause is the `await`. Before #500 everything from
`_adoptStructuralResponses` to the end of the load ran in one task: the
adopted bodies, `_adoptInitialSpace`, the viewport restore, `_loadOk`, and
the device seeding — whose `_syncNewDevices`/`_seedHiddenDevices` write the
config back — all landed in a single Lit update. #500 made the adoption an
async sequence, so the caller resumes one microtask later, after Lit has
already painted the adopted config; the seeding writes then arrive as a
second config epoch, a second model build and a second paint of a 60-room
house.
`GatedAdoptionInput` gains `afterAdopt`, the mirror of `beforeAdopt`: it
runs synchronously at the end of the sequence, before the promise resolves.
`_loadFromServer` moves the viewport restore, `_loadOk` and the device
rebuild into it — `_syncNewDevices` refuses to write before `_loadOk`, so
the order inside the hook matters — and the load tail now rebuilds devices
only when nothing was adopted. `_reloadConfigOnly` takes the same route.
Measured with the project's own runner, 7 samples per profile, base
`a44fbd37` against this tree (Chromium 152, sandbox):
interaction modelReadyMs 761.3 ≤ 950.56 (base 731.2)
firstStableRenderMs 2567.2 ≤ 3000 (base 2542.7)
longTask.maxSingleMs 690 ≤ 921 · cache.entries.cleanFloor 100
isometric modelReadyMs 1252.9 ≤ 1499.76 (base 1249.8)
firstStableRenderMs 1378 ≤ 1610.16 (base 1341.8)
Boot diagnostics on both trees: 18 update cycles, 3 model builds, 3 config
epochs, with the same epoch trace — the candidate is no longer
distinguishable from the base.
Witnesses. `config-adoption.test.mjs` queues a microtask at the start of
the adoption and pins that `afterAdopt` runs before it — the probe fails the
moment the hook crosses an await; `config-adoption-ownership.test.mjs` pins
the wiring in the card and the hook's place in the sequence. Mutants
`adoption-tail-defers-caller-hook` (defers the hook by one microtask) and
`authoritative-load-seeds-devices-after-the-await` (drops the rebuild from
the hook) redden them.
The initial View graph grows 40 B gzip, so the #438 ceiling is recentred
300 300 → 300 400 with the usual dated note; measured 299 812 B keeps 588 B
above and 1 412 B below the band. The overall 301 066 B budget and the #367
headroom debt are untouched.
Issue: #520
User-Visible: no
#500 gave `_serverCfg` and `_layout` prototype accessors but left them in
`static properties`. Lit marks such a property `wrapped` and, on the FIRST
update, force-writes it into `changedProperties` with an `undefined` old
value even though nobody assigned anything (`reactive-element.js:249-252`
and `:880-886`). `willUpdate` reads that as a config replacement, raises
`_cfgEpoch`, the memoized model key changes, and a 60-room house builds and
paints its model a second time: measured 19 update cycles, 4 builds and 4
epochs against 18 / 3 / 3 before #500, worth ~550 ms of `modelReadyMs` and
the same on `firstStableRenderMs` (3355 against a 3000 ceiling).
The declaration goes; the bodies stay reactive through the owner —
`_adoption` → `onBodyReplaced` → `requestUpdate(field, previous)` — which
needs no declaration: `getPropertyOptions` falls back to the default and
`changed.has('_serverCfg')` works as before. `noAccessor: true` would not
help, `wrapped` is set before that flag is read. The trap is written above
`static properties`, where someone would put the declaration back.
`cache.entries.cleanFloor` returns to 100 in both interaction budgets: the
120 entries were the extra epoch re-keying the per-room cache, not a
property of the design — the reasoning in 914e8402 was wrong.
Witness: test/config-adoption-ownership.test.mjs pins that neither body is
declared; the mutant `adoption-bodies-declared-reactive` puts the
declaration back and reddens it.
The boot diagnostics of the previous three commits touch four private
members, so they are declared in the performance contract: `_buildModel` and
`_cfgEpoch` outright (both exist in every supported comparison base), and the
adoption entry point as a current/legacy pair — #500 turned the private
`_adoptStructuralResponses` into the public `_adoptAuthoritative`, and an
undeclared rename would have the counter report zero adoptions instead of
failing.
The same commits carried a `node_modules` symlink: `.gitignore` had the
pattern with a trailing slash, which does not cover a symbolic link, and
`git add -A` in a sandbox worktree committed it. The link is removed and the
pattern loses the slash; a mutant run on this branch failed with `EEXIST` on
it.
Issue: #520
User-Visible: no
`test/config-adoption-ownership.test.mjs` pins identity writes to the owner
and ratchets body staging (AC1/AC2). `demo/smoke_post_write_adoption.mjs`
drives space/delete (both runtimes), Optimize Undo and Import apply with a
concurrent backdrop change between the write and the re-read (AC4). Smokes
that seed revisions from outside the card keep working through the
`seedIdentity` harness seam behind the card's delegate setters. The initial
View ceiling is re-centred with the measured fact; ARCHITECTURE.md gets the
boundary paragraph.
Issue: #500
User-Visible: no
Sergey Matyunin