diff --git a/demo/benchmark_large_house.mjs b/demo/benchmark_large_house.mjs
index 1570e50d..62f32c57 100644
--- a/demo/benchmark_large_house.mjs
+++ b/demo/benchmark_large_house.mjs
@@ -1121,6 +1121,24 @@ try {
       card._settingsDialog = null;
       await card.updateComplete;
 
+      // #735: every sample mounts a new card, and until here it has visited
+      // only floors 1 and 2. The cycle would otherwise pay a first visit to
+      // floor 3 (and, after the interaction editor series moves the config
+      // epoch, to floor 1 again) inside its window, so one cold floor build
+      // dominated a metric documented as warmed navigation. Visit every
+      // fixture floor once in cycle order outside every timed and Long Task
+      // window, then return to floor 2 so the cycle still starts with 2 -> 1.
+      for (let floor = 1; floor <= fixture.counts.floors; floor++) {
+        card._pickSpace(`perf-floor-${floor}`);
+        await card.updateComplete;
+        await frame();
+      }
+      card._pickSpace('perf-floor-2');
+      await card.updateComplete;
+      await frame();
+
+      const switchCycleCachesBefore = cacheSnapshot(card);
+      const switchCycleBuildsBefore = isoStructuralBuildCount(card);
       const switchCycle = await duration(async () => {
         for (let index = 0; index < 12; index++) {
           card._pickSpace(`perf-floor-${(index % fixture.counts.floors) + 1}`);
@@ -1131,6 +1149,19 @@ try {
           await new Promise((done) => setTimeout(done, 0));
         }
       });
+      // #735 guard: a warmed cycle builds nothing. Any grown hot cache or a
+      // structural 2.5D build inside the window means a cold floor visit
+      // leaked back into switchCycleMs. Caches an older base lacks read as 0
+      // and cannot grow; its build counter is null and is not judged.
+      const switchCycleCachesAfter = cacheSnapshot(card);
+      const switchCycleBuildsAfter = isoStructuralBuildCount(card);
+      const switchCycleBuilt = Object.keys(switchCycleCachesAfter)
+        .filter((key) => switchCycleCachesAfter[key] > switchCycleCachesBefore[key])
+        .map((key) => `${key} +${switchCycleCachesAfter[key] - switchCycleCachesBefore[key]}`);
+      if (switchCycleBuildsBefore != null && switchCycleBuildsAfter !== switchCycleBuildsBefore)
+        switchCycleBuilt.push(`isoStructuralBuilds +${switchCycleBuildsAfter - switchCycleBuildsBefore}`);
+      if (switchCycleBuilt.length)
+        throw new Error(`${profile} switchCycle built a floor inside the window: ${switchCycleBuilt.join(', ')}`);
 
       await forceGc();
       const cacheBefore = cacheSnapshot(card);
diff --git a/demo/performance/README.md b/demo/performance/README.md
index abc4b133..353f5ab3 100644
--- a/demo/performance/README.md
+++ b/demo/performance/README.md
@@ -66,11 +66,29 @@ 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;
+- a twelve-switch navigation cycle; since #735 every fixture floor is visited
+  once before its window, and a floor build inside the window (any grown hot
+  cache or a 2.5D structural build) fails the sample;
 - 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.
 
+Issue #735 moved the first visit to each floor out of the navigation cycle.
+Every sample mounts a new card that had seen only floors 1 and 2, so the cycle
+used to pay one cold floor-3 build inside its window (in
+`large-house-interaction-v1` also a floor-1 rebuild, because the editor series
+moves the config epoch that keys the clean-floor cache). That single step was
+about half of `switchCycleMs` and hid the warmed switches the metric is
+meant to describe; a cold floor visit stays measured by `spaceSwitchMs`. The
+change is a level step, not a regression or a speed-up of the card: base and
+candidate are still measured by the candidate runner in the same run, so the
+comparison is unaffected, but absolute `switchCycleMs` history and the
+profile's Long Task sums before and after #735 are not comparable. Local
+diagnostics showed the median falling by roughly 1.6–2.8 times (for example
+`large-house-v1` about 2.0 s to 0.9 s); the exact-SHA Full Performance medians
+on both sides of the change are recorded in #735. Budgets and `hardMaxMs` did
+not change.
+
 Every report is tied to the source fingerprint embedded by Rollup. A stale
 bundle is a hard failure.
 
diff --git a/test/performance-workflow.test.mjs b/test/performance-workflow.test.mjs
index 638958fa..38ca5f27 100644
--- a/test/performance-workflow.test.mjs
+++ b/test/performance-workflow.test.mjs
@@ -175,6 +175,36 @@ test('#570 current Stage 4 runner fails closed on the agreed observable DOM cont
     'both isometric profiles must reject a structural rebuild on the HA-only window');
 });
 
+test('#735 switchCycle times warmed navigation and fails on a floor build inside its window', () => {
+  // Every sample mounts a new card that has seen only floors 1 and 2 before
+  // the cycle, so the first visit to floor 3 (and, in the interaction
+  // profile, a rebuilt floor 1) used to dominate switchCycleMs. The runner
+  // visits every fixture floor once after the settings dialog closes and
+  // before the timed window, then guards the window against any build.
+  const runner = readFileSync(new URL('../demo/benchmark_large_house.mjs', import.meta.url), 'utf8');
+  const settingsClosed = runner.indexOf('card._settingsDialog = null;');
+  const cycleStart = runner.indexOf('const switchCycle = await duration(');
+  assert.ok(settingsClosed > 0 && cycleStart > settingsClosed,
+    'the switch cycle must follow the closed settings dialog');
+  const warmup = runner.slice(settingsClosed, cycleStart);
+  assert.match(warmup,
+    /for \(let floor = 1; floor <= fixture\.counts\.floors; floor\+\+\) \{\s*card\._pickSpace\(`perf-floor-\$\{floor\}`\);\s*await card\.updateComplete;\s*await frame\(\);\s*\}/,
+    'every fixture floor must be visited once before the switchCycle window');
+  assert.match(warmup,
+    /card\._pickSpace\('perf-floor-2'\);\s*await card\.updateComplete;\s*await frame\(\);\s*const switchCycleCachesBefore = cacheSnapshot\(card\);\s*const switchCycleBuildsBefore = isoStructuralBuildCount\(card\);\s*$/,
+    'the cycle must still start from floor 2 with the guard snapshot taken last');
+  assert.ok(!warmup.includes('duration(') && !warmup.includes('startLongTaskWindow('),
+    'the warm-up must stay outside every timed and Long Task window');
+  const afterCycle = runner.slice(cycleStart, runner.indexOf('await forceGc();', cycleStart));
+  for (const contract of [
+    'const switchCycleCachesAfter = cacheSnapshot(card);',
+    'const switchCycleBuildsAfter = isoStructuralBuildCount(card);',
+    'switchCycleCachesAfter[key] > switchCycleCachesBefore[key]',
+    'switchCycleBuildsBefore != null && switchCycleBuildsAfter !== switchCycleBuildsBefore',
+    '${profile} switchCycle built a floor inside the window: ',
+  ]) assert.ok(afterCycle.includes(contract), `missing #735 switchCycle guard: ${contract}`);
+});
+
 test('#347: a rewritten before forces the full run instead of guessing the range', () => {
   // Force-push kills github.event.before; the merge-base fallback then
   // guessed a range that hid a real custom_components/** diff behind two doc