diff --git a/package.json b/package.json
index 6826f04..42e73b1 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
   "scripts": {
     "build": "tsc -p tsconfig.json",
     "verify": "npm run build && node scripts/check-charter.mjs && node scripts/verify-four-layer.mjs && node scripts/generate-sweep.mjs && node scripts/verify-sweep.mjs && node scripts/verify-cross-family.mjs && node scripts/verify-ua-styles.mjs && node scripts/verify-rect-contract.mjs && node scripts/verify-stress.mjs",
-    "verify:all": "npm run build && node scripts/check-charter.mjs && node scripts/verify-four-layer.mjs && node scripts/generate-sweep.mjs && node scripts/verify-sweep.mjs && node scripts/verify-cross-family.mjs && node scripts/verify-ua-styles.mjs && node scripts/verify-text-measure.mjs && node scripts/verify-calc.mjs && node scripts/verify-shadow.mjs && node scripts/verify-opacity.mjs && node scripts/verify-layers.mjs && node scripts/verify-paint-text.mjs && node scripts/verify-border-radius.mjs && node scripts/verify-layout-flexbox.mjs && node scripts/verify-layout-floats.mjs && node scripts/verify-layout-grid.mjs && node scripts/verify-layout-inline-block.mjs && node scripts/verify-layout-positioning.mjs && node scripts/verify-lists.mjs && node scripts/verify-media-queries.mjs && node scripts/verify-pseudo-elements.mjs && node scripts/verify-report.mjs && node scripts/verify-segmenter.mjs && node scripts/verify-text-align.mjs && node scripts/verify-white-space.mjs && node scripts/verify-firefox.mjs && node scripts/verify-font-registration.mjs && node scripts/verify-overflow.mjs && node scripts/verify-breaker.mjs && node scripts/verify-comments.mjs && node scripts/verify-rect-contract.mjs && node scripts/verify-stress.mjs",
+    "verify:all": "npm run build && tsc -p scripts/tsconfig.json && tsc -p scripts/tsconfig.all.json && node scripts/check-charter.mjs && node scripts/verify-four-layer.mjs && node scripts/generate-sweep.mjs && node scripts/verify-sweep.mjs && node scripts/verify-cross-family.mjs && node scripts/verify-ua-styles.mjs && node scripts/verify-text-measure.mjs && node scripts/verify-calc.mjs && node scripts/verify-shadow.mjs && node scripts/verify-opacity.mjs && node scripts/verify-layers.mjs && node scripts/verify-paint-text.mjs && node scripts/verify-border-radius.mjs && node scripts/verify-layout-flexbox.mjs && node scripts/verify-layout-floats.mjs && node scripts/verify-layout-grid.mjs && node scripts/verify-layout-inline-block.mjs && node scripts/verify-layout-positioning.mjs && node scripts/verify-lists.mjs && node scripts/verify-media-queries.mjs && node scripts/verify-pseudo-elements.mjs && node scripts/verify-report.mjs && node scripts/verify-segmenter.mjs && node scripts/verify-text-align.mjs && node scripts/verify-white-space.mjs && node scripts/verify-firefox.mjs && node scripts/verify-font-registration.mjs && node scripts/verify-overflow.mjs && node scripts/verify-breaker.mjs && node scripts/verify-comments.mjs && node scripts/verify-rect-contract.mjs && node scripts/verify-stress.mjs && node scripts/verify-float-content.mjs && node scripts/verify-atomic-perf.mjs",
     "verify:four-layer": "npm run build && node scripts/verify-four-layer.mjs",
     "verify:border-radius": "npm run build && node scripts/verify-border-radius.mjs",
     "verify:overflow": "npm run build && node scripts/verify-overflow.mjs",
@@ -51,6 +51,9 @@
     "verify:property-coverage": "npm run build && node scripts/verify-property-coverage.mjs",
     "verify:breaker": "npm run build && node scripts/verify-breaker.mjs",
     "verify:comments": "npm run build && node scripts/verify-comments.mjs",
+    "typecheck:scripts": "npm run build && tsc -p scripts/tsconfig.json && tsc -p scripts/tsconfig.all.json",
+    "verify:float-content": "npm run build && node scripts/verify-float-content.mjs",
+    "verify:atomic-perf": "npm run build && node scripts/verify-atomic-perf.mjs",
     "probe:browser-gap": "npm run build && node probes/probe-browser-gap.mjs",
     "bench:engine-vs-oracle": "npm run build && node scripts/bench-engine-vs-oracle.mjs",
     "test:probe": "npm run build && node --test probes/probe-gap-lib.test.mjs",
diff --git a/scripts/bench-engine-vs-oracle.mjs b/scripts/bench-engine-vs-oracle.mjs
index 208d3b0..d1d14c4 100644
--- a/scripts/bench-engine-vs-oracle.mjs
+++ b/scripts/bench-engine-vs-oracle.mjs
@@ -98,19 +98,19 @@ async function measureChromeRender(browser, raw) {
   const h = raw.harvest;
   const page = await browser.newPage({ viewport: { width: h.viewport.width, height: h.viewport.height } });
   await page.addInitScript(() => {
-    window.__paints = [];
+    (/** @type {any} */ (window)).__paints = [];
     try {
       new PerformanceObserver((list) => {
-        for (const e of list.getEntries()) window.__paints.push({ name: e.name, startTime: e.startTime });
+        for (const e of list.getEntries()) (/** @type {any} */ (window)).__paints.push({ name: e.name, startTime: e.startTime });
       }).observe({ type: 'paint' });
     } catch (e) {
-      window.__paints.push({ name: 'observer-error', startTime: 0 });
+      (/** @type {any} */ (window)).__paints.push({ name: 'observer-error', startTime: 0 });
     }
   });
   await page.goto('data:text/html;charset=utf-8,' + encodeURIComponent(h.html));
   await page.evaluate(() => document.fonts.ready);
   await page.waitForTimeout(50);
-  const paints = await page.evaluate(() => window.__paints);
+  const paints = await page.evaluate(() => (/** @type {any} */ (window)).__paints);
   const fcp = paints.find((e) => e.name === 'first-contentful-paint') ?? paints.find((e) => e.name === 'first-paint');
   await page.close();
   if (!fcp) throw new Error(`fixture ${raw.name}: no paint timing entry observed`);
diff --git a/scripts/check-charter.mjs b/scripts/check-charter.mjs
index 19a12e9..4f5461d 100644
--- a/scripts/check-charter.mjs
+++ b/scripts/check-charter.mjs
@@ -61,7 +61,7 @@ const requires = [
 ];
 
 for (const [label, re] of requires) {
-  if (!re.test(charter)) fail(`charter.md missing: ${label}`);
+  if (!(/** @type {RegExp} */ (re)).test(charter)) fail(`charter.md missing: ${label}`);
 }
 
 // --- corpus gap-fixture schema (improvement-plan §4) ---
diff --git a/scripts/generate-sweep.mjs b/scripts/generate-sweep.mjs
index cf2772e..755247b 100644
--- a/scripts/generate-sweep.mjs
+++ b/scripts/generate-sweep.mjs
@@ -67,7 +67,7 @@ try {
     const viewport = combo.viewport;
     const page = await browser.newPage({ viewport: { width: viewport.width, height: viewport.height } });
     await page.setContent(combo.html);
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of combo.rects) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -100,9 +100,9 @@ try {
       width: refImg.width,
       height: refImg.height,
     };
-    const harness = evaluateFixture(fixture);
-    const rectLayer = harness.layers.rect;
-    const shotLayer = harness.layers.screenshot;
+    const harness = evaluateFixture(/** @type {import('../dist/harness/fixtures.js').Fixture} */ (fixture));
+    const rectLayer = /** @type {import('../dist/harness/evaluate.js').RectLayerResult} */ (harness.layers.rect);
+    const shotLayer = /** @type {import('../dist/harness/evaluate.js').ScreenshotLayerResult} */ (harness.layers.screenshot);
 
     const expected = { measureText: 'pass', computedStyle: 'pass' };
     expected.rect = rectLayer.pass ? 'pass' : gapFor(combo.label);
diff --git a/scripts/lib/render.mjs b/scripts/lib/render.mjs
new file mode 100644
index 0000000..dab7b14
--- /dev/null
+++ b/scripts/lib/render.mjs
@@ -0,0 +1,46 @@
+/**
+ * Shared render harness for the engine-only verify gates (no browser oracle):
+ * the FONT_FILE / FONT_FAMILY fallbacks, the document wrapper, and a typed
+ * `render(body)` over `renderHtml`. Centralizing this keeps each gate to just
+ * its assertions and gives the gates a single typed surface — `renderHtml`
+ * options are checked against the engine's own `RenderOptions` type (see
+ * scripts/tsconfig.json).
+ *
+ * The repo default font is the bundled Hack face, so these gates need no system
+ * fonts; FONT_FILE / FONT_FAMILY still override it (matching the oracle gates).
+ */
+import { resolve } from 'node:path';
+import { renderHtml } from '../../dist/index.js';
+
+export const FONT_FILE = process.env.FONT_FILE ?? resolve('fonts/HackNerdFont-Regular.ttf');
+export const FONT_FAMILY = process.env.FONT_FAMILY ?? 'Hack Nerd Font';
+
+/**
+ * Wrap body markup in a minimal document with a zero-margin body at the shared
+ * font. `style` is extra CSS appended to the body rule's stylesheet.
+ * @param {string} body
+ * @param {string} [style]
+ * @returns {string}
+ */
+export function doc(body, style = '') {
+  return `<!doctype html><html><head><style>body{margin:0;font:16px '${FONT_FAMILY}'}${style}</style></head><body>${body}</body></html>`;
+}
+
+/**
+ * Render body markup through the engine at the given viewport.
+ * @param {string} body
+ * @param {{ width?: number, height?: number, style?: string }} [opts]
+ */
+export function render(body, opts = {}) {
+  const { width = 800, height = 600, style = '' } = opts;
+  return renderHtml(doc(body, style), { width, height, fontFamily: FONT_FAMILY, fontFile: FONT_FILE });
+}
+
+/**
+ * Normalize a caught value (typed `unknown` under strict) to a message string.
+ * @param {unknown} e
+ * @returns {string}
+ */
+export function errorMessage(e) {
+  return e instanceof Error ? e.message : String(e);
+}
diff --git a/scripts/tsconfig.all.json b/scripts/tsconfig.all.json
new file mode 100644
index 0000000..01ffc09
--- /dev/null
+++ b/scripts/tsconfig.all.json
@@ -0,0 +1,21 @@
+{
+  "//": "Broad type-check for the remaining scripts (npm run typecheck:scripts runs this after the strict gate config). checkJs against dist/*.d.ts catches the errors that matter for test code — a wrong renderHtml/BrowserConfig option, a wrong harness field or property — across the oracle/bench/generator scripts. noImplicitAny and strictNullChecks are relaxed here (the strict tier in tsconfig.json covers the engine-only gates): the oracle scripts run untyped browser-context code inside page.evaluate and build result objects dynamically, where per-parameter annotations and DOM null-guards are noise rather than signal. As scripts are hardened they can graduate to the strict tier.",
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "..",
+    "noEmit": true,
+    "allowJs": true,
+    "checkJs": true,
+    "declaration": false,
+    "sourceMap": false,
+    "noImplicitAny": false,
+    "strictNullChecks": false
+  },
+  "include": ["**/*.mjs"],
+  "exclude": [
+    "lib/render.mjs",
+    "verify-comments.mjs",
+    "verify-float-content.mjs",
+    "verify-atomic-perf.mjs"
+  ]
+}
diff --git a/scripts/tsconfig.json b/scripts/tsconfig.json
new file mode 100644
index 0000000..575b2ad
--- /dev/null
+++ b/scripts/tsconfig.json
@@ -0,0 +1,19 @@
+{
+  "//": "Type-checks the engine-only verify gates and their shared harness (npm run typecheck:scripts). checkJs brings the src/ strict safety net to the .mjs gates that pin the engine's behavior, without converting all of scripts/ at once. renderHtml options and RenderOutput fields are checked against dist/*.d.ts, so a mistyped option or a wrong rects field is caught before runtime. Add new engine-only gates and lib helpers to `include` as they land.",
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "..",
+    "noEmit": true,
+    "allowJs": true,
+    "checkJs": true,
+    "declaration": false,
+    "sourceMap": false
+  },
+  "include": [
+    "lib/render.mjs",
+    "verify-comments.mjs",
+    "verify-float-content.mjs",
+    "verify-atomic-perf.mjs"
+  ],
+  "exclude": []
+}
diff --git a/scripts/verify-atomic-perf.mjs b/scripts/verify-atomic-perf.mjs
new file mode 100644
index 0000000..0756cac
--- /dev/null
+++ b/scripts/verify-atomic-perf.mjs
@@ -0,0 +1,54 @@
+#!/usr/bin/env node
+/**
+ * `npm run verify:atomic-perf`
+ *
+ * Intrinsic sizing / measurement of inline-block ("atomic") boxes used to be
+ * unmemoized: sizing an auto-width inline-block measures its whole subtree, and
+ * every atomic was measured once for line-breaking and again for placement — so
+ * nested inline-blocks re-measured every level below them, twice, giving
+ * O(2^depth) work. Deeply nested inline-blocks (a real WPT flex reference, or
+ * the progressive nesting a stray self-closing `<div/>` produces in the HTML
+ * parser) hung the engine for minutes / OOM-killed the process.
+ *
+ * atomicBoxSize/measureAtomic are now memoized per (element, width), which is
+ * linear. This gate renders pathological nesting and asserts it finishes fast;
+ * the pre-fix engine could not complete depth 14 in two minutes.
+ */
+import assert from 'node:assert/strict';
+import { render, errorMessage } from './lib/render.mjs';
+
+const BUDGET_MS = Number(process.env.ATOMIC_BUDGET_MS ?? 5000); // generous; pre-fix hung > 120s at depth 14
+
+let pass = 0;
+/** @type {string[]} */
+const fails = [];
+/** @param {string} name @param {string} body */
+const timed = (name, body) => {
+  const t = Date.now();
+  try { render(body); } catch (e) { fails.push(`${name}: threw ${errorMessage(e)}`); return; }
+  const ms = Date.now() - t;
+  if (ms > BUDGET_MS) fails.push(`${name}: took ${ms}ms > ${BUDGET_MS}ms budget (exponential regression?)`);
+  else { pass++; console.log(`  ${name}: ${ms}ms`); }
+};
+
+// Deep nested inline-blocks — the exponential shape.
+let ib = 'x';
+for (let i = 0; i < 200; i++) ib = `<span style="display:inline-block">${ib}</span>`;
+timed('nested inline-block depth 200', ib);
+
+// Progressive nesting from self-closing <div/> in HTML parsing (the WPT ref).
+let sc = '';
+for (let i = 0; i < 80; i++) sc += `<div style="line-height:0"><div style="display:inline-block;width:10px;height:10px"/><div style="display:inline-block;width:50px;height:10px"/></div>`;
+timed('80 self-closing-div blocks', sc);
+
+// Correctness: memoization must not change layout — deep nesting still resolves.
+try {
+  const r = render(`<span id="o" style="display:inline-block"><span id="i" style="display:inline-block;width:30px;height:12px"></span></span>`).rects;
+  assert.ok(r.o && r.i && r.i.width === 30, 'nested inline-block rects wrong');
+  pass++;
+} catch (e) { fails.push(`nested rect correctness: ${errorMessage(e)}`); }
+
+for (const f of fails) console.log(`FAIL ${f}`);
+console.log(`${pass}/${pass + fails.length} atomic-perf checks passed`);
+if (fails.length) { console.error('verify:atomic-perf: FAIL'); process.exit(1); }
+console.log('verify:atomic-perf: PASS');
diff --git a/scripts/verify-border-radius.mjs b/scripts/verify-border-radius.mjs
index b5e2b5e..189b14b 100644
--- a/scripts/verify-border-radius.mjs
+++ b/scripts/verify-border-radius.mjs
@@ -86,7 +86,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -94,7 +94,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -108,7 +108,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -156,7 +156,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-breaker.mjs b/scripts/verify-breaker.mjs
index e9235df..f364fc8 100644
--- a/scripts/verify-breaker.mjs
+++ b/scripts/verify-breaker.mjs
@@ -98,6 +98,7 @@ if (fontsByFamily.size === 0) {
   console.error(`verify:breaker: no fixtures found under ${corpus}`);
   process.exit(1);
 }
+/** @type {import('../dist/index.js').BrowserConfig} */
 const config = {
   browser: 'chrome',
   fonts: [...fontsByFamily.values()],
diff --git a/scripts/verify-calc.mjs b/scripts/verify-calc.mjs
index 7336d7d..942f57e 100644
--- a/scripts/verify-calc.mjs
+++ b/scripts/verify-calc.mjs
@@ -51,7 +51,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -97,7 +97,7 @@ try {
       height,
     };
 
-    results.push(evaluateFixture(fixture));
+    results.push(evaluateFixture(/** @type {import('../dist/harness/fixtures.js').Fixture} */ (fixture)));
     console.log(`verified ${name}: ${width}x${height}`);
   }
 } finally {
diff --git a/scripts/verify-comments.mjs b/scripts/verify-comments.mjs
index 05307f7..5d37338 100644
--- a/scripts/verify-comments.mjs
+++ b/scripts/verify-comments.mjs
@@ -19,17 +19,10 @@
  */
 
 import assert from 'node:assert/strict';
-import { resolve } from 'node:path';
-import { renderHtml } from '../dist/index.js';
+import { render as renderAt, errorMessage } from './lib/render.mjs';
 
-const FONT_FILE = process.env.FONT_FILE ?? resolve('fonts/HackNerdFont-Regular.ttf');
-const FONT_FAMILY = process.env.FONT_FAMILY ?? 'Hack Nerd Font';
-
-const doc = (body, style = '') =>
-  `<!doctype html><html><head><style>body{margin:0;font:16px '${FONT_FAMILY}'}${style}</style></head><body>${body}</body></html>`;
-
-const render = (body, style) =>
-  renderHtml(doc(body, style), { width: 400, height: 300, fontFamily: FONT_FAMILY, fontFile: FONT_FILE });
+/** @param {string} body @param {string} [style] */
+const render = (body, style = '') => renderAt(body, { width: 400, height: 300, style });
 
 // Each case: [name, withoutComments, withComments, style]. The two markups must
 // lay out identically — the only difference is interleaved comment nodes.
@@ -61,6 +54,7 @@ const cases = [
 ];
 
 let pass = 0;
+/** @type {string[]} */
 const fails = [];
 
 // Property 1 + 2 over the matrix.
@@ -70,7 +64,7 @@ for (const [name, plain, commented, style] of cases) {
     base = render(plain, style);
     withc = render(commented, style);
   } catch (e) {
-    fails.push(`${name}: threw ${e.message}`);
+    fails.push(`${name}: threw ${errorMessage(e)}`);
     continue;
   }
   try {
@@ -86,7 +80,7 @@ try {
   render(`<!-- a comment --><p id="a">hi</p>`);
   pass++;
 } catch (e) {
-  fails.push(`original repro still throws: ${e.message}`);
+  fails.push(`original repro still throws: ${errorMessage(e)}`);
 }
 
 const total = cases.length + 1;
diff --git a/scripts/verify-cross-family.mjs b/scripts/verify-cross-family.mjs
index b5484f9..b947732 100644
--- a/scripts/verify-cross-family.mjs
+++ b/scripts/verify-cross-family.mjs
@@ -101,7 +101,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -109,7 +109,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -123,7 +123,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -173,7 +173,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
@@ -238,7 +238,7 @@ try {
       height,
     };
 
-    results.push(evaluateFixture(fixture));
+    results.push(evaluateFixture(/** @type {import('../dist/harness/fixtures.js').Fixture} */ (fixture)));
     console.log(`verified ${name} (${target}): ${width}x${height}, ${fragments.length} text fragments, ${mask.some((b) => b === 1) ? 'masked' : 'no mask'}`);
   }
 } finally {
diff --git a/scripts/verify-firefox.mjs b/scripts/verify-firefox.mjs
index 5a319fc..a44df79 100644
--- a/scripts/verify-firefox.mjs
+++ b/scripts/verify-firefox.mjs
@@ -130,7 +130,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -138,7 +138,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -152,7 +152,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -208,7 +208,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-float-content.mjs b/scripts/verify-float-content.mjs
new file mode 100644
index 0000000..45bb98e
--- /dev/null
+++ b/scripts/verify-float-content.mjs
@@ -0,0 +1,59 @@
+#!/usr/bin/env node
+/**
+ * `npm run verify:float-content`
+ *
+ * A float used to lay out only its inline content: `layoutFloat` walked text
+ * lines and set `children: []`, so block-level or floated descendants of a
+ * float were dropped. Because the engine asserts rect-completeness (every
+ * id-bearing element must get a rect), any float containing a block/floated
+ * child with an id crashed the whole render ("no rect collected for id(s)").
+ * This is common real markup (a floated card/sidebar with block content, the
+ * Acid1 shape of floated list items inside a floated container).
+ *
+ * This gate asserts such documents render, and that the inner block/float
+ * children get sensible rects inside the float. Uses the repo-bundled font, no
+ * browser oracle.
+ */
+import assert from 'node:assert/strict';
+import { render, errorMessage } from './lib/render.mjs';
+
+/** @param {string} body */
+const at = (body) => render(body, { width: 400, height: 300 });
+
+let pass = 0;
+/** @type {string[]} */
+const fails = [];
+/** @param {string} name @param {() => void} fn */
+const check = (name, fn) => { try { fn(); pass++; } catch (e) { fails.push(`${name}: ${errorMessage(e)}`); } };
+
+// 1. Block child of a float gets a rect inside the float.
+check('block child of float', () => {
+  const r = at(`<div style="float:left;width:100px;padding:10px"><div id="inner" style="height:20px">x</div></div>`).rects;
+  assert.ok(r.inner, 'inner block has no rect');
+  assert.equal(r.inner.x, 10, 'inner x should sit at float padding');
+  assert.equal(r.inner.width, 100, 'inner block fills float content width');
+});
+
+// 2. Float nested inside a float gets a rect (the original crash / Acid1 shape).
+check('float nested in float', () => {
+  const r = at(`<div style="float:right;width:120px"><div id="nf" style="float:left;width:20px;height:20px">b</div></div>`).rects;
+  assert.ok(r.nf, 'nested float has no rect');
+  assert.equal(r.nf.width, 20);
+});
+
+// 3. Floated list items inside a floated container (Acid1-like) all render.
+check('floated list items in floated container', () => {
+  const r = at(`<div style="float:right;width:200px"><ul style="margin:0;padding:0"><li id="a" style="float:left;width:40px;height:20px">a</li><li id="b" style="float:left;width:40px;height:20px">b</li></ul></div>`).rects;
+  assert.ok(r.a && r.b, 'floated list items missing rects');
+});
+
+// 4. Inline-only floats are unchanged (no regression to the existing path).
+check('inline float still works', () => {
+  const r = at(`<div id="f" style="float:left;width:80px;height:30px">hello</div>`).rects;
+  assert.ok(r.f && r.f.width === 80 && r.f.height === 30, 'inline float rect changed');
+});
+
+for (const f of fails) console.log(`FAIL ${f}`);
+console.log(`${pass}/${pass + fails.length} float-content checks passed`);
+if (fails.length) { console.error('verify:float-content: FAIL'); process.exit(1); }
+console.log('verify:float-content: PASS');
diff --git a/scripts/verify-four-layer.mjs b/scripts/verify-four-layer.mjs
index 579424b..82f5512 100644
--- a/scripts/verify-four-layer.mjs
+++ b/scripts/verify-four-layer.mjs
@@ -120,7 +120,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -128,7 +128,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -142,7 +142,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -196,7 +196,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-layout-flexbox.mjs b/scripts/verify-layout-flexbox.mjs
index 280b3ca..2abad13 100644
--- a/scripts/verify-layout-flexbox.mjs
+++ b/scripts/verify-layout-flexbox.mjs
@@ -86,7 +86,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -94,7 +94,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -140,7 +140,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-layout-floats.mjs b/scripts/verify-layout-floats.mjs
index cd68797..05de9c2 100644
--- a/scripts/verify-layout-floats.mjs
+++ b/scripts/verify-layout-floats.mjs
@@ -88,7 +88,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -96,7 +96,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -142,7 +142,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-layout-grid.mjs b/scripts/verify-layout-grid.mjs
index 3d4b062..157b6a8 100644
--- a/scripts/verify-layout-grid.mjs
+++ b/scripts/verify-layout-grid.mjs
@@ -86,7 +86,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -94,7 +94,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -140,7 +140,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-layout-inline-block.mjs b/scripts/verify-layout-inline-block.mjs
index f027644..e8da496 100644
--- a/scripts/verify-layout-inline-block.mjs
+++ b/scripts/verify-layout-inline-block.mjs
@@ -88,7 +88,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -96,7 +96,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -110,7 +110,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -158,7 +158,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-layout-positioning.mjs b/scripts/verify-layout-positioning.mjs
index b97a543..e9e5e6e 100644
--- a/scripts/verify-layout-positioning.mjs
+++ b/scripts/verify-layout-positioning.mjs
@@ -87,7 +87,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -95,7 +95,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -141,7 +141,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-lists.mjs b/scripts/verify-lists.mjs
index 6c9789a..a5c84dd 100644
--- a/scripts/verify-lists.mjs
+++ b/scripts/verify-lists.mjs
@@ -149,7 +149,7 @@ try {
     await page.evaluate(() => document.fonts.ready);
 
     // --- Chrome oracle quantities ---
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -157,7 +157,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -171,7 +171,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -224,7 +224,7 @@ try {
 
     const candidateRects = out.rects;
     const candidateComputed = out.computedStyles;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-opacity.mjs b/scripts/verify-opacity.mjs
index 3029370..0639908 100644
--- a/scripts/verify-opacity.mjs
+++ b/scripts/verify-opacity.mjs
@@ -78,7 +78,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -86,7 +86,7 @@ try {
       });
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
diff --git a/scripts/verify-overflow.mjs b/scripts/verify-overflow.mjs
index be2dd33..f269194 100644
--- a/scripts/verify-overflow.mjs
+++ b/scripts/verify-overflow.mjs
@@ -85,7 +85,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -93,7 +93,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -107,7 +107,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -155,7 +155,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-paint-text.mjs b/scripts/verify-paint-text.mjs
index 6a70594..0b06d00 100644
--- a/scripts/verify-paint-text.mjs
+++ b/scripts/verify-paint-text.mjs
@@ -127,7 +127,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -135,7 +135,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -189,7 +189,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     const paintRuns = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
diff --git a/scripts/verify-property-coverage.mjs b/scripts/verify-property-coverage.mjs
index ba500e2..6a60334 100644
--- a/scripts/verify-property-coverage.mjs
+++ b/scripts/verify-property-coverage.mjs
@@ -113,7 +113,7 @@ for (const f of fixturesToRender) {
     rectsOf(f.html, { width: 800, height: 600, fontFamily: FONT_FAMILY, fontFile: FONT_FILE });
     rendered++;
   } catch (err) {
-    console.error(`verify-property-coverage: fixture ${f.name} failed to render: ${err.message}`);
+    console.error(`verify-property-coverage: fixture ${f.name} failed to render: ${(/** @type {Error} */ (err)).message}`);
     process.exit(1);
   }
 }
diff --git a/scripts/verify-pseudo-elements.mjs b/scripts/verify-pseudo-elements.mjs
index 2aac9ba..be45339 100644
--- a/scripts/verify-pseudo-elements.mjs
+++ b/scripts/verify-pseudo-elements.mjs
@@ -101,7 +101,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -109,7 +109,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -123,7 +123,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, pseudo, props } of h.computedStyle) {
         const key = pseudo ? `${id}::${pseudo}` : id;
@@ -172,7 +172,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-rect-contract.mjs b/scripts/verify-rect-contract.mjs
index 3875fb0..dc076a2 100644
--- a/scripts/verify-rect-contract.mjs
+++ b/scripts/verify-rect-contract.mjs
@@ -43,7 +43,7 @@ let out;
 try {
   out = renderHtml(HTML, opts);
 } catch (err) {
-  console.error(`FAIL: renderHtml threw — 'no rect collected' must not fire for DOM-present ids: ${err.message}`);
+  console.error(`FAIL: renderHtml threw — 'no rect collected' must not fire for DOM-present ids: ${(/** @type {Error} */ (err)).message}`);
   process.exit(1);
 }
 
diff --git a/scripts/verify-rtl.mjs b/scripts/verify-rtl.mjs
index 2d6005f..fd9d3f0 100644
--- a/scripts/verify-rtl.mjs
+++ b/scripts/verify-rtl.mjs
@@ -70,6 +70,7 @@ try {
       fixtureFonts.find((f) => f.family === defaultFamily)?.filePath ??
       cfg.fonts.find((f) => f.family === defaultFamily)?.filePath ??
       FONT_FILE;
+    /** @type {import('../dist/index.js').BrowserConfig} */
     const browserConfig = {
       browser: 'chrome',
       fonts: [...cfg.fonts, ...fixtureFonts],
@@ -82,7 +83,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -90,7 +91,7 @@ try {
       });
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -105,7 +106,7 @@ try {
       }
     }
 
-    const referenceFragments = {};
+    /** @type {Record<string, any>} */ const referenceFragments = {};
     if (h.textElements && h.textElements.length > 0) {
       for (const id of h.textElements) {
         referenceFragments[id] = await page.evaluate((id) => {
diff --git a/scripts/verify-segmenter.mjs b/scripts/verify-segmenter.mjs
index a7980f7..92e45f0 100644
--- a/scripts/verify-segmenter.mjs
+++ b/scripts/verify-segmenter.mjs
@@ -93,7 +93,7 @@ for (const { raw } of fixtureList) {
     try {
       skiaCanvasFactory.registerFont(f.file, f.family);
     } catch (err) {
-      failFast(`font registration failed for '${f.family}': ${err.message}`);
+      failFast(`font registration failed for '${f.family}': ${(/** @type {Error} */ (err)).message}`);
     }
     registeredFamilies.add(f.family);
   }
@@ -162,8 +162,8 @@ try {
       res.end('not found');
     }
   });
-  await new Promise((r) => server.listen(0, '127.0.0.1', r));
-  const baseUrl = `http://127.0.0.1:${server.address().port}`;
+  await new Promise((r) => server.listen(0, '127.0.0.1', () => r()));
+  const baseUrl = `http://127.0.0.1:${(/** @type {import('net').AddressInfo} */ (server.address())).port}`;
   await page.goto(`${baseUrl}/`);
 
   const layoutRequests = fixtureList.flatMap(({ raw }) =>
diff --git a/scripts/verify-shadow.mjs b/scripts/verify-shadow.mjs
index b3612a4..11c90e0 100644
--- a/scripts/verify-shadow.mjs
+++ b/scripts/verify-shadow.mjs
@@ -86,7 +86,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -94,7 +94,7 @@ try {
       });
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
diff --git a/scripts/verify-stress.mjs b/scripts/verify-stress.mjs
index 8870bcb..5da7eef 100644
--- a/scripts/verify-stress.mjs
+++ b/scripts/verify-stress.mjs
@@ -104,7 +104,7 @@ try {
       await page.setContent(h.html);
       await page.evaluate(() => document.fonts.ready);
 
-      const referenceRects = {};
+      /** @type {Record<string, any>} */ const referenceRects = {};
       for (const id of h.rects ?? []) {
         referenceRects[id] = await page.$eval(`#${id}`, (el) => {
           const r = el.getBoundingClientRect();
@@ -112,7 +112,7 @@ try {
         });
       }
 
-      const referenceMeasure = {};
+      /** @type {Record<string, any>} */ const referenceMeasure = {};
       if (h.measureText) {
         for (const { text, font } of h.measureText) {
           referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -126,7 +126,7 @@ try {
         }
       }
 
-      const referenceComputed = {};
+      /** @type {Record<string, any>} */ const referenceComputed = {};
       if (specs.length > 0) {
         for (const { id, pseudo, props } of specs) {
           const key = pseudo ? `${id}::${pseudo}` : id;
@@ -175,7 +175,7 @@ try {
       const candImg = decodePng(out.rgba);
 
       const candidateRects = out.rects;
-      const candidateMeasure = {};
+      /** @type {Record<string, any>} */ const candidateMeasure = {};
       if (h.measureText) {
         const { measureTextWidth } = await import('../dist/layout/measure.js');
         for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-sweep.mjs b/scripts/verify-sweep.mjs
index a7ccaa2..71120b7 100644
--- a/scripts/verify-sweep.mjs
+++ b/scripts/verify-sweep.mjs
@@ -61,7 +61,7 @@ try {
       await page.setContent(h.html);
       await page.evaluate(() => document.fonts.ready);
 
-      const referenceRects = {};
+      /** @type {Record<string, any>} */ const referenceRects = {};
       for (const id of h.rects ?? []) {
         referenceRects[id] = await page.$eval(`#${id}`, (el) => {
           const r = el.getBoundingClientRect();
@@ -112,10 +112,10 @@ try {
         height,
       };
 
-      const result = evaluateFixture(fixture);
+      const result = evaluateFixture(/** @type {import('../dist/harness/fixtures.js').Fixture} */ (fixture));
       results.push(result);
-      const rectLayer = result.layers.rect;
-      const shotLayer = result.layers.screenshot;
+      const rectLayer = /** @type {import('../dist/harness/evaluate.js').RectLayerResult} */ (result.layers.rect);
+      const shotLayer = /** @type {import('../dist/harness/evaluate.js').ScreenshotLayerResult} */ (result.layers.screenshot);
       const gapLayers = ['rect', 'screenshot'].filter((l) => isGapExpectation(raw.expected?.[l]));
       rows.push({
         fixture: name,
diff --git a/scripts/verify-text-align.mjs b/scripts/verify-text-align.mjs
index 9aa2488..fe2f099 100644
--- a/scripts/verify-text-align.mjs
+++ b/scripts/verify-text-align.mjs
@@ -105,7 +105,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -113,7 +113,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -127,7 +127,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -175,7 +175,7 @@ try {
 
     const candidateRects = out.rects;
     const candidateComputed = out.computedStyles;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-text-measure.mjs b/scripts/verify-text-measure.mjs
index 36b3298..ae277b2 100644
--- a/scripts/verify-text-measure.mjs
+++ b/scripts/verify-text-measure.mjs
@@ -62,7 +62,7 @@ for (const { name, raw } of fixtures()) {
     try {
       skiaCanvasFactory.registerFont(f.file, f.family);
     } catch (err) {
-      console.error(`verify:text-measure: failed to register font '${f.family}' from ${f.file}: ${err.message}`);
+      console.error(`verify:text-measure: failed to register font '${f.family}' from ${f.file}: ${(/** @type {Error} */ (err)).message}`);
       process.exit(1);
     }
     registeredFamilies.add(f.family);
@@ -148,7 +148,7 @@ try {
 
     // Harness layer-1 runner decides tolerance on the pass corpus of this fixture.
     const fixture = { name, tolerances, candidate, reference };
-    const layer = evaluateMeasureText(fixture);
+    const layer = evaluateMeasureText(/** @type {import('../dist/harness/fixtures.js').Fixture} */ (fixture));
 
     let checkPass;
     let detail;
diff --git a/scripts/verify-ua-styles.mjs b/scripts/verify-ua-styles.mjs
index 686b4f7..156e0a2 100644
--- a/scripts/verify-ua-styles.mjs
+++ b/scripts/verify-ua-styles.mjs
@@ -76,7 +76,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -84,7 +84,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -98,7 +98,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -149,7 +149,7 @@ try {
     const candImg = decodePng(out.rgba);
 
     const candidateRects = out.rects;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/scripts/verify-white-space.mjs b/scripts/verify-white-space.mjs
index 78bf0c0..d0c8f2a 100644
--- a/scripts/verify-white-space.mjs
+++ b/scripts/verify-white-space.mjs
@@ -132,7 +132,7 @@ try {
     await page.setContent(h.html);
     await page.evaluate(() => document.fonts.ready);
 
-    const referenceRects = {};
+    /** @type {Record<string, any>} */ const referenceRects = {};
     for (const id of h.rects ?? []) {
       referenceRects[id] = await page.$eval(`#${id}`, (el) => {
         const r = el.getBoundingClientRect();
@@ -140,7 +140,7 @@ try {
       });
     }
 
-    const referenceMeasure = {};
+    /** @type {Record<string, any>} */ const referenceMeasure = {};
     if (h.measureText) {
       for (const { text, font } of h.measureText) {
         referenceMeasure[`${font} | ${text}`] = await page.evaluate(
@@ -154,7 +154,7 @@ try {
       }
     }
 
-    const referenceComputed = {};
+    /** @type {Record<string, any>} */ const referenceComputed = {};
     if (h.computedStyle) {
       for (const { id, props } of h.computedStyle) {
         referenceComputed[id] = await page.evaluate(
@@ -202,7 +202,7 @@ try {
 
     const candidateRects = out.rects;
     const candidateComputed = out.computedStyles;
-    const candidateMeasure = {};
+    /** @type {Record<string, any>} */ const candidateMeasure = {};
     if (h.measureText) {
       const { measureTextWidth } = await import('../dist/layout/measure.js');
       for (const { text, font } of h.measureText) {
diff --git a/src/layout/block-inline.ts b/src/layout/block-inline.ts
index 168cfbe..0ba55f6 100644
--- a/src/layout/block-inline.ts
+++ b/src/layout/block-inline.ts
@@ -1149,11 +1149,17 @@ function layoutFloat(
   const bT = style.borderWidth.top;
   const bB = style.borderWidth.bottom;
 
+  const floatHasBlocks = hasBlockLevelChild(el, styles);
   const specW = resolveLength(style.width, contentWidth, viewport);
   const padBorderH = padL + padR + bL + bR;
   let borderBoxWidth: number;
   if (specW !== null) {
     borderBoxWidth = style.boxSizing === 'border-box' ? specW : specW + padBorderH;
+  } else if (floatHasBlocks) {
+    // Auto-width float with block-level content: approximate shrink-to-fit with
+    // the available inline width. A full max-content pass over block descendants
+    // is future work; explicit widths — the common case — are exact.
+    borderBoxWidth = Math.max(0, contentWidth - marginL - marginR);
   } else {
     const text = collectInlineText(el, styles).trim();
     const ls = style.letterSpacing;
@@ -1167,10 +1173,24 @@ function layoutFloat(
   }
   const floatContentWidth = Math.max(0, borderBoxWidth - bL - bR - padL - padR);
 
-  // Float content lays out in its own BFC (a fresh float list).
+  // Float content lays out in its own BFC (a fresh float list). Block-level
+  // children (including nested floats) go through the normal block-children
+  // path so they are sized, positioned, painted, and get rects; inline content
+  // uses the line layouter. A measurement pass sizes the float box here; the
+  // real positioned pass runs after placement (below) so the children paint
+  // above the float's own background.
   let contentHeight = 0;
   let lines: LineBox[] = [];
-  if (hasInlineContent(el, styles)) {
+  if (floatHasBlocks) {
+    const measFm = new FloatManager(0, floatContentWidth);
+    const measState: LayoutBlockInput = { fm: measFm, contentX: 0, contentWidth: floatContentWidth, y: 0, prevBottomMargin: 0, cbDirection: style.direction };
+    const snapshot = paints.length;
+    const meas = layoutBlockChildren(el, measState, styles, paints, nextOrder, viewport);
+    paints.length = snapshot;
+    contentHeight = meas.height;
+    const lowest = measFm.lowestFloatBottom('both');
+    if (Number.isFinite(lowest)) contentHeight = Math.max(contentHeight, lowest);
+  } else if (hasInlineContent(el, styles)) {
     const lineRes = layoutTextLines({
       text: collectInlineText(el, styles),
       x: 0,
@@ -1271,6 +1291,15 @@ function layoutFloat(
     });
   }
   pushBorders(paints, nextOrder, floatKey, style, placed.borderX, placed.borderY, borderBoxWidth, borderHeight);
+  if (floatHasBlocks) {
+    // Real, positioned block-children layout: at the placed content origin and
+    // after the float's background/border ops, so children paint on top. Their
+    // rects flow into the tree via node.children (collectRects walks it).
+    const childFm = new FloatManager(node.contentX, floatContentWidth);
+    const childState: LayoutBlockInput = { fm: childFm, contentX: node.contentX, contentWidth: floatContentWidth, y: node.contentY, prevBottomMargin: 0, cbDirection: style.direction };
+    const real = layoutBlockChildren(el, childState, styles, paints, nextOrder, viewport);
+    node.children.push(...real.nodes);
+  }
   if (lines.length > 0) {
     pushPaintOp(paints, {
       key: inFlowPaintKey(STEP_INLINE),
@@ -1817,6 +1846,33 @@ function isInlineBoxStyle(s: ComputedStyle): boolean {
   return s.display === 'inline-block' && s.float === 'none' && s.position === 'static';
 }
 
+/**
+ * Render-scoped memoization for atomic (inline-block) intrinsic sizing and
+ * measurement. Sizing an inline-block whose `width` is auto measures its whole
+ * subtree, and an atomic is measured once for line-breaking and again for
+ * placement — so with nested inline-blocks each level re-measures every level
+ * below it, twice, giving O(2^depth) work. Deeply nested inline-blocks (a real
+ * WPT flexbox reference, or the progressive nesting a stray self-closing
+ * `<div/>` produces in the HTML parser) then hang the engine outright.
+ *
+ * Both `atomicBoxSize` and `measureAtomic` are pure functions of
+ * `(element, width)` for a fixed render (styles/viewport are constant), so
+ * caching by width collapses the exponential to linear. Element objects are
+ * unique per `renderHtml` (each call re-parses), so a WeakMap keyed by element
+ * is inherently render-scoped and never yields a stale cross-render result.
+ */
+const atomicSizeMemo = new WeakMap<P5Element, Map<number, { borderWidth: number; contentWidth: number }>>();
+const measureAtomicMemo = new WeakMap<P5Element, Map<number, { borderHeight: number; baselineOffset: number | null }>>();
+
+function memoMapFor<V>(wm: WeakMap<P5Element, Map<number, V>>, el: P5Element): Map<number, V> {
+  let m = wm.get(el);
+  if (!m) {
+    m = new Map<number, V>();
+    wm.set(el, m);
+  }
+  return m;
+}
+
 function atomicBoxSize(
   el: P5Element,
   style: ComputedStyle,
@@ -1824,6 +1880,9 @@ function atomicBoxSize(
   refWidth: number,
   viewport: Viewport | undefined,
 ): { borderWidth: number; contentWidth: number } {
+  const memo = memoMapFor(atomicSizeMemo, el);
+  const hit = memo.get(refWidth);
+  if (hit) return hit;
   const padL = resolveLength(style.padding.left, refWidth, viewport) ?? 0;
   const padR = resolveLength(style.padding.right, refWidth, viewport) ?? 0;
   const bL = style.borderWidth.left;
@@ -1846,7 +1905,9 @@ function atomicBoxSize(
   const maxW = resolveLength(style.maxWidth, refWidth, viewport);
   if (minW !== null) borderWidth = Math.max(borderWidth, minW);
   if (maxW !== null) borderWidth = Math.min(borderWidth, maxW);
-  return { borderWidth, contentWidth: Math.max(0, borderWidth - padBorderH) };
+  const result = { borderWidth, contentWidth: Math.max(0, borderWidth - padBorderH) };
+  memo.set(refWidth, result);
+  return result;
 }
 
 function piecesContentSizes(pieces: InlinePiece[], style: ComputedStyle, ws: WhiteSpaceValue): { min: number; max: number } {
@@ -2056,6 +2117,14 @@ function measureAtomic(
   viewport: Viewport | undefined,
 ): MeasuredAtomic {
   const s = piece.style;
+  // Measurement is a throwaway layout (its paints are discarded below) that
+  // depends only on (element, contentWidth); memoize to avoid re-measuring the
+  // subtree once per line-break trial and once per placement (see
+  // atomicSizeMemo). Only the height/baseline are cached; the returned `piece`
+  // is the caller's current piece.
+  const memo = memoMapFor(measureAtomicMemo, piece.el);
+  const hit = memo.get(piece.contentWidth);
+  if (hit) return { piece, borderHeight: hit.borderHeight, baselineOffset: hit.baselineOffset };
   const padL = resolveLength(s.padding.left, piece.contentWidth, viewport) ?? 0;
   const padT = resolveLength(s.padding.top, piece.contentWidth, viewport) ?? 0;
   const bL = s.borderWidth.left;
@@ -2078,7 +2147,9 @@ function measureAtomic(
     viewport,
   );
   paints.length = snapshot;
-  return { piece, borderHeight: node.borderHeight, baselineOffset: atomicBaselineOffset(node, s) };
+  const measured = { borderHeight: node.borderHeight, baselineOffset: atomicBaselineOffset(node, s) };
+  memo.set(piece.contentWidth, measured);
+  return { piece, borderHeight: measured.borderHeight, baselineOffset: measured.baselineOffset };
 }
 
 /**