diff --git a/.github/workflows/quality.yml b/.github/workflows/quality.yml
index 2b9e21b2..922e6c5d 100644
--- a/.github/workflows/quality.yml
+++ b/.github/workflows/quality.yml
@@ -48,3 +48,6 @@ jobs:
 
       - name: Detect unused files and dependencies
         run: npm run knip
+
+      - name: Test
+        run: npm test
diff --git a/docs/package.json b/docs/package.json
index 95d1dc8b..a46e7095 100644
--- a/docs/package.json
+++ b/docs/package.json
@@ -6,6 +6,7 @@
     "dev": "astro dev --port 4322 --open",
     "build": "astro build",
     "preview": "astro preview",
+    "test": "node --test \"tests/**/*.test.js\"",
     "astro": "astro",
     "typecheck": "astro check",
     "format:check": "prettier --check src",
diff --git a/docs/public/features/posters/agentic-demo.jpg b/docs/public/features/posters/agentic-demo.jpg
deleted file mode 100644
index 901b5ee9..00000000
Binary files a/docs/public/features/posters/agentic-demo.jpg and /dev/null differ
diff --git a/docs/public/features/posters/agentic-demo.webp b/docs/public/features/posters/agentic-demo.webp
new file mode 100644
index 00000000..2a381d91
Binary files /dev/null and b/docs/public/features/posters/agentic-demo.webp differ
diff --git a/docs/public/features/posters/asc-drag-drop-demo.jpg b/docs/public/features/posters/asc-drag-drop-demo.jpg
deleted file mode 100644
index afdb831d..00000000
Binary files a/docs/public/features/posters/asc-drag-drop-demo.jpg and /dev/null differ
diff --git a/docs/public/features/posters/asc-drag-drop-demo.webp b/docs/public/features/posters/asc-drag-drop-demo.webp
new file mode 100644
index 00000000..1e9c77fd
Binary files /dev/null and b/docs/public/features/posters/asc-drag-drop-demo.webp differ
diff --git a/docs/public/features/posters/magnifier-color-picker.jpg b/docs/public/features/posters/magnifier-color-picker.jpg
deleted file mode 100644
index 7f77e18b..00000000
Binary files a/docs/public/features/posters/magnifier-color-picker.jpg and /dev/null differ
diff --git a/docs/public/features/posters/magnifier-color-picker.webp b/docs/public/features/posters/magnifier-color-picker.webp
new file mode 100644
index 00000000..aa112c17
Binary files /dev/null and b/docs/public/features/posters/magnifier-color-picker.webp differ
diff --git a/docs/public/features/posters/network-monitoring-demo.jpg b/docs/public/features/posters/network-monitoring-demo.jpg
deleted file mode 100644
index c985cc25..00000000
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diff --git a/docs/public/features/posters/network-monitoring-demo.webp b/docs/public/features/posters/network-monitoring-demo.webp
new file mode 100644
index 00000000..802ebaae
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diff --git a/docs/public/features/posters/onboarding-compare.jpg b/docs/public/features/posters/onboarding-compare.jpg
deleted file mode 100644
index 01097e29..00000000
Binary files a/docs/public/features/posters/onboarding-compare.jpg and /dev/null differ
diff --git a/docs/public/features/posters/onboarding-compare.webp b/docs/public/features/posters/onboarding-compare.webp
new file mode 100644
index 00000000..de3ff9e7
Binary files /dev/null and b/docs/public/features/posters/onboarding-compare.webp differ
diff --git a/docs/public/features/posters/physical-device-testing.jpg b/docs/public/features/posters/physical-device-testing.jpg
deleted file mode 100644
index 1806699d..00000000
Binary files a/docs/public/features/posters/physical-device-testing.jpg and /dev/null differ
diff --git a/docs/public/features/posters/physical-device-testing.webp b/docs/public/features/posters/physical-device-testing.webp
new file mode 100644
index 00000000..8a40102c
Binary files /dev/null and b/docs/public/features/posters/physical-device-testing.webp differ
diff --git a/docs/public/features/posters/quick-actions.jpg b/docs/public/features/posters/quick-actions.jpg
deleted file mode 100644
index 6b9bcfe8..00000000
Binary files a/docs/public/features/posters/quick-actions.jpg and /dev/null differ
diff --git a/docs/public/features/posters/quick-actions.webp b/docs/public/features/posters/quick-actions.webp
new file mode 100644
index 00000000..1ab1f61a
Binary files /dev/null and b/docs/public/features/posters/quick-actions.webp differ
diff --git a/docs/public/features/posters/recording-example.jpg b/docs/public/features/posters/recording-example.jpg
deleted file mode 100644
index 6ea9e7f3..00000000
Binary files a/docs/public/features/posters/recording-example.jpg and /dev/null differ
diff --git a/docs/public/features/posters/recording-example.webp b/docs/public/features/posters/recording-example.webp
new file mode 100644
index 00000000..13599da0
Binary files /dev/null and b/docs/public/features/posters/recording-example.webp differ
diff --git a/docs/public/features/posters/simulator-airplane-mode.jpg b/docs/public/features/posters/simulator-airplane-mode.jpg
deleted file mode 100644
index b428e21b..00000000
Binary files a/docs/public/features/posters/simulator-airplane-mode.jpg and /dev/null differ
diff --git a/docs/public/features/posters/simulator-airplane-mode.webp b/docs/public/features/posters/simulator-airplane-mode.webp
new file mode 100644
index 00000000..c67f2a05
Binary files /dev/null and b/docs/public/features/posters/simulator-airplane-mode.webp differ
diff --git a/docs/public/features/posters/simulator-camera.jpg b/docs/public/features/posters/simulator-camera.jpg
deleted file mode 100644
index ec2ed128..00000000
Binary files a/docs/public/features/posters/simulator-camera.jpg and /dev/null differ
diff --git a/docs/public/features/posters/simulator-camera.webp b/docs/public/features/posters/simulator-camera.webp
new file mode 100644
index 00000000..ca88bf01
Binary files /dev/null and b/docs/public/features/posters/simulator-camera.webp differ
diff --git a/docs/public/features/posters/slow-animations.jpg b/docs/public/features/posters/slow-animations.jpg
deleted file mode 100644
index 0d1ec061..00000000
Binary files a/docs/public/features/posters/slow-animations.jpg and /dev/null differ
diff --git a/docs/public/features/posters/slow-animations.webp b/docs/public/features/posters/slow-animations.webp
new file mode 100644
index 00000000..de39250d
Binary files /dev/null and b/docs/public/features/posters/slow-animations.webp differ
diff --git a/docs/public/features/posters/team-insights-dashboard.jpg b/docs/public/features/posters/team-insights-dashboard.jpg
deleted file mode 100644
index dd3be95d..00000000
Binary files a/docs/public/features/posters/team-insights-dashboard.jpg and /dev/null differ
diff --git a/docs/public/features/posters/team-insights-dashboard.webp b/docs/public/features/posters/team-insights-dashboard.webp
new file mode 100644
index 00000000..aa22cef6
Binary files /dev/null and b/docs/public/features/posters/team-insights-dashboard.webp differ
diff --git a/docs/public/features/posters/user-defaults-editor.jpg b/docs/public/features/posters/user-defaults-editor.jpg
deleted file mode 100644
index 38dd6061..00000000
Binary files a/docs/public/features/posters/user-defaults-editor.jpg and /dev/null differ
diff --git a/docs/public/features/posters/user-defaults-editor.webp b/docs/public/features/posters/user-defaults-editor.webp
new file mode 100644
index 00000000..15b6658f
Binary files /dev/null and b/docs/public/features/posters/user-defaults-editor.webp differ
diff --git a/docs/public/features/reencode-all.sh b/docs/public/features/reencode-all.sh
index edb4d869..5d9ed3f4 100755
--- a/docs/public/features/reencode-all.sh
+++ b/docs/public/features/reencode-all.sh
@@ -9,13 +9,16 @@
 #   - encodes H.264 (high profile, yuv420p) at CRF 28
 #   - drops the audio track (feature videos play muted)
 #   - moves the moov atom to the front (+faststart) for progressive streaming
-#   - exports the first frame to ./posters/<name>.jpg as a lightweight poster
+#   - exports the first frame to ./posters/<name>.webp as a lightweight poster
 #
 # .mov sources are converted to .mp4 and the original .mov is removed.
 # Re-encoding is idempotent enough to re-run; outputs replace the originals.
 
 set -euo pipefail
 
+# Requires ffmpeg (video encode) and cwebp (poster encode: brew install webp).
+command -v cwebp >/dev/null || { echo "cwebp not found — brew install webp"; exit 1; }
+
 INPUT_DIR="$(cd "$(dirname "$0")" && pwd)"
 POSTER_DIR="${INPUT_DIR}/posters"
 MAX_LONG_EDGE=1440
@@ -34,7 +37,7 @@ for file in "$INPUT_DIR"/*.mp4 "$INPUT_DIR"/*.mov; do
   name="${filename%.*}"
   tmp="${INPUT_DIR}/${name}.tmp.mp4"
   output="${INPUT_DIR}/${name}.mp4"
-  poster="${POSTER_DIR}/${name}.jpg"
+  poster="${POSTER_DIR}/${name}.webp"
 
   echo "Optimizing $filename → $(basename "$output")"
 
@@ -54,7 +57,9 @@ for file in "$INPUT_DIR"/*.mp4 "$INPUT_DIR"/*.mov; do
 
   echo "  Poster → posters/$(basename "$poster")"
   ffmpeg -y -i "$output" -vf "$SCALE_FILTER" \
-    -frames:v 1 -update 1 -q:v 4 "$poster"
+    -frames:v 1 -update 1 -f image2 -c:v png "${POSTER_DIR}/${name}.tmp.png"
+  cwebp -quiet -q 78 "${POSTER_DIR}/${name}.tmp.png" -o "$poster"
+  rm -f "${POSTER_DIR}/${name}.tmp.png"
 done
 
 echo "Done. Remember to update any .md asset paths if a .mov became .mp4."
diff --git a/docs/src/content/blog/ai-agents-ios-simulator/index.mdx b/docs/src/content/blog/ai-agents-ios-simulator/index.mdx
index c82ada8a..4e8ef617 100644
--- a/docs/src/content/blog/ai-agents-ios-simulator/index.mdx
+++ b/docs/src/content/blog/ai-agents-ios-simulator/index.mdx
@@ -28,7 +28,7 @@ I do not want an agent to guess whether those changes worked. I want it to open
   <video
     controls
     playsinline
-    poster="/features/posters/agentic-demo.jpg"
+    poster="/features/posters/agentic-demo.webp"
     class="w-full rounded-2xl"
   >
     <source src="/features/agentic-demo.mp4" type="video/mp4" />
diff --git a/docs/src/content/blog/debug-urlsession-requests-without-proxy/index.mdx b/docs/src/content/blog/debug-urlsession-requests-without-proxy/index.mdx
index cdb13e4a..1da88428 100644
--- a/docs/src/content/blog/debug-urlsession-requests-without-proxy/index.mdx
+++ b/docs/src/content/blog/debug-urlsession-requests-without-proxy/index.mdx
@@ -35,7 +35,7 @@ RocketSim takes a different route. With [RocketSim Connect](/docs/getting-starte
   <video
     controls
     playsinline
-    poster="/features/posters/network-monitoring-demo.jpg"
+    poster="/features/posters/network-monitoring-demo.webp"
     class="w-full rounded-2xl"
   >
     <source src="/features/network-monitoring-demo.mp4" type="video/mp4" />
diff --git a/docs/src/content/blog/ios-simulator-camera/index.mdx b/docs/src/content/blog/ios-simulator-camera/index.mdx
index 4c8f9278..a5390246 100644
--- a/docs/src/content/blog/ios-simulator-camera/index.mdx
+++ b/docs/src/content/blog/ios-simulator-camera/index.mdx
@@ -28,7 +28,7 @@ I have made this mistake myself while building camera-related flows: I postponed
   <video
     controls
     playsinline
-    poster="/features/posters/simulator-camera.jpg"
+    poster="/features/posters/simulator-camera.webp"
     class="w-full rounded-2xl"
   >
     <source src="/features/simulator-camera.mp4" type="video/mp4" />
diff --git a/docs/src/content/docs/docs/features/networking/network-speed-control.mdx b/docs/src/content/docs/docs/features/networking/network-speed-control.mdx
index ea9bbb3b..79e12798 100644
--- a/docs/src/content/docs/docs/features/networking/network-speed-control.mdx
+++ b/docs/src/content/docs/docs/features/networking/network-speed-control.mdx
@@ -1,8 +1,9 @@
 ---
-title: "Network Speed Control & Simulator Airplane Mode"
-description: "Throttle network speed on the iOS Simulator to test your app under 3G, Edge, or airplane mode conditions. Your Mac stays online while the Simulator is throttled."
+title: "Simulator Airplane Mode & Network Speed"
+description: "Turn on airplane mode in the iOS Simulator and throttle to 3G, Edge, or 100% packet loss. Your Mac stays online while only the Simulator loses connectivity."
 sidebar:
   order: 1
+  label: "Network Speed Control"
 ---
 
 It's essential to test your app in bad networking conditions during app development. Historically, you've had to test this on an actual device using Airplane mode or turn off your Mac's WiFi. Both are not ideal and often slow you down during development.
diff --git a/docs/src/content/docs/docs/features/physical-devices/index.mdx b/docs/src/content/docs/docs/features/physical-devices/index.mdx
index 9dd7f78a..efee065c 100644
--- a/docs/src/content/docs/docs/features/physical-devices/index.mdx
+++ b/docs/src/content/docs/docs/features/physical-devices/index.mdx
@@ -12,7 +12,7 @@ RocketSim brings its fastest testing workflows to a connected physical iPhone or
   muted
   playsinline
   preload="metadata"
-  poster="/features/posters/physical-device-testing.jpg"
+  poster="/features/posters/physical-device-testing.webp"
   aria-label="RocketSim simulating a location and opening a deep link on a connected physical iOS device"
 >
   <source src="/features/physical-device-testing.mp4" type="video/mp4" />
diff --git a/docs/src/layouts/components/Feature.astro b/docs/src/layouts/components/Feature.astro
index 93b86169..646339d4 100644
--- a/docs/src/layouts/components/Feature.astro
+++ b/docs/src/layouts/components/Feature.astro
@@ -14,12 +14,12 @@ const parsedCaption = asset.caption
   ? marked.parseInline(asset.caption)
   : undefined;
 
-// Posters live alongside the videos in `/features/posters/<name>.jpg` and are
+// Posters live alongside the videos in `/features/posters/<name>.webp` and are
 // generated by `public/features/reencode-all.sh`. They give the video area
 // instant visual content while the actual video bytes stay deferred.
 const posterPath =
   asset.type === "video"
-    ? asset.path.replace(/\/([^/]+)\.[^/.]+$/, "/posters/$1.jpg")
+    ? asset.path.replace(/\/([^/]+)\.[^/.]+$/, "/posters/$1.webp")
     : undefined;
 
 const blogPath = blogSlug
diff --git a/docs/tests/build-output.test.js b/docs/tests/build-output.test.js
new file mode 100644
index 00000000..dcb731b5
--- /dev/null
+++ b/docs/tests/build-output.test.js
@@ -0,0 +1,68 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync, readdirSync, statSync } from "node:fs";
+import { join } from "node:path";
+
+const DIST = new URL("../dist/", import.meta.url).pathname;
+
+export function readDist(relativePath) {
+  return readFileSync(join(DIST, relativePath), "utf8");
+}
+
+test("feature posters ship as webp, not jpeg", () => {
+  const posters = readdirSync(join(DIST, "features/posters"));
+  const jpegs = posters.filter((f) => f.endsWith(".jpg"));
+  assert.deepEqual(jpegs, [], `expected no .jpg posters, found: ${jpegs}`);
+});
+
+test("poster payload shrank against the jpeg baseline", () => {
+  const dir = join(DIST, "features/posters");
+  const total = readdirSync(dir).reduce(
+    (sum, f) => sum + statSync(join(dir, f)).size,
+    0,
+  );
+  // Byte-sum of the 13 jpg posters, measured 2026-07-25. Threshold is 0.75,
+  // not 0.55: the converted set saves ~51%, but the directory also keeps the
+  // pre-existing physical-device-location-system-behaviors.webp (105 KB,
+  // no jpg twin), which this change does not touch.
+  const BASELINE_BYTES = 856528;
+  assert.ok(
+    total <= BASELINE_BYTES * 0.75,
+    `poster payload ${Math.round(total / 1024)}KB exceeds 75% of baseline`,
+  );
+});
+
+test("no rendered page references a .jpg poster", () => {
+  const html = readDist("index.html");
+  assert.equal(
+    /posters\/[^"']*\.jpg/.test(html),
+    false,
+    "homepage still references a .jpg poster",
+  );
+});
+
+test("homepage videos stay deferred", () => {
+  const html = readDist("index.html");
+  const videoCount = (html.match(/<video/g) || []).length;
+  const preloadNone = (html.match(/preload="none"/g) || []).length;
+  assert.equal(
+    preloadNone,
+    videoCount,
+    "every homepage video must keep preload=none",
+  );
+});
+
+test("airplane-mode doc leads its title with the searched phrase", () => {
+  const html = readDist(
+    "docs/features/networking/network-speed-control/index.html",
+  );
+  const titleMatch = html.match(/<title>([^<]*)<\/title>/);
+  assert.ok(titleMatch, "no <title> tag found in the built page");
+  const title = titleMatch[1];
+  assert.match(
+    title,
+    /^Simulator Airplane Mode/,
+    `title should lead with the query phrase, got: ${title}`,
+  );
+  assert.ok(title.length <= 60, `title is ${title.length} chars, max 60`);
+});