diff --git a/src/deepscientist/daemon/api/handlers.py b/src/deepscientist/daemon/api/handlers.py
index 197e24f0..8d1637bd 100644
--- a/src/deepscientist/daemon/api/handlers.py
+++ b/src/deepscientist/daemon/api/handlers.py
@@ -2533,6 +2533,17 @@ def config_show(self, name: str) -> dict:
         }
 
     def config_save(self, name: str, body: dict) -> dict:
+        if name == "config" and isinstance(body.get("structured"), dict):
+            default_runner = self.app.config_manager._normalize_runtime_runner_name(
+                body["structured"].get("default_runner")
+            )
+            if default_runner in {"codex", "claude", "kimi", "opencode"}:
+                os.environ["DEEPSCIENTIST_DEFAULT_RUNNER"] = default_runner
+                os.environ["DEEPSCIENTIST_ENABLE_RUNNER"] = default_runner
+                os.environ.pop("DS_DEFAULT_RUNNER", None)
+                os.environ.pop("DS_ENABLE_RUNNER", None)
+                os.environ.pop("DEEPSCIENTIST_ENABLE_RUNNERS", None)
+                os.environ.pop("DS_ENABLE_RUNNERS", None)
         if isinstance(body.get("structured"), dict):
             result = self.app.config_manager.save_named_payload(name, body["structured"])
         else:
diff --git a/src/ui/src/components/landing/Hero.tsx b/src/ui/src/components/landing/Hero.tsx
index 80d0b51b..658fbab2 100644
--- a/src/ui/src/components/landing/Hero.tsx
+++ b/src/ui/src/components/landing/Hero.tsx
@@ -602,7 +602,7 @@ export default function Hero(props: {
                           className="h-12 rounded-full bg-[#C7AD96] px-7 text-[#2D2A26] shadow-[0_12px_28px_-14px_rgba(45,42,38,0.55)] transition-all duration-200 hover:-translate-y-0.5 hover:bg-[#D7C6AE]"
                           onClick={() => {
                             window.setTimeout(() => {
-                              setActiveDialog('autonomous')
+                              setActiveDialog('launch')
                             }, 120)
                           }}
                           data-onboarding-id="landing-start-research"
diff --git a/src/ui/src/components/landing/HeroNav.tsx b/src/ui/src/components/landing/HeroNav.tsx
index 8bf4d419..9c4cb44a 100644
--- a/src/ui/src/components/landing/HeroNav.tsx
+++ b/src/ui/src/components/landing/HeroNav.tsx
@@ -25,7 +25,7 @@ export default function HeroNav(props: {
         'supports-[backdrop-filter]:bg-white/40'
       )}
     >
-      <div className="mx-auto flex min-h-16 w-full max-w-[90vw] items-center justify-between gap-4 px-6">
+      <div className="mx-auto flex min-h-16 w-full max-w-[min(1180px,100vw)] items-center justify-between gap-2 px-3 sm:max-w-[90vw] sm:gap-4 sm:px-6">
         <Link
           href="/"
           className="flex items-center gap-2 rounded-full px-2 py-1 transition-colors hover:bg-black/[0.03]"
@@ -41,22 +41,23 @@ export default function HeroNav(props: {
             decoding="async"
             draggable={false}
           />
-          <span className="text-sm font-semibold tracking-tight text-[#2D2A26]">
+          <span className="hidden text-sm font-semibold tracking-tight text-[#2D2A26] sm:inline">
             DeepScientist
           </span>
         </Link>
 
-        <div className="flex items-center gap-2">
+        <div className="flex min-w-0 items-center gap-1.5 sm:gap-2">
           <SystemUpdateButton />
           <LocalAuthTokenButton />
           <Button
             variant="outline"
             size="sm"
-            className="h-9 rounded-full border-black/10 bg-white/60 text-[#2D2A26] hover:bg-white/90"
+            className="h-9 w-9 rounded-full border-black/10 bg-white/60 px-0 text-[#2D2A26] hover:bg-white/90 sm:w-auto sm:px-3"
             onClick={toggleLocale}
+            aria-label={locale === 'zh' ? 'Switch to English' : '切换到中文'}
           >
-            <Languages className="mr-2 h-4 w-4" />
-            {locale === 'zh' ? 'English' : '中文'}
+            <Languages className="h-4 w-4 sm:mr-2" />
+            <span className="hidden sm:inline">{locale === 'zh' ? 'English' : '中文'}</span>
           </Button>
           <Button
             variant="outline"
@@ -74,12 +75,12 @@ export default function HeroNav(props: {
           <Button
             variant="outline"
             size="sm"
-            className="h-9 rounded-full border-black/10 bg-white/60 text-[#2D2A26] hover:bg-white/90"
+            className="h-9 w-9 rounded-full border-black/10 bg-white/60 px-0 text-[#2D2A26] hover:bg-white/90 sm:w-auto sm:px-3"
             asChild
           >
-            <Link href="/docs">
-              <BookOpen className="mr-2 h-4 w-4" />
-              {t('navDocs')}
+            <Link href="/docs" aria-label={t('navDocs')}>
+              <BookOpen className="h-4 w-4 sm:mr-2" />
+              <span className="hidden sm:inline">{t('navDocs')}</span>
             </Link>
           </Button>
           {props.onOpenBenchStore ? (
@@ -95,12 +96,12 @@ export default function HeroNav(props: {
           ) : null}
           <Button
             size="sm"
-            className="h-9 rounded-full bg-[#C7AD96] text-[#2D2A26] hover:bg-[#D7C6AE]"
+            className="h-9 w-9 rounded-full bg-[#C7AD96] px-0 text-[#2D2A26] hover:bg-[#D7C6AE] sm:w-auto sm:px-3"
             asChild
           >
-            <Link href="/settings">
-              <Settings2 className="mr-2 h-4 w-4" />
-              {t('navSettings')}
+            <Link href="/settings" aria-label={t('navSettings')}>
+              <Settings2 className="h-4 w-4 sm:mr-2" />
+              <span className="hidden sm:inline">{t('navSettings')}</span>
             </Link>
           </Button>
         </div>
diff --git a/src/ui/src/components/onboarding/OnboardingOverlay.tsx b/src/ui/src/components/onboarding/OnboardingOverlay.tsx
index 9292601a..115f7833 100644
--- a/src/ui/src/components/onboarding/OnboardingOverlay.tsx
+++ b/src/ui/src/components/onboarding/OnboardingOverlay.tsx
@@ -651,6 +651,25 @@ function queryTarget(id?: string | null) {
   return document.querySelector<HTMLElement>(`[data-onboarding-id="${id}"]`)
 }
 
+function waitForTarget(id: string, timeoutMs = 2400) {
+  const startedAt = Date.now()
+  return new Promise<HTMLElement | null>((resolve) => {
+    const tick = () => {
+      const target = queryTarget(id)
+      if (target) {
+        resolve(target)
+        return
+      }
+      if (Date.now() - startedAt >= timeoutMs) {
+        resolve(null)
+        return
+      }
+      window.setTimeout(tick, 80)
+    }
+    tick()
+  })
+}
+
 function stepNeedsCopilotPanel(step: OnboardingStep | null) {
   if (!step) return false
   const ids = [step.targetId, step.actionTargetId, step.waitForElementId].filter(Boolean)
@@ -724,9 +743,15 @@ function scrollTargetIntoViewVerticalOnly(target: HTMLElement) {
 function triggerTargetAction(id?: string | null) {
   const target = queryTarget(id)
   if (!target) return false
+  const clickableTarget =
+    target instanceof HTMLElement &&
+    !target.matches('button, a, [role="button"], input, select, textarea')
+      ? target.querySelector<HTMLElement>('button, a, [role="button"], input, select, textarea')
+      : null
+  const actionTarget = clickableTarget || target
   const isFileTreeNode = Boolean(target.closest('[data-node-id]'))
   if (isFileTreeNode) {
-    target.dispatchEvent(
+    actionTarget.dispatchEvent(
       new MouseEvent('click', {
         bubbles: true,
         cancelable: true,
@@ -734,7 +759,7 @@ function triggerTargetAction(id?: string | null) {
         detail: 1,
       })
     )
-    target.dispatchEvent(
+    actionTarget.dispatchEvent(
       new MouseEvent('click', {
         bubbles: true,
         cancelable: true,
@@ -742,7 +767,7 @@ function triggerTargetAction(id?: string | null) {
         detail: 2,
       })
     )
-    target.dispatchEvent(
+    actionTarget.dispatchEvent(
       new MouseEvent('dblclick', {
         bubbles: true,
         cancelable: true,
@@ -752,11 +777,11 @@ function triggerTargetAction(id?: string | null) {
     )
     return true
   }
-  if (typeof target.click === 'function') {
-    target.click()
+  if (typeof actionTarget.click === 'function') {
+    actionTarget.click()
     return true
   }
-  target.dispatchEvent(
+  actionTarget.dispatchEvent(
     new MouseEvent('click', {
       bubbles: true,
       cancelable: true,
@@ -784,6 +809,51 @@ function clamp(value: number, min: number, max: number) {
   return Math.min(Math.max(value, min), max)
 }
 
+function cardTargetOverlap(args: {
+  top: number
+  left: number
+  cardWidth: number
+  cardHeight: number
+  targetRect: DOMRect
+}) {
+  const right = args.left + args.cardWidth
+  const bottom = args.top + args.cardHeight
+  const overlapWidth = Math.max(0, Math.min(right, args.targetRect.right) - Math.max(args.left, args.targetRect.left))
+  const overlapHeight = Math.max(0, Math.min(bottom, args.targetRect.bottom) - Math.max(args.top, args.targetRect.top))
+  return overlapWidth * overlapHeight
+}
+
+function bestFallbackCardPosition(args: {
+  targetRect: DOMRect
+  cardWidth: number
+  cardHeight: number
+  margin: number
+  viewportWidth: number
+  viewportHeight: number
+}) {
+  const maxTop = Math.max(args.margin, args.viewportHeight - args.margin - args.cardHeight)
+  const maxLeft = Math.max(args.margin, args.viewportWidth - args.margin - args.cardWidth)
+  const candidates = [
+    { top: args.margin, left: args.margin },
+    { top: args.margin, left: maxLeft },
+    { top: maxTop, left: args.margin },
+    { top: maxTop, left: maxLeft },
+  ]
+
+  return candidates
+    .map((candidate, index) => ({
+      ...candidate,
+      index,
+      overlap: cardTargetOverlap({
+        ...candidate,
+        cardWidth: args.cardWidth,
+        cardHeight: args.cardHeight,
+        targetRect: args.targetRect,
+      }),
+    }))
+    .sort((a, b) => a.overlap - b.overlap || b.index - a.index)[0]
+}
+
 function resolveCardPosition(args: {
   targetRect: DOMRect | null
   cardWidth: number
@@ -809,12 +879,29 @@ function resolveCardPosition(args: {
   const canPlaceLeft = rect.left - gap - args.cardWidth >= margin
 
   let placement = args.placement || 'auto'
+  if (
+    (placement === 'bottom' && !canPlaceBottom) ||
+    (placement === 'top' && !canPlaceTop) ||
+    (placement === 'right' && !canPlaceRight) ||
+    (placement === 'left' && !canPlaceLeft)
+  ) {
+    placement = 'auto'
+  }
   if (placement === 'auto') {
     if (canPlaceBottom) placement = 'bottom'
     else if (canPlaceTop) placement = 'top'
     else if (canPlaceRight) placement = 'right'
     else if (canPlaceLeft) placement = 'left'
-    else placement = 'bottom'
+    else {
+      return bestFallbackCardPosition({
+        targetRect: rect,
+        cardWidth: args.cardWidth,
+        cardHeight: args.cardHeight,
+        margin,
+        viewportWidth,
+        viewportHeight,
+      })
+    }
   }
 
   let top = rect.bottom + gap
@@ -921,6 +1008,7 @@ export function OnboardingOverlay() {
     neverShowAgain,
     close,
     completeTutorial,
+    goToStep,
   } = useOnboardingStore((state) => ({
     hydrated: state.hydrated,
     status: state.status,
@@ -935,6 +1023,7 @@ export function OnboardingOverlay() {
     neverShowAgain: state.neverShowAgain,
     close: state.close,
     completeTutorial: state.completeTutorial,
+    goToStep: state.goToStep,
   }))
 
   const [targetRect, setTargetRect] = React.useState<DOMRect | null>(null)
@@ -990,6 +1079,40 @@ export function OnboardingOverlay() {
     advance()
   }, [advance, navigate, status, step])
 
+  const restoreBenchstoreStartStep = React.useCallback(async () => {
+    triggerTargetAction('experiment-launch-close')
+    if (!queryTarget('benchstore-dialog')) {
+      triggerTargetAction('landing-benchstore')
+      await waitForTarget('benchstore-dialog')
+    }
+    if (!queryTarget('benchstore-detail-action-strip')) {
+      const featuredCard = await waitForTarget('benchstore-featured-card')
+      if (featuredCard) {
+        triggerTargetAction('benchstore-featured-card')
+        await waitForTarget('benchstore-detail-action-strip')
+      }
+    }
+    goToStep(7)
+  }, [goToStep])
+
+  const handlePrevious = React.useCallback(() => {
+    if (step?.id === 'benchstore-overview') {
+      triggerTargetAction('benchstore-close')
+      goToStep(2)
+      return
+    }
+    if (step?.id === 'landing-open-dialog') {
+      void restoreBenchstoreStartStep()
+      return
+    }
+    if (step?.id === 'launch-mode-overview') {
+      triggerTargetAction('experiment-launch-close')
+      goToStep(8)
+      return
+    }
+    previousStep()
+  }, [goToStep, previousStep, restoreBenchstoreStartStep, step?.id])
+
   React.useEffect(() => {
     hydrate()
   }, [hydrate])
@@ -1331,14 +1454,15 @@ export function OnboardingOverlay() {
 
       <div
         ref={cardRef}
-        className="pointer-events-auto fixed w-[min(466px,calc(100vw-32px))] overflow-hidden rounded-[30px] border border-[rgba(255,255,255,0.28)] bg-[linear-gradient(180deg,rgba(255,252,248,0.98),rgba(246,239,231,0.95))] p-5 shadow-[0_32px_110px_-44px_rgba(15,23,42,0.62)] backdrop-blur-xl"
+        className="pointer-events-auto fixed flex max-h-[calc(100vh-32px)] w-[min(466px,calc(100vw-32px))] flex-col overflow-hidden rounded-[30px] border border-[rgba(255,255,255,0.28)] bg-[linear-gradient(180deg,rgba(255,252,248,0.98),rgba(246,239,231,0.95))] p-5 shadow-[0_32px_110px_-44px_rgba(15,23,42,0.62)] backdrop-blur-xl"
         style={{
           top: cardPosition.top,
           left: cardPosition.left,
         }}
       >
         <div className="absolute inset-x-0 top-0 h-px bg-[linear-gradient(90deg,transparent,rgba(160,133,103,0.4),transparent)]" />
-        <div className="flex items-start gap-3">
+        <div className="min-h-0 flex-1 overflow-y-auto pr-1">
+          <div className="flex items-start gap-3">
           <div className="flex h-10 w-10 shrink-0 items-center justify-center rounded-full bg-[rgba(199,173,150,0.22)] text-[rgba(92,78,58,0.95)]">
             {step.route === 'landing' ? <Compass className="h-5 w-5" /> : <Sparkles className="h-5 w-5" />}
           </div>
@@ -1397,18 +1521,19 @@ export function OnboardingOverlay() {
               </div>
             ) : null}
           </div>
+          </div>
         </div>
 
-        <div className={cn('mt-6 flex gap-2', stepIndex === 0 ? 'justify-end' : 'justify-between')}>
+        <div className={cn('mt-6 flex shrink-0 flex-wrap gap-2', stepIndex === 0 ? 'justify-end' : 'justify-between')}>
           {stepIndex > 0 ? (
-            <Button variant="ghost" onClick={previousStep}>
+            <Button variant="ghost" onClick={handlePrevious}>
               <ChevronLeft className="mr-1 h-4 w-4" />
               {copy.back}
             </Button>
           ) : (
             <span />
           )}
-          <div className="flex items-center gap-2">
+          <div className="flex flex-wrap items-center justify-end gap-2">
             <Button variant="secondary" onClick={() => exitTutorial('close')}>
               <BookOpen className="mr-2 h-4 w-4" />
               {copy.skip}
diff --git a/src/ui/src/components/projects/ExperimentLaunchModeDialog.tsx b/src/ui/src/components/projects/ExperimentLaunchModeDialog.tsx
index ae9fe1f6..6b4130fb 100644
--- a/src/ui/src/components/projects/ExperimentLaunchModeDialog.tsx
+++ b/src/ui/src/components/projects/ExperimentLaunchModeDialog.tsx
@@ -132,6 +132,7 @@ export function ExperimentLaunchModeDialog({
       description={t.body}
       onClose={onClose}
       dataOnboardingId="experiment-launch-dialog"
+      closeButtonDataOnboardingId="experiment-launch-close"
       className={cn(LAUNCH_DIALOG_SHELL_CLASS, 'h-auto lg:max-h-[78svh]')}
     >
       <div className="feed-scrollbar h-full min-h-0 overflow-y-auto p-4 sm:p-6 lg:p-7">
diff --git a/src/ui/src/components/settings/SettingsPage.tsx b/src/ui/src/components/settings/SettingsPage.tsx
index f165397c..a87e6740 100644
--- a/src/ui/src/components/settings/SettingsPage.tsx
+++ b/src/ui/src/components/settings/SettingsPage.tsx
@@ -975,11 +975,11 @@ export function SettingsPage({
       <main className="mx-auto mt-5 min-h-0 w-full flex-1 overflow-hidden">
         <div
           className={cn(
-            'mx-auto grid h-full min-h-0 w-full max-w-[90vw] grid-rows-[auto_minmax(0,1fr)] gap-0 xl:grid-rows-1',
+            'mx-auto grid h-full min-h-0 w-full max-w-[90vw] grid-rows-[auto_minmax(0,1fr)] gap-4 xl:grid-rows-1 xl:gap-0',
             dockOpen ? 'xl:grid-cols-[260px_minmax(0,1fr)_420px]' : 'xl:grid-cols-[260px_minmax(0,1fr)]'
           )}
         >
-          <aside className="feed-scrollbar flex min-h-0 flex-col overflow-auto border-b border-black/[0.08] pb-6 xl:border-b-0 xl:border-r xl:pb-0 xl:pr-6 dark:border-white/[0.08]">
+          <aside className="feed-scrollbar flex max-h-[34vh] min-h-0 flex-col overflow-auto border-b border-black/[0.08] pb-4 xl:max-h-none xl:border-b-0 xl:border-r xl:pb-0 xl:pr-6 dark:border-white/[0.08]">
             <div className="text-sm font-medium">{t.title}</div>
 
             <div className="relative mt-4">
@@ -1142,7 +1142,7 @@ export function SettingsPage({
             </div>
           </aside>
 
-          <section ref={contentRef} className="feed-scrollbar min-h-0 overflow-y-auto py-6 xl:px-8">
+          <section ref={contentRef} className="feed-scrollbar min-h-0 overflow-y-auto py-4 xl:px-8 xl:py-6">
             <div className={cn('mx-auto w-full', dockOpen ? 'max-w-[1010px]' : 'max-w-[1180px]')}>
               {isPageLoading ? (
                 <div className="flex items-center gap-3 text-sm text-muted-foreground">
diff --git a/src/ui/src/components/ui/hint-dot.tsx b/src/ui/src/components/ui/hint-dot.tsx
index 556f4568..bfa68283 100644
--- a/src/ui/src/components/ui/hint-dot.tsx
+++ b/src/ui/src/components/ui/hint-dot.tsx
@@ -1,5 +1,15 @@
+import * as React from 'react'
+
 import { cn } from '@/lib/utils'
 
+const TOOLTIP_WIDTH = 224
+const TOOLTIP_GAP = 8
+const VIEWPORT_PADDING = 12
+
+function clamp(value: number, min: number, max: number) {
+  return Math.min(Math.max(value, min), max)
+}
+
 export function HintDot({
   label,
   className,
@@ -7,16 +17,62 @@ export function HintDot({
   label: string
   className?: string
 }) {
+  const triggerRef = React.useRef<HTMLSpanElement | null>(null)
+  const [tooltipStyle, setTooltipStyle] = React.useState<React.CSSProperties>({
+    left: VIEWPORT_PADDING,
+    top: VIEWPORT_PADDING,
+    width: TOOLTIP_WIDTH,
+  })
+
+  const updateTooltipPosition = React.useCallback(() => {
+    if (typeof window === 'undefined') return
+    const trigger = triggerRef.current
+    if (!trigger) return
+    const rect = trigger.getBoundingClientRect()
+    const width = Math.min(TOOLTIP_WIDTH, Math.max(160, window.innerWidth - VIEWPORT_PADDING * 2))
+    const left = clamp(
+      rect.left + rect.width / 2 - width / 2,
+      VIEWPORT_PADDING,
+      window.innerWidth - width - VIEWPORT_PADDING
+    )
+    const bottomTop = rect.bottom + TOOLTIP_GAP
+    const top =
+      bottomTop + 96 > window.innerHeight - VIEWPORT_PADDING && rect.top > 112
+        ? rect.top - TOOLTIP_GAP
+        : bottomTop
+    setTooltipStyle({
+      left,
+      top,
+      width,
+      transform: top === bottomTop ? undefined : 'translateY(-100%)',
+    })
+  }, [])
+
+  React.useEffect(() => {
+    window.addEventListener('resize', updateTooltipPosition)
+    window.addEventListener('scroll', updateTooltipPosition, true)
+    return () => {
+      window.removeEventListener('resize', updateTooltipPosition)
+      window.removeEventListener('scroll', updateTooltipPosition, true)
+    }
+  }, [updateTooltipPosition])
+
   return (
     <span className={cn('group relative inline-flex', className)}>
       <span
+        ref={triggerRef}
         tabIndex={0}
         aria-label={label}
+        onFocus={updateTooltipPosition}
+        onMouseEnter={updateTooltipPosition}
         className="inline-flex h-4 w-4 cursor-help items-center justify-center rounded-full border border-black/[0.10] text-[10px] font-medium leading-none text-muted-foreground outline-none transition hover:border-black/[0.16] hover:text-foreground focus:border-black/[0.16] focus:text-foreground dark:border-white/[0.12] dark:hover:border-white/[0.18] dark:hover:text-white dark:focus:border-white/[0.18] dark:focus:text-white"
       >
         ?
       </span>
-      <span className="pointer-events-none invisible absolute left-1/2 top-[calc(100%+0.5rem)] z-50 w-56 -translate-x-1/2 rounded-[18px] border border-black/[0.08] bg-[rgba(255,255,255,0.96)] px-3 py-2 text-[11px] font-normal leading-5 text-foreground opacity-0 shadow-[0_20px_40px_-28px_rgba(17,24,39,0.35)] transition group-hover:visible group-hover:opacity-100 group-focus-within:visible group-focus-within:opacity-100 dark:border-white/[0.10] dark:bg-[rgba(24,27,32,0.96)] dark:text-white/88">
+      <span
+        style={tooltipStyle}
+        className="pointer-events-none invisible fixed z-50 rounded-[18px] border border-black/[0.08] bg-[rgba(255,255,255,0.96)] px-3 py-2 text-[11px] font-normal leading-5 text-foreground opacity-0 shadow-[0_20px_40px_-28px_rgba(17,24,39,0.35)] transition group-hover:visible group-hover:opacity-100 group-focus-within:visible group-focus-within:opacity-100 dark:border-white/[0.10] dark:bg-[rgba(24,27,32,0.96)] dark:text-white/88"
+      >
         {label}
       </span>
     </span>
diff --git a/src/ui/src/lib/stores/onboarding.ts b/src/ui/src/lib/stores/onboarding.ts
index 9a84ff60..06e26034 100644
--- a/src/ui/src/lib/stores/onboarding.ts
+++ b/src/ui/src/lib/stores/onboarding.ts
@@ -21,6 +21,7 @@ type OnboardingState = OnboardingPersistence & {
   openChooser: (origin?: 'auto' | 'manual') => void
   startTutorial: (language: OnboardingLanguage, pathname: string, origin?: 'auto' | 'manual') => void
   restartTutorial: (pathname: string, language?: OnboardingLanguage | null) => void
+  goToStep: (stepIndex: number) => void
   nextStep: () => void
   previousStep: () => void
   close: () => void
@@ -165,6 +166,12 @@ export const useOnboardingStore = create<OnboardingState>((set, get) => ({
     })
   },
 
+  goToStep: (stepIndex) => {
+    set({
+      stepIndex: Math.max(0, stepIndex),
+    })
+  },
+
   nextStep: () => {
     set((state) => ({
       stepIndex: state.stepIndex + 1,