diff --git a/.trellis/spec/frontend/components.md b/.trellis/spec/frontend/components.md
index f36fe27..09f5629 100644
--- a/.trellis/spec/frontend/components.md
+++ b/.trellis/spec/frontend/components.md
@@ -117,6 +117,47 @@ import { Table } from "@/components/ui/table";
 Visible form controls and data tables should use the Kumo-backed adapters. Native hidden
 inputs are acceptable only inside adapters when needed to preserve FormData semantics.
 
+### Select Adapter Positioning Contract
+
+`components/ui/select.tsx` is intentionally project-owned instead of directly wrapping
+`@cloudflare/kumo/components/select`. Kumo Select 2.6 can inherit Base UI
+`alignItemWithTrigger=true`, which may render `data-side="none"` and overlap the trigger in
+production.
+
+The project Select adapter must:
+
+- Preserve the local API: `options`, `value`, `defaultValue`, `name`, `placeholder`,
+  `disabled`, `required`, `aria-*`, and `onValueChange`.
+- Render a hidden form value only inside the adapter when `name` is provided.
+- Use portal/fixed positioning for the popup and keep a positive gap between trigger and
+  panel. Browser validation should assert `verticalOverlap === 0` on desktop and mobile.
+- Keep keyboard behavior for ArrowUp/ArrowDown, Home/End, Enter/Space, Escape, and Tab.
+
+```typescript
+// Good: feature code stays on the project adapter.
+<Select name="organizationId" options={organizationOptions} />
+
+// Avoid: this can reintroduce production overlay regressions.
+import { Select } from "@cloudflare/kumo/components/select";
+```
+
+### Dialog Adapter Centering Contract
+
+`components/ui/dialog.tsx` may use Kumo Dialog primitives for accessibility, but the
+project adapter owns panel geometry. Kumo Dialog includes fixed `left-1/2 top-1/2`
+and translate classes, and those transforms can interact with project animations or
+production CSS ordering.
+
+The project Dialog adapter must:
+
+- Center the panel without relying on translate transforms. Use `fixed inset-0 m-auto`
+  plus explicit width, max-height, and `h-fit`.
+- Override Kumo minimum width so mobile dialogs stay inside `100vw`.
+- Keep `transform: none` and `translate: 0 0` on `.teatea-dialog`; use
+  opacity/scale-only motion if animation is needed.
+- Browser validation should assert the panel center is within 2px of the viewport center
+  on desktop and mobile.
+
 ### Use Proper Elements
 
 ```typescript
diff --git a/app/(app)/app/template.tsx b/app/(app)/app/template.tsx
new file mode 100644
index 0000000..7267a42
--- /dev/null
+++ b/app/(app)/app/template.tsx
@@ -0,0 +1,7 @@
+type AppTemplateProps = {
+  children: React.ReactNode;
+};
+
+export default function AppTemplate({ children }: AppTemplateProps): React.ReactElement {
+  return <div className="route-transition min-h-full">{children}</div>;
+}
diff --git a/app/globals.css b/app/globals.css
index 2e5241a..895ae1b 100644
--- a/app/globals.css
+++ b/app/globals.css
@@ -101,6 +101,17 @@ a,
   }
 }
 
+@keyframes route-transition {
+  from {
+    opacity: 0;
+    transform: translateY(0.375rem);
+  }
+  to {
+    opacity: 1;
+    transform: translateY(0);
+  }
+}
+
 @keyframes loading-progress {
   0% {
     transform: translateX(-100%);
@@ -128,6 +139,10 @@ a,
   animation: page-enter 180ms ease-out both;
 }
 
+.route-transition {
+  animation: route-transition 180ms ease-out both;
+}
+
 .table-row-enter {
   animation: page-enter 160ms ease-out both;
 }
@@ -141,9 +156,15 @@ a,
 }
 
 .teatea-button {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 0.375rem;
   min-height: 2.5rem;
   border-radius: var(--radius-md);
   font-weight: 600;
+  line-height: 1.25;
+  white-space: nowrap;
   transition:
     background-color 140ms ease,
     border-color 140ms ease,
@@ -152,8 +173,13 @@ a,
     opacity 140ms ease;
 }
 
+.teatea-button :where(svg) {
+  flex-shrink: 0;
+}
+
 .teatea-button:focus-visible,
 .teatea-control:focus-visible,
+.teatea-select-trigger:focus-visible,
 :where([data-kumo-component="Select"][data-kumo-part="trigger"]):focus-visible {
   outline: none;
   box-shadow: 0 0 0 3px color-mix(in oklch, var(--ring) 24%, transparent);
@@ -198,6 +224,7 @@ a,
 }
 
 .teatea-control,
+.teatea-select-trigger,
 :where([data-kumo-component="Select"][data-kumo-part="trigger"]) {
   min-height: 2.5rem;
   width: 100%;
@@ -207,6 +234,7 @@ a,
   color: var(--foreground);
   font-size: 0.875rem;
   font-weight: 500;
+  line-height: 1.35;
   box-shadow: 0 1px 2px color-mix(in oklch, var(--foreground) 7%, transparent);
   transition:
     background-color 140ms ease,
@@ -218,7 +246,12 @@ a,
   padding: 0.5rem 0.75rem;
 }
 
+.teatea-select-trigger,
 :where([data-kumo-component="Select"][data-kumo-part="trigger"]) {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.5rem;
   appearance: none;
   outline: none;
   padding: 0.5rem 0.75rem;
@@ -226,27 +259,89 @@ a,
 }
 
 .teatea-control:hover,
+.teatea-select-trigger:hover,
 :where([data-kumo-component="Select"][data-kumo-part="trigger"]):hover {
   border-color: color-mix(in oklch, var(--primary) 45%, var(--input));
   background: color-mix(in oklch, var(--secondary) 34%, white);
 }
 
+.teatea-select-trigger[data-open="true"] {
+  border-color: color-mix(in oklch, var(--primary) 58%, var(--input));
+  background: var(--card);
+}
+
 .teatea-control::placeholder {
   color: var(--muted-foreground);
 }
 
 .teatea-control:disabled,
 .teatea-button:disabled,
+.teatea-select-trigger:disabled,
 :where([data-kumo-component="Select"][data-kumo-part="trigger"][data-disabled]) {
   cursor: not-allowed;
   opacity: 0.55;
 }
 
+.teatea-select-trigger :where(svg),
 .teatea-select :where(svg),
 :where([data-kumo-component="Select"][data-kumo-part="trigger"]) :where(svg) {
   color: var(--primary);
 }
 
+.teatea-select-panel {
+  position: fixed;
+  z-index: 60;
+  overflow-y: auto;
+  overscroll-behavior: contain;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-md);
+  background: var(--card);
+  color: var(--foreground);
+  padding: 0.375rem;
+  box-shadow:
+    0 18px 44px color-mix(in oklch, var(--foreground) 14%, transparent),
+    0 0 0 1px color-mix(in oklch, var(--primary) 10%, transparent);
+  animation: page-enter 120ms ease-out both;
+}
+
+.teatea-select-option {
+  display: flex;
+  min-height: 2.25rem;
+  width: 100%;
+  cursor: pointer;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.625rem;
+  border: 0;
+  border-radius: calc(var(--radius-md) - 2px);
+  background: transparent;
+  color: var(--foreground);
+  padding: 0.5rem 0.625rem;
+  text-align: left;
+  font-size: 0.875rem;
+  outline: none;
+}
+
+.teatea-select-option[data-highlighted="true"],
+.teatea-select-option:hover {
+  background: var(--secondary);
+  color: var(--secondary-foreground);
+}
+
+.teatea-select-option:focus-visible {
+  box-shadow: inset 0 0 0 2px color-mix(in oklch, var(--ring) 36%, transparent);
+}
+
+.teatea-select-option[data-selected="true"] {
+  color: var(--primary);
+  font-weight: 600;
+}
+
+.teatea-select-option:disabled {
+  cursor: not-allowed;
+  opacity: 0.5;
+}
+
 :where([role="listbox"]:has([data-kumo-component="Select"][data-kumo-part="option"])) {
   z-index: 60;
   outline: none;
@@ -332,6 +427,14 @@ a,
 }
 
 .teatea-dialog {
+  inset: 0 !important;
+  height: fit-content;
+  margin: auto !important;
+  max-width: calc(100vw - 1.5rem);
+  min-width: min(calc(100vw - 1.5rem), 48rem) !important;
+  transform: none !important;
+  translate: 0 0 !important;
+  width: min(calc(100vw - 1.5rem), 48rem) !important;
   border: 1px solid var(--border);
   border-radius: var(--radius-lg);
   background: var(--card);
@@ -348,8 +451,10 @@ a,
 
 @media (prefers-reduced-motion: reduce) {
   .page-enter,
+  .route-transition,
   .table-row-enter,
   .dialog-panel-enter,
+  .teatea-select-panel,
   .loading-progress {
     animation: none;
   }
diff --git a/components/ui/badge.tsx b/components/ui/badge.tsx
index 633db80..c4808ea 100644
--- a/components/ui/badge.tsx
+++ b/components/ui/badge.tsx
@@ -16,13 +16,34 @@ const variantMap: Record<LegacyBadgeVariant, KumoBadgeProps["variant"]> = {
   danger: "error",
 };
 
-export type BadgeProps = Omit<KumoBadgeProps, "variant" | "children"> & {
+export type BadgeProps = Omit<KumoBadgeProps, "variant"> & {
   variant?: LegacyBadgeVariant | KumoBadgeProps["variant"];
-  children?: React.ReactNode;
 };
 
-export function Badge({ className, variant = "default", ...props }: BadgeProps): React.ReactElement {
-  const mappedVariant = variant in variantMap ? variantMap[variant as LegacyBadgeVariant] : (variant as KumoBadgeProps["variant"]);
-
-  return <KumoBadge className={cn("teatea-badge", className)} variant={mappedVariant} {...(props as KumoBadgeProps)} />;
+function isLegacyBadgeVariant(variant: BadgeProps["variant"]): variant is LegacyBadgeVariant {
+  switch (variant) {
+    case "default":
+    case "secondary":
+    case "outline":
+    case "success":
+    case "warning":
+    case "danger":
+      return true;
+    default:
+      return false;
+  }
+}
+
+function mapBadgeVariant(variant: BadgeProps["variant"]): KumoBadgeProps["variant"] {
+  if (isLegacyBadgeVariant(variant)) {
+    return variantMap[variant];
+  }
+
+  return variant;
+}
+
+export function Badge({ className, variant = "default", ...props }: BadgeProps): React.ReactElement {
+  const mappedVariant = mapBadgeVariant(variant);
+
+  return <KumoBadge className={cn("teatea-badge", className)} variant={mappedVariant} {...props} />;
 }
diff --git a/components/ui/button.tsx b/components/ui/button.tsx
index 2291a03..61a97f9 100644
--- a/components/ui/button.tsx
+++ b/components/ui/button.tsx
@@ -26,11 +26,21 @@ const sizeMap: Record<ButtonSize, KumoButtonProps["size"]> = {
   icon: "base",
 };
 
-export type ButtonProps = Omit<KumoButtonProps, "variant" | "size" | "shape"> & {
+type BaseButtonProps = Omit<KumoButtonProps, "variant" | "size" | "shape"> & {
   variant?: ButtonVariant;
-  size?: ButtonSize;
 };
 
+type TextButtonProps = BaseButtonProps & {
+  size?: Exclude<ButtonSize, "icon">;
+};
+
+type IconButtonProps = BaseButtonProps & {
+  "aria-label": string;
+  size: "icon";
+};
+
+export type ButtonProps = TextButtonProps | IconButtonProps;
+
 export type LinkButtonProps = Omit<KumoLinkButtonProps, "variant" | "size"> & {
   variant?: ButtonVariant;
   size?: Exclude<ButtonSize, "icon">;
@@ -40,17 +50,34 @@ export const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(function
   { className, variant = "default", size = "default", ...props },
   ref,
 ): React.ReactElement {
-  const kumoProps = {
-    className: cn("teatea-button", `teatea-button-${variant}`, className),
-    ref,
-    shape: size === "icon" ? "square" : "base",
-    size: sizeMap[size],
-    variant: variantMap[variant],
-    ...props,
-  } as KumoButtonProps & React.RefAttributes<HTMLButtonElement>;
+  if (size === "icon") {
+    const iconAriaLabel = props["aria-label"];
+
+    if (!iconAriaLabel) {
+      throw new Error("Icon buttons require an aria-label.");
+    }
+
+    return (
+      <KumoButton
+        {...props}
+        ref={ref}
+        aria-label={iconAriaLabel}
+        className={cn("teatea-button", `teatea-button-${variant}`, className)}
+        shape="square"
+        size={sizeMap[size]}
+        variant={variantMap[variant]}
+      />
+    );
+  }
 
   return (
-    <KumoButton {...kumoProps} />
+    <KumoButton
+      ref={ref}
+      className={cn("teatea-button", `teatea-button-${variant}`, className)}
+      size={sizeMap[size]}
+      variant={variantMap[variant]}
+      {...props}
+    />
   );
 });
 
diff --git a/components/ui/dialog.tsx b/components/ui/dialog.tsx
index 45156c8..97b082b 100644
--- a/components/ui/dialog.tsx
+++ b/components/ui/dialog.tsx
@@ -40,7 +40,7 @@ export function Dialog({
     >
       <KumoDialog
         className={cn(
-          "teatea-dialog dialog-panel-enter fixed left-1/2 top-1/2 z-50 flex max-h-[min(92svh,52rem)] w-[min(calc(100vw-1.5rem),48rem)] -translate-x-1/2 -translate-y-1/2 flex-col overflow-hidden rounded-lg border border-kumo-line bg-kumo-base p-0 shadow-xl outline-none ring-1 ring-kumo-line",
+          "teatea-dialog fixed inset-0 z-50 m-auto flex h-fit max-h-[min(calc(100svh-1.5rem),52rem)] w-[min(calc(100vw-1.5rem),48rem)] min-w-0 flex-col overflow-hidden rounded-lg border border-kumo-line bg-kumo-base p-0 shadow-xl outline-none ring-1 ring-kumo-line",
           "data-ending-style:scale-95 data-ending-style:opacity-0 data-starting-style:scale-95 data-starting-style:opacity-0",
           className,
         )}
diff --git a/components/ui/select.tsx b/components/ui/select.tsx
index ff63d5d..14c381c 100644
--- a/components/ui/select.tsx
+++ b/components/ui/select.tsx
@@ -1,7 +1,8 @@
 "use client";
 
 import * as React from "react";
-import { Select as KumoSelect } from "@cloudflare/kumo/components/select";
+import { createPortal } from "react-dom";
+import { Check, ChevronDown } from "lucide-react";
 
 import { cn } from "@/lib/utils";
 
@@ -11,13 +12,25 @@ export type SelectOption = {
   disabled?: boolean;
 };
 
+type SelectPosition = {
+  left: number;
+  maxHeight: number;
+  top: number;
+  width: number;
+};
+
 type SelectProps = {
+  "aria-describedby"?: string;
   "aria-label"?: string;
+  "aria-labelledby"?: string;
   className?: string;
   defaultValue?: string;
   disabled?: boolean;
+  id?: string;
   label?: React.ReactNode;
   name?: string;
+  onBlur?: React.FocusEventHandler<HTMLButtonElement>;
+  onFocus?: React.FocusEventHandler<HTMLButtonElement>;
   onValueChange?: (value: string) => void;
   options: SelectOption[];
   placeholder?: string;
@@ -25,37 +38,414 @@ type SelectProps = {
   value?: string;
 };
 
+const SELECT_GAP = 6;
+const SELECT_MAX_HEIGHT = 288;
+const VIEWPORT_PADDING = 8;
+
+function getEnabledValues(options: SelectOption[]): string[] {
+  return options.filter((option) => option.disabled !== true).map((option) => option.value);
+}
+
+function getInitialValue(options: SelectOption[], defaultValue?: string, placeholder?: string): string {
+  if (defaultValue !== undefined) {
+    return defaultValue;
+  }
+
+  if (placeholder !== undefined) {
+    return "";
+  }
+
+  return getEnabledValues(options)[0] ?? "";
+}
+
+function getAdjacentValue(options: SelectOption[], currentValue: string, direction: 1 | -1): string {
+  const enabledValues = getEnabledValues(options);
+
+  if (enabledValues.length === 0) {
+    return currentValue;
+  }
+
+  const currentIndex = enabledValues.indexOf(currentValue);
+  const nextIndex =
+    currentIndex === -1
+      ? direction === 1
+        ? 0
+        : enabledValues.length - 1
+      : (currentIndex + direction + enabledValues.length) % enabledValues.length;
+
+  return enabledValues[nextIndex] ?? currentValue;
+}
+
+function getBoundaryValue(options: SelectOption[], boundary: "first" | "last", fallbackValue: string): string {
+  const enabledValues = getEnabledValues(options);
+
+  if (enabledValues.length === 0) {
+    return fallbackValue;
+  }
+
+  if (boundary === "first") {
+    return enabledValues[0] ?? fallbackValue;
+  }
+
+  return enabledValues[enabledValues.length - 1] ?? fallbackValue;
+}
+
+function findOption(options: SelectOption[], value: string): SelectOption | undefined {
+  return options.find((option) => option.value === value);
+}
+
 export function Select({
+  "aria-describedby": ariaDescribedBy,
+  "aria-label": ariaLabel,
+  "aria-labelledby": ariaLabelledBy,
   className,
+  defaultValue,
+  disabled = false,
+  id,
+  label,
+  name,
+  onBlur,
+  onFocus,
   onValueChange,
   options,
   placeholder,
+  required,
   value,
-  defaultValue,
-  ...props
 }: SelectProps): React.ReactElement {
+  const generatedId = React.useId().replace(/:/g, "");
+  const controlId = id ?? `teatea-select-${generatedId}`;
+  const labelId = label ? `${controlId}-label` : undefined;
+  const listboxId = `${controlId}-listbox`;
+  const triggerRef = React.useRef<HTMLButtonElement>(null);
+  const listboxRef = React.useRef<HTMLDivElement>(null);
+  const [portalRoot, setPortalRoot] = React.useState<HTMLElement | null>(null);
+  const [isOpen, setIsOpen] = React.useState(false);
+  const [position, setPosition] = React.useState<SelectPosition | null>(null);
+  const [uncontrolledValue, setUncontrolledValue] = React.useState(() =>
+    getInitialValue(options, defaultValue, placeholder),
+  );
+  const isControlled = value !== undefined;
+  const selectedValue = isControlled ? value : uncontrolledValue;
+  const selectedOption = findOption(options, selectedValue);
+  const [highlightedValue, setHighlightedValue] = React.useState(selectedValue);
+  const highlightedIndex = options.findIndex((option) => option.value === highlightedValue);
+  const activeDescendant =
+    isOpen && highlightedIndex >= 0 ? `${listboxId}-option-${highlightedIndex}` : undefined;
+
+  const updatePosition = React.useCallback(() => {
+    const trigger = triggerRef.current;
+
+    if (!trigger || typeof window === "undefined") {
+      return;
+    }
+
+    const rect = trigger.getBoundingClientRect();
+    const viewportWidth = window.innerWidth;
+    const viewportHeight = window.innerHeight;
+    const availableBelow = viewportHeight - rect.bottom - SELECT_GAP - VIEWPORT_PADDING;
+    const availableAbove = rect.top - SELECT_GAP - VIEWPORT_PADDING;
+    const estimatedHeight = Math.min(SELECT_MAX_HEIGHT, Math.max(120, options.length * 40 + 12));
+    const shouldOpenBelow = availableBelow >= estimatedHeight || availableBelow >= availableAbove;
+    const availableHeight = shouldOpenBelow ? availableBelow : availableAbove;
+    const maxHeight = Math.max(96, Math.min(SELECT_MAX_HEIGHT, availableHeight));
+    const left = Math.min(
+      Math.max(VIEWPORT_PADDING, rect.left),
+      Math.max(VIEWPORT_PADDING, viewportWidth - rect.width - VIEWPORT_PADDING),
+    );
+    const top = shouldOpenBelow
+      ? Math.min(rect.bottom + SELECT_GAP, viewportHeight - maxHeight - VIEWPORT_PADDING)
+      : Math.max(VIEWPORT_PADDING, rect.top - SELECT_GAP - maxHeight);
+
+    setPosition({
+      left,
+      maxHeight,
+      top,
+      width: rect.width,
+    });
+  }, [options.length]);
+
+  const openSelect = React.useCallback(() => {
+    if (disabled || options.length === 0) {
+      return;
+    }
+
+    const nextHighlightedValue =
+      findOption(options, selectedValue)?.disabled === true
+        ? getBoundaryValue(options, "first", selectedValue)
+        : selectedValue;
+
+    setHighlightedValue(nextHighlightedValue);
+    setIsOpen(true);
+  }, [disabled, options, selectedValue]);
+
+  const closeSelect = React.useCallback(() => {
+    setIsOpen(false);
+  }, []);
+
+  const commitValue = React.useCallback(
+    (nextValue: string) => {
+      const nextOption = findOption(options, nextValue);
+
+      if (!nextOption || nextOption.disabled === true) {
+        return;
+      }
+
+      if (!isControlled) {
+        setUncontrolledValue(nextValue);
+      }
+
+      if (nextValue !== selectedValue) {
+        onValueChange?.(nextValue);
+      }
+
+      setHighlightedValue(nextValue);
+      closeSelect();
+      triggerRef.current?.focus();
+    },
+    [closeSelect, isControlled, onValueChange, options, selectedValue],
+  );
+
+  React.useEffect(() => {
+    setPortalRoot(document.body);
+  }, []);
+
+  React.useEffect(() => {
+    if (isControlled) {
+      return;
+    }
+
+    if (findOption(options, uncontrolledValue)) {
+      return;
+    }
+
+    setUncontrolledValue(getInitialValue(options, defaultValue, placeholder));
+  }, [defaultValue, isControlled, options, placeholder, uncontrolledValue]);
+
+  React.useEffect(() => {
+    const trigger = triggerRef.current;
+    const form = trigger?.form;
+
+    if (!form || isControlled) {
+      return;
+    }
+
+    function handleReset(): void {
+      setUncontrolledValue(getInitialValue(options, defaultValue, placeholder));
+    }
+
+    form.addEventListener("reset", handleReset);
+
+    return () => {
+      form.removeEventListener("reset", handleReset);
+    };
+  }, [defaultValue, isControlled, options, placeholder]);
+
+  React.useLayoutEffect(() => {
+    if (!isOpen) {
+      return;
+    }
+
+    updatePosition();
+  }, [isOpen, updatePosition]);
+
+  React.useEffect(() => {
+    if (!isOpen) {
+      return;
+    }
+
+    function handlePointerDown(event: MouseEvent | TouchEvent): void {
+      const target = event.target;
+
+      if (!(target instanceof Node)) {
+        return;
+      }
+
+      if (triggerRef.current?.contains(target) || listboxRef.current?.contains(target)) {
+        return;
+      }
+
+      closeSelect();
+    }
+
+    document.addEventListener("mousedown", handlePointerDown);
+    document.addEventListener("touchstart", handlePointerDown);
+    window.addEventListener("resize", updatePosition);
+    window.addEventListener("scroll", updatePosition, true);
+
+    return () => {
+      document.removeEventListener("mousedown", handlePointerDown);
+      document.removeEventListener("touchstart", handlePointerDown);
+      window.removeEventListener("resize", updatePosition);
+      window.removeEventListener("scroll", updatePosition, true);
+    };
+  }, [closeSelect, isOpen, updatePosition]);
+
+  function handleTriggerClick(): void {
+    if (isOpen) {
+      closeSelect();
+      return;
+    }
+
+    openSelect();
+  }
+
+  function handleKeyDown(event: React.KeyboardEvent<HTMLButtonElement>): void {
+    switch (event.key) {
+      case "ArrowDown": {
+        event.preventDefault();
+        if (!isOpen) {
+          openSelect();
+          return;
+        }
+        setHighlightedValue((currentValue) => getAdjacentValue(options, currentValue, 1));
+        return;
+      }
+      case "ArrowUp": {
+        event.preventDefault();
+        if (!isOpen) {
+          openSelect();
+          return;
+        }
+        setHighlightedValue((currentValue) => getAdjacentValue(options, currentValue, -1));
+        return;
+      }
+      case "Home": {
+        if (!isOpen) {
+          return;
+        }
+        event.preventDefault();
+        setHighlightedValue((currentValue) => getBoundaryValue(options, "first", currentValue));
+        return;
+      }
+      case "End": {
+        if (!isOpen) {
+          return;
+        }
+        event.preventDefault();
+        setHighlightedValue((currentValue) => getBoundaryValue(options, "last", currentValue));
+        return;
+      }
+      case "Enter":
+      case " ": {
+        event.preventDefault();
+        if (!isOpen) {
+          openSelect();
+          return;
+        }
+        commitValue(highlightedValue);
+        return;
+      }
+      case "Escape": {
+        if (!isOpen) {
+          return;
+        }
+        event.preventDefault();
+        closeSelect();
+        return;
+      }
+      case "Tab": {
+        closeSelect();
+        return;
+      }
+      default:
+        return;
+    }
+  }
+
+  const field = (
+    <div className="grid gap-2">
+      {label ? (
+        <span id={labelId} className="text-sm font-medium text-foreground">
+          {label}
+        </span>
+      ) : null}
+      <button
+        ref={triggerRef}
+        aria-activedescendant={activeDescendant}
+        aria-controls={isOpen ? listboxId : undefined}
+        aria-describedby={ariaDescribedBy}
+        aria-expanded={isOpen}
+        aria-haspopup="listbox"
+        aria-label={labelId ? undefined : ariaLabel}
+        aria-labelledby={ariaLabelledBy ?? labelId}
+        aria-required={required}
+        className={cn("teatea-select-trigger", className)}
+        data-open={isOpen ? "true" : undefined}
+        disabled={disabled}
+        id={controlId}
+        onBlur={onBlur}
+        onClick={handleTriggerClick}
+        onFocus={onFocus}
+        onKeyDown={handleKeyDown}
+        role="combobox"
+        type="button"
+      >
+        <span className={cn("min-w-0 truncate", !selectedOption && "text-muted-foreground")}>
+          {selectedOption?.label ?? placeholder ?? ""}
+        </span>
+        <ChevronDown
+          aria-hidden="true"
+          className={cn("size-4 shrink-0 text-primary transition-transform", isOpen && "rotate-180")}
+        />
+      </button>
+      {name ? <input name={name} type="hidden" value={selectedValue} /> : null}
+    </div>
+  );
+
+  const popup =
+    portalRoot && isOpen && position
+      ? createPortal(
+          <div
+            ref={listboxRef}
+            aria-labelledby={ariaLabelledBy ?? labelId}
+            className="teatea-select-panel"
+            id={listboxId}
+            role="listbox"
+            style={{
+              left: position.left,
+              maxHeight: position.maxHeight,
+              top: position.top,
+              width: position.width,
+            }}
+          >
+            {options.map((option, index) => {
+              const isSelected = option.value === selectedValue;
+              const isHighlighted = option.value === highlightedValue;
+
+              return (
+                <button
+                  aria-disabled={option.disabled}
+                  aria-selected={isSelected}
+                  className="teatea-select-option"
+                  data-highlighted={isHighlighted ? "true" : undefined}
+                  data-selected={isSelected ? "true" : undefined}
+                  disabled={option.disabled}
+                  id={`${listboxId}-option-${index}`}
+                  key={option.value}
+                  onClick={() => commitValue(option.value)}
+                  onMouseDown={(event) => event.preventDefault()}
+                  onMouseEnter={() => {
+                    if (option.disabled !== true) {
+                      setHighlightedValue(option.value);
+                    }
+                  }}
+                  role="option"
+                  type="button"
+                >
+                  <span className="min-w-0 truncate">{option.label}</span>
+                  {isSelected ? <Check aria-hidden="true" className="size-4 shrink-0 text-primary" /> : null}
+                </button>
+              );
+            })}
+          </div>,
+          portalRoot,
+        )
+      : null;
+
   return (
-    <KumoSelect<string>
-      className={cn(
-        "teatea-select",
-        "min-h-10 w-full rounded-md border border-input bg-card px-3 py-2 text-left text-sm font-medium text-foreground shadow-sm",
-        "transition-colors hover:border-primary/45 hover:bg-secondary/35",
-        "focus-visible:border-primary focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring/25",
-        "disabled:cursor-not-allowed disabled:opacity-50",
-        "[&_[data-placeholder]]:text-muted-foreground [&_svg]:text-primary",
-        className,
-      )}
-      defaultValue={defaultValue}
-      onValueChange={(nextValue) => onValueChange?.(String(nextValue))}
-      placeholder={placeholder}
-      value={value}
-      {...props}
-    >
-      {options.map((option) => (
-        <KumoSelect.Option key={option.value} disabled={option.disabled} value={option.value}>
-          {option.label}
-        </KumoSelect.Option>
-      ))}
-    </KumoSelect>
+    <>
+      {field}
+      {popup}
+    </>
   );
 }
diff --git a/modules/auth/components/AuthPanel.tsx b/modules/auth/components/AuthPanel.tsx
index df5c834..eb352c1 100644
--- a/modules/auth/components/AuthPanel.tsx
+++ b/modules/auth/components/AuthPanel.tsx
@@ -25,6 +25,26 @@ const modeCopy: Record<AuthMode, { title: string; badge: string; submit: string
   setup: { title: "初始化机构", badge: "First run", submit: "完成初始化" },
 };
 
+async function readApiResult<T extends Record<string, unknown>>(response: Response): Promise<ApiResult<T>> {
+  const text = await response.text();
+
+  if (!text) {
+    return {
+      success: false,
+      reason: response.ok ? "服务器返回了空响应" : `请求失败：${response.status}`,
+    };
+  }
+
+  try {
+    return JSON.parse(text) as ApiResult<T>;
+  } catch {
+    return {
+      success: false,
+      reason: response.ok ? "服务器返回了无法解析的数据" : `请求失败：${response.status}`,
+    };
+  }
+}
+
 function AuthPanelContent({ mode }: AuthPanelProps): React.ReactElement {
   const router = useRouter();
   const searchParams = useSearchParams();
@@ -48,11 +68,14 @@ function AuthPanelContent({ mode }: AuthPanelProps): React.ReactElement {
         fetch("/api/auth/session"),
         fetch("/api/organizations"),
       ]);
-      const bootstrap = (await bootstrapResponse.json()) as ApiResult<{ setupRequired: boolean }>;
-      const session = (await sessionResponse.json()) as ApiResult<{ account: unknown | null }>;
-      const organizationsResult = (await organizationsResponse.json()) as ApiResult<{ organizations: Organization[] }>;
+      const bootstrap = await readApiResult<{ setupRequired: boolean }>(bootstrapResponse);
+      const session = await readApiResult<{ account: unknown | null }>(sessionResponse);
+      const organizationsResult = await readApiResult<{ organizations: Organization[] }>(organizationsResponse);
 
       if (!isMounted || !bootstrap.success || !session.success) {
+        if (isMounted) {
+          setMessage(!bootstrap.success ? bootstrap.reason : session.reason);
+        }
         return;
       }
 
@@ -122,7 +145,7 @@ function AuthPanelContent({ mode }: AuthPanelProps): React.ReactElement {
         invitationToken,
       }),
     });
-    const result = (await response.json()) as ApiResult<{ account: unknown; pendingApproval?: boolean }>;
+    const result = await readApiResult<{ account: unknown; pendingApproval?: boolean }>(response);
     setIsPending(false);
 
     if (!result.success) {
diff --git a/modules/auth/components/SignOutButton.tsx b/modules/auth/components/SignOutButton.tsx
index e0d5c26..2faf9fe 100644
--- a/modules/auth/components/SignOutButton.tsx
+++ b/modules/auth/components/SignOutButton.tsx
@@ -5,8 +5,13 @@ import { useRouter } from "next/navigation";
 import { useState } from "react";
 
 import { Button } from "@/components/ui/button";
+import { cn } from "@/lib/utils";
 
-export function SignOutButton(): React.ReactElement {
+type SignOutButtonProps = {
+  className?: string;
+};
+
+export function SignOutButton({ className }: SignOutButtonProps): React.ReactElement {
   const router = useRouter();
   const [isPending, setIsPending] = useState(false);
 
@@ -25,6 +30,7 @@ export function SignOutButton(): React.ReactElement {
       onClick={handleSignOut}
       disabled={isPending}
       aria-label="退出登录"
+      className={cn(className)}
     >
       <LogOut className="size-4" aria-hidden="true" />
       <span className="hidden sm:inline">退出</span>
diff --git a/modules/shared/components/AppShell.tsx b/modules/shared/components/AppShell.tsx
index 009f084..c04d4da 100644
--- a/modules/shared/components/AppShell.tsx
+++ b/modules/shared/components/AppShell.tsx
@@ -192,6 +192,17 @@ export function AppShell({ children, account, permissions }: AppShellProps): Rea
               ))}
             </div>
           </nav>
+
+          <div className="border-t p-3">
+            <div className="flex min-w-0 items-center gap-3 rounded-md bg-secondary/55 p-2">
+              <UserAvatar avatarUrl={account.avatarUrl} name={account.name} size="sm" />
+              <div className="min-w-0 flex-1">
+                <p className="truncate text-sm font-medium leading-tight">{account.name}</p>
+                <p className="truncate text-xs leading-tight text-muted-foreground">{account.email}</p>
+              </div>
+            </div>
+            <SignOutButton className="mt-2 w-full justify-start" />
+          </div>
         </div>
       </aside>
 
@@ -205,12 +216,12 @@ export function AppShell({ children, account, permissions }: AppShellProps): Rea
               <p className="text-sm font-medium">工作台</p>
             </div>
           </div>
-          <div className="flex items-center gap-2">
-            <div className="hidden items-center gap-2 sm:flex">
-              <div className="text-right">
-                <p className="text-sm font-medium">{account.name}</p>
-                <p className="text-xs text-muted-foreground">{account.email}</p>
-              </div>
+          <div className="flex min-w-0 items-center gap-2 xl:hidden">
+            <div className="hidden min-w-0 items-center gap-2 sm:flex">
+              <p className="min-w-0 max-w-[min(52vw,24rem)] truncate whitespace-nowrap text-right text-sm leading-tight">
+                <span className="font-medium">{account.name}</span>
+                <span className="ml-2 text-muted-foreground">{account.email}</span>
+              </p>
               <UserAvatar avatarUrl={account.avatarUrl} name={account.name} size="sm" />
             </div>
             <SignOutButton />