diff --git a/src/components/ui/Select.module.scss b/src/components/ui/Select.module.scss
index 93f1f03..7a3bd32 100644
--- a/src/components/ui/Select.module.scss
+++ b/src/components/ui/Select.module.scss
@@ -67,11 +67,7 @@
 }
 
 .dropdown {
-  position: absolute;
-  top: calc(100% + 6px);
-  left: 0;
-  right: 0;
-  z-index: 1000;
+  position: fixed;
   background: var(--bg-primary);
   border: 1px solid var(--border-color);
   border-radius: $radius-lg;
@@ -83,6 +79,7 @@
   max-height: 240px;
   overflow-y: auto;
   overscroll-behavior: contain;
+  scrollbar-gutter: stable;
 }
 
 .option {
diff --git a/src/components/ui/Select.tsx b/src/components/ui/Select.tsx
index 3bd9e91..9c36515 100644
--- a/src/components/ui/Select.tsx
+++ b/src/components/ui/Select.tsx
@@ -1,4 +1,14 @@
-import { useCallback, useEffect, useId, useMemo, useRef, useState } from 'react';
+import {
+  useCallback,
+  useEffect,
+  useId,
+  useLayoutEffect,
+  useMemo,
+  useRef,
+  useState,
+  type CSSProperties
+} from 'react';
+import { createPortal } from 'react-dom';
 import { IconChevronDown } from './icons';
 import styles from './Select.module.scss';
 
@@ -21,6 +31,51 @@ interface SelectProps {
   id?: string;
 }
 
+const VIEWPORT_MARGIN = 8;
+const DROPDOWN_OFFSET = 6;
+const DROPDOWN_MAX_HEIGHT = 240;
+const DROPDOWN_Z_INDEX = 2010;
+
+const clamp = (value: number, min: number, max: number) => Math.min(Math.max(value, min), max);
+
+const resolveDropdownStyle = (element: HTMLElement): CSSProperties => {
+  const rect = element.getBoundingClientRect();
+  const viewportWidth = window.innerWidth;
+  const viewportHeight = window.innerHeight;
+  const width = Math.min(rect.width, Math.max(0, viewportWidth - VIEWPORT_MARGIN * 2));
+  const left = clamp(
+    rect.left,
+    VIEWPORT_MARGIN,
+    Math.max(VIEWPORT_MARGIN, viewportWidth - width - VIEWPORT_MARGIN)
+  );
+  const spaceBelow = viewportHeight - rect.bottom - VIEWPORT_MARGIN - DROPDOWN_OFFSET;
+  const spaceAbove = rect.top - VIEWPORT_MARGIN - DROPDOWN_OFFSET;
+  const direction =
+    spaceBelow >= DROPDOWN_MAX_HEIGHT || spaceBelow >= spaceAbove ? 'down' : 'up';
+  const maxHeight = Math.max(
+    0,
+    Math.min(DROPDOWN_MAX_HEIGHT, direction === 'down' ? spaceBelow : spaceAbove)
+  );
+
+  return direction === 'down'
+    ? {
+        position: 'fixed',
+        top: rect.bottom + DROPDOWN_OFFSET,
+        left,
+        width,
+        maxHeight,
+        zIndex: DROPDOWN_Z_INDEX
+      }
+    : {
+        position: 'fixed',
+        bottom: viewportHeight - rect.top + DROPDOWN_OFFSET,
+        left,
+        width,
+        maxHeight,
+        zIndex: DROPDOWN_Z_INDEX
+      };
+};
+
 export function Select({
   value,
   options,
@@ -40,17 +95,78 @@ export function Select({
   const [open, setOpen] = useState(false);
   const [highlightedIndex, setHighlightedIndex] = useState(-1);
   const wrapRef = useRef<HTMLDivElement | null>(null);
+  const dropdownRef = useRef<HTMLDivElement | null>(null);
+  const rafRef = useRef<number | null>(null);
+  const [dropdownStyle, setDropdownStyle] = useState<CSSProperties | null>(null);
+  const isOpen = open && !disabled;
 
   useEffect(() => {
     if (!open || disabled) return;
     const handleClickOutside = (event: MouseEvent) => {
-      if (!wrapRef.current?.contains(event.target as Node)) setOpen(false);
+      const target = event.target as Node;
+      if (wrapRef.current?.contains(target) || dropdownRef.current?.contains(target)) return;
+      setOpen(false);
     };
     document.addEventListener('mousedown', handleClickOutside);
     return () => document.removeEventListener('mousedown', handleClickOutside);
   }, [disabled, open]);
 
-  const isOpen = open && !disabled;
+  const updateDropdownStyle = useCallback(() => {
+    if (!wrapRef.current) return;
+    setDropdownStyle(resolveDropdownStyle(wrapRef.current));
+  }, []);
+
+  const scheduleDropdownStyleUpdate = useCallback(() => {
+    if (typeof window === 'undefined') return;
+    if (rafRef.current !== null) {
+      window.cancelAnimationFrame(rafRef.current);
+    }
+    rafRef.current = window.requestAnimationFrame(() => {
+      rafRef.current = null;
+      updateDropdownStyle();
+    });
+  }, [updateDropdownStyle]);
+
+  useLayoutEffect(() => {
+    if (!isOpen) {
+      if (rafRef.current !== null && typeof window !== 'undefined') {
+        window.cancelAnimationFrame(rafRef.current);
+        rafRef.current = null;
+      }
+      return;
+    }
+
+    updateDropdownStyle();
+
+    const handleViewportChange = () => {
+      scheduleDropdownStyleUpdate();
+    };
+
+    const resizeObserver =
+      typeof ResizeObserver !== 'undefined' && wrapRef.current
+        ? new ResizeObserver(() => {
+            scheduleDropdownStyleUpdate();
+          })
+        : null;
+
+    if (resizeObserver && wrapRef.current) {
+      resizeObserver.observe(wrapRef.current);
+    }
+
+    window.addEventListener('resize', handleViewportChange);
+    window.addEventListener('scroll', handleViewportChange, true);
+
+    return () => {
+      window.removeEventListener('resize', handleViewportChange);
+      window.removeEventListener('scroll', handleViewportChange, true);
+      resizeObserver?.disconnect();
+      if (rafRef.current !== null) {
+        window.cancelAnimationFrame(rafRef.current);
+        rafRef.current = null;
+      }
+    };
+  }, [isOpen, scheduleDropdownStyleUpdate, updateDropdownStyle]);
+
   const selectedIndex = useMemo(() => options.findIndex((option) => option.value === value), [options, value]);
   const resolvedHighlightedIndex =
     highlightedIndex >= 0 ? highlightedIndex : selectedIndex >= 0 ? selectedIndex : options.length > 0 ? 0 : -1;
@@ -136,60 +252,80 @@ export function Select({
     [commitSelection, disabled, isOpen, moveHighlight, options.length, resolvedHighlightedIndex]
   );
 
+  useEffect(() => {
+    if (!isOpen || resolvedHighlightedIndex < 0) return;
+    const highlightedOption = document.getElementById(`${selectId}-option-${resolvedHighlightedIndex}`);
+    highlightedOption?.scrollIntoView({ block: 'nearest' });
+  }, [isOpen, resolvedHighlightedIndex, selectId]);
+
+  const dropdown =
+    isOpen && dropdownStyle
+      ? (
+          <div
+            ref={dropdownRef}
+            className={styles.dropdown}
+            id={listboxId}
+            role="listbox"
+            aria-label={ariaLabel}
+            style={dropdownStyle}
+          >
+            {options.map((opt, index) => {
+              const active = opt.value === value;
+              const highlighted = index === resolvedHighlightedIndex;
+              return (
+                <button
+                  key={opt.value}
+                  id={`${selectId}-option-${index}`}
+                  type="button"
+                  role="option"
+                  aria-selected={active}
+                  className={`${styles.option} ${active ? styles.optionActive : ''} ${highlighted ? styles.optionHighlighted : ''}`.trim()}
+                  onMouseEnter={() => setHighlightedIndex(index)}
+                  onKeyDown={handleKeyDown}
+                  onClick={() => commitSelection(index)}
+                >
+                  {opt.label}
+                </button>
+              );
+            })}
+          </div>
+        )
+      : null;
+
   return (
-    <div
-      className={`${styles.wrap} ${fullWidth ? styles.wrapFullWidth : ''} ${className ?? ''}`}
-      ref={wrapRef}
-    >
-      <button
-        id={selectId}
-        type="button"
-        className={styles.trigger}
-        onClick={disabled ? undefined : () => setOpen((prev) => !prev)}
-        onKeyDown={handleKeyDown}
-        aria-haspopup="listbox"
-        aria-expanded={isOpen}
-        aria-controls={isOpen ? listboxId : undefined}
-        aria-activedescendant={
-          isOpen && resolvedHighlightedIndex >= 0
-            ? `${selectId}-option-${resolvedHighlightedIndex}`
-            : undefined
-        }
-        aria-label={ariaLabel}
-        aria-labelledby={ariaLabelledBy}
-        aria-describedby={ariaDescribedBy}
-        disabled={disabled}
+    <>
+      <div
+        className={`${styles.wrap} ${fullWidth ? styles.wrapFullWidth : ''} ${className ?? ''}`}
+        ref={wrapRef}
       >
-        <span className={`${styles.triggerText} ${isPlaceholder ? styles.placeholder : ''}`}>
-          {displayText}
-        </span>
-        <span className={styles.triggerIcon} aria-hidden="true">
-          <IconChevronDown size={14} />
-        </span>
-      </button>
-      {isOpen && (
-        <div className={styles.dropdown} id={listboxId} role="listbox" aria-label={ariaLabel}>
-          {options.map((opt, index) => {
-            const active = opt.value === value;
-            const highlighted = index === resolvedHighlightedIndex;
-            return (
-              <button
-                key={opt.value}
-                id={`${selectId}-option-${index}`}
-                type="button"
-                role="option"
-                aria-selected={active}
-                className={`${styles.option} ${active ? styles.optionActive : ''} ${highlighted ? styles.optionHighlighted : ''}`.trim()}
-                onMouseEnter={() => setHighlightedIndex(index)}
-                onKeyDown={handleKeyDown}
-                onClick={() => commitSelection(index)}
-              >
-                {opt.label}
-              </button>
-            );
-          })}
-        </div>
-      )}
-    </div>
+        <button
+          id={selectId}
+          type="button"
+          className={styles.trigger}
+          onClick={disabled ? undefined : () => setOpen((prev) => !prev)}
+          onKeyDown={handleKeyDown}
+          aria-haspopup="listbox"
+          aria-expanded={isOpen}
+          aria-controls={isOpen ? listboxId : undefined}
+          aria-activedescendant={
+            isOpen && resolvedHighlightedIndex >= 0
+              ? `${selectId}-option-${resolvedHighlightedIndex}`
+              : undefined
+          }
+          aria-label={ariaLabel}
+          aria-labelledby={ariaLabelledBy}
+          aria-describedby={ariaDescribedBy}
+          disabled={disabled}
+        >
+          <span className={`${styles.triggerText} ${isPlaceholder ? styles.placeholder : ''}`}>
+            {displayText}
+          </span>
+          <span className={styles.triggerIcon} aria-hidden="true">
+            <IconChevronDown size={14} />
+          </span>
+        </button>
+      </div>
+      {dropdown && (typeof document === 'undefined' ? dropdown : createPortal(dropdown, document.body))}
+    </>
   );
 }