diff --git a/README.md b/README.md
index af8022afc..1c8888f18 100644
--- a/README.md
+++ b/README.md
@@ -171,6 +171,19 @@ adds any) and extra goodies that are included in that particular plugin.
 
 ### Themes
 
+Preview installed themes in your current directory without changing your prompt or `.zshrc`:
+
+```zsh
+omz theme browse              # Interactive browser
+omz theme browse agn          # Start with a theme-name filter
+omz theme preview agnoster    # Print one isolated static preview
+```
+
+In the browser, type to filter, use Up/Down or Ctrl-P/Ctrl-N to navigate, and press Enter
+for explicit use/save actions. Esc or Ctrl-C cancels without applying a theme.
+See the [theme browser guide](tools/theme-browser.md) for shortcuts, preview limitations,
+and local testing instructions.
+
 We'll admit it. Early in the Oh My Zsh world, we may have gotten a bit too theme-happy. We have over one
 hundred and fifty themes now bundled. Most of them have
 [screenshots](https://github.com/ohmyzsh/ohmyzsh/wiki/Themes) on the wiki (We are working on updating this!).
diff --git a/lib/cli.zsh b/lib/cli.zsh
index a86434411..d15b977a7 100644
--- a/lib/cli.zsh
+++ b/lib/cli.zsh
@@ -51,7 +51,7 @@ function _omz {
         _describe 'command' subcmds ;;
       pr) subcmds=('clean:Delete all Pull Request branches' 'test:Test a Pull Request')
         _describe 'command' subcmds ;;
-      theme) subcmds=('list:List themes' 'set:Set a theme in your .zshrc file' 'use:Load a theme')
+      theme) subcmds=('browse:Browse theme previews' 'preview:Preview a theme without applying it' 'list:List themes' 'set:Set a theme in your .zshrc file' 'use:Load a theme')
         _describe 'command' subcmds ;;
     esac
   elif (( CURRENT == 4 )); then
@@ -77,6 +77,10 @@ function _omz {
         local -a opts
         opts=('--enabled:List enabled plugins only')
         _describe -o 'options' opts ;;
+      theme::(browse|preview))
+        local -a themes
+        themes=("${(@f)$(source "$ZSH/tools/theme-preview.zsh"; _omz_theme_names)}")
+        _describe 'theme' themes ;;
       theme::(set|use))
         local -aU themes
         themes=("$ZSH"/themes/*.zsh-theme(-.N:t:r) "$ZSH_CUSTOM"/**/*.zsh-theme(-.N:r:gs:"$ZSH_CUSTOM"/themes/:::gs:"$ZSH_CUSTOM"/:::))
@@ -749,6 +753,8 @@ Usage: ${(j: :)${(s.::.)0#_}} <command> [options]
 
 Available commands:
 
+  browse [filter] Browse installed themes without applying them
+  preview <theme> Preview a theme in the current directory
   list            List all available Oh My Zsh themes
   set <theme>     Set a theme in your .zshrc file
   use <theme>     Load a theme
@@ -763,6 +769,45 @@ EOF
   $0::$command "$@"
 }
 
+function _omz::theme::preview {
+  if (( $# != 1 )); then
+    print -u2 -r -- 'Usage: omz theme preview <theme>'
+    return 1
+  fi
+  source "$ZSH/tools/theme-preview.zsh"
+  _omz_theme_preview "$1"
+}
+
+function _omz::theme::browse {
+  if (( $# > 1 )); then
+    print -u2 -r -- 'Usage: omz theme browse [filter]'
+    return 1
+  fi
+  if [[ ! -o interactive || ! -t 0 || ! -t 1 ]]; then
+    print -u2 -r -- 'omz theme browse requires an interactive terminal; use omz theme preview <theme> instead.'
+    return 1
+  fi
+  source "$ZSH/tools/theme-preview.zsh"
+  source "$ZSH/tools/theme-browser.zsh"
+  local selection action name
+  selection=$(_omz_theme_browser "$1") || return $?
+  [[ -n $selection ]] || return 0
+  action=${selection%%$'\n'*}
+  name=${selection#*$'\n'}
+  _omz_theme_resolve "$name" >/dev/null || return 1
+  case $action in
+    use) _omz::theme::use "$name" ;;
+    set)
+      # The existing set command interpolates the name into shell and awk text.
+      [[ $name != *[^a-zA-Z0-9_./-]* ]] || {
+        print -u2 -r -- 'Cannot save this theme name safely; set ZSH_THEME manually.'
+        return 1
+      }
+      _omz::theme::set "$name" ;;
+    *) return 1 ;;
+  esac
+}
+
 function _omz::theme::list {
   local -a custom_themes builtin_themes
   custom_themes=("$ZSH_CUSTOM"/**/*.zsh-theme(-.N:r:gs:"$ZSH_CUSTOM"/themes/:::gs:"$ZSH_CUSTOM"/:::))
diff --git a/tools/tests/theme-browser.zsh b/tools/tests/theme-browser.zsh
new file mode 100644
index 000000000..b2512a8bb
--- /dev/null
+++ b/tools/tests/theme-browser.zsh
@@ -0,0 +1,350 @@
+#!/usr/bin/env zsh
+# Run with: zsh -df tools/tests/theme-browser.zsh
+# Optionally pass one group, e.g. `slow-interrupt`, to run it alone.
+# Each browser runs under a real controlling PTY, with no user startup files.
+emulate -R zsh
+
+if [[ $1 == --child ]]; then
+  if [[ $2 == completion ]]; then
+    function compdef { print -r -- "REGISTERED:${(j.:.)@}"; }
+  fi
+  source "$ZSH/lib/cli.zsh"
+  # Match normal OMZ sessions without sourcing any user startup/configuration.
+  setopt promptsubst
+  print -r -- "LAZY:$+functions[_omz_theme_browser]:$+functions[_omz_theme_preview]"
+  if [[ $2 == completion ]]; then
+    # Capture the real completion function's candidates without loading the
+    # user's completion setup or replacing any CLI/backend functions.
+    function _describe { print -rl -- "DESCRIBE:$1" "${(@P)2}"; }
+    CURRENT=3 words=(omz theme '')
+    print -r -- SUBCOMMANDS
+    _omz
+    print -r -- END_SUBCOMMANDS
+    for action in browse preview set use; do
+      CURRENT=4 words=(omz theme "$action" '')
+      print -r -- "CANDIDATES:$action"
+      _omz
+      print -r -- "END:$action"
+    done
+    print -r -- "STILL_LAZY:$+functions[_omz_theme_browser]:$+functions[_omz_theme_preview]"
+    print -r -- COMPLETIONS_FINISHED
+    exit
+  fi
+  if [[ $2 == reject* ]]; then
+    case $2 in
+      reject-stdin) omz theme browse </dev/null ;;
+      reject-stdout) omz theme browse >/dev/null ;;
+      *) omz theme browse ;;
+    esac
+    result=$?
+    print -r -- "REJECT:$result:$+functions[_omz_theme_browser]:$+functions[_omz_theme_preview]"
+    exit
+  fi
+  function _omz::theme::use { calls+=("use:$1"); ZSH_THEME=$1; }
+  function _omz::theme::set { calls+=("set:$1"); ZSH_THEME=$1; }
+  function browser_test_hook { : parent-hook; }
+  function precmd { : parent-precmd; }
+  typeset -a calls=() precmd_functions=(browser_test_hook) chpwd_functions=(browser_test_hook)
+  ZSH_THEME=parent-theme PROMPT=parent-prompt RPROMPT=parent-rprompt
+  typeset original_hook=$functions[browser_test_hook] original_precmd=$functions[precmd]
+  typeset original_options=$(setopt) original_pwd=$PWD
+  stty rows 24 cols 100
+  # PENDIN is a transient kernel input-reprocessing flag, not a user mode.
+  typeset original_tty=$(stty -a)
+  original_tty=${${original_tty//-pendin/}//pendin/}
+  tty > "$TEST_SCRATCH/tty"
+  print -r -- READY
+  # An interactive script otherwise aborts on SIGINT instead of returning to
+  # the next prompt as an interactive command loop would.
+  trap ':' INT
+  omz theme browse "$2"
+  result=$?
+  typeset restored_tty=$(stty -a)
+  restored_tty=${${restored_tty//-pendin/}//pendin/}
+  if [[ $restored_tty == "$original_tty" ]]; then
+    print -r -- TTY_RESTORED
+  else
+    print -r -- "TTY_MISMATCH:before=$original_tty after=$restored_tty"
+  fi
+  if [[ $PROMPT == parent-prompt && $RPROMPT == parent-rprompt &&
+        $functions[browser_test_hook] == "$original_hook" &&
+        $functions[precmd] == "$original_precmd" &&
+        ${(j:,:)precmd_functions} == browser_test_hook &&
+        ${(j:,:)chpwd_functions} == browser_test_hook &&
+        -o promptsubst && $(setopt) == "$original_options" && $PWD == "$original_pwd" &&
+        ${BROWSER_TEST_LEAK-unset} == unset ]]; then
+    print -r -- PARENT_UNCHANGED
+  fi
+  print -r -- "RESULT:$result:${(j:,:)calls}:$ZSH_THEME"
+  print -r -- FINISHED
+  exit 0
+fi
+
+setopt err_exit pipe_fail
+[[ -n $BROWSER_TEST_TRACE ]] && setopt xtrace
+zmodload zsh/zpty
+zmodload zsh/datetime
+zmodload zsh/zselect
+typeset -r repo=${0:A:h:h:h} self=${0:A}
+typeset scratch=$(mktemp -d "${TMPDIR:-/tmp}/omz-browser-test.XXXXXXXX")
+scratch=${scratch:A}
+trap 'zpty -d 2>/dev/null; command rm -rf -- "$scratch"' EXIT
+trap 'exit 130' INT
+trap 'exit 143' TERM
+mkdir -p "$scratch/home" "$scratch/custom/themes/nested" "$scratch/tmp"
+export ZSH=$repo ZSH_CUSTOM=$scratch/custom HOME=$scratch/home ZDOTDIR=$scratch/home
+export TMPDIR=$scratch/tmp TEST_SCRATCH=$scratch TERM=xterm-256color
+unset ZSH_THEME
+# Even a mistakenly enabled startup-file load must never reach real dotfiles.
+print -r -- 'print STARTUP_RAN; exit 99' > "$HOME/.zshenv"
+print -r -- 'PROMPT="nested fixture"' > "$ZSH_CUSTOM/themes/nested/browser-fixture.zsh-theme"
+for number in {01..10}; do
+  print -r -- 'typeset -g BROWSER_TEST_LEAK=bad
+ZSH_THEME=fixture-theme
+precmd_functions=() chpwd_functions=()
+function precmd { PROMPT="%F{red}FIXTURE_PREVIEW%f" }
+RPROMPT="fixture-right"' > "$ZSH_CUSTOM/zz-omz-test-$number.zsh-theme"
+done
+print -r -- 'sleep 30 &
+print -r -- $! > "$TEST_SCRATCH/slow-pid"
+wait
+PROMPT="SLOW_FINISHED"' > "$ZSH_CUSTOM/zz-omz-test-slow.zsh-theme"
+typeset filter_probe='$(print HIT > $TEST_SCRATCH/filter-executed)'
+typeset preview_probe='$(print HIT > $TEST_SCRATCH/preview-executed)'
+# Emit literal preview output, rather than asking the worker to evaluate a
+# prompt expression. Only a second evaluation by the browser can execute it.
+print -rl -- "print -r -- ${(q)preview_probe}" 'PROMPT="literal-preview-ready"' > "$ZSH_CUSTOM/literal-browser.zsh-theme"
+
+typeset buffer='' transcript='' chunk='' label=''
+typeset -F browser_finished_at=0
+function cleanup_pty {
+  local record group
+  for record in "${(@f)$(zpty)}"; do
+    [[ $record == \(<->\)\ browser:* ]] || continue
+    group=${${record#\(}%%\)*}
+    kill -HUP -- -$group 2>/dev/null || true
+    zselect -t 20 || true
+    # A renderer regression can loop without checking its cancellation flag.
+    kill -KILL -- -$group 2>/dev/null || true
+  done
+  zpty -d 2>/dev/null || true
+  return 0
+}
+function fail {
+  print -u2 -r -- "FAIL: $label: $1"
+  print -u2 -r -- "PTY transcript, last 4000 characters (escaped): ${(V)transcript[-4000,-1]}"
+  exit 1
+}
+function check {
+  "$@" || fail "$1 assertion failed"
+}
+function await {
+  local wanted=$1
+  local -F deadline=$(( EPOCHREALTIME + ${2:-6} ))
+  [[ $buffer == *"$wanted"* ]] && return 0
+  while (( EPOCHREALTIME < deadline )); do
+    if zpty -r browser chunk; then
+      buffer+=$chunk transcript+=$chunk
+      [[ $buffer == *"$wanted"* ]] && return 0
+    else
+      zselect -t 1 || true
+    fi
+  done
+  fail "timed out waiting for ${(V)wanted}"
+}
+function send {
+  buffer=''
+  zpty -w -n browser "$1"
+}
+function start {
+  label=$1 buffer='' transcript=''
+  local -a launch=("$commands[zsh]" -dfi "$self" --child "$2")
+  zpty -b browser exec "${(@q)launch}"
+  await 'LAZY:0:0'
+  await "$3"
+}
+function finish {
+  await FINISHED
+  # zpty -d can spend a second reaping an already-completed child. It is
+  # harness teardown, not browser cancellation/terminal-restoration latency.
+  browser_finished_at=$EPOCHREALTIME
+  check test "${transcript#*TTY_RESTORED}" != "$transcript"
+  check test "${transcript#*PARENT_UNCHANGED}" != "$transcript"
+  check test "${transcript#*RESULT:$1}" != "$transcript"
+  check test "${transcript#*$'\e[?1049l'}" != "$transcript"
+  check test "${transcript#*$'\e[?25h'}" != "$transcript"
+  check test "${transcript#*STARTUP_RAN}" = "$transcript"
+  zpty -d browser
+  [[ -z $BROWSER_TEST_TIMING ]] || print -r -- "TIMING: PTY deletion $(( EPOCHREALTIME - browser_finished_at ))s"
+}
+
+function test_completion {
+  start 'completion registration, commands, theme candidates, lazy loading' completion COMPLETIONS_FINISHED
+  check test "${transcript#*REGISTERED:_omz:omz}" != "$transcript"
+  local section=${${transcript#*SUBCOMMANDS}%END_SUBCOMMANDS*} action
+  check test "${section#*browse:Browse theme previews}" != "$section"
+  check test "${section#*preview:Preview a theme without applying it}" != "$section"
+  for action in browse preview set use; do
+    section=${${transcript#*CANDIDATES:$action}%END:$action*}
+    check test "${section#*DESCRIBE:theme}" != "$section"
+    for name in robbyrussell zz-omz-test-01 nested/browser-fixture; do
+      check test "${section#*$name}" != "$section"
+    done
+  done
+  check test "${transcript#*STILL_LAZY:0:0}" != "$transcript"
+  check test "${transcript#*STARTUP_RAN}" = "$transcript"
+  zpty -d browser
+}
+
+function test_rejection {
+  # Noninteractive rejection even with both descriptors attached to a PTY.
+  label=noninteractive
+  typeset -a launch=("$commands[zsh]" -df "$self" --child reject)
+  zpty -b browser exec "${(@q)launch}"
+  await 'REJECT:1:0:0'
+  check test "${transcript#*requires an interactive terminal}" != "$transcript"
+  zpty -d browser
+  for mode in stdin stdout; do
+    start "redirected $mode" "reject-$mode" 'REJECT:1:0:0'
+    check test "${transcript#*requires an interactive terminal}" != "$transcript"
+    zpty -d browser
+  done
+  label='noninteractive and redirected-I/O rejection'
+}
+
+function test_navigation {
+  start 'filter, navigation, actions/back, Esc isolation' zz-omz-test- '> zz-omz-test-01'
+  await FIXTURE_PREVIEW
+  send $'\e[B'; await '> zz-omz-test-02'
+  send $'\e[A'; await '> zz-omz-test-01'
+  send $'\x0e'; await '> zz-omz-test-02'
+  send $'\x10'; await '> zz-omz-test-01'
+  send $'\e[6~'; await '> zz-omz-test-05'
+  send $'\e[5~'; await '> zz-omz-test-01'
+  send '09'; await '> zz-omz-test-09'
+  send $'\x7f'; await '(9 themes)'
+  send $'\x15'; await 'Filter:   ('
+  send 'ZZ-OMZ-TEST-03'; await '> zz-omz-test-03'
+  send $'\r'; await '[u] Use in session'
+  send b; await 'Enter: actions'
+  send $'\x15no-such-omz-fixture'; await 'No matching themes.'
+  send $'\r'; await 'No matching themes.'
+  send $'\e'
+  finish '0::parent-theme'
+}
+
+function test_use {
+  start 'explicit use dispatch' zz-omz-test-01 '> zz-omz-test-01'
+  send $'\r'; await '[u] Use in session'
+  send u
+  finish '0:use:zz-omz-test-01:zz-omz-test-01'
+}
+
+function test_promptsubst {
+  start 'literal filter/preview substitutions with parent promptsubst enabled' literal-browser '> literal-browser'
+  await "$preview_probe"
+  await literal-preview-ready
+  check test ! -e "$scratch/preview-executed"
+  send $'\x15'"$filter_probe"
+  await "Filter: $filter_probe"
+  await 'No matching themes.'
+  check test ! -e "$scratch/filter-executed"
+  send $'\x15literal-browser'
+  await "$preview_probe"
+  await literal-preview-ready
+  send $'\e'
+  finish '0::parent-theme'
+  check test ! -e "$scratch/filter-executed"
+  check test ! -e "$scratch/preview-executed"
+}
+
+function test_save {
+  start 'explicit save dispatch (stubbed)' zz-omz-test-02 '> zz-omz-test-02'
+  send $'\r'; await '[u] Use in session'
+  send s
+  finish '0:set:zz-omz-test-02:zz-omz-test-02'
+}
+
+function test_interrupt {
+  start 'Ctrl-C restores terminal' zz-omz-test-01 '> zz-omz-test-01'
+  send $'\x03'
+  finish '130::parent-theme'
+}
+
+function test_resize {
+  start 'resize small and back' zz-omz-test-01 '> zz-omz-test-01'
+  typeset terminal=$(<"$scratch/tty")
+  terminal=${terminal//$'\r'/}
+  buffer=''
+  stty rows 10 cols 30 < "$terminal"
+  await '40 columns x 16 rows.'
+  buffer=''
+  stty rows 24 cols 100 < "$terminal"
+  await '> zz-omz-test-01'
+  send $'\e'
+  finish '0::parent-theme'
+}
+
+function test_slow {
+  local cancellation=$1
+  command rm -f "$scratch/slow-pid"
+  start "slow preview cancellation: $cancellation" zz-omz-test-slow '> zz-omz-test-slow'
+  for attempt in {1..150}; do
+    [[ -s "$scratch/slow-pid" ]] && break
+    zselect -t 1 || true
+  done
+  check test -s "$scratch/slow-pid"
+  typeset -F started=$EPOCHREALTIME
+  case $cancellation in
+    navigation)
+      send $'\x15zz-omz-test-01'
+      await FIXTURE_PREVIEW 2
+      [[ -z $BROWSER_TEST_TIMING ]] || print -r -- "TIMING: navigation preview $(( EPOCHREALTIME - started ))s"
+      (( EPOCHREALTIME - started < 2 )) || fail 'replacement preview exceeded 2 seconds'
+      send $'\e'
+      finish '0::parent-theme'
+      ;;
+    escape) send $'\e'; finish '0::parent-theme' ;;
+    interrupt) send $'\x03'; finish '130::parent-theme' ;;
+  esac
+  [[ -z $BROWSER_TEST_TIMING ]] || print -r -- "TIMING: browser completed $(( browser_finished_at - started ))s; including teardown $(( EPOCHREALTIME - started ))s"
+  (( browser_finished_at - started < 2 )) || fail "browser completion exceeded 2 seconds: $(( browser_finished_at - started ))s"
+  typeset child=$(<"$scratch/slow-pid") child_state
+  for attempt in {1..100}; do
+    child_state=$(command ps -o stat= -p "$child" 2>/dev/null || true)
+    [[ -z "${child_state//[ ZN+]/}" ]] && break
+    zselect -t 1 || true
+  done
+  [[ -z $BROWSER_TEST_TIMING ]] || print -r -- "TIMING: descendant $child state=${child_state:-absent}, cleanup polls=$attempt"
+  [[ -z "${child_state//[ ZN+]/}" ]] || fail "preview descendant $child still running: $child_state"
+}
+
+# Keep independent regressions running after a failed UI session.
+unsetopt err_exit
+typeset -i failures=0
+for scenario in rejection completion navigation promptsubst use save interrupt resize slow-navigation slow-escape slow-interrupt; do
+  [[ -z $1 || $scenario == "$1" ]] || continue
+  (
+    setopt err_exit
+    trap 'cleanup_pty' EXIT
+    if [[ $scenario == slow-* ]]; then
+      test_slow "${scenario#slow-}"
+    else
+      test_$scenario
+    fi
+    print -r -- "PASS: $label"
+  )
+  (( $? == 0 )) || (( failures++ ))
+done
+typeset -a leftovers
+for attempt in {1..100}; do
+  leftovers=("$TMPDIR"/omz-preview.*(N))
+  (( $#leftovers == 0 )) && break
+  zselect -t 1 || true
+done
+if (( $#leftovers )); then
+  print -u2 -r -- "FAIL: $#leftovers preview temporary directories remain"
+  (( failures++ ))
+fi
+print -r -- "Theme browser regression groups failed: $failures"
+(( failures == 0 ))
diff --git a/tools/tests/theme-preview.zsh b/tools/tests/theme-preview.zsh
new file mode 100644
index 000000000..ba0812927
--- /dev/null
+++ b/tools/tests/theme-preview.zsh
@@ -0,0 +1,282 @@
+#!/usr/bin/env zsh
+# Run with: zsh -df tools/tests/theme-preview.zsh
+emulate -R zsh
+setopt err_exit pipe_fail
+typeset -r repo=${0:A:h:h:h}
+source "$repo/tools/theme-preview.zsh"
+typeset scratch=$(mktemp -d "${TMPDIR:-/tmp}/omz-preview-test.XXXXXXXX")
+scratch=${scratch:A}
+trap 'command rm -rf -- "$scratch"' EXIT
+trap 'exit 130' INT
+trap 'exit 143' TERM
+mkdir "$scratch/tmp"
+export TMPDIR=$scratch/tmp
+
+function check {
+  if ! "$@"; then
+    print -u2 -r -- "FAIL: ${(j: :)@}"
+    exit 1
+  fi
+}
+
+export ZSH=$scratch/omz ZSH_CUSTOM=$scratch/custom
+mkdir -p "$ZSH/themes" "$ZSH_CUSTOM/themes/nested" "$scratch/home" "$scratch/work"
+print -r -- "PROMPT='bundled'" > "$ZSH/themes/same.zsh-theme"
+print -r -- "PROMPT='custom themes'" > "$ZSH_CUSTOM/themes/same.zsh-theme"
+print -r -- "PROMPT='custom root'" > "$ZSH_CUSTOM/same.zsh-theme"
+print -r -- "PROMPT='z'" > "$ZSH/themes/zebra.zsh-theme"
+print -r -- "PROMPT='a'" > "$ZSH/themes/alpha.zsh-theme"
+print -r -- "PROMPT='bad'" > "$ZSH/themes/"$'bad\nname.zsh-theme'
+print -r -- "PROMPT='random'" > "$ZSH/themes/random.zsh-theme"
+print -r -- "PROMPT='nested'" > "$ZSH_CUSTOM/themes/nested/example.zsh-theme"
+check test "$(_omz_theme_names)" = $'alpha\nnested/example\nsame\nzebra'
+check test "$(_omz_theme_resolve nested/example)" = "$ZSH_CUSTOM/themes/nested/example.zsh-theme"
+check test "$(_omz_theme_resolve same)" = "$ZSH_CUSTOM/same.zsh-theme"
+rm "$ZSH_CUSTOM/same.zsh-theme"
+check test "$(_omz_theme_resolve same)" = "$ZSH_CUSTOM/themes/same.zsh-theme"
+rm "$ZSH_CUSTOM/themes/same.zsh-theme"
+check test "$(_omz_theme_resolve same)" = "$ZSH/themes/same.zsh-theme"
+for name in ../same /same . .. nested/../same nested/./example nested//example random $'bad\nname' 'bad\name' missing ''; do
+  if _omz_theme_resolve "$name" > /dev/null 2>&1; then
+    print -u2 -r -- 'FAIL: accepted invalid/missing name'
+    exit 1
+  fi
+done
+
+# The fixtures intentionally write only inside this private, always-cleaned tree.
+print -r -- 'print STARTUP_RAN; exit 99' > "$scratch/home/.zshenv"
+export ZDOTDIR=$scratch/home PREVIEW_ENV=preserved
+print -r -- '
+typeset -g PREVIEW_LEAK=bad
+export PREVIEW_ENV=changed
+alias preview_leak=true
+setopt noclobber
+function precmd { PROMPT="hook:$PWD:$PREVIEW_ENV:%?" }
+function second_hook { RPROMPT="second-hook:%?" }
+precmd_functions=(second_hook)
+' > "$ZSH_CUSTOM/isolation.zsh-theme"
+typeset before_pwd=$PWD before_options=$(setopt) before_env=$PREVIEW_ENV
+typeset output=$(_omz_theme_preview isolation 7)
+check test "$PWD" = "$before_pwd"
+check test "$(setopt)" = "$before_options"
+check test "$PREVIEW_ENV" = "$before_env"
+check test "${PREVIEW_LEAK-unset}" = unset
+check test "${aliases[preview_leak]-unset}" = unset
+check test "${functions[second_hook]-unset}" = unset
+check test "${output#*hook:${PWD}:changed:7}" != "$output"
+check test "${output#*second-hook:7}" != "$output"
+check test "${output#*STARTUP_RAN}" = "$output"
+
+print -r -- 'PROMPT="env:$PREVIEW_ENV cwd:$PWD %(?.success.failure)"' > "$ZSH_CUSTOM/status.zsh-theme"
+output=$(_omz_theme_preview status)
+check test "${output#*env:preserved cwd:${PWD} success}" != "$output"
+output=$(_omz_theme_preview status 1)
+check test "${output#*failure}" != "$output"
+if _omz_theme_preview status nope >/dev/null 2>&1; then exit 1; fi
+
+# Values produced by parameters or helpers are prompt text, not shell code for
+# a second substitution pass. Check both sides and the helper's incoming status.
+export PREVIEW_REEXECUTED=$scratch/reexecuted
+export PREVIEW_LITERAL='$(print reexecuted > "$PREVIEW_REEXECUTED")'
+print -r -- '
+function literal_helper { print -r -- "helper-status:$? $PREVIEW_LITERAL" }
+PROMPT='"'"'$PREVIEW_LITERAL $(literal_helper) %?'"'"'
+RPROMPT='"'"'$(literal_helper) $PREVIEW_LITERAL %?'"'"'
+' > "$ZSH_CUSTOM/literal.zsh-theme"
+output=$(_omz_theme_preview literal 7)
+check test ! -e "$PREVIEW_REEXECUTED"
+check test "${output#*"$PREVIEW_LITERAL"}" != "$output"
+check test "${output#*helper-status:7}" != "$output"
+check test "${output#*"$PREVIEW_LITERAL 7"}" != "$output"
+print -r -- 'unsetopt promptsubst; PROMPT='"'"'$PREVIEW_LITERAL %?'"'" > "$ZSH_CUSTOM/no-subst.zsh-theme"
+output=$(_omz_theme_preview no-subst 7)
+check test "${output#*'$PREVIEW_LITERAL 7'}" != "$output"
+
+print -r -- 'PROMPT="conditional prompt"; [[ -n ${OMZ_PREVIEW_UNSET_SSH-} ]] && RPROMPT="remote"' > "$ZSH_CUSTOM/final-false.zsh-theme"
+output=$(_omz_theme_preview final-false)
+check test "${output#*conditional prompt}" != "$output"
+print -r -- 'PROMPT=""' > "$ZSH_CUSTOM/empty.zsh-theme"
+output=$(_omz_theme_preview empty)
+print -r -- 'RPROMPT="right-only"; false' > "$ZSH_CUSTOM/right-only.zsh-theme"
+output=$(_omz_theme_preview right-only)
+check test "${output#*right-only}" != "$output"
+
+# A helper can fail inside command substitution without making print -P fail.
+# Its runtime diagnostic must remain visible in the sanitized partial preview.
+print -r -- 'PROMPT='"'"'$( _omz_preview_missing_helper )'"'" > "$ZSH_CUSTOM/helper-failure.zsh-theme"
+output=$(_omz_theme_preview helper-failure 2>&1)
+check test "${output#*command not found: _omz_preview_missing_helper}" != "$output"
+
+# A failing precmd (or array hook) stops later hooks, as in interactive zsh.
+# Preserve any partial preview, but report failure rather than silently claiming
+# that an incomplete initialization is a faithful preview.
+for hook_setup in 'precmd() { return 3 }; precmd_functions=(must_not_run)' \
+  'failed_hook() { return 4 }; precmd_functions=(failed_hook must_not_run)' \
+  'failed_hook() { _omz_preview_missing_command }; precmd_functions=(failed_hook must_not_run)'; do
+  print -rl -- 'PROMPT="partial prompt"; must_not_run() { print UNEXPECTED_HOOK; }' "$hook_setup" > "$ZSH_CUSTOM/hook-failure.zsh-theme"
+  if _omz_theme_preview hook-failure >"$scratch/hook-error" 2>&1; then
+    print -u2 -r -- 'FAIL: accepted failing precmd hook'
+    exit 1
+  fi
+  output=$(<"$scratch/hook-error")
+  check test "${output#*UNEXPECTED_HOOK}" = "$output"
+  check test "${output#*remaining hooks skipped}" != "$output"
+  check test "${output#*partial prompt}" != "$output"
+done
+
+# No language runtime, timeout utility, or process-inspection utility is needed
+# by the backend. The worker still has zsh's usual autoload/module search paths.
+mkdir "$scratch/bin"
+for name in zsh mktemp mkfifo rm; do
+  ln -s "$commands[$name]" "$scratch/bin/$name"
+done
+output=$(PATH="$scratch/bin" _omz_theme_preview status)
+check test "${output#*success}" != "$output"
+print -r -- '[[ ! -t 0 && ! -t 1 && ! -t 2 && ! -o interactive ]] || exit 9; PROMPT="non-tty"' > "$ZSH_CUSTOM/non-tty.zsh-theme"
+output=$(_omz_theme_preview non-tty)
+check test "${output#*non-tty}" != "$output"
+
+print -r -- 'print -n -- "\e]52;c;SECRET\a\e[2J\r\b\ePSECRET\e\\"; PROMPT="%F{red}safe%f"' > "$ZSH_CUSTOM/escapes.zsh-theme"
+output=$(_omz_theme_preview escapes)
+check test "${output#*SECRET}" = "$output"
+check test "${output#*$'\e[2J'}" = "$output"
+check test "${output#*$'\r'}" = "$output"
+check test "${output#*$'\e[31m'safe}" != "$output"
+
+for code in 'return 1' 'exit 0' 'exit 7' 'if then' 'PROMPT="partial"; if then' \
+  'PROMPT="partial"; return 2' 'PROMPT="partial"; _omz_preview_missing_command'; do
+  print -r -- "$code" > "$ZSH_CUSTOM/broken.zsh-theme"
+  if _omz_theme_preview broken >"$scratch/error" 2>&1; then
+    print -u2 -r -- "FAIL: accepted broken theme: $code"
+    exit 1
+  fi
+done
+print -r -- 'while true; do print -r -- xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx; done' > "$ZSH_CUSTOM/flood.zsh-theme"
+if _omz_theme_preview flood >"$scratch/flood" 2>&1; then exit 1; fi
+check test "$(wc -c < "$scratch/flood")" -le 32768
+print -r -- 'printf "\377%.0s" {1..11000}; PROMPT="safe"' > "$ZSH_CUSTOM/bytes.zsh-theme"
+_omz_theme_preview bytes >"$scratch/bytes" 2>&1
+check test "$(wc -c < "$scratch/bytes")" -le 32768
+check test "${$(<"$scratch/bytes")#*$'\xff'}" = "$(<"$scratch/bytes")"
+print -r -- 'printf "\233m%.0s" {1..12000}; PROMPT="safe"' > "$ZSH_CUSTOM/csi-bytes.zsh-theme"
+_omz_theme_preview csi-bytes >"$scratch/csi-bytes" 2>&1
+check test "$(wc -c < "$scratch/csi-bytes")" -le 32768
+
+print -r -- 'sleep 30 & print -r -- $! > "$PREVIEW_PID_FILE"; wait' > "$ZSH_CUSTOM/slow.zsh-theme"
+export PREVIEW_PID_FILE=$scratch/child
+zmodload zsh/datetime
+typeset -F started=$EPOCHREALTIME
+if _omz_theme_preview slow >"$scratch/timeout" 2>&1; then exit 1; fi
+check test $(( EPOCHREALTIME - started < 5 )) = 1
+check test "${$(<"$scratch/timeout")#*timed out}" != "$(<"$scratch/timeout")"
+typeset child=$(<"$scratch/child")
+# A killed orphan may briefly remain a zombie until the system reaps it.
+typeset child_state=$(command ps -o stat= -p "$child" 2>/dev/null || true)
+check test -z "${child_state//[ ZN+]/}"
+
+for signal in INT TERM HUP; do
+  rm -f "$PREVIEW_PID_FILE"
+  _omz_theme_preview slow >"$scratch/cancel" 2>&1 &
+  typeset preview_job=$!
+  for attempt in {1..100}; do
+    [[ -s "$PREVIEW_PID_FILE" ]] && break
+    sleep 0.01
+  done
+  check test -s "$PREVIEW_PID_FILE"
+  # zsh adds a waiting wrapper around a backgrounded subshell function.
+  # Signal the supervisor itself; terminal interrupts reach it via the job group.
+  typeset supervisor='' candidate='' parent=''
+  for candidate parent in ${(z)$(command ps -A -o pid= -o ppid=)}; do
+    if [[ $parent == $preview_job ]]; then
+      supervisor=$candidate
+      break
+    fi
+  done
+  check test -n "$supervisor"
+  kill -$signal "$supervisor"
+  typeset result=0
+  wait "$preview_job" || result=$?
+  if (( result != 130 && result != 143 && result != 129 )); then
+    print -u2 -r -- "Unexpected cancellation result: $result: $(<"$scratch/cancel")"
+  fi
+  if [[ $signal == INT ]]; then
+    check test "$result" = 130
+  elif [[ $signal == TERM ]]; then
+    check test "$result" = 143
+  else
+    check test "$result" = 129
+  fi
+  child=$(<"$PREVIEW_PID_FILE")
+  child_state=$(command ps -o stat= -p "$child" 2>/dev/null || true)
+  check test -z "${child_state//[ ZN+]/}"
+done
+
+print -r -- 'sleep 30 & print -r -- $! > "$PREVIEW_PID_FILE"; PROMPT="background"' > "$ZSH_CUSTOM/background.zsh-theme"
+output=$(_omz_theme_preview background)
+child=$(<"$PREVIEW_PID_FILE")
+child_state=$(command ps -o stat= -p "$child" 2>/dev/null || true)
+check test -z "${child_state//[ ZN+]/}"
+
+# Match the browser's nested-PTY invocation, preserving other owned PTYs.
+zmodload zsh/zpty
+zpty -b unrelated 'exec sleep 30'
+typeset -a nested_command=("$commands[zsh]" -dfc 'source "$1"; _omz_theme_preview status' zsh "$repo/tools/theme-preview.zsh")
+zpty -b browser exec "${(@q)nested_command}"
+output=''
+for attempt in {1..300}; do
+  if zpty -r browser chunk; then
+    output+=$chunk
+  elif ! zpty -t browser; then
+    break
+  else
+    sleep 0.01
+  fi
+done
+check test "${output#*success}" != "$output"
+check zpty -t unrelated
+zpty -d browser unrelated
+
+# Cancellation by the browser's outer process group must also clean the
+# backend's separate inner PTY group and private FIFO directory.
+rm -f "$PREVIEW_PID_FILE"
+nested_command=("$commands[zsh]" -dfc 'source "$1"; _omz_theme_preview slow' zsh "$repo/tools/theme-preview.zsh")
+zpty -b browser exec "${(@q)nested_command}"
+typeset browser_group record
+for record in "${(@f)$(zpty)}"; do
+  [[ $record == \(<->\)\ browser:* ]] && browser_group=${${record#\(}%%\)*}
+done
+check test -n "$browser_group"
+for attempt in {1..100}; do
+  [[ -s "$PREVIEW_PID_FILE" ]] && break
+  sleep 0.01
+done
+check test -s "$PREVIEW_PID_FILE"
+child=$(<"$PREVIEW_PID_FILE")
+kill -TERM -- -$browser_group
+for attempt in {1..100}; do
+  child_state=$(command ps -o stat= -p "$child" 2>/dev/null || true)
+  [[ -z "${child_state//[ ZN+]/}" ]] && break
+  sleep 0.01
+done
+check test -z "${child_state//[ ZN+]/}"
+zpty -d browser
+
+# Real themes exercise synchronous git, top-level locals, command substitution,
+# and hook-driven prompt construction against an isolated repository.
+export ZSH=$repo
+git -C "$scratch/work" init -q
+git -C "$scratch/work" symbolic-ref HEAD refs/heads/preview-branch
+output=$(zsh -dfc 'builtin cd "$1"; source tools/theme-preview.zsh; builtin cd "$2"; _omz_theme_preview robbyrussell' zsh "$repo" "$scratch/work")
+check test "${output#*preview-branch}" != "$output"
+for name in robbyrussell dieter agnoster bira nicoulaj half-life; do
+  output=$(builtin cd "$scratch/work"; _omz_theme_preview "$name" 7)
+  check test "${output#*Left prompt}" != "$output"
+  check test "${output#*Right prompt}" != "$output"
+  check test "${output#*preview-branch}" != "$output"
+  if [[ $name == dieter || $name == bira ]]; then
+    check test "${output#*7 }" != "$output"
+  fi
+done
+typeset -a leftovers=("$TMPDIR"/omz-preview.*(N))
+check test "$#leftovers" = 0
+print -r -- 'PASS: theme preview resolution, isolation, single-pass expansion, conditional loads, hook failures, status, sanitization, limits, cancellation, descendant cleanup, and six bundled themes'
diff --git a/tools/theme-browser.md b/tools/theme-browser.md
new file mode 100644
index 000000000..280638642
--- /dev/null
+++ b/tools/theme-browser.md
@@ -0,0 +1,118 @@
+# Theme Browser
+
+```zsh
+omz theme browse
+omz theme browse agn
+omz theme preview agnoster
+```
+
+The browser renders only the highlighted theme, in your invoking directory with real,
+synchronous Git information. Filtering is a case-insensitive literal substring match.
+Names are deduplicated; resolution follows normal Oh My Zsh precedence:
+`$ZSH_CUSTOM/<name>.zsh-theme`, `$ZSH_CUSTOM/themes/<name>.zsh-theme`, then
+`$ZSH/themes/<name>.zsh-theme`. Nested custom themes are supported. The `random`
+selector and names containing traversal components or control characters are excluded.
+
+## Controls
+
+| Key | Action |
+| --- | --- |
+| Up / Down, Ctrl-P / Ctrl-N | Previous / next theme |
+| Page Up / Page Down | Move one page |
+| Printable text | Filter names |
+| Backspace | Delete the last filter character |
+| Ctrl-U | Clear the filter |
+| Enter | Open selection actions |
+| Esc / Ctrl-C | Cancel without applying or saving |
+| `u` in selection actions | Use the theme for this session |
+| `s` in selection actions | Save as default and reload the shell |
+| `b` or Enter in selection actions | Return to browsing |
+
+Using a theme calls `omz theme use`: it does **not** remove hooks, widgets, or other
+state installed by your previous theme. Saving calls `omz theme set`, edits `.zshrc`,
+and reloads the shell. These actions happen only after leaving the browser and
+restoring terminal state. Names containing shell punctuation cannot be saved through
+the browser; configure those manually. No global aliases or keybindings are installed.
+
+## Preview Limits
+
+- Each preview runs in a fresh `zsh -df` worker, not your active shell. The worker
+  inherits the directory and exported environment, but not non-exported theme
+  settings, plugins, user `.zshrc`, or custom library overrides. System `zshenv`
+  still runs as required by zsh.
+- Previews initialize prompt helpers and precmd hooks. They show a successful
+  previous command (status 0). Tests also exercise nonzero status rendering.
+- Multiline left prompts are supported. Right prompts are deliberately labeled
+  and displayed separately, not positioned as ZLE would position them.
+- Interactive/async themes, plugin-dependent segments, terminal queries, and
+  widget-driven prompts may be incomplete or unsupported. Themes still require
+  their usual fonts for special glyphs; the browser itself requires no fonts.
+- Workers have a three-second execution limit and a 32,000-byte output limit.
+  Navigation cancels obsolete work. ANSI colors are retained; other terminal
+  controls are filtered. Long lines and tall previews are clipped in the browser.
+- The browser requires an interactive terminal with alternate-screen support and
+  at least 40 columns by 16 rows. Smaller windows show a resize message; Esc still
+  exits. `omz theme preview` also works without an interactive terminal.
+- This is **shell-state isolation, not a security sandbox**. Only preview trusted
+  themes: their code can write files, access the network, or deliberately detach
+  processes. The supervisor cleans up ordinary descendants, not escaped processes.
+
+No new third-party runtime is required. The implementation uses standard zsh modules
+(`zpty`, `system`, `datetime`, `zselect`, `terminfo`) and platform utilities including
+`stty`, `mktemp`, `mkfifo`, and `rm`. Git segments need Git as usual. Private temporary
+files are removed when previews finish or are cancelled. Full OMZ startup, update
+checks, and OMZ cache initialization are not invoked by workers. The old
+`tools/theme_chooser.sh` is unchanged.
+
+## Local Testing
+
+From this checkout, launch a disposable interactive shell without reading your `.zshrc`:
+
+```zsh
+env ZSH="$PWD" zsh -dfi
+```
+
+Inside it, load the CLI and try previews. Change directory to a Git repository to
+compare clean, dirty, and untracked-file states:
+
+```zsh
+source "$ZSH/lib/cli.zsh"
+omz theme preview robbyrussell
+omz theme preview agnoster
+omz theme preview half-life
+omz theme preview dieter
+omz theme browse
+```
+
+This minimal shell is intended for preview/navigation testing. For a real session-use
+test, load this checkout's full OMZ configuration in a disposable shell. Do not choose
+Save unless you intend to edit your actual `.zshrc`; automated browser tests stub both
+actions and never edit your configuration. Exit the disposable shell when finished.
+
+Regression suites run without additional test frameworks:
+
+```zsh
+zsh -df tools/tests/theme-preview.zsh
+zsh -df tools/tests/theme-browser.zsh
+```
+
+The tests cover resolution, prompt isolation, Git context, hook/status rendering,
+terminal-control filtering, failures, time/output limits, descendant cleanup,
+completion candidates, lazy loading, keyboard navigation, resizing, action dispatch,
+and terminal restoration using real PTYs. Human visual testing in your terminal and
+font is still required before proposing a PR. Linux/older-zsh testing remains pending.
+
+## Footprint And Startup
+
+Runtime code is roughly 18 KiB across the three `tools/theme-*.zsh` files, plus small
+CLI wrappers and completion/help entries. Tests and this guide are additional text
+files, not runtime dependencies. Measure the exact current footprint with:
+
+```zsh
+wc -c tools/theme-browser.zsh tools/theme-preview.zsh tools/theme-preview-worker.zsh
+```
+
+Normal shell startup only defines the CLI wrappers: none of the three tool files is
+sourced, no browser modules are loaded, and no workers or browser I/O are started.
+The regression suite verifies lazy loading. Startup timing should be considered
+noise-sensitive; this prototype does not claim a measurable speed improvement.
diff --git a/tools/theme-browser.zsh b/tools/theme-browser.zsh
new file mode 100644
index 000000000..93fbc7488
--- /dev/null
+++ b/tools/theme-browser.zsh
@@ -0,0 +1,170 @@
+# Loaded only by `omz theme browse`. The UI runs in a subshell; stdout is a
+# two-line data handoff, while all terminal I/O goes through a private tty fd.
+function _omz_theme_browser() (
+  emulate -L zsh
+  setopt extendedglob
+  # Displayed names, filter text, and worker output are data, not prompt code.
+  unsetopt promptsubst
+  zmodload zsh/terminfo && zmodload zsh/zpty && zmodload zsh/system && zmodload zsh/datetime || return 1
+  local tty saved filter=$1 key suffix name previous='' preview='' chunk
+  local mode=browse action='' pty=omz-browser-$sysparams[pid] record pgid
+  local -a names matches lines size
+  local -i selected=1 page=1 height=0 width=0 rows=0 cols=0 active=0 dirty=1 i row cancelled=0
+  local -F render_after=0
+  [[ -n $terminfo[smcup] && -n $terminfo[rmcup] && -n $terminfo[cup] ]] || {
+    print -u2 -r -- 'Theme browser requires a terminal with alternate-screen support.'
+    return 1
+  }
+  exec {tty}<>/dev/tty || return 1
+  saved=$(command stty -g <&$tty) || return 1
+  names=("${(@f)$(_omz_theme_names)}")
+  names=("${(@)names:#}")
+  trap 'cancelled=1' INT TERM HUP
+  trap 'dirty=1' WINCH
+
+  function _omz_browser_stop {
+    if (( active )); then
+      [[ $pgid == <2-> ]] && kill -HUP -- -$pgid 2>/dev/null
+      # Let the preview supervisor clean up its nested worker group first.
+      local -i wait_count=0
+      while zpty -t "$pty" && (( wait_count++ < 100 )); do
+        zselect -t 1
+      done
+      zpty -d "$pty" 2>/dev/null
+      active=0
+    fi
+  }
+
+  function _omz_browser_line {
+    local text=${1//$'\t'/    } formatted='' MATCH MBEGIN MEND
+    text=${text//\%/%%}
+    # Tell prompt truncation that SGR has zero display width. All other terminal
+    # controls have already been removed by the preview backend.
+    while [[ $text =~ $'\e\\[[0-9;:]*m' ]]; do
+      formatted+=${text[1,$(( MBEGIN - 1 ))]}"%{"$MATCH"%}"
+      text=${text[$(( MEND + 1 )),-1]}
+    done
+    formatted+=$text
+    echoti cup $row 0 >&$tty
+    print -Pn -u $tty -- "%${width}<..<${formatted}%<<%f%k%b"
+    (( row++ ))
+  }
+
+  {
+    zmodload zsh/zselect || return 1
+    command stty -echo -icanon min 0 time 0 <&$tty || return 1
+    print -rn -u $tty -- "$terminfo[smcup]$terminfo[civis]"
+    while (( ! cancelled )); do
+      size=(${=$(command stty size <&$tty)})
+      rows=${size[1]:-24} cols=${size[2]:-80}
+      if (( height != rows || width != cols - 1 )); then
+        height=$rows width=$(( cols - 1 )) dirty=1
+      fi
+      matches=()
+      for name in "${names[@]}"; do
+        [[ ${(L)name} == *${(L)filter}* ]] && matches+=("$name")
+      done
+      (( selected > $#matches )) && selected=$#matches
+      (( selected < 1 )) && selected=1
+      name=${matches[$selected]}
+      if [[ $name != "$previous" ]]; then
+        _omz_browser_stop
+        previous=$name preview='' dirty=1
+        render_after=$(( EPOCHREALTIME + 0.12 ))
+      fi
+      # Coalesce typing and key repeats rather than starting a worker per key.
+      if (( ! active && EPOCHREALTIME >= render_after )); then
+        if [[ -n $name ]]; then
+          # zpty joins arguments as shell text; quote the literal theme name.
+          zpty -b "$pty" _omz_theme_preview "${(q)name}" || return 1
+          active=1
+          pgid=''
+          for record in "${(@f)$(zpty)}"; do
+            [[ $record == \(<->\)\ "$pty":* ]] && pgid=${${record#\(}%%\)*}
+          done
+        fi
+      fi
+      if (( active )); then
+        while zpty -r -t "$pty" chunk; do
+          preview+=${chunk//$'\r'/}
+          dirty=1
+        done
+      fi
+      page=$(( height > 24 ? 8 : 4 ))
+      if (( dirty )); then
+        print -rn -u $tty -- "$terminfo[clear]"
+        row=0
+        if (( width < 39 || height < 16 )); then
+          _omz_browser_line 'Resize to at least 40 columns x 16 rows.'
+          _omz_browser_line 'Esc / Ctrl-C: cancel'
+        else
+          _omz_browser_line 'Oh My Zsh theme browser | Esc / Ctrl-C: cancel'
+          _omz_browser_line "Filter: ${(V)filter}  ($#matches themes)"
+          if [[ $mode == actions ]]; then
+            _omz_browser_line '[u] Use in session  [s] Save + reload  [b] Back'
+            _omz_browser_line 'Use keeps old theme hooks. Save edits .zshrc + reloads.'
+          else
+            _omz_browser_line 'Arrows / Ctrl-P,N: move | PgUp,Dn | Enter: actions'
+            _omz_browser_line 'Type to filter | Backspace: delete | Ctrl-U: clear'
+          fi
+          for (( i = ((selected - 1) / page) * page + 1; i <= $#matches && row < page + 4; i++ )); do
+            if (( i == selected )); then
+              _omz_browser_line "> ${(V)matches[$i]}"
+            else
+              _omz_browser_line "  ${(V)matches[$i]}"
+            fi
+          done
+          _omz_browser_line '--- Static preview (right prompt shown separately) ---'
+          lines=("${(@f)preview}")
+          if [[ -z $preview ]]; then
+            [[ -n $name ]] && lines=('Rendering...') || lines=('No matching themes.')
+          fi
+          for chunk in "${lines[@]}"; do
+            (( row < height - 1 )) || break
+            _omz_browser_line "$chunk"
+          done
+        fi
+        dirty=0
+      fi
+      key=''
+      read -r -k 1 -t 0.1 -u $tty key || continue
+      if [[ $key == $'\e' ]]; then
+        suffix=''
+        while read -r -k 1 -t 0.03 -u $tty chunk; do
+          suffix+=$chunk
+          [[ $chunk == [A-Za-z~] || ${#suffix} -ge 8 ]] && break
+        done
+        [[ -n $suffix ]] || break
+        key=$'\e'$suffix
+      fi
+      [[ $key == $'\x03' ]] && break
+      if [[ $mode == actions ]]; then
+        case $key in
+          u) action=use; break ;;
+          s) action=set; break ;;
+          b|$'\r'|$'\n') mode=browse ;;
+        esac
+      else
+        case $key in
+          $'\e[A'|$'\eOA'|$'\x10') (( selected-- )) ;;
+          $'\e[B'|$'\eOB'|$'\x0e') (( selected++ )) ;;
+          $'\e[5~') (( selected -= page )) ;;
+          $'\e[6~') (( selected += page )) ;;
+          $'\x7f'|$'\b') filter=${filter[1,-2]}; selected=1 ;;
+          $'\x15') filter=''; selected=1 ;;
+          $'\r'|$'\n') [[ -n $name ]] && mode=actions ;;
+          [[:print:]]) filter+=$key; selected=1 ;;
+        esac
+      fi
+      dirty=1
+    done
+  } always {
+    _omz_browser_stop
+    print -rn -u $tty -- $'\e[0m'"$terminfo[cnorm]$terminfo[rmcup]"
+    command stty "$saved" <&$tty
+    exec {tty}>&-
+  }
+  (( cancelled )) && return 130
+  [[ -n $action ]] && print -rl -- "$action" "$name"
+  return 0
+)
diff --git a/tools/theme-preview-worker.zsh b/tools/theme-preview-worker.zsh
new file mode 100644
index 000000000..b0db83092
--- /dev/null
+++ b/tools/theme-preview-worker.zsh
@@ -0,0 +1,88 @@
+# Invoked only by theme-preview.zsh in a fresh zsh -df process. Themes and hooks
+# are intentionally sourced/run at top level (not inside a setup function).
+emulate -R zsh
+if [[ $1 == --supervise ]]; then
+  # This process is the private PTY's session leader. Keep the actual worker's
+  # standard descriptors non-TTY, and report its status outside theme state.
+  typeset -r _omz_preview_tmp=$2
+  shift 2
+  unsetopt monitor
+  command "$commands[zsh]" -df "${0:A}" "$@" \
+    < /dev/null > "$_omz_preview_tmp/output" 2>&1
+  print -r -- $? > "$_omz_preview_tmp/result"
+  exit
+fi
+typeset -r _omz_preview_root=$1 _omz_preview_theme=$2 _omz_preview_status=$3
+export ZSH=${ZSH:-$_omz_preview_root}
+ZSH_THEME=$4
+ZSH_CUSTOM=$5
+fpath=("$_omz_preview_root/functions" $fpath)
+autoload -Uz colors add-zsh-hook vcs_info
+colors
+setopt prompt_subst prompt_percent
+zstyle ':omz:alpha:lib:git' async-prompt no
+ZSH_THEME_GIT_PROMPT_PREFIX='git:('
+ZSH_THEME_GIT_PROMPT_SUFFIX=')'
+ZSH_THEME_GIT_PROMPT_DIRTY='*'
+ZSH_THEME_GIT_PROMPT_CLEAN=''
+ZSH_THEME_RUBY_PROMPT_PREFIX='('
+ZSH_THEME_RUBY_PROMPT_SUFFIX=')'
+source "$_omz_preview_root/lib/git.zsh"
+source "$_omz_preview_root/lib/vcs_info.zsh"
+source "$_omz_preview_root/lib/bzr.zsh"
+source "$_omz_preview_root/lib/nvm.zsh"
+source "$_omz_preview_root/lib/prompt_info_functions.zsh"
+source "$_omz_preview_root/lib/spectrum.zsh"
+# Check syntax before accepting a final false conditional as a successful load.
+# This subprocess shares the worker's execution deadline and process group.
+command "$commands[zsh]" -dfn "$_omz_preview_theme" || {
+  print -u2 -r -- 'theme preview: theme syntax check failed'
+  exit 1
+}
+# Keep zsh's PROMPT/PS1 and RPROMPT/RPS1 aliases intact (dieter sets RPS1).
+PROMPT=''
+RPROMPT=''
+source "$_omz_preview_theme"
+typeset -i _omz_preview_load_status=$?
+# Status 1 may just be a final conditional; require an initialized prompt below.
+# Higher statuses include syntax/runtime errors and missing commands.
+if (( _omz_preview_load_status > 1 )); then
+  print -u2 -r -- "theme preview: theme could not be loaded (exit $_omz_preview_load_status)"
+  exit 1
+fi
+
+function _omz_preview_set_status { return "$_omz_preview_status" }
+typeset -i _omz_preview_hook_status=0
+if (( $+functions[precmd] )); then
+  _omz_preview_set_status
+  precmd
+  _omz_preview_hook_status=$?
+  if (( _omz_preview_hook_status )); then
+    print -u2 -r -- "theme preview: precmd failed (exit $_omz_preview_hook_status); remaining hooks skipped"
+  fi
+fi
+for _omz_preview_hook in "${precmd_functions[@]}"; do
+  (( _omz_preview_hook_status )) && break
+  if (( $+functions[$_omz_preview_hook] )); then
+    _omz_preview_set_status
+    "$_omz_preview_hook"
+    _omz_preview_hook_status=$?
+    if (( _omz_preview_hook_status )); then
+      print -u2 -r -- "theme preview: precmd hook $_omz_preview_hook failed (exit $_omz_preview_hook_status); remaining hooks skipped"
+    fi
+  fi
+done
+if (( _omz_preview_load_status )) && [[ -z $PROMPT && -z $RPROMPT ]]; then
+  print -u2 -r -- "theme preview: theme did not initialize a prompt (load exit $_omz_preview_load_status)"
+  exit 1
+fi
+# Native prompt expansion handles PROMPT_SUBST once, followed by percent escapes.
+# An explicit (e) pass here would re-execute literal substitutions from helpers.
+print -r -- "Left prompt (status $_omz_preview_status):"
+_omz_preview_set_status
+print -Pr -- "${PROMPT-}"
+print -r -- 'Right prompt (shown separately):'
+_omz_preview_set_status
+print -Pr -- "${RPROMPT-}"
+(( _omz_preview_hook_status )) && exit 1
+exit 42
diff --git a/tools/theme-preview.zsh b/tools/theme-preview.zsh
new file mode 100644
index 000000000..91a6dd05f
--- /dev/null
+++ b/tools/theme-preview.zsh
@@ -0,0 +1,217 @@
+# Static previews execute theme code as the current user, not in a sandbox.
+# A private PTY supplies a process group without requiring shell job control.
+typeset -g _OMZ_THEME_PREVIEW_DIR=${${(%):-%x}:A:h}
+
+function _omz_theme_names() (
+  emulate -L zsh
+  setopt extendedglob
+  local root=${ZSH:-${_OMZ_THEME_PREVIEW_DIR:h}}
+  local custom=${ZSH_CUSTOM:-$root/custom} dir file name
+  local -a names files
+  for dir in "$custom" "$root/themes"; do
+    if [[ $dir == "$custom" ]]; then
+      files=("$dir"/**/*.zsh-theme(N-.))
+    else
+      files=("$dir"/*.zsh-theme(N-.))
+    fi
+    for file in "${files[@]}"; do
+      name=${${file#"$dir/"}%.zsh-theme}
+      [[ $dir == "$custom" ]] && name=${name#themes/}
+      [[ -n $name && $name != random && /$name/ != */(.|..)/* && $name != /* && $name != *[[:cntrl:]\\]* ]] || continue
+      names+=("$name")
+    done
+  done
+  (( $#names )) && print -rl -- ${(ou)names}
+  return 0
+)
+
+function _omz_theme_resolve() (
+  emulate -L zsh
+  setopt extendedglob
+  local name=$1 root=${ZSH:-${_OMZ_THEME_PREVIEW_DIR:h}}
+  local custom=${ZSH_CUSTOM:-$root/custom} dir
+  if (( $# != 1 )) || [[ -z $name || $name == random || /$name/ == */(.|..)/* || $name == /* || $name == *//* || $name == *[[:cntrl:]\\]* ]]; then
+    print -u2 -r -- 'theme preview: invalid or non-selectable theme name'
+    return 2
+  fi
+  for dir in "$custom" "$custom/themes" "$root/themes"; do
+    if [[ -f "$dir/$name.zsh-theme" ]]; then
+      print -r -- "${dir:A}/$name.zsh-theme"
+      return 0
+    fi
+  done
+  print -u2 -r -- 'theme preview: theme not found'
+  return 1
+)
+
+# One sample, with the requested exit status (0 by default). All execution and
+# state changes are confined to this subshell and the fresh -df worker.
+# For asynchronous callers, cancel the job group, not just zsh's waiting wrapper.
+function _omz_theme_preview() (
+  emulate -L zsh
+  local theme sample=${2:-0} backend=$_OMZ_THEME_PREVIEW_DIR
+  if (( $# < 1 || $# > 2 )) || [[ $sample != <0-255> ]]; then
+    print -u2 -r -- 'theme preview: usage: _omz_theme_preview name [status 0..255]'
+    return 2
+  fi
+  theme=$(_omz_theme_resolve "$1") || return $?
+  if ! zmodload zsh/zpty || ! zmodload zsh/system || ! zmodload zsh/datetime || ! zmodload zsh/zselect; then
+    print -u2 -r -- 'theme preview: required zsh modules unavailable (zpty, system, datetime, zselect)'
+    return 1
+  fi
+  local tmp fifo_fd pty=omz-preview-$sysparams[pid] record pgid raw='' chunk error=''
+  local selected=$1 custom=${ZSH_CUSTOM:-${ZSH:-$backend:h}/custom}
+  local -i active=0 cancelled=0 bytes=0 count remaining result=1
+  local -F deadline
+  trap 'cancelled=130' INT
+  trap 'cancelled=143' TERM
+  trap 'cancelled=129' HUP
+  {
+    tmp=$(command mktemp -d "${TMPDIR:-/tmp}/omz-preview.XXXXXXXX") || return 1
+    command mkfifo "$tmp/output" || return 1
+    sysopen -r -o nonblock,cloexec -u fifo_fd "$tmp/output" || return 1
+
+    # Exec immediately: a forked shell function could run inherited EXIT traps
+    # after returning. Both the launcher and theme worker must start fresh.
+    local -a launch=("$commands[zsh]" -df "$backend/theme-preview-worker.zsh" --supervise
+      "$tmp" "$backend:h" "$theme" "$sample" "$selected" "$custom")
+    deadline=$(( EPOCHREALTIME + 3 ))
+    if ! zpty -b "$pty" exec "${(@q)launch}"; then
+      print -u2 -r -- 'theme preview: could not allocate a private PTY'
+      return 1
+    fi
+    active=1
+    # The builtin listing supplies the session leader even before the child
+    # starts; this avoids a PID-handshake race during immediate cancellation.
+    for record in "${(@f)$(zpty)}"; do
+      if [[ $record == \(<->\)\ "$pty":* ]]; then
+        pgid=${${record#\(}%%\)*}
+        break
+      fi
+    done
+    if [[ $pgid != <2-> ]]; then
+      print -u2 -r -- 'theme preview: could not identify worker process group'
+      return 1
+    fi
+    while true; do
+      if (( cancelled )); then
+        error='cancelled'
+        break
+      fi
+      if (( EPOCHREALTIME >= deadline )); then
+        error='timed out after 3 seconds'
+        break
+      fi
+      remaining=$(( 32001 - bytes ))
+      if sysread -i "$fifo_fd" -s $(( remaining < 4096 ? remaining : 4096 )) -t 0.02 -c count chunk; then
+        raw+=$chunk
+        (( bytes += count ))
+        if (( bytes > 32000 )); then
+          error='output exceeded 32 KiB'
+          break
+        fi
+      elif [[ -s "$tmp/result" ]]; then
+        result=$(<"$tmp/result")
+        # The worker's dedicated completion status distinguishes a theme's
+        # early exit (including exit 0) from rendering both prompts.
+        [[ $result == 42 ]] || error="worker did not complete preview (exit $result)"
+        break
+      elif ! zpty -t "$pty"; then
+        error='worker supervisor exited before completing preview'
+        break
+      else
+        zselect -t 1
+      fi
+    done
+  } always {
+    # Clean up the whole group even on success. Deliberately detached processes
+    # are outside this boundary. Delete only our PTY, not any inherited ones.
+    if [[ $pgid == <2-> ]]; then
+      kill -TERM -- -$pgid 2>/dev/null
+      zselect -t 5
+      kill -KILL -- -$pgid 2>/dev/null
+    fi
+    (( active )) && zpty -d "$pty" 2>/dev/null
+    [[ -n $fifo_fd ]] && exec {fifo_fd}<&-
+    [[ -n $tmp ]] && command rm -rf -- "$tmp"
+  }
+
+  # Bound by bytes before splitting into locale-aware characters. No escape is
+  # emitted until it is a complete numeric SGR; all string controls are dropped,
+  # including their payloads and incomplete sequences at the output boundary.
+  unsetopt multibyte
+  raw=${raw[1,32000]}
+  setopt multibyte
+  local char safe='' state=text sgr=''
+  local -i code valid=1
+  for char in "${(@s::)raw}"; do
+    if (( cancelled )); then
+      error='cancelled'
+      break
+    fi
+    printf -v code '%d' "'$char" 2>/dev/null
+    case $state in
+      string|string-escape)
+        if [[ $char == $'\a' || $char == $'\xc2\x9c' || $char == $'\x9c' || ( $state == string-escape && $char == \\ ) ]]; then
+          state=text
+        elif [[ $char == $'\e' ]]; then
+          state=string-escape
+        else
+          state=string
+        fi
+        ;;
+      escape)
+        case $char in
+          '[') state=csi; sgr=''; valid=1 ;;
+          ']'|P|X|'^'|_) state=string ;;
+          $'\e') ;;
+          *)
+            if (( code >= 32 && code <= 47 )); then
+              state=intermediate
+            else
+              state=text
+            fi
+            ;;
+        esac
+        ;;
+      intermediate)
+        (( code >= 32 && code <= 47 )) || state=text
+        ;;
+      csi)
+        if [[ $char == [0-9\;:] ]]; then
+          sgr+=$char
+        elif (( code >= 64 && code <= 126 )); then
+          [[ $char == m && $valid == 1 ]] && safe+=$'\e['${sgr}m
+          state=text
+        elif [[ $char == $'\e' ]]; then
+          state=escape
+        else
+          valid=0
+        fi
+        ;;
+      text)
+        case $char in
+          $'\e') state=escape ;;
+          $'\xc2\x9b') state=csi; sgr=''; valid=1 ;;
+          # Drop raw 8-bit CSI instead of expanding it to two bytes. Filtering
+          # can then never enlarge the byte-bounded input buffer.
+          $'\x9b') state=csi; sgr=''; valid=0 ;;
+          $'\xc2\x90'|$'\xc2\x98'|$'\xc2\x9d'|$'\xc2\x9e'|$'\xc2\x9f'|$'\x90'|$'\x98'|$'\x9d'|$'\x9e'|$'\x9f') state=string ;;
+          $'\n'|$'\t') safe+=$char ;;
+          *)
+            # Reject format/directional controls even on libc implementations
+            # that classify them as printable. Keep private-use font glyphs.
+            if [[ $char == [[:print:]] ]] && ! (( code >= 0x200b && code <= 0x200f || code >= 0x2028 && code <= 0x202e || code >= 0x2060 && code <= 0x206f || code == 0xfeff )); then
+              safe+=$char
+            fi
+            ;;
+        esac
+        ;;
+    esac
+  done
+  (( cancelled )) && error='cancelled'
+  print -rn -- "$safe"$'\e[0m\n'
+  [[ -n $error ]] && print -u2 -r -- "theme preview: $error"
+  (( cancelled )) && return $cancelled
+  [[ -z $error ]]
+)