diff --git a/scripts/uninstall.ps1 b/scripts/uninstall.ps1
index 9b6e6ebb86..7fc5efab4c 100644
--- a/scripts/uninstall.ps1
+++ b/scripts/uninstall.ps1
@@ -3,8 +3,10 @@
 #
 # Unsloth Studio uninstaller for Windows PowerShell.
 # Stops running servers and removes install dir, launcher data, CLI shim,
-# desktop and Start Menu shortcuts, the user PATH entry, and the PathBackup
-# registry key. Honors custom roots set via UNSLOTH_STUDIO_HOME / STUDIO_HOME
+# desktop and Start Menu shortcuts, the user PATH entry, the PathBackup
+# registry key, and WebView2 runtime data keyed by the app bundle id
+# (EBWebView caches created at first desktop-app launch, not by install.ps1).
+# Honors custom roots set via UNSLOTH_STUDIO_HOME / STUDIO_HOME
 # at install time (read back from share\studio.conf).
 #
 # Usage:  irm https://raw.githubusercontent.com/unslothai/unsloth/main/scripts/uninstall.ps1 | iex
@@ -398,6 +400,32 @@ function Uninstall-UnslothStudio {
         _RemovePath $defaultUnslothHome
     }
 
+    # WebView2/app runtime data keyed by the Tauri bundle id. Created at first
+    # desktop-app launch, not by install.ps1. LOCALAPPDATA holds the EBWebView
+    # profile (a leftover copy serves a stale frontend to the next install);
+    # APPDATA holds the app config dir.
+    _Step "Removing WebView caches and app data (ai.unsloth.studio)..."
+    $bundleId = "ai.unsloth.studio"
+    $webviewDataDirs = @()
+    if ($env:LOCALAPPDATA) { $webviewDataDirs += Join-Path $env:LOCALAPPDATA $bundleId }
+    if ($env:APPDATA) { $webviewDataDirs += Join-Path $env:APPDATA $bundleId }
+    # Stop the desktop app and any msedgewebview2.exe helper using these dirs
+    # first; WebView2 keeps open handles that make the delete fail.
+    try { Stop-Process -Name "unsloth-studio" -Force -ErrorAction SilentlyContinue } catch { }
+    try {
+        foreach ($proc in (Get-CimInstance Win32_Process -Filter "Name = 'msedgewebview2.exe'" -ErrorAction SilentlyContinue)) {
+            $cl = $proc.CommandLine
+            if (-not $cl) { continue }
+            foreach ($d in $webviewDataDirs) {
+                if ($cl -ilike "*$d*") {
+                    try { Stop-Process -Id $proc.ProcessId -Force -ErrorAction SilentlyContinue } catch { }
+                    break
+                }
+            }
+        }
+    } catch { }
+    foreach ($d in $webviewDataDirs) { _RemovePath $d }
+
     # ── Remove desktop and Start Menu shortcuts ──
     _Step "Removing desktop and Start Menu shortcuts..."
     try {
diff --git a/scripts/uninstall.sh b/scripts/uninstall.sh
index 957d2b7af2..303b5225dc 100755
--- a/scripts/uninstall.sh
+++ b/scripts/uninstall.sh
@@ -4,7 +4,9 @@
 #
 # Unsloth Studio uninstaller (macOS / Linux / WSL).
 # Stops running servers and removes install dir, launcher data,
-# CLI shim, desktop shortcut, .app bundle, and Launch Services entry.
+# CLI shim, desktop shortcut, .app bundle, Launch Services entry, and
+# WebView runtime data keyed by the app bundle id (WebKit/webkit2gtk
+# caches created at first app launch, not by install.sh).
 # Honors custom roots set via UNSLOTH_STUDIO_HOME / STUDIO_HOME at
 # install time (read back from studio.conf).
 #
@@ -80,6 +82,13 @@ $_roots_from_conf"
             pkill -KILL -f "$_pat" 2>/dev/null || true
         done
     done
+
+    # Tauri desktop app (binary "unsloth-studio"): stop it so its WebView
+    # helpers can't hold or re-create the runtime caches removed below.
+    # -x is an exact name match, so the "unsloth" CLI shim is never touched.
+    pkill -TERM -x unsloth-studio 2>/dev/null || true
+    sleep 0.5
+    pkill -KILL -x unsloth-studio 2>/dev/null || true
 }
 
 _remove_path() {
@@ -261,6 +270,25 @@ case "$_os" in
         if [ -x "$_lsr" ]; then
             "$_lsr" -u "$HOME/Applications/Unsloth Studio.app" 2>/dev/null || true
         fi
+        # WebView/app runtime data keyed by the bundle id. Created by macOS +
+        # WKWebView at first app launch, not by install.sh, so it survives an
+        # uninstall and a leftover WebKit cache then serves a stale frontend
+        # to the next install.
+        _bid="ai.unsloth.studio"
+        echo "Removing WebView caches and app data ($_bid)..."
+        _remove_path "$HOME/Library/Caches/$_bid"
+        _remove_path "$HOME/Library/WebKit/$_bid"
+        _remove_path "$HOME/Library/Application Support/$_bid"
+        _remove_path "$HOME/Library/HTTPStorages/$_bid"
+        _remove_path "$HOME/Library/HTTPStorages/$_bid.binarycookies"
+        _remove_path "$HOME/Library/Cookies/$_bid.binarycookies"
+        _remove_path "$HOME/Library/Saved Application State/$_bid.savedState"
+        # Delete via defaults first: cfprefsd caches plists in memory and can
+        # re-write the file after a bare rm.
+        if command -v defaults >/dev/null 2>&1; then
+            defaults delete "$_bid" >/dev/null 2>&1 || true
+        fi
+        _remove_path "$HOME/Library/Preferences/$_bid.plist"
         ;;
     Linux)
         if [ "$_is_wsl" = "1" ]; then
@@ -403,6 +431,15 @@ case "$_os" in
                 echo "          sudo rm -rf /opt/rocm /opt/rocm-* && sudo ldconfig"
             fi
         fi
+        # WebView/app runtime data keyed by the Tauri bundle id. Created by
+        # webkit2gtk at first desktop-app launch, not by install.sh; a
+        # leftover cache serves a stale frontend to the next install.
+        _bid="ai.unsloth.studio"
+        echo "Removing WebView caches and app data ($_bid)..."
+        _remove_path "${XDG_CACHE_HOME:-$HOME/.cache}/$_bid"
+        _remove_path "${XDG_DATA_HOME:-$HOME/.local/share}/$_bid"
+        _remove_path "${XDG_CONFIG_HOME:-$HOME/.config}/$_bid"
+        _remove_path "${XDG_STATE_HOME:-$HOME/.local/state}/$_bid"
         echo "Removing Linux .desktop entry..."
         _remove_path "$HOME/.local/share/applications/unsloth-studio.desktop"
         if command -v update-desktop-database >/dev/null 2>&1; then
diff --git a/tests/run_all.sh b/tests/run_all.sh
index eaa726f73c..bb62582c61 100755
--- a/tests/run_all.sh
+++ b/tests/run_all.sh
@@ -14,6 +14,7 @@ sh "$TESTS_DIR/sh/test_nvcc_meets_llama_minimum.sh"
 sh "$TESTS_DIR/sh/test_resolve_cuda_archs.sh"
 sh "$TESTS_DIR/sh/test_strixhalo_wsl_reroute.sh"
 sh "$TESTS_DIR/sh/test_uninstall_shared_icon.sh"
+sh "$TESTS_DIR/sh/test_uninstall_webview_data.sh"
 sh "$TESTS_DIR/sh/test_torch_flavor.sh"
 sh "$TESTS_DIR/sh/test_redact_install_output.sh"
 sh "$TESTS_DIR/sh/test_install_uv_override_space.sh"
diff --git a/tests/sh/test_uninstall_webview_data.sh b/tests/sh/test_uninstall_webview_data.sh
new file mode 100755
index 0000000000..14898c05c2
--- /dev/null
+++ b/tests/sh/test_uninstall_webview_data.sh
@@ -0,0 +1,106 @@
+#!/bin/bash
+# SPDX-License-Identifier: AGPL-3.0-only
+# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0
+# Regression tests for WebView runtime-data cleanup in scripts/uninstall.sh.
+#
+# WKWebView (macOS) and webkit2gtk (Linux) create data keyed by the bundle id
+# at first app launch, not at install time, so the uninstaller used to miss it
+# and a leftover cache served a stale frontend to the next install. Runs the
+# full script against a fixture HOME (pkill/defaults stubbed via PATH, OS
+# branch picked by a stubbed uname) and asserts bundle-id paths are removed
+# while unrelated app data survives.
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+UNINSTALL_SH="$SCRIPT_DIR/../../scripts/uninstall.sh"
+BID="ai.unsloth.studio"
+PASS=0
+FAIL=0
+
+_TMP_ROOT=$(mktemp -d)
+trap 'rm -rf "$_TMP_ROOT"' EXIT
+
+assert_gone()    { _l="$1"; if [ -e "$2" ]; then echo "  FAIL: $_l (still present: $2)"; FAIL=$((FAIL+1)); else echo "  PASS: $_l"; PASS=$((PASS+1)); fi; }
+assert_present() { _l="$1"; if [ -e "$2" ]; then echo "  PASS: $_l"; PASS=$((PASS+1)); else echo "  FAIL: $_l (missing: $2)"; FAIL=$((FAIL+1)); fi; }
+
+# Stub out process kills and macOS pref/LaunchServices tools so the script can
+# run against a fixture HOME without touching the real system.
+STUB_BIN="$_TMP_ROOT/stubbin"
+mkdir -p "$STUB_BIN"
+for _tool in pkill defaults; do
+    printf '#!/bin/sh\nexit 0\n' > "$STUB_BIN/$_tool"
+    chmod +x "$STUB_BIN/$_tool"
+done
+
+# run_uninstall <home> <uname_output> : run the full script with a stubbed OS.
+run_uninstall() {
+    printf '#!/bin/sh\necho %s\n' "$2" > "$STUB_BIN/uname"
+    chmod +x "$STUB_BIN/uname"
+    env -u UNSLOTH_STUDIO_HOME -u STUDIO_HOME \
+        -u XDG_CACHE_HOME -u XDG_DATA_HOME -u XDG_CONFIG_HOME -u XDG_STATE_HOME \
+        HOME="$1" PATH="$STUB_BIN:$PATH" sh "$UNINSTALL_SH" >/dev/null 2>&1
+}
+
+# ── 1. macOS: every bundle-id-keyed ~/Library path is removed ──
+H=$(mktemp -d -p "$_TMP_ROOT")
+mkdir -p "$H/Library/Caches/$BID/WebKit/NetworkCache" \
+         "$H/Library/WebKit/$BID/WebsiteData/CacheStorage" \
+         "$H/Library/Application Support/$BID" \
+         "$H/Library/HTTPStorages/$BID" \
+         "$H/Library/Saved Application State/$BID.savedState" \
+         "$H/Library/Preferences" \
+         "$H/Library/Cookies" \
+         "$H/Library/Caches/com.other.app"
+: > "$H/Library/HTTPStorages/$BID.binarycookies"
+: > "$H/Library/Cookies/$BID.binarycookies"
+: > "$H/Library/Preferences/$BID.plist"
+: > "$H/Library/Caches/$BID/stale-frontend.js"
+: > "$H/Library/Caches/com.other.app/keepme"
+run_uninstall "$H" Darwin
+assert_gone "macOS: Caches/$BID removed"                     "$H/Library/Caches/$BID"
+assert_gone "macOS: WebKit/$BID removed"                     "$H/Library/WebKit/$BID"
+assert_gone "macOS: Application Support/$BID removed"        "$H/Library/Application Support/$BID"
+assert_gone "macOS: HTTPStorages/$BID removed"               "$H/Library/HTTPStorages/$BID"
+assert_gone "macOS: HTTPStorages/$BID.binarycookies removed" "$H/Library/HTTPStorages/$BID.binarycookies"
+assert_gone "macOS: Cookies/$BID.binarycookies removed"      "$H/Library/Cookies/$BID.binarycookies"
+assert_gone "macOS: Saved Application State removed"         "$H/Library/Saved Application State/$BID.savedState"
+assert_gone "macOS: Preferences/$BID.plist removed"          "$H/Library/Preferences/$BID.plist"
+assert_present "macOS: unrelated app cache kept"             "$H/Library/Caches/com.other.app/keepme"
+
+# ── 2. Linux: bundle-id-keyed XDG default paths are removed ──
+H=$(mktemp -d -p "$_TMP_ROOT")
+mkdir -p "$H/.cache/$BID" "$H/.local/share/$BID" "$H/.config/$BID" \
+         "$H/.local/state/$BID" "$H/.cache/other.app"
+run_uninstall "$H" Linux
+assert_gone "linux: ~/.cache/$BID removed"       "$H/.cache/$BID"
+assert_gone "linux: ~/.local/share/$BID removed" "$H/.local/share/$BID"
+assert_gone "linux: ~/.config/$BID removed"      "$H/.config/$BID"
+assert_gone "linux: ~/.local/state/$BID removed" "$H/.local/state/$BID"
+assert_present "linux: unrelated app cache kept" "$H/.cache/other.app"
+
+# ── 3. Linux: XDG_*_HOME overrides are honored ──
+H=$(mktemp -d -p "$_TMP_ROOT")
+XDG=$(mktemp -d -p "$_TMP_ROOT")
+mkdir -p "$XDG/cache/$BID" "$XDG/data/$BID" "$XDG/config/$BID" "$XDG/state/$BID"
+printf '#!/bin/sh\necho Linux\n' > "$STUB_BIN/uname"
+chmod +x "$STUB_BIN/uname"
+env -u UNSLOTH_STUDIO_HOME -u STUDIO_HOME \
+    XDG_CACHE_HOME="$XDG/cache" XDG_DATA_HOME="$XDG/data" \
+    XDG_CONFIG_HOME="$XDG/config" XDG_STATE_HOME="$XDG/state" \
+    HOME="$H" PATH="$STUB_BIN:$PATH" sh "$UNINSTALL_SH" >/dev/null 2>&1
+assert_gone "linux: XDG_CACHE_HOME override honored"  "$XDG/cache/$BID"
+assert_gone "linux: XDG_DATA_HOME override honored"   "$XDG/data/$BID"
+assert_gone "linux: XDG_CONFIG_HOME override honored" "$XDG/config/$BID"
+assert_gone "linux: XDG_STATE_HOME override honored"  "$XDG/state/$BID"
+
+# ── 4. Nothing to remove is a clean no-op (fresh HOME, exit 0) ──
+H=$(mktemp -d -p "$_TMP_ROOT")
+if run_uninstall "$H" Darwin; then
+    echo "  PASS: empty HOME -> no-op exit 0"; PASS=$((PASS+1))
+else
+    echo "  FAIL: empty HOME -> nonzero exit"; FAIL=$((FAIL+1))
+fi
+
+echo ""
+echo "Results: $PASS passed, $FAIL failed"
+[ "$FAIL" = 0 ]