diff --git a/README.md b/README.md
index e1b7e448ef..6c12b28096 100644
--- a/README.md
+++ b/README.md
@@ -79,8 +79,9 @@ irm https://unsloth.ai/install.ps1 | iex
 
 #### Launch
 ```bash
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
+> For cloud VMs or LAN access, add `-H 0.0.0.0` to bind on all interfaces.
 
 #### Update
 To update, use the same install commands as above. Or run (does not work on Windows):
@@ -167,7 +168,7 @@ The below advanced instructions are for Unsloth Studio. For Unsloth Core advance
 git clone https://github.com/unslothai/unsloth
 cd unsloth
 ./install.sh --local
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 Then to update :
 ```bash
@@ -180,7 +181,7 @@ git clone https://github.com/unslothai/unsloth.git
 cd unsloth
 Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass
 .\install.ps1 --local
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 Then to update :
 ```bash
@@ -193,11 +194,11 @@ git clone https://github.com/unslothai/unsloth
 cd unsloth
 git checkout nightly
 ./install.sh --local
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 Then to launch every time:
 ```bash
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 
 #### Nightly: Windows:
@@ -208,11 +209,11 @@ cd unsloth
 git checkout nightly
 Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass
 .\install.ps1 --local
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 Then to launch every time:
 ```bash
-unsloth studio -H 0.0.0.0 -p 8888
+unsloth studio -p 8888
 ```
 
 #### Uninstall
diff --git a/install.ps1 b/install.ps1
index ab43bcdc52..7dc5a50250 100644
--- a/install.ps1
+++ b/install.ps1
@@ -552,7 +552,7 @@ try {
         } catch {}
         exit 1
     }
-    `$studioCommand = '& "' + `$studioExe + '" studio -H 0.0.0.0 -p ' + `$launchPort
+    `$studioCommand = '& "' + `$studioExe + '" studio -p ' + `$launchPort
     `$launchArgs = @(
         '-NoExit',
         '-NoProfile',
@@ -1344,15 +1344,25 @@ shell.Run cmd, 0, False
 
     New-StudioShortcuts -UnslothExePath $UnslothExe
 
-    # Launch studio automatically in interactive terminals;
-    # in non-interactive environments (CI, Docker) just print instructions.
+    # In interactive terminals, ask the user before starting Studio.
+    # In non-interactive environments (CI, Docker) just print instructions.
     $IsInteractive = [Environment]::UserInteractive -and (-not [Console]::IsInputRedirected)
     if ($IsInteractive) {
-        & $UnslothExe studio -H 0.0.0.0 -p 8888
+        Write-Host ""
+        $reply = Read-Host "  Start Unsloth Studio now? [Y/n]"
+        if ([string]::IsNullOrWhiteSpace($reply) -or $reply -match '^[Yy]') {
+            & $UnslothExe studio -p 8888
+        } else {
+            step "launch" "to start later, run:"
+            substep "unsloth studio -p 8888"
+            substep "(add -H 0.0.0.0 to allow network / cloud access)"
+            Write-Host ""
+        }
     } else {
         step "launch" "manual commands:"
         substep "& `"$VenvDir\Scripts\Activate.ps1`""
-        substep "unsloth studio -H 0.0.0.0 -p 8888"
+        substep "unsloth studio -p 8888"
+        substep "(add -H 0.0.0.0 to allow network / cloud access)"
         Write-Host ""
     }
 }
diff --git a/install.sh b/install.sh
index 4f17ea80cb..7948170043 100755
--- a/install.sh
+++ b/install.sh
@@ -622,11 +622,11 @@ if [ -t 1 ]; then
     ) &
     # Clear traps so exec does not trigger _release_lock (the subshell owns it)
     trap - EXIT INT TERM
-    exec "$UNSLOTH_EXE" studio -H 0.0.0.0 -p "$_launch_port"
+    exec "$UNSLOTH_EXE" studio -p "$_launch_port"
 else
     # ── Background mode (no TTY) ──
     # Used by macOS .app and headless invocations.
-    _launch_cmd=$(printf '%q ' "$UNSLOTH_EXE" studio -H 0.0.0.0 -p "$_launch_port")
+    _launch_cmd=$(printf '%q ' "$UNSLOTH_EXE" studio -p "$_launch_port")
     _launch_cmd=${_launch_cmd% }
     _spawn_terminal "$_launch_cmd"
 
@@ -1847,28 +1847,46 @@ printf "  ${C_TITLE}%s${C_RST}\n" "Unsloth Studio installed!"
 printf "  ${C_DIM}%s${C_RST}\n" "$RULE"
 echo ""
 
-# Launch studio automatically in interactive terminals;
-# in non-interactive environments (Docker, CI, cloud-init) just print instructions.
+# In interactive terminals, ask the user before starting Studio.
+# In non-interactive environments (Docker, CI, cloud-init) just print instructions.
 if [ -t 1 ]; then
-    step "launch" "starting Unsloth Studio..."
-    "$VENV_DIR/bin/unsloth" studio -H 0.0.0.0 -p 8888
-    _LAUNCH_EXIT=$?
-    if [ "$_LAUNCH_EXIT" -ne 0 ] && [ "$_MIGRATED" = true ]; then
-        echo ""
-        echo "⚠️  Unsloth Studio failed to start after migration."
-        echo "   Your migrated environment may be incompatible."
-        echo "   To fix, remove the environment and reinstall:"
-        echo ""
-        echo "   rm -rf $VENV_DIR"
-        echo "   curl -fsSL https://unsloth.ai/install.sh | sh"
-        echo ""
+    echo ""
+    printf "  Start Unsloth Studio now? [Y/n] "
+    if [ -r /dev/tty ]; then
+        read -r _reply </dev/tty || _reply="y"
+    else
+        _reply="y"
     fi
-    exit "$_LAUNCH_EXIT"
+    case "${_reply:-y}" in
+        [Yy]*|"")
+            step "launch" "starting Unsloth Studio..."
+            "$VENV_DIR/bin/unsloth" studio -p 8888
+            _LAUNCH_EXIT=$?
+            if [ "$_LAUNCH_EXIT" -ne 0 ] && [ "$_MIGRATED" = true ]; then
+                echo ""
+                echo "⚠️  Unsloth Studio failed to start after migration."
+                echo "   Your migrated environment may be incompatible."
+                echo "   To fix, remove the environment and reinstall:"
+                echo ""
+                echo "   rm -rf $VENV_DIR"
+                echo "   curl -fsSL https://unsloth.ai/install.sh | sh"
+                echo ""
+            fi
+            exit "$_LAUNCH_EXIT"
+            ;;
+        *)
+            step "launch" "to start later, run:"
+            substep "unsloth studio -p 8888"
+            substep "(add -H 0.0.0.0 to allow network / cloud access)"
+            echo ""
+            ;;
+    esac
 else
     step "launch" "manual commands:"
-    substep "unsloth studio -H 0.0.0.0 -p 8888"
+    substep "unsloth studio -p 8888"
     substep "or activate env first:"
     substep "source ${VENV_DIR}/bin/activate"
-    substep "unsloth studio -H 0.0.0.0 -p 8888"
+    substep "unsloth studio -p 8888"
+    substep "(add -H 0.0.0.0 to allow network / cloud access)"
     echo ""
 fi
diff --git a/studio/backend/run.py b/studio/backend/run.py
index 7590ef1067..c5b103ff70 100644
--- a/studio/backend/run.py
+++ b/studio/backend/run.py
@@ -244,7 +244,7 @@ def _graceful_shutdown(server = None):
 
 
 def run_server(
-    host: str = "0.0.0.0",
+    host: str = "127.0.0.1",
     port: int = 8888,
     frontend_path: Path = Path(__file__).resolve().parent.parent / "frontend" / "dist",
     silent: bool = False,
@@ -392,7 +392,11 @@ def _trigger_shutdown():
             pass
 
     parser = argparse.ArgumentParser(description = "Run Unsloth UI Backend server")
-    parser.add_argument("--host", default = "0.0.0.0", help = "Host to bind to")
+    parser.add_argument(
+        "--host",
+        default = "127.0.0.1",
+        help = "Host to bind to (default: 127.0.0.1; use 0.0.0.0 for network/cloud access)",
+    )
     parser.add_argument("--port", type = int, default = 8888, help = "Port to bind to")
     parser.add_argument(
         "--frontend",
diff --git a/studio/backend/tests/test_host_defaults.py b/studio/backend/tests/test_host_defaults.py
new file mode 100644
index 0000000000..8b81474e92
--- /dev/null
+++ b/studio/backend/tests/test_host_defaults.py
@@ -0,0 +1,98 @@
+# SPDX-License-Identifier: AGPL-3.0-only
+# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0
+
+"""Tests that Unsloth Studio defaults to 127.0.0.1 (loopback) not 0.0.0.0.
+
+Uses AST parsing to inspect source-level defaults without requiring the
+full studio venv (run.py has heavy dependencies like structlog/uvicorn).
+"""
+
+import ast
+from pathlib import Path
+
+_RUN_PY = Path(__file__).resolve().parent.parent / "run.py"
+
+
+def _parse_function_param_defaults(source: str, func_name: str) -> dict:
+    """Return {param_name: default_value} for a named function in *source*.
+
+    Only handles ast.Constant defaults (strings, ints, bools).
+    """
+    tree = ast.parse(source)
+    for node in ast.walk(tree):
+        if (
+            isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef))
+            and node.name == func_name
+        ):
+            result = {}
+            all_args = node.args.args
+            defaults = node.args.defaults
+            # Defaults are right-aligned against the args list
+            offset = len(all_args) - len(defaults)
+            for i, default in enumerate(defaults):
+                arg_name = all_args[offset + i].arg
+                if isinstance(default, ast.Constant):
+                    result[arg_name] = default.value
+            return result
+    return {}
+
+
+def _parse_argparse_add_argument_default(source: str, option_name: str):
+    """Return the 'default' kwarg value for add_argument(option_name, ...) in *source*.
+
+    Walks the entire module so the call can live in __main__ or in a helper
+    function — only handles ast.Constant defaults.
+    """
+    tree = ast.parse(source)
+    for node in ast.walk(tree):
+        if not isinstance(node, ast.Call):
+            continue
+        func = node.func
+        if not (isinstance(func, ast.Attribute) and func.attr == "add_argument"):
+            continue
+        if not node.args:
+            continue
+        first_arg = node.args[0]
+        if not (isinstance(first_arg, ast.Constant) and first_arg.value == option_name):
+            continue
+        for kw in node.keywords:
+            if kw.arg == "default" and isinstance(kw.value, ast.Constant):
+                return kw.value.value
+    return None
+
+
+def test_run_server_default_host_is_loopback():
+    """run_server() parameter default for 'host' must be 127.0.0.1, not 0.0.0.0.
+
+    Binding to 0.0.0.0 by default exposes the service on all network
+    interfaces, contradicting the documented "privacy first / 100% local"
+    guarantee.  Loopback (127.0.0.1) is the least-permissive default;
+    users who need network access can pass -H 0.0.0.0 explicitly.
+    """
+    source = _RUN_PY.read_text()
+    defaults = _parse_function_param_defaults(source, "run_server")
+    assert (
+        "host" in defaults
+    ), "run_server() must have a 'host' parameter with a default"
+    host_default = defaults["host"]
+    assert host_default == "127.0.0.1", (
+        f"run_server() host default must be '127.0.0.1' (loopback) "
+        f"but got '{host_default}'. Binding to '{host_default}' by default "
+        f"exposes the service beyond localhost."
+    )
+
+
+def test_argparse_default_host_is_loopback():
+    """argparse --host add_argument default must be 127.0.0.1.
+
+    When run.py is invoked directly (python run.py), the argparse default
+    should match the function default so direct execution is equally safe.
+    """
+    source = _RUN_PY.read_text()
+    host_default = _parse_argparse_add_argument_default(source, "--host")
+    assert (
+        host_default is not None
+    ), "Could not find add_argument('--host', ...) in run.py"
+    assert (
+        host_default == "127.0.0.1"
+    ), f"run.py argparse --host default must be '127.0.0.1', got '{host_default}'"
diff --git a/studio/setup.sh b/studio/setup.sh
index 39fb566f1b..3e875eed30 100755
--- a/studio/setup.sh
+++ b/studio/setup.sh
@@ -1087,10 +1087,11 @@ else
     fi
     printf "  ${C_DIM}%s${C_RST}\n" "$RULE"
     if [ "$_LLAMA_CPP_DEGRADED" = true ]; then
-        printf "  ${C_DIM}%-15s${C_WARN}%s${C_RST}\n" "launch" "unsloth studio -H 0.0.0.0 -p 8888"
+        printf "  ${C_DIM}%-15s${C_WARN}%s${C_RST}\n" "launch" "unsloth studio -p 8888"
     else
-        printf "  ${C_DIM}%-15s${C_OK}%s${C_RST}\n" "launch" "unsloth studio -H 0.0.0.0 -p 8888"
+        printf "  ${C_DIM}%-15s${C_OK}%s${C_RST}\n" "launch" "unsloth studio -p 8888"
     fi
+    printf "  ${C_DIM}%-15s%s${C_RST}\n" "" "(add -H 0.0.0.0 to allow network / cloud access)"
 fi
 echo ""
 
diff --git a/tests/sh/test_install_host_defaults.sh b/tests/sh/test_install_host_defaults.sh
new file mode 100755
index 0000000000..7b01eaa716
--- /dev/null
+++ b/tests/sh/test_install_host_defaults.sh
@@ -0,0 +1,104 @@
+#!/bin/bash
+# Static analysis: installer scripts and README must not hard-code 0.0.0.0
+# in any user-visible default launch command. The dynamic-port launcher
+# templates and post-install hints should rely on the new loopback default.
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+INSTALL_SH="$SCRIPT_DIR/../../install.sh"
+INSTALL_PS1="$SCRIPT_DIR/../../install.ps1"
+SETUP_SH="$SCRIPT_DIR/../../studio/setup.sh"
+README="$SCRIPT_DIR/../../README.md"
+PASS=0
+FAIL=0
+
+assert_contains() {
+    _label="$1"; _haystack="$2"; _needle="$3"
+    if echo "$_haystack" | grep -qF -- "$_needle"; then
+        echo "  PASS: $_label"
+        PASS=$((PASS + 1))
+    else
+        echo "  FAIL: $_label (expected to find '$_needle')"
+        FAIL=$((FAIL + 1))
+    fi
+}
+
+assert_not_contains() {
+    _label="$1"; _haystack="$2"; _needle="$3"
+    if echo "$_haystack" | grep -qF -- "$_needle"; then
+        echo "  FAIL: $_label (found '$_needle' but should not)"
+        FAIL=$((FAIL + 1))
+    else
+        echo "  PASS: $_label"
+        PASS=$((PASS + 1))
+    fi
+}
+
+echo ""
+echo "=== install.sh launcher template ==="
+
+# Extract the heredoc that generates ~/.local/share/unsloth/launch-studio.sh.
+_launcher=$(awk '/cat > "\$_css_launcher"/{found=1} found{print} /^LAUNCHER_EOF$/{found=0}' "$INSTALL_SH")
+assert_contains \
+    "launcher template: extraction found the heredoc content" \
+    "$_launcher" "#!/usr/bin/env bash"
+# The desktop launcher should rely on the new 127.0.0.1 default.
+assert_not_contains \
+    "launcher template: no hardcoded 'studio -H 0.0.0.0'" \
+    "$_launcher" "studio -H 0.0.0.0"
+
+echo ""
+echo "=== install.sh end-of-install block ==="
+
+_end=$(tail -50 "$INSTALL_SH")
+assert_contains \
+    "install.sh: interactive block prompts user (read)" \
+    "$_end" "read"
+assert_not_contains \
+    "install.sh: no 'studio -H 0.0.0.0' in end-of-install commands" \
+    "$_end" "studio -H 0.0.0.0"
+
+echo ""
+echo "=== install.ps1 end-of-install block ==="
+
+_ps1_end=$(tail -25 "$INSTALL_PS1")
+assert_contains \
+    "install.ps1: interactive block prompts user (Read-Host)" \
+    "$_ps1_end" "Read-Host"
+assert_not_contains \
+    "install.ps1: no 'studio -H 0.0.0.0' in end-of-install commands" \
+    "$_ps1_end" "studio -H 0.0.0.0"
+
+echo ""
+echo "=== studio/setup.sh launch hint ==="
+
+_setup_tail=$(tail -30 "$SETUP_SH")
+assert_not_contains \
+    "studio/setup.sh: launch hint has no '-H 0.0.0.0'" \
+    "$_setup_tail" "studio -H 0.0.0.0"
+
+echo ""
+echo "=== README.md Launch section ==="
+
+# The primary Launch example must not include -H 0.0.0.0; the LAN/cloud
+# note appears as an opt-in line outside the code block.
+_readme_launch=$(awk '/^#### Launch$/{found=1} found{print} /^#### Update$/{found=0}' "$README")
+assert_contains \
+    "README: Launch section exists" \
+    "$_readme_launch" "unsloth studio"
+assert_not_contains \
+    "README: Launch section primary command has no -H 0.0.0.0" \
+    "$_readme_launch" "studio -H 0.0.0.0"
+assert_contains \
+    "README: Launch section documents -H 0.0.0.0 opt-in" \
+    "$_readme_launch" "0.0.0.0"
+
+echo ""
+echo "=== Results ==="
+echo "  PASS: $PASS"
+echo "  FAIL: $FAIL"
+if [ "$FAIL" -gt 0 ]; then
+    echo "FAILED"
+    exit 1
+fi
+echo "ALL PASSED"
diff --git a/tests/studio/test_cli_studio_defaults.py b/tests/studio/test_cli_studio_defaults.py
new file mode 100644
index 0000000000..4d6f28f075
--- /dev/null
+++ b/tests/studio/test_cli_studio_defaults.py
@@ -0,0 +1,87 @@
+"""Tests that the 'unsloth studio' CLI defaults to 127.0.0.1.
+
+Uses AST parsing to inspect source-level defaults without requiring the
+full unsloth_cli dependencies (typer/pydantic) at test-collection time.
+"""
+
+import ast
+from pathlib import Path
+
+_STUDIO_CMD_PY = (
+    Path(__file__).resolve().parents[2] / "unsloth_cli" / "commands" / "studio.py"
+)
+
+
+def _find_typer_option_default(source: str, func_name: str, long_option: str):
+    """Return the default value of a typer.Option(...) parameter in *func_name*.
+
+    Matches by the long option name (e.g. '--host') among the positional args
+    of the typer.Option() call and returns the first positional arg (the
+    default value). Only handles ast.Constant defaults.
+    """
+    tree = ast.parse(source)
+    for func_node in ast.walk(tree):
+        if not isinstance(func_node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+            continue
+        if func_node.name != func_name:
+            continue
+        # Walk both regular args and kwonly args, each paired with its default.
+        all_args = func_node.args.args + func_node.args.kwonlyargs
+        all_defaults = func_node.args.defaults + [
+            d for d in func_node.args.kw_defaults if d is not None
+        ]
+        # ast pads defaults right-aligned against args (ignoring kwonly). We
+        # iterate calls directly, which is simpler and robust.
+        for default in all_defaults:
+            if not isinstance(default, ast.Call):
+                continue
+            call_func = default.func
+            is_typer_option = (
+                isinstance(call_func, ast.Attribute)
+                and call_func.attr == "Option"
+                and isinstance(call_func.value, ast.Name)
+                and call_func.value.id == "typer"
+            )
+            if not is_typer_option:
+                continue
+            # First positional is the default value; remaining positionals are
+            # option flags like "--host", "-H".
+            if not default.args:
+                continue
+            flags = [
+                a.value
+                for a in default.args[1:]
+                if isinstance(a, ast.Constant) and isinstance(a.value, str)
+            ]
+            if long_option not in flags:
+                continue
+            first = default.args[0]
+            if isinstance(first, ast.Constant):
+                return first.value
+    return None
+
+
+def test_studio_default_host_is_loopback():
+    """`unsloth studio` (studio_default) --host typer Option default must be 127.0.0.1."""
+    source = _STUDIO_CMD_PY.read_text()
+    host_default = _find_typer_option_default(source, "studio_default", "--host")
+    assert (
+        host_default is not None
+    ), "Could not find --host typer.Option default in studio_default()"
+    assert host_default == "127.0.0.1", (
+        f"studio_default() --host default must be '127.0.0.1' (loopback) "
+        f"but got '{host_default}'."
+    )
+
+
+def test_studio_run_host_is_loopback():
+    """`unsloth studio run` --host typer Option default must be 127.0.0.1."""
+    source = _STUDIO_CMD_PY.read_text()
+    host_default = _find_typer_option_default(source, "run", "--host")
+    assert (
+        host_default is not None
+    ), "Could not find --host typer.Option default in run()"
+    assert host_default == "127.0.0.1", (
+        f"`unsloth studio run` --host default must be '127.0.0.1' (loopback) "
+        f"but got '{host_default}'."
+    )
diff --git a/unsloth_cli/commands/studio.py b/unsloth_cli/commands/studio.py
index b74f42674d..ac25c8805d 100644
--- a/unsloth_cli/commands/studio.py
+++ b/unsloth_cli/commands/studio.py
@@ -414,7 +414,7 @@ def _load_model_via_http(
 def studio_default(
     ctx: typer.Context,
     port: int = typer.Option(8888, "--port", "-p"),
-    host: str = typer.Option("0.0.0.0", "--host", "-H"),
+    host: str = typer.Option("127.0.0.1", "--host", "-H"),
     frontend: Optional[Path] = typer.Option(None, "--frontend", "-f"),
     silent: bool = typer.Option(False, "--silent", "-q"),
     api_only: bool = typer.Option(
@@ -528,7 +528,7 @@ def run(
         "cli", "--api-key-name", help = "Label for the auto-generated API key"
     ),
     port: int = typer.Option(8888, "--port", "-p"),
-    host: str = typer.Option("0.0.0.0", "--host", "-H"),
+    host: str = typer.Option("127.0.0.1", "--host", "-H"),
     frontend: Optional[Path] = typer.Option(None, "--frontend", "-f"),
     silent: bool = typer.Option(False, "--silent", "-q"),
 ):