diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4615cc7..970ebd9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.37.1] - 2026-05-22
+### Fixed
+- **`rigdoctor update` now uses the right method for how RigDoctor was installed.** It detects
+  apt (`.deb`), pip (venv/`.run`), or source installs (`updates.install_kind()`); only pip
+  installs self-update in place. An apt install no longer fails with "No module named pip" —
+  it (and the GUI Update button) shows `sudo apt update && sudo apt install --only-upgrade
+  rigdoctor`; a source checkout points to `git pull`.
+
 ## [0.37.0] - 2026-05-22
 ### Added
 - **Version footer** — a footer across the bottom of the window shows `RigDoctor v<version>` in
diff --git a/pyproject.toml b/pyproject.toml
index 37c944f..0e5d594 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "rigdoctor"
-version = "0.37.0"
+version = "0.37.1"
 description = "Modular hardware monitoring & crash diagnostics for Linux gamers."
 readme = "README.md"
 requires-python = ">=3.11"
diff --git a/src/rigdoctor/__init__.py b/src/rigdoctor/__init__.py
index 23a6340..3d2cff1 100644
--- a/src/rigdoctor/__init__.py
+++ b/src/rigdoctor/__init__.py
@@ -1,3 +1,3 @@
 """RigDoctor — modular hardware monitoring & crash diagnostics for Linux gamers."""
 
-__version__ = "0.37.0"
+__version__ = "0.37.1"
diff --git a/src/rigdoctor/cli.py b/src/rigdoctor/cli.py
index e83e530..a10e58c 100644
--- a/src/rigdoctor/cli.py
+++ b/src/rigdoctor/cli.py
@@ -263,6 +263,10 @@ def cmd_update(args) -> int:
         print("\nWhat's new:\n" + "\n".join("  " + ln for ln in notes.splitlines()) + "\n")
     if args.check:
         return 0
+    kind = updates.install_kind()
+    if kind != "pip":  # apt/source installs aren't pip-updatable — show the right command
+        print(updates.update_hint(kind))
+        return 0
     print(f"Installing {tag}…")
     rc, out = updates.apply_update(tag)
     print(out[-2000:])
diff --git a/src/rigdoctor/core/updates.py b/src/rigdoctor/core/updates.py
index c00f7f1..7fe37af 100644
--- a/src/rigdoctor/core/updates.py
+++ b/src/rigdoctor/core/updates.py
@@ -8,11 +8,14 @@ state for the UI; `apply_update` performs the no-root self-update.
 
 from __future__ import annotations
 
+import functools
 import json
+import shutil
 import subprocess
 import sys
 import urllib.error
 import urllib.request
+from pathlib import Path
 
 from .. import __version__
 from ..config import load_token
@@ -31,6 +34,50 @@ UP_TO_DATE = "up-to-date"
 AVAILABLE = "available"
 
 
+APT_PACKAGE = "rigdoctor"
+
+
+def _dpkg_owns(path: Path) -> bool:
+    """True if dpkg reports `path` belongs to a package (i.e. an apt/.deb install)."""
+    if not shutil.which("dpkg"):
+        return False
+    try:
+        r = subprocess.run(["dpkg", "-S", str(path)], capture_output=True, text=True, timeout=5)
+    except (subprocess.SubprocessError, OSError):
+        return False
+    return r.returncode == 0 and APT_PACKAGE in r.stdout
+
+
+@functools.lru_cache(maxsize=1)
+def install_kind() -> str:
+    """How RigDoctor was installed: 'apt' (.deb), 'pip' (venv/.run), or 'dev' (source checkout).
+
+    Decides which updater to use: only 'pip' can self-update in place; apt is root/dpkg-managed
+    and source is VCS-managed, so those are guided rather than auto-applied.
+    """
+    pkg = Path(__file__).resolve().parents[1]  # .../rigdoctor
+    if _dpkg_owns(pkg / "__init__.py"):
+        return "apt"
+    if sys.prefix != sys.base_prefix:  # inside a venv → the pip/.run install
+        return "pip"
+    if (pkg.parents[1] / "pyproject.toml").exists():  # repo checkout
+        return "dev"
+    if str(pkg).startswith("/usr/") or "/dist-packages/" in str(pkg):
+        return "apt"  # system-managed but no dpkg record — still don't pip
+    return "pip"
+
+
+def update_hint(kind: str | None = None) -> str:
+    """Human guidance for installs that can't self-update via pip (apt / source)."""
+    kind = kind or install_kind()
+    if kind == "apt":
+        return ("Installed via apt — update with:\n"
+                f"  sudo apt update && sudo apt install --only-upgrade {APT_PACKAGE}")
+    if kind == "dev":
+        return "Running from a source checkout — update with `git pull`."
+    return ""
+
+
 def _parse(version: str) -> tuple[int, ...]:
     return tuple(int(p) for p in version.lstrip("vV").split(".") if p.isdigit())
 
@@ -100,11 +147,16 @@ def list_releases(limit: int = 15, timeout: float = 6.0) -> tuple[list[tuple[str
 
 
 def apply_update(tag: str) -> tuple[int, str]:
-    """Self-update the current (user-local) install to `tag` via authenticated pip.
+    """Update to `tag` using the method matching how RigDoctor was installed.
 
-    Installs `rigdoctor[gui] @ git+https://oauth2:<token>@…/rigdoctor.git@<tag>` into
-    the running environment. Returns (exit_code, output) with the token scrubbed.
+    Only pip/venv installs are upgraded in place (authenticated pip install of
+    `rigdoctor[gui] @ git+https://oauth2:<token>@…/rigdoctor.git@<tag>`). apt and source
+    installs can't be (root/dpkg- or VCS-managed), so they return guidance instead of
+    attempting pip. Returns (exit_code, output) with the token scrubbed.
     """
+    kind = install_kind()
+    if kind != "pip":
+        return (1, update_hint(kind))
     token = load_token()
     if not token:
         return (1, "No update token configured. Run `rigdoctor login`.")
diff --git a/src/rigdoctor/gui/main_window.py b/src/rigdoctor/gui/main_window.py
index d8d5881..5ce9247 100644
--- a/src/rigdoctor/gui/main_window.py
+++ b/src/rigdoctor/gui/main_window.py
@@ -289,6 +289,9 @@ class MainWindow(QMainWindow):
     def _apply_update(self) -> None:
         if not self._latest_tag:
             return
+        if updates.install_kind() != "pip":  # apt/source: can't pip-update — show the command
+            QMessageBox.information(self, "Update RigDoctor", updates.update_hint())
+            return
         box = QMessageBox(self)
         box.setWindowTitle(f"Update to {self._latest_tag}")
         box.setText(f"Update RigDoctor to {self._latest_tag}?")
@@ -454,7 +457,7 @@ class MainWindow(QMainWindow):
             self._update_label.setText("update check unavailable")
         elif state == updates.AVAILABLE:
             self._update_label.setText(f'<span style="color:{GOOD};">{tag} available</span>')
-            self._update_btn.setText(f"Update to {tag}")
+            self._update_btn.setText(f"Update to {tag}" if updates.install_kind() == "pip" else "How to update")
             self._update_btn.setVisible(True)
             if self._alert_monitor.enabled and tag != self._notified_update_tag:
                 self._notified_update_tag = tag  # once per version, not every poll
diff --git a/tests/test_updates.py b/tests/test_updates.py
new file mode 100644
index 0000000..9721435
--- /dev/null
+++ b/tests/test_updates.py
@@ -0,0 +1,64 @@
+"""Tests for the M13 updater: install detection + routing the update to the right method."""
+
+import unittest
+from unittest import mock
+
+from rigdoctor.core import updates
+
+
+class InstallKindTests(unittest.TestCase):
+    def setUp(self):
+        updates.install_kind.cache_clear()
+
+    def tearDown(self):
+        updates.install_kind.cache_clear()
+
+    def test_apt_when_dpkg_owns_the_package(self):
+        with mock.patch.object(updates, "_dpkg_owns", return_value=True):
+            self.assertEqual(updates.install_kind(), "apt")
+
+    def test_pip_when_running_in_a_venv(self):
+        with mock.patch.object(updates, "_dpkg_owns", return_value=False), \
+             mock.patch.object(updates.sys, "prefix", "/opt/venv"), \
+             mock.patch.object(updates.sys, "base_prefix", "/usr"):
+            self.assertEqual(updates.install_kind(), "pip")
+
+
+class ApplyUpdateRoutingTests(unittest.TestCase):
+    def test_apt_returns_guidance_and_never_runs_pip(self):
+        with mock.patch.object(updates, "install_kind", return_value="apt"), \
+             mock.patch("subprocess.run") as run:
+            rc, out = updates.apply_update("v9.9.9")
+        self.assertEqual(rc, 1)
+        self.assertIn("apt install --only-upgrade", out)
+        run.assert_not_called()
+
+    def test_dev_returns_guidance_and_never_runs_pip(self):
+        with mock.patch.object(updates, "install_kind", return_value="dev"), \
+             mock.patch("subprocess.run") as run:
+            rc, out = updates.apply_update("v9.9.9")
+        self.assertIn("git pull", out)
+        run.assert_not_called()
+
+    def test_pip_install_runs_pip(self):
+        proc = mock.Mock(returncode=0, stdout="Successfully installed", stderr="")
+        with mock.patch.object(updates, "install_kind", return_value="pip"), \
+             mock.patch.object(updates, "load_token", return_value="TOK"), \
+             mock.patch("subprocess.run", return_value=proc) as run:
+            rc, _out = updates.apply_update("v1.2.3")
+        self.assertEqual(rc, 0)
+        cmd = run.call_args[0][0]
+        self.assertIn("pip", cmd)
+        self.assertIn("install", cmd)
+
+
+class UpdateHintTests(unittest.TestCase):
+    def test_apt_hint_names_the_apt_command(self):
+        self.assertIn("apt install --only-upgrade rigdoctor", updates.update_hint("apt"))
+
+    def test_dev_hint_says_git_pull(self):
+        self.assertIn("git pull", updates.update_hint("dev"))
+
+
+if __name__ == "__main__":
+    unittest.main()