diff --git a/CHANGELOG.md b/CHANGELOG.md
index 172ba7a..ed6b137 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,27 @@ This project uses calendar versioning: `YY.N-stage` (e.g. `26.0-alpha` = 2026, r
 
 ## [Unreleased]
 
+## [26.12-alpha] - 2026-04-21
+
+### Changed
+
+- **App-Install geht async mit Live-Progress.** `POST /api/apps/install`
+  returnt jetzt `202 Accepted` nach der synchronen Pre-Validation
+  (Source auflösen, Files kopieren, `.env` schreiben, Placeholder- und
+  Path-Checks). Den eigentlichen Docker-Teil (`compose pull` → volumes
+  → `compose up`) dispatched der Handler als `systemd-run
+  --unit=furtka-install-<app>` Hintergrund-Job, der seine Phase in
+  `/var/lib/furtka/install-state.json` schreibt. Neues
+  `GET /api/apps/install/status` für UI-Polling. Das Install-Modal
+  zeigt jetzt live "Image wird heruntergeladen…" →
+  "Speicherbereiche werden erstellt…" → "Container wird gestartet…"
+  statt ~30 Sekunden totem "Installing…". Muster 1:1 parallel zu
+  `/api/catalog/sync/apply` und `/api/furtka/update/apply`. Neue CLI-
+  Subcommand `furtka app install-bg <name>` (intern, von der API
+  aufgerufen); `furtka app install` für Terminal-User bleibt synchron.
+  Die Reinstall-Taste in der App-Liste pollt ebenfalls den
+  Install-Status und spiegelt die Phase im Button-Text.
+
 ## [26.11-alpha] - 2026-04-21
 
 ### Added
@@ -222,7 +243,8 @@ First tagged snapshot. Pre-alpha — the installer does not yet boot, but the de
 - **Containers:** Docker + Compose
 - **License:** AGPL-3.0
 
-[Unreleased]: https://forgejo.sourcegate.online/daniel/furtka/compare/26.11-alpha...HEAD
+[Unreleased]: https://forgejo.sourcegate.online/daniel/furtka/compare/26.12-alpha...HEAD
+[26.12-alpha]: https://forgejo.sourcegate.online/daniel/furtka/releases/tag/26.12-alpha
 [26.11-alpha]: https://forgejo.sourcegate.online/daniel/furtka/releases/tag/26.11-alpha
 [26.10-alpha]: https://forgejo.sourcegate.online/daniel/furtka/releases/tag/26.10-alpha
 [26.9-alpha]: https://forgejo.sourcegate.online/daniel/furtka/releases/tag/26.9-alpha
diff --git a/furtka/api.py b/furtka/api.py
index d3c84e3..9095754 100644
--- a/furtka/api.py
+++ b/furtka/api.py
@@ -21,7 +21,7 @@ import time
 from http.cookies import SimpleCookie
 from http.server import BaseHTTPRequestHandler, HTTPServer
 
-from furtka import auth, dockerops, installer, reconciler, sources
+from furtka import auth, dockerops, install_runner, installer, reconciler, sources
 from furtka.manifest import ManifestError, load_manifest
 from furtka.paths import apps_dir
 from furtka.scanner import scan
@@ -214,6 +214,51 @@ async function openSettingsDialog(name, action) {
 
 modal.submit.addEventListener('click', submitModal);
 
+// Install progress phases written by the background job's state file.
+// Mirrors furtka/install_runner.py stage strings. Unknown stages fall
+// back to a neutral "Installing…" so a future phase rename doesn't
+// leave the modal button blank.
+const INSTALL_STAGE_LABELS = {
+  'pulling_image': 'Image wird heruntergeladen…',
+  'creating_volumes': 'Speicherbereiche werden erstellt…',
+  'starting_container': 'Container wird gestartet…',
+  'done': 'Fertig',
+};
+
+async function pollInstallStatus(original) {
+  // Two-minute ceiling: Jellyfin over a slow DSL line can take ~90s
+  // just on the image pull. Beyond that something's stuck — the
+  // background job is still running in systemd, but the UI gives up
+  // on the modal and lets the user close it.
+  const deadline = Date.now() + 120000;
+  while (Date.now() < deadline) {
+    await new Promise(res => setTimeout(res, 1500));
+    let s = {};
+    try {
+      s = await fetch('/api/apps/install/status').then(r => r.json());
+    } catch (e) { /* transient; keep polling */ }
+    const stage = s.stage || '';
+    modal.submit.textContent = INSTALL_STAGE_LABELS[stage] || 'Installing…';
+    if (stage === 'done') {
+      closeModal();
+      await refresh();
+      return;
+    }
+    if (stage === 'error') {
+      modal.error.textContent = s.error || 'Install failed';
+      modal.error.classList.add('show');
+      modal.submit.disabled = false;
+      modal.submit.textContent = original;
+      return;
+    }
+  }
+  // Timed out waiting for a terminal state — don't lie to the user.
+  modal.error.textContent = 'Installation is taking longer than expected. Check /settings for the background job status.';
+  modal.error.classList.add('show');
+  modal.submit.disabled = false;
+  modal.submit.textContent = original;
+}
+
 async function submitModal() {
   if (!modal.current) return;
   const { name, action } = modal.current;
@@ -247,6 +292,13 @@ async function submitModal() {
       modal.submit.textContent = original;
       return;
     }
+    // Install dispatched a background job — poll until terminal. The
+    // edit path stays synchronous (settings updates are fast: env write
+    // + reconcile, no image pull).
+    if (action === 'install' && r.status === 202) {
+      await pollInstallStatus(original);
+      return;
+    }
     closeModal();
     await refresh();
   } catch (e) {
@@ -339,10 +391,24 @@ async function handleButton(op, name, btn) {
         : ' — already up to date';
     }
     document.getElementById('log').textContent = header + '\\n' + JSON.stringify(data, null, 2);
+    // Reinstall dispatches an async install the same way the modal does
+    // — follow the background job on the button label until terminal.
+    if (op === 'reinstall' && r.status === 202) {
+      const deadline = Date.now() + 120000;
+      while (Date.now() < deadline) {
+        await new Promise(res => setTimeout(res, 1500));
+        let s = {};
+        try { s = await fetch('/api/apps/install/status').then(r => r.json()); } catch (e) {}
+        const stage = s.stage || '';
+        btn.textContent = INSTALL_STAGE_LABELS[stage] || 'Reinstalling…';
+        if (stage === 'done' || stage === 'error') break;
+      }
+    }
   } catch (e) {
     document.getElementById('log').textContent = `[${op} ${name}] network error: ${e.message}`;
   }
   btn.textContent = original;
+  btn.disabled = false;
   await refresh();
 }
 
@@ -627,18 +693,66 @@ def _do_get_settings(name):
 
 
 def _do_install(name, settings=None):
+    """Kick off an app install. Synchronous sync-phase + async docker-phase.
+
+    Fast parts run inline so validation failures come back as immediate
+    4xx (bad path, placeholder secret, unknown app, etc.). The slow
+    `docker compose pull` then `compose up` are dispatched as a
+    background systemd-run unit that writes phase transitions to
+    /var/lib/furtka/install-state.json for the UI to poll.
+    """
+    import subprocess
+
+    # Fast-fail if another install is already in flight. Lock lives under
+    # /run/ so a previous reboot clears it automatically.
     try:
-        src = installer.resolve_source(name)
-        target = installer.install_from(src, settings=settings)
-    except installer.InstallError as e:
-        return 400, {"error": str(e)}
-    actions = reconciler.reconcile(apps_dir())
-    payload = {
-        "installed": str(target),
-        "actions": [{"kind": a.kind, "target": a.target, "detail": a.detail} for a in actions],
-    }
-    # 207 Multi-Status — install copy succeeded but reconcile had per-app errors.
-    return (207 if reconciler.has_errors(actions) else 200, payload)
+        fh = install_runner.acquire_lock()
+    except install_runner.InstallRunnerError as e:
+        return 409, {"error": str(e)}
+    try:
+        try:
+            src = installer.resolve_source(name)
+            target = installer.install_from(src, settings=settings)
+        except installer.InstallError as e:
+            return 400, {"error": str(e)}
+        # Initial state so the UI has something to show between this
+        # response and the background job's first write.
+        install_runner.write_state("pulling_image", app=name)
+    finally:
+        # Release the lock so the background job can re-acquire it.
+        fh.close()
+
+    unit = f"furtka-install-{name}"
+    try:
+        subprocess.run(
+            [
+                "systemd-run",
+                f"--unit={unit}",
+                "--no-block",
+                "--collect",
+                "/usr/local/bin/furtka",
+                "app",
+                "install-bg",
+                name,
+            ],
+            check=True,
+            capture_output=True,
+            text=True,
+        )
+    except FileNotFoundError:
+        install_runner.write_state("error", app=name, error="systemd-run not available")
+        return 502, {"error": "systemd-run not available"}
+    except subprocess.CalledProcessError as e:
+        err = (e.stderr or e.stdout or "").strip()
+        install_runner.write_state("error", app=name, error=f"dispatch failed: {err}")
+        return 502, {"error": f"systemd-run failed: {err}"}
+
+    return 202, {"status": "dispatched", "unit": unit, "installed": str(target)}
+
+
+def _do_install_status():
+    """Return the current install-state.json contents (or {})."""
+    return 200, install_runner.read_state()
 
 
 def _do_update_settings(name, settings):
@@ -1100,6 +1214,9 @@ class _Handler(BaseHTTPRequestHandler):
         if self.path == "/api/catalog/status":
             status, body = _do_catalog_status()
             return self._json(status, body)
+        if self.path == "/api/apps/install/status":
+            status, body = _do_install_status()
+            return self._json(status, body)
         # /api/apps/<name>/settings
         if self.path.startswith("/api/apps/") and self.path.endswith("/settings"):
             name = self.path[len("/api/apps/") : -len("/settings")]
diff --git a/furtka/cli.py b/furtka/cli.py
index d4af59a..bf56cab 100644
--- a/furtka/cli.py
+++ b/furtka/cli.py
@@ -71,6 +71,24 @@ def _cmd_app_install(args: argparse.Namespace) -> int:
     return 1 if reconciler.has_errors(actions) else 0
 
 
+def _cmd_app_install_bg(args: argparse.Namespace) -> int:
+    """Docker-facing phases of an install — called by the API via systemd-run.
+
+    Internal subcommand; normal CLI users want `app install` (synchronous).
+    This exists to separate the slow docker pull/up from the synchronous
+    validation the API does inline, so the UI can poll a state file.
+    """
+    from furtka import install_runner
+
+    try:
+        install_runner.run_install(args.name)
+    except Exception as e:
+        # run_install already wrote state="error"; echo for journald.
+        print(f"install-bg failed: {e}", file=sys.stderr)
+        return 1
+    return 0
+
+
 def _cmd_app_remove(args: argparse.Namespace) -> int:
     target = apps_dir() / args.name
     if not target.exists():
@@ -237,6 +255,15 @@ def build_parser() -> argparse.ArgumentParser:
     )
     app_install.set_defaults(func=_cmd_app_install)
 
+    # Internal — called by the HTTP API via systemd-run. Deliberately omitted
+    # from the help listing; regular CLI users want `app install` above.
+    app_install_bg = app_sub.add_parser(
+        "install-bg",
+        help=argparse.SUPPRESS,
+    )
+    app_install_bg.add_argument("name", help="Installed app folder name")
+    app_install_bg.set_defaults(func=_cmd_app_install_bg)
+
     app_remove = app_sub.add_parser("remove", help="Stop and uninstall an app (keeps volumes)")
     app_remove.add_argument("name", help="App name (folder name under /var/lib/furtka/apps/)")
     app_remove.set_defaults(func=_cmd_app_remove)
diff --git a/furtka/install_runner.py b/furtka/install_runner.py
new file mode 100644
index 0000000..2bf290d
--- /dev/null
+++ b/furtka/install_runner.py
@@ -0,0 +1,121 @@
+"""Background job for app installs — progress-visible via state file.
+
+The slow part of installing an app is `docker compose pull` on a large
+image (Jellyfin ~500 MB); without progress feedback, the UI modal sits
+dead on "Installing…" for 30+ seconds and the user wonders if it hung.
+
+This module mirrors the exact same shape as ``furtka.catalog`` and
+``furtka.updater`` so the UI can poll an install just like it polls a
+catalog sync or a self-update. The split is:
+
+- ``furtka.api._do_install`` runs synchronously: resolve source, copy
+  the app folder, write .env, validate path settings + placeholders.
+  Those are fast, and their failures deserve an immediate 4xx so the
+  install modal can surface them in-line.
+- After that the API writes an initial state file (stage
+  "pulling_image") and dispatches ``systemd-run --unit=furtka-install-
+  <name>`` to run ``furtka app install-bg <name>`` in the background.
+  That CLI subcommand is what calls ``run_install()`` here — it does the
+  docker-facing phases and writes state transitions as it goes.
+
+State file schema (``/var/lib/furtka/install-state.json``):
+
+    {
+      "stage": "pulling_image" | "creating_volumes"
+             | "starting_container" | "done" | "error",
+      "updated_at": "2026-04-21T17:30:45+0200",
+      "app": "jellyfin",
+      "version": "1.0.0",            // added at "done"
+      "error": "details..."          // added at "error"
+    }
+
+Lock: ``/run/furtka/install.lock`` (tmpfs, reboot-safe). Global, not
+per-app — two parallel installs are not a v1 use-case and the lock
+keeps the state-file representation simple (one in-flight install at
+a time).
+"""
+
+from __future__ import annotations
+
+import fcntl
+import json
+import os
+import time
+from pathlib import Path
+
+from furtka import dockerops
+from furtka.manifest import load_manifest
+from furtka.paths import apps_dir
+
+_INSTALL_STATE = Path(os.environ.get("FURTKA_INSTALL_STATE", "/var/lib/furtka/install-state.json"))
+_LOCK_PATH = Path(os.environ.get("FURTKA_INSTALL_LOCK", "/run/furtka/install.lock"))
+
+
+class InstallRunnerError(RuntimeError):
+    """Any failure in the background install flow that should surface to the caller."""
+
+
+def state_path() -> Path:
+    return _INSTALL_STATE
+
+
+def lock_path() -> Path:
+    return _LOCK_PATH
+
+
+def write_state(stage: str, **extra) -> None:
+    """Atomic JSON state write — same shape as catalog/update-state."""
+    state_path().parent.mkdir(parents=True, exist_ok=True)
+    tmp = state_path().with_suffix(".tmp")
+    payload = {"stage": stage, "updated_at": time.strftime("%Y-%m-%dT%H:%M:%S%z"), **extra}
+    tmp.write_text(json.dumps(payload, indent=2))
+    tmp.replace(state_path())
+
+
+def read_state() -> dict:
+    try:
+        return json.loads(state_path().read_text())
+    except (FileNotFoundError, json.JSONDecodeError):
+        return {}
+
+
+def acquire_lock():
+    path = lock_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    fh = path.open("w")
+    try:
+        fcntl.flock(fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except BlockingIOError as e:
+        fh.close()
+        raise InstallRunnerError("another install is already in progress") from e
+    return fh
+
+
+def run_install(name: str) -> None:
+    """Docker-facing phases of the install: pull → volumes → compose up.
+
+    Called by the ``furtka app install-bg <name>`` CLI subcommand from the
+    systemd-run spawned by the API. Assumes the API has already run
+    ``installer.install_from()``, so the app folder, .env, and manifest
+    are on disk at ``apps_dir() / <name>``.
+
+    Every phase transition is written to the state file for the UI to
+    poll. On exception the state flips to ``"error"`` with the message,
+    then the exception is re-raised so the CLI exits non-zero and
+    journald has a traceback.
+    """
+    with acquire_lock():
+        target = apps_dir() / name
+        manifest = load_manifest(target / "manifest.json", expected_name=name)
+        try:
+            write_state("pulling_image", app=name)
+            dockerops.compose_pull(target, name)
+            write_state("creating_volumes", app=name)
+            for short in manifest.volumes:
+                dockerops.ensure_volume(manifest.volume_name(short))
+            write_state("starting_container", app=name)
+            dockerops.compose_up(target, name)
+            write_state("done", app=name, version=manifest.version)
+        except Exception as e:
+            write_state("error", app=name, error=str(e))
+            raise
diff --git a/pyproject.toml b/pyproject.toml
index d9123fc..f964c71 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "furtka"
-version = "26.11-alpha"
+version = "26.12-alpha"
 description = "Open-source home server OS — simple enough for everyone."
 requires-python = ">=3.11"
 readme = "README.md"
diff --git a/tests/test_api.py b/tests/test_api.py
index fca872b..1b35d26 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -30,6 +30,18 @@ def fake_dirs(tmp_path, monkeypatch):
     monkeypatch.setenv("FURTKA_BUNDLED_APPS_DIR", str(bundled))
     monkeypatch.setenv("FURTKA_CATALOG_DIR", str(catalog))
     monkeypatch.setenv("FURTKA_USERS_FILE", str(users_file))
+    # install_runner writes to /var/lib/furtka/install-state.json and
+    # /run/furtka/install.lock by default — redirect into tmp_path so
+    # test code doesn't need root.
+    monkeypatch.setenv("FURTKA_INSTALL_STATE", str(tmp_path / "install-state.json"))
+    monkeypatch.setenv("FURTKA_INSTALL_LOCK", str(tmp_path / "install.lock"))
+    # install_runner caches env vars at import time, so reload it to
+    # pick up the tmp-path env vars this fixture just set.
+    import importlib
+
+    from furtka import install_runner
+
+    importlib.reload(install_runner)
     # Scrub any sessions that leaked from a prior test — the SESSIONS
     # store is module-level.
     auth.SESSIONS.clear()
@@ -53,6 +65,29 @@ def no_docker(monkeypatch):
     monkeypatch.setattr(dockerops, "compose_down", lambda app_dir, project: None)
 
 
+@pytest.fixture
+def no_systemd_run(monkeypatch):
+    """Stub the systemd-run dispatch in _do_install so tests don't need it.
+
+    The install endpoint now spawns a background systemd-run unit to do
+    the docker-facing phases. Tests that exercise the install path only
+    care that the sync pre-phase succeeded and the dispatch was
+    attempted with the right args — they shouldn't actually fire up
+    systemd. subprocess.run gets monkeypatched to return a fake success
+    CompletedProcess, and the call args get captured for assertions.
+    """
+    import subprocess
+
+    calls = []
+
+    def fake_run(cmd, check=False, capture_output=False, text=False, **kwargs):
+        calls.append(cmd)
+        return subprocess.CompletedProcess(cmd, 0, stdout="", stderr="")
+
+    monkeypatch.setattr(subprocess, "run", fake_run)
+    return calls
+
+
 def _write_bundled(bundled, name, manifest=None, env_example=None):
     app = bundled / name
     app.mkdir()
@@ -145,7 +180,7 @@ def test_list_available_inlines_icon_svg(fake_dirs):
     assert entry["icon_svg"] == _SIMPLE_SVG
 
 
-def test_list_installed_inlines_icon_svg(fake_dirs, no_docker):
+def test_list_installed_inlines_icon_svg(fake_dirs, no_docker, no_systemd_run):
     apps, bundled = fake_dirs
     app = _write_bundled(bundled, "fileshare", env_example="A=real")
     _write_icon(app, _SIMPLE_SVG)
@@ -154,12 +189,15 @@ def test_list_installed_inlines_icon_svg(fake_dirs, no_docker):
     assert entry["icon_svg"] == _SIMPLE_SVG
 
 
-def test_list_available_hides_already_installed(fake_dirs, no_docker):
+def test_list_available_hides_already_installed(fake_dirs, no_docker, no_systemd_run):
     apps, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     status, _ = api._do_install("fileshare")
-    assert status == 200
-    # Now bundled should NOT include fileshare anymore.
+    assert status == 202  # async dispatch
+    # Now bundled should NOT include fileshare anymore — the app folder
+    # exists on disk (install_from finished synchronously before the
+    # dispatch), which is what _list_available uses for the "installed"
+    # check.
     assert api._list_available() == []
     # But installed list should.
     installed = api._list_installed()
@@ -202,7 +240,7 @@ def test_remove_endpoint_unknown(fake_dirs, no_docker):
     assert status == 404
 
 
-def test_remove_endpoint_happy_path(fake_dirs, no_docker):
+def test_remove_endpoint_happy_path(fake_dirs, no_docker, no_systemd_run):
     apps, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -562,13 +600,13 @@ def test_get_settings_not_found(fake_dirs):
     assert status == 404
 
 
-def test_install_with_settings_writes_env_via_api(fake_dirs, no_docker):
+def test_install_with_settings_writes_env_via_api(fake_dirs, no_docker, no_systemd_run):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", manifest=SETTINGS_MANIFEST)
     status, body = api._do_install(
         "fileshare", settings={"SMB_USER": "alice", "SMB_PASSWORD": "s3cret"}
     )
-    assert status == 200, body
+    assert status == 202, body
     apps, _ = fake_dirs
     env = (apps / "fileshare" / ".env").read_text()
     assert "SMB_USER=alice" in env
@@ -583,7 +621,7 @@ def test_install_with_settings_rejects_empty_required_via_api(fake_dirs, no_dock
     assert "SMB_PASSWORD" in body["error"]
 
 
-def test_update_settings_merges(fake_dirs, no_docker):
+def test_update_settings_merges(fake_dirs, no_docker, no_systemd_run):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", manifest=SETTINGS_MANIFEST)
     api._do_install("fileshare", settings={"SMB_USER": "alice", "SMB_PASSWORD": "original"})
@@ -665,7 +703,7 @@ def test_update_not_installed(fake_dirs):
     assert "not installed" in body["error"]
 
 
-def test_update_no_changes(fake_dirs, no_docker, update_docker_stubs):
+def test_update_no_changes(fake_dirs, no_docker, no_systemd_run, update_docker_stubs):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -678,7 +716,7 @@ def test_update_no_changes(fake_dirs, no_docker, update_docker_stubs):
     assert update_docker_stubs["up_called"] == 0
 
 
-def test_update_changes_applied(fake_dirs, no_docker, update_docker_stubs):
+def test_update_changes_applied(fake_dirs, no_docker, no_systemd_run, update_docker_stubs):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -698,7 +736,9 @@ def test_update_changes_applied(fake_dirs, no_docker, update_docker_stubs):
     assert update_docker_stubs["up_called"] == 1
 
 
-def test_update_skips_services_not_running(fake_dirs, no_docker, update_docker_stubs):
+def test_update_skips_services_not_running(
+    fake_dirs, no_docker, no_systemd_run, update_docker_stubs
+):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -712,7 +752,9 @@ def test_update_skips_services_not_running(fake_dirs, no_docker, update_docker_s
     assert update_docker_stubs["up_called"] == 0
 
 
-def test_update_returns_502_on_pull_error(fake_dirs, no_docker, update_docker_stubs):
+def test_update_returns_502_on_pull_error(
+    fake_dirs, no_docker, no_systemd_run, update_docker_stubs
+):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -823,7 +865,9 @@ def test_furtka_update_status_endpoint(stub_furtka_updater):
     assert stub_furtka_updater["status_called"] == 1
 
 
-def test_http_post_update_route(fake_dirs, no_docker, update_docker_stubs, admin_session):
+def test_http_post_update_route(
+    fake_dirs, no_docker, no_systemd_run, update_docker_stubs, admin_session
+):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", env_example="A=real")
     api._do_install("fileshare")
@@ -851,7 +895,7 @@ def test_http_post_update_route(fake_dirs, no_docker, update_docker_stubs, admin
         server.server_close()
 
 
-def test_http_post_install_with_settings(fake_dirs, no_docker, admin_session):
+def test_http_post_install_with_settings(fake_dirs, no_docker, no_systemd_run, admin_session):
     _, bundled = fake_dirs
     _write_bundled(bundled, "fileshare", manifest=SETTINGS_MANIFEST)
     server = api.HTTPServer(("127.0.0.1", 0), api._Handler)
@@ -870,14 +914,50 @@ def test_http_post_install_with_settings(fake_dirs, no_docker, admin_session):
             },
         )
         with urllib.request.urlopen(req) as r:
-            assert r.status == 200
+            # Async: 202 Accepted + dispatched background job.
+            assert r.status == 202
+            body = json.loads(r.read())
+            assert body["status"] == "dispatched"
+            assert body["unit"] == "furtka-install-fileshare"
+        # Sync phase wrote the .env before dispatch.
         apps, _ = fake_dirs
         assert "SMB_PASSWORD=s3cret" in (apps / "fileshare" / ".env").read_text()
+        # And systemd-run was called exactly once with the expected cmd.
+        assert len(no_systemd_run) == 1
+        assert no_systemd_run[0][:4] == [
+            "systemd-run",
+            "--unit=furtka-install-fileshare",
+            "--no-block",
+            "--collect",
+        ]
+        assert no_systemd_run[0][-3:] == ["app", "install-bg", "fileshare"]
     finally:
         server.shutdown()
         server.server_close()
 
 
+def test_do_install_returns_409_when_locked(fake_dirs, no_docker, no_systemd_run):
+    _, bundled = fake_dirs
+    _write_bundled(bundled, "fileshare", env_example="A=real")
+    # Hold the install lock so _do_install fast-fails.
+    fh = api.install_runner.acquire_lock()
+    try:
+        status, body = api._do_install("fileshare")
+        assert status == 409
+        assert "in progress" in body["error"]
+    finally:
+        fh.close()
+
+
+def test_do_install_status_returns_state(fake_dirs):
+    # Write state directly, then GET it via the status handler.
+    api.install_runner.write_state("pulling_image", app="jellyfin")
+    status, body = api._do_install_status()
+    assert status == 200
+    assert body["stage"] == "pulling_image"
+    assert body["app"] == "jellyfin"
+
+
 # --- Catalog endpoints ------------------------------------------------------
 
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index f6137b5..5648fae 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -71,3 +71,35 @@ def test_reconcile_dry_run_empty(tmp_path, monkeypatch, capsys):
     assert rc == 0
     out = capsys.readouterr().out
     assert "0 actions" in out
+
+
+def test_app_install_bg_dispatches_to_runner(tmp_path, monkeypatch):
+    """CLI `app install-bg <name>` must call install_runner.run_install(name).
+
+    This is the entry point the HTTP API fires via systemd-run; regression
+    here would leave the UI hanging at "pulling_image…" forever because
+    the background never transitions state.
+    """
+    _set_env(monkeypatch, tmp_path)
+    from furtka import install_runner
+
+    called = []
+    monkeypatch.setattr(install_runner, "run_install", lambda name: called.append(name))
+    rc = main(["app", "install-bg", "fileshare"])
+    assert rc == 0
+    assert called == ["fileshare"]
+
+
+def test_app_install_bg_returns_1_on_failure(tmp_path, monkeypatch, capsys):
+    _set_env(monkeypatch, tmp_path)
+    from furtka import install_runner
+
+    def boom(name):
+        raise RuntimeError("compose pull failed")
+
+    monkeypatch.setattr(install_runner, "run_install", boom)
+    rc = main(["app", "install-bg", "fileshare"])
+    assert rc == 1
+    err = capsys.readouterr().err
+    assert "install-bg failed" in err
+    assert "compose pull failed" in err
diff --git a/tests/test_install_runner.py b/tests/test_install_runner.py
new file mode 100644
index 0000000..e3a6885
--- /dev/null
+++ b/tests/test_install_runner.py
@@ -0,0 +1,177 @@
+"""Tests for the background app-install runner.
+
+Same shape as test_catalog.py / test_updater.py: fixture reloads the
+module with env-overridden paths, dockerops calls are stubbed so nothing
+touches a real daemon. Asserts that state transitions happen in the
+right order and that exceptions flip the state to "error" with the
+message before re-raising.
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+
+
+@pytest.fixture
+def runner(tmp_path, monkeypatch):
+    apps = tmp_path / "apps"
+    apps.mkdir()
+    monkeypatch.setenv("FURTKA_APPS_DIR", str(apps))
+    monkeypatch.setenv("FURTKA_INSTALL_STATE", str(tmp_path / "install-state.json"))
+    monkeypatch.setenv("FURTKA_INSTALL_LOCK", str(tmp_path / "install.lock"))
+
+    import importlib
+
+    from furtka import install_runner as r
+    from furtka import paths as p
+
+    importlib.reload(p)
+    importlib.reload(r)
+    return r
+
+
+def _write_installed_app(apps_dir: Path, name: str = "fileshare"):
+    app = apps_dir / name
+    app.mkdir()
+    manifest = {
+        "name": name,
+        "display_name": "Fileshare",
+        "version": "0.1.0",
+        "description": "Test fixture",
+        "volumes": ["files"],
+        "ports": [445],
+        "icon": "icon.svg",
+    }
+    (app / "manifest.json").write_text(json.dumps(manifest))
+    (app / "docker-compose.yaml").write_text("services: {}\n")
+    return app
+
+
+def test_write_and_read_state_round_trip(runner):
+    runner.write_state("pulling_image", app="jellyfin")
+    s = runner.read_state()
+    assert s["stage"] == "pulling_image"
+    assert s["app"] == "jellyfin"
+    assert "updated_at" in s
+
+
+def test_read_state_returns_empty_when_missing(runner):
+    assert runner.read_state() == {}
+
+
+def test_read_state_returns_empty_on_junk(runner):
+    runner.state_path().parent.mkdir(parents=True, exist_ok=True)
+    runner.state_path().write_text("{not json")
+    assert runner.read_state() == {}
+
+
+def test_acquire_lock_prevents_concurrent_runs(runner):
+    held = runner.acquire_lock()
+    try:
+        with pytest.raises(runner.InstallRunnerError, match="in progress"):
+            runner.acquire_lock()
+    finally:
+        held.close()
+
+
+def test_run_install_happy_path(runner, monkeypatch):
+    import furtka.dockerops as dockerops
+    from furtka.paths import apps_dir
+
+    _write_installed_app(apps_dir(), "fileshare")
+
+    calls = []
+    monkeypatch.setattr(dockerops, "compose_pull", lambda *a, **k: calls.append(("pull", a)))
+    monkeypatch.setattr(dockerops, "ensure_volume", lambda name: calls.append(("vol", name)))
+    monkeypatch.setattr(dockerops, "compose_up", lambda *a, **k: calls.append(("up", a)))
+
+    runner.run_install("fileshare")
+
+    # Ordering: pull first, then volumes, then up.
+    assert [c[0] for c in calls] == ["pull", "vol", "up"]
+    # Exactly the namespaced volume name got created.
+    assert calls[1] == ("vol", "furtka_fileshare_files")
+    # Final state is "done" with the manifest version.
+    s = runner.read_state()
+    assert s["stage"] == "done"
+    assert s["app"] == "fileshare"
+    assert s["version"] == "0.1.0"
+
+
+def test_run_install_writes_error_on_pull_failure(runner, monkeypatch):
+    import furtka.dockerops as dockerops
+    from furtka.paths import apps_dir
+
+    _write_installed_app(apps_dir(), "fileshare")
+
+    def boom(*a, **k):
+        raise dockerops.DockerError("pull failed: registry unreachable")
+
+    monkeypatch.setattr(dockerops, "compose_pull", boom)
+    monkeypatch.setattr(dockerops, "ensure_volume", lambda name: None)
+    monkeypatch.setattr(dockerops, "compose_up", lambda *a, **k: None)
+
+    with pytest.raises(dockerops.DockerError):
+        runner.run_install("fileshare")
+
+    s = runner.read_state()
+    assert s["stage"] == "error"
+    assert s["app"] == "fileshare"
+    assert "registry unreachable" in s["error"]
+
+
+def test_run_install_writes_error_on_up_failure(runner, monkeypatch):
+    import furtka.dockerops as dockerops
+    from furtka.paths import apps_dir
+
+    _write_installed_app(apps_dir(), "fileshare")
+
+    monkeypatch.setattr(dockerops, "compose_pull", lambda *a, **k: None)
+    monkeypatch.setattr(dockerops, "ensure_volume", lambda name: None)
+
+    def boom(*a, **k):
+        raise dockerops.DockerError("compose up: container refused to start")
+
+    monkeypatch.setattr(dockerops, "compose_up", boom)
+
+    with pytest.raises(dockerops.DockerError):
+        runner.run_install("fileshare")
+
+    s = runner.read_state()
+    assert s["stage"] == "error"
+    assert "refused to start" in s["error"]
+
+
+def test_run_install_releases_lock_after_done(runner, monkeypatch):
+    import furtka.dockerops as dockerops
+    from furtka.paths import apps_dir
+
+    _write_installed_app(apps_dir(), "fileshare")
+    monkeypatch.setattr(dockerops, "compose_pull", lambda *a, **k: None)
+    monkeypatch.setattr(dockerops, "ensure_volume", lambda name: None)
+    monkeypatch.setattr(dockerops, "compose_up", lambda *a, **k: None)
+
+    runner.run_install("fileshare")
+
+    # Lock released — a fresh acquire must succeed.
+    fh = runner.acquire_lock()
+    fh.close()
+
+
+def test_run_install_releases_lock_after_error(runner, monkeypatch):
+    import furtka.dockerops as dockerops
+    from furtka.paths import apps_dir
+
+    _write_installed_app(apps_dir(), "fileshare")
+    monkeypatch.setattr(
+        dockerops, "compose_pull", lambda *a, **k: (_ for _ in ()).throw(dockerops.DockerError("x"))
+    )
+
+    with pytest.raises(dockerops.DockerError):
+        runner.run_install("fileshare")
+
+    fh = runner.acquire_lock()
+    fh.close()