diff --git a/docs/openapi.yaml b/docs/openapi.yaml
index 4de31af..4f3843b 100644
--- a/docs/openapi.yaml
+++ b/docs/openapi.yaml
@@ -120,6 +120,19 @@ paths:
               properties:
                 email: { type: string, format: email }
                 password: { type: string }
+                client:
+                  type: string
+                  enum: [web, app]
+                  description: |
+                    `app` for the iOS app. Its session comes back as
+                    `session_token` instead of a cookie and slides — every use
+                    moves its end forward, up to `VERDANDE_APP_SESSION_TTL`
+                    (180 days) unused. Left out, it is a browser login.
+                device_name:
+                  type: string
+                  maxLength: 100
+                  description: Required with `client: app`; shown in the list of sessions.
+                  example: Kristians iPhone
       responses:
         "200":
           description: |
@@ -132,7 +145,14 @@ paths:
                 properties:
                   user: { $ref: "#/components/schemas/User" }
                   totp_required: { type: boolean }
+                  session_token:
+                    type: string
+                    description: |
+                      An app login only, also while `totp_required` — the app
+                      sends it to `/auth/login/totp` too. Sent from then on as
+                      `Authorization: Bearer`. A browser never receives it.
         "401": { $ref: "#/components/responses/Unauthorized" }
+        "422": { $ref: "#/components/responses/Validation" }
         "429": { $ref: "#/components/responses/RateLimited" }
 
   /api/v1/auth/login/totp:
@@ -4439,6 +4459,10 @@ components:
         A personal API token, `vrd_…`. Carries its owner's permissions exactly —
         there is no separate service identity — and is refused on `/tokens`.
 
+        Or the iOS app's session, the `session_token` from an app login. That
+        one is a session and reaches everything a browser session does. A
+        browser's own session is never accepted here.
+
   responses:
     BadRequest:
       description: The body could not be read.
@@ -4973,6 +4997,12 @@ components:
             it so anything the summary gets wrong is still visible.
           example: Chrome på macOS
         user_agent: { type: string }
+        client:
+          type: string
+          enum: [web, app]
+          description: |
+            `app` for the iOS app, whose `device` is the name it gave itself and
+            whose `expires_at` moves forward each time it is used.
         ip: { type: string }
         created_at: { type: string, format: date-time }
         last_seen_at: { type: string, format: date-time }
diff --git a/internal/config/config.go b/internal/config/config.go
index f269895..c1e146c 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -24,8 +24,12 @@ type Config struct {
 	DataDir string
 
 	SessionTTL time.Duration
-	InviteTTL  time.Duration
-	ResetTTL   time.Duration
+	// AppSessionTTL is how long a session from the iOS app may sit unused before
+	// it ends. It slides: every use moves the end forward, so a phone in daily use
+	// stays signed in and one left in a drawer does not.
+	AppSessionTTL time.Duration
+	InviteTTL     time.Duration
+	ResetTTL      time.Duration
 
 	SMTP SMTP
 
@@ -166,6 +170,9 @@ func Load() (*Config, error) {
 	if c.SessionTTL, err = envDuration("VERDANDE_SESSION_TTL", 30*24*time.Hour); err != nil {
 		return nil, err
 	}
+	if c.AppSessionTTL, err = envDuration("VERDANDE_APP_SESSION_TTL", 180*24*time.Hour); err != nil {
+		return nil, err
+	}
 	if c.InviteTTL, err = envDuration("VERDANDE_INVITE_TTL", 7*24*time.Hour); err != nil {
 		return nil, err
 	}
diff --git a/internal/httpapi/app_session_test.go b/internal/httpapi/app_session_test.go
new file mode 100644
index 0000000..457f677
--- /dev/null
+++ b/internal/httpapi/app_session_test.go
@@ -0,0 +1,269 @@
+package httpapi
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/url"
+	"testing"
+	"time"
+)
+
+// The iOS app loads its interface from itself — capacitor://localhost — so it
+// never shares an origin with the server and never gets a cookie back. It signs
+// in like a browser does and carries the same kind of session, as a bearer token.
+
+// appDo is a request the way the app makes it: no cookie jar, the token in a
+// header, and the browser engine reporting the request as cross-site, because to
+// WKWebView it is.
+func (ts *testServer) appDo(t *testing.T, token, method, path string, body any) (*http.Response, map[string]any) {
+	t.Helper()
+	var reader io.Reader
+	if body != nil {
+		raw, err := json.Marshal(body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		reader = bytes.NewReader(raw)
+	}
+	req, err := http.NewRequest(method, ts.URL+path, reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if body != nil {
+		req.Header.Set("Content-Type", "application/json")
+	}
+	if token != "" {
+		req.Header.Set("Authorization", "Bearer "+token)
+	}
+	req.Header.Set("Origin", "capacitor://localhost")
+	req.Header.Set("Sec-Fetch-Site", "cross-site")
+
+	resp, err := (&http.Client{Timeout: 10 * time.Second}).Do(req)
+	if err != nil {
+		t.Fatalf("%s %s: %v", method, path, err)
+	}
+	t.Cleanup(func() { resp.Body.Close() })
+	var decoded map[string]any
+	raw, _ := io.ReadAll(resp.Body)
+	if len(raw) > 0 {
+		_ = json.Unmarshal(raw, &decoded)
+	}
+	return resp, decoded
+}
+
+func appLogin(t *testing.T, ts *testServer) (*http.Response, map[string]any) {
+	t.Helper()
+	return ts.appDo(t, "", "POST", "/api/v1/auth/login", map[string]string{
+		"email": "kristian@example.dk", "password": "et langt kodeord",
+		"client": "app", "device_name": "Kristians iPhone",
+	})
+}
+
+func TestAppLoginReturnsATokenAndNoCookie(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	resp, body := appLogin(t, ts)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("app login: %d %v", resp.StatusCode, body)
+	}
+	if len(resp.Cookies()) != 0 {
+		t.Errorf("an app login set a cookie: %v", resp.Cookies())
+	}
+	token, _ := body["session_token"].(string)
+	if token == "" {
+		t.Fatalf("no session_token in %v", body)
+	}
+	if body["user"] == nil {
+		t.Error("no user in the response")
+	}
+
+	// The token is the whole credential, from a foreign origin, reads and writes.
+	resp, me := ts.appDo(t, token, "GET", "/api/v1/auth/me", nil)
+	if resp.StatusCode != http.StatusOK || me["email"] != "kristian@example.dk" {
+		t.Fatalf("me with the app token: %d %v", resp.StatusCode, me)
+	}
+	resp, body = ts.appDo(t, token, "POST", "/api/v1/projects", map[string]string{"name": "Fra telefonen"})
+	if resp.StatusCode != http.StatusCreated {
+		t.Errorf("a write from the app was refused: %d %v", resp.StatusCode, body)
+	}
+
+	// It is a session, not an API token: it reaches what a token may not, and it
+	// is in the list of devices under the name the app gave itself.
+	resp, body = ts.appDo(t, token, "GET", "/api/v1/auth/sessions", nil)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("sessions from the app: %d %v", resp.StatusCode, body)
+	}
+	var found bool
+	for _, raw := range body["sessions"].([]any) {
+		s := raw.(map[string]any)
+		if s["current"] == true {
+			found = true
+			if s["device"] != "Kristians iPhone" || s["client"] != "app" {
+				t.Errorf("the app's session reads %v / %v", s["device"], s["client"])
+			}
+		}
+	}
+	if !found {
+		t.Error("the app's own session is not marked current")
+	}
+
+	// And signing out ends it.
+	if resp, _ = ts.appDo(t, token, "POST", "/api/v1/auth/logout", nil); resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("logout: %d", resp.StatusCode)
+	}
+	if resp, _ = ts.appDo(t, token, "GET", "/api/v1/auth/me", nil); resp.StatusCode != http.StatusUnauthorized {
+		t.Errorf("the token still works after logout: %d", resp.StatusCode)
+	}
+}
+
+// A browser's session never leaves its httpOnly cookie. Its value replayed as a
+// bearer must not work: that would turn the header into a second way past the
+// SameSite and CSRF locks the cookie sits behind.
+func TestABrowserSessionIsNotABearer(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	var cookie string
+	for _, c := range ts.client.Jar.Cookies(mustURL(t, ts.URL)) {
+		if c.Name == sessionCookieInsecure {
+			cookie = c.Value
+		}
+	}
+	if cookie == "" {
+		t.Fatal("bootstrap left no session cookie")
+	}
+	if resp, _ := ts.appDo(t, cookie, "GET", "/api/v1/auth/me", nil); resp.StatusCode != http.StatusUnauthorized {
+		t.Errorf("a browser session worked as a bearer: %d", resp.StatusCode)
+	}
+	// Control: the same value is still a perfectly good cookie.
+	if resp, _ := ts.do(t, "GET", "/api/v1/auth/me", nil); resp.StatusCode != http.StatusOK {
+		t.Errorf("control: the cookie itself: %d", resp.StatusCode)
+	}
+}
+
+func TestAppLoginWithASecondFactor(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+	_, body := ts.do(t, "POST", "/api/v1/auth/totp/setup", map[string]string{"password": "et langt kodeord"})
+	secret, _ := body["secret"].(string)
+	if resp, body := ts.do(t, "POST", "/api/v1/auth/totp/confirm", map[string]string{"code": codeFor(t, secret)}); resp.StatusCode != http.StatusOK {
+		t.Fatalf("totp confirm: %d %v", resp.StatusCode, body)
+	}
+
+	resp, body := appLogin(t, ts)
+	token, _ := body["session_token"].(string)
+	if resp.StatusCode != http.StatusOK || body["totp_required"] != true || token == "" {
+		t.Fatalf("app login should hand over a token and ask for a code: %d %v", resp.StatusCode, body)
+	}
+	if body["user"] != nil {
+		t.Error("the user came back before the code was given")
+	}
+
+	// Half a login reaches nothing, as in a browser, and does not slide yet.
+	resp, body = ts.appDo(t, token, "GET", "/api/v1/auth/me", nil)
+	if resp.StatusCode != http.StatusUnauthorized || body["code"] != CodeTOTPRequired {
+		t.Errorf("a pending app session reached /me: %d %v", resp.StatusCode, body)
+	}
+	session, _, err := ts.db.SessionByToken(t.Context(), token)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if session.IdleTTL != 0 || time.Until(session.ExpiresAt) > 11*time.Minute {
+		t.Errorf("a pending app session lives %v and slides by %v", time.Until(session.ExpiresAt), session.IdleTTL)
+	}
+
+	resp, body = ts.appDo(t, token, "POST", "/api/v1/auth/login/totp", map[string]string{"code": codeFor(t, secret)})
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("totp from the app: %d %v", resp.StatusCode, body)
+	}
+	if len(resp.Cookies()) != 0 {
+		t.Errorf("finishing an app login set a cookie: %v", resp.Cookies())
+	}
+	if resp, _ = ts.appDo(t, token, "GET", "/api/v1/auth/me", nil); resp.StatusCode != http.StatusOK {
+		t.Errorf("me after the code: %d", resp.StatusCode)
+	}
+	session, _, _ = ts.db.SessionByToken(t.Context(), token)
+	if session.IdleTTL != 7*24*time.Hour {
+		t.Errorf("a finished app session slides by %v, want the app TTL", session.IdleTTL)
+	}
+}
+
+// A phone in daily use must not sign itself out; one left in a drawer must. The
+// end moves forward each time the session is used, and a browser's does not.
+func TestAnAppSessionSlides(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+	_, body := appLogin(t, ts)
+	token := body["session_token"].(string)
+
+	// Pretend it was last used a while ago and is a day from ending.
+	soon := time.Now().Add(24 * time.Hour).Unix()
+	if _, err := ts.db.ExecContext(t.Context(),
+		`UPDATE sessions SET last_seen_at = ?, expires_at = ? WHERE client = 'app'`,
+		time.Now().Add(-time.Hour).Unix(), soon); err != nil {
+		t.Fatal(err)
+	}
+	if resp, _ := ts.appDo(t, token, "GET", "/api/v1/auth/me", nil); resp.StatusCode != http.StatusOK {
+		t.Fatalf("me: %d", resp.StatusCode)
+	}
+	var expires int64
+	if err := ts.db.QueryRowContext(t.Context(),
+		`SELECT expires_at FROM sessions WHERE client = 'app'`).Scan(&expires); err != nil {
+		t.Fatal(err)
+	}
+	if left := time.Until(time.Unix(expires, 0)); left < 6*24*time.Hour {
+		t.Errorf("using the app session left %v on it, want about the app TTL", left)
+	}
+
+	// Control: a browser session used the same way keeps its fixed end.
+	if _, err := ts.db.ExecContext(t.Context(),
+		`UPDATE sessions SET last_seen_at = ?, expires_at = ? WHERE client = 'web'`,
+		time.Now().Add(-time.Hour).Unix(), soon); err != nil {
+		t.Fatal(err)
+	}
+	ts.do(t, "GET", "/api/v1/auth/me", nil)
+	if err := ts.db.QueryRowContext(t.Context(),
+		`SELECT expires_at FROM sessions WHERE client = 'web'`).Scan(&expires); err != nil {
+		t.Fatal(err)
+	}
+	if expires != soon {
+		t.Errorf("a browser session's end moved from %d to %d", soon, expires)
+	}
+}
+
+func TestAppLoginRefusesWhatItDoesNotKnow(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	for _, tc := range []struct {
+		name  string
+		body  map[string]string
+		field string
+	}{
+		{"unknown client", map[string]string{"client": "android", "device_name": "x"}, "client"},
+		{"app without a name", map[string]string{"client": "app", "device_name": "  "}, "device_name"},
+	} {
+		tc.body["email"] = "kristian@example.dk"
+		tc.body["password"] = "et langt kodeord"
+		resp, body := ts.appDo(t, "", "POST", "/api/v1/auth/login", tc.body)
+		if resp.StatusCode != http.StatusUnprocessableEntity {
+			t.Errorf("%s: status %d, want 422", tc.name, resp.StatusCode)
+			continue
+		}
+		if fields, _ := body["fields"].(map[string]any); fields[tc.field] == nil {
+			t.Errorf("%s: no error on %q in %v", tc.name, tc.field, body)
+		}
+	}
+}
+
+func mustURL(t *testing.T, raw string) *url.URL {
+	t.Helper()
+	u, err := url.Parse(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return u
+}
diff --git a/internal/httpapi/auth_handlers.go b/internal/httpapi/auth_handlers.go
index 158b3a1..9a3c215 100644
--- a/internal/httpapi/auth_handlers.go
+++ b/internal/httpapi/auth_handlers.go
@@ -159,11 +159,40 @@ func (s *Server) handleSetDefaultReminder(w http.ResponseWriter, r *http.Request
 type loginRequest struct {
 	Email    string `json:"email"`
 	Password string `json:"password"`
+	// Client is "app" when the iOS app signs in; empty is a browser. DeviceName is
+	// what the app calls itself, shown in the list of signed-in devices.
+	Client     string `json:"client"`
+	DeviceName string `json:"device_name"`
 }
 
 type loginResponse struct {
 	User         *userJSON `json:"user,omitempty"`
 	TOTPRequired bool      `json:"totp_required"`
+	// SessionToken is set for an app login only, and instead of the cookie: the
+	// app loads its interface from itself, so it never shares an origin with the
+	// server and a cookie would not come back. It is sent from then on as
+	// `Authorization: Bearer`. A browser never sees it — its session stays in an
+	// httpOnly cookie no script can read.
+	SessionToken string `json:"session_token,omitempty"`
+}
+
+// appClient reports whether a login asked for an app session, and refuses a value
+// it does not know rather than quietly giving it a browser session: a client that
+// asked for something else and got a cookie would look signed in until its next
+// request, and then not be.
+func appClient(w http.ResponseWriter, client, deviceName string) (app, ok bool) {
+	switch client {
+	case "", "web":
+		return false, true
+	case "app":
+		if strings.TrimSpace(deviceName) == "" {
+			writeFieldErrors(w, map[string]string{"device_name": "an app names the device it signs in from"})
+			return false, false
+		}
+		return true, true
+	}
+	writeFieldErrors(w, map[string]string{"client": `must be "app" or left out`})
+	return false, false
 }
 
 func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
@@ -171,6 +200,10 @@ func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
 	if err := decodeJSON(w, r, &req); err != nil {
 		return
 	}
+	app, ok := appClient(w, req.Client, req.DeviceName)
+	if !ok {
+		return
+	}
 
 	user, err := s.db.UserByEmail(r.Context(), req.Email)
 	if err != nil || auth.VerifyPassword(user.PasswordHash, req.Password) != nil {
@@ -215,22 +248,40 @@ func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
 	// A session that still needs a code gets a short life of its own: long enough
 	// to fetch a phone, not long enough to be worth stealing.
 	ttl := s.cfg.SessionTTL
+	if app {
+		ttl = s.cfg.AppSessionTTL
+	}
 	if user.TOTPEnabled {
 		ttl = 10 * time.Minute
 	}
-	token, _, err := s.db.CreateSession(r.Context(), user.ID, r.UserAgent(), clientIP(r), ttl, user.TOTPEnabled)
+	token, session, err := s.db.CreateSession(r.Context(), user.ID, r.UserAgent(), clientIP(r), ttl, user.TOTPEnabled)
 	if err != nil {
 		s.internal(w, r, "create session", err)
 		return
 	}
-	s.setSessionCookie(w, token, ttl)
 
-	if user.TOTPEnabled {
-		writeJSON(w, http.StatusOK, loginResponse{TOTPRequired: true})
-		return
+	resp := loginResponse{TOTPRequired: user.TOTPEnabled}
+	if app {
+		// Sliding only once the login is finished; a pending one keeps its ten
+		// minutes and handleLoginTOTP turns it on.
+		idle := s.cfg.AppSessionTTL
+		if user.TOTPEnabled {
+			idle = 0
+		}
+		if err := s.db.MarkAppSession(r.Context(), session.ID, req.DeviceName, idle); err != nil {
+			s.internal(w, r, "mark app session", err)
+			return
+		}
+		resp.SessionToken = token
+	} else {
+		s.setSessionCookie(w, token, ttl)
 	}
-	uj := toUserJSON(user)
-	writeJSON(w, http.StatusOK, loginResponse{User: &uj})
+
+	if !user.TOTPEnabled {
+		uj := toUserJSON(user)
+		resp.User = &uj
+	}
+	writeJSON(w, http.StatusOK, resp)
 }
 
 type totpRequest struct {
@@ -305,7 +356,19 @@ func (s *Server) handleLoginTOTP(w http.ResponseWriter, r *http.Request) {
 	s.loginLimiter.reset(clientIP(r))
 	s.totpLimiter.reset(user.ID)
 
-	if err := s.db.PromoteSession(r.Context(), session.ID, s.cfg.SessionTTL); err != nil {
+	// An app's session finishes as a sliding one; it already holds its token and
+	// gets no cookie.
+	if session.Client == "app" {
+		if err := s.db.PromoteSession(r.Context(), session.ID, s.cfg.AppSessionTTL, s.cfg.AppSessionTTL); err != nil {
+			s.internal(w, r, "promote session", err)
+			return
+		}
+		uj := toUserJSON(user)
+		writeJSON(w, http.StatusOK, loginResponse{User: &uj})
+		return
+	}
+
+	if err := s.db.PromoteSession(r.Context(), session.ID, s.cfg.SessionTTL, 0); err != nil {
 		s.internal(w, r, "promote session", err)
 		return
 	}
diff --git a/internal/httpapi/auth_test.go b/internal/httpapi/auth_test.go
index 110dfbe..02831b7 100644
--- a/internal/httpapi/auth_test.go
+++ b/internal/httpapi/auth_test.go
@@ -51,12 +51,13 @@ func newTestServerWith(t *testing.T, configure func(*config.Config)) *testServer
 	cfg := &config.Config{
 		// `localhost`, not a loopback IP: passkeys refuse an IP address as a relying
 		// party id, and every browser makes the same exception for localhost.
-		BaseURL:    "http://localhost",
-		DataDir:    t.TempDir(),
-		SessionTTL: 24 * time.Hour,
-		InviteTTL:  7 * 24 * time.Hour,
-		ResetTTL:   time.Hour,
-		Dev:        true,
+		BaseURL:       "http://localhost",
+		DataDir:       t.TempDir(),
+		SessionTTL:    24 * time.Hour,
+		AppSessionTTL: 7 * 24 * time.Hour,
+		InviteTTL:     7 * 24 * time.Hour,
+		ResetTTL:      time.Hour,
+		Dev:           true,
 	}
 	if configure != nil {
 		configure(cfg)
diff --git a/internal/httpapi/middleware.go b/internal/httpapi/middleware.go
index 8e6f5a1..3aa3a45 100644
--- a/internal/httpapi/middleware.go
+++ b/internal/httpapi/middleware.go
@@ -126,9 +126,10 @@ func (s *Server) requireAdmin(next http.Handler) http.Handler {
 	})
 }
 
-// authenticate resolves a request to a user, by session cookie or by API token.
+// authenticate resolves a request to a user, by session cookie, by API token, or by
+// an app's session sent as a bearer token.
 //
-// Both are accepted everywhere. An API token belongs to a person and carries their
+// All are accepted everywhere. An API token belongs to a person and carries their
 // permissions exactly — there is no separate service identity to reason about, and
 // a script therefore cannot reach anything its owner could not.
 // errNoCredentials means the request carried nothing to authenticate with, as
@@ -145,6 +146,21 @@ func (s *Server) authenticate(r *http.Request) (*store.User, *store.Session, err
 		return user, nil, nil
 	}
 
+	// Any other bearer is an app session (see loginResponse.SessionToken). It is
+	// accepted only for a session that was issued to the app: a browser's session
+	// never leaves its httpOnly cookie, and a cookie value found somewhere and
+	// replayed as a header must not become a second way to use it.
+	if token := bearerToken(r); token != "" {
+		session, user, err := s.db.SessionByToken(r.Context(), token)
+		if err != nil {
+			return nil, nil, err
+		}
+		if session.Client != "app" {
+			return nil, nil, store.ErrNotFound
+		}
+		return user, session, nil
+	}
+
 	cookie, err := r.Cookie(s.cookieName())
 	if err != nil || cookie.Value == "" {
 		return nil, nil, errNoCredentials
@@ -200,6 +216,14 @@ func (s *Server) requireCSRF(next http.Handler) http.Handler {
 			next.ServeHTTP(w, r)
 			return
 		}
+		// The iOS app, before it has a token: its sign-in. A web page cannot send
+		// this Origin — the browser writes the header, not the page — and an app
+		// login sets no cookie, so there is no session here for a forged request
+		// to ride on.
+		if isAppOrigin(r.Header.Get("Origin")) {
+			next.ServeHTTP(w, r)
+			return
+		}
 
 		// Sec-Fetch-Site is set by the browser and cannot be forged by page script.
 		switch r.Header.Get("Sec-Fetch-Site") {
@@ -220,6 +244,20 @@ func (s *Server) requireCSRF(next http.Handler) http.Handler {
 	})
 }
 
+// appOrigins are where the iOS app's interface is served from. Capacitor loads
+// the bundled build on this scheme inside WKWebView, so every request the app
+// makes to a server arrives from here, whichever server it is.
+var appOrigins = []string{"capacitor://localhost"}
+
+func isAppOrigin(origin string) bool {
+	for _, o := range appOrigins {
+		if origin == o {
+			return true
+		}
+	}
+	return false
+}
+
 func (s *Server) isOwnOrigin(origin string) bool {
 	if strings.EqualFold(origin, s.cfg.BaseURL) {
 		return true
diff --git a/internal/httpapi/sessions_handlers.go b/internal/httpapi/sessions_handlers.go
index 43c478f..21db515 100644
--- a/internal/httpapi/sessions_handlers.go
+++ b/internal/httpapi/sessions_handlers.go
@@ -23,8 +23,11 @@ type sessionJSON struct {
 	// Device is a summary; UserAgent is what it was summarised from. Both, because
 	// the summary is what you read and the original is what settles the question
 	// when the summary is not enough.
-	Device     string `json:"device"`
-	UserAgent  string `json:"user_agent"`
+	Device    string `json:"device"`
+	UserAgent string `json:"user_agent"`
+	// Client is "web" or "app". An app session slides — its expires_at moves
+	// forward each time it is used — where a browser's is fixed.
+	Client     string `json:"client"`
 	IP         string `json:"ip"`
 	CreatedAt  string `json:"created_at"`
 	LastSeenAt string `json:"last_seen_at"`
@@ -47,11 +50,17 @@ func (s *Server) handleListSessions(w http.ResponseWriter, r *http.Request) {
 
 	out := make([]sessionJSON, 0, len(sessions))
 	for _, sess := range sessions {
+		// The app names itself; a browser is described from its user agent.
+		device := sess.DeviceName
+		if device == "" {
+			device = describeUserAgent(sess.UA)
+		}
 		out = append(out, sessionJSON{
 			ID:         sess.ID,
 			Current:    current != nil && sess.ID == current.ID,
-			Device:     describeUserAgent(sess.UA),
+			Device:     device,
 			UserAgent:  sess.UA,
+			Client:     sess.Client,
 			IP:         sess.IP,
 			CreatedAt:  sess.CreatedAt.Format(time.RFC3339),
 			LastSeenAt: sess.LastSeenAt.Format(time.RFC3339),
diff --git a/internal/store/migrations/0037_sessioner_fra_en_app.sql b/internal/store/migrations/0037_sessioner_fra_en_app.sql
new file mode 100644
index 0000000..674f333
--- /dev/null
+++ b/internal/store/migrations/0037_sessioner_fra_en_app.sql
@@ -0,0 +1,19 @@
+-- Sessioner fra en app.
+--
+-- En app logger ind som en browser gør, med adgangskode og evt. kode, og får en
+-- almindelig session. Forskellen er transporten: tokenet kommer i svaret og sendes
+-- som `Authorization: Bearer`, fordi en app, der henter sit UI fra sig selv, ikke
+-- deler origin med serveren og derfor aldrig får cookien tilbage. At det er en
+-- SESSION og ikke et API-token er hele pointen: den står i listen over enheder,
+-- kan logges ud derfra, og den når indstillingerne for 2FA og nøgler, som et
+-- token med vilje ikke gør.
+--
+-- device_name er det navn, appen giver sig selv ("Kristians iPhone"), så listen
+-- siger noget, en person genkender. idle_ttl er sekunder: større end 0 betyder, at
+-- sessionen glider — hver gang den bruges, flyttes udløbet frem. En browser får
+-- 0 og sin faste levetid som før; en telefon, man har i lommen hver dag, må ikke
+-- logge sig selv ud hver 30. dag, men en telefon, der ligger i en skuffe et halvt
+-- år, skal.
+ALTER TABLE sessions ADD COLUMN client TEXT NOT NULL DEFAULT 'web';
+ALTER TABLE sessions ADD COLUMN device_name TEXT NOT NULL DEFAULT '';
+ALTER TABLE sessions ADD COLUMN idle_ttl INTEGER NOT NULL DEFAULT 0;
diff --git a/internal/store/sessions.go b/internal/store/sessions.go
index c8b0fe5..31211fc 100644
--- a/internal/store/sessions.go
+++ b/internal/store/sessions.go
@@ -15,9 +15,36 @@ type Session struct {
 	UA          string
 	IP          string
 	PendingTOTP bool
-	CreatedAt   time.Time
-	LastSeenAt  time.Time
-	ExpiresAt   time.Time
+	// Client is "web" for a browser and "app" for the iOS app, which carries its
+	// session as a bearer token rather than a cookie. DeviceName is what the app
+	// calls itself; a browser has none and is described from its user agent.
+	Client     string
+	DeviceName string
+	// IdleTTL above zero makes the session slide: each use moves ExpiresAt to
+	// IdleTTL from now. Zero is the fixed lifetime a browser session has always had.
+	IdleTTL    time.Duration
+	CreatedAt  time.Time
+	LastSeenAt time.Time
+	ExpiresAt  time.Time
+}
+
+const sessionColumns = `id, user_id, ua, ip, pending_totp, client, device_name, idle_ttl,
+	created_at, last_seen_at, expires_at`
+
+func scanSession(row interface{ Scan(...any) error }) (*Session, error) {
+	var s Session
+	var pending int
+	var idle, created, lastSeen, expires int64
+	if err := row.Scan(&s.ID, &s.UserID, &s.UA, &s.IP, &pending, &s.Client, &s.DeviceName, &idle,
+		&created, &lastSeen, &expires); err != nil {
+		return nil, err
+	}
+	s.PendingTOTP = pending == 1
+	s.IdleTTL = time.Duration(idle) * time.Second
+	s.CreatedAt = time.Unix(created, 0).UTC()
+	s.LastSeenAt = time.Unix(lastSeen, 0).UTC()
+	s.ExpiresAt = time.Unix(expires, 0).UTC()
+	return &s, nil
 }
 
 // CreateSession issues a session and returns the value to put in the cookie.
@@ -40,6 +67,7 @@ func (db *DB) CreateSession(ctx context.Context, userID, ua, ip string, ttl time
 		UA:          truncate(ua, 500),
 		IP:          truncate(ip, 100),
 		PendingTOTP: pendingTOTP,
+		Client:      "web",
 		CreatedAt:   now,
 		LastSeenAt:  now,
 		ExpiresAt:   now.Add(ttl),
@@ -63,13 +91,8 @@ func (db *DB) CreateSession(ctx context.Context, userID, ua, ip string, ttl time
 func (db *DB) SessionByToken(ctx context.Context, token string) (*Session, *User, error) {
 	id := auth.HashToken(token)
 
-	var s Session
-	var pending int
-	var created, lastSeen, expires int64
-	err := db.QueryRowContext(ctx,
-		`SELECT id, user_id, ua, ip, pending_totp, created_at, last_seen_at, expires_at
-		 FROM sessions WHERE id = ?`, id).
-		Scan(&s.ID, &s.UserID, &s.UA, &s.IP, &pending, &created, &lastSeen, &expires)
+	s, err := scanSession(db.QueryRowContext(ctx,
+		`SELECT `+sessionColumns+` FROM sessions WHERE id = ?`, id))
 	if errors.Is(err, sql.ErrNoRows) {
 		return nil, nil, ErrNotFound
 	}
@@ -77,11 +100,6 @@ func (db *DB) SessionByToken(ctx context.Context, token string) (*Session, *User
 		return nil, nil, err
 	}
 
-	s.PendingTOTP = pending == 1
-	s.CreatedAt = time.Unix(created, 0).UTC()
-	s.LastSeenAt = time.Unix(lastSeen, 0).UTC()
-	s.ExpiresAt = time.Unix(expires, 0).UTC()
-
 	if time.Now().After(s.ExpiresAt) {
 		_, _ = db.ExecContext(ctx, `DELETE FROM sessions WHERE id = ?`, s.ID)
 		return nil, nil, ErrNotFound
@@ -95,20 +113,47 @@ func (db *DB) SessionByToken(ctx context.Context, token string) (*Session, *User
 	// last_seen_at drives the session list in settings ("this device, 2 minutes
 	// ago"). It is written at most once a minute: every request would be a write
 	// per request, which on SQLite means a write lock per request.
+	//
+	// A sliding session moves its end in the same write, and only then: its
+	// expiry is therefore accurate to the minute, which is far finer than the
+	// months it is measured in.
 	if time.Since(s.LastSeenAt) > time.Minute {
-		_, _ = db.ExecContext(ctx,
-			`UPDATE sessions SET last_seen_at = ? WHERE id = ?`, time.Now().Unix(), s.ID)
+		now := time.Now()
+		if s.IdleTTL > 0 && !s.PendingTOTP {
+			s.ExpiresAt = now.Add(s.IdleTTL).UTC()
+			_, _ = db.ExecContext(ctx,
+				`UPDATE sessions SET last_seen_at = ?, expires_at = ? WHERE id = ?`,
+				now.Unix(), s.ExpiresAt.Unix(), s.ID)
+		} else {
+			_, _ = db.ExecContext(ctx,
+				`UPDATE sessions SET last_seen_at = ? WHERE id = ?`, now.Unix(), s.ID)
+		}
 	}
-	return &s, user, nil
+	return s, user, nil
+}
+
+// MarkAppSession records that a session belongs to the iOS app, what the device
+// calls itself, and how long it may sit unused (see Session.IdleTTL).
+//
+// A login still waiting on its code is marked with idle 0, so it keeps its ten
+// minutes; PromoteSession turns sliding on once the code is in.
+func (db *DB) MarkAppSession(ctx context.Context, sessionID, deviceName string, idle time.Duration) error {
+	_, err := db.ExecContext(ctx,
+		`UPDATE sessions SET client = 'app', device_name = ?, idle_ttl = ? WHERE id = ?`,
+		truncate(deviceName, 100), int64(idle/time.Second), sessionID)
+	return err
 }
 
 // PromoteSession completes a two-step login: the session stops being pending and
 // its clock restarts, so the full lifetime is counted from finishing the login and
 // not from typing the password.
-func (db *DB) PromoteSession(ctx context.Context, sessionID string, ttl time.Duration) error {
+//
+// idle above zero makes the finished session slide (see Session.IdleTTL); a
+// browser passes zero.
+func (db *DB) PromoteSession(ctx context.Context, sessionID string, ttl, idle time.Duration) error {
 	res, err := db.ExecContext(ctx,
-		`UPDATE sessions SET pending_totp = 0, expires_at = ? WHERE id = ? AND pending_totp = 1`,
-		time.Now().Add(ttl).Unix(), sessionID)
+		`UPDATE sessions SET pending_totp = 0, expires_at = ?, idle_ttl = ? WHERE id = ? AND pending_totp = 1`,
+		time.Now().Add(ttl).Unix(), int64(idle/time.Second), sessionID)
 	if err != nil {
 		return err
 	}
@@ -147,7 +192,7 @@ func (db *DB) DeleteUserSessions(ctx context.Context, userID string) error {
 
 func (db *DB) ListSessions(ctx context.Context, userID string) ([]Session, error) {
 	rows, err := db.QueryContext(ctx,
-		`SELECT id, user_id, ua, ip, pending_totp, created_at, last_seen_at, expires_at
+		`SELECT `+sessionColumns+`
 		 FROM sessions WHERE user_id = ? AND pending_totp = 0 ORDER BY last_seen_at DESC`, userID)
 	if err != nil {
 		return nil, err
@@ -156,17 +201,11 @@ func (db *DB) ListSessions(ctx context.Context, userID string) ([]Session, error
 
 	var out []Session
 	for rows.Next() {
-		var s Session
-		var pending int
-		var created, lastSeen, expires int64
-		if err := rows.Scan(&s.ID, &s.UserID, &s.UA, &s.IP, &pending, &created, &lastSeen, &expires); err != nil {
+		s, err := scanSession(rows)
+		if err != nil {
 			return nil, err
 		}
-		s.PendingTOTP = pending == 1
-		s.CreatedAt = time.Unix(created, 0).UTC()
-		s.LastSeenAt = time.Unix(lastSeen, 0).UTC()
-		s.ExpiresAt = time.Unix(expires, 0).UTC()
-		out = append(out, s)
+		out = append(out, *s)
 	}
 	return out, rows.Err()
 }