diff --git a/internal/app/seal.go b/internal/app/seal.go
index d71553a..3c49584 100644
--- a/internal/app/seal.go
+++ b/internal/app/seal.go
@@ -218,7 +218,7 @@ func (a *app) Seal(config *fst.Config) error {
 	// open process state store
 	// the simple store only starts holding an open file after first action
 	// store activity begins after Start is called and must end before Wait
-	seal.store = state.NewSimple(seal.RunDirPath, seal.sys.user.as)
+	seal.store = state.NewMulti(seal.RunDirPath)
 
 	// initialise system interface with full uid
 	seal.sys.I = system.New(seal.sys.user.uid)
diff --git a/internal/app/start.go b/internal/app/start.go
index 1ebc94f..8de7821 100644
--- a/internal/app/start.go
+++ b/internal/app/start.go
@@ -76,8 +76,8 @@ func (a *app) Start() error {
 
 		// register process state
 		var err0 = new(StateStoreError)
-		err0.Inner, err0.DoErr = a.seal.store.Do(func(b state.Backend) {
-			err0.InnerErr = b.Save(&sd)
+		err0.Inner, err0.DoErr = a.seal.store.Do(a.seal.sys.user.aid, func(c state.Cursor) {
+			err0.InnerErr = c.Save(&sd)
 		})
 		a.seal.sys.saveState = true
 		return err0.equiv("cannot save process state:")
@@ -199,11 +199,11 @@ func (a *app) Wait() (int, error) {
 
 	// update store and revert app setup transaction
 	e := new(StateStoreError)
-	e.Inner, e.DoErr = a.seal.store.Do(func(b state.Backend) {
+	e.Inner, e.DoErr = a.seal.store.Do(a.seal.sys.user.aid, func(b state.Cursor) {
 		e.InnerErr = func() error {
 			// destroy defunct state entry
 			if cmd := a.shim.Unwrap(); cmd != nil && a.seal.sys.saveState {
-				if err := b.Destroy(cmd.Process.Pid); err != nil {
+				if err := b.Destroy(*a.id); err != nil {
 					return err
 				}
 			}
diff --git a/internal/state/multi.go b/internal/state/multi.go
index f014b3d..16afc08 100644
--- a/internal/state/multi.go
+++ b/internal/state/multi.go
@@ -3,54 +3,135 @@ package state
 import (
 	"encoding/gob"
 	"errors"
+	"fmt"
 	"io/fs"
 	"os"
 	"path"
 	"strconv"
 	"sync"
 	"syscall"
+
+	"git.ophivana.moe/security/fortify/fst"
+	"git.ophivana.moe/security/fortify/internal/fmsg"
 )
 
 // fine-grained locking and access
 type multiStore struct {
-	path []string
+	base string
 
-	// created/opened by prepare
-	lockfile *os.File
-	// enforce prepare method
-	init sync.Once
-	// error returned by prepare
-	initErr error
+	// initialised backends
+	backends *sync.Map
 
-	lock sync.Mutex
+	lock sync.RWMutex
 }
 
-func (s *multiStore) Do(f func(b Backend)) (bool, error) {
-	s.init.Do(s.prepare)
-	if s.initErr != nil {
-		return false, s.initErr
+func (s *multiStore) Do(aid int, f func(c Cursor)) (bool, error) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+
+	// load or initialise new backend
+	b := new(multiBackend)
+	if v, ok := s.backends.LoadOrStore(aid, b); ok {
+		b = v.(*multiBackend)
+	} else {
+		b.lock.Lock()
+		b.path = path.Join(s.base, strconv.Itoa(aid))
+
+		// ensure directory
+		if err := os.MkdirAll(b.path, 0700); err != nil && !errors.Is(err, fs.ErrExist) {
+			s.backends.CompareAndDelete(aid, b)
+			return false, err
+		}
+
+		// open locker file
+		if l, err := os.OpenFile(b.path+".lock", os.O_RDWR|os.O_CREATE, 0600); err != nil {
+			s.backends.CompareAndDelete(aid, b)
+			return false, err
+		} else {
+			b.lockfile = l
+		}
+		b.lock.Unlock()
 	}
 
-	s.lock.Lock()
-	defer s.lock.Unlock()
-
-	// lock store
-	if err := s.lockFile(); err != nil {
+	// lock backend
+	if err := b.lockFile(); err != nil {
 		return false, err
 	}
 
-	// initialise new backend for caller
-	b := new(multiBackend)
-	b.path = path.Join(s.path...)
+	// expose backend methods without exporting the pointer
+	c := new(struct{ *multiBackend })
+	c.multiBackend = b
 	f(b)
-	// disable backend
-	b.lock.Lock()
+	// disable access to the backend on a best-effort basis
+	c.multiBackend = nil
 
-	// unlock store
-	return true, s.unlockFile()
+	// unlock backend
+	return true, b.unlockFile()
 }
 
-func (s *multiStore) lockFileAct(lt int) (err error) {
+func (s *multiStore) List() ([]int, error) {
+	var entries []os.DirEntry
+
+	// read base directory to get all aids
+	if v, err := os.ReadDir(s.base); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return nil, err
+	} else {
+		entries = v
+	}
+
+	aidsBuf := make([]int, 0, len(entries))
+	for _, e := range entries {
+		// skip non-directories
+		if !e.IsDir() {
+			fmsg.VPrintf("skipped non-directory entry %q", e.Name())
+			continue
+		}
+
+		// skip non-numerical names
+		if v, err := strconv.Atoi(e.Name()); err != nil {
+			fmsg.VPrintf("skipped non-aid entry %q", e.Name())
+			continue
+		} else {
+			if v < 0 || v > 9999 {
+				fmsg.VPrintf("skipped out of bounds entry %q", e.Name())
+				continue
+			}
+
+			aidsBuf = append(aidsBuf, v)
+		}
+	}
+
+	return append([]int(nil), aidsBuf...), nil
+}
+
+func (s *multiStore) Close() error {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	var errs []error
+	s.backends.Range(func(_, value any) bool {
+		b := value.(*multiBackend)
+		errs = append(errs, b.close())
+		return true
+	})
+
+	return errors.Join(errs...)
+}
+
+type multiBackend struct {
+	path string
+
+	// created/opened by prepare
+	lockfile *os.File
+
+	lock sync.RWMutex
+}
+
+func (b *multiBackend) filename(id *fst.ID) string {
+	return path.Join(b.path, id.String())
+}
+
+func (b *multiBackend) lockFileAct(lt int) (err error) {
 	op := "LockAct"
 	switch lt {
 	case syscall.LOCK_EX:
@@ -60,7 +141,7 @@ func (s *multiStore) lockFileAct(lt int) (err error) {
 	}
 
 	for {
-		err = syscall.Flock(int(s.lockfile.Fd()), lt)
+		err = syscall.Flock(int(b.lockfile.Fd()), lt)
 		if !errors.Is(err, syscall.EINTR) {
 			break
 		}
@@ -68,103 +149,80 @@ func (s *multiStore) lockFileAct(lt int) (err error) {
 	if err != nil {
 		return &fs.PathError{
 			Op:   op,
-			Path: s.lockfile.Name(),
+			Path: b.lockfile.Name(),
 			Err:  err,
 		}
 	}
 	return nil
 }
 
-func (s *multiStore) lockFile() error {
-	return s.lockFileAct(syscall.LOCK_EX)
+func (b *multiBackend) lockFile() error {
+	return b.lockFileAct(syscall.LOCK_EX)
 }
 
-func (s *multiStore) unlockFile() error {
-	return s.lockFileAct(syscall.LOCK_UN)
-}
-
-func (s *multiStore) prepare() {
-	s.initErr = func() error {
-		prefix := path.Join(s.path...)
-		// ensure directory
-		if err := os.MkdirAll(prefix, 0700); err != nil && !errors.Is(err, fs.ErrExist) {
-			return err
-		}
-
-		// open locker file
-		if f, err := os.OpenFile(prefix+".lock", os.O_RDWR|os.O_CREATE, 0600); err != nil {
-			return err
-		} else {
-			s.lockfile = f
-		}
-
-		return nil
-	}()
-}
-
-func (s *multiStore) Close() error {
-	s.lock.Lock()
-	defer s.lock.Unlock()
-
-	err := s.lockfile.Close()
-	if err == nil || errors.Is(err, os.ErrInvalid) || errors.Is(err, os.ErrClosed) {
-		return nil
-	}
-	return err
-}
-
-type multiBackend struct {
-	path string
-
-	lock sync.RWMutex
-}
-
-func (b *multiBackend) filename(pid int) string {
-	return path.Join(b.path, strconv.Itoa(pid))
+func (b *multiBackend) unlockFile() error {
+	return b.lockFileAct(syscall.LOCK_UN)
 }
 
 // reads all launchers in simpleBackend
 // file contents are ignored if decode is false
-func (b *multiBackend) load(decode bool) ([]*State, error) {
+func (b *multiBackend) load(decode bool) (Entries, error) {
 	b.lock.RLock()
 	defer b.lock.RUnlock()
 
-	var (
-		r []*State
-		f *os.File
-	)
-
-	// read directory contents, should only contain files named after PIDs
+	// read directory contents, should only contain files named after ids
+	var entries []os.DirEntry
 	if pl, err := os.ReadDir(b.path); err != nil {
 		return nil, err
 	} else {
-		for _, e := range pl {
-			// run in a function to better handle file closing
-			if err = func() error {
-				// open state file for reading
-				if f, err = os.Open(path.Join(b.path, e.Name())); err != nil {
-					return err
-				} else {
-					defer func() {
-						if f.Close() != nil {
-							// unreachable
-							panic("foreign state file closed prematurely")
-						}
-					}()
+		entries = pl
+	}
 
-					var s State
-					r = append(r, &s)
+	// allocate as if every entry is valid
+	// since that should be the case assuming no external interference happens
+	r := make(Entries, len(entries))
 
-					// append regardless, but only parse if required, used to implement Len
-					if decode {
-						return gob.NewDecoder(f).Decode(&s)
-					} else {
-						return nil
+	for _, e := range entries {
+		if e.IsDir() {
+			return nil, fmt.Errorf("unexpected directory %q in store", e.Name())
+		}
+
+		id := new(fst.ID)
+		if err := fst.ParseAppID(id, e.Name()); err != nil {
+			return nil, err
+		}
+
+		// run in a function to better handle file closing
+		if err := func() error {
+			// open state file for reading
+			if f, err := os.Open(path.Join(b.path, e.Name())); err != nil {
+				return err
+			} else {
+				defer func() {
+					if f.Close() != nil {
+						// unreachable
+						panic("foreign state file closed prematurely")
+					}
+				}()
+
+				s := new(State)
+				r[*id] = s
+
+				// append regardless, but only parse if required, used to implement Len
+				if decode {
+					if err = gob.NewDecoder(f).Decode(s); err != nil {
+						return err
+					}
+
+					if s.ID != *id {
+						return fmt.Errorf("state entry %s has unexpected id %s", id, &s.ID)
 					}
 				}
-			}(); err != nil {
-				return nil, err
+
+				return nil
 			}
+		}(); err != nil {
+			return nil, err
 		}
 	}
 
@@ -180,7 +238,7 @@ func (b *multiBackend) Save(state *State) error {
 		return errors.New("state does not contain config")
 	}
 
-	statePath := b.filename(state.PID)
+	statePath := b.filename(&state.ID)
 
 	// create and open state data file
 	if f, err := os.OpenFile(statePath, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600); err != nil {
@@ -197,14 +255,14 @@ func (b *multiBackend) Save(state *State) error {
 	}
 }
 
-func (b *multiBackend) Destroy(pid int) error {
+func (b *multiBackend) Destroy(id fst.ID) error {
 	b.lock.Lock()
 	defer b.lock.Unlock()
 
-	return os.Remove(b.filename(pid))
+	return os.Remove(b.filename(&id))
 }
 
-func (b *multiBackend) Load() ([]*State, error) {
+func (b *multiBackend) Load() (Entries, error) {
 	return b.load(true)
 }
 
@@ -214,9 +272,21 @@ func (b *multiBackend) Len() (int, error) {
 	return len(rn), err
 }
 
-// NewSimple returns an instance of a file-based store.
-func NewSimple(runDir string, prefix ...string) Store {
+func (b *multiBackend) close() error {
+	b.lock.Lock()
+	defer b.lock.Unlock()
+
+	err := b.lockfile.Close()
+	if err == nil || errors.Is(err, os.ErrInvalid) || errors.Is(err, os.ErrClosed) {
+		return nil
+	}
+	return err
+}
+
+// NewMulti returns an instance of the multi-file store.
+func NewMulti(runDir string) Store {
 	b := new(multiStore)
-	b.path = append([]string{runDir, "state"}, prefix...)
+	b.base = path.Join(runDir, "state")
+	b.backends = new(sync.Map)
 	return b
 }
diff --git a/internal/state/multi_test.go b/internal/state/multi_test.go
new file mode 100644
index 0000000..13b2937
--- /dev/null
+++ b/internal/state/multi_test.go
@@ -0,0 +1,11 @@
+package state_test
+
+import (
+	"testing"
+
+	"git.ophivana.moe/security/fortify/internal/state"
+)
+
+func TestMulti(t *testing.T) {
+	testStore(t, state.NewMulti(t.TempDir()))
+}
diff --git a/internal/state/print.go b/internal/state/print.go
index 485fd67..2309bd6 100644
--- a/internal/state/print.go
+++ b/internal/state/print.go
@@ -1,11 +1,8 @@
 package state
 
 import (
-	"errors"
 	"fmt"
 	"os"
-	"path"
-	"strconv"
 	"strings"
 	"text/tabwriter"
 	"time"
@@ -18,45 +15,31 @@ import (
 // in an implementation-specific way.
 func MustPrintLauncherStateSimpleGlobal(w **tabwriter.Writer, runDir string) {
 	now := time.Now().UTC()
+	s := NewMulti(runDir)
 
 	// read runtime directory to get all UIDs
-	if dirs, err := os.ReadDir(path.Join(runDir, "state")); err != nil && !errors.Is(err, os.ErrNotExist) {
-		fmsg.Fatal("cannot read runtime directory:", err)
+	if aids, err := s.List(); err != nil {
+		fmsg.Fatal("cannot list store:", err)
 	} else {
-		for _, e := range dirs {
-			// skip non-directories
-			if !e.IsDir() {
-				fmsg.VPrintf("skipped non-directory entry %q", e.Name())
-				continue
-			}
-
-			// skip non-numerical names
-			if _, err = strconv.Atoi(e.Name()); err != nil {
-				fmsg.VPrintf("skipped non-uid entry %q", e.Name())
-				continue
-			}
-
-			// obtain temporary store
-			s := NewSimple(runDir, e.Name()).(*multiStore)
-
+		for _, aid := range aids {
 			// print states belonging to this store
-			s.mustPrintLauncherState(w, now)
-
-			// mustPrintLauncherState causes store activity so store needs to be closed
-			if err = s.Close(); err != nil {
-				fmsg.Printf("cannot close store for user %q: %s", e.Name(), err)
-			}
+			s.(*multiStore).mustPrintLauncherState(aid, w, now)
 		}
 	}
+
+	// mustPrintLauncherState causes store activity so store needs to be closed
+	if err := s.Close(); err != nil {
+		fmsg.Printf("cannot close store: %v", err)
+	}
 }
 
-func (s *multiStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time) {
+func (s *multiStore) mustPrintLauncherState(aid int, w **tabwriter.Writer, now time.Time) {
 	var innerErr error
 
-	if ok, err := s.Do(func(b Backend) {
+	if ok, err := s.Do(aid, func(c Cursor) {
 		innerErr = func() error {
 			// read launcher states
-			states, err := b.Load()
+			states, err := c.Load()
 			if err != nil {
 				return err
 			}
@@ -111,25 +94,25 @@ func (s *multiStore) mustPrintLauncherState(w **tabwriter.Writer, now time.Time)
 				}
 
 				if !fmsg.Verbose() {
-					_, _ = fmt.Fprintf(*w, "\t%d\t%s\t%s\t%s\t%s\n",
-						state.PID, s.path[len(s.path)-1], now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "), cs)
+					_, _ = fmt.Fprintf(*w, "\t%d\t%d\t%s\t%s\t%s\n",
+						state.PID, aid, now.Sub(state.Time).Round(time.Second).String(), strings.TrimPrefix(ets.String(), ", "), cs)
 				} else {
 					// emit argv instead when verbose
-					_, _ = fmt.Fprintf(*w, "\t%d\t%s\t%s\n",
-						state.PID, s.path[len(s.path)-1], state.ID)
+					_, _ = fmt.Fprintf(*w, "\t%d\t%d\t%s\n",
+						state.PID, aid, state.ID)
 				}
 			}
 
 			return nil
 		}()
 	}); err != nil {
-		fmsg.Printf("cannot perform action on store %q: %s", path.Join(s.path...), err)
+		fmsg.Printf("cannot perform action on app %d: %v", aid, err)
 		if !ok {
 			fmsg.Fatal("store faulted before printing")
 		}
 	}
 
 	if innerErr != nil {
-		fmsg.Fatalf("cannot print launcher state for store %q: %s", path.Join(s.path...), innerErr)
+		fmsg.Fatalf("cannot print launcher state of app %d: %s", aid, innerErr)
 	}
 }
diff --git a/internal/state/state.go b/internal/state/state.go
index cf345aa..ccc44b1 100644
--- a/internal/state/state.go
+++ b/internal/state/state.go
@@ -6,21 +6,27 @@ import (
 	"git.ophivana.moe/security/fortify/fst"
 )
 
+type Entries map[fst.ID]*State
+
 type Store interface {
 	// Do calls f exactly once and ensures store exclusivity until f returns.
 	// Returns whether f is called and any errors during the locking process.
-	// Backend provided to f becomes invalid as soon as f returns.
-	Do(f func(b Backend)) (bool, error)
+	// Cursor provided to f becomes invalid as soon as f returns.
+	Do(aid int, f func(c Cursor)) (ok bool, err error)
+
+	// List queries the store and returns a list of aids known to the store.
+	// Note that some or all returned aids might not have any active apps.
+	List() (aids []int, err error)
 
 	// Close releases any resources held by Store.
 	Close() error
 }
 
-// Backend provides access to the store
-type Backend interface {
+// Cursor provides access to the store
+type Cursor interface {
 	Save(state *State) error
-	Destroy(pid int) error
-	Load() ([]*State, error)
+	Destroy(id fst.ID) error
+	Load() (Entries, error)
 	Len() (int, error)
 }
 
diff --git a/internal/state/state_test.go b/internal/state/state_test.go
new file mode 100644
index 0000000..0a4ba57
--- /dev/null
+++ b/internal/state/state_test.go
@@ -0,0 +1,126 @@
+package state_test
+
+import (
+	"math/rand/v2"
+	"reflect"
+	"slices"
+	"testing"
+	"time"
+
+	"git.ophivana.moe/security/fortify/fst"
+	"git.ophivana.moe/security/fortify/internal/state"
+)
+
+func testStore(t *testing.T, s state.Store) {
+	t.Run("list empty store", func(t *testing.T) {
+		if aids, err := s.List(); err != nil {
+			t.Fatalf("List: error = %v", err)
+		} else if len(aids) != 0 {
+			t.Fatalf("List: aids = %#v", aids)
+		}
+	})
+
+	const (
+		insertEntryChecked = iota
+		insertEntryNoCheck
+		insertEntryOtherApp
+
+		tl
+	)
+
+	var tc [tl]state.State
+	for i := 0; i < tl; i++ {
+		makeState(t, &tc[i])
+	}
+
+	do := func(aid int, f func(c state.Cursor)) {
+		if ok, err := s.Do(aid, f); err != nil {
+			t.Fatalf("Do: ok = %v, error = %v", ok, err)
+		}
+	}
+
+	insert := func(i, aid int) {
+		do(aid, func(c state.Cursor) {
+			if err := c.Save(&tc[i]); err != nil {
+				t.Fatalf("Save(&tc[%v]): error = %v", i, err)
+			}
+		})
+	}
+
+	check := func(i, aid int) {
+		do(aid, func(c state.Cursor) {
+			if entries, err := c.Load(); err != nil {
+				t.Fatalf("Load: error = %v", err)
+			} else if got, ok := entries[tc[i].ID]; !ok {
+				t.Fatalf("Load: entry %s missing",
+					&tc[i].ID)
+			} else {
+				got.Time = tc[i].Time
+				if !reflect.DeepEqual(got, &tc[i]) {
+					t.Fatalf("Load: entry %s got %#v, want %#v",
+						&tc[i].ID, got, &tc[i])
+				}
+			}
+		})
+	}
+
+	t.Run("insert entry checked", func(t *testing.T) {
+		insert(insertEntryChecked, 0)
+		check(insertEntryChecked, 0)
+	})
+
+	t.Run("insert entry unchecked", func(t *testing.T) {
+		insert(insertEntryNoCheck, 0)
+	})
+
+	t.Run("insert entry different aid", func(t *testing.T) {
+		insert(insertEntryOtherApp, 1)
+		check(insertEntryOtherApp, 1)
+	})
+
+	t.Run("check previous insertion", func(t *testing.T) {
+		check(insertEntryNoCheck, 0)
+	})
+
+	t.Run("list aids", func(t *testing.T) {
+		if aids, err := s.List(); err != nil {
+			t.Fatalf("List: error = %v", err)
+		} else {
+			slices.Sort(aids)
+			want := []int{0, 1}
+			if slices.Compare(aids, want) != 0 {
+				t.Fatalf("List() = %#v, want %#v", aids, want)
+			}
+		}
+	})
+
+	t.Run("clear aid 1", func(t *testing.T) {
+		do(1, func(c state.Cursor) {
+			if err := c.Destroy(tc[insertEntryOtherApp].ID); err != nil {
+				t.Fatalf("Destroy: error = %v", err)
+			}
+		})
+		do(1, func(c state.Cursor) {
+			if l, err := c.Len(); err != nil {
+				t.Fatalf("Len: error = %v", err)
+			} else if l != 0 {
+				t.Fatalf("Len() = %d, want 0", l)
+			}
+		})
+	})
+
+	t.Run("close store", func(t *testing.T) {
+		if err := s.Close(); err != nil {
+			t.Fatalf("Close: error = %v", err)
+		}
+	})
+}
+
+func makeState(t *testing.T, s *state.State) {
+	if err := fst.NewAppID(&s.ID); err != nil {
+		t.Fatalf("cannot create dummy state: %v", err)
+	}
+	s.Config = fst.Template()
+	s.PID = rand.Int()
+	s.Time = time.Now()
+}
diff --git a/test.nix b/test.nix
index 00bcba4..12384bc 100644
--- a/test.nix
+++ b/test.nix
@@ -214,5 +214,8 @@ nixosTest {
     swaymsg("exit", succeed=False)
     machine.wait_until_fails("pgrep -x sway")
     machine.wait_for_file("/tmp/sway-exit-ok")
+
+    # Print fortify runDir contents:
+    print(machine.succeed("find /run/user/1000/fortify"))
   '';
 }