Pin compose example to v0.2.3

README.md

@@ -134,6 +134,15 @@ answers on the port, gpu-turnstile just uses it instead of spawning
 instance already holds the port when you open the desktop app, the
 desktop's server is the one that fails to bind.
 
+One catch when gpu-turnstile runs as a service: the sandboxed service
+account may not enter your user profile, so a ComfyUI install under
+`C:\Users\...` (or `/home/...`) fails with "Access is denied".
+`--install-service` fixes that automatically — it grants
+`NT SERVICE\gpu-turnstile` recursive access to `COMFY_DIR` on Windows and
+adds a `BindPaths=` to the systemd unit on Linux. Re-run it after changing
+`COMFY_DIR`; or grant by hand from an admin shell:
+`icacls "<COMFY_DIR>" /grant "NT SERVICE\gpu-turnstile:(OI)(CI)M" /T`.
+
 ## Game detection
 
 Want to game on the same GPU without Ollama/ComfyUI squatting on the VRAM?

SPEC.md

@@ -159,6 +159,14 @@ files are flagged in the startup log.
 - Its stdout/stderr is forwarded to the log at INFO. The health check
   skips the intentionally-stopped/starting states; a failed probe while
   the process is alive and was previously ready is logged as DOWN.
+- **Permissions**: the service account is sandboxed (Windows virtual
+  account, systemd `DynamicUser`), so a ComfyUI install inside a user
+  profile is off-limits by default. `--install-service` opens it up —
+  a recursive ACL grant for `NT SERVICE\gpu-turnstile` on Windows, a
+  `BindPaths=` in the unit on Linux — reading `COMFY_DIR` from the config
+  it installs. Re-run `--install-service` after changing `COMFY_DIR`, or
+  grant by hand (admin shell):
+  `icacls "<COMFY_DIR>" /grant "NT SERVICE\gpu-turnstile:(OI)(CI)M" /T`.
 
 ## Game detection (foreign GPU holders)
 

cmd/gpu-turnstile/main.go

@@ -17,11 +17,13 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
 	"gpu-turnstile/internal/comfy"
 	"gpu-turnstile/internal/config"
+	"gpu-turnstile/internal/control"
 	"gpu-turnstile/internal/game"
 	"gpu-turnstile/internal/lock"
 	"gpu-turnstile/internal/metrics"
@@ -39,6 +41,11 @@ var version = "dev"
 // process: a signed update has been staged and the GPU lock is idle.
 const exitCodeUpdate = 3
 
+// exitCodeStaged is returned by an elevated --force-update child when it
+// staged a new binary, so the non-elevated parent can tell "updated" from
+// "up to date" (it cannot see the child's console).
+const exitCodeStaged = 4
+
 // stdoutIsTerminal reports whether stdout is a console (char device), as
 // opposed to a pipe or file — which is what Docker containers and services
 // see.
@@ -51,7 +58,7 @@ func stdoutIsTerminal() bool {
 // --install-service / --remove-service switches, --no-copy, -h/--help,
 // -v/--version, --force-update and the hidden --elevated-child marker from
 // args.
-func parseFlags(args []string) (configPath string, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild bool, rest []string) {
+func parseFlags(args []string) (configPath string, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild bool, rest []string) {
 	rest = args[:0]
 	for i := 0; i < len(args); i++ {
 		switch {
@@ -72,13 +79,15 @@ func parseFlags(args []string) (configPath string, install, remove, noCopy, help
 			showVersion = true
 		case args[i] == "--force-update" || args[i] == "-force-update":
 			forceUpdate = true
+		case args[i] == "--update-now" || args[i] == "-update-now":
+			updateNow = true
 		case args[i] == "--elevated-child":
 			elevatedChild = true
 		default:
 			rest = append(rest, args[i])
 		}
 	}
-	return configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, rest
+	return configPath, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild, rest
 }
 
 // versionLine is printed at the top of every help and error screen.
@@ -93,6 +102,9 @@ Usage:
   gpu-turnstile -v | --version                                print just the version
   gpu-turnstile --force-update                                check for a signed update now,
                                                               apply it and restart the service
+                                                              (no admin needed when the service runs)
+  gpu-turnstile --update-now                                  like --force-update, but only
+                                                              through the running service
   gpu-turnstile -h | --help                                   this help
 
 Options:
@@ -123,12 +135,12 @@ func fatalUsage(format string, args ...any) {
 }
 
 func main() {
-	configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, args := parseFlags(os.Args[1:])
+	configPath, install, remove, noCopy, help, showVersion, forceUpdate, updateNow, elevatedChild, args := parseFlags(os.Args[1:])
 	if showVersion {
 		fmt.Println(version)
 		return
 	}
-	bare := configPath == "" && !install && !remove && !forceUpdate && !elevatedChild && len(args) == 0
+	bare := configPath == "" && !install && !remove && !forceUpdate && !updateNow && !elevatedChild && len(args) == 0
 	if help || (bare && stdoutIsTerminal()) {
 		// Bare invocation in a terminal (e.g. double-clicked on Windows)
 		// shows the help instead of starting a proxy window with no visible
@@ -151,12 +163,16 @@ func main() {
 		fatalUsage("error: --install-service and --remove-service are mutually exclusive")
 	case forceUpdate && (install || remove):
 		fatalUsage("error: --force-update cannot be combined with --install-service/--remove-service")
+	case updateNow && (install || remove || forceUpdate):
+		fatalUsage("error: --update-now cannot be combined with other commands")
 	case install:
 		os.Exit(serviceCommand(configPath, true, noCopy, elevatedChild))
 	case remove:
 		os.Exit(serviceCommand(configPath, false, noCopy, elevatedChild))
 	case forceUpdate:
 		os.Exit(forceUpdateCommand(configPath, elevatedChild))
+	case updateNow:
+		os.Exit(updateNowCommand())
 	}
 	if len(args) > 0 {
 		fatalUsage("error: unknown arguments: %s", strings.Join(args, " "))
@@ -342,17 +358,25 @@ func forceUpdateCommand(configPath string, elevatedChild bool) int {
 		fmt.Printf("%s: APP_VER=dev, updates disabled\n", versionLine())
 		return 0
 	}
+	// A running service can do the privileged work itself (its account owns
+	// the install dir and it knows when the GPU is idle): ask it over the
+	// local control channel first, no admin rights needed. Fails fast when
+	// no service is listening, in which case we do the direct check below.
+	if reply, err := control.Ask(control.CmdUpdateNow); err == nil {
+		return printControlReply(reply)
+	}
 	u := &update.Updater{Repo: cfg.UpdateRepo, Asset: cfg.UpdateAsset, Version: version, Desired: cfg.AppVersion, Log: log}
 
 	// Single-shot: one attempt, fail fast when the server is unreachable
 	// instead of hanging in a TCP connect for minutes.
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
-	staged, err := u.Check(ctx, exePath)
+	staged, to, err := u.Check(ctx, exePath)
 	if err != nil && isPermission(err) && !service.Elevated() {
 		code, _ := elevateAndMirror("--force-update")
-		if code == 0 {
-			fmt.Println("update applied (elevated)")
+		reportElevatedUpdate(code, to)
+		if code == 0 || code == exitCodeStaged {
+			return 0
 		}
 		return code
 	}
@@ -364,12 +388,13 @@ func forceUpdateCommand(configPath string, elevatedChild bool) int {
 		fmt.Printf("%s is up to date\n", versionLine())
 		return 0
 	}
-	fmt.Printf("%s: update staged\n", versionLine())
+	fmt.Printf("gpu-turnstile: updated from %s to %s\n", version, to)
 	restarted, err := service.RestartIfRunning()
 	if err != nil && isPermission(err) && !service.Elevated() {
 		code, _ := elevateAndMirror("--force-update")
-		if code == 0 {
-			fmt.Println("update applied (elevated)")
+		reportElevatedUpdate(code, to)
+		if code == 0 || code == exitCodeStaged {
+			return 0
 		}
 		return code
 	}
@@ -378,13 +403,57 @@ func forceUpdateCommand(configPath string, elevatedChild bool) int {
 		return 1
 	}
 	if restarted {
-		fmt.Println("service restarted on the new version")
+		fmt.Println("service restarted on " + to)
 	} else {
-		fmt.Println("no running service; the new version applies on next start")
+		fmt.Println("no running service; " + to + " applies on the next start")
+	}
+	if elevatedChild {
+		// Tell the non-elevated parent (which cannot see this console)
+		// whether anything was staged, so its mirror message is honest.
+		return exitCodeStaged
 	}
 	return 0
 }
 
+// printControlReply prints the service's answer to a control-channel
+// request: "OK ..." on stdout (exit 0), "ERR ..." on stderr (exit 1).
+func printControlReply(reply string) int {
+	if msg, ok := strings.CutPrefix(reply, "ERR "); ok {
+		fmt.Fprintf(os.Stderr, "gpu-turnstile: %s\n", msg)
+		return 1
+	}
+	fmt.Println("gpu-turnstile: " + strings.TrimPrefix(reply, "OK "))
+	return 0
+}
+
+// updateNowCommand only goes through the running service's control channel
+// (no direct check, no elevation): the unprivileged update trigger.
+func updateNowCommand() int {
+	reply, err := control.Ask(control.CmdUpdateNow)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n\ngpu-turnstile: no running service to ask — use --force-update for a direct check\n", versionLine())
+		return 1
+	}
+	return printControlReply(reply)
+}
+
+// reportElevatedUpdate prints the parent's summary of an elevated
+// --force-update child: exitCodeStaged means the child staged a new binary,
+// 0 means it found nothing to do. to is the tag the parent's own check
+// resolved before it hit the permission wall ("" when it never got that
+// far).
+func reportElevatedUpdate(code int, to string) {
+	switch {
+	case code == exitCodeStaged && to != "":
+		fmt.Printf("gpu-turnstile: updated from %s to %s (elevated)\n", version, to)
+	case code == exitCodeStaged:
+		fmt.Println("update applied (elevated)")
+	case code == 0:
+		fmt.Printf("%s is up to date\n", versionLine())
+	}
+	// Non-zero, non-staged codes: elevateAndMirror already printed the failure.
+}
+
 // serviceCommand installs (copyBin = register the canonical-layout copy)
 // or removes the service and reports the result. On Windows, when the
 // shell is not elevated, the command relaunches itself through a UAC
@@ -518,11 +587,18 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 	if comfyCmdLine != "" {
 		if cfg.ComfyCmd == "" {
 			// Derived from COMFY_DIR: flag a wrong-looking layout early,
-			// while the operator is still watching the startup log.
+			// while the operator is still watching the startup log. Inside
+			// a profile the service account may not enter, os.Stat fails
+			// with EACCES — that reads as "not found" but means "grant
+			// access", so say so.
 			python, script := supervise.ComfyLayout(runtime.GOOS, cfg.ComfyDir)
 			for _, p := range []string{python, script} {
 				if _, err := os.Stat(p); err != nil {
-					log.Warn("COMFY_DIR: file not found; ComfyUI requests will fail until it exists", "path", p)
+					if isPermission(err) {
+						log.Warn("COMFY_DIR: not accessible to the service account; grant access or re-run --install-service", "path", p)
+					} else {
+						log.Warn("COMFY_DIR: file not found; ComfyUI requests will fail until it exists", "path", p)
+					}
 				}
 			}
 		}
@@ -652,7 +728,35 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 	service.StartWatchdog(ctx)
 
 	if cfg.AutoUpdate {
-		go updateLoop(ctx, cfg, log, lk, isService)
+		exePath, err := os.Executable()
+		if err != nil {
+			log.Warn("auto-update disabled: cannot locate executable", "err", err)
+		} else {
+			u := &update.Updater{Repo: cfg.UpdateRepo, Asset: cfg.UpdateAsset, Version: version, Desired: cfg.AppVersion, Log: log}
+			// applyStaged is shared by the hourly loop and the control
+			// channel; the once guard keeps a second trigger from
+			// double-waiting on the GPU lock.
+			var once sync.Once
+			applyStaged := func(to string) {
+				if !isService {
+					log.Warn("auto-update: new binary staged; restart gpu-turnstile to apply", "version", to)
+					return
+				}
+				log.Warn("auto-update: staged; restarting once the GPU is idle", "version", to)
+				once.Do(func() {
+					go func() {
+						if waitForIdle(ctx, lk, 24*time.Hour) {
+							log.Warn("auto-update: restarting to apply update")
+							os.Exit(exitCodeUpdate)
+						}
+					}()
+				})
+			}
+			go updateLoop(ctx, cfg.UpdateInterval, log, u, exePath, applyStaged)
+			if isService {
+				serveControl(ctx, log, u, exePath, applyStaged)
+			}
+		}
 	}
 
 	select {
@@ -794,42 +898,63 @@ func healthLoop(ctx context.Context, interval, probeTimeout time.Duration, log *
 	}
 }
 
-// updateLoop checks for signed updates on startup and every UPDATE_INTERVAL.
-// In service mode a staged update is applied by exiting with exitCodeUpdate
-// once the GPU lock is idle; the service recovery configuration restarts the
-// process with the new binary. Interactively it only logs.
-func updateLoop(ctx context.Context, cfg config.Config, log *slog.Logger, lk *lock.Lock, isService bool) {
-	exePath, err := os.Executable()
-	if err != nil {
-		log.Warn("auto-update disabled: cannot locate executable", "err", err)
-		return
-	}
-	u := &update.Updater{Repo: cfg.UpdateRepo, Asset: cfg.UpdateAsset, Version: version, Desired: cfg.AppVersion, Log: log}
+// updateLoop checks for signed updates on startup and every interval;
+// applyStaged decides what a staged update means (restart when idle as a
+// service, log only interactively).
+func updateLoop(ctx context.Context, interval time.Duration, log *slog.Logger, u *update.Updater, exePath string, applyStaged func(to string)) {
 	for {
-		staged, err := u.Check(ctx, exePath)
+		staged, to, err := u.Check(ctx, exePath)
 		if err != nil && ctx.Err() == nil {
 			log.Warn("auto-update check failed", "err", err)
 		}
 		if staged {
-			if !isService {
-				log.Warn("auto-update: new binary staged; restart gpu-turnstile to apply")
-				return
-			}
-			log.Warn("auto-update: staged; restarting once the GPU is idle")
-			if waitForIdle(ctx, lk, 24*time.Hour) {
-				log.Warn("auto-update: restarting to apply update")
-				os.Exit(exitCodeUpdate)
-			}
+			applyStaged(to)
 			return
 		}
 		select {
 		case <-ctx.Done():
 			return
-		case <-time.After(cfg.UpdateInterval):
+		case <-time.After(interval):
 		}
 	}
 }
 
+// serveControl opens the local control channel (named pipe on Windows,
+// unix socket on Linux) so unprivileged local users can trigger an update
+// check via --force-update without admin rights. The check payload is
+// signature-verified regardless of who asks; triggers are rate-limited to
+// one per minute so the channel cannot be used to spam restarts.
+func serveControl(ctx context.Context, log *slog.Logger, u *update.Updater, exePath string, applyStaged func(to string)) {
+	var mu sync.Mutex
+	var lastTrigger time.Time
+	h := func(cmd string) string {
+		if cmd != control.CmdUpdateNow {
+			return "ERR unknown command: " + cmd
+		}
+		mu.Lock()
+		if wait := time.Minute - time.Since(lastTrigger); wait > 0 {
+			mu.Unlock()
+			return fmt.Sprintf("ERR rate limited: retry in %ds", int(wait.Seconds())+1)
+		}
+		lastTrigger = time.Now()
+		mu.Unlock()
+		cctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+		defer cancel()
+		staged, to, err := u.Check(cctx, exePath)
+		if err != nil {
+			return "ERR update check failed: " + err.Error()
+		}
+		if !staged {
+			return "OK " + version + " is up to date"
+		}
+		applyStaged(to)
+		return "OK updated from " + version + " to " + to + "; the service restarts once the GPU is idle"
+	}
+	if err := control.Serve(ctx, h, log); err != nil {
+		log.Warn("control channel disabled", "err", err)
+	}
+}
+
 // waitForIdle polls the lock until no LLM or image work is active or
 // pending, max at most. Returns false on timeout or cancellation.
 func waitForIdle(ctx context.Context, lk *lock.Lock, max time.Duration) bool {

compose.yaml.example

@@ -6,7 +6,7 @@
 # ComfyUI --listen 0.0.0.0 --port 8189).
 services:
   gpu-turnstile:
-    image: git.rambossek.at/public/gpu-turnstile:v0.1.10
+    image: git.rambossek.at/public/gpu-turnstile:v0.2.3
     restart: unless-stopped
     environment:
       # Each consumer is enabled by setting its URL; leave one unset to

internal/control/control.go

@@ -0,0 +1,61 @@
+// Package control exposes a local-only command channel into a running
+// gpu-turnstile service: a named pipe on Windows, a unix socket on Linux.
+// It lets unprivileged local users ask the service to do privileged work
+// that is safe to offer — currently triggering an update check, whose
+// payload is signature-verified regardless of who asks. The channel never
+// accepts data beyond a one-word command, and the server rate-limits
+// triggers, so the worst a local user can cause is a cheap, throttled
+// check and a GPU-idle-gated restart onto a signed binary.
+//
+// Protocol: the client writes one command line, the server answers with
+// one reply line ("OK ..." or "ERR ...") and hangs up.
+package control
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// CmdUpdateNow asks the service to check for, stage and (once the GPU is
+// idle) restart onto a signed update immediately.
+const CmdUpdateNow = "update-now"
+
+// ErrUnavailable means no running service offers the control channel.
+var ErrUnavailable = errors.New("control channel unavailable")
+
+// Handler answers one command; the returned string is sent back as one
+// line. It must start with "OK " or "ERR ".
+type Handler func(cmd string) string
+
+// serveConn runs the line protocol on one accepted connection.
+func serveConn(c io.ReadWriteCloser, h Handler) {
+	defer c.Close()
+	line, err := bufio.NewReader(io.LimitReader(c, 4096)).ReadString('\n')
+	cmd := strings.TrimSpace(line)
+	if cmd == "" {
+		if err != nil {
+			return
+		}
+		fmt.Fprintln(c, "ERR empty command")
+		return
+	}
+	fmt.Fprintln(c, h(cmd))
+}
+
+// readReply writes cmd and reads the server's one-line reply.
+func readReply(c io.ReadWriteCloser, cmd string) (string, error) {
+	if _, err := fmt.Fprintln(c, cmd); err != nil {
+		return "", err
+	}
+	// The server hangs up after its reply; a broken-pipe error after the
+	// last byte still leaves the reply in the buffer.
+	data, _ := io.ReadAll(io.LimitReader(c, 4096))
+	line := strings.TrimSpace(string(data))
+	if line == "" {
+		return "", ErrUnavailable
+	}
+	return line, nil
+}

internal/control/control_linux.go

@@ -0,0 +1,54 @@
+//go:build linux
+
+package control
+
+import (
+	"context"
+	"log/slog"
+	"net"
+	"os"
+	"time"
+)
+
+// sockPath lives in the unit's RuntimeDirectory; mode 0666 lets every
+// local user ask, nothing can reach it from off the machine.
+const sockPath = "/run/gpu-turnstile/control.sock"
+
+// Serve starts the socket listener in the background and returns; only a
+// setup failure is reported. Each client connection is answered in its own
+// goroutine.
+func Serve(ctx context.Context, h Handler, log *slog.Logger) error {
+	os.Remove(sockPath) // stale socket from a previous run
+	ln, err := net.Listen("unix", sockPath)
+	if err != nil {
+		return err
+	}
+	if err := os.Chmod(sockPath, 0o666); err != nil {
+		ln.Close()
+		return err
+	}
+	go func() {
+		<-ctx.Done()
+		ln.Close()
+	}()
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return // shutting down
+			}
+			go serveConn(c, h)
+		}
+	}()
+	return nil
+}
+
+// Ask sends one command to the running service and returns its reply.
+func Ask(cmd string) (string, error) {
+	c, err := net.DialTimeout("unix", sockPath, 2*time.Second)
+	if err != nil {
+		return "", ErrUnavailable
+	}
+	defer c.Close()
+	return readReply(c, cmd)
+}

internal/control/control_other.go

@@ -0,0 +1,18 @@
+//go:build !windows && !linux
+
+package control
+
+import (
+	"context"
+	"log/slog"
+)
+
+// Serve is a no-op on platforms without a control channel.
+func Serve(ctx context.Context, h Handler, log *slog.Logger) error {
+	return ErrUnavailable
+}
+
+// Ask always reports the channel as unavailable.
+func Ask(cmd string) (string, error) {
+	return "", ErrUnavailable
+}

internal/control/control_test.go

@@ -0,0 +1,46 @@
+package control
+
+import (
+	"errors"
+	"net"
+	"strings"
+	"testing"
+)
+
+func TestRoundTrip(t *testing.T) {
+	server, client := net.Pipe()
+	go serveConn(server, func(cmd string) string {
+		if cmd != CmdUpdateNow {
+			return "ERR unknown command: " + cmd
+		}
+		return "OK v0.2.2 is up to date"
+	})
+	reply, err := readReply(client, CmdUpdateNow)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if reply != "OK v0.2.2 is up to date" {
+		t.Fatalf("reply = %q", reply)
+	}
+
+	server2, client2 := net.Pipe()
+	go serveConn(server2, func(cmd string) string { return "ERR unknown command: " + cmd })
+	reply, err = readReply(client2, "bogus")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(reply, "ERR ") {
+		t.Fatalf("reply = %q, want ERR prefix", reply)
+	}
+}
+
+func TestEmptyReplyIsUnavailable(t *testing.T) {
+	server, client := net.Pipe()
+	go serveConn(server, func(cmd string) string {
+		server.Close() // hang up without answering
+		return ""
+	})
+	if _, err := readReply(client, CmdUpdateNow); !errors.Is(err, ErrUnavailable) {
+		t.Fatalf("err = %v, want ErrUnavailable", err)
+	}
+}

internal/control/control_windows.go

@@ -0,0 +1,112 @@
+//go:build windows
+
+package control
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"os"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// pipePath is a kernel-local named pipe: no TCP, no firewall prompt.
+const pipePath = `\\.\pipe\gpu-turnstile`
+
+// sddlPipe grants full access to Administrators, SYSTEM and the pipe owner,
+// and read+write to authenticated users — except network logons, so the
+// pipe cannot be reached from another machine over SMB.
+const sddlPipe = "D:(D;;GRGW;;;NU)(A;;GA;;;BA)(A;;GA;;;SY)(A;;GA;;;OW)(A;;GRGW;;;AU)"
+
+var (
+	procConvertSDDL = windows.NewLazySystemDLL("advapi32.dll").
+			NewProc("ConvertStringSecurityDescriptorToSecurityDescriptorW")
+	procWaitNamedPipe = windows.NewLazySystemDLL("kernel32.dll").
+				NewProc("WaitNamedPipeW")
+)
+
+func waitNamedPipe(name *uint16, timeout uint32) error {
+	r, _, err := procWaitNamedPipe.Call(uintptr(unsafe.Pointer(name)), uintptr(timeout))
+	if r == 0 {
+		return err
+	}
+	return nil
+}
+
+func securityAttributesFromSDDL(sddl string) (*windows.SecurityAttributes, error) {
+	s, err := windows.UTF16PtrFromString(sddl)
+	if err != nil {
+		return nil, err
+	}
+	var sd *uint16 // SECURITY_DESCRIPTOR*, kept for the process lifetime
+	r, _, callErr := procConvertSDDL.Call(
+		uintptr(unsafe.Pointer(s)), 1, /* SDDL_REVISION_1 */
+		uintptr(unsafe.Pointer(&sd)), 0)
+	if r == 0 {
+		return nil, fmt.Errorf("invalid SDDL: %w", callErr)
+	}
+	sa := &windows.SecurityAttributes{
+		Length:             uint32(unsafe.Sizeof(windows.SecurityAttributes{})),
+		SecurityDescriptor: (*windows.SECURITY_DESCRIPTOR)(unsafe.Pointer(sd)),
+	}
+	return sa, nil
+}
+
+// Serve starts the pipe listener in the background and returns; only a
+// setup failure is reported. Each client connection is answered in its own
+// goroutine. On shutdown the process exit reaps everything.
+func Serve(ctx context.Context, h Handler, log *slog.Logger) error {
+	sa, err := securityAttributesFromSDDL(sddlPipe)
+	if err != nil {
+		return err
+	}
+	name, err := windows.UTF16PtrFromString(pipePath)
+	if err != nil {
+		return err
+	}
+	go func() {
+		for ctx.Err() == nil {
+			pipe, err := windows.CreateNamedPipe(name,
+				windows.PIPE_ACCESS_DUPLEX,
+				windows.PIPE_TYPE_BYTE|windows.PIPE_READMODE_BYTE|windows.PIPE_WAIT,
+				16, 4096, 4096, 0, sa)
+			if err != nil {
+				log.Warn("control channel stopped", "err", err)
+				return
+			}
+			go func() {
+				// Blocks until a client connects; on process exit the
+				// handle goes away with everything else.
+				if err := windows.ConnectNamedPipe(pipe, nil); err != nil {
+					windows.CloseHandle(pipe)
+					return
+				}
+				f := os.NewFile(uintptr(pipe), pipePath)
+				serveConn(f, h) // closes f, and with it the pipe handle
+			}()
+		}
+	}()
+	return nil
+}
+
+// Ask sends one command to the running service and returns its reply.
+func Ask(cmd string) (string, error) {
+	name, err := windows.UTF16PtrFromString(pipePath)
+	if err != nil {
+		return "", err
+	}
+	if err := waitNamedPipe(name, 2000); err != nil {
+		return "", ErrUnavailable
+	}
+	handle, err := windows.CreateFile(name,
+		windows.GENERIC_READ|windows.GENERIC_WRITE, 0, nil,
+		windows.OPEN_EXISTING, 0, 0)
+	if err != nil {
+		return "", ErrUnavailable
+	}
+	f := os.NewFile(uintptr(handle), pipePath)
+	defer f.Close()
+	return readReply(f, cmd)
+}

internal/service/envfile.go

@@ -45,3 +45,19 @@ func writeEnvFile(path, content string) error {
 	}
 	return nil
 }
+
+// configuredValue reads one key from the env file the service will load, so
+// the installers can adapt the sandbox to it (ACL grants, unit directives).
+// "" when unset or unreadable.
+func configuredValue(configPath, key string) string {
+	f, err := os.Open(configPath)
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+	values, err := config.ParseEnvFile(f)
+	if err != nil {
+		return ""
+	}
+	return values[key]
+}

internal/service/service_linux.go

@@ -15,6 +15,8 @@ import (
 	"os/signal"
 	"path/filepath"
 	"syscall"
+
+	"gpu-turnstile/internal/supervise"
 )
 
 // Name matches the Windows service name; the systemd unit is Name + ".service".
@@ -62,8 +64,23 @@ func Run(run func(ctx context.Context) error) error {
 // filesystem is read-only except StateDirectory (the install dir, so
 // self-updates can rewrite the binary), and the usual no-privilege-escalation
 // directives apply. The proxy needs nothing but outbound TCP/UDP and the
-// notify socket, so it loses nothing.
-func renderUnit(exePath, configPath string) string {
+// notify socket, so it loses nothing. A managed ComfyUI (comfyDir) gets a
+// BindPaths hole through ProtectHome/ProtectSystem: it reads its venv and
+// writes output/temp/user data under COMFY_DIR. A venv whose base
+// interpreter (pyvenv.cfg home) lives outside COMFY_DIR gets an additional
+// read-only bind, and a Comfy-Desktop shared data dir (models, input,
+// output) a read-write one.
+func renderUnit(exePath, configPath, comfyDir string) string {
+	bind := ""
+	if comfyDir != "" {
+		bind = "BindPaths=" + comfyDir + "\n"
+		if home := comfyVenvHome(comfyDir); home != "" {
+			bind += "BindReadOnlyPaths=" + home + "\n"
+		}
+		if shared := supervise.DesktopSharedDir(comfyDir); shared != "" {
+			bind += "BindPaths=" + shared + "\n"
+		}
+	}
 	return fmt.Sprintf(`[Unit]
 Description=gpu-turnstile GPU arbitration proxy for Ollama and ComfyUI
 After=network-online.target
@@ -78,7 +95,9 @@ RestartSec=5s
 
 DynamicUser=yes
 StateDirectory=%s
-ProtectSystem=strict
+RuntimeDirectory=%s
+RuntimeDirectoryMode=0755
+%sProtectSystem=strict
 ProtectHome=yes
 PrivateTmp=yes
 NoNewPrivileges=yes
@@ -100,7 +119,7 @@ SystemCallErrorNumber=EPERM
 
 [Install]
 WantedBy=multi-user.target
-`, exePath, configPath, Name)
+`, exePath, configPath, Name, Name, bind)
 }
 
 // copyFile copies src to dst, creating dst with the given mode.
@@ -125,7 +144,9 @@ func copyFile(src, dst string, mode os.FileMode) error {
 // sure /etc/gpu-turnstile.env exists (copied from the given config file if
 // provided), writes the hardened unit, then enables and starts it. With
 // copyBin=false the current executable location and config path are
-// registered as-is instead. Needs root.
+// registered as-is instead. When the config sets COMFY_DIR, the unit gets a
+// BindPaths= for it so the sandboxed service can reach the managed ComfyUI
+// even under /home. Needs root.
 //
 // Re-running install converges an existing unit instead of failing: it is
 // stopped first if active, the installed binary is replaced only when the
@@ -186,7 +207,7 @@ func Install(configPath string, copyBin bool, version string) error {
 			cfg = abs
 		}
 	}
-	rendered := renderUnit(exe, cfg)
+	rendered := renderUnit(exe, cfg, configuredValue(cfg, "COMFY_DIR"))
 	if old, _ := os.ReadFile(unitPath); string(old) != rendered {
 		if err := os.WriteFile(unitPath, []byte(rendered), 0o644); err != nil {
 			return fmt.Errorf("write %s (run as root): %w", unitPath, err)

internal/service/service_linux_test.go

@@ -8,7 +8,7 @@ import (
 )
 
 func TestRenderUnit(t *testing.T) {
-	unit := renderUnit("/var/lib/gpu-turnstile/gpu-turnstile", "/etc/gpu-turnstile.env")
+	unit := renderUnit("/var/lib/gpu-turnstile/gpu-turnstile", "/etc/gpu-turnstile.env", "")
 	for _, want := range []string{
 		"Type=notify",
 		"WatchdogSec=30s",
@@ -17,6 +17,7 @@ func TestRenderUnit(t *testing.T) {
 		"WantedBy=multi-user.target",
 		"DynamicUser=yes",
 		"StateDirectory=gpu-turnstile",
+		"RuntimeDirectory=gpu-turnstile",
 		"ProtectSystem=strict",
 		"NoNewPrivileges=yes",
 		"RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6",
@@ -26,4 +27,12 @@ func TestRenderUnit(t *testing.T) {
 			t.Fatalf("unit missing %q:\n%s", want, unit)
 		}
 	}
+	if strings.Contains(unit, "BindPaths") {
+		t.Fatalf("unit without COMFY_DIR must not bind anything:\n%s", unit)
+	}
+
+	unit = renderUnit("/var/lib/gpu-turnstile/gpu-turnstile", "/etc/gpu-turnstile.env", "/home/gpu/ComfyUI")
+	if !strings.Contains(unit, "BindPaths=/home/gpu/ComfyUI\n") {
+		t.Fatalf("unit with COMFY_DIR must bind it:\n%s", unit)
+	}
 }

internal/service/service_windows.go

@@ -25,7 +25,7 @@ import (
 	"golang.org/x/sys/windows/svc"
 	"golang.org/x/sys/windows/svc/mgr"
 
-	"gpu-turnstile/internal/config"
+	"gpu-turnstile/internal/supervise"
 )
 
 // Name is the Windows service name.
@@ -106,10 +106,12 @@ func (h *handler) Execute(_ []string, requests <-chan svc.ChangeRequest, status
 // the service after 5s on failure — this is also what brings up a staged
 // update after the updater exits with a non-zero code. After registering,
 // the virtual account is granted modify access to the install and data
-// directories (self-updates rewrite the exe), and read access to the
-// config file if it lives elsewhere. The grants must come after
-// CreateService: the virtual account's SID only exists once the service is
-// registered.
+// directories (self-updates rewrite the exe), read access to the
+// config file if it lives elsewhere, and — when the config sets COMFY_DIR —
+// recursive modify access to the managed ComfyUI's install tree, which may
+// live inside a user profile the account otherwise cannot enter. The grants
+// must come after CreateService: the virtual account's SID only exists once
+// the service is registered.
 //
 // Re-running install on an existing service converges instead of failing:
 // the service is stopped first if running (so the binary can be replaced),
@@ -146,6 +148,7 @@ func Install(configPath string, copyBin bool, version string) error {
 		if st, qErr := s.Query(); qErr == nil &&
 			(st.State == svc.Running || st.State == svc.StartPending) {
 			wasRunning = true
+			fmt.Println("stopping the running gpu-turnstile service")
 			if err := stopAndWait(s); err != nil {
 				return err
 			}
@@ -161,6 +164,7 @@ func Install(configPath string, copyBin bool, version string) error {
 			}
 			installedExe := filepath.Join(installDir, "gpu-turnstile.exe")
 			if same, _ := sameFileContent(exe, installedExe); !same {
+				fmt.Printf("installing %s\n", installedExe)
 				if err := copyFile(exe, installedExe); err != nil {
 					return fmt.Errorf("copy binary to %s: %w", installedExe, err)
 				}
@@ -208,6 +212,7 @@ func Install(configPath string, copyBin bool, version string) error {
 		// Best effort: start now instead of waiting for the next boot. A
 		// missing config (no consumer URLs) fails the start; the service stays
 		// registered and can be started once the config exists.
+		fmt.Println("starting the gpu-turnstile service")
 		s.Start()
 		return nil
 	}
@@ -243,6 +248,7 @@ func Install(configPath string, copyBin bool, version string) error {
 		return err
 	}
 	if wasRunning {
+		fmt.Println("starting the gpu-turnstile service")
 		if err := s.Start(); err != nil {
 			return fmt.Errorf("start service: %w", err)
 		}
@@ -354,7 +360,7 @@ func grantAll(exe, configPath string) error {
 			return err
 		}
 	}
-	if logFile := configuredLogFile(configPath); logFile != "" {
+	if logFile := configuredValue(configPath, "LOG_FILE"); logFile != "" {
 		dir := filepath.Dir(logFile)
 		if err := os.MkdirAll(dir, 0o755); err == nil {
 			if err := grantAccess(dir, "(OI)(CI)(M)"); err != nil {
@@ -362,6 +368,31 @@ func grantAll(exe, configPath string) error {
 			}
 		}
 	}
+	// A managed ComfyUI whose install lives somewhere the virtual account
+	// may not go (a user profile) needs an explicit grant — recursively,
+	// since ComfyUI also writes output/temp/user data next to its code. A
+	// missing directory is skipped: the startup warning covers it.
+	if comfyDir := configuredValue(configPath, "COMFY_DIR"); comfyDir != "" {
+		if _, err := os.Stat(comfyDir); err == nil {
+			if err := grantAccessTree(comfyDir, "(OI)(CI)(M)"); err != nil {
+				return err
+			}
+			// uv venvs (Comfy-Desktop) redirect to a base interpreter that
+			// can live outside COMFY_DIR; read+execute suffices for it.
+			if home := comfyVenvHome(comfyDir); home != "" {
+				if err := grantAccessTree(home, "(OI)(CI)(RX)"); err != nil {
+					return err
+				}
+			}
+			// Comfy-Desktop keeps models/input/output in a shared dir next
+			// to the install; the managed instance writes output there.
+			if shared := supervise.DesktopSharedDir(comfyDir); shared != "" {
+				if err := grantAccessTree(shared, "(OI)(CI)(M)"); err != nil {
+					return err
+				}
+			}
+		}
+	}
 	return nil
 }
 
@@ -466,28 +497,35 @@ func RelaunchElevated(args []string) (int, error) {
 // grantAccess gives the virtual account the icacls permission set (e.g.
 // "(OI)(CI)(M)") on path.
 func grantAccess(path, perms string) error {
-	out, err := exec.Command("icacls", path, "/grant", virtualAccount+":"+perms).CombinedOutput()
+	return runIcacls(path, perms, false)
+}
+
+// grantAccessTree is grantAccess with /T: the ACE is applied to the
+// existing tree, not just inherited by children created later. Needed when
+// the tree already exists, e.g. a ComfyUI install in a user profile. On a
+// large tree (a venv has tens of thousands of files) this takes minutes,
+// so it says what it is doing instead of looking hung.
+func grantAccessTree(path, perms string) error {
+	return runIcacls(path, perms, true)
+}
+
+func runIcacls(path, perms string, recursive bool) error {
+	args := []string{path, "/grant", virtualAccount + ":" + perms}
+	if recursive {
+		fmt.Printf("granting %s %s access to %s (large trees can take minutes)\n", virtualAccount, perms, path)
+		args = append(args, "/T")
+	}
+	start := time.Now()
+	out, err := exec.Command("icacls", args...).CombinedOutput()
 	if err != nil {
 		return fmt.Errorf("grant %s access to %s: %w (%s)", virtualAccount, path, err, strings.TrimSpace(string(out)))
 	}
+	if recursive {
+		fmt.Printf("access granted in %s\n", time.Since(start).Round(time.Second))
+	}
 	return nil
 }
 
-// configuredLogFile reads LOG_FILE from the config file so the installer
-// can pre-create and ACL the log directory. "" when unset or unreadable.
-func configuredLogFile(configPath string) string {
-	f, err := os.Open(configPath)
-	if err != nil {
-		return ""
-	}
-	defer f.Close()
-	values, err := config.ParseEnvFile(f)
-	if err != nil {
-		return ""
-	}
-	return values["LOG_FILE"]
-}
-
 // RestartIfRunning restarts the service when it is installed and running
 // (used after a forced update staged a new binary). Reports whether a
 // restart happened. A service that is not installed or not running is not

internal/service/venv.go

@@ -0,0 +1,38 @@
+package service
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// comfyVenvHome returns the base interpreter directory of the Python venv at
+// <comfyDir>/.venv when that directory lives outside comfyDir, "" otherwise.
+// uv-created venvs (Comfy-Desktop) ship a redirector python.exe whose real
+// interpreter is the pyvenv.cfg "home" tree — typically a sibling of
+// COMFY_DIR, which a sandbox/ACL covering COMFY_DIR alone does not reach.
+func comfyVenvHome(comfyDir string) string {
+	data, err := os.ReadFile(filepath.Join(comfyDir, ".venv", "pyvenv.cfg"))
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(data), "\n") {
+		k, v, ok := strings.Cut(line, "=")
+		if !ok || strings.TrimSpace(k) != "home" {
+			continue
+		}
+		home := strings.TrimSpace(v)
+		if home == "" {
+			return ""
+		}
+		if st, err := os.Stat(home); err != nil || !st.IsDir() {
+			return ""
+		}
+		rel, err := filepath.Rel(comfyDir, home)
+		if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
+			return home
+		}
+		return "" // inside comfyDir: already covered by the COMFY_DIR grant
+	}
+	return ""
+}

internal/service/venv_test.go

@@ -0,0 +1,45 @@
+package service
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestComfyVenvHome(t *testing.T) {
+	root := t.TempDir()
+	comfy := filepath.Join(root, "ComfyUI")
+	outside := filepath.Join(root, "standalone-env")
+	inside := filepath.Join(comfy, "runtime")
+	for _, d := range []string{filepath.Join(comfy, ".venv"), outside, inside} {
+		if err := os.MkdirAll(d, 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	cfg := filepath.Join(comfy, ".venv", "pyvenv.cfg")
+
+	write := func(home string) {
+		if err := os.WriteFile(cfg, []byte("home = "+home+"\nversion_info = 3.13.0\n"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	write(outside)
+	if got := comfyVenvHome(comfy); got != outside {
+		t.Fatalf("outside home: got %q, want %q", got, outside)
+	}
+
+	write(inside)
+	if got := comfyVenvHome(comfy); got != "" {
+		t.Fatalf("inside home: got %q, want empty", got)
+	}
+
+	write(filepath.Join(root, "does-not-exist"))
+	if got := comfyVenvHome(comfy); got != "" {
+		t.Fatalf("missing home: got %q, want empty", got)
+	}
+
+	if got := comfyVenvHome(filepath.Join(root, "no-venv")); got != "" {
+		t.Fatalf("no pyvenv.cfg: got %q, want empty", got)
+	}
+}

internal/supervise/supervise.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 	"sync"
@@ -43,7 +44,9 @@ func ComfyLayout(goos, dir string) (python, script string) {
 // DefaultComfyCommand builds the launch command for the standard venv
 // layout (see ComfyLayout): the script is passed relative to dir so dir
 // stays the working directory, and --port is taken from comfyURL when the
-// URL carries one.
+// URL carries one. On a Comfy-Desktop standalone install the shared data
+// directory (models, input, output) is added as --*-directory flags so the
+// managed instance sees the desktop app's models.
 func DefaultComfyCommand(goos, dir, comfyURL string) string {
 	python, script := ComfyLayout(goos, dir)
 	rel, err := filepath.Rel(dir, script)
@@ -54,9 +57,34 @@ func DefaultComfyCommand(goos, dir, comfyURL string) string {
 	if u, err := url.Parse(comfyURL); err == nil && u.Port() != "" {
 		cmd += " --port " + u.Port()
 	}
+	if shared := DesktopSharedDir(dir); shared != "" {
+		for _, sub := range []string{"models", "input", "output"} {
+			p := filepath.Join(shared, sub)
+			if st, err := os.Stat(p); err == nil && st.IsDir() {
+				cmd += ` --` + sub + `-directory "` + p + `"`
+			}
+		}
+	}
 	return cmd
 }
 
+// DesktopSharedDir returns the Comfy-Desktop shared data directory
+// (<root>/ComfyUI-Shared) when dir looks like a desktop standalone install
+// (<root>/ComfyUI-Installs/<name>/ComfyUI) and the shared models directory
+// exists; "" otherwise. The desktop app keeps models, input and output
+// there rather than inside the ComfyUI tree.
+func DesktopSharedDir(dir string) string {
+	installs := filepath.Dir(filepath.Dir(dir))
+	if filepath.Base(installs) != "ComfyUI-Installs" {
+		return ""
+	}
+	shared := filepath.Join(filepath.Dir(installs), "ComfyUI-Shared")
+	if st, err := os.Stat(filepath.Join(shared, "models")); err == nil && st.IsDir() {
+		return shared
+	}
+	return ""
+}
+
 // Process is one managed child process.
 type Process struct {
 	name         string
@@ -185,6 +213,9 @@ func (p *Process) EnsureRunning() error {
 	p.external = false
 	cmd := exec.Command(p.argv[0], p.argv[1:]...)
 	cmd.Dir = p.dir
+	// Ask the child not to colorize (ComfyUI ignores this and colors
+	// anyway, so pipeLog also strips escape sequences).
+	cmd.Env = append(os.Environ(), "NO_COLOR=1", "TERM=dumb")
 	stdout, err := cmd.StdoutPipe()
 	if err != nil {
 		return err
@@ -278,7 +309,9 @@ func (p *Process) WatchIdle(ctx context.Context, idleTimeout time.Duration, gpuI
 }
 
 // pipeLog forwards one child output stream to the log at INFO, line by
-// line, prefixed with the process name.
+// line, prefixed with the process name. ANSI escape sequences are
+// stripped: ComfyUI colorizes unconditionally, and the escapes only
+// render as garbage in a log file.
 func (p *Process) pipeLog(r io.Reader) {
 	buf := make([]byte, 4096)
 	var line string
@@ -290,18 +323,25 @@ func (p *Process) pipeLog(r io.Reader) {
 			if i < 0 {
 				break
 			}
-			p.log.Info(p.name + ": " + strings.TrimRight(line[:i], "\r"))
+			p.log.Info(p.name + ": " + stripANSI(strings.TrimRight(line[:i], "\r")))
 			line = line[i+1:]
 		}
 		if err != nil {
 			if strings.TrimSpace(line) != "" {
-				p.log.Info(p.name + ": " + line)
+				p.log.Info(p.name + ": " + stripANSI(line))
 			}
 			return
 		}
 	}
 }
 
+// ansiPattern matches CSI escape sequences (colors, cursor moves, …).
+var ansiPattern = regexp.MustCompile("\x1b\\[[0-9;?]*[a-zA-Z]")
+
+func stripANSI(s string) string {
+	return ansiPattern.ReplaceAllString(s, "")
+}
+
 // stopTree kills cmd's process, including its children on Windows (python
 // launchers tend to spawn some). The Wait goroutine reaps it.
 func stopTree(cmd *exec.Cmd) {

internal/supervise/supervise_test.go

@@ -239,3 +239,38 @@ func TestComfyLayoutAndDefaultCommand(t *testing.T) {
 		t.Errorf("missing-layout script = %s", script)
 	}
 }
+
+func TestStripANSI(t *testing.T) {
+	cases := map[string]string{
+		"\x1b[32m[INFO]\x1b[0m Starting server":   "[INFO] Starting server",
+		"\x1b[1m\x1b[31m[ERROR]\x1b[0m boom":      "[ERROR] boom",
+		"plain line":                              "plain line",
+		"\x1b[33mWARN\x1b[0m: \x1b[1mbold\x1b[0m": "WARN: bold",
+	}
+	for in, want := range cases {
+		if got := stripANSI(in); got != want {
+			t.Errorf("stripANSI(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+func TestDesktopSharedDir(t *testing.T) {
+	root := t.TempDir()
+	comfy := filepath.Join(root, "ComfyUI-Installs", "rtx5080", "ComfyUI")
+	if err := os.MkdirAll(comfy, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if got := DesktopSharedDir(comfy); got != "" {
+		t.Fatalf("no shared dir yet: got %q, want empty", got)
+	}
+	shared := filepath.Join(root, "ComfyUI-Shared")
+	if err := os.MkdirAll(filepath.Join(shared, "models"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if got := DesktopSharedDir(comfy); got != shared {
+		t.Fatalf("got %q, want %q", got, shared)
+	}
+	if got := DesktopSharedDir(filepath.Join(root, "plain", "ComfyUI")); got != "" {
+		t.Fatalf("non-desktop layout: got %q, want empty", got)
+	}
+}

internal/update/update.go

@@ -173,11 +173,13 @@ func CleanupOld(exePath string) {
 
 // Check performs a single update check. staged is true when a
 // signature-verified binary has been swapped into place at exePath; the
-// caller should then restart the process. A nil error with staged=false
-// means "no action" (up to date, APP_VER=dev, or no embedded public key);
-// a non-nil error means the check failed and the running binary is
-// untouched.
-func (u *Updater) Check(ctx context.Context, exePath string) (staged bool, err error) {
+// caller should then restart the process. to is the release tag the check
+// resolved (the latest release or the pinned tag), set once the release
+// fetch succeeded — even when staging afterwards fails. A nil error with
+// staged=false means "no action" (up to date, APP_VER=dev, or no embedded
+// public key); a non-nil error means the check failed and the running
+// binary is untouched.
+func (u *Updater) Check(ctx context.Context, exePath string) (staged bool, to string, err error) {
 	log := u.logger()
 	desired := u.Desired
 	if desired == "" {
@@ -185,15 +187,15 @@ func (u *Updater) Check(ctx context.Context, exePath string) (staged bool, err e
 	}
 	if desired == "dev" {
 		log.Debug("auto-update: APP_VER=dev, skipping")
-		return false, nil
+		return false, "", nil
 	}
 	if publicKeyPEM == "" {
 		log.Debug("auto-update: no public key embedded, skipping")
-		return false, nil
+		return false, "", nil
 	}
 	api, err := u.apiURL()
 	if err != nil {
-		return false, err
+		return false, "", err
 	}
 
 	pinned := desired != "stable"
@@ -203,29 +205,30 @@ func (u *Updater) Check(ctx context.Context, exePath string) (staged bool, err e
 	}
 	body, err := u.get(ctx, endpoint)
 	if err != nil {
-		return false, fmt.Errorf("fetch release: %w", err)
+		return false, "", fmt.Errorf("fetch release: %w", err)
 	}
 	var rel release
 	if err := json.Unmarshal(body, &rel); err != nil {
-		return false, fmt.Errorf("parse release: %w", err)
+		return false, "", fmt.Errorf("parse release: %w", err)
 	}
+	to = rel.TagName
 	if pinned {
 		// Pin mode: any difference from the target tag means stage it —
 		// including downgrades and replacing a dev binary.
 		if u.Version == rel.TagName {
 			log.Debug("auto-update: already on pinned version", "version", u.Version)
-			return false, nil
+			return false, to, nil
 		}
 	} else if u.Version != "" && u.Version != "dev" {
 		// Stable mode: only strictly newer releases count; a dev binary
 		// cannot be compared and is always replaced by the latest release.
 		newer, err := newerVersion(u.Version, rel.TagName)
 		if err != nil {
-			return false, err
+			return false, to, err
 		}
 		if !newer {
 			log.Debug("auto-update: up to date", "version", u.Version, "latest", rel.TagName)
-			return false, nil
+			return false, to, nil
 		}
 	}
 
@@ -235,42 +238,42 @@ func (u *Updater) Check(ctx context.Context, exePath string) (staged bool, err e
 	}
 	assetURL, ok := urls[u.Asset]
 	if !ok {
-		return false, fmt.Errorf("release %s has no asset %q", rel.TagName, u.Asset)
+		return false, to, fmt.Errorf("release %s has no asset %q", rel.TagName, u.Asset)
 	}
 	sigURL, ok := urls[u.Asset+".sig"]
 	if !ok {
-		return false, fmt.Errorf("release %s has no signature asset %q", rel.TagName, u.Asset+".sig")
+		return false, to, fmt.Errorf("release %s has no signature asset %q", rel.TagName, u.Asset+".sig")
 	}
 
 	data, err := u.get(ctx, assetURL)
 	if err != nil {
-		return false, fmt.Errorf("download %s: %w", u.Asset, err)
+		return false, to, fmt.Errorf("download %s: %w", u.Asset, err)
 	}
 	sig, err := u.get(ctx, sigURL)
 	if err != nil {
-		return false, fmt.Errorf("download signature: %w", err)
+		return false, to, fmt.Errorf("download signature: %w", err)
 	}
 
 	if sumURL, ok := urls[u.Asset+".sha256"]; ok {
 		sumText, err := u.get(ctx, sumURL)
 		if err != nil {
-			return false, fmt.Errorf("download checksum: %w", err)
+			return false, to, fmt.Errorf("download checksum: %w", err)
 		}
 		want := strings.Fields(string(sumText))[0]
 		got := hex.EncodeToString(sha256Bytes(data))
 		if !strings.EqualFold(want, got) {
-			return false, fmt.Errorf("sha256 mismatch: got %s, want %s", got, want)
+			return false, to, fmt.Errorf("sha256 mismatch: got %s, want %s", got, want)
 		}
 	}
 	if err := verifySignature(publicKeyPEM, data, sig); err != nil {
-		return false, err
+		return false, to, err
 	}
 
 	if err := stage(exePath, data); err != nil {
-		return false, fmt.Errorf("stage update: %w", err)
+		return false, to, fmt.Errorf("stage update: %w", err)
 	}
 	log.Info("auto-update: new version staged", "from", u.Version, "to", rel.TagName)
-	return true, nil
+	return true, to, nil
 }
 
 func sha256Bytes(data []byte) []byte {

internal/update/update_test.go

@@ -102,13 +102,16 @@ func TestCheckStagesUpdate(t *testing.T) {
 	withPublicKey(t, f.pubPEM)
 	exe := fakeExe(t)
 
-	staged, err := f.updater("v0.1.2").Check(context.Background(), exe)
+	staged, to, err := f.updater("v0.1.2").Check(context.Background(), exe)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if !staged {
 		t.Fatal("expected staged update")
 	}
+	if to != "v9.9.9" {
+		t.Fatalf("to = %q, want v9.9.9", to)
+	}
 	content, _ := os.ReadFile(exe)
 	if string(content) != "new-binary" {
 		t.Fatalf("exe content = %q", content)
@@ -125,7 +128,7 @@ func TestCheckRejectsTamperedSignature(t *testing.T) {
 	withPublicKey(t, f.pubPEM)
 	exe := fakeExe(t)
 
-	staged, err := f.updater("v0.1.2").Check(context.Background(), exe)
+	staged, _, err := f.updater("v0.1.2").Check(context.Background(), exe)
 	if err == nil {
 		t.Fatal("expected signature error")
 	}
@@ -142,7 +145,7 @@ func TestCheckSkipsOlderOrEqual(t *testing.T) {
 	for _, tag := range []string{"v0.1.2", "v0.1.1", "v0.0.9"} {
 		f := newFakeGitea(t, tag, []byte("new-binary"))
 		withPublicKey(t, f.pubPEM)
-		staged, err := f.updater("v0.1.2").Check(context.Background(), fakeExe(t))
+		staged, _, err := f.updater("v0.1.2").Check(context.Background(), fakeExe(t))
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -155,7 +158,7 @@ func TestCheckSkipsOlderOrEqual(t *testing.T) {
 func TestCheckSkipsWithoutPublicKey(t *testing.T) {
 	f := newFakeGitea(t, "v9.9.9", []byte("new-binary"))
 	withPublicKey(t, "")
-	staged, err := f.updater("v0.1.2").Check(context.Background(), fakeExe(t))
+	staged, _, err := f.updater("v0.1.2").Check(context.Background(), fakeExe(t))
 	if err != nil || staged {
 		t.Fatalf("staged=%v err=%v, want no action without key", staged, err)
 	}
@@ -167,7 +170,7 @@ func TestCheckDevBuildGetsStable(t *testing.T) {
 	f := newFakeGitea(t, "v9.9.9", []byte("new-binary"))
 	withPublicKey(t, f.pubPEM)
 	exe := fakeExe(t)
-	staged, err := f.updater("dev").Check(context.Background(), exe)
+	staged, _, err := f.updater("dev").Check(context.Background(), exe)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -184,7 +187,7 @@ func TestCheckDesiredDevDisables(t *testing.T) {
 	f := newFakeGitea(t, "v9.9.9", []byte("new-binary"))
 	withPublicKey(t, f.pubPEM)
 	for _, version := range []string{"dev", "v0.1.2"} {
-		staged, err := f.updaterDesired(version, "dev").Check(context.Background(), fakeExe(t))
+		staged, _, err := f.updaterDesired(version, "dev").Check(context.Background(), fakeExe(t))
 		if err != nil || staged {
 			t.Fatalf("version %s: staged=%v err=%v, want no action with APP_VER=dev", version, staged, err)
 		}
@@ -198,13 +201,16 @@ func TestCheckPinned(t *testing.T) {
 		f := newFakeGitea(t, "v0.5.0", []byte("pinned-binary"))
 		withPublicKey(t, f.pubPEM)
 		exe := fakeExe(t)
-		staged, err := f.updaterDesired(version, "v0.5.0").Check(context.Background(), exe)
+		staged, to, err := f.updaterDesired(version, "v0.5.0").Check(context.Background(), exe)
 		if err != nil {
 			t.Fatalf("version %s: %v", version, err)
 		}
 		if !staged {
 			t.Fatalf("version %s: expected pinned v0.5.0 to be staged", version)
 		}
+		if to != "v0.5.0" {
+			t.Fatalf("version %s: to = %q, want v0.5.0", version, to)
+		}
 		content, _ := os.ReadFile(exe)
 		if string(content) != "pinned-binary" {
 			t.Fatalf("version %s: exe content = %q", version, content)
@@ -213,7 +219,7 @@ func TestCheckPinned(t *testing.T) {
 
 	f := newFakeGitea(t, "v0.5.0", []byte("pinned-binary"))
 	withPublicKey(t, f.pubPEM)
-	staged, err := f.updaterDesired("v0.5.0", "v0.5.0").Check(context.Background(), fakeExe(t))
+	staged, _, err := f.updaterDesired("v0.5.0", "v0.5.0").Check(context.Background(), fakeExe(t))
 	if err != nil || staged {
 		t.Fatalf("staged=%v err=%v, want no action when already on the pinned version", staged, err)
 	}