Use kit runtime store writability check

go.mod

@@ -30,7 +30,8 @@ require (
 	github.com/teambition/rrule-go v1.8.2
 	github.com/testcontainers/testcontainers-go v0.42.0
 	github.com/testcontainers/testcontainers-go/modules/postgres v0.42.0
-	go.kenn.io/kit v0.20.0
+	go.kenn.io/kit v0.21.3
+	golang.org/x/sync v0.21.0
 	golang.org/x/sys v0.46.0
 	golang.org/x/term v0.44.0
 	golang.org/x/text v0.38.0
@@ -167,7 +168,6 @@ require (
 	golang.org/x/mod v0.36.0 // indirect
 	golang.org/x/net v0.56.0 // indirect
 	golang.org/x/oauth2 v0.36.0 // indirect
-	golang.org/x/sync v0.21.0 // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20260706201446-f0a921348800 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260706201446-f0a921348800 // indirect
 	google.golang.org/grpc v1.81.1 // indirect

go.sum

@@ -285,8 +285,8 @@ github.com/yuin/goldmark-emoji v1.0.6 h1:QWfF2FYaXwL74tfGOW5izeiZepUDroDJfWubQI9
 github.com/yuin/goldmark-emoji v1.0.6/go.mod h1:ukxJDKFpdFb5x0a5HqbdlcKtebh086iJpI31LTKmWuA=
 github.com/yusufpapurcu/wmi v1.2.4 h1:zFUKzehAFReQwLys1b/iSMl+JQGSCSjtVqQn9bBrPo0=
 github.com/yusufpapurcu/wmi v1.2.4/go.mod h1:SBZ9tNy3G9/m5Oi98Zks0QjeHVDvuK0qfxQmPyzfmi0=
-go.kenn.io/kit v0.20.0 h1:vviC9r/QRWN7Sh09ISh+7xlYVoKvCKVoqFLcUkGutL4=
-go.kenn.io/kit v0.20.0/go.mod h1:Cg1V5dG+XaSDYr/nE0tvmCxotfpYtW1vPhyc+Ph9Ny0=
+go.kenn.io/kit v0.21.3 h1:7LejpspYJR2Lb2mCQnukXW5wc2cLQ9P6G2UInaoeowI=
+go.kenn.io/kit v0.21.3/go.mod h1:sUFJe7d25a3FYwjL3mlHx/qzHhF8//xNnR920jzoejw=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
 go.opentelemetry.io/contrib/bridges/prometheus v0.69.0 h1:saQoWg5845Q8TojpqeVStS7zGwVZ6bc5W2PJavTPiBM=

internal/client/ensure.go

@@ -82,7 +82,9 @@ var (
 	stopRunningDaemonsForEnsure  = stopRunningDaemons
 	signalDaemonStopForEnsure    = daemon.SignalDaemonStop
 	discoverDaemonForAutoStart   = discoverForEnsureWithError
-	checkDaemonStateForEnsure    = checkDaemonStateWritable
+	checkDaemonStateForEnsure    = func(dataDir string) error {
+		return (kitdaemon.RuntimeStore{Dir: dataDir}).CheckWritable()
+	}
 )
 
 // EnsureRunning returns a live daemon's base URL, auto-starting the daemon
@@ -328,22 +330,6 @@ func autoStart(ctx context.Context, dataDir string) (string, error) {
 	return "", fmt.Errorf("daemon failed to start within %s; inspect kata daemon status and kata daemon logs", daemonStartupWait)
 }
 
-// checkDaemonStateWritable verifies that an auto-started daemon can write its
-// runtime record before spawning it. Without this check, a sandboxed child can
-// fail silently and leave the caller waiting for the full readiness deadline.
-func checkDaemonStateWritable(dataDir string) error {
-	if err := os.MkdirAll(dataDir, 0o700); err != nil {
-		return err
-	}
-	f, err := os.CreateTemp(dataDir, ".kata-write-check-*")
-	if err != nil {
-		return err
-	}
-	path := f.Name()
-	defer func() { _ = os.Remove(path) }()
-	return f.Close()
-}
-
 // daemonLogWriter opens <dataDir>/daemon.log for the auto-started daemon's
 // stdout+stderr. Returns nil (so exec falls back to the null device) if the
 // directory or file cannot be created — the caller must never substitute its

internal/client/ensure_unix_test.go

@@ -0,0 +1,38 @@
+//go:build !windows
+
+package client
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	kitdaemon "go.kenn.io/kit/daemon"
+)
+
+func TestAutoStartRejectsSymlinkStateDirectoryBeforeSpawn(t *testing.T) {
+	base := t.TempDir()
+	target := filepath.Join(base, "target")
+	require.NoError(t, os.Mkdir(target, 0o700))
+	dataDir := filepath.Join(base, "runtime")
+	require.NoError(t, os.Symlink(target, dataDir))
+
+	originalStart := startDetachedDaemonForEnsure
+	spawnErr := errors.New("unexpected daemon spawn")
+	started := false
+	startDetachedDaemonForEnsure = func(context.Context, kitdaemon.StartDetachedOptions) error {
+		started = true
+		return spawnErr
+	}
+	t.Cleanup(func() { startDetachedDaemonForEnsure = originalStart })
+
+	_, err := autoStart(t.Context(), dataDir)
+
+	require.Error(t, err)
+	assert.False(t, started, "daemon should not be spawned for a symlinked state directory")
+	assert.NotErrorIs(t, err, spawnErr)
+}