diff --git a/cli/cmd/cache_helper.go b/cli/cmd/cache_helper.go
index efcabd393..ce8a1deb3 100644
--- a/cli/cmd/cache_helper.go
+++ b/cli/cmd/cache_helper.go
@@ -4,11 +4,17 @@ import (
 	"context"
 
 	"github.com/pkg/errors"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/replicatedhq/replicated/pkg/kotsclient"
 	"github.com/replicatedhq/replicated/pkg/types"
 )
 
 func getApp(appSlugOrID string, kotsClient *kotsclient.VendorV3Client) (*types.App, error) {
+	cache, err := replicatedcache.GetInstance()
+	if err != nil {
+		return nil, errors.Wrap(err, "initialize cache")
+	}
+
 	app, err := cache.GetApp(appSlugOrID)
 	if err == nil && app != nil {
 		return app, nil
diff --git a/cli/cmd/completion_test.go b/cli/cmd/completion_test.go
index 31587a020..9e73693c3 100644
--- a/cli/cmd/completion_test.go
+++ b/cli/cmd/completion_test.go
@@ -2,11 +2,46 @@ package cmd
 
 import (
 	"bytes"
+	"os"
 	"testing"
 
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/spf13/cobra"
 )
 
+// TestShellCompletionsNoHome verifies that completion commands work even when
+// HOME is unset or invalid (e.g., during Nix builds). This is a regression
+// test for https://github.com/replicatedhq/replicated/issues/535.
+func TestShellCompletionsNoHome(t *testing.T) {
+	// Save and clear HOME to simulate an environment where cache initialization
+	// would fail.
+	origHome := os.Getenv("HOME")
+	os.Unsetenv("HOME")
+	os.Unsetenv("XDG_CACHE_HOME")
+	defer func() {
+		os.Setenv("HOME", origHome)
+	}()
+
+	// Reset the lazy cache state so this test doesn't interfere with others.
+	replicatedcache.ResetForTesting()
+	defer replicatedcache.ResetForTesting()
+
+	parentCmd := &cobra.Command{
+		Use: "replicated",
+	}
+	out := bytes.NewBufferString("")
+	cmd := NewCmdCompletion(out, parentCmd.Name())
+	parentCmd.AddCommand(cmd)
+
+	err := RunCompletion(out, cmd, []string{"bash"})
+	if err != nil {
+		t.Fatalf("Unexpected error with no HOME: %v", err)
+	}
+	if out.Len() == 0 {
+		t.Fatalf("Output was not written")
+	}
+}
+
 // This unit-test was adapted from kubectl repo
 // Link: https://github.com/kubernetes/kubectl/blob/826006cdb947f80a679ff1eb3cb53f183a6a9bf2/pkg/cmd/completion/completion_test.go
 func TestShellCompletions(t *testing.T) {
diff --git a/cli/cmd/default_clear.go b/cli/cmd/default_clear.go
index 46aae45b3..0ff9ccec7 100644
--- a/cli/cmd/default_clear.go
+++ b/cli/cmd/default_clear.go
@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"github.com/pkg/errors"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/spf13/cobra"
 )
 
@@ -29,6 +30,11 @@ replicated default clear app`,
 }
 
 func (r *runners) clearDefault(cmd *cobra.Command, defaultType string) error {
+	cache, err := replicatedcache.GetInstance()
+	if err != nil {
+		return errors.Wrap(err, "initialize cache")
+	}
+
 	if err := cache.ClearDefault(defaultType); err != nil {
 		return errors.Wrap(err, "clear default")
 	}
diff --git a/cli/cmd/default_clearall.go b/cli/cmd/default_clearall.go
index 2a979fa14..db8e7b397 100644
--- a/cli/cmd/default_clearall.go
+++ b/cli/cmd/default_clearall.go
@@ -1,6 +1,10 @@
 package cmd
 
-import "github.com/spf13/cobra"
+import (
+	"github.com/pkg/errors"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
+	"github.com/spf13/cobra"
+)
 
 func (r *runners) InitDefaultClearAllCommand(parent *cobra.Command) *cobra.Command {
 	cmd := &cobra.Command{
@@ -22,6 +26,11 @@ replicated default clear-all`,
 }
 
 func (r *runners) clearAllDefaults(cmd *cobra.Command) error {
+	cache, err := replicatedcache.GetInstance()
+	if err != nil {
+		return errors.Wrap(err, "initialize cache")
+	}
+
 	if err := cache.ClearDefault("app"); err != nil {
 		return err
 	}
diff --git a/cli/cmd/default_set.go b/cli/cmd/default_set.go
index db9ffee6c..804c02035 100644
--- a/cli/cmd/default_set.go
+++ b/cli/cmd/default_set.go
@@ -3,6 +3,7 @@ package cmd
 import (
 	"github.com/pkg/errors"
 	"github.com/replicatedhq/replicated/cli/print"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/replicatedhq/replicated/pkg/types"
 	"github.com/spf13/cobra"
 )
@@ -44,6 +45,11 @@ func (r *runners) setDefault(cmd *cobra.Command, defaultType string, defaultValu
 			return errors.Wrap(err, "get app")
 		}
 
+		cache, err := replicatedcache.GetInstance()
+		if err != nil {
+			return errors.Wrap(err, "initialize cache")
+		}
+
 		if err := cache.SetDefault(defaultType, defaultValue); err != nil {
 			return errors.Wrap(err, "set default in cache")
 		}
diff --git a/cli/cmd/default_show.go b/cli/cmd/default_show.go
index 5bcc9a110..347060ff2 100644
--- a/cli/cmd/default_show.go
+++ b/cli/cmd/default_show.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/pkg/errors"
 	"github.com/replicatedhq/replicated/cli/print"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/replicatedhq/replicated/pkg/types"
 	"github.com/spf13/cobra"
 )
@@ -40,6 +41,11 @@ replicated default show app
 }
 
 func (r *runners) showDefault(cmd *cobra.Command, defaultType string, outputFormat string) error {
+	cache, err := replicatedcache.GetInstance()
+	if err != nil {
+		return errors.Wrap(err, "initialize cache")
+	}
+
 	defaultValue, err := cache.GetDefault(defaultType)
 	if err != nil {
 		return errors.Wrap(err, "get default value")
diff --git a/cli/cmd/enterprise_portal_preview.go b/cli/cmd/enterprise_portal_preview.go
index 73a299a5d..eaf9033e2 100644
--- a/cli/cmd/enterprise_portal_preview.go
+++ b/cli/cmd/enterprise_portal_preview.go
@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+	replicatedcache "github.com/replicatedhq/replicated/pkg/cache"
 	"github.com/replicatedhq/replicated/pkg/credentials"
 	"github.com/replicatedhq/replicated/pkg/kotsclient"
 	"github.com/replicatedhq/replicated/pkg/platformclient"
@@ -106,8 +107,11 @@ func (r *runners) enterprisePortalPreview(cmd *cobra.Command, args []string) err
 	//   2. default app set via `replicated default app <slug>` (cache.DefaultApp)
 	//   3. REPLICATED_APP env var
 	appSlug := appSlugOrID
-	if appSlug == "" && cache != nil {
-		appSlug = cache.DefaultApp
+	if appSlug == "" {
+		cache, err := replicatedcache.GetInstance()
+		if err == nil && cache != nil {
+			appSlug = cache.DefaultApp
+		}
 	}
 	if appSlug == "" {
 		appSlug = os.Getenv("REPLICATED_APP")
diff --git a/cli/cmd/root.go b/cli/cmd/root.go
index b2268218e..196c497ff 100644
--- a/cli/cmd/root.go
+++ b/cli/cmd/root.go
@@ -35,7 +35,6 @@ var (
 	profileNameFlag string
 	platformOrigin  = "https://api.replicated.com/vendor"
 	kurlDotSHOrigin = "https://kurl.sh"
-	cache           *replicatedcache.Cache
 	debugFlag       bool
 )
 
@@ -45,12 +44,6 @@ func init() {
 		platformOrigin = originFromEnv
 	}
 
-	c, err := replicatedcache.InitCache()
-	if err != nil {
-		panic(err)
-	}
-	cache = c
-
 	// Set debug mode from environment variable
 	if os.Getenv("REPLICATED_DEBUG") == "1" || os.Getenv("REPLICATED_DEBUG") == "true" {
 		debugFlag = true
@@ -446,6 +439,11 @@ func Execute(rootCmd *cobra.Command, stdin io.Reader, stdout io.Writer, stderr i
 			return errors.Wrap(err, "set up APIs")
 		}
 
+		cache, err := replicatedcache.GetInstance()
+		if err != nil {
+			return errors.Wrap(err, "initialize cache")
+		}
+
 		if appSlugOrID == "" {
 			if cache.DefaultApp != "" {
 				appSlugOrID = cache.DefaultApp
diff --git a/pkg/cache/cache.go b/pkg/cache/cache.go
index e53de1b69..01dc441cc 100644
--- a/pkg/cache/cache.go
+++ b/pkg/cache/cache.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"sync"
 	"time"
 
 	"github.com/adrg/xdg"
@@ -11,6 +12,32 @@ import (
 	"github.com/replicatedhq/replicated/pkg/types"
 )
 
+var (
+	instance    *Cache
+	instanceErr error
+	once        sync.Once
+)
+
+// GetInstance returns the singleton cache instance, initializing it on first
+// call. Lazy initialization ensures commands that don't need the cache (e.g.
+// 'completion') won't fail when HOME is not writable.
+func GetInstance() (*Cache, error) {
+	once.Do(func() {
+		instance, instanceErr = InitCache()
+	})
+	if instanceErr != nil {
+		return nil, instanceErr
+	}
+	return instance, nil
+}
+
+// ResetForTesting resets the singleton so tests can control cache state.
+func ResetForTesting() {
+	once = sync.Once{}
+	instance = nil
+	instanceErr = nil
+}
+
 const cacheFileName = "replicated.cache"
 
 type Cache struct {