diff --git a/README.md b/README.md
index 8866db60..3f2b8c8a 100644
--- a/README.md
+++ b/README.md
@@ -398,7 +398,7 @@ Lumen reclaim the space for you:
 ```bash
 lumen clean            # remove indexes unused for 30 days or whose project is gone
 lumen clean --days 7   # tighten the cutoff to a week
-lumen clean --days 0   # remove every cached index on this host
+lumen clean --days 0   # remove every eligible index except actively locked indexes
 ```
 
 An index counts as used every time Lumen opens it (search, indexing, status, or
diff --git a/cmd/clean.go b/cmd/clean.go
index 5c4b801a..01685a1d 100644
--- a/cmd/clean.go
+++ b/cmd/clean.go
@@ -24,12 +24,18 @@ import (
 	"github.com/ory/lumen/internal/config"
 	"github.com/ory/lumen/internal/indexlock"
 	"github.com/ory/lumen/internal/store"
+	"github.com/ory/lumen/internal/tui"
 	"github.com/spf13/cobra"
 )
 
 // defaultCleanDays is how long an index may go unused before `lumen clean`
 // removes it.
-const defaultCleanDays = 30
+const (
+	defaultCleanDays = 30
+	maxCleanDays     = 106751
+)
+
+var removeIndexDir = os.RemoveAll
 
 func init() {
 	addCleanFlags(cleanCmd)
@@ -40,7 +46,7 @@ func init() {
 // definition never drifts from what runClean reads.
 func addCleanFlags(cmd *cobra.Command) {
 	cmd.Flags().Int("days", defaultCleanDays,
-		"remove indexes not used in the last N days (0 removes every index that is not currently being written)")
+		"remove indexes not used in the last N days (0 removes every eligible index except those protected by active locks)")
 }
 
 var cleanCmd = &cobra.Command{
@@ -56,7 +62,8 @@ checkouts, and abandoned models leave behind data that is never read again.
 Indexes written by older binaries that never recorded an access time fall back
 to their last indexing time; those without any usable timestamp are removed.
 
-Use "lumen clean --days 0" to drop every cached index on this host, and
+Use "lumen clean --days 0" to drop every eligible cached index except those
+protected by active locks, and
 "lumen index --force <project-path>" to rebuild a single project from scratch.
 
 Indexes with an indexer currently running are always kept.`, defaultCleanDays),
@@ -72,6 +79,9 @@ func runClean(cmd *cobra.Command, _ []string) error {
 	if days < 0 {
 		return fmt.Errorf("--days must not be negative, got %d", days)
 	}
+	if days > maxCleanDays {
+		return fmt.Errorf("--days must not exceed %d, got %d", maxCleanDays, days)
+	}
 	dataDir := filepath.Join(config.XDGDataDir(), "lumen")
 	return cleanIndexes(cmd.ErrOrStderr(), cmd.OutOrStdout(), dataDir, days, time.Now())
 }
@@ -82,10 +92,11 @@ func runClean(cmd *cobra.Command, _ []string) error {
 // reported and the sweep continues; the first such failure is returned once
 // every directory has been considered.
 func cleanIndexes(stderr, stdout io.Writer, dataDir string, days int, now time.Time) error {
+	progress := tui.NewProgress(stderr)
 	entries, err := os.ReadDir(dataDir)
 	if err != nil {
 		if os.IsNotExist(err) {
-			_, _ = fmt.Fprintln(stderr, "No index data found — nothing to clean.")
+			progress.Info("No index data found — nothing to clean.")
 			return nil
 		}
 		return fmt.Errorf("read data dir: %w", err)
@@ -102,29 +113,17 @@ func cleanIndexes(stderr, stdout io.Writer, dataDir string, days int, now time.T
 			continue
 		}
 		hashDir := filepath.Join(dataDir, entry.Name())
-		dbPath := filepath.Join(hashDir, "index.db")
-
-		if indexlock.IsHeld(indexlock.LockPathForDB(dbPath)) {
-			_, _ = fmt.Fprintf(stderr, "Keeping %s: an indexer is currently running.\n", entry.Name())
+		wasRemoved, err := cleanIndex(progress, entry.Name(), hashDir, days, cutoff)
+		if wasRemoved {
+			removed++
+		} else {
 			skipped++
-			continue
-		}
-
-		stale, reason := isIndexStale(dbPath, days, cutoff)
-		if !stale {
-			skipped++
-			continue
 		}
-		if err := os.RemoveAll(hashDir); err != nil {
-			_, _ = fmt.Fprintf(stderr, "Failed to remove %s: %v\n", hashDir, err)
+		if err != nil {
 			if firstErr == nil {
-				firstErr = fmt.Errorf("remove %s: %w", hashDir, err)
+				firstErr = err
 			}
-			skipped++
-			continue
 		}
-		_, _ = fmt.Fprintf(stderr, "Removed %s (%s).\n", entry.Name(), reason)
-		removed++
 	}
 
 	_, _ = fmt.Fprintf(stdout, "Removed %d index director%s, skipped %d.\n",
@@ -132,6 +131,28 @@ func cleanIndexes(stderr, stdout io.Writer, dataDir string, days int, now time.T
 	return firstErr
 }
 
+// cleanIndex evaluates and removes one index while holding its writer lock.
+func cleanIndex(progress *tui.Progress, name, hashDir string, days int, cutoff time.Time) (bool, error) {
+	dbPath := filepath.Join(hashDir, "index.db")
+	lock, err := indexlock.TryAcquire(indexlock.LockPathForDB(dbPath))
+	if err != nil || lock == nil {
+		progress.Info(fmt.Sprintf("Keeping %s: an indexer is currently running.", name))
+		return false, nil
+	}
+	defer lock.Release()
+
+	stale, reason := isIndexStale(dbPath, days, cutoff)
+	if !stale {
+		return false, nil
+	}
+	if err := removeIndexDir(hashDir); err != nil {
+		progress.Info(fmt.Sprintf("Failed to remove %s: %v", hashDir, err))
+		return false, fmt.Errorf("remove %s: %w", hashDir, err)
+	}
+	progress.Info(fmt.Sprintf("Removed %s (%s).", name, reason))
+	return true, nil
+}
+
 // isIndexStale reports whether the index at dbPath is no longer worth keeping,
 // along with a human-readable reason. The metadata read is read-only so it does
 // not itself count as an access.
diff --git a/cmd/clean_test.go b/cmd/clean_test.go
index 2f7abe32..904ad9b6 100644
--- a/cmd/clean_test.go
+++ b/cmd/clean_test.go
@@ -17,6 +17,7 @@ package cmd
 import (
 	"bytes"
 	"database/sql"
+	"errors"
 	"os"
 	"path/filepath"
 	"testing"
@@ -389,6 +390,61 @@ func TestClean_NegativeDaysFails(t *testing.T) {
 	assert.DirExists(t, hashDir, "a rejected invocation must not delete anything")
 }
 
+func TestClean_MaxDaysAccepted(t *testing.T) {
+	tmp := resolvedTempDir(t)
+	t.Setenv("XDG_DATA_HOME", tmp)
+
+	project := projectDir(t, "max-days")
+	hashDir := seedIndex(t, project, embedder.DefaultModel, nil)
+
+	_, _, err := runCleanCmd(t, "--days", "106751")
+	require.NoError(t, err)
+	assert.DirExists(t, hashDir, "the largest safe whole-day duration must be accepted")
+}
+
+func TestClean_TooManyDaysFailsWithoutDeleting(t *testing.T) {
+	tmp := resolvedTempDir(t)
+	t.Setenv("XDG_DATA_HOME", tmp)
+
+	project := projectDir(t, "overflow-days")
+	hashDir := seedIndex(t, project, embedder.DefaultModel, nil)
+
+	_, _, err := runCleanCmd(t, "--days", "106752")
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "106751")
+	assert.DirExists(t, hashDir, "an overflowing duration must be rejected before cleanup")
+}
+
+func TestClean_HoldsLockDuringRemovalAndReleasesItAfterFailure(t *testing.T) {
+	tmp := resolvedTempDir(t)
+	t.Setenv("XDG_DATA_HOME", tmp)
+
+	project := projectDir(t, "remove-failure")
+	hashDir := seedIndex(t, project, embedder.DefaultModel, map[string]string{
+		"last_accessed_at": daysAgo(45),
+	})
+	lockPath := indexlock.LockPathForDB(filepath.Join(hashDir, "index.db"))
+	removeErr := errors.New("injected removal failure")
+	lockHeldDuringRemoval := false
+	originalRemoveIndexDir := removeIndexDir
+	removeIndexDir = func(path string) error {
+		assert.Equal(t, hashDir, path)
+		lockHeldDuringRemoval = indexlock.IsHeld(lockPath)
+		return removeErr
+	}
+	t.Cleanup(func() { removeIndexDir = originalRemoveIndexDir })
+
+	_, _, err := runCleanIndexes(t, tmp, 30)
+	require.ErrorIs(t, err, removeErr)
+	assert.True(t, lockHeldDuringRemoval, "cleanup must hold the index lock while removing the directory")
+	assert.DirExists(t, hashDir, "a failed removal must leave the index directory in place")
+
+	lock, lockErr := indexlock.TryAcquire(lockPath)
+	require.NoError(t, lockErr)
+	require.NotNil(t, lock, "cleanup must release the index lock after a removal failure")
+	lock.Release()
+}
+
 func TestClean_RejectsPositionalArgs(t *testing.T) {
 	require.Error(t, cleanCmd.Args(cleanCmd, []string{"/some/project"}),
 		"clean takes no positional arguments")
diff --git a/skills/reindex/SKILL.md b/skills/reindex/SKILL.md
index 71f152e3..e9c534c6 100644
--- a/skills/reindex/SKILL.md
+++ b/skills/reindex/SKILL.md
@@ -19,8 +19,9 @@ Refresh or rebuild the bundled Lumen index for the current project.
    run one via the shell:
    - `lumen index --force .` — rebuilds only the current project's index from
      scratch. Prefer this.
-   - `lumen clean --days 0 && lumen index .` — deletes every cached index on the
-     host before rebuilding. Use only when the user asks for a full wipe.
+   - `lumen clean --days 0 && lumen index .` — deletes every eligible cached
+     index except those protected by active locks, then rebuilds. Use only when
+     the user asks for a full wipe.
    - `lumen clean` — removes indexes for projects that no longer exist or have
      not been used in 30 days. Use to reclaim disk space, not to rebuild the
      current project.