diff --git a/internal/jobs/runners/worktree_prune.go b/internal/jobs/runners/worktree_prune.go
new file mode 100644
index 0000000..79295aa
--- /dev/null
+++ b/internal/jobs/runners/worktree_prune.go
@@ -0,0 +1,122 @@
+package runners
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/yan1h/agent-coding-workflow/internal/infra/notify"
+)
+
+// WorktreeRow projects the worktree fields needed for prune. OwnerID and
+// MainPath come from a JOIN performed in the production adapter (workspace
+// + project), not from the worktrees table directly.
+type WorktreeRow struct {
+	ID       uuid.UUID
+	OwnerID  uuid.UUID
+	Branch   string
+	MainPath string
+	Path     string
+}
+
+// WorktreePruneRepo is the minimal repository surface used by this runner.
+type WorktreePruneRepo interface {
+	ListWorktreesNeedingPruneWarning(ctx context.Context, lastUsedBefore time.Time) ([]WorktreeRow, error)
+	ListWorktreesNeedingPrune(ctx context.Context, lastUsedBefore time.Time) ([]WorktreeRow, error)
+	MarkPruneWarning(ctx context.Context, id uuid.UUID) error
+	TryStartPrune(ctx context.Context, id uuid.UUID) (WorktreeRow, error)
+	FinishPruneSuccess(ctx context.Context, id uuid.UUID) error
+	FinishPruneRollback(ctx context.Context, id uuid.UUID) error
+}
+
+// WorktreePruner abstracts the git CLI surface needed.
+type WorktreePruner interface {
+	WorktreeRemove(ctx context.Context, mainPath, worktreePath string) error
+}
+
+// WorktreePruneConfig matches jobs.WorktreePruneConfig minus enabled/interval
+// (managed by scheduler).
+type WorktreePruneConfig struct {
+	IdleThreshold time.Duration
+	WarningLead   time.Duration
+}
+
+// WorktreePrune is the B runner.
+type WorktreePrune struct {
+	repo WorktreePruneRepo
+	gitr WorktreePruner
+	disp Dispatcher
+	cfg  WorktreePruneConfig
+	log  *slog.Logger
+}
+
+// NewWorktreePrune constructs the runner.
+func NewWorktreePrune(repo WorktreePruneRepo, gitr WorktreePruner, disp Dispatcher, cfg WorktreePruneConfig, log *slog.Logger) *WorktreePrune {
+	if log == nil {
+		log = slog.Default()
+	}
+	return &WorktreePrune{repo: repo, gitr: gitr, disp: disp, cfg: cfg, log: log}
+}
+
+// Run executes warning phase then execution phase.
+func (r *WorktreePrune) Run(ctx context.Context) {
+	r.warningPhase(ctx)
+	r.executionPhase(ctx)
+}
+
+func (r *WorktreePrune) warningPhase(ctx context.Context) {
+	cutoff := time.Now().Add(-(r.cfg.IdleThreshold - r.cfg.WarningLead))
+	rows, err := r.repo.ListWorktreesNeedingPruneWarning(ctx, cutoff)
+	if err != nil {
+		r.log.Error("worktree_prune.list_warning", "err", err.Error())
+		return
+	}
+	for _, w := range rows {
+		if err := r.repo.MarkPruneWarning(ctx, w.ID); err != nil {
+			r.log.Error("worktree_prune.mark_warning", "id", w.ID, "err", err.Error())
+			continue
+		}
+		if derr := r.disp.Dispatch(ctx, notify.Message{
+			UserID:   w.OwnerID,
+			Topic:    "worktree.prune_pending",
+			Severity: notify.SeverityWarning,
+			Title:    "Worktree will be pruned soon",
+			Body:     "Branch " + w.Branch + " has been idle and will be removed in 3 days unless used.",
+			Metadata: map[string]any{
+				"worktree_id": w.ID.String(),
+				"branch":      w.Branch,
+			},
+			CreatedAt: time.Now().UTC(),
+		}); derr != nil {
+			r.log.Error("worktree_prune.dispatch", "id", w.ID, "err", derr.Error())
+		}
+	}
+}
+
+func (r *WorktreePrune) executionPhase(ctx context.Context) {
+	cutoff := time.Now().Add(-r.cfg.IdleThreshold)
+	rows, err := r.repo.ListWorktreesNeedingPrune(ctx, cutoff)
+	if err != nil {
+		r.log.Error("worktree_prune.list_prune", "err", err.Error())
+		return
+	}
+	for _, w := range rows {
+		started, err := r.repo.TryStartPrune(ctx, w.ID)
+		if err != nil {
+			// CAS lost (idle → other status), skip
+			continue
+		}
+		if rmErr := r.gitr.WorktreeRemove(ctx, started.MainPath, started.Path); rmErr != nil {
+			r.log.Error("worktree_prune.remove_failed", "id", w.ID, "err", rmErr.Error())
+			if rbErr := r.repo.FinishPruneRollback(ctx, w.ID); rbErr != nil {
+				r.log.Error("worktree_prune.rollback", "id", w.ID, "err", rbErr.Error())
+			}
+			continue
+		}
+		if err := r.repo.FinishPruneSuccess(ctx, w.ID); err != nil {
+			r.log.Error("worktree_prune.finish_success", "id", w.ID, "err", err.Error())
+		}
+	}
+}
diff --git a/internal/jobs/runners/worktree_prune_test.go b/internal/jobs/runners/worktree_prune_test.go
new file mode 100644
index 0000000..b6d5240
--- /dev/null
+++ b/internal/jobs/runners/worktree_prune_test.go
@@ -0,0 +1,180 @@
+package runners_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/yan1h/agent-coding-workflow/internal/infra/notify"
+	"github.com/yan1h/agent-coding-workflow/internal/jobs/runners"
+)
+
+// fakeWorktreeRepo is a fresh fake distinct from fakeWorkspaceFetchRepo.
+type fakeWorktreeRepo struct {
+	warnList    []runners.WorktreeRow
+	pruneList   []runners.WorktreeRow
+	warnListErr error
+	pruneListErr error
+
+	markedWarning  []uuid.UUID
+	markWarningErr error
+
+	tryStartResult  runners.WorktreeRow
+	tryStartErr     error
+	tryStartCalled  map[uuid.UUID]bool
+
+	finalized       map[uuid.UUID]string // "ok" | "rollback"
+	finishSuccessErr error
+	finishRollbackErr error
+}
+
+func (f *fakeWorktreeRepo) ListWorktreesNeedingPruneWarning(_ context.Context, _ time.Time) ([]runners.WorktreeRow, error) {
+	return f.warnList, f.warnListErr
+}
+
+func (f *fakeWorktreeRepo) ListWorktreesNeedingPrune(_ context.Context, _ time.Time) ([]runners.WorktreeRow, error) {
+	return f.pruneList, f.pruneListErr
+}
+
+func (f *fakeWorktreeRepo) MarkPruneWarning(_ context.Context, id uuid.UUID) error {
+	f.markedWarning = append(f.markedWarning, id)
+	return f.markWarningErr
+}
+
+func (f *fakeWorktreeRepo) TryStartPrune(_ context.Context, id uuid.UUID) (runners.WorktreeRow, error) {
+	if f.tryStartCalled == nil {
+		f.tryStartCalled = map[uuid.UUID]bool{}
+	}
+	f.tryStartCalled[id] = true
+	if f.tryStartErr != nil {
+		return runners.WorktreeRow{}, f.tryStartErr
+	}
+	return f.tryStartResult, nil
+}
+
+func (f *fakeWorktreeRepo) FinishPruneSuccess(_ context.Context, id uuid.UUID) error {
+	if f.finalized == nil {
+		f.finalized = map[uuid.UUID]string{}
+	}
+	f.finalized[id] = "ok"
+	return f.finishSuccessErr
+}
+
+func (f *fakeWorktreeRepo) FinishPruneRollback(_ context.Context, id uuid.UUID) error {
+	if f.finalized == nil {
+		f.finalized = map[uuid.UUID]string{}
+	}
+	f.finalized[id] = "rollback"
+	return f.finishRollbackErr
+}
+
+// fakePruner records WorktreeRemove calls.
+type fakePruner struct {
+	err   error
+	calls int
+}
+
+func (f *fakePruner) WorktreeRemove(_ context.Context, _, _ string) error {
+	f.calls++
+	return f.err
+}
+
+func TestWorktreePrune_WarningPhase(t *testing.T) {
+	t.Parallel()
+	id := uuid.New()
+	ownerID := uuid.New()
+	row := runners.WorktreeRow{ID: id, OwnerID: ownerID, Branch: "feat-x", MainPath: "/main", Path: "/main/.worktrees/feat-x"}
+
+	repo := &fakeWorktreeRepo{warnList: []runners.WorktreeRow{row}}
+	disp := &recordingDispatcher{}
+	gitr := &fakePruner{}
+	cfg := runners.WorktreePruneConfig{IdleThreshold: 7 * 24 * time.Hour, WarningLead: 3 * 24 * time.Hour}
+
+	r := runners.NewWorktreePrune(repo, gitr, disp, cfg, discardLogger())
+	r.Run(context.Background())
+
+	require.Len(t, repo.markedWarning, 1)
+	assert.Equal(t, id, repo.markedWarning[0])
+
+	require.Len(t, disp.msgs, 1)
+	msg := disp.msgs[0]
+	assert.Equal(t, ownerID, msg.UserID)
+	assert.Equal(t, "worktree.prune_pending", msg.Topic)
+	assert.Equal(t, notify.SeverityWarning, msg.Severity)
+
+	// execution phase: pruneList is empty, so no prune calls.
+	assert.Zero(t, gitr.calls)
+}
+
+func TestWorktreePrune_ExecutionPhaseSuccess(t *testing.T) {
+	t.Parallel()
+	id := uuid.New()
+	ownerID := uuid.New()
+	row := runners.WorktreeRow{ID: id, OwnerID: ownerID, Branch: "feat-y", MainPath: "/main", Path: "/main/.worktrees/feat-y"}
+
+	repo := &fakeWorktreeRepo{
+		pruneList:       []runners.WorktreeRow{row},
+		tryStartResult:  row,
+	}
+	gitr := &fakePruner{}
+	cfg := runners.WorktreePruneConfig{IdleThreshold: 7 * 24 * time.Hour, WarningLead: 3 * 24 * time.Hour}
+
+	r := runners.NewWorktreePrune(repo, gitr, &recordingDispatcher{}, cfg, discardLogger())
+	r.Run(context.Background())
+
+	assert.True(t, repo.tryStartCalled[id])
+	assert.Equal(t, 1, gitr.calls)
+	require.NotNil(t, repo.finalized)
+	assert.Equal(t, "ok", repo.finalized[id])
+}
+
+func TestWorktreePrune_ExecutionFailureRollsBack(t *testing.T) {
+	t.Parallel()
+	id := uuid.New()
+	ownerID := uuid.New()
+	row := runners.WorktreeRow{ID: id, OwnerID: ownerID, Branch: "feat-z", MainPath: "/main", Path: "/main/.worktrees/feat-z"}
+
+	repo := &fakeWorktreeRepo{
+		pruneList:      []runners.WorktreeRow{row},
+		tryStartResult: row,
+	}
+	gitr := &fakePruner{err: errors.New("git worktree remove failed")}
+	cfg := runners.WorktreePruneConfig{IdleThreshold: 7 * 24 * time.Hour, WarningLead: 3 * 24 * time.Hour}
+
+	r := runners.NewWorktreePrune(repo, gitr, &recordingDispatcher{}, cfg, discardLogger())
+	r.Run(context.Background())
+
+	assert.True(t, repo.tryStartCalled[id])
+	assert.Equal(t, 1, gitr.calls)
+	require.NotNil(t, repo.finalized)
+	assert.Equal(t, "rollback", repo.finalized[id])
+}
+
+func TestWorktreePrune_CASLostSkipsSilently(t *testing.T) {
+	t.Parallel()
+	id := uuid.New()
+	ownerID := uuid.New()
+	row := runners.WorktreeRow{ID: id, OwnerID: ownerID, Branch: "feat-cas", MainPath: "/main", Path: "/main/.worktrees/feat-cas"}
+
+	repo := &fakeWorktreeRepo{
+		pruneList:   []runners.WorktreeRow{row},
+		tryStartErr: errors.New("worktree no longer idle"),
+	}
+	gitr := &fakePruner{}
+	cfg := runners.WorktreePruneConfig{IdleThreshold: 7 * 24 * time.Hour, WarningLead: 3 * 24 * time.Hour}
+
+	r := runners.NewWorktreePrune(repo, gitr, &recordingDispatcher{}, cfg, discardLogger())
+	r.Run(context.Background())
+
+	// TryStartPrune was called but failed.
+	assert.True(t, repo.tryStartCalled[id])
+	// No git call.
+	assert.Zero(t, gitr.calls)
+	// No finalize for that ID.
+	assert.Empty(t, repo.finalized)
+}
diff --git a/internal/workspace/domain.go b/internal/workspace/domain.go
index 44d7187..b7685f7 100644
--- a/internal/workspace/domain.go
+++ b/internal/workspace/domain.go
@@ -83,9 +83,10 @@ type Worktree struct {
 	Path         string
 	Status       WorktreeStatus
 	ActiveHolder string // "user:<uid>" / "session:<sid>" / 空
-	AcquiredAt   *time.Time
-	LastUsedAt   time.Time
-	CreatedAt    time.Time
+	AcquiredAt     *time.Time
+	LastUsedAt     time.Time
+	PruneWarningAt *time.Time
+	CreatedAt      time.Time
 }
 
 // Credential 是 git_credentials 表的领域投影。Secret 仅在创建/更新时有值，
diff --git a/internal/workspace/queries/worktrees.sql b/internal/workspace/queries/worktrees.sql
index 255e070..fbd38e7 100644
--- a/internal/workspace/queries/worktrees.sql
+++ b/internal/workspace/queries/worktrees.sql
@@ -49,3 +49,35 @@ RETURNING *;
 
 -- name: DeleteWorktree :exec
 DELETE FROM workspace_worktrees WHERE id = $1;
+
+-- name: ListWorktreesNeedingPruneWarning :many
+SELECT * FROM workspace_worktrees
+ WHERE status = 'idle'
+   AND prune_warning_at IS NULL
+   AND last_used_at < $1
+ ORDER BY last_used_at ASC;
+
+-- name: ListWorktreesNeedingPrune :many
+SELECT * FROM workspace_worktrees
+ WHERE status = 'idle'
+   AND last_used_at < $1
+ ORDER BY last_used_at ASC;
+
+-- name: MarkPruneWarning :exec
+UPDATE workspace_worktrees
+   SET prune_warning_at = now()
+ WHERE id = $1 AND prune_warning_at IS NULL;
+
+-- name: TryStartPrune :one
+UPDATE workspace_worktrees
+   SET status = 'pruning'
+ WHERE id = $1 AND status = 'idle'
+RETURNING *;
+
+-- name: FinishPruneSuccess :exec
+DELETE FROM workspace_worktrees WHERE id = $1;
+
+-- name: FinishPruneRollback :exec
+UPDATE workspace_worktrees
+   SET status = 'idle'
+ WHERE id = $1 AND status = 'pruning';
diff --git a/internal/workspace/repository.go b/internal/workspace/repository.go
index 97113aa..a023687 100644
--- a/internal/workspace/repository.go
+++ b/internal/workspace/repository.go
@@ -50,6 +50,12 @@ type Repository interface {
 	GetWorktreeByID(ctx context.Context, id uuid.UUID) (*Worktree, error)
 	ListWorktreesByWorkspace(ctx context.Context, wsID uuid.UUID) ([]*Worktree, error)
 	DeleteWorktree(ctx context.Context, id uuid.UUID) error
+	ListWorktreesNeedingPruneWarning(ctx context.Context, lastUsedBefore time.Time) ([]*Worktree, error)
+	ListWorktreesNeedingPrune(ctx context.Context, lastUsedBefore time.Time) ([]*Worktree, error)
+	MarkPruneWarning(ctx context.Context, id uuid.UUID) error
+	TryStartPrune(ctx context.Context, id uuid.UUID) (*Worktree, error)
+	FinishPruneSuccess(ctx context.Context, id uuid.UUID) error
+	FinishPruneRollback(ctx context.Context, id uuid.UUID) error
 
 	// Credential
 	UpsertCredential(ctx context.Context, c *Credential) (*Credential, error)
@@ -240,15 +246,16 @@ func (r *pgRepo) ResetStuckSyncStatuses(ctx context.Context) error {
 
 func rowToWorktree(r workspacesqlc.WorkspaceWorktree) *Worktree {
 	return &Worktree{
-		ID:           fromPgUUID(r.ID),
-		WorkspaceID:  fromPgUUID(r.WorkspaceID),
-		Branch:       r.Branch,
-		Path:         r.Path,
-		Status:       WorktreeStatus(r.Status),
-		ActiveHolder: fromPtrString(r.ActiveHolder),
-		AcquiredAt:   fromPgTimePtr(r.AcquiredAt),
-		LastUsedAt:   r.LastUsedAt.Time,
-		CreatedAt:    r.CreatedAt.Time,
+		ID:             fromPgUUID(r.ID),
+		WorkspaceID:    fromPgUUID(r.WorkspaceID),
+		Branch:         r.Branch,
+		Path:           r.Path,
+		Status:         WorktreeStatus(r.Status),
+		ActiveHolder:   fromPtrString(r.ActiveHolder),
+		AcquiredAt:     fromPgTimePtr(r.AcquiredAt),
+		LastUsedAt:     r.LastUsedAt.Time,
+		PruneWarningAt: fromPgTimePtr(r.PruneWarningAt),
+		CreatedAt:      r.CreatedAt.Time,
 	}
 }
 
@@ -283,6 +290,64 @@ func (r *pgRepo) DeleteWorktree(ctx context.Context, id uuid.UUID) error {
 	return nil
 }
 
+func (r *pgRepo) ListWorktreesNeedingPruneWarning(ctx context.Context, lastUsedBefore time.Time) ([]*Worktree, error) {
+	ts := pgtype.Timestamptz{Time: lastUsedBefore, Valid: true}
+	rows, err := r.q.ListWorktreesNeedingPruneWarning(ctx, ts)
+	if err != nil {
+		return nil, errs.Wrap(err, errs.CodeInternal, "list worktrees needing prune warning")
+	}
+	out := make([]*Worktree, 0, len(rows))
+	for _, row := range rows {
+		out = append(out, rowToWorktree(row))
+	}
+	return out, nil
+}
+
+func (r *pgRepo) ListWorktreesNeedingPrune(ctx context.Context, lastUsedBefore time.Time) ([]*Worktree, error) {
+	ts := pgtype.Timestamptz{Time: lastUsedBefore, Valid: true}
+	rows, err := r.q.ListWorktreesNeedingPrune(ctx, ts)
+	if err != nil {
+		return nil, errs.Wrap(err, errs.CodeInternal, "list worktrees needing prune")
+	}
+	out := make([]*Worktree, 0, len(rows))
+	for _, row := range rows {
+		out = append(out, rowToWorktree(row))
+	}
+	return out, nil
+}
+
+func (r *pgRepo) MarkPruneWarning(ctx context.Context, id uuid.UUID) error {
+	if err := r.q.MarkPruneWarning(ctx, toPgUUID(id)); err != nil {
+		return errs.Wrap(err, errs.CodeInternal, "mark prune warning")
+	}
+	return nil
+}
+
+func (r *pgRepo) TryStartPrune(ctx context.Context, id uuid.UUID) (*Worktree, error) {
+	row, err := r.q.TryStartPrune(ctx, toPgUUID(id))
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, errs.New(errs.CodeWorktreeAlreadyActive, "worktree no longer idle")
+	}
+	if err != nil {
+		return nil, errs.Wrap(err, errs.CodeInternal, "try start prune")
+	}
+	return rowToWorktree(row), nil
+}
+
+func (r *pgRepo) FinishPruneSuccess(ctx context.Context, id uuid.UUID) error {
+	if err := r.q.FinishPruneSuccess(ctx, toPgUUID(id)); err != nil {
+		return errs.Wrap(err, errs.CodeInternal, "finish prune success")
+	}
+	return nil
+}
+
+func (r *pgRepo) FinishPruneRollback(ctx context.Context, id uuid.UUID) error {
+	if err := r.q.FinishPruneRollback(ctx, toPgUUID(id)); err != nil {
+		return errs.Wrap(err, errs.CodeInternal, "finish prune rollback")
+	}
+	return nil
+}
+
 // ===== Credential =====
 
 func rowToCredential(r workspacesqlc.GitCredential) *Credential {
diff --git a/internal/workspace/repository_test.go b/internal/workspace/repository_test.go
index a35481c..7d6d27c 100644
--- a/internal/workspace/repository_test.go
+++ b/internal/workspace/repository_test.go
@@ -13,6 +13,7 @@ import (
 	tcpg "github.com/testcontainers/testcontainers-go/modules/postgres"
 
 	"github.com/yan1h/agent-coding-workflow/internal/infra/db"
+	"github.com/yan1h/agent-coding-workflow/internal/infra/errs"
 )
 
 // setupRepo 起一个临时 postgres 容器、跑迁移、注入一条 user/project 行做外键，
@@ -186,3 +187,83 @@ func TestRepo_SetWorktreeActive_ClearsPruneWarning(t *testing.T) {
 	require.NoError(t, pool.QueryRow(ctx, `SELECT prune_warning_at FROM workspace_worktrees WHERE id = $1`, wtID).Scan(&pwAt))
 	require.Nil(t, pwAt, "SetWorktreeIdle should clear prune_warning_at")
 }
+
+// TestRepo_TryStartPrune_CASLossReturnsAlreadyActive 验证：对一个已变为 active 的
+// worktree 调用 TryStartPrune 会返回 CodeWorktreeAlreadyActive。
+func TestRepo_TryStartPrune_CASLossReturnsAlreadyActive(t *testing.T) {
+	t.Parallel()
+	repo, pool, pid := setupRepo(t)
+	ctx := context.Background()
+	wsID := uuid.New()
+	_, err := repo.CreateWorkspace(ctx, &Workspace{
+		ID: wsID, ProjectID: pid, Slug: "ws-cas", Name: "CAS",
+		GitRemoteURL: "https://x", DefaultBranch: "main", MainPath: "/x", SyncStatus: SyncStatusIdle,
+	})
+	require.NoError(t, err)
+
+	wtID := uuid.New()
+	require.NoError(t, repo.InTx(ctx, func(tx Tx) error {
+		_, e := tx.InsertWorktree(ctx, &Worktree{
+			ID: wtID, WorkspaceID: wsID, Branch: "cas-branch",
+			Path: "/x/.worktrees/cas", Status: WorktreeStatusIdle,
+		})
+		return e
+	}))
+
+	// 绕过 service 直接把 status 改成 active，模拟 CAS 竞争丢失。
+	_, err = pool.Exec(ctx, `UPDATE workspace_worktrees SET status = 'active' WHERE id = $1`, wtID)
+	require.NoError(t, err)
+
+	_, err = repo.TryStartPrune(ctx, wtID)
+	require.Error(t, err)
+	appErr, ok := errs.As(err)
+	require.True(t, ok, "expected AppError")
+	require.Equal(t, errs.CodeWorktreeAlreadyActive, appErr.Code)
+}
+
+// TestRepo_ListWorktreesNeedingPruneWarning_FiltersExisting 验证：已有
+// prune_warning_at 的 worktree 不会被返回，仅返回尚未标记的。
+func TestRepo_ListWorktreesNeedingPruneWarning_FiltersExisting(t *testing.T) {
+	t.Parallel()
+	repo, pool, pid := setupRepo(t)
+	ctx := context.Background()
+	wsID := uuid.New()
+	_, err := repo.CreateWorkspace(ctx, &Workspace{
+		ID: wsID, ProjectID: pid, Slug: "ws-pwf", Name: "PWF",
+		GitRemoteURL: "https://x", DefaultBranch: "main", MainPath: "/x", SyncStatus: SyncStatusIdle,
+	})
+	require.NoError(t, err)
+
+	cutoff := time.Now().Add(-24 * time.Hour)
+
+	// worktree A：没有 prune_warning_at，last_used_at 在 cutoff 之前 → 应返回。
+	wtA := uuid.New()
+	require.NoError(t, repo.InTx(ctx, func(tx Tx) error {
+		_, e := tx.InsertWorktree(ctx, &Worktree{
+			ID: wtA, WorkspaceID: wsID, Branch: "prune-a",
+			Path: "/x/.worktrees/a", Status: WorktreeStatusIdle,
+		})
+		return e
+	}))
+	_, err = pool.Exec(ctx, `UPDATE workspace_worktrees SET last_used_at = $1 WHERE id = $2`, cutoff.Add(-time.Hour), wtA)
+	require.NoError(t, err)
+
+	// worktree B：已经有 prune_warning_at，last_used_at 同样在 cutoff 前 → 不应返回。
+	wtB := uuid.New()
+	require.NoError(t, repo.InTx(ctx, func(tx Tx) error {
+		_, e := tx.InsertWorktree(ctx, &Worktree{
+			ID: wtB, WorkspaceID: wsID, Branch: "prune-b",
+			Path: "/x/.worktrees/b", Status: WorktreeStatusIdle,
+		})
+		return e
+	}))
+	_, err = pool.Exec(ctx,
+		`UPDATE workspace_worktrees SET last_used_at = $1, prune_warning_at = now() WHERE id = $2`,
+		cutoff.Add(-time.Hour), wtB)
+	require.NoError(t, err)
+
+	rows, err := repo.ListWorktreesNeedingPruneWarning(ctx, cutoff)
+	require.NoError(t, err)
+	require.Len(t, rows, 1)
+	require.Equal(t, wtA, rows[0].ID)
+}
diff --git a/internal/workspace/sqlc/worktrees.sql.go b/internal/workspace/sqlc/worktrees.sql.go
index c7f4eba..c99a50d 100644
--- a/internal/workspace/sqlc/worktrees.sql.go
+++ b/internal/workspace/sqlc/worktrees.sql.go
@@ -63,6 +63,26 @@ func (q *Queries) DeleteWorktree(ctx context.Context, id pgtype.UUID) error {
 	return err
 }
 
+const finishPruneRollback = `-- name: FinishPruneRollback :exec
+UPDATE workspace_worktrees
+   SET status = 'idle'
+ WHERE id = $1 AND status = 'pruning'
+`
+
+func (q *Queries) FinishPruneRollback(ctx context.Context, id pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, finishPruneRollback, id)
+	return err
+}
+
+const finishPruneSuccess = `-- name: FinishPruneSuccess :exec
+DELETE FROM workspace_worktrees WHERE id = $1
+`
+
+func (q *Queries) FinishPruneSuccess(ctx context.Context, id pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, finishPruneSuccess, id)
+	return err
+}
+
 const getWorktreeByBranchForUpdate = `-- name: GetWorktreeByBranchForUpdate :one
 SELECT id, workspace_id, branch, path, status, active_holder, acquired_at, last_used_at, created_at, prune_warning_at FROM workspace_worktrees
 WHERE workspace_id = $1 AND branch = $2
@@ -174,6 +194,94 @@ func (q *Queries) ListWorktreesByWorkspace(ctx context.Context, workspaceID pgty
 	return items, nil
 }
 
+const listWorktreesNeedingPrune = `-- name: ListWorktreesNeedingPrune :many
+SELECT id, workspace_id, branch, path, status, active_holder, acquired_at, last_used_at, created_at, prune_warning_at FROM workspace_worktrees
+ WHERE status = 'idle'
+   AND last_used_at < $1
+ ORDER BY last_used_at ASC
+`
+
+func (q *Queries) ListWorktreesNeedingPrune(ctx context.Context, lastUsedAt pgtype.Timestamptz) ([]WorkspaceWorktree, error) {
+	rows, err := q.db.Query(ctx, listWorktreesNeedingPrune, lastUsedAt)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []WorkspaceWorktree
+	for rows.Next() {
+		var i WorkspaceWorktree
+		if err := rows.Scan(
+			&i.ID,
+			&i.WorkspaceID,
+			&i.Branch,
+			&i.Path,
+			&i.Status,
+			&i.ActiveHolder,
+			&i.AcquiredAt,
+			&i.LastUsedAt,
+			&i.CreatedAt,
+			&i.PruneWarningAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listWorktreesNeedingPruneWarning = `-- name: ListWorktreesNeedingPruneWarning :many
+SELECT id, workspace_id, branch, path, status, active_holder, acquired_at, last_used_at, created_at, prune_warning_at FROM workspace_worktrees
+ WHERE status = 'idle'
+   AND prune_warning_at IS NULL
+   AND last_used_at < $1
+ ORDER BY last_used_at ASC
+`
+
+func (q *Queries) ListWorktreesNeedingPruneWarning(ctx context.Context, lastUsedAt pgtype.Timestamptz) ([]WorkspaceWorktree, error) {
+	rows, err := q.db.Query(ctx, listWorktreesNeedingPruneWarning, lastUsedAt)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []WorkspaceWorktree
+	for rows.Next() {
+		var i WorkspaceWorktree
+		if err := rows.Scan(
+			&i.ID,
+			&i.WorkspaceID,
+			&i.Branch,
+			&i.Path,
+			&i.Status,
+			&i.ActiveHolder,
+			&i.AcquiredAt,
+			&i.LastUsedAt,
+			&i.CreatedAt,
+			&i.PruneWarningAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const markPruneWarning = `-- name: MarkPruneWarning :exec
+UPDATE workspace_worktrees
+   SET prune_warning_at = now()
+ WHERE id = $1 AND prune_warning_at IS NULL
+`
+
+func (q *Queries) MarkPruneWarning(ctx context.Context, id pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, markPruneWarning, id)
+	return err
+}
+
 const setWorktreeActive = `-- name: SetWorktreeActive :one
 UPDATE workspace_worktrees
 SET status = 'active',
@@ -261,3 +369,28 @@ func (q *Queries) SetWorktreePruning(ctx context.Context, id pgtype.UUID) (Works
 	)
 	return i, err
 }
+
+const tryStartPrune = `-- name: TryStartPrune :one
+UPDATE workspace_worktrees
+   SET status = 'pruning'
+ WHERE id = $1 AND status = 'idle'
+RETURNING id, workspace_id, branch, path, status, active_holder, acquired_at, last_used_at, created_at, prune_warning_at
+`
+
+func (q *Queries) TryStartPrune(ctx context.Context, id pgtype.UUID) (WorkspaceWorktree, error) {
+	row := q.db.QueryRow(ctx, tryStartPrune, id)
+	var i WorkspaceWorktree
+	err := row.Scan(
+		&i.ID,
+		&i.WorkspaceID,
+		&i.Branch,
+		&i.Path,
+		&i.Status,
+		&i.ActiveHolder,
+		&i.AcquiredAt,
+		&i.LastUsedAt,
+		&i.CreatedAt,
+		&i.PruneWarningAt,
+	)
+	return i, err
+}
diff --git a/internal/workspace/workspace_service_test.go b/internal/workspace/workspace_service_test.go
index 0609c05..ae5502a 100644
--- a/internal/workspace/workspace_service_test.go
+++ b/internal/workspace/workspace_service_test.go
@@ -86,6 +86,18 @@ func (f *fakeRepo) ListWorktreesByWorkspace(_ context.Context, _ uuid.UUID) ([]*
 	return nil, nil
 }
 func (f *fakeRepo) DeleteWorktree(_ context.Context, _ uuid.UUID) error { return nil }
+func (f *fakeRepo) ListWorktreesNeedingPruneWarning(_ context.Context, _ time.Time) ([]*Worktree, error) {
+	return nil, nil
+}
+func (f *fakeRepo) ListWorktreesNeedingPrune(_ context.Context, _ time.Time) ([]*Worktree, error) {
+	return nil, nil
+}
+func (f *fakeRepo) MarkPruneWarning(_ context.Context, _ uuid.UUID) error    { return nil }
+func (f *fakeRepo) TryStartPrune(_ context.Context, _ uuid.UUID) (*Worktree, error) {
+	return nil, nil
+}
+func (f *fakeRepo) FinishPruneSuccess(_ context.Context, _ uuid.UUID) error  { return nil }
+func (f *fakeRepo) FinishPruneRollback(_ context.Context, _ uuid.UUID) error { return nil }
 func (f *fakeRepo) UpsertCredential(_ context.Context, c *Credential) (*Credential, error) {
 	cp := *c
 	f.creds[c.WorkspaceID] = &cp