feat: auto-archive inactive chats with audit trail (#24642)

Adds a background job in `dbpurge` that periodically archives chats
inactive beyond a configurable threshold. Each archived root chat gets a
background audit entry tagged `chat_auto_archive`. Disabled by default.

* New `AutoArchiveInactiveChats` SQL query with LATERAL last-activity
subquery and partial index on archive candidates
* `site_configs`-backed `auto_archive_days` setting with admin-only PUT,
any-authenticated-user GET
* Cascade archive via `root_chat_id`; pinned chats and active threads
exempt
* Root-only audit dispatch on detached context, matching manual archive
(`patchChat`) behavior
* 11 subtests covering disabled no-op, boundary, deleted messages, child
activity, pinned exemption, multi-owner, idempotency, and batch
pagination

PR #24643 adds per-owner digest notifications.
PR #24704 adds the requisite UI controls.

> 🤖

coderd/database/dbauthz/dbauthz.go

@@ -644,6 +644,8 @@ var (
 					rbac.ResourceNotificationMessage.Type:  {policy.ActionDelete},
 					rbac.ResourceApiKey.Type:               {policy.ActionDelete},
 					rbac.ResourceAibridgeInterception.Type: {policy.ActionDelete},
+					// Chat auto-archive sets archived=true on inactive chats.
+					rbac.ResourceChat.Type: {policy.ActionRead, policy.ActionUpdate},
 				}),
 				User:    []rbac.Permission{},
 				ByOrgID: map[string]rbac.OrgPermissions{},
@@ -1593,6 +1595,16 @@ func (q *querier) ArchiveUnusedTemplateVersions(ctx context.Context, arg databas
 	return q.db.ArchiveUnusedTemplateVersions(ctx, arg)
 }
 
+func (q *querier) AutoArchiveInactiveChats(ctx context.Context, arg database.AutoArchiveInactiveChatsParams) ([]database.AutoArchiveInactiveChatsRow, error) {
+	// Background write by dbpurge. The LATERAL read of chat_messages rows
+	// happens below the RBAC boundary; only the chat row itself requires
+	// authorization.
+	if err := q.authorizeContext(ctx, policy.ActionUpdate, rbac.ResourceChat); err != nil {
+		return nil, err
+	}
+	return q.db.AutoArchiveInactiveChats(ctx, arg)
+}
+
 func (q *querier) BackoffChatDiffStatus(ctx context.Context, arg database.BackoffChatDiffStatusParams) error {
 	// This is a system-level operation used by the gitsync
 	// background worker to reschedule failed refreshes. Same
@@ -2557,6 +2569,17 @@ func (q *querier) GetAuthorizationUserRoles(ctx context.Context, userID uuid.UUI
 	return q.db.GetAuthorizationUserRoles(ctx, userID)
 }
 
+func (q *querier) GetChatAutoArchiveDays(ctx context.Context, defaultAutoArchiveDays int32) (int32, error) {
+	// Chat auto-archive is a deployment-wide config read by dbpurge.
+	// Only requires a valid actor in context. The HTTP GET handler
+	// allows any authenticated user; the PUT handler enforces admin
+	// access (policy.ActionUpdate on ResourceDeploymentConfig).
+	if _, ok := ActorFromContext(ctx); !ok {
+		return 0, ErrNoActor
+	}
+	return q.db.GetChatAutoArchiveDays(ctx, defaultAutoArchiveDays)
+}
+
 func (q *querier) GetChatByID(ctx context.Context, id uuid.UUID) (database.Chat, error) {
 	return fetch(q.log, q.auth, q.db.GetChatByID)(ctx, id)
 }
@@ -7374,6 +7397,13 @@ func (q *querier) UpsertBoundaryUsageStats(ctx context.Context, arg database.Ups
 	return q.db.UpsertBoundaryUsageStats(ctx, arg)
 }
 
+func (q *querier) UpsertChatAutoArchiveDays(ctx context.Context, autoArchiveDays int32) error {
+	if err := q.authorizeContext(ctx, policy.ActionUpdate, rbac.ResourceDeploymentConfig); err != nil {
+		return err
+	}
+	return q.db.UpsertChatAutoArchiveDays(ctx, autoArchiveDays)
+}
+
 func (q *querier) UpsertChatDebugLoggingAllowUsers(ctx context.Context, allowUsers bool) error {
 	if err := q.authorizeContext(ctx, policy.ActionUpdate, rbac.ResourceDeploymentConfig); err != nil {
 		return err

coderd/database/dbauthz/dbauthz_test.go

@@ -741,6 +741,18 @@ func (s *MethodTestSuite) TestChats() {
 		dbm.EXPECT().UpsertChatRetentionDays(gomock.Any(), int32(30)).Return(nil).AnyTimes()
 		check.Args(int32(30)).Asserts(rbac.ResourceDeploymentConfig, policy.ActionUpdate)
 	}))
+	s.Run("GetChatAutoArchiveDays", s.Mocked(func(dbm *dbmock.MockStore, _ *gofakeit.Faker, check *expects) {
+		dbm.EXPECT().GetChatAutoArchiveDays(gomock.Any(), gomock.Any()).Return(int32(90), nil).AnyTimes()
+		check.Args(int32(90)).Asserts()
+	}))
+	s.Run("UpsertChatAutoArchiveDays", s.Mocked(func(dbm *dbmock.MockStore, _ *gofakeit.Faker, check *expects) {
+		dbm.EXPECT().UpsertChatAutoArchiveDays(gomock.Any(), int32(90)).Return(nil).AnyTimes()
+		check.Args(int32(90)).Asserts(rbac.ResourceDeploymentConfig, policy.ActionUpdate)
+	}))
+	s.Run("AutoArchiveInactiveChats", s.Mocked(func(dbm *dbmock.MockStore, _ *gofakeit.Faker, check *expects) {
+		dbm.EXPECT().AutoArchiveInactiveChats(gomock.Any(), database.AutoArchiveInactiveChatsParams{}).Return([]database.AutoArchiveInactiveChatsRow{}, nil).AnyTimes()
+		check.Args(database.AutoArchiveInactiveChatsParams{}).Asserts(rbac.ResourceChat, policy.ActionUpdate)
+	}))
 	s.Run("GetChatMessageByID", s.Mocked(func(dbm *dbmock.MockStore, faker *gofakeit.Faker, check *expects) {
 		chat := testutil.Fake(s.T(), faker, database.Chat{})
 		msg := testutil.Fake(s.T(), faker, database.ChatMessage{ChatID: chat.ID})

coderd/database/dbmetrics/querymetrics.go

@@ -176,6 +176,14 @@ func (m queryMetricsStore) ArchiveUnusedTemplateVersions(ctx context.Context, ar
 	return r0, r1
 }
 
+func (m queryMetricsStore) AutoArchiveInactiveChats(ctx context.Context, arg database.AutoArchiveInactiveChatsParams) ([]database.AutoArchiveInactiveChatsRow, error) {
+	start := time.Now()
+	r0, r1 := m.s.AutoArchiveInactiveChats(ctx, arg)
+	m.queryLatencies.WithLabelValues("AutoArchiveInactiveChats").Observe(time.Since(start).Seconds())
+	m.queryCounts.WithLabelValues(httpmw.ExtractHTTPRoute(ctx), httpmw.ExtractHTTPMethod(ctx), "AutoArchiveInactiveChats").Inc()
+	return r0, r1
+}
+
 func (m queryMetricsStore) BackoffChatDiffStatus(ctx context.Context, arg database.BackoffChatDiffStatusParams) error {
 	start := time.Now()
 	r0 := m.s.BackoffChatDiffStatus(ctx, arg)
@@ -1112,6 +1120,14 @@ func (m queryMetricsStore) GetAuthorizationUserRoles(ctx context.Context, userID
 	return r0, r1
 }
 
+func (m queryMetricsStore) GetChatAutoArchiveDays(ctx context.Context, defaultAutoArchiveDays int32) (int32, error) {
+	start := time.Now()
+	r0, r1 := m.s.GetChatAutoArchiveDays(ctx, defaultAutoArchiveDays)
+	m.queryLatencies.WithLabelValues("GetChatAutoArchiveDays").Observe(time.Since(start).Seconds())
+	m.queryCounts.WithLabelValues(httpmw.ExtractHTTPRoute(ctx), httpmw.ExtractHTTPMethod(ctx), "GetChatAutoArchiveDays").Inc()
+	return r0, r1
+}
+
 func (m queryMetricsStore) GetChatByID(ctx context.Context, id uuid.UUID) (database.Chat, error) {
 	start := time.Now()
 	r0, r1 := m.s.GetChatByID(ctx, id)
@@ -5272,6 +5288,14 @@ func (m queryMetricsStore) UpsertBoundaryUsageStats(ctx context.Context, arg dat
 	return r0, r1
 }
 
+func (m queryMetricsStore) UpsertChatAutoArchiveDays(ctx context.Context, autoArchiveDays int32) error {
+	start := time.Now()
+	r0 := m.s.UpsertChatAutoArchiveDays(ctx, autoArchiveDays)
+	m.queryLatencies.WithLabelValues("UpsertChatAutoArchiveDays").Observe(time.Since(start).Seconds())
+	m.queryCounts.WithLabelValues(httpmw.ExtractHTTPRoute(ctx), httpmw.ExtractHTTPMethod(ctx), "UpsertChatAutoArchiveDays").Inc()
+	return r0
+}
+
 func (m queryMetricsStore) UpsertChatDebugLoggingAllowUsers(ctx context.Context, allowUsers bool) error {
 	start := time.Now()
 	r0 := m.s.UpsertChatDebugLoggingAllowUsers(ctx, allowUsers)

coderd/database/dbmock/dbmock.go

@@ -177,6 +177,21 @@ func (mr *MockStoreMockRecorder) ArchiveUnusedTemplateVersions(ctx, arg any) *go
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ArchiveUnusedTemplateVersions", reflect.TypeOf((*MockStore)(nil).ArchiveUnusedTemplateVersions), ctx, arg)
 }
 
+// AutoArchiveInactiveChats mocks base method.
+func (m *MockStore) AutoArchiveInactiveChats(ctx context.Context, arg database.AutoArchiveInactiveChatsParams) ([]database.AutoArchiveInactiveChatsRow, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "AutoArchiveInactiveChats", ctx, arg)
+	ret0, _ := ret[0].([]database.AutoArchiveInactiveChatsRow)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// AutoArchiveInactiveChats indicates an expected call of AutoArchiveInactiveChats.
+func (mr *MockStoreMockRecorder) AutoArchiveInactiveChats(ctx, arg any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "AutoArchiveInactiveChats", reflect.TypeOf((*MockStore)(nil).AutoArchiveInactiveChats), ctx, arg)
+}
+
 // BackoffChatDiffStatus mocks base method.
 func (m *MockStore) BackoffChatDiffStatus(ctx context.Context, arg database.BackoffChatDiffStatusParams) error {
 	m.ctrl.T.Helper()
@@ -2041,6 +2056,21 @@ func (mr *MockStoreMockRecorder) GetAuthorizedWorkspacesAndAgentsByOwnerID(ctx,
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetAuthorizedWorkspacesAndAgentsByOwnerID", reflect.TypeOf((*MockStore)(nil).GetAuthorizedWorkspacesAndAgentsByOwnerID), ctx, ownerID, prepared)
 }
 
+// GetChatAutoArchiveDays mocks base method.
+func (m *MockStore) GetChatAutoArchiveDays(ctx context.Context, defaultAutoArchiveDays int32) (int32, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetChatAutoArchiveDays", ctx, defaultAutoArchiveDays)
+	ret0, _ := ret[0].(int32)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// GetChatAutoArchiveDays indicates an expected call of GetChatAutoArchiveDays.
+func (mr *MockStoreMockRecorder) GetChatAutoArchiveDays(ctx, defaultAutoArchiveDays any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetChatAutoArchiveDays", reflect.TypeOf((*MockStore)(nil).GetChatAutoArchiveDays), ctx, defaultAutoArchiveDays)
+}
+
 // GetChatByID mocks base method.
 func (m *MockStore) GetChatByID(ctx context.Context, id uuid.UUID) (database.Chat, error) {
 	m.ctrl.T.Helper()
@@ -9906,6 +9936,20 @@ func (mr *MockStoreMockRecorder) UpsertBoundaryUsageStats(ctx, arg any) *gomock.
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UpsertBoundaryUsageStats", reflect.TypeOf((*MockStore)(nil).UpsertBoundaryUsageStats), ctx, arg)
 }
 
+// UpsertChatAutoArchiveDays mocks base method.
+func (m *MockStore) UpsertChatAutoArchiveDays(ctx context.Context, autoArchiveDays int32) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "UpsertChatAutoArchiveDays", ctx, autoArchiveDays)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// UpsertChatAutoArchiveDays indicates an expected call of UpsertChatAutoArchiveDays.
+func (mr *MockStoreMockRecorder) UpsertChatAutoArchiveDays(ctx, autoArchiveDays any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UpsertChatAutoArchiveDays", reflect.TypeOf((*MockStore)(nil).UpsertChatAutoArchiveDays), ctx, autoArchiveDays)
+}
+
 // UpsertChatDebugLoggingAllowUsers mocks base method.
 func (m *MockStore) UpsertChatDebugLoggingAllowUsers(ctx context.Context, allowUsers bool) error {
 	m.ctrl.T.Helper()

coderd/database/dbpurge/dbpurge.go

@@ -3,12 +3,15 @@ package dbpurge
 import (
 	"context"
 	"io"
+	"net/http"
+	"sync/atomic"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"golang.org/x/xerrors"
 
 	"cdr.dev/slog/v3"
+	"github.com/coder/coder/v2/coderd/audit"
 	"github.com/coder/coder/v2/coderd/database"
 	"github.com/coder/coder/v2/coderd/database/dbauthz"
 	"github.com/coder/coder/v2/coderd/database/dbtime"
@@ -34,18 +37,38 @@ const (
 	// long enough to cover the maximum interval of a heartbeat event (currently
 	// 1 hour) plus some buffer.
 	maxTelemetryHeartbeatAge = 24 * time.Hour
-	// Batch sizes for chat purging. Both use 1000, which is smaller
-	// than audit/connection log batches (10000), because chat_files
-	// rows contain bytea blob data that make large batches heavier.
+	// Chat batch sizes stay smaller than audit/connection log batches because
+	// chat_files rows carry bytea blobs.
 	chatsBatchSize     = 1000
 	chatFilesBatchSize = 1000
 )
 
+// defaultChatAutoArchiveBatchSize bounds how many root chats one
+// tick will archive by default.
+const defaultChatAutoArchiveBatchSize int32 = 1000
+
+type Option func(*instance)
+
+// WithClock overrides the clock used by the purger. Defaults to
+// quartz.NewReal().
+func WithClock(clk quartz.Clock) Option {
+	return func(i *instance) { i.clk = clk }
+}
+
+// WithChatAutoArchiveBatchSize overrides how many root chats a
+// single tick will auto-archive. Defaults to
+// defaultChatAutoArchiveBatchSize (1000).
+func WithChatAutoArchiveBatchSize(n int32) Option {
+	return func(i *instance) { i.chatAutoArchiveBatchSize = n }
+}
+
 // New creates a new periodically purging database instance.
-// It is the caller's responsibility to call Close on the returned instance.
+// Callers must Close the returned instance.
 //
-// This is for cleaning up old, unused resources from the database that take up space.
-func New(ctx context.Context, logger slog.Logger, db database.Store, vals *codersdk.DeploymentValues, clk quartz.Clock, reg prometheus.Registerer) io.Closer {
+// The auditor pointer is loaded on each dispatch tick so runtime
+// entitlement changes (e.g. toggling the audit-log feature) take
+// effect without restarting the process.
+func New(ctx context.Context, logger slog.Logger, db database.Store, vals *codersdk.DeploymentValues, reg prometheus.Registerer, auditor *atomic.Pointer[audit.Auditor], opts ...Option) io.Closer {
 	closed := make(chan struct{})
 
 	ctx, cancelFunc := context.WithCancel(ctx)
@@ -69,18 +92,32 @@ func New(ctx context.Context, logger slog.Logger, db database.Store, vals *coder
 	}, []string{"record_type"})
 	reg.MustRegister(recordsPurged)
 
+	chatAutoArchiveRecords := prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace: "coderd",
+		Subsystem: "chat_auto_archive",
+		Name:      "records_archived_total",
+		Help:      "Total number of chats archived by the auto-archive job (counting both roots and cascaded children).",
+	})
+	reg.MustRegister(chatAutoArchiveRecords)
+
 	inst := &instance{
-		cancel:            cancelFunc,
-		closed:            closed,
-		logger:            logger,
-		vals:              vals,
-		clk:               clk,
-		iterationDuration: iterationDuration,
-		recordsPurged:     recordsPurged,
+		cancel:                   cancelFunc,
+		closed:                   closed,
+		logger:                   logger,
+		vals:                     vals,
+		clk:                      quartz.NewReal(),
+		auditor:                  auditor,
+		iterationDuration:        iterationDuration,
+		recordsPurged:            recordsPurged,
+		chatAutoArchiveRecords:   chatAutoArchiveRecords,
+		chatAutoArchiveBatchSize: defaultChatAutoArchiveBatchSize,
+	}
+	for _, opt := range opts {
+		opt(inst)
 	}
 
 	// Start the ticker with the initial delay.
-	ticker := clk.NewTicker(delay)
+	ticker := inst.clk.NewTicker(delay)
 	doTick := func(ctx context.Context, start time.Time) {
 		defer ticker.Reset(delay)
 		err := inst.purgeTick(ctx, db, start)
@@ -88,7 +125,7 @@ func New(ctx context.Context, logger slog.Logger, db database.Store, vals *coder
 			logger.Error(ctx, "failed to purge old database entries", slog.Error(err))
 
 			// Record metrics for failed purge iteration.
-			duration := clk.Since(start)
+			duration := inst.clk.Since(start)
 			iterationDuration.WithLabelValues("false").Observe(duration.Seconds())
 		}
 	}
@@ -97,7 +134,7 @@ func New(ctx context.Context, logger slog.Logger, db database.Store, vals *coder
 		defer close(closed)
 		defer ticker.Stop()
 		// Force an initial tick.
-		doTick(ctx, dbtime.Time(clk.Now()).UTC())
+		doTick(ctx, dbtime.Time(inst.clk.Now()).UTC())
 		for {
 			select {
 			case <-ctx.Done():
@@ -125,9 +162,19 @@ func (i *instance) purgeTick(ctx context.Context, db database.Store, start time.
 		chatRetentionDays = 0
 	}
 
+	// Same rationale as chat_retention_days: read outside the tx.
+	chatAutoArchiveDays, err := db.GetChatAutoArchiveDays(ctx, codersdk.DefaultChatAutoArchiveDays)
+	if err != nil {
+		i.logger.Warn(ctx, "failed to read chat auto-archive config, skipping auto-archive", slog.Error(err))
+		chatAutoArchiveDays = 0
+	}
+
+	// Populated inside the tx; dispatched post-commit.
+	var archivedChats []database.AutoArchiveInactiveChatsRow
+
 	// Start a transaction to grab advisory lock, we don't want to run
 	// multiple purges at the same time (multiple replicas).
-	return db.InTx(func(tx database.Store) error {
+	err = db.InTx(func(tx database.Store) error {
 		// Acquire a lock to ensure that only one instance of the
 		// purge is running at a time.
 		ok, err := tx.TryAcquireLock(ctx, database.LockIDDBPurge)
@@ -258,6 +305,20 @@ func (i *instance) purgeTick(ctx context.Context, db database.Store, start time.
 				return xerrors.Errorf("failed to delete old chat files: %w", err)
 			}
 		}
+
+		// Auto-archive runs after the delete pass so newly
+		// archived chats aren't eligible for deletion this tick.
+		if chatAutoArchiveDays > 0 {
+			archiveCutoff := start.Add(-time.Duration(chatAutoArchiveDays) * 24 * time.Hour)
+			archivedChats, err = tx.AutoArchiveInactiveChats(ctx, database.AutoArchiveInactiveChatsParams{
+				ArchiveCutoff: archiveCutoff,
+				LimitCount:    i.chatAutoArchiveBatchSize,
+			})
+			if err != nil {
+				return xerrors.Errorf("failed to auto-archive inactive chats: %w", err)
+			}
+		}
+
 		i.logger.Debug(ctx, "purged old database entries",
 			slog.F("workspace_agent_logs", purgedWorkspaceAgentLogs),
 			slog.F("expired_api_keys", expiredAPIKeys),
@@ -266,6 +327,7 @@ func (i *instance) purgeTick(ctx context.Context, db database.Store, start time.
 			slog.F("audit_logs", purgedAuditLogs),
 			slog.F("chats", purgedChats),
 			slog.F("chat_files", purgedChatFiles),
+			slog.F("auto_archived_chats", len(archivedChats)),
 			slog.F("duration", i.clk.Since(start)),
 		)
 
@@ -285,16 +347,35 @@ func (i *instance) purgeTick(ctx context.Context, db database.Store, start time.
 
 		return nil
 	}, database.DefaultTXOptions().WithID("db_purge"))
+	if err != nil {
+		return err
+	}
+
+	// Dispatch audits post-commit on a detached context so ticker
+	// cancellation doesn't interrupt the loop. No timeout: every root
+	// must be audited to avoid gaps in the trail. Children inherit
+	// their root's archival decision and are not audited individually,
+	// matching the manual archive path (patchChat audits the root only).
+	if len(archivedChats) > 0 {
+		i.chatAutoArchiveRecords.Add(float64(len(archivedChats)))
+		dispatchCtx := context.WithoutCancel(ctx)
+		i.dispatchChatAutoArchive(dispatchCtx, archivedChats)
+	}
+
+	return nil
 }
 
 type instance struct {
-	cancel            context.CancelFunc
-	closed            chan struct{}
-	logger            slog.Logger
-	vals              *codersdk.DeploymentValues
-	clk               quartz.Clock
-	iterationDuration *prometheus.HistogramVec
-	recordsPurged     *prometheus.CounterVec
+	cancel                   context.CancelFunc
+	closed                   chan struct{}
+	logger                   slog.Logger
+	vals                     *codersdk.DeploymentValues
+	clk                      quartz.Clock
+	auditor                  *atomic.Pointer[audit.Auditor]
+	iterationDuration        *prometheus.HistogramVec
+	recordsPurged            *prometheus.CounterVec
+	chatAutoArchiveRecords   prometheus.Counter
+	chatAutoArchiveBatchSize int32
 }
 
 func (i *instance) Close() error {
@@ -302,3 +383,74 @@ func (i *instance) Close() error {
 	<-i.closed
 	return nil
 }
+
+// chatFromAutoArchiveRow reshapes the query row into a database.Chat for
+// audit.Auditable[database.Chat].
+func chatFromAutoArchiveRow(logger slog.Logger, r database.AutoArchiveInactiveChatsRow) database.Chat {
+	var labels database.StringMap
+	// sqlc's StringMap override doesn't reach CTE-aliased columns, so Labels
+	// arrives as raw JSON bytes. StringMap.Scan handles []byte and nil.
+	if err := labels.Scan([]byte(r.Labels)); err != nil {
+		logger.Warn(context.Background(), "failed to parse chat labels from auto-archive row",
+			slog.F("chat_id", r.ID),
+			slog.F("raw_labels", string(r.Labels)),
+			slog.Error(err),
+		)
+	}
+	return database.Chat{
+		ID:                  r.ID,
+		OwnerID:             r.OwnerID,
+		OrganizationID:      r.OrganizationID,
+		WorkspaceID:         r.WorkspaceID,
+		BuildID:             r.BuildID,
+		AgentID:             r.AgentID,
+		Title:               r.Title,
+		Status:              r.Status,
+		WorkerID:            r.WorkerID,
+		StartedAt:           r.StartedAt,
+		HeartbeatAt:         r.HeartbeatAt,
+		CreatedAt:           r.CreatedAt,
+		UpdatedAt:           r.UpdatedAt,
+		ParentChatID:        r.ParentChatID,
+		RootChatID:          r.RootChatID,
+		LastModelConfigID:   r.LastModelConfigID,
+		Archived:            r.Archived,
+		LastError:           r.LastError,
+		Mode:                r.Mode,
+		MCPServerIDs:        r.MCPServerIDs,
+		Labels:              labels,
+		PinOrder:            r.PinOrder,
+		LastReadMessageID:   r.LastReadMessageID,
+		LastInjectedContext: r.LastInjectedContext,
+		DynamicTools:        r.DynamicTools,
+		PlanMode:            r.PlanMode,
+		ClientType:          r.ClientType,
+	}
+}
+
+// dispatchChatAutoArchive audits every archived root chat. Children
+// inherit their root's archival decision and are skipped, matching
+// the manual archive path (patchChat audits the root only). Runs on
+// a detached context so ticker cancellation cannot truncate the trail.
+func (i *instance) dispatchChatAutoArchive(ctx context.Context, archived []database.AutoArchiveInactiveChatsRow) {
+	auditor := *i.auditor.Load()
+	for _, row := range archived {
+		if row.ParentChatID.Valid {
+			continue // Children inherit root's archival; audit roots only.
+		}
+		after := chatFromAutoArchiveRow(i.logger, row)
+		before := after
+		before.Archived = false
+		audit.BackgroundAudit(ctx, &audit.BackgroundAuditParams[database.Chat]{
+			Audit:            auditor,
+			Log:              i.logger,
+			UserID:           row.OwnerID,
+			OrganizationID:   row.OrganizationID,
+			Action:           database.AuditActionWrite,
+			Old:              before,
+			New:              after,
+			Status:           http.StatusOK,
+			AdditionalFields: audit.BackgroundTaskFieldsBytes(ctx, i.logger, audit.BackgroundSubsystemChatAutoArchive),
+		})
+	}
+}

coderd/database/dbpurge/dbpurge_test.go

@@ -8,6 +8,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"slices"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -22,6 +23,7 @@ import (
 
 	"cdr.dev/slog/v3"
 	"cdr.dev/slog/v3/sloggers/slogtest"
+	"github.com/coder/coder/v2/coderd/audit"
 	"github.com/coder/coder/v2/coderd/coderdtest/promhelp"
 	"github.com/coder/coder/v2/coderd/database"
 	"github.com/coder/coder/v2/coderd/database/dbgen"
@@ -55,8 +57,9 @@ func TestPurge(t *testing.T) {
 	done := awaitDoTick(ctx, t, clk)
 	mDB := dbmock.NewMockStore(gomock.NewController(t))
 	mDB.EXPECT().GetChatRetentionDays(gomock.Any()).Return(int32(0), nil).AnyTimes()
+	mDB.EXPECT().GetChatAutoArchiveDays(gomock.Any(), codersdk.DefaultChatAutoArchiveDays).Return(int32(0), nil).AnyTimes()
 	mDB.EXPECT().InTx(gomock.Any(), database.DefaultTXOptions().WithID("db_purge")).Return(nil).Times(2)
-	purger := dbpurge.New(context.Background(), testutil.Logger(t), mDB, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	purger := dbpurge.New(context.Background(), testutil.Logger(t), mDB, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	<-done // wait for doTick() to run.
 	require.NoError(t, purger.Close())
 }
@@ -90,7 +93,7 @@ func TestMetrics(t *testing.T) {
 			Retention: codersdk.RetentionConfig{
 				APIKeys: serpent.Duration(7 * 24 * time.Hour), // 7 days retention
 			},
-		}, clk, reg)
+		}, reg, nopAuditorPtr(t), dbpurge.WithClock(clk))
 		defer closer.Close()
 		testutil.TryReceive(ctx, t, done)
 
@@ -151,6 +154,7 @@ func TestMetrics(t *testing.T) {
 		ctrl := gomock.NewController(t)
 		mDB := dbmock.NewMockStore(ctrl)
 		mDB.EXPECT().GetChatRetentionDays(gomock.Any()).Return(int32(0), nil).AnyTimes()
+		mDB.EXPECT().GetChatAutoArchiveDays(gomock.Any(), codersdk.DefaultChatAutoArchiveDays).Return(int32(0), nil).AnyTimes()
 		mDB.EXPECT().InTx(gomock.Any(), database.DefaultTXOptions().WithID("db_purge")).
 			Return(xerrors.New("simulated database error")).
 			MinTimes(1)
@@ -158,7 +162,7 @@ func TestMetrics(t *testing.T) {
 		logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: true})
 
 		done := awaitDoTick(ctx, t, clk)
-		closer := dbpurge.New(ctx, logger, mDB, &codersdk.DeploymentValues{}, clk, reg)
+		closer := dbpurge.New(ctx, logger, mDB, &codersdk.DeploymentValues{}, reg, nopAuditorPtr(t), dbpurge.WithClock(clk))
 		defer closer.Close()
 		testutil.TryReceive(ctx, t, done)
 
@@ -248,7 +252,7 @@ func TestDeleteOldWorkspaceAgentStats(t *testing.T) {
 	})
 
 	// when
-	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	defer closer.Close()
 
 	// then
@@ -273,7 +277,7 @@ func TestDeleteOldWorkspaceAgentStats(t *testing.T) {
 
 	// Start a new purger to immediately trigger delete after rollup.
 	_ = closer.Close()
-	closer = dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	closer = dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	defer closer.Close()
 
 	// then
@@ -368,7 +372,7 @@ func TestDeleteOldWorkspaceAgentLogs(t *testing.T) {
 		Retention: codersdk.RetentionConfig{
 			WorkspaceAgentLogs: serpent.Duration(7 * 24 * time.Hour),
 		},
-	}, clk, prometheus.NewRegistry())
+	}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 
 	defer closer.Close()
 	<-done // doTick() has now run.
@@ -424,6 +428,63 @@ func awaitDoTick(ctx context.Context, t *testing.T, clk *quartz.Mock) chan struc
 	return ch
 }
 
+// tickDriver drives one or more dbpurge ticks against a single
+// dbpurge.New instance. Unlike awaitDoTick it must be constructed
+// *before* dbpurge.New so its traps are installed when the forced
+// initial tick fires. awaitInitial waits for the forced tick's
+// doTick to complete without advancing the clock, so no loop
+// iteration has yet run; awaitNext then explicitly drives each
+// subsequent iteration. This keeps each tick's observable state
+// isolated and deterministic, which matters for tests where
+// per-tick work differs (e.g. batch-size pagination).
+type tickDriver struct {
+	clk       *quartz.Mock
+	trapNow   *quartz.Trap
+	trapStop  *quartz.Trap
+	trapReset *quartz.Trap
+}
+
+func newTickDriver(t *testing.T, clk *quartz.Mock) *tickDriver {
+	t.Helper()
+	d := &tickDriver{
+		clk:       clk,
+		trapNow:   clk.Trap().Now(),
+		trapStop:  clk.Trap().TickerStop(),
+		trapReset: clk.Trap().TickerReset(),
+	}
+	return d
+}
+
+// close releases all traps. Call this via defer *after* the defer
+// that closes the dbpurge instance so trap closure releases the
+// shutdown ticker.Stop() rather than blocking on it.
+func (d *tickDriver) close() {
+	d.trapReset.Close()
+	d.trapStop.Close()
+	d.trapNow.Close()
+}
+
+// awaitInitial waits for the forced initial tick's doTick to
+// complete. No loop iteration runs because the clock has not been
+// advanced.
+func (d *tickDriver) awaitInitial(ctx context.Context, t *testing.T) {
+	t.Helper()
+	d.trapNow.MustWait(ctx).MustRelease(ctx)
+	d.trapReset.MustWait(ctx).MustRelease(ctx)
+}
+
+// awaitNext advances the clock by the tick interval, lets the loop
+// receive the tick and run doTick, and waits for the ensuing
+// ticker.Reset so the driver is ready for another awaitNext.
+func (d *tickDriver) awaitNext(ctx context.Context, t *testing.T) {
+	t.Helper()
+	dur, w := d.clk.AdvanceNext()
+	require.Equal(t, 10*time.Minute, dur)
+	w.MustWait(ctx)
+	d.trapStop.MustWait(ctx).MustRelease(ctx)
+	d.trapReset.MustWait(ctx).MustRelease(ctx)
+}
+
 func assertNoWorkspaceAgentLogs(ctx context.Context, t *testing.T, db database.Store, agentID uuid.UUID) {
 	t.Helper()
 	agentLogs, err := db.GetWorkspaceAgentLogsAfter(ctx, database.GetWorkspaceAgentLogsAfterParams{
@@ -583,7 +644,7 @@ func TestDeleteOldWorkspaceAgentLogsRetention(t *testing.T) {
 			done := awaitDoTick(ctx, t, clk)
 			closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{
 				Retention: tc.retentionConfig,
-			}, clk, prometheus.NewRegistry())
+			}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 			defer closer.Close()
 			testutil.TryReceive(ctx, t, done)
 
@@ -674,7 +735,7 @@ func TestDeleteOldProvisionerDaemons(t *testing.T) {
 	require.NoError(t, err)
 
 	// when
-	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	defer closer.Close()
 
 	// then
@@ -778,7 +839,7 @@ func TestDeleteOldAuditLogConnectionEvents(t *testing.T) {
 
 	// Run the purge
 	done := awaitDoTick(ctx, t, clk)
-	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	defer closer.Close()
 	// Wait for tick
 	testutil.TryReceive(ctx, t, done)
@@ -941,7 +1002,7 @@ func TestDeleteOldTelemetryHeartbeats(t *testing.T) {
 	require.NoError(t, err)
 
 	done := awaitDoTick(ctx, t, clk)
-	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+	closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 	defer closer.Close()
 	<-done // doTick() has now run.
 
@@ -1060,7 +1121,7 @@ func TestDeleteOldConnectionLogs(t *testing.T) {
 			done := awaitDoTick(ctx, t, clk)
 			closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{
 				Retention: tc.retentionConfig,
-			}, clk, prometheus.NewRegistry())
+			}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 			defer closer.Close()
 			testutil.TryReceive(ctx, t, done)
 
@@ -1316,7 +1377,7 @@ func TestDeleteOldAIBridgeRecords(t *testing.T) {
 						Retention: serpent.Duration(tc.retention),
 					},
 				},
-			}, clk, prometheus.NewRegistry())
+			}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 			defer closer.Close()
 			testutil.TryReceive(ctx, t, done)
 
@@ -1403,7 +1464,7 @@ func TestDeleteOldAuditLogs(t *testing.T) {
 			done := awaitDoTick(ctx, t, clk)
 			closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{
 				Retention: tc.retentionConfig,
-			}, clk, prometheus.NewRegistry())
+			}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 			defer closer.Close()
 			testutil.TryReceive(ctx, t, done)
 
@@ -1493,7 +1554,7 @@ func TestDeleteOldAuditLogs(t *testing.T) {
 			Retention: codersdk.RetentionConfig{
 				AuditLogs: serpent.Duration(retentionPeriod),
 			},
-		}, clk, prometheus.NewRegistry())
+		}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 		defer closer.Close()
 		testutil.TryReceive(ctx, t, done)
 
@@ -1613,7 +1674,7 @@ func TestDeleteExpiredAPIKeys(t *testing.T) {
 			done := awaitDoTick(ctx, t, clk)
 			closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{
 				Retention: tc.retentionConfig,
-			}, clk, prometheus.NewRegistry())
+			}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 			defer closer.Close()
 			testutil.TryReceive(ctx, t, done)
 
@@ -1648,6 +1709,23 @@ func ptr[T any](v T) *T {
 	return &v
 }
 
+// nopAuditorPtr returns an atomic pointer to a nop auditor for tests.
+func nopAuditorPtr(t *testing.T) *atomic.Pointer[audit.Auditor] {
+	t.Helper()
+	nop := audit.NewNop()
+	var p atomic.Pointer[audit.Auditor]
+	p.Store(&nop)
+	return &p
+}
+
+// mockAuditorPtr wraps a *MockAuditor in an atomic pointer for tests.
+func mockAuditorPtr(m *audit.MockAuditor) *atomic.Pointer[audit.Auditor] {
+	a := audit.Auditor(m)
+	var p atomic.Pointer[audit.Auditor]
+	p.Store(&a)
+	return &p
+}
+
 //nolint:paralleltest // It uses LockIDDBPurge.
 func TestDeleteOldChatFiles(t *testing.T) {
 	now := time.Date(2025, 6, 15, 12, 0, 0, 0, time.UTC)
@@ -1742,7 +1820,7 @@ func TestDeleteOldChatFiles(t *testing.T) {
 				oldFileID := createChatFile(ctx, t, db, rawDB, deps.user.ID, deps.org.ID, now.Add(-31*24*time.Hour))
 
 				done := awaitDoTick(ctx, t, clk)
-				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 				defer closer.Close()
 				testutil.TryReceive(ctx, t, done)
 
@@ -1799,7 +1877,7 @@ func TestDeleteOldChatFiles(t *testing.T) {
 				activeChat := createChat(ctx, t, db, rawDB, deps.user.ID, deps.org.ID, deps.modelConfig.ID, false, now)
 
 				done := awaitDoTick(ctx, t, clk)
-				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 				defer closer.Close()
 				testutil.TryReceive(ctx, t, done)
 
@@ -1856,7 +1934,7 @@ func TestDeleteOldChatFiles(t *testing.T) {
 				fileBoundary := createChatFile(ctx, t, db, rawDB, deps.user.ID, deps.org.ID, now.Add(-30*24*time.Hour).Add(time.Hour))
 
 				done := awaitDoTick(ctx, t, clk)
-				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 				defer closer.Close()
 				testutil.TryReceive(ctx, t, done)
 
@@ -1936,7 +2014,7 @@ func TestDeleteOldChatFiles(t *testing.T) {
 				require.NoError(t, err)
 
 				done := awaitDoTick(ctx, t, clk)
-				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, clk, prometheus.NewRegistry())
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), nopAuditorPtr(t), dbpurge.WithClock(clk))
 				defer closer.Close()
 				testutil.TryReceive(ctx, t, done)
 
@@ -2137,3 +2215,552 @@ func TestDeleteOldChatFiles(t *testing.T) {
 		})
 	}
 }
+
+// helpers for TestAutoArchiveInactiveChats. Kept scoped to the
+// test so they don't leak into the package surface area.
+func archiveTestDeps(ctx context.Context, t *testing.T, db database.Store) chatAutoArchiveDeps {
+	t.Helper()
+	user := dbgen.User(t, db, database.User{})
+	org := dbgen.Organization(t, db, database.Organization{})
+	_ = dbgen.OrganizationMember(t, db, database.OrganizationMember{UserID: user.ID, OrganizationID: org.ID})
+	_, err := db.InsertChatProvider(ctx, database.InsertChatProviderParams{
+		Provider:             "openai",
+		DisplayName:          "OpenAI",
+		Enabled:              true,
+		CentralApiKeyEnabled: true,
+	})
+	require.NoError(t, err)
+	mc, err := db.InsertChatModelConfig(ctx, database.InsertChatModelConfigParams{
+		Provider:     "openai",
+		Model:        "test-model",
+		ContextLimit: 8192,
+		Options:      json.RawMessage("{}"),
+	})
+	require.NoError(t, err)
+	return chatAutoArchiveDeps{user: user, org: org, modelConfig: mc}
+}
+
+type chatAutoArchiveDeps struct {
+	user        database.User
+	org         database.Organization
+	modelConfig database.ChatModelConfig
+}
+
+// archiveHarness bundles the per-subtest setup shared by every
+// TestAutoArchiveInactiveChats case. Subtests read fields off the
+// harness directly instead of repeating six lines of identical
+// plumbing.
+type archiveHarness struct {
+	ctx    context.Context
+	clk    *quartz.Mock
+	db     database.Store
+	rawDB  *sql.DB
+	logger slog.Logger
+	deps   chatAutoArchiveDeps
+}
+
+func newArchiveHarness(t *testing.T, now time.Time) *archiveHarness {
+	t.Helper()
+	ctx := testutil.Context(t, testutil.WaitLong)
+	clk := quartz.NewMock(t)
+	clk.Set(now).MustWait(ctx)
+	db, _, rawDB := dbtestutil.NewDBWithSQLDB(t, dbtestutil.WithDumpOnFailure())
+	logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: true})
+	return &archiveHarness{
+		ctx:    ctx,
+		clk:    clk,
+		db:     db,
+		rawDB:  rawDB,
+		logger: logger,
+		deps:   archiveTestDeps(ctx, t, db),
+	}
+}
+
+// createArchiveChat inserts a chat with an optional backdated
+// created_at. Title is propagated through so tests can assert on
+// digest contents.
+func createArchiveChat(ctx context.Context, t *testing.T, db database.Store, rawDB *sql.DB, deps chatAutoArchiveDeps, title string, createdAt time.Time) database.Chat {
+	t.Helper()
+	chat, err := db.InsertChat(ctx, database.InsertChatParams{
+		OrganizationID:    deps.org.ID,
+		OwnerID:           deps.user.ID,
+		LastModelConfigID: deps.modelConfig.ID,
+		Title:             title,
+		Status:            database.ChatStatusWaiting,
+		ClientType:        database.ChatClientTypeUi,
+	})
+	require.NoError(t, err)
+	_, err = rawDB.ExecContext(ctx, "UPDATE chats SET created_at = $1, updated_at = $1 WHERE id = $2", createdAt, chat.ID)
+	require.NoError(t, err)
+	return chat
+}
+
+// insertTextMessage appends a non-deleted user message with a
+// backdated created_at. Used to establish "last activity" for the
+// auto-archive query's LATERAL subquery.
+func insertTextMessage(ctx context.Context, t *testing.T, db database.Store, rawDB *sql.DB, chatID, userID, modelConfigID uuid.UUID, createdAt time.Time) {
+	t.Helper()
+	msgs, err := db.InsertChatMessages(ctx, database.InsertChatMessagesParams{
+		ChatID:              chatID,
+		CreatedBy:           []uuid.UUID{userID},
+		ModelConfigID:       []uuid.UUID{modelConfigID},
+		Role:                []database.ChatMessageRole{database.ChatMessageRoleUser},
+		Content:             []string{`[{"type":"text","text":"hello"}]`},
+		ContentVersion:      []int16{0},
+		Visibility:          []database.ChatMessageVisibility{database.ChatMessageVisibilityBoth},
+		InputTokens:         []int64{0},
+		OutputTokens:        []int64{0},
+		TotalTokens:         []int64{0},
+		ReasoningTokens:     []int64{0},
+		CacheCreationTokens: []int64{0},
+		CacheReadTokens:     []int64{0},
+		ContextLimit:        []int64{0},
+		Compressed:          []bool{false},
+		TotalCostMicros:     []int64{0},
+		RuntimeMs:           []int64{0},
+		ProviderResponseID:  []string{""},
+	})
+	require.NoError(t, err)
+	require.Len(t, msgs, 1)
+	_, err = rawDB.ExecContext(ctx, "UPDATE chat_messages SET created_at = $1 WHERE id = $2", createdAt, msgs[0].ID)
+	require.NoError(t, err)
+}
+
+//nolint:paralleltest // It uses LockIDDBPurge.
+func TestAutoArchiveInactiveChats(t *testing.T) {
+	now := time.Date(2025, 6, 15, 12, 0, 0, 0, time.UTC)
+
+	tests := []struct {
+		name string
+		run  func(t *testing.T)
+	}{
+		{
+			name: "AutoArchiveDisabled",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.Zero(t, codersdk.DefaultChatAutoArchiveDays)
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, codersdk.DefaultChatAutoArchiveDays))
+
+				// Chat older than any reasonable cutoff.
+				staleChat := createArchiveChat(ctx, t, db, rawDB, deps, "stale-chat", now.Add(-365*24*time.Hour))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshed, err := db.GetChatByID(ctx, staleChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshed.Archived, "chat should stay active when auto-archive is disabled")
+				require.Empty(t, auditor.AuditLogs(), "no audit log entries expected")
+			},
+		},
+		{
+			name: "ArchivesInactiveRoot",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(90)))
+
+				// Inactive root: newest message 100 days old.
+				staleChat := createArchiveChat(ctx, t, db, rawDB, deps, "stale-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, staleChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+
+				// Active root: message 10 days old, within cutoff.
+				activeChat := createArchiveChat(ctx, t, db, rawDB, deps, "active-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, activeChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-10*24*time.Hour))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshedStale, err := db.GetChatByID(ctx, staleChat.ID)
+				require.NoError(t, err)
+				require.True(t, refreshedStale.Archived, "stale chat should be auto-archived")
+
+				refreshedActive, err := db.GetChatByID(ctx, activeChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedActive.Archived, "active chat should stay live")
+
+				logs := auditor.AuditLogs()
+				require.Len(t, logs, 1, "expected one audit entry")
+				require.Equal(t, staleChat.ID, logs[0].ResourceID)
+				require.Equal(t, database.ResourceTypeChat, logs[0].ResourceType)
+				require.Equal(t, database.AuditActionWrite, logs[0].Action)
+				require.Contains(t, string(logs[0].AdditionalFields), "chat_auto_archive",
+					"audit entry must carry the auto-archive subsystem tag")
+			},
+		},
+		{
+			name: "ExactCutoffBoundary",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(90)))
+				// The forced initial tick uses start = now. Compute
+				// the cutoff from that tick's perspective so the
+				// boundary is deterministic.
+				cutoff := now.Add(-90 * 24 * time.Hour)
+
+				// Message exactly at the cutoff: query uses strict <,
+				// so this chat must survive.
+				exactChat := createArchiveChat(ctx, t, db, rawDB, deps, "exact", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, exactChat.ID, deps.user.ID, deps.modelConfig.ID, cutoff)
+
+				// Message one second before the cutoff: should be archived.
+				justOverChat := createArchiveChat(ctx, t, db, rawDB, deps, "just-over", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, justOverChat.ID, deps.user.ID, deps.modelConfig.ID, cutoff.Add(-time.Second))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				// Use newTickDriver for precise tick control so we
+				// observe the forced initial tick's results without
+				// racing with a second tick.
+				driver := newTickDriver(t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				// Defer driver.close() after closer.Close(): defers
+				// run LIFO, so driver cleanup frees shutdown's
+				// ticker.Stop() before the dbpurge goroutine blocks
+				// on it.
+				defer closer.Close()
+				defer driver.close()
+				driver.awaitInitial(ctx, t)
+
+				refreshedExact, err := db.GetChatByID(ctx, exactChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedExact.Archived, "chat at exact cutoff must survive (strict <)")
+
+				refreshedOver, err := db.GetChatByID(ctx, justOverChat.ID)
+				require.NoError(t, err)
+				require.True(t, refreshedOver.Archived, "chat one second past cutoff must be archived")
+
+				require.Len(t, auditor.AuditLogs(), 1, "only the just-over chat should produce an audit entry")
+			},
+		},
+		{
+			name: "DeletedMessagesIgnored",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(90)))
+
+				// Chat created 120 days ago with a recent message
+				// (10 days old) that is then soft-deleted. The
+				// LATERAL subquery filters cm.deleted = false, so
+				// the chat should fall back to created_at and be
+				// archived.
+				chat := createArchiveChat(ctx, t, db, rawDB, deps, "deleted-msg", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, chat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-10*24*time.Hour))
+				// Soft-delete all messages on this chat.
+				_, err := rawDB.ExecContext(ctx, "UPDATE chat_messages SET deleted = true WHERE chat_id = $1", chat.ID)
+				require.NoError(t, err)
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshed, err := db.GetChatByID(ctx, chat.ID)
+				require.NoError(t, err)
+				require.True(t, refreshed.Archived, "chat with only deleted messages should be archived")
+				require.Len(t, auditor.AuditLogs(), 1)
+			},
+		},
+		{
+			name: "ChildActivityKeepsRootAlive",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(90)))
+
+				// Stale root with no messages of its own.
+				root := createArchiveChat(ctx, t, db, rawDB, deps, "stale-root", now.Add(-120*24*time.Hour))
+
+				// Child linked to root with a recent message (10 days old,
+				// well within the 90-day cutoff).
+				child := createArchiveChat(ctx, t, db, rawDB, deps, "active-child", now.Add(-120*24*time.Hour))
+				_, err := rawDB.ExecContext(ctx, "UPDATE chats SET parent_chat_id = $1, root_chat_id = $1 WHERE id = $2", root.ID, child.ID)
+				require.NoError(t, err)
+				insertTextMessage(ctx, t, db, rawDB, child.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-10*24*time.Hour))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshedRoot, err := db.GetChatByID(ctx, root.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedRoot.Archived, "root must stay active because child has recent activity")
+
+				refreshedChild, err := db.GetChatByID(ctx, child.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedChild.Archived, "child must stay active")
+
+				require.Empty(t, auditor.AuditLogs(), "no chats should be archived")
+			},
+		},
+		{
+			name: "SkipsActiveStatusChats",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(90)))
+
+				// Stale chats whose status prevents archiving.
+				runningChat := createArchiveChat(ctx, t, db, rawDB, deps, "running-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, runningChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+				_, err := rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusRunning, runningChat.ID)
+				require.NoError(t, err)
+
+				requiresActionChat := createArchiveChat(ctx, t, db, rawDB, deps, "requires-action-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, requiresActionChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusRequiresAction, requiresActionChat.ID)
+				require.NoError(t, err)
+
+				pendingChat := createArchiveChat(ctx, t, db, rawDB, deps, "pending-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, pendingChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusPending, pendingChat.ID)
+				require.NoError(t, err)
+
+				pausedChat := createArchiveChat(ctx, t, db, rawDB, deps, "paused-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, pausedChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusPaused, pausedChat.ID)
+				require.NoError(t, err)
+
+				// Control: a stale chat with archivable status that
+				// should be archived.
+				completedChat := createArchiveChat(ctx, t, db, rawDB, deps, "completed-chat", now.Add(-120*24*time.Hour))
+				insertTextMessage(ctx, t, db, rawDB, completedChat.ID, deps.user.ID, deps.modelConfig.ID, now.Add(-100*24*time.Hour))
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusCompleted, completedChat.ID)
+				require.NoError(t, err)
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshedRunning, err := db.GetChatByID(ctx, runningChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedRunning.Archived, "running chat must not be archived")
+
+				refreshedRA, err := db.GetChatByID(ctx, requiresActionChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedRA.Archived, "requires_action chat must not be archived")
+
+				refreshedPending, err := db.GetChatByID(ctx, pendingChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedPending.Archived, "pending chat must not be archived")
+
+				refreshedPaused, err := db.GetChatByID(ctx, pausedChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedPaused.Archived, "paused chat must not be archived")
+
+				refreshedCompleted, err := db.GetChatByID(ctx, completedChat.ID)
+				require.NoError(t, err)
+				require.True(t, refreshedCompleted.Archived, "completed stale chat should be archived")
+
+				logs := auditor.AuditLogs()
+				require.Len(t, logs, 1, "only the completed chat should produce an audit entry")
+				require.Equal(t, completedChat.ID, logs[0].ResourceID)
+			},
+		},
+		{
+			name: "SkipsPinnedAndChildren",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(30)))
+
+				// Pinned stale chat: should be skipped.
+				pinnedChat := createArchiveChat(ctx, t, db, rawDB, deps, "pinned-chat", now.Add(-90*24*time.Hour))
+				_, err := rawDB.ExecContext(ctx, "UPDATE chats SET pin_order = 1 WHERE id = $1", pinnedChat.ID)
+				require.NoError(t, err)
+
+				// Stale root with a child.
+				root := createArchiveChat(ctx, t, db, rawDB, deps, "root-chat", now.Add(-90*24*time.Hour))
+				child := createArchiveChat(ctx, t, db, rawDB, deps, "child-chat", now.Add(-90*24*time.Hour))
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET parent_chat_id = $1, root_chat_id = $1 WHERE id = $2", root.ID, child.ID)
+				require.NoError(t, err)
+				// Give the child an active status to prove the cascade is
+				// status-blind by design. If someone adds a status filter
+				// to the cascade CTE, this assertion will catch it.
+				_, err = rawDB.ExecContext(ctx, "UPDATE chats SET status = $1 WHERE id = $2", database.ChatStatusRunning, child.ID)
+				require.NoError(t, err)
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				refreshedPinned, err := db.GetChatByID(ctx, pinnedChat.ID)
+				require.NoError(t, err)
+				require.False(t, refreshedPinned.Archived, "pinned chat must be skipped")
+
+				refreshedRoot, err := db.GetChatByID(ctx, root.ID)
+				require.NoError(t, err)
+				require.True(t, refreshedRoot.Archived, "root should be archived")
+
+				refreshedChild, err := db.GetChatByID(ctx, child.ID)
+				require.NoError(t, err)
+				require.True(t, refreshedChild.Archived, "child should be cascade-archived")
+
+				// One audit entry for the root; the cascaded child is
+				// not audited individually.
+				require.Len(t, auditor.AuditLogs(), 1)
+			},
+		},
+		{
+			name: "MultipleOwners",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+				user2 := dbgen.User(t, db, database.User{})
+				_ = dbgen.OrganizationMember(t, db, database.OrganizationMember{UserID: user2.ID, OrganizationID: deps.org.ID})
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(30)))
+
+				// Two stale roots per owner, backdated well past the
+				// 30-day cutoff.
+				u1Deps := deps
+				u2Deps := chatAutoArchiveDeps{user: user2, org: deps.org, modelConfig: deps.modelConfig}
+				createArchiveChat(ctx, t, db, rawDB, u1Deps, "u1-a", now.Add(-60*24*time.Hour))
+				createArchiveChat(ctx, t, db, rawDB, u1Deps, "u1-b", now.Add(-60*24*time.Hour))
+				createArchiveChat(ctx, t, db, rawDB, u2Deps, "u2-a", now.Add(-60*24*time.Hour))
+				createArchiveChat(ctx, t, db, rawDB, u2Deps, "u2-b", now.Add(-60*24*time.Hour))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				done := awaitDoTick(ctx, t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				defer closer.Close()
+				testutil.TryReceive(ctx, t, done)
+
+				// Four audit rows, one per archived root. Each entry
+				// carries the owning UserID so downstream consumers can
+				// correlate per-owner activity.
+				logs := auditor.AuditLogs()
+				require.Len(t, logs, 4)
+				byUser := map[uuid.UUID]int{}
+				for _, l := range logs {
+					byUser[l.UserID]++
+				}
+				require.Equal(t, 2, byUser[deps.user.ID])
+				require.Equal(t, 2, byUser[user2.ID])
+			},
+		},
+		{
+			name: "SecondTickIdempotent",
+			run: func(t *testing.T) {
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(30)))
+
+				// Two stale roots seeded before the first tick.
+				firstA := createArchiveChat(ctx, t, db, rawDB, deps, "first-a", now.Add(-60*24*time.Hour))
+				firstB := createArchiveChat(ctx, t, db, rawDB, deps, "first-b", now.Add(-60*24*time.Hour))
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				driver := newTickDriver(t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk))
+				// Defer driver.close() after closer.Close(): defers
+				// run LIFO, so this frees shutdown's ticker.Stop()
+				// before the dbpurge goroutine blocks on it.
+				defer closer.Close()
+				defer driver.close()
+				driver.awaitInitial(ctx, t)
+
+				// Tick 1: both archived.
+				require.Len(t, auditor.AuditLogs(), 2, "tick 1 audits")
+
+				// Seed a third stale root between ticks so tick 2 has
+				// genuine work and we can distinguish "ignored already
+				// archived" from "ignored everything".
+				third := createArchiveChat(ctx, t, db, rawDB, deps, "second-c", now.Add(-60*24*time.Hour))
+
+				driver.awaitNext(ctx, t)
+
+				// Tick 2: exactly one new audit for the third chat;
+				// tick 1's rows must not be re-archived.
+				require.Len(t, auditor.AuditLogs(), 3, "tick 2 cumulative audits")
+
+				// All three chats should remain archived.
+				for _, id := range []uuid.UUID{firstA.ID, firstB.ID, third.ID} {
+					refreshed, err := db.GetChatByID(ctx, id)
+					require.NoError(t, err)
+					require.True(t, refreshed.Archived, "chat %s should remain archived", id)
+				}
+			},
+		},
+		{
+			name: "BatchSizePagination",
+			run: func(t *testing.T) {
+				// With 27 stale roots and batch size 20, tick 1
+				// archives 20, tick 2 archives the remaining 7, tick 3
+				// archives none. We assert the audit dispatch follows
+				// the same pattern: no dispatch runs when rows == 0,
+				// so tick 3 emits no new audits.
+				h := newArchiveHarness(t, now)
+				ctx, clk, db, rawDB, logger, deps := h.ctx, h.clk, h.db, h.rawDB, h.logger, h.deps
+
+				require.NoError(t, db.UpsertChatAutoArchiveDays(ctx, int32(30)))
+
+				const total = 27
+				for i := range total {
+					createArchiveChat(ctx, t, db, rawDB, deps,
+						fmt.Sprintf("page-%02d", i),
+						now.Add(-60*24*time.Hour))
+				}
+
+				auditor := audit.NewMock()
+				auditorPtr := mockAuditorPtr(auditor)
+				driver := newTickDriver(t, clk)
+				closer := dbpurge.New(ctx, logger, db, &codersdk.DeploymentValues{}, prometheus.NewRegistry(), auditorPtr, dbpurge.WithClock(clk), dbpurge.WithChatAutoArchiveBatchSize(20))
+				// Defer driver.close() after closer.Close() so trap
+				// cleanup frees shutdown's ticker.Stop() before the
+				// dbpurge goroutine blocks on it.
+				defer closer.Close()
+				defer driver.close()
+				driver.awaitInitial(ctx, t)
+
+				require.Len(t, auditor.AuditLogs(), 20, "tick 1 audits")
+
+				driver.awaitNext(ctx, t)
+				require.Len(t, auditor.AuditLogs(), 27, "tick 2 cumulative audits")
+
+				driver.awaitNext(ctx, t)
+				// Tick 3: nothing left to archive; dispatch is gated
+				// on len(archivedChats) > 0 so no new audits.
+				require.Len(t, auditor.AuditLogs(), 27, "tick 3 cumulative audits unchanged")
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tc.run(t)
+		})
+	}
+}

coderd/database/dump.sql

@@ -3860,6 +3860,8 @@ CREATE INDEX idx_chat_queued_messages_chat_id ON chat_queued_messages USING btre
 
 CREATE INDEX idx_chats_agent_id ON chats USING btree (agent_id) WHERE (agent_id IS NOT NULL);
 
+CREATE INDEX idx_chats_auto_archive_candidates ON chats USING btree (created_at) WHERE ((archived = false) AND (pin_order = 0) AND (parent_chat_id IS NULL));
+
 CREATE INDEX idx_chats_labels ON chats USING gin (labels);
 
 CREATE INDEX idx_chats_last_model_config_id ON chats USING btree (last_model_config_id);

coderd/database/migrations/000477_chat_auto_archive.down.sql

@@ -0,0 +1 @@
+DROP INDEX IF EXISTS idx_chats_auto_archive_candidates;

coderd/database/migrations/000477_chat_auto_archive.up.sql

@@ -0,0 +1,10 @@
+-- Partial index matching the AutoArchiveInactiveChats WHERE clause so
+-- dbpurge can skip the bulk of archived / pinned / child chats.
+-- The status predicate lives in the query, not the index, because
+-- enum values added by earlier migrations cannot be referenced in
+-- index predicates within the same transaction batch.
+CREATE INDEX IF NOT EXISTS idx_chats_auto_archive_candidates
+    ON chats (created_at)
+    WHERE archived = false
+      AND pin_order = 0
+      AND parent_chat_id IS NULL;

coderd/database/querier.go

@@ -61,6 +61,10 @@ type sqlcQuerier interface {
 	// Only unused template versions will be archived, which are any versions not
 	// referenced by the latest build of a workspace.
 	ArchiveUnusedTemplateVersions(ctx context.Context, arg ArchiveUnusedTemplateVersionsParams) ([]uuid.UUID, error)
+	// Archives inactive root chats (pinned and already-archived chats skipped),
+	// cascading to children via root_chat_id. Limits apply to roots, not total
+	// rows. Used by dbpurge.
+	AutoArchiveInactiveChats(ctx context.Context, arg AutoArchiveInactiveChatsParams) ([]AutoArchiveInactiveChatsRow, error)
 	BackoffChatDiffStatus(ctx context.Context, arg BackoffChatDiffStatusParams) error
 	BatchUpdateWorkspaceAgentMetadata(ctx context.Context, arg BatchUpdateWorkspaceAgentMetadataParams) error
 	BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg BatchUpdateWorkspaceLastUsedAtParams) error
@@ -267,6 +271,8 @@ type sqlcQuerier interface {
 	// This function returns roles for authorization purposes. Implied member roles
 	// are included.
 	GetAuthorizationUserRoles(ctx context.Context, userID uuid.UUID) (GetAuthorizationUserRolesRow, error)
+	// Auto-archive window in days. 0 disables.
+	GetChatAutoArchiveDays(ctx context.Context, defaultAutoArchiveDays int32) (int32, error)
 	GetChatByID(ctx context.Context, id uuid.UUID) (Chat, error)
 	GetChatByIDForUpdate(ctx context.Context, id uuid.UUID) (Chat, error)
 	// Per-root-chat cost breakdown for a single user within a date range.
@@ -1170,6 +1176,7 @@ type sqlcQuerier interface {
 	// cumulative values for unique counts (accurate period totals). Request counts
 	// are always deltas, accumulated in DB. Returns true if insert, false if update.
 	UpsertBoundaryUsageStats(ctx context.Context, arg UpsertBoundaryUsageStatsParams) (bool, error)
+	UpsertChatAutoArchiveDays(ctx context.Context, autoArchiveDays int32) error
 	// UpsertChatDebugLoggingAllowUsers updates the runtime admin setting that
 	// allows users to opt into chat debug logging.
 	UpsertChatDebugLoggingAllowUsers(ctx context.Context, allowUsers bool) error

coderd/database/queries.sql.go

@@ -5330,6 +5330,147 @@ func (q *sqlQuerier) ArchiveChatByID(ctx context.Context, id uuid.UUID) ([]Chat,
 	return items, nil
 }
 
+const autoArchiveInactiveChats = `-- name: AutoArchiveInactiveChats :many
+WITH to_archive AS (
+    SELECT
+        c.id,
+        -- Activity = MAX(cm.created_at) across the family, or c.created_at
+        -- when the family has no non-deleted messages.
+        COALESCE(activity.last_activity_at, c.created_at) AS last_activity_at
+    FROM chats c
+    LEFT JOIN LATERAL (
+        SELECT MAX(cm.created_at) AS last_activity_at
+        FROM chat_messages cm
+        JOIN chats fc ON fc.id = cm.chat_id
+        WHERE (fc.id = c.id OR fc.root_chat_id = c.id)
+          AND cm.deleted = false
+    ) activity ON TRUE
+    WHERE c.archived = false
+      AND c.pin_order = 0
+      AND c.parent_chat_id IS NULL -- roots only
+      AND c.created_at < $1::timestamptz
+      -- New active statuses must be added here to prevent archiving.
+      AND c.status NOT IN ('running', 'pending', 'paused', 'requires_action')
+      AND COALESCE(activity.last_activity_at, c.created_at) < $1::timestamptz
+    -- Sorting by created_at lets Postgres drive the scan from the
+    -- partial index instead of evaluating every LATERAL subquery
+    -- before sorting. All candidates are past the cutoff, so the
+    -- archive order is immaterial once the backlog drains.
+    ORDER BY c.created_at ASC
+    LIMIT $2
+),
+archived AS (
+    UPDATE chats c
+    SET archived = true, pin_order = 0, updated_at = NOW()
+    FROM to_archive t
+    WHERE (c.id = t.id OR c.root_chat_id = t.id) -- cascade to children
+      AND c.archived = false
+    RETURNING c.id, c.owner_id, c.workspace_id, c.title, c.status, c.worker_id, c.started_at, c.heartbeat_at, c.created_at, c.updated_at, c.parent_chat_id, c.root_chat_id, c.last_model_config_id, c.archived, c.last_error, c.mode, c.mcp_server_ids, c.labels, c.build_id, c.agent_id, c.pin_order, c.last_read_message_id, c.last_injected_context, c.dynamic_tools, c.organization_id, c.plan_mode, c.client_type
+)
+SELECT
+    a.id, a.owner_id, a.workspace_id, a.title, a.status, a.worker_id, a.started_at, a.heartbeat_at, a.created_at, a.updated_at, a.parent_chat_id, a.root_chat_id, a.last_model_config_id, a.archived, a.last_error, a.mode, a.mcp_server_ids, a.labels, a.build_id, a.agent_id, a.pin_order, a.last_read_message_id, a.last_injected_context, a.dynamic_tools, a.organization_id, a.plan_mode, a.client_type,
+    -- Children inherit their root's activity so last_activity_at is never null.
+    COALESCE(
+        t.last_activity_at,
+        (SELECT tr.last_activity_at FROM to_archive tr WHERE tr.id = a.root_chat_id),
+        a.created_at
+    )::timestamptz AS last_activity_at
+FROM archived a
+LEFT JOIN to_archive t ON t.id = a.id
+ORDER BY (a.root_chat_id IS NULL) DESC, a.owner_id ASC, a.created_at ASC, a.id ASC
+`
+
+type AutoArchiveInactiveChatsParams struct {
+	ArchiveCutoff time.Time `db:"archive_cutoff" json:"archive_cutoff"`
+	LimitCount    int32     `db:"limit_count" json:"limit_count"`
+}
+
+type AutoArchiveInactiveChatsRow struct {
+	ID                  uuid.UUID             `db:"id" json:"id"`
+	OwnerID             uuid.UUID             `db:"owner_id" json:"owner_id"`
+	WorkspaceID         uuid.NullUUID         `db:"workspace_id" json:"workspace_id"`
+	Title               string                `db:"title" json:"title"`
+	Status              ChatStatus            `db:"status" json:"status"`
+	WorkerID            uuid.NullUUID         `db:"worker_id" json:"worker_id"`
+	StartedAt           sql.NullTime          `db:"started_at" json:"started_at"`
+	HeartbeatAt         sql.NullTime          `db:"heartbeat_at" json:"heartbeat_at"`
+	CreatedAt           time.Time             `db:"created_at" json:"created_at"`
+	UpdatedAt           time.Time             `db:"updated_at" json:"updated_at"`
+	ParentChatID        uuid.NullUUID         `db:"parent_chat_id" json:"parent_chat_id"`
+	RootChatID          uuid.NullUUID         `db:"root_chat_id" json:"root_chat_id"`
+	LastModelConfigID   uuid.UUID             `db:"last_model_config_id" json:"last_model_config_id"`
+	Archived            bool                  `db:"archived" json:"archived"`
+	LastError           sql.NullString        `db:"last_error" json:"last_error"`
+	Mode                NullChatMode          `db:"mode" json:"mode"`
+	MCPServerIDs        []uuid.UUID           `db:"mcp_server_ids" json:"mcp_server_ids"`
+	Labels              json.RawMessage       `db:"labels" json:"labels"`
+	BuildID             uuid.NullUUID         `db:"build_id" json:"build_id"`
+	AgentID             uuid.NullUUID         `db:"agent_id" json:"agent_id"`
+	PinOrder            int32                 `db:"pin_order" json:"pin_order"`
+	LastReadMessageID   sql.NullInt64         `db:"last_read_message_id" json:"last_read_message_id"`
+	LastInjectedContext pqtype.NullRawMessage `db:"last_injected_context" json:"last_injected_context"`
+	DynamicTools        pqtype.NullRawMessage `db:"dynamic_tools" json:"dynamic_tools"`
+	OrganizationID      uuid.UUID             `db:"organization_id" json:"organization_id"`
+	PlanMode            NullChatPlanMode      `db:"plan_mode" json:"plan_mode"`
+	ClientType          ChatClientType        `db:"client_type" json:"client_type"`
+	LastActivityAt      time.Time             `db:"last_activity_at" json:"last_activity_at"`
+}
+
+// Archives inactive root chats (pinned and already-archived chats skipped),
+// cascading to children via root_chat_id. Limits apply to roots, not total
+// rows. Used by dbpurge.
+func (q *sqlQuerier) AutoArchiveInactiveChats(ctx context.Context, arg AutoArchiveInactiveChatsParams) ([]AutoArchiveInactiveChatsRow, error) {
+	rows, err := q.db.QueryContext(ctx, autoArchiveInactiveChats, arg.ArchiveCutoff, arg.LimitCount)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []AutoArchiveInactiveChatsRow
+	for rows.Next() {
+		var i AutoArchiveInactiveChatsRow
+		if err := rows.Scan(
+			&i.ID,
+			&i.OwnerID,
+			&i.WorkspaceID,
+			&i.Title,
+			&i.Status,
+			&i.WorkerID,
+			&i.StartedAt,
+			&i.HeartbeatAt,
+			&i.CreatedAt,
+			&i.UpdatedAt,
+			&i.ParentChatID,
+			&i.RootChatID,
+			&i.LastModelConfigID,
+			&i.Archived,
+			&i.LastError,
+			&i.Mode,
+			pq.Array(&i.MCPServerIDs),
+			&i.Labels,
+			&i.BuildID,
+			&i.AgentID,
+			&i.PinOrder,
+			&i.LastReadMessageID,
+			&i.LastInjectedContext,
+			&i.DynamicTools,
+			&i.OrganizationID,
+			&i.PlanMode,
+			&i.ClientType,
+			&i.LastActivityAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const backoffChatDiffStatus = `-- name: BackoffChatDiffStatus :exec
 UPDATE
     chat_diff_statuses
@@ -20367,6 +20508,22 @@ func (q *sqlQuerier) GetApplicationName(ctx context.Context) (string, error) {
 	return value, err
 }
 
+const getChatAutoArchiveDays = `-- name: GetChatAutoArchiveDays :one
+SELECT COALESCE(
+    (SELECT value::integer FROM site_configs
+     WHERE key = 'agents_chat_auto_archive_days'),
+    $1::integer
+) :: integer AS auto_archive_days
+`
+
+// Auto-archive window in days. 0 disables.
+func (q *sqlQuerier) GetChatAutoArchiveDays(ctx context.Context, defaultAutoArchiveDays int32) (int32, error) {
+	row := q.db.QueryRowContext(ctx, getChatAutoArchiveDays, defaultAutoArchiveDays)
+	var auto_archive_days int32
+	err := row.Scan(&auto_archive_days)
+	return auto_archive_days, err
+}
+
 const getChatDebugLoggingAllowUsers = `-- name: GetChatDebugLoggingAllowUsers :one
 SELECT
 	COALESCE((SELECT value = 'true' FROM site_configs WHERE key = 'agents_chat_debug_logging_allow_users'), false) :: boolean AS allow_users
@@ -20729,6 +20886,18 @@ func (q *sqlQuerier) UpsertApplicationName(ctx context.Context, value string) er
 	return err
 }
 
+const upsertChatAutoArchiveDays = `-- name: UpsertChatAutoArchiveDays :exec
+INSERT INTO site_configs (key, value)
+VALUES ('agents_chat_auto_archive_days', CAST($1 AS integer)::text)
+ON CONFLICT (key) DO UPDATE SET value = CAST($1 AS integer)::text
+WHERE site_configs.key = 'agents_chat_auto_archive_days'
+`
+
+func (q *sqlQuerier) UpsertChatAutoArchiveDays(ctx context.Context, autoArchiveDays int32) error {
+	_, err := q.db.ExecContext(ctx, upsertChatAutoArchiveDays, autoArchiveDays)
+	return err
+}
+
 const upsertChatDebugLoggingAllowUsers = `-- name: UpsertChatDebugLoggingAllowUsers :exec
 INSERT INTO site_configs (key, value)
 VALUES (

coderd/database/queries/chats.sql

@@ -1427,3 +1427,55 @@ UPDATE chat_messages SET deleted = true
 WHERE chat_id = @chat_id::uuid
     AND deleted = false
     AND content::jsonb @> '[{"type": "context-file"}]';
+
+-- name: AutoArchiveInactiveChats :many
+-- Archives inactive root chats (pinned and already-archived chats skipped),
+-- cascading to children via root_chat_id. Limits apply to roots, not total
+-- rows. Used by dbpurge.
+WITH to_archive AS (
+    SELECT
+        c.id,
+        -- Activity = MAX(cm.created_at) across the family, or c.created_at
+        -- when the family has no non-deleted messages.
+        COALESCE(activity.last_activity_at, c.created_at) AS last_activity_at
+    FROM chats c
+    LEFT JOIN LATERAL (
+        SELECT MAX(cm.created_at) AS last_activity_at
+        FROM chat_messages cm
+        JOIN chats fc ON fc.id = cm.chat_id
+        WHERE (fc.id = c.id OR fc.root_chat_id = c.id)
+          AND cm.deleted = false
+    ) activity ON TRUE
+    WHERE c.archived = false
+      AND c.pin_order = 0
+      AND c.parent_chat_id IS NULL -- roots only
+      AND c.created_at < @archive_cutoff::timestamptz
+      -- New active statuses must be added here to prevent archiving.
+      AND c.status NOT IN ('running', 'pending', 'paused', 'requires_action')
+      AND COALESCE(activity.last_activity_at, c.created_at) < @archive_cutoff::timestamptz
+    -- Sorting by created_at lets Postgres drive the scan from the
+    -- partial index instead of evaluating every LATERAL subquery
+    -- before sorting. All candidates are past the cutoff, so the
+    -- archive order is immaterial once the backlog drains.
+    ORDER BY c.created_at ASC
+    LIMIT @limit_count
+),
+archived AS (
+    UPDATE chats c
+    SET archived = true, pin_order = 0, updated_at = NOW()
+    FROM to_archive t
+    WHERE (c.id = t.id OR c.root_chat_id = t.id) -- cascade to children
+      AND c.archived = false
+    RETURNING c.*
+)
+SELECT
+    a.*,
+    -- Children inherit their root's activity so last_activity_at is never null.
+    COALESCE(
+        t.last_activity_at,
+        (SELECT tr.last_activity_at FROM to_archive tr WHERE tr.id = a.root_chat_id),
+        a.created_at
+    )::timestamptz AS last_activity_at
+FROM archived a
+LEFT JOIN to_archive t ON t.id = a.id
+ORDER BY (a.root_chat_id IS NULL) DESC, a.owner_id ASC, a.created_at ASC, a.id ASC;

coderd/database/queries/siteconfig.sql

@@ -302,3 +302,17 @@ INSERT INTO site_configs (key, value)
 VALUES ('agents_chat_retention_days', CAST(@retention_days AS integer)::text)
 ON CONFLICT (key) DO UPDATE SET value = CAST(@retention_days AS integer)::text
 WHERE site_configs.key = 'agents_chat_retention_days';
+
+-- name: GetChatAutoArchiveDays :one
+-- Auto-archive window in days. 0 disables.
+SELECT COALESCE(
+    (SELECT value::integer FROM site_configs
+     WHERE key = 'agents_chat_auto_archive_days'),
+    @default_auto_archive_days::integer
+) :: integer AS auto_archive_days;
+
+-- name: UpsertChatAutoArchiveDays :exec
+INSERT INTO site_configs (key, value)
+VALUES ('agents_chat_auto_archive_days', CAST(@auto_archive_days AS integer)::text)
+ON CONFLICT (key) DO UPDATE SET value = CAST(@auto_archive_days AS integer)::text
+WHERE site_configs.key = 'agents_chat_auto_archive_days';