diff --git a/routers/api/actions/runner/runner.go b/routers/api/actions/runner/runner.go
index eee39760ed..0c9c2a5f4a 100644
--- a/routers/api/actions/runner/runner.go
+++ b/routers/api/actions/runner/runner.go
@@ -261,7 +261,16 @@ func (s *Service) UpdateLog(
 	}
 	ack := task.LogLength
 
-	if len(req.Msg.Rows) == 0 || req.Msg.Index > ack || int64(len(req.Msg.Rows))+req.Msg.Index <= ack {
+	// Trim rows the runner already had acked.
+	var rows []*runnerv1.LogRow
+	if req.Msg.Index <= ack && int64(len(req.Msg.Rows))+req.Msg.Index > ack {
+		rows = req.Msg.Rows[ack-req.Msg.Index:]
+	}
+
+	// Bail unless we have new rows or a NoMore to finalize. Even with
+	// NoMore, bail when the runner has outrun the server — archiving a
+	// log with a gap is worse than asking it to retry.
+	if len(rows) == 0 && (!req.Msg.NoMore || req.Msg.Index > ack) {
 		res.Msg.AckIndex = ack
 		return res, nil
 	}
@@ -270,7 +279,9 @@ func (s *Service) UpdateLog(
 		return nil, status.Errorf(codes.AlreadyExists, "log file has been archived")
 	}
 
-	rows := req.Msg.Rows[ack-req.Msg.Index:]
+	// WriteLogs is called even with no rows: with offset==0 it bootstraps
+	// an empty DBFS file so TransferLogs below has something to read when
+	// the runner finalizes a task that produced no log output.
 	ns, err := actions.WriteLogs(ctx, task.LogFilename, task.LogSize, rows)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "unable to append logs to dbfs file: %v", err)
diff --git a/tests/integration/actions_log_finalize_test.go b/tests/integration/actions_log_finalize_test.go
new file mode 100644
index 0000000000..5f6e2a0efc
--- /dev/null
+++ b/tests/integration/actions_log_finalize_test.go
@@ -0,0 +1,77 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"testing"
+
+	actions_model "code.gitea.io/gitea/models/actions"
+	auth_model "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/dbfs"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	actions_module "code.gitea.io/gitea/modules/actions"
+	"code.gitea.io/gitea/modules/storage"
+
+	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
+	"connectrpc.com/connect"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Regression for https://gitea.com/gitea/runner/issues/950: a runner that
+// finalizes a task with no log output sends UpdateLog{Rows:[], NoMore:true}.
+// The previous short-circuit on len(Rows)==0 skipped TransferLogs, leaving
+// an orphan dbfs_data row. Verify the row is now archived and removed.
+func TestActionsLogFinalizeWithoutRows(t *testing.T) {
+	onGiteaRun(t, func(t *testing.T, _ *url.URL) {
+		user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+		session := loginUser(t, user2.Name)
+		token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteRepository, auth_model.AccessTokenScopeWriteUser)
+
+		apiRepo := createActionsTestRepo(t, token, "actions-finalize-no-rows", false)
+		repo := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: apiRepo.ID})
+
+		runner := newMockRunner()
+		runner.registerAsRepoRunner(t, user2.Name, repo.Name, "mock-runner", []string{"ubuntu-latest"}, false)
+
+		const wfTreePath = ".gitea/workflows/finalize-no-rows.yml"
+		wfFileContent := fmt.Sprintf(`name: finalize-no-rows
+on:
+  push:
+    paths:
+      - '%s'
+jobs:
+  job1:
+    runs-on: ubuntu-latest
+    steps:
+      - run: noop
+`, wfTreePath)
+		createWorkflowFile(t, token, user2.Name, repo.Name, wfTreePath, getWorkflowCreateFileOptions(user2, repo.DefaultBranch, "trigger", wfFileContent))
+
+		task := runner.fetchTask(t)
+
+		resp, err := runner.client.runnerServiceClient.UpdateLog(t.Context(), connect.NewRequest(&runnerv1.UpdateLogRequest{
+			TaskId: task.Id,
+			Index:  0,
+			Rows:   nil,
+			NoMore: true,
+		}))
+		require.NoError(t, err)
+		assert.EqualValues(t, 0, resp.Msg.AckIndex)
+
+		freshTask := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionTask{ID: task.Id})
+		require.True(t, freshTask.LogInStorage, "log_in_storage must flip after empty NoMore=true")
+
+		_, err = storage.Actions.Stat(freshTask.LogFilename)
+		assert.NoError(t, err, "archived log must exist in storage")
+
+		_, err = dbfs.Open(t.Context(), actions_module.DBFSPrefix+freshTask.LogFilename)
+		assert.ErrorIs(t, err, os.ErrNotExist, "DBFS row must be cleaned up after TransferLogs")
+	})
+}