diff --git a/app/vlselect/logsql/logsql.go b/app/vlselect/logsql/logsql.go
index d367a44ab7..654020d791 100644
--- a/app/vlselect/logsql/logsql.go
+++ b/app/vlselect/logsql/logsql.go
@@ -199,7 +199,7 @@ func ProcessFacetsRequest(ctx context.Context, w http.ResponseWriter, r *http.Re
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write response
 	WriteFacetsResponse(w, m)
@@ -310,7 +310,7 @@ func ProcessHitsRequest(ctx context.Context, w http.ResponseWriter, r *http.Requ
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write response
 	WriteHitsSeries(w, m)
@@ -450,7 +450,7 @@ func ProcessFieldNamesRequest(ctx context.Context, w http.ResponseWriter, r *htt
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, fieldNames)
@@ -498,7 +498,7 @@ func ProcessFieldValuesRequest(ctx context.Context, w http.ResponseWriter, r *ht
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, values)
@@ -532,7 +532,7 @@ func ProcessStreamFieldNamesRequest(ctx context.Context, w http.ResponseWriter,
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, names)
@@ -580,7 +580,7 @@ func ProcessStreamFieldValuesRequest(ctx context.Context, w http.ResponseWriter,
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, values)
@@ -618,7 +618,7 @@ func ProcessStreamIDsRequest(ctx context.Context, w http.ResponseWriter, r *http
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, streamIDs)
@@ -656,7 +656,7 @@ func ProcessStreamsRequest(ctx context.Context, w http.ResponseWriter, r *http.R
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write results
 	WriteValuesWithHitsJSON(w, streams)
@@ -1030,7 +1030,7 @@ func ProcessStatsQueryRangeRequest(ctx context.Context, w http.ResponseWriter, r
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write response
 	WriteStatsQueryRangeResponse(w, rows)
@@ -1153,7 +1153,7 @@ func ProcessStatsQueryRequest(ctx context.Context, w http.ResponseWriter, r *htt
 	h := w.Header()
 
 	h.Set("Content-Type", "application/json")
-	ca.writeResponseHeaders(h, startTime)
+	ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 	// Write response
 	WriteStatsQueryResponse(w, rows)
@@ -1245,6 +1245,9 @@ func ProcessQueryRequest(ctx context.Context, w http.ResponseWriter, r *http.Req
 		}
 	}()
 
+	qctx := ca.newQueryContext(ctx)
+	defer ca.updatePerQueryStatsMetrics()
+
 	startTime := time.Now()
 	writeResponseHeadersOnce := sync.OnceFunc(func() {
 		// Write response headers
@@ -1255,7 +1258,7 @@ func ProcessQueryRequest(ctx context.Context, w http.ResponseWriter, r *http.Req
 		} else {
 			h.Set("Content-Type", "application/stream+json")
 		}
-		ca.writeResponseHeaders(h, startTime)
+		ca.writeResponseHeaders(h, qctx.QueryStats, startTime)
 
 		if format == "csv" {
 			_, _ = sw.Write(csvHeader)
@@ -1293,9 +1296,6 @@ func ProcessQueryRequest(ctx context.Context, w http.ResponseWriter, r *http.Req
 		}
 	}
 
-	qctx := ca.newQueryContext(ctx)
-	defer ca.updatePerQueryStatsMetrics()
-
 	// Execute the query
 	if err := vlstorage.RunQuery(qctx, writeBlock); err != nil {
 		httpserver.Errorf(w, r, "cannot execute query [%s]: %s", ca.q, err)
@@ -1808,9 +1808,9 @@ func getStringSliceFromRequest(r *http.Request, argName string) ([]string, error
 	return a, nil
 }
 
-func (ca *commonArgs) writeResponseHeaders(h http.Header, startTime time.Time) {
+func (ca *commonArgs) writeResponseHeaders(h http.Header, qs *logstorage.QueryStats, startTime time.Time) {
 	// Write request duration
-	accessControlExposeHeaders := []string{"VL-Request-Duration-Seconds"}
+	accessControlExposeHeaders := []string{"VL-Request-Duration-Seconds", "VL-Partial-Response"}
 	h.Set("VL-Request-Duration-Seconds", fmt.Sprintf("%.3f", time.Since(startTime).Seconds()))
 
 	if len(ca.tenantIDs) == 1 {
@@ -1821,12 +1821,32 @@ func (ca *commonArgs) writeResponseHeaders(h http.Header, startTime time.Time) {
 		h.Set("ProjectID", fmt.Sprintf("%d", tenantID.ProjectID))
 	}
 
+	qc := qs.QueryCompleteness
+	h.Set("VL-Partial-Response", getPartialResponseHeaderValue(qc))
+
 	for i, v := range accessControlExposeHeaders {
 		accessControlExposeHeaders[i] = http.CanonicalHeaderKey(v)
 	}
 	h.Set("Access-Control-Expose-Headers", strings.Join(accessControlExposeHeaders, ", "))
 }
 
+func getPartialResponseHeaderValue(qc logstorage.QueryCompleteness) string {
+	switch qc {
+	case logstorage.QueryCompletenessNotSet:
+		// qs is not set, means the response is flushed without waiting full response.
+		// Treat this as "unknown".
+		return "unknown"
+	case logstorage.QueryCompletenessPartial:
+		return "true"
+	case logstorage.QueryCompletenessUnknown:
+		return "unknown"
+	case logstorage.QueryCompletenessComplete:
+		return "false"
+	default:
+		panic(fmt.Errorf("BUG: unexpected QueryCompleteness value %d", qc))
+	}
+}
+
 func parseDuration(r *http.Request, argName, defaultValue string) (int64, error) {
 	s := r.FormValue(argName)
 	if s == "" {
diff --git a/app/vlstorage/netselect/netselect.go b/app/vlstorage/netselect/netselect.go
index 924c07411c..9ba65f4bd9 100644
--- a/app/vlstorage/netselect/netselect.go
+++ b/app/vlstorage/netselect/netselect.go
@@ -129,19 +129,16 @@ func newStorageNode(s *Storage, addr string, ac *promauth.Config, isTLS bool) *s
 	return sn
 }
 
-func (sn *storageNode) runQuery(qctx *logstorage.QueryContext, processBlock func(db *logstorage.DataBlock)) error {
-	args := sn.getCommonArgs(QueryProtocolVersion, qctx)
-
-	qsLocal := &logstorage.QueryStats{}
-	defer qctx.QueryStats.UpdateAtomic(qsLocal)
-
+func (sn *storageNode) runQuery(ctx context.Context, args url.Values, processBlock func(db *logstorage.DataBlock)) (*logstorage.QueryStats, error) {
 	path := "/internal/select/query"
-	responseBody, reqURL, err := sn.getResponseBodyForPathAndArgs(qctx.Context, path, args)
+	responseBody, reqURL, err := sn.getResponseBodyForPathAndArgs(ctx, path, args)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	defer responseBody.Close()
 
+	qs := &logstorage.QueryStats{}
+
 	// read the response
 	var dataLenBuf [8]byte
 	var buf []byte
@@ -151,18 +148,18 @@ func (sn *storageNode) runQuery(qctx *logstorage.QueryContext, processBlock func
 		if _, err := io.ReadFull(responseBody, dataLenBuf[:]); err != nil {
 			if errors.Is(err, io.EOF) {
 				// The end of response stream
-				return nil
+				return qs, nil
 			}
-			return fmt.Errorf("cannot read block size from %q: %w", reqURL, err)
+			return nil, fmt.Errorf("cannot read block size from %q: %w", reqURL, err)
 		}
 		blockLen := encoding.UnmarshalUint64(dataLenBuf[:])
 		if blockLen > math.MaxInt {
-			return fmt.Errorf("too big data block read from %q: %d bytes; mustn't exceed %v bytes", reqURL, blockLen, math.MaxInt)
+			return nil, fmt.Errorf("too big data block read from %q: %d bytes; mustn't exceed %v bytes", reqURL, blockLen, math.MaxInt)
 		}
 
 		buf = slicesutil.SetLength(buf, int(blockLen))
 		if _, err := io.ReadFull(responseBody, buf); err != nil {
-			return fmt.Errorf("cannot read block with size of %d bytes from %q: %w", blockLen, reqURL, err)
+			return nil, fmt.Errorf("cannot read block with size of %d bytes from %q: %w", blockLen, reqURL, err)
 		}
 
 		src := buf
@@ -171,7 +168,7 @@ func (sn *storageNode) runQuery(qctx *logstorage.QueryContext, processBlock func
 			var err error
 			buf, err = encoding.DecompressZSTD(buf, buf)
 			if err != nil {
-				return fmt.Errorf("cannot decompress data block: %w", err)
+				return nil, fmt.Errorf("cannot decompress data block: %w", err)
 			}
 			src = buf[bufLen:]
 		}
@@ -181,9 +178,9 @@ func (sn *storageNode) runQuery(qctx *logstorage.QueryContext, processBlock func
 			src = src[1:]
 
 			if isQueryStatsBlock {
-				tail, err := unmarshalQueryStats(qsLocal, src)
+				tail, err := unmarshalQueryStats(qs, src)
 				if err != nil {
-					return fmt.Errorf("cannot unmarshal query stats received from %q: %w", reqURL, err)
+					return nil, fmt.Errorf("cannot unmarshal query stats received from %q: %w", reqURL, err)
 				}
 				src = tail
 				continue
@@ -191,7 +188,7 @@ func (sn *storageNode) runQuery(qctx *logstorage.QueryContext, processBlock func
 
 			tail, vb, err := db.UnmarshalInplace(src, valuesBuf[:0])
 			if err != nil {
-				return fmt.Errorf("cannot unmarshal data block received from %q: %w", reqURL, err)
+				return nil, fmt.Errorf("cannot unmarshal data block received from %q: %w", reqURL, err)
 			}
 			valuesBuf = vb
 			src = tail
@@ -405,23 +402,37 @@ func (s *Storage) runQuery(stopCh <-chan struct{}, qctx *logstorage.QueryContext
 	ctxWithCancel, cancel := contextutil.NewStopChanContext(stopCh)
 	defer cancel()
 
-	qctxLocal := qctx.WithContext(ctxWithCancel)
-
 	errs := make([]error, len(s.sns))
+	queryStats := make([]*logstorage.QueryStats, len(s.sns))
 
 	var wg sync.WaitGroup
 	for nodeIdx := range s.sns {
 		wg.Go(func() {
 			sn := s.sns[nodeIdx]
-			err := sn.runQuery(qctxLocal, func(db *logstorage.DataBlock) {
+			args := sn.getCommonArgs(QueryProtocolVersion, qctx)
+			qs, err := sn.runQuery(ctxWithCancel, args, func(db *logstorage.DataBlock) {
 				writeBlock(uint(nodeIdx), db)
 			})
 			errs[nodeIdx] = sn.handleError(ctxWithCancel, cancel, err, qctx.AllowPartialResponse)
+			queryStats[nodeIdx] = qs
 		})
 	}
 	wg.Wait()
 
-	return getFirstError(errs, qctx.AllowPartialResponse)
+	isPartial, err := getPartialResponseError(errs, qctx.AllowPartialResponse)
+	if err != nil {
+		return err
+	}
+	qctx.QueryStats.MergeQueryCompleteness(!isPartial)
+
+	for _, qs := range queryStats {
+		if qs == nil {
+			continue
+		}
+		qctx.QueryStats.UpdateAtomic(qs)
+	}
+
+	return nil
 }
 
 // GetFieldNames executes qctx and returns field names seen in results.
@@ -512,7 +523,7 @@ func (s *Storage) DeleteRunTask(ctx context.Context, taskID string, timestamp in
 	}
 	wg.Wait()
 
-	return getFirstError(errs, allowPartialResponse)
+	return getFirstError(errs)
 }
 
 // DeleteStopTask stops the delete task with the given taskID.
@@ -538,7 +549,7 @@ func (s *Storage) DeleteStopTask(ctx context.Context, taskID string) error {
 	}
 	wg.Wait()
 
-	return getFirstError(errs, allowPartialResponse)
+	return getFirstError(errs)
 }
 
 // DeleteActiveTasks returns the list of active delete tasks started via DeleteRunTask
@@ -564,7 +575,7 @@ func (s *Storage) DeleteActiveTasks(ctx context.Context) ([]*logstorage.DeleteTa
 	}
 	wg.Wait()
 
-	if err := getFirstError(errs, allowPartialResponse); err != nil {
+	if err := getFirstError(errs); err != nil {
 		return nil, err
 	}
 
@@ -619,7 +630,7 @@ func (s *Storage) getTenantIDs(ctx context.Context, start, end int64) ([]logstor
 	}
 	wg.Wait()
 
-	if err := getFirstError(errs, allowPartialResponse); err != nil {
+	if err := getFirstError(errs); err != nil {
 		return nil, err
 	}
 
@@ -659,9 +670,11 @@ func (s *Storage) getValuesWithHits(qctx *logstorage.QueryContext, limit uint64,
 	}
 	wg.Wait()
 
-	if err := getFirstError(errs, qctx.AllowPartialResponse); err != nil {
+	isPartial, err := getPartialResponseError(errs, qctx.AllowPartialResponse)
+	if err != nil {
 		return nil, err
 	}
+	qctx.QueryStats.MergeQueryCompleteness(!isPartial)
 
 	vhs := logstorage.MergeValuesWithHits(results, limit, resetHitsOnLimitExceeded)
 
@@ -760,36 +773,57 @@ func (sn *storageNode) handleError(ctx context.Context, cancel func(), err error
 	return err
 }
 
-func getFirstError(errs []error, allowPartialResponse bool) error {
+// getPartialResponseError determines whether the query result is partial or fully failed based on allowPartialResponse.
+// If allowPartialResponse is false, the first non-nil error is returned.
+// If allowPartialResponse is true:
+// - returns (false, err) if a node returned a non-availability error.
+// - returns (false, err) if all nodes are unavailable.
+// - returns (true, nil) if at least one node succeeded.
+func getPartialResponseError(errs []error, allowPartialResponse bool) (bool, error) {
 	if len(errs) == 0 {
 		logger.Panicf("BUG: len(errs) must be bigger than 0")
 	}
 
 	if !allowPartialResponse {
-		for _, err := range errs {
-			if err != nil {
-				return err
-			}
+		return false, getFirstError(errs)
+	}
+
+	noErrors := true
+	for _, err := range errs {
+		if err != nil {
+			noErrors = false
+			break
 		}
-		return nil
+	}
+	if noErrors {
+		// Not a partial response.
+		return false, nil
 	}
 
-	// allowPartialResponse == true. Return the error only if all the backends are unavailable
-	// or if some of the backends are improperly configured.
 	for _, err := range errs {
 		if err == nil {
 			// At least a single vlstorage returned full response.
-			return nil
+			return true, nil
 		}
 		if !isUnavailableBackendError(err) {
 			// Return the first error, which isn't related to the backend unavailability, to the client,
 			// since this error may point to configuration issues, which must be fixed ASAP.
 			// Hiding this error would complicate troubleshooting of improperly configured system.
-			return fmt.Errorf("the vlstorage node is available, but it returns an error, which may point to configuration issues: %w", err)
+			return false, fmt.Errorf("the vlstorage node is available, but it returns an error, which may point to configuration issues: %w", err)
 		}
 	}
 
-	return fmt.Errorf("all the vlstorage nodes are unavailable for querying; a sample error: %w", errs[0])
+	return false, fmt.Errorf("all the vlstorage nodes are unavailable for querying; a sample error: %w", errs[0])
+}
+
+// getFirstError returns the first non-nil error in errs.
+func getFirstError(errs []error) error {
+	for _, err := range errs {
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func isUnavailableBackendError(err error) bool {
diff --git a/docs/victorialogs/CHANGELOG.md b/docs/victorialogs/CHANGELOG.md
index b3727cd118..e9c1e943de 100644
--- a/docs/victorialogs/CHANGELOG.md
+++ b/docs/victorialogs/CHANGELOG.md
@@ -32,6 +32,7 @@ according to the following docs:
 * FEATURE: [web UI](https://docs.victoriametrics.com/victorialogs/querying/#web-ui): rename field `Query time` to `Hits query` on the Hits chart panel. The change makes it clear duration of which query is displayed.
 * FEATURE: [dashboards/kubernetes-explorer](https://github.com/VictoriaMetrics/VictoriaLogs/blob/master/dashboards/victorialogs-kubernetes-explorer.json): add new dashboard for exploring Kubernetes logs via [VictoriaLogs datasource](https://docs.victoriametrics.com/victorialogs/integrations/grafana/) in Grafana. Thanks to @sias32 for [the contribution](https://github.com/VictoriaMetrics/VictoriaLogs/pull/1254)!
 * FEATURE: [File Collector](https://docs.victoriametrics.com/victorialogs/vlagent/#collect-logs-from-files): enhance glob pattern support with additional syntax: double-star `/**/` for matching nested directories (e.g. `/var/log/**/*.log`), alternatives `{a,b}` for matching multiple specific names (e.g. `{access,error}.log`), character classes `[a-z]` and `?` wildcard for single-character matching. See [#1393](https://github.com/VictoriaMetrics/VictoriaLogs/issues/1393) and [these docs](https://docs.victoriametrics.com/victorialogs/vlagent/#glob-pattern-requirements) for the full pattern syntax reference.
+* FEATURE: [querying API](https://docs.victoriametrics.com/victorialogs/querying/): expose the `VL-Partial-Response` HTTP header for all `/select/logsql/*` handlers. The header value is set to `true` if the [response is partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses), or `false` if the response is complete. For streaming queries that do not require buffering the final result in memory, this header will contain the value `unknown`. See [#718](https://github.com/VictoriaMetrics/VictoriaLogs/issues/718).
 
 * BUGFIX: [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/): fix [`unroll` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#unroll-pipe) and [`json_array_len` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#json_array_len-pipe) ignoring JSON arrays preceded by whitespace. See [#1427](https://github.com/VictoriaMetrics/VictoriaLogs/issues/1427).
 * BUGFIX: [vlagent](https://docs.victoriametrics.com/victorialogs/vlagent/): hide sensitive values passed via `-remoteWrite.proxyURL` in `/metrics`, `/flags`, and startup logs. Previously these values could be exposed in plain text. See [#1320](https://github.com/VictoriaMetrics/VictoriaLogs/pull/1320).
diff --git a/docs/victorialogs/querying/README.md b/docs/victorialogs/querying/README.md
index e3ae257e56..395975fe41 100644
--- a/docs/victorialogs/querying/README.md
+++ b/docs/victorialogs/querying/README.md
@@ -144,6 +144,7 @@ with [`vl_http_requests_total{path="/select/logsql/query"}`](https://docs.victor
 The `/select/logsql/query` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -356,6 +357,7 @@ curl http://localhost:9428/select/logsql/hits -H 'AccountID: 12' -H 'ProjectID:
 The `/select/logsql/hits` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -457,6 +459,7 @@ curl http://localhost:9428/select/logsql/facets -d 'query=_time:1h' -d 'keep_con
 The `/select/logsql/facets` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -539,6 +542,7 @@ It is used by [vmalert](https://docs.victoriametrics.com/victorialogs/vmalert/).
 The `/select/logsql/stats_query` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -656,6 +660,7 @@ It is used by [Grafana plugin for VictoriaLogs](https://docs.victoriametrics.com
 The `/select/logsql/stats_query_range` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -722,6 +727,7 @@ curl http://localhost:9428/select/logsql/stream_ids -H 'AccountID: 12' -H 'Proje
 The `/select/logsql/stream_ids` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -787,6 +793,7 @@ curl http://localhost:9428/select/logsql/streams -H 'AccountID: 12' -H 'ProjectI
 The `/select/logsql/streams` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -851,6 +858,7 @@ curl http://localhost:9428/select/logsql/stream_field_names -H 'AccountID: 12' -
 The `/select/logsql/stream_field_names` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -914,6 +922,7 @@ curl http://localhost:9428/select/logsql/stream_field_values -H 'AccountID: 12'
 The `/select/logsql/stream_field_values` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -997,6 +1006,7 @@ curl http://localhost:9428/select/logsql/field_names -H 'AccountID: 12' -H 'Proj
 The `/select/logsql/field_names` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
@@ -1065,6 +1075,7 @@ curl http://localhost:9428/select/logsql/field_values -H 'AccountID: 12' -H 'Pro
 The `/select/logsql/field_values` returns the following additional HTTP response headers:
 
 - `VL-Request-Duration-Seconds` - the duration of the query until the first response byte.
+- `VL-Partial-Response` - indicates whether the response is complete (`false`), [partial](https://docs.victoriametrics.com/victorialogs/querying/#partial-responses) due to unavailable storage nodes (`true`), or cannot be determined, e.g., for unbuffered streaming queries (`unknown`).
 - `AccountID` and `ProjectID` - the requested [tenant](https://docs.victoriametrics.com/victorialogs/#multitenancy).
 
 See also:
diff --git a/lib/logstorage/query_stats.go b/lib/logstorage/query_stats.go
index 89f58f08a2..2133b2471e 100644
--- a/lib/logstorage/query_stats.go
+++ b/lib/logstorage/query_stats.go
@@ -44,6 +44,8 @@ type QueryStats struct {
 
 	// BytesProcessedUncompressedValues is the total number of uncompressed values bytes processed during the search.
 	BytesProcessedUncompressedValues uint64
+
+	QueryCompleteness QueryCompleteness
 }
 
 // GetBytesReadTotal returns the total number of bytes read, which is tracked by qs.
@@ -66,6 +68,71 @@ func (qs *QueryStats) UpdateAtomic(src *QueryStats) {
 	atomic.AddUint64(&qs.ValuesRead, src.ValuesRead)
 	atomic.AddUint64(&qs.TimestampsRead, src.TimestampsRead)
 	atomic.AddUint64(&qs.BytesProcessedUncompressedValues, src.BytesProcessedUncompressedValues)
+
+	mergeQueryCompleteness(&qs.QueryCompleteness, &src.QueryCompleteness)
+}
+
+// QueryCompleteness indicates whether a query returned a full or partial result set.
+// Partial result only happen if the `-search.allowPartialResponse` command-line flag or the `allow_partial_response` LogsQL option is set.
+// See https://docs.victoriametrics.com/victorialogs/querying/#partial-responses
+type QueryCompleteness uint32
+
+const (
+	// QueryCompletenessNotSet indicates that the value was not set.
+	// This typically occurs in streaming queries where data is not buffered but flushed periodically without merging a final completeness status.
+	// In this case, it behaves like QueryCompletenessUnknown, except that QueryCompletenessNotSet has a lower priority during a merge than other statuses.
+	QueryCompletenessNotSet QueryCompleteness = 0
+
+	// QueryCompletenessPartial means that at least one storage failed to process the query, and the response contains partially calculated data.
+	QueryCompletenessPartial QueryCompleteness = 1
+
+	// QueryCompletenessUnknown indicates a case where it is impossible to determine whether a query is complete or partial.
+	// This occurs with streaming queries that are not buffered in memory.
+	QueryCompletenessUnknown QueryCompleteness = 2
+
+	// QueryCompletenessComplete means that the query was processed by every storage without errors, and the response is complete.
+	QueryCompletenessComplete QueryCompleteness = 3
+)
+
+func (qs *QueryStats) MergeQueryCompleteness(complete bool) {
+	v := QueryCompletenessComplete
+	if !complete {
+		v = QueryCompletenessPartial
+	}
+	mergeQueryCompleteness(&qs.QueryCompleteness, &v)
+}
+
+func mergeQueryCompleteness(dstPtr, srcPtr *QueryCompleteness) {
+	src := QueryCompleteness(atomic.LoadUint32((*uint32)(srcPtr)))
+	if src == QueryCompletenessNotSet {
+		return
+	}
+	srcPriority := getQueryCompletenessPriority(src)
+
+	for {
+		dst := QueryCompleteness(atomic.LoadUint32((*uint32)(dstPtr)))
+		dstPriority := getQueryCompletenessPriority(dst)
+		if srcPriority <= dstPriority {
+			// src priority is lower, e.g. Partial should not be overridden with Unknown.
+			return
+		}
+		if atomic.CompareAndSwapUint32((*uint32)(dstPtr), uint32(dst), uint32(src)) {
+			return
+		}
+	}
+}
+
+func getQueryCompletenessPriority(qc QueryCompleteness) uint8 {
+	switch qc {
+	case QueryCompletenessPartial:
+		return 3
+	case QueryCompletenessUnknown:
+		return 2
+	case QueryCompletenessComplete:
+		return 1
+	default:
+		return 0
+	}
 }
 
 // UpdateAtomicFromDataBlock adds query stats from db to qs.
@@ -76,9 +143,12 @@ func (qs *QueryStats) UpdateFromDataBlock(db *DataBlock) error {
 	}
 
 	var errGlobal error
-	getUint64Entry := func(name string) uint64 {
+	getUint64Entry := func(name string, required bool) uint64 {
 		c := db.GetColumnByName(name)
 		if c == nil {
+			if !required {
+				return 0
+			}
 			if errGlobal == nil {
 				errGlobal = fmt.Errorf("cannot find field %q in query stats received from the remote storage", name)
 			}
@@ -89,19 +159,27 @@ func (qs *QueryStats) UpdateFromDataBlock(db *DataBlock) error {
 		return n
 	}
 
-	qs.BytesReadColumnsHeaders += getUint64Entry("BytesReadColumnsHeaders")
-	qs.BytesReadColumnsHeaderIndexes += getUint64Entry("BytesReadColumnsHeaderIndexes")
-	qs.BytesReadBloomFilters += getUint64Entry("BytesReadBloomFilters")
-	qs.BytesReadValues += getUint64Entry("BytesReadValues")
-	qs.BytesReadTimestamps += getUint64Entry("BytesReadTimestamps")
-	qs.BytesReadBlockHeaders += getUint64Entry("BytesReadBlockHeaders")
-
-	qs.BlocksProcessed += getUint64Entry("BlocksProcessed")
-	qs.RowsProcessed += getUint64Entry("RowsProcessed")
-	qs.RowsFound += getUint64Entry("RowsFound")
-	qs.ValuesRead += getUint64Entry("ValuesRead")
-	qs.TimestampsRead += getUint64Entry("TimestampsRead")
-	qs.BytesProcessedUncompressedValues += getUint64Entry("BytesProcessedUncompressedValues")
+	qs.BytesReadColumnsHeaders += getUint64Entry("BytesReadColumnsHeaders", true)
+	qs.BytesReadColumnsHeaderIndexes += getUint64Entry("BytesReadColumnsHeaderIndexes", true)
+	qs.BytesReadBloomFilters += getUint64Entry("BytesReadBloomFilters", true)
+	qs.BytesReadValues += getUint64Entry("BytesReadValues", true)
+	qs.BytesReadTimestamps += getUint64Entry("BytesReadTimestamps", true)
+	qs.BytesReadBlockHeaders += getUint64Entry("BytesReadBlockHeaders", true)
+
+	qs.BlocksProcessed += getUint64Entry("BlocksProcessed", true)
+	qs.RowsProcessed += getUint64Entry("RowsProcessed", true)
+	qs.RowsFound += getUint64Entry("RowsFound", true)
+	qs.ValuesRead += getUint64Entry("ValuesRead", true)
+	qs.TimestampsRead += getUint64Entry("TimestampsRead", true)
+	qs.BytesProcessedUncompressedValues += getUint64Entry("BytesProcessedUncompressedValues", true)
+
+	v := QueryCompleteness(getUint64Entry("QueryCompleteness", false))
+	if v == QueryCompletenessNotSet {
+		// We received NotSet, which means a backend flushed the data without waiting for the final status.
+		// Override the value to Unknown to distinguish it from the default value (NotSet).
+		v = QueryCompletenessUnknown
+	}
+	mergeQueryCompleteness(&qs.QueryCompleteness, &v)
 
 	return errGlobal
 }
@@ -121,6 +199,9 @@ func (qs *QueryStats) CreateDataBlock(queryDurationNsecs int64) *DataBlock {
 
 	qs.addEntries(addUint64Entry, queryDurationNsecs)
 
+	// An internal field that should not be shown to the user.
+	addUint64Entry("QueryCompleteness", uint64(qs.QueryCompleteness))
+
 	return &DataBlock{
 		columns: cs,
 	}
diff --git a/lib/logstorage/storage_search.go b/lib/logstorage/storage_search.go
index 2b1f6a4497..0dd72a2da2 100644
--- a/lib/logstorage/storage_search.go
+++ b/lib/logstorage/storage_search.go
@@ -217,6 +217,9 @@ func (s *Storage) RunQuery(qctx *QueryContext, writeBlock WriteDataBlockFunc) er
 type runQueryFunc func(qctx *QueryContext, writeBlock writeBlockResultFunc) error
 
 func (s *Storage) runQuery(qctx *QueryContext, writeBlock writeBlockResultFunc) error {
+	// Mark the response as complete.
+	qctx.QueryStats.MergeQueryCompleteness(true)
+
 	qNew, err := initSubqueries(qctx, s.runQuery, false)
 	if err != nil {
 		return err