diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc3a68d8b..250533bab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,12 +51,12 @@ As is traditional with a beta release, we do **not** recommend users install 3.0
 * [CHANGE] Remove deprecated `remote-write-receiver`,`promql-at-modifier`, and `promql-negative-offset` feature flags. #13456, #14526
 * [CHANGE] Remove deprecated `storage.tsdb.allow-overlapping-blocks`, `alertmanager.timeout`, and `storage.tsdb.retention` flags. #14640, #14643
 * [ENHANCEMENT] Move AM discovery page from "Monitoring status" to "Server status". #14875
+* [FEATURE] Support config reload automatically - feature flag `auto-reload-config`. #14769
 * [BUGFIX] Scrape: Do not override target parameter labels with config params. #11029
 
 ## 2.55.0-rc.0 / 2024-09-20
 
 * [FEATURE] Support UTF-8 characters in label names - feature flag `utf8-names`. #14482, #14880, #14736, #14727
-* [FEATURE] Support config reload automatically - feature flag `auto-reload-config`. #14769
 * [FEATURE] Scraping: Add the ability to set custom `http_headers` in config. #14817
 * [FEATURE] Scraping: Support feature flag `created-timestamp-zero-ingestion` in OpenMetrics. #14356, #14815
 * [FEATURE] Scraping: `scrape_failure_log_file` option to log failures to a file. #14734
@@ -69,7 +69,7 @@ As is traditional with a beta release, we do **not** recommend users install 3.0
 * [ENHANCEMENT] Remote Read client: Enable streaming remote read if the server supports it. #11379
 * [ENHANCEMENT] Remote-Write: Don't reshard if we haven't successfully sent a sample since last update. #14450
 * [ENHANCEMENT] PromQL: Delay deletion of `__name__` label to the end of the query evaluation. This is **experimental** and enabled under the feature-flag `promql-delayed-name-removal`. #14477
-* [ENHANCEMENT] PromQL: Experimental `sort_by_label` and `sort_by_label_desc` sort by all labels when label is equal. #14655
+* [ENHANCEMENT] PromQL: Experimental `sort_by_label` and `sort_by_label_desc` sort by all labels when label is equal. #14655, #14985
 * [ENHANCEMENT] PromQL: Clarify error message logged when Go runtime panic occurs during query evaluation. #14621
 * [ENHANCEMENT] PromQL: Use Kahan summation for better accuracy in `avg` and `avg_over_time`. #14413
 * [ENHANCEMENT] Tracing: Improve PromQL tracing, including showing the operation performed for aggregates, operators, and calls. #14816
diff --git a/promql/engine.go b/promql/engine.go
index 5435db0fc..0e5ab6235 100644
--- a/promql/engine.go
+++ b/promql/engine.go
@@ -1230,38 +1230,17 @@ func (ev *evaluator) rangeEval(ctx context.Context, prepSeries func(labels.Label
 		ev.currentSamples = tempNumSamples
 		// Gather input vectors for this timestamp.
 		for i := range exprs {
-			vectors[i] = vectors[i][:0]
-
+			var bh []EvalSeriesHelper
+			var sh []EvalSeriesHelper
 			if prepSeries != nil {
-				bufHelpers[i] = bufHelpers[i][:0]
-			}
-
-			for si, series := range matrixes[i] {
-				switch {
-				case len(series.Floats) > 0 && series.Floats[0].T == ts:
-					vectors[i] = append(vectors[i], Sample{Metric: series.Metric, F: series.Floats[0].F, T: ts, DropName: series.DropName})
-					// Move input vectors forward so we don't have to re-scan the same
-					// past points at the next step.
-					matrixes[i][si].Floats = series.Floats[1:]
-				case len(series.Histograms) > 0 && series.Histograms[0].T == ts:
-					vectors[i] = append(vectors[i], Sample{Metric: series.Metric, H: series.Histograms[0].H, T: ts, DropName: series.DropName})
-					matrixes[i][si].Histograms = series.Histograms[1:]
-				default:
-					continue
-				}
-				if prepSeries != nil {
-					bufHelpers[i] = append(bufHelpers[i], seriesHelpers[i][si])
-				}
-				// Don't add histogram size here because we only
-				// copy the pointer above, not the whole
-				// histogram.
-				ev.currentSamples++
-				if ev.currentSamples > ev.maxSamples {
-					ev.error(ErrTooManySamples(env))
-				}
+				bh = bufHelpers[i][:0]
+				sh = seriesHelpers[i]
 			}
+			vectors[i], bh = ev.gatherVector(ts, matrixes[i], vectors[i], bh, sh)
 			args[i] = vectors[i]
-			ev.samplesStats.UpdatePeak(ev.currentSamples)
+			if prepSeries != nil {
+				bufHelpers[i] = bh
+			}
 		}
 
 		// Make the function call.
@@ -3724,3 +3703,41 @@ func newHistogramStatsSeries(series storage.Series) *histogramStatsSeries {
 func (s histogramStatsSeries) Iterator(it chunkenc.Iterator) chunkenc.Iterator {
 	return NewHistogramStatsIterator(s.Series.Iterator(it))
 }
+
+// gatherVector gathers a Vector for ts from the series in input.
+// output is used as a buffer.
+// If bufHelpers and seriesHelpers are provided, seriesHelpers[i] is appended to bufHelpers for every input index i.
+// The gathered Vector and bufHelper are returned.
+func (ev *evaluator) gatherVector(ts int64, input Matrix, output Vector, bufHelpers, seriesHelpers []EvalSeriesHelper) (Vector, []EvalSeriesHelper) {
+	output = output[:0]
+	for i, series := range input {
+		switch {
+		case len(series.Floats) > 0 && series.Floats[0].T == ts:
+			s := series.Floats[0]
+			output = append(output, Sample{Metric: series.Metric, F: s.F, T: ts, DropName: series.DropName})
+			// Move input vectors forward so we don't have to re-scan the same
+			// past points at the next step.
+			input[i].Floats = series.Floats[1:]
+		case len(series.Histograms) > 0 && series.Histograms[0].T == ts:
+			s := series.Histograms[0]
+			output = append(output, Sample{Metric: series.Metric, H: s.H, T: ts, DropName: series.DropName})
+			input[i].Histograms = series.Histograms[1:]
+		default:
+			continue
+		}
+		if len(seriesHelpers) > 0 {
+			bufHelpers = append(bufHelpers, seriesHelpers[i])
+		}
+
+		// Don't add histogram size here because we only
+		// copy the pointer above, not the whole
+		// histogram.
+		ev.currentSamples++
+		if ev.currentSamples > ev.maxSamples {
+			ev.error(ErrTooManySamples(env))
+		}
+	}
+	ev.samplesStats.UpdatePeak(ev.currentSamples)
+
+	return output, bufHelpers
+}
diff --git a/promql/functions.go b/promql/functions.go
index 4333cb5ce..054365512 100644
--- a/promql/functions.go
+++ b/promql/functions.go
@@ -415,22 +415,12 @@ func funcSortDesc(vals []parser.Value, args parser.Expressions, enh *EvalNodeHel
 
 // === sort_by_label(vector parser.ValueTypeVector, label parser.ValueTypeString...) (Vector, Annotations) ===
 func funcSortByLabel(vals []parser.Value, args parser.Expressions, enh *EvalNodeHelper) (Vector, annotations.Annotations) {
-	// First, sort by the full label set. This ensures a consistent ordering in case sorting by the
-	// labels provided as arguments is not conclusive.
+	lbls := stringSliceFromArgs(args[1:])
 	slices.SortFunc(vals[0].(Vector), func(a, b Sample) int {
-		return labels.Compare(a.Metric, b.Metric)
-	})
-
-	labels := stringSliceFromArgs(args[1:])
-	// Next, sort by the labels provided as arguments.
-	slices.SortFunc(vals[0].(Vector), func(a, b Sample) int {
-		// Iterate over each given label.
-		for _, label := range labels {
+		for _, label := range lbls {
 			lv1 := a.Metric.Get(label)
 			lv2 := b.Metric.Get(label)
 
-			// If we encounter multiple samples with the same label values, the sorting which was
-			// performed in the first step will act as a "tie breaker".
 			if lv1 == lv2 {
 				continue
 			}
@@ -442,7 +432,8 @@ func funcSortByLabel(vals []parser.Value, args parser.Expressions, enh *EvalNode
 			return +1
 		}
 
-		return 0
+		// If all labels provided as arguments were equal, sort by the full label set. This ensures a consistent ordering.
+		return labels.Compare(a.Metric, b.Metric)
 	})
 
 	return vals[0].(Vector), nil
@@ -450,22 +441,12 @@ func funcSortByLabel(vals []parser.Value, args parser.Expressions, enh *EvalNode
 
 // === sort_by_label_desc(vector parser.ValueTypeVector, label parser.ValueTypeString...) (Vector, Annotations) ===
 func funcSortByLabelDesc(vals []parser.Value, args parser.Expressions, enh *EvalNodeHelper) (Vector, annotations.Annotations) {
-	// First, sort by the full label set. This ensures a consistent ordering in case sorting by the
-	// labels provided as arguments is not conclusive.
+	lbls := stringSliceFromArgs(args[1:])
 	slices.SortFunc(vals[0].(Vector), func(a, b Sample) int {
-		return labels.Compare(b.Metric, a.Metric)
-	})
-
-	labels := stringSliceFromArgs(args[1:])
-	// Next, sort by the labels provided as arguments.
-	slices.SortFunc(vals[0].(Vector), func(a, b Sample) int {
-		// Iterate over each given label.
-		for _, label := range labels {
+		for _, label := range lbls {
 			lv1 := a.Metric.Get(label)
 			lv2 := b.Metric.Get(label)
 
-			// If we encounter multiple samples with the same label values, the sorting which was
-			// performed in the first step will act as a "tie breaker".
 			if lv1 == lv2 {
 				continue
 			}
@@ -477,7 +458,8 @@ func funcSortByLabelDesc(vals []parser.Value, args parser.Expressions, enh *Eval
 			return -1
 		}
 
-		return 0
+		// If all labels provided as arguments were equal, sort by the full label set. This ensures a consistent ordering.
+		return -labels.Compare(a.Metric, b.Metric)
 	})
 
 	return vals[0].(Vector), nil