From 05aee52517084a8b1493af20b4721cc9f3a86b5f Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Fri, 10 Oct 2025 23:42:12 -0400
Subject: [PATCH 01/11] add disableTimestamp option in serializer with unit
 tests

---
 .../Internal/PrometheusSerializerExt.cs       |  22 ++-
 .../PrometheusSerializerTests.cs              | 146 ++++++++++--------
 2 files changed, 98 insertions(+), 70 deletions(-)

diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
index 70d67f468bf..a952a08816d 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
@@ -22,7 +22,7 @@ public static bool CanWriteMetric(Metric metric)
         return true;
     }
 
-    public static int WriteMetric(byte[] buffer, int cursor, Metric metric, PrometheusMetric prometheusMetric, bool openMetricsRequested = false)
+    public static int WriteMetric(byte[] buffer, int cursor, Metric metric, PrometheusMetric prometheusMetric, bool openMetricsRequested = false, bool disableTimestamp = false)
     {
         cursor = WriteTypeMetadata(buffer, cursor, prometheusMetric, openMetricsRequested);
         cursor = WriteUnitMetadata(buffer, cursor, prometheusMetric, openMetricsRequested);
@@ -68,7 +68,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
 
                 buffer[cursor++] = unchecked((byte)' ');
 
-                cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                if (!disableTimestamp)
+                {
+                    cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                }
 
                 buffer[cursor++] = ASCII_LINEFEED;
             }
@@ -105,7 +108,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                     cursor = WriteLong(buffer, cursor, totalCount);
                     buffer[cursor++] = unchecked((byte)' ');
 
-                    cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                    if (!disableTimestamp)
+                    {
+                        cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                    }
 
                     buffer[cursor++] = ASCII_LINEFEED;
                 }
@@ -120,7 +126,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                 cursor = WriteDouble(buffer, cursor, metricPoint.GetHistogramSum());
                 buffer[cursor++] = unchecked((byte)' ');
 
-                cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                if (!disableTimestamp)
+                {
+                    cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                }
 
                 buffer[cursor++] = ASCII_LINEFEED;
 
@@ -134,7 +143,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                 cursor = WriteLong(buffer, cursor, metricPoint.GetHistogramCount());
                 buffer[cursor++] = unchecked((byte)' ');
 
-                cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                if (!disableTimestamp)
+                {
+                    cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
+                }
 
                 buffer[cursor++] = ASCII_LINEFEED;
             }
diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
index 2864fe59b5c..43c97126cc5 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
@@ -11,8 +11,10 @@ namespace OpenTelemetry.Exporter.Prometheus.Tests;
 
 public sealed class PrometheusSerializerTests
 {
-    [Fact]
-    public void GaugeZeroDimension()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void GaugeZeroDimension(bool disableTimestamp)
     {
         var buffer = new byte[85000];
         var metrics = new List<Metric>();
@@ -27,13 +29,15 @@ public void GaugeZeroDimension()
 
         provider.ForceFlush();
 
-        var cursor = WriteMetric(buffer, 0, metrics[0]);
-        Assert.Matches(
+        var cursor = WriteMetric(buffer, 0, metrics[0], false, disableTimestamp);
+        var timestampPart = disableTimestamp ? string.Empty : "\\d+";
+        var output = Encoding.UTF8.GetString(buffer, 0, cursor);
+        var expected =
             ("^"
                 + "# TYPE test_gauge gauge\n"
-                + $"test_gauge{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 123 \\d+\n"
-                + "$").Replace('\'', '"'),
-            Encoding.UTF8.GetString(buffer, 0, cursor));
+                + $"test_gauge{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 123 {timestampPart}\n"
+                + "$").Replace('\'', '"');
+        Assert.Matches(expected, output);
     }
 
     [Fact]
@@ -255,8 +259,10 @@ public void SumNonMonotonicDouble()
             Encoding.UTF8.GetString(buffer, 0, cursor));
     }
 
-    [Fact]
-    public void HistogramZeroDimension()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void HistogramZeroDimension(bool disableTimestamp)
     {
         var buffer = new byte[85000];
         var metrics = new List<Metric>();
@@ -273,30 +279,32 @@ public void HistogramZeroDimension()
 
         provider.ForceFlush();
 
-        var cursor = WriteMetric(buffer, 0, metrics[0]);
-        Assert.Matches(
+        var cursor = WriteMetric(buffer, 0, metrics[0], false, disableTimestamp);
+        var timestampPart = disableTimestamp ? string.Empty : "\\d+";
+        var output = Encoding.UTF8.GetString(buffer, 0, cursor);
+        var expected =
             ("^"
                 + "# TYPE test_histogram histogram\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='0'}} 0 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5'}} 0 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10'}} 0 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='25'}} 1 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='50'}} 1 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='75'}} 1 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='100'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='250'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='500'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='750'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='1000'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='2500'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5000'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='7500'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10000'}} 2 \\d+\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='\\+Inf'}} 2 \\d+\n"
-                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 118 \\d+\n"
-                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 2 \\d+\n"
-                + "$").Replace('\'', '"'),
-            Encoding.UTF8.GetString(buffer, 0, cursor));
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='0'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='25'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='50'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='75'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='100'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='250'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='750'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='1000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='2500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='7500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='\\+Inf'}} 2 {timestampPart}\n"
+                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 118 {timestampPart}\n"
+                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 2 {timestampPart}\n"
+                + "$").Replace('\'', '"');
+        Assert.Matches(expected, output);
     }
 
     [Fact]
@@ -499,8 +507,10 @@ public void ExponentialHistogramIsIgnoredForNow()
         Assert.False(PrometheusSerializer.CanWriteMetric(metrics[0]));
     }
 
-    [Fact]
-    public void SumWithOpenMetricsFormat()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void SumWithOpenMetricsFormat(bool disableTimestamp)
     {
         var buffer = new byte[85000];
         var metrics = new List<Metric>();
@@ -517,17 +527,21 @@ public void SumWithOpenMetricsFormat()
 
         provider.ForceFlush();
 
-        var cursor = WriteMetric(buffer, 0, metrics[0], true);
-        Assert.Matches(
+        var cursor = WriteMetric(buffer, 0, metrics[0], true, disableTimestamp);
+        var timestampPart = disableTimestamp ? string.Empty : "\\d+\\.\\d{3}";
+        var output = Encoding.UTF8.GetString(buffer, 0, cursor);
+        var expected =
             ("^"
-             + "# TYPE test_updown_counter gauge\n"
-             + $"test_updown_counter{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} -1 \\d+\\.\\d{{3}}\n"
-             + "$").Replace('\'', '"'),
-            Encoding.UTF8.GetString(buffer, 0, cursor));
+                + "# TYPE test_updown_counter gauge\n"
+                + $"test_updown_counter{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} -1 {timestampPart}\n"
+                + "$").Replace('\'', '"');
+        Assert.Matches(expected, output);
     }
 
-    [Fact]
-    public void HistogramOneDimensionWithOpenMetricsFormat()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void HistogramOneDimensionWithOpenMetricsFormat(bool disableTimestamp)
     {
         var buffer = new byte[85000];
         var metrics = new List<Metric>();
@@ -544,30 +558,32 @@ public void HistogramOneDimensionWithOpenMetricsFormat()
 
         provider.ForceFlush();
 
-        var cursor = WriteMetric(buffer, 0, metrics[0], true);
-        Assert.Matches(
+        var cursor = WriteMetric(buffer, 0, metrics[0], true, disableTimestamp);
+        var timestampPart = disableTimestamp ? string.Empty : "\\d+\\.\\d{3}";
+        var output = Encoding.UTF8.GetString(buffer, 0, cursor);
+        var expected =
             ("^"
                 + "# TYPE test_histogram histogram\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='0'}} 0 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5'}} 0 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10'}} 0 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='25'}} 1 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='50'}} 1 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='75'}} 1 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='100'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='250'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='500'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='750'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='1000'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='2500'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5000'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='7500'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10000'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='\\+Inf'}} 2 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 118 \\d+\\.\\d{{3}}\n"
-                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 2 \\d+\\.\\d{{3}}\n"
-                + "$").Replace('\'', '"'),
-            Encoding.UTF8.GetString(buffer, 0, cursor));
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='0'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10'}} 0 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='25'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='50'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='75'}} 1 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='100'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='250'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='750'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='1000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='2500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='7500'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10000'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='\\+Inf'}} 2 {timestampPart}\n"
+                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 118 {timestampPart}\n"
+                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 2 {timestampPart}\n"
+                + "$").Replace('\'', '"');
+        Assert.Matches(expected, output);
     }
 
     [Fact]
@@ -653,8 +669,8 @@ public void HistogramOneDimensionWithScopeVersion()
             Encoding.UTF8.GetString(buffer, 0, cursor));
     }
 
-    private static int WriteMetric(byte[] buffer, int cursor, Metric metric, bool useOpenMetrics = false)
+    private static int WriteMetric(byte[] buffer, int cursor, Metric metric, bool useOpenMetrics = false, bool disableTimestamp = false)
     {
-        return PrometheusSerializer.WriteMetric(buffer, cursor, metric, PrometheusMetric.Create(metric, false), useOpenMetrics);
+        return PrometheusSerializer.WriteMetric(buffer, cursor, metric, PrometheusMetric.Create(metric, false), useOpenMetrics, disableTimestamp);
     }
 }

From 896fd2c9993211dbd1bc445de218a749f8b721b0 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Fri, 10 Oct 2025 23:44:07 -0400
Subject: [PATCH 02/11] add disableTimestamp option for prometheus httpListener
 and AspNetCore

---
 .../.publicApi/PublicAPI.Unshipped.txt                   | 2 ++
 .../PrometheusAspNetCoreOptions.cs                       | 9 +++++++++
 .../.publicApi/PublicAPI.Unshipped.txt                   | 2 ++
 .../Internal/PrometheusCollectionManager.cs              | 3 ++-
 .../Internal/PrometheusExporter.cs                       | 3 +++
 .../Internal/PrometheusExporterOptions.cs                | 5 +++++
 ...ometheusHttpListenerMeterProviderBuilderExtensions.cs | 1 +
 .../PrometheusHttpListenerOptions.cs                     | 5 +++++
 8 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt
index 92eaa1e4111..043f62a17a9 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt
@@ -1,6 +1,8 @@
 Microsoft.AspNetCore.Builder.PrometheusExporterApplicationBuilderExtensions
 Microsoft.AspNetCore.Builder.PrometheusExporterEndpointRouteBuilderExtensions
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions
+OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTimestamp.get -> bool
+OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTimestamp.set -> void
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTotalNameSuffixForCounters.get -> bool
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTotalNameSuffixForCounters.set -> void
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.PrometheusAspNetCoreOptions() -> void
diff --git a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs
index ed8186ec88d..171eb465692 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs
@@ -38,5 +38,14 @@ public int ScrapeResponseCacheDurationMilliseconds
         set => this.ExporterOptions.ScrapeResponseCacheDurationMilliseconds = value;
     }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether timestamps should be disabled. Default value: <see langword="false"/>.
+    /// </summary>
+    public bool DisableTimestamp
+    {
+        get => this.ExporterOptions.DisableTimestamp;
+        set => this.ExporterOptions.DisableTimestamp = value;
+    }
+
     internal PrometheusExporterOptions ExporterOptions { get; } = new();
 }
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt
index 6caa1a77cb1..043ec1010ae 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt
@@ -1,4 +1,6 @@
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions
+OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTimestamp.get -> bool
+OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTimestamp.set -> void
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTotalNameSuffixForCounters.get -> bool
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTotalNameSuffixForCounters.set -> void
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.UriPrefixes.get -> System.Collections.Generic.IReadOnlyCollection<string!>!
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusCollectionManager.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusCollectionManager.cs
index ce4c5384485..8e50d1c1da9 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusCollectionManager.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusCollectionManager.cs
@@ -275,7 +275,8 @@ private ExportResult OnCollect(in Batch<Metric> metrics)
                             cursor,
                             metric,
                             this.GetPrometheusMetric(metric),
-                            this.exporter.OpenMetricsRequested);
+                            this.exporter.OpenMetricsRequested,
+                            this.exporter.DisableTimestamp);
 
                         break;
                     }
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporter.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporter.cs
index 2d9ea4c27d1..f1cca1d3c19 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporter.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporter.cs
@@ -27,6 +27,7 @@ public PrometheusExporter(PrometheusExporterOptions options)
 
         this.ScrapeResponseCacheDurationMilliseconds = options.ScrapeResponseCacheDurationMilliseconds;
         this.DisableTotalNameSuffixForCounters = options.DisableTotalNameSuffixForCounters;
+        this.DisableTimestamp = options.DisableTimestamp;
 
         this.CollectionManager = new PrometheusCollectionManager(this);
     }
@@ -50,6 +51,8 @@ public PrometheusExporter(PrometheusExporterOptions options)
 
     internal bool OpenMetricsRequested { get; set; }
 
+    internal bool DisableTimestamp { get; set; }
+
     internal Resource Resource => this.resource ??= this.ParentProvider.GetResource();
 
     /// <inheritdoc/>
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporterOptions.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporterOptions.cs
index ec14b88b182..9f2f03bb5c9 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporterOptions.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporterOptions.cs
@@ -33,4 +33,9 @@ public int ScrapeResponseCacheDurationMilliseconds
     /// Gets or sets a value indicating whether addition of _total suffix for counter metric names is disabled. Default value: <see langword="false"/>.
     /// </summary>
     public bool DisableTotalNameSuffixForCounters { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether timestamps should be disabled. Default value: <see langword="false"/>.
+    /// </summary>
+    public bool DisableTimestamp { get; set; }
 }
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs
index 94eea0f5742..508d4358e58 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs
@@ -69,6 +69,7 @@ private static BaseExportingMetricReader BuildPrometheusHttpListenerMetricReader
         {
             ScrapeResponseCacheDurationMilliseconds = 0,
             DisableTotalNameSuffixForCounters = options.DisableTotalNameSuffixForCounters,
+            DisableTimestamp = options.DisableTimestamp,
         });
 
         var reader = new BaseExportingMetricReader(exporter)
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs
index 8909a3bd82e..581f42f63a6 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs
@@ -24,6 +24,11 @@ public class PrometheusHttpListenerOptions
     /// </summary>
     public bool DisableTotalNameSuffixForCounters { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether timestamps should be disabled. Default value: <see langword="false"/>.
+    /// </summary>
+    public bool DisableTimestamp { get; set; }
+
     /// <summary>
     /// Gets or sets the URI (Uniform Resource Identifier) prefixes to use for the http listener.
     /// Default value: <c>["http://localhost:9464/"]</c>.

From 8d443d86f598d68d05303284af93a96ee40c9355 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Sat, 11 Oct 2025 22:48:57 -0400
Subject: [PATCH 03/11] add disableTimestamp flag tests for Prometheus
 httpListener and AspNetCore

---
 .../PrometheusExporterMiddlewareTests.cs      | 31 +++++++++++++------
 .../PrometheusHttpListenerTests.cs            | 29 ++++++++++-------
 2 files changed, 40 insertions(+), 20 deletions(-)

diff --git a/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs b/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
index 98d503e8e92..113edace584 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
@@ -51,13 +51,19 @@ public Task PrometheusExporterMiddlewareIntegration_OptionsFallback()
             services => services.Configure<PrometheusAspNetCoreOptions>(o => o.ScrapeEndpointPath = null));
     }
 
-    [Fact]
-    public Task PrometheusExporterMiddlewareIntegration_OptionsViaAddPrometheusExporter()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public Task PrometheusExporterMiddlewareIntegration_OptionsViaAddPrometheusExporter(bool disableTimestamp)
     {
         return RunPrometheusExporterMiddlewareIntegrationTest(
             "/metrics_from_AddPrometheusExporter",
             app => app.UseOpenTelemetryPrometheusScrapingEndpoint(),
-            configureOptions: o => o.ScrapeEndpointPath = "/metrics_from_AddPrometheusExporter");
+            configureOptions: o =>
+            {
+                o.ScrapeEndpointPath = "/metrics_from_AddPrometheusExporter";
+                o.DisableTimestamp = disableTimestamp;
+            });
     }
 
     [Fact]
@@ -407,7 +413,9 @@ private static async Task RunPrometheusExporterMiddlewareIntegrationTest(
 
         if (!skipMetrics)
         {
-            await VerifyAsync(beginTimestamp, endTimestamp, response, requestOpenMetrics, meterTags);
+            var options = new PrometheusAspNetCoreOptions();
+            configureOptions?.Invoke(options);
+            await VerifyAsync(beginTimestamp, endTimestamp, response, requestOpenMetrics, meterTags, options.DisableTimestamp);
         }
         else
         {
@@ -419,7 +427,7 @@ private static async Task RunPrometheusExporterMiddlewareIntegrationTest(
         await host.StopAsync();
     }
 
-    private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, HttpResponseMessage response, bool requestOpenMetrics, KeyValuePair<string, object?>[]? meterTags)
+    private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, HttpResponseMessage response, bool requestOpenMetrics, KeyValuePair<string, object?>[]? meterTags, bool disableTimestamp = false)
     {
         Assert.Equal(HttpStatusCode.OK, response.StatusCode);
         Assert.True(response.Content.Headers.Contains("Last-Modified"));
@@ -439,6 +447,8 @@ private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, Ht
 
         string content = (await response.Content.ReadAsStringAsync()).ReplaceLineEndings();
 
+        var timestampPart = disableTimestamp ? string.Empty : "(\\d+)";
+        var timestampPartOpenMetrics = disableTimestamp ? string.Empty : "(\\d+\\.\\d{3})";
         string expected = requestOpenMetrics
             ? $$"""
                     # TYPE target info
@@ -449,14 +459,14 @@ private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, Ht
                     otel_scope_info{otel_scope_name="{{MeterName}}"} 1
                     # TYPE counter_double_bytes counter
                     # UNIT counter_double_bytes bytes
-                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 (\d+\.\d{3})
+                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 {{timestampPartOpenMetrics}}
                     # EOF
 
                     """.ReplaceLineEndings()
             : $$"""
                     # TYPE counter_double_bytes_total counter
                     # UNIT counter_double_bytes_total bytes
-                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 (\d+)
+                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 {{timestampPart}}
                     # EOF
 
                     """.ReplaceLineEndings();
@@ -465,9 +475,12 @@ private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, Ht
 
         Assert.True(matches.Count == 1, content);
 
-        var timestamp = long.Parse(matches[0].Groups[1].Value.Replace(".", string.Empty, StringComparison.Ordinal), CultureInfo.InvariantCulture);
+        if (!disableTimestamp)
+        {
+            var timestamp = long.Parse(matches[0].Groups[1].Value.Replace(".", string.Empty, StringComparison.Ordinal), CultureInfo.InvariantCulture);
 
-        Assert.True(beginTimestamp <= timestamp && timestamp <= endTimestamp, $"{beginTimestamp} {timestamp} {endTimestamp}");
+            Assert.True(beginTimestamp <= timestamp && timestamp <= endTimestamp, $"{beginTimestamp} {timestamp} {endTimestamp}");
+        }
     }
 
     private static Task<IHost> StartTestHostAsync(
diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
index 7ff58940692..6394fc8295a 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
@@ -61,10 +61,12 @@ public void UriPrefixesInvalid()
         });
     }
 
-    [Fact]
-    public async Task PrometheusExporterHttpServerIntegration()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task PrometheusExporterHttpServerIntegration(bool disableTimestamp)
     {
-        await RunPrometheusExporterHttpServerIntegrationTest();
+        await RunPrometheusExporterHttpServerIntegrationTest(disableTimestamp: disableTimestamp);
     }
 
     [Fact]
@@ -73,10 +75,12 @@ public async Task PrometheusExporterHttpServerIntegration_NoMetrics()
         await RunPrometheusExporterHttpServerIntegrationTest(skipMetrics: true);
     }
 
-    [Fact]
-    public async Task PrometheusExporterHttpServerIntegration_NoOpenMetrics()
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task PrometheusExporterHttpServerIntegration_NoOpenMetrics(bool disableTimestamp)
     {
-        await RunPrometheusExporterHttpServerIntegrationTest(acceptHeader: string.Empty);
+        await RunPrometheusExporterHttpServerIntegrationTest(acceptHeader: string.Empty, disableTimestamp: disableTimestamp);
     }
 
     [Fact]
@@ -220,7 +224,7 @@ private static void TestPrometheusHttpListenerUriPrefixOptions(string[] uriPrefi
             });
     }
 
-    private static MeterProvider BuildMeterProvider(Meter meter, IEnumerable<KeyValuePair<string, object>> attributes, out string address)
+    private static MeterProvider BuildMeterProvider(Meter meter, IEnumerable<KeyValuePair<string, object>> attributes, out string address, bool disableTimestamp = false)
     {
         Random random = new Random();
         int retryAttempts = 5;
@@ -242,6 +246,7 @@ private static MeterProvider BuildMeterProvider(Meter meter, IEnumerable<KeyValu
                     .AddPrometheusHttpListener(options =>
                     {
                         options.UriPrefixes = [generatedAddress];
+                        options.DisableTimestamp = disableTimestamp;
                     })
                     .Build();
 
@@ -258,13 +263,13 @@ private static MeterProvider BuildMeterProvider(Meter meter, IEnumerable<KeyValu
         return provider ?? throw new InvalidOperationException("HttpListener could not be started");
     }
 
-    private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetrics = false, string acceptHeader = "application/openmetrics-text", KeyValuePair<string, object?>[]? meterTags = null)
+    private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool skipMetrics = false, string acceptHeader = "application/openmetrics-text", KeyValuePair<string, object?>[]? meterTags = null, bool disableTimestamp = false)
     {
         var requestOpenMetrics = acceptHeader.StartsWith("application/openmetrics-text", StringComparison.Ordinal);
 
         using var meter = new Meter(MeterName, MeterVersion, meterTags);
 
-        var provider = BuildMeterProvider(meter, [], out var address);
+        var provider = BuildMeterProvider(meter, [], out var address, disableTimestamp);
 
         var counterTags = new KeyValuePair<string, object?>[]
         {
@@ -308,6 +313,8 @@ private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool sk
 
             var content = await response.Content.ReadAsStringAsync();
 
+            var timestampPart = disableTimestamp ? string.Empty : "(\\d+)";
+            var timestampPartOpenMetrics = disableTimestamp ? string.Empty : "(\\d+\\.\\d{3})";
             var expected = requestOpenMetrics
                 ? "# TYPE target info\n"
                   + "# HELP target Target metadata\n"
@@ -317,11 +324,11 @@ private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool sk
                   + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
                   + "# TYPE counter_double_bytes counter\n"
                   + "# UNIT counter_double_bytes bytes\n"
-                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 (\\d+\\.\\d{{3}})\n"
+                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 {timestampPartOpenMetrics}\n"
                   + "# EOF\n"
                 : "# TYPE counter_double_bytes_total counter\n"
                   + "# UNIT counter_double_bytes_total bytes\n"
-                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 (\\d+)\n"
+                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 {timestampPart}\n"
                   + "# EOF\n";
 
             Assert.Matches(("^" + expected + "$").Replace('\'', '"'), content);

From b4a7d190664d47103b5306b864603d87d59502e2 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Sun, 12 Oct 2025 22:20:57 -0400
Subject: [PATCH 04/11] added changelog entries

---
 src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md  | 3 +++
 .../CHANGELOG.md                                               | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
index 13d43338279..16175f0ce04 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
+++ b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
@@ -7,6 +7,9 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+* Added the possibility to disable timestamps via the `PrometheusAspNetCoreOptions`.
+  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
+
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
index c293fec214f..a6bd5ca03bf 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
@@ -7,6 +7,9 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+* Added the possibility to disable timestamps via the `PrometheusHttpListenerOptions`.
+  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
+
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and

From 50236d5d7368627333a2b232c4d2d0bf6ad82ed1 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Tue, 14 Oct 2025 11:53:43 -0400
Subject: [PATCH 05/11] remove space if no timestamp is used

---
 .../CHANGELOG.md                                         | 6 +++---
 .../CHANGELOG.md                                         | 6 +++---
 .../Internal/PrometheusSerializerExt.cs                  | 9 ++++-----
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
index 16175f0ce04..061bea516e0 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
+++ b/src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md
@@ -7,15 +7,15 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
-* Added the possibility to disable timestamps via the `PrometheusAspNetCoreOptions`.
-  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
-
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and
   `Microsoft.Extensions.Logging.Configuration` NuGet packages.
   ([#6327](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6327))
 
+* Added the possibility to disable timestamps via the `PrometheusAspNetCoreOptions`.
+  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
+
 ## 1.13.1-beta.1
 
 Released 2025-Oct-10
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
index a6bd5ca03bf..34670fa41ad 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md
@@ -7,15 +7,15 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
-* Added the possibility to disable timestamps via the `PrometheusHttpListenerOptions`.
-  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
-
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and
   `Microsoft.Extensions.Logging.Configuration` NuGet packages.
   ([#6327](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6327))
 
+* Added the possibility to disable timestamps via the `PrometheusHttpListenerOptions`.
+  ([#6600](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6600))
+
 ## 1.13.1-beta.1
 
 Released 2025-Oct-10
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
index a952a08816d..6579008933a 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
@@ -66,10 +66,9 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                     }
                 }
 
-                buffer[cursor++] = unchecked((byte)' ');
-
                 if (!disableTimestamp)
                 {
+                    buffer[cursor++] = unchecked((byte)' ');
                     cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
                 }
 
@@ -106,10 +105,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                     cursor = WriteAsciiStringNoEscape(buffer, cursor, "\"} ");
 
                     cursor = WriteLong(buffer, cursor, totalCount);
-                    buffer[cursor++] = unchecked((byte)' ');
 
                     if (!disableTimestamp)
                     {
+                        buffer[cursor++] = unchecked((byte)' ');
                         cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
                     }
 
@@ -124,10 +123,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                 buffer[cursor++] = unchecked((byte)' ');
 
                 cursor = WriteDouble(buffer, cursor, metricPoint.GetHistogramSum());
-                buffer[cursor++] = unchecked((byte)' ');
 
                 if (!disableTimestamp)
                 {
+                    buffer[cursor++] = unchecked((byte)' ');
                     cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
                 }
 
@@ -141,10 +140,10 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                 buffer[cursor++] = unchecked((byte)' ');
 
                 cursor = WriteLong(buffer, cursor, metricPoint.GetHistogramCount());
-                buffer[cursor++] = unchecked((byte)' ');
 
                 if (!disableTimestamp)
                 {
+                    buffer[cursor++] = unchecked((byte)' ');
                     cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
                 }
 

From 0cd9dd7345e4e75ceab77086cbea38390fd8b44d Mon Sep 17 00:00:00 2001
From: Hannah Haering <157852144+hannahhaering@users.noreply.github.com>
Date: Tue, 14 Oct 2025 11:58:36 -0400
Subject: [PATCH 06/11] Update
 test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Piotr Kiełkowicz <pkiekowicz@splunk.com>
---
 .../PrometheusSerializerTests.cs              | 36 +++++++++----------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
index 43c97126cc5..51af8b7018f 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
@@ -285,24 +285,24 @@ public void HistogramZeroDimension(bool disableTimestamp)
         var expected =
             ("^"
                 + "# TYPE test_histogram histogram\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='0'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='25'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='50'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='75'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='100'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='250'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='750'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='1000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='2500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='7500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='\\+Inf'}} 2 {timestampPart}\n"
-                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 118 {timestampPart}\n"
-                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='0'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='25'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='50'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='75'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='100'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='250'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='750'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='1000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='2500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='5000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='7500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='10000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',le='\\+Inf'}} 2{timestampPart}\n"
+                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 118{timestampPart}\n"
+                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 2{timestampPart}\n"
                 + "$").Replace('\'', '"');
         Assert.Matches(expected, output);
     }

From 5ec336d80cc30a028401b534fbb34458b49b90a0 Mon Sep 17 00:00:00 2001
From: Hannah Haering <157852144+hannahhaering@users.noreply.github.com>
Date: Tue, 14 Oct 2025 11:58:54 -0400
Subject: [PATCH 07/11] Update
 src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Piotr Kiełkowicz <pkiekowicz@splunk.com>
---
 .../Internal/PrometheusSerializerExt.cs                         | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
index 6579008933a..613f7acf4d7 100644
--- a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
+++ b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
@@ -22,7 +22,7 @@ public static bool CanWriteMetric(Metric metric)
         return true;
     }
 
-    public static int WriteMetric(byte[] buffer, int cursor, Metric metric, PrometheusMetric prometheusMetric, bool openMetricsRequested = false, bool disableTimestamp = false)
+    public static int WriteMetric(byte[] buffer, int cursor, Metric metric, PrometheusMetric prometheusMetric, bool openMetricsRequested, bool disableTimestamp)
     {
         cursor = WriteTypeMetadata(buffer, cursor, prometheusMetric, openMetricsRequested);
         cursor = WriteUnitMetadata(buffer, cursor, prometheusMetric, openMetricsRequested);

From b311eee0b55601f72d3e61e422e1496192e89f52 Mon Sep 17 00:00:00 2001
From: Hannah Haering <157852144+hannahhaering@users.noreply.github.com>
Date: Tue, 14 Oct 2025 11:59:05 -0400
Subject: [PATCH 08/11] Update
 test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Piotr Kiełkowicz <pkiekowicz@splunk.com>
---
 .../PrometheusSerializerTests.cs                                | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
index 51af8b7018f..6d7e8c97f9e 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
@@ -280,7 +280,7 @@ public void HistogramZeroDimension(bool disableTimestamp)
         provider.ForceFlush();
 
         var cursor = WriteMetric(buffer, 0, metrics[0], false, disableTimestamp);
-        var timestampPart = disableTimestamp ? string.Empty : "\\d+";
+        var timestampPart = disableTimestamp ? string.Empty : " \\d+";
         var output = Encoding.UTF8.GetString(buffer, 0, cursor);
         var expected =
             ("^"

From f005de3f534cb908578cad34d840667807951e88 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Tue, 14 Oct 2025 13:21:27 -0400
Subject: [PATCH 09/11] fix method call

---
 test/Benchmarks/Exporter/PrometheusSerializerBenchmarks.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/Benchmarks/Exporter/PrometheusSerializerBenchmarks.cs b/test/Benchmarks/Exporter/PrometheusSerializerBenchmarks.cs
index 47d04dd0d10..30b029625ab 100644
--- a/test/Benchmarks/Exporter/PrometheusSerializerBenchmarks.cs
+++ b/test/Benchmarks/Exporter/PrometheusSerializerBenchmarks.cs
@@ -59,7 +59,7 @@ public void WriteMetric()
             int cursor = 0;
             foreach (var metric in this.metrics)
             {
-                cursor = PrometheusSerializer.WriteMetric(this.buffer, cursor, metric, this.GetPrometheusMetric(metric));
+                cursor = PrometheusSerializer.WriteMetric(this.buffer, cursor, metric, this.GetPrometheusMetric(metric), openMetricsRequested: false, disableTimestamp: false);
             }
         }
     }

From 5fdfebba7424737892415cdcb215e7115c90e5b0 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Tue, 14 Oct 2025 13:32:34 -0400
Subject: [PATCH 10/11] fix tests

---
 .../PrometheusExporterMiddlewareTests.cs      |  8 ++--
 .../PrometheusSerializerTests.cs              | 46 +++++++++----------
 2 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs b/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
index 113edace584..c0ae96f5770 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs
@@ -447,8 +447,8 @@ private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, Ht
 
         string content = (await response.Content.ReadAsStringAsync()).ReplaceLineEndings();
 
-        var timestampPart = disableTimestamp ? string.Empty : "(\\d+)";
-        var timestampPartOpenMetrics = disableTimestamp ? string.Empty : "(\\d+\\.\\d{3})";
+        var timestampPart = disableTimestamp ? string.Empty : " (\\d+)";
+        var timestampPartOpenMetrics = disableTimestamp ? string.Empty : " (\\d+\\.\\d{3})";
         string expected = requestOpenMetrics
             ? $$"""
                     # TYPE target info
@@ -459,14 +459,14 @@ private static async Task VerifyAsync(long beginTimestamp, long endTimestamp, Ht
                     otel_scope_info{otel_scope_name="{{MeterName}}"} 1
                     # TYPE counter_double_bytes counter
                     # UNIT counter_double_bytes bytes
-                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 {{timestampPartOpenMetrics}}
+                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17{{timestampPartOpenMetrics}}
                     # EOF
 
                     """.ReplaceLineEndings()
             : $$"""
                     # TYPE counter_double_bytes_total counter
                     # UNIT counter_double_bytes_total bytes
-                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17 {{timestampPart}}
+                    counter_double_bytes_total{otel_scope_name="{{MeterName}}",otel_scope_version="{{MeterVersion}}",{{additionalTags}}key1="value1",key2="value2"} 101.17{{timestampPart}}
                     # EOF
 
                     """.ReplaceLineEndings();
diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
index 6d7e8c97f9e..aa060cf2545 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusSerializerTests.cs
@@ -30,12 +30,12 @@ public void GaugeZeroDimension(bool disableTimestamp)
         provider.ForceFlush();
 
         var cursor = WriteMetric(buffer, 0, metrics[0], false, disableTimestamp);
-        var timestampPart = disableTimestamp ? string.Empty : "\\d+";
+        var timestampPart = disableTimestamp ? string.Empty : " \\d+";
         var output = Encoding.UTF8.GetString(buffer, 0, cursor);
         var expected =
             ("^"
                 + "# TYPE test_gauge gauge\n"
-                + $"test_gauge{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 123 {timestampPart}\n"
+                + $"test_gauge{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} 123{timestampPart}\n"
                 + "$").Replace('\'', '"');
         Assert.Matches(expected, output);
     }
@@ -528,12 +528,12 @@ public void SumWithOpenMetricsFormat(bool disableTimestamp)
         provider.ForceFlush();
 
         var cursor = WriteMetric(buffer, 0, metrics[0], true, disableTimestamp);
-        var timestampPart = disableTimestamp ? string.Empty : "\\d+\\.\\d{3}";
+        var timestampPart = disableTimestamp ? string.Empty : " \\d+\\.\\d{3}";
         var output = Encoding.UTF8.GetString(buffer, 0, cursor);
         var expected =
             ("^"
                 + "# TYPE test_updown_counter gauge\n"
-                + $"test_updown_counter{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} -1 {timestampPart}\n"
+                + $"test_updown_counter{{otel_scope_name='{Utils.GetCurrentMethodName()}'}} -1{timestampPart}\n"
                 + "$").Replace('\'', '"');
         Assert.Matches(expected, output);
     }
@@ -559,29 +559,29 @@ public void HistogramOneDimensionWithOpenMetricsFormat(bool disableTimestamp)
         provider.ForceFlush();
 
         var cursor = WriteMetric(buffer, 0, metrics[0], true, disableTimestamp);
-        var timestampPart = disableTimestamp ? string.Empty : "\\d+\\.\\d{3}";
+        var timestampPart = disableTimestamp ? string.Empty : " \\d+\\.\\d{3}";
         var output = Encoding.UTF8.GetString(buffer, 0, cursor);
         var expected =
             ("^"
                 + "# TYPE test_histogram histogram\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='0'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10'}} 0 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='25'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='50'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='75'}} 1 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='100'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='250'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='750'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='1000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='2500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='7500'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10000'}} 2 {timestampPart}\n"
-                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='\\+Inf'}} 2 {timestampPart}\n"
-                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 118 {timestampPart}\n"
-                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 2 {timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='0'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10'}} 0{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='25'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='50'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='75'}} 1{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='100'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='250'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='750'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='1000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='2500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='5000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='7500'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='10000'}} 2{timestampPart}\n"
+                + $"test_histogram_bucket{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1',le='\\+Inf'}} 2{timestampPart}\n"
+                + $"test_histogram_sum{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 118{timestampPart}\n"
+                + $"test_histogram_count{{otel_scope_name='{Utils.GetCurrentMethodName()}',x='1'}} 2{timestampPart}\n"
                 + "$").Replace('\'', '"');
         Assert.Matches(expected, output);
     }

From abda976f7bd6472d15f5742a6dd5a04b7fd44883 Mon Sep 17 00:00:00 2001
From: hannahhaering <hannah.haering96@gmail.com>
Date: Tue, 14 Oct 2025 13:41:21 -0400
Subject: [PATCH 11/11] fix tests 2

---
 .../PrometheusHttpListenerTests.cs                        | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
index 6394fc8295a..c584ecc64cc 100644
--- a/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
+++ b/test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs
@@ -313,8 +313,8 @@ private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool sk
 
             var content = await response.Content.ReadAsStringAsync();
 
-            var timestampPart = disableTimestamp ? string.Empty : "(\\d+)";
-            var timestampPartOpenMetrics = disableTimestamp ? string.Empty : "(\\d+\\.\\d{3})";
+            var timestampPart = disableTimestamp ? string.Empty : " (\\d+)";
+            var timestampPartOpenMetrics = disableTimestamp ? string.Empty : " (\\d+\\.\\d{3})";
             var expected = requestOpenMetrics
                 ? "# TYPE target info\n"
                   + "# HELP target Target metadata\n"
@@ -324,11 +324,11 @@ private static async Task RunPrometheusExporterHttpServerIntegrationTest(bool sk
                   + $"otel_scope_info{{otel_scope_name='{MeterName}'}} 1\n"
                   + "# TYPE counter_double_bytes counter\n"
                   + "# UNIT counter_double_bytes bytes\n"
-                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 {timestampPartOpenMetrics}\n"
+                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17{timestampPartOpenMetrics}\n"
                   + "# EOF\n"
                 : "# TYPE counter_double_bytes_total counter\n"
                   + "# UNIT counter_double_bytes_total bytes\n"
-                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17 {timestampPart}\n"
+                  + $"counter_double_bytes_total{{otel_scope_name='{MeterName}',otel_scope_version='{MeterVersion}',{additionalTags}key1='value1',key2='value2'}} 101.17{timestampPart}\n"
                   + "# EOF\n";
 
             Assert.Matches(("^" + expected + "$").Replace('\'', '"'), content);