From b5f196cf913b12d73f508a9d2f3b9a1bc22eaefc Mon Sep 17 00:00:00 2001
From: Diego Hurtado <5069942+ocelotl@users.noreply.github.com>
Date: Mon, 24 Aug 2026 08:59:47 -0500
Subject: [PATCH 1/2] fix(sdk): make instrumentation scope glob matching
 case-sensitive

_scope_name_matches_glob used fnmatch.fnmatch, which normalizes both the
scope name and the glob pattern through os.path.normcase. On Windows
normcase lower-cases its argument, so scope name matching was
case-insensitive there while staying case-sensitive on Linux. The same
configuration therefore disabled a different set of instrumentation
scopes depending on the host operating system.

The declarative configuration schema requires case-sensitive matching for
the tracer, meter and logger configurator name matchers. Use fnmatchcase
so the behavior no longer depends on the host platform, matching what
metrics/_internal/view.py and trace/_sampling_experimental/_rule_based.py
already do.

Fixes #5583.
---
 .../opentelemetry/sdk/util/instrumentation.py    |  7 +++++--
 opentelemetry-sdk/tests/metrics/test_metrics.py  | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py b/opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py
index 710bd81de49..dba64abad96 100644
--- a/opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py
+++ b/opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py
@@ -1,7 +1,7 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
-import fnmatch
 from collections.abc import Callable
+from fnmatch import fnmatchcase
 from json import dumps
 
 from typing_extensions import deprecated
@@ -166,6 +166,9 @@ def _scope_name_matches_glob(
     glob_pattern: str,
 ) -> _InstrumentationScopePredicateT:
     def inner(scope: InstrumentationScope) -> bool:
-        return fnmatch.fnmatch(scope.name, glob_pattern)
+        # Scope name matching is case-sensitive. fnmatchcase is used instead of
+        # fnmatch so it does not rely on the host platform's filename case
+        # sensitivity (normcase), which lower-cases both operands on Windows.
+        return fnmatchcase(scope.name, glob_pattern)
 
     return inner
diff --git a/opentelemetry-sdk/tests/metrics/test_metrics.py b/opentelemetry-sdk/tests/metrics/test_metrics.py
index d093873ee59..bfca6ed778f 100644
--- a/opentelemetry-sdk/tests/metrics/test_metrics.py
+++ b/opentelemetry-sdk/tests/metrics/test_metrics.py
@@ -814,6 +814,22 @@ def test_scope_name_matches_glob_no_match(self):
         predicate = _scope_name_matches_glob("no.match")
         self.assertFalse(predicate(InstrumentationScope("my.meter", "1.0")))
 
+    def test_scope_name_matches_glob_is_case_sensitive_on_every_platform(self):
+        # fnmatch normcases both operands, which lower-cases them on Windows.
+        # Scope name matching must stay case-sensitive everywhere.
+        exact = _scope_name_matches_glob("my.meter")
+        self.assertTrue(exact(InstrumentationScope("my.meter", "1.0")))
+        self.assertFalse(exact(InstrumentationScope("My.Meter", "1.0")))
+
+        wildcard = _scope_name_matches_glob("my.*")
+        self.assertTrue(wildcard(InstrumentationScope("my.meter", "1.0")))
+        self.assertFalse(wildcard(InstrumentationScope("MY.meter", "1.0")))
+
+    def test_scope_name_matches_glob_pattern_case_is_not_normalized(self):
+        predicate = _scope_name_matches_glob("MY.*")
+        self.assertTrue(predicate(InstrumentationScope("MY.meter", "1.0")))
+        self.assertFalse(predicate(InstrumentationScope("my.meter", "1.0")))
+
     @patch("opentelemetry.sdk.metrics._internal.SynchronousMeasurementConsumer")
     def test_disabled_meter_counter_skips_measurement(self, mock_sync_measurement_consumer):
         sync_consumer_instance = mock_sync_measurement_consumer()

From 4498bd16d51184bea90dcc9477a607d2e8fba596 Mon Sep 17 00:00:00 2001
From: Diego Hurtado <5069942+ocelotl@users.noreply.github.com>
Date: Mon, 24 Aug 2026 09:00:49 -0500
Subject: [PATCH 2/2] Add changelog fragment for PR 5584

---
 .changelog/5584.fixed | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 .changelog/5584.fixed

diff --git a/.changelog/5584.fixed b/.changelog/5584.fixed
new file mode 100644
index 00000000000..b3659d71411
--- /dev/null
+++ b/.changelog/5584.fixed
@@ -0,0 +1 @@
+`opentelemetry-sdk`: fix instrumentation scope name matching in the tracer, meter and logger configurators so it is case-sensitive on every platform instead of relying on `fnmatch`'s OS-dependent case handling