From 8e0e223dcc6117bbc6cc967bc5da3b6b23eda8b9 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 11:44:12 +0200
Subject: [PATCH 01/22] Add cardinality limit option to MeterProvider
 configuration(Default 2000)

---
 sdk/metric/config.go | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 203cd9d6508..14dc1aa0177 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -17,10 +17,11 @@ import (
 
 // config contains configuration options for a MeterProvider.
 type config struct {
-	res            *resource.Resource
-	readers        []Reader
-	views          []View
-	exemplarFilter exemplar.Filter
+	res              *resource.Resource
+	readers          []Reader
+	views            []View
+	exemplarFilter   exemplar.Filter
+	cardinalityLimit int
 }
 
 // readerSignals returns a force-flush and shutdown function for a
@@ -69,8 +70,9 @@ func unifyShutdown(funcs []func(context.Context) error) func(context.Context) er
 // newConfig returns a config configured with options.
 func newConfig(options []Option) config {
 	conf := config{
-		res:            resource.Default(),
-		exemplarFilter: exemplar.TraceBasedFilter,
+		res:              resource.Default(),
+		exemplarFilter:   exemplar.TraceBasedFilter,
+		cardinalityLimit: 2000, // Default cardinality limit.
 	}
 	for _, o := range meterProviderOptionsFromEnv() {
 		conf = o.apply(conf)
@@ -155,6 +157,20 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 	})
 }
 
+// WithCardinalityLimit sets the cardinality limit for the MeterProvider.
+//
+// The cardinality limit is the maximum number of unique label sets that can be
+// recorded for a given instrument. If the limit is exceeded, the SDK will
+// drop the data point.
+//
+// By default, the cardinality limit is set to 2000.
+func WithCardinalityLimit(limit int) Option {
+	return optionFunc(func(cfg config) config {
+		cfg.cardinalityLimit = limit
+		return cfg
+	})
+}
+
 func meterProviderOptionsFromEnv() []Option {
 	var opts []Option
 	// https://github.com/open-telemetry/opentelemetry-specification/blob/d4b241f451674e8f611bb589477680341006ad2b/specification/configuration/sdk-environment-variables.md#exemplar

From c5c4e84c7d99d25e7cc8d30c10614890ff4defbb Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 11:44:52 +0200
Subject: [PATCH 02/22] unit tests for `Cardinality Limit`

---
 sdk/metric/config_test.go | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index 307c3e598e0..f87dbac970a 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -306,6 +306,16 @@ func TestWithExemplarFilterOff(t *testing.T) {
 	}
 }
 
+func TestWithCardinalityLimit(t *testing.T) {
+	c := newConfig([]Option{WithCardinalityLimit(1000)})
+	assert.Equal(t, 1000, c.cardinalityLimit)
+}
+
+func TestWithDefaultCardinalityLimit(t *testing.T) {
+	c := newConfig([]Option{})
+	assert.Equal(t, 2000, c.cardinalityLimit)
+}
+
 func sample(parent context.Context) context.Context {
 	sc := trace.NewSpanContext(trace.SpanContextConfig{
 		TraceID:    trace.TraceID{0x01},

From f666cfcffdbca502e57798b07a036581abf9f78b Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 11:46:53 +0200
Subject: [PATCH 03/22] refactor test

---
 sdk/metric/config_test.go | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index f87dbac970a..ba05a7a043b 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -307,13 +307,29 @@ func TestWithExemplarFilterOff(t *testing.T) {
 }
 
 func TestWithCardinalityLimit(t *testing.T) {
-	c := newConfig([]Option{WithCardinalityLimit(1000)})
-	assert.Equal(t, 1000, c.cardinalityLimit)
-}
+	cases := []struct {
+		name             string
+		options          []Option
+		expectedLimit    int
+	}{
+		{
+			name:          "explicit cardinality limit",
+			options:       []Option{WithCardinalityLimit(1000)},
+			expectedLimit: 1000,
+		},
+		{
+			name:          "default cardinality limit",
+			options:       []Option{},
+			expectedLimit: 2000,
+		},
+	}
 
-func TestWithDefaultCardinalityLimit(t *testing.T) {
-	c := newConfig([]Option{})
-	assert.Equal(t, 2000, c.cardinalityLimit)
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			c := newConfig(tc.options)
+			assert.Equal(t, tc.expectedLimit, c.cardinalityLimit)
+		})
+	}
 }
 
 func sample(parent context.Context) context.Context {

From c9edcf995b0458fd79c69982ed96ff513c347172 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 11:52:22 +0200
Subject: [PATCH 04/22] fix format

---
 sdk/metric/config_test.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index ba05a7a043b..1235cbcb603 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -308,9 +308,9 @@ func TestWithExemplarFilterOff(t *testing.T) {
 
 func TestWithCardinalityLimit(t *testing.T) {
 	cases := []struct {
-		name             string
-		options          []Option
-		expectedLimit    int
+		name         string
+		options      []Option
+		expectedLimit int
 	}{
 		{
 			name:          "explicit cardinality limit",

From e76e74f05d80ac7f5e1a72388e227636c454a9e1 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 11:55:59 +0200
Subject: [PATCH 05/22] fix format

---
 sdk/metric/config_test.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index 1235cbcb603..6337093778c 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -308,8 +308,8 @@ func TestWithExemplarFilterOff(t *testing.T) {
 
 func TestWithCardinalityLimit(t *testing.T) {
 	cases := []struct {
-		name         string
-		options      []Option
+		name          string
+		options       []Option
 		expectedLimit int
 	}{
 		{

From c555a1f6d230a25d95523dd6700d8c6d3ef07e33 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:04:35 +0200
Subject: [PATCH 06/22] Changelog

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a1e084d5b9..cc6f3e4ee43 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `RPCGRPCResponseMetadata`
 - Add `ErrorType` attribute helper function to the `go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
 
+- Add `cardinalityLimit` Configuration Option. (#6976)
+
 ### Changed
 
 - Change `AssertEqual` in `go.opentelemetry.io/otel/log/logtest` to accept `TestingT` in order to support benchmarks and fuzz tests. (#6908)

From 790095849895cb49cfb6c184142a6e6c112f1b45 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:05:17 +0200
Subject: [PATCH 07/22] fix Pr number

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc6f3e4ee43..3b94a898a2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,7 +41,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `RPCGRPCResponseMetadata`
 - Add `ErrorType` attribute helper function to the `go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
 
-- Add `cardinalityLimit` Configuration Option. (#6976)
+- Add `cardinalityLimit` Configuration Option. (#6996)
 
 ### Changed
 

From ad08fcdd47a53a4fa99df5253687a05923ebf2b5 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:27:09 +0200
Subject: [PATCH 08/22] extract default CardinalityLimit to const

---
 sdk/metric/config.go      | 5 ++++-
 sdk/metric/config_test.go | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 14dc1aa0177..862ad1922f5 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -24,6 +24,9 @@ type config struct {
 	cardinalityLimit int
 }
 
+// default cardinality limit.
+const defaultCardinalityLimit = 2000
+
 // readerSignals returns a force-flush and shutdown function for a
 // MeterProvider to call in their respective options. All Readers c contains
 // will have their force-flush and shutdown methods unified into returned
@@ -72,7 +75,7 @@ func newConfig(options []Option) config {
 	conf := config{
 		res:              resource.Default(),
 		exemplarFilter:   exemplar.TraceBasedFilter,
-		cardinalityLimit: 2000, // Default cardinality limit.
+		cardinalityLimit: defaultCardinalityLimit,
 	}
 	for _, o := range meterProviderOptionsFromEnv() {
 		conf = o.apply(conf)
diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index 6337093778c..a297e2e9721 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -320,7 +320,7 @@ func TestWithCardinalityLimit(t *testing.T) {
 		{
 			name:          "default cardinality limit",
 			options:       []Option{},
-			expectedLimit: 2000,
+			expectedLimit: defaultCardinalityLimit,
 		},
 	}
 

From 5c9c26f4564f0e633ff521cf4de6106b74de3a7c Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:30:01 +0200
Subject: [PATCH 09/22] update description

---
 sdk/metric/config.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 862ad1922f5..727729d5a02 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -162,11 +162,11 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 
 // WithCardinalityLimit sets the cardinality limit for the MeterProvider.
 //
-// The cardinality limit is the maximum number of unique label sets that can be
-// recorded for a given instrument. If the limit is exceeded, the SDK will
-// drop the data point.
+// The cardinality limit is the hard limit on the number of metric streams
+// that can be collected for a single instrument.
 //
 // By default, the cardinality limit is set to 2000.
+// To disable the limit, set the value to 0 or a negative number.
 func WithCardinalityLimit(limit int) Option {
 	return optionFunc(func(cfg config) config {
 		cfg.cardinalityLimit = limit

From ff93247914960b68577b38357de326e3a2ccdb61 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:33:54 +0200
Subject: [PATCH 10/22] fix changelog

---
 CHANGELOG.md | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3b94a898a2d..aad55bb2b8b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,8 +40,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `RPCGRPCRequestMetadata`
   - `RPCGRPCResponseMetadata`
 - Add `ErrorType` attribute helper function to the `go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
-
-- Add `cardinalityLimit` Configuration Option. (#6996)
+- Add `WithCardinalityLimit` option to configure the `cardinalityLimit` used by `go.opentelemetry.io/otel/sdk/metric`. (#6996)
 
 ### Changed
 

From 0132081955cee7b7ae666f45fb8675ad1afdeb29 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:54:41 +0200
Subject: [PATCH 11/22] support the `OTEL_GO_X_CARDINALITY_LIMIT` env var

---
 sdk/metric/config.go      | 16 +++++++++++++++-
 sdk/metric/config_test.go | 32 ++++++++++++++++++++++++++++++--
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 727729d5a02..a9b275e0c95 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -7,6 +7,7 @@ import (
 	"context"
 	"errors"
 	"os"
+	"strconv"
 	"strings"
 	"sync"
 
@@ -75,7 +76,7 @@ func newConfig(options []Option) config {
 	conf := config{
 		res:              resource.Default(),
 		exemplarFilter:   exemplar.TraceBasedFilter,
-		cardinalityLimit: defaultCardinalityLimit,
+		cardinalityLimit: cardinalityLimitFromEnv(),
 	}
 	for _, o := range meterProviderOptionsFromEnv() {
 		conf = o.apply(conf)
@@ -189,3 +190,16 @@ func meterProviderOptionsFromEnv() []Option {
 	}
 	return opts
 }
+
+func cardinalityLimitFromEnv() int {
+	const cardinalityLimitKey = "OTEL_GO_X_CARDINALITY_LIMIT"
+	v := strings.TrimSpace(os.Getenv(cardinalityLimitKey))
+	if v == "" {
+		return defaultCardinalityLimit
+	}
+	n, err := strconv.Atoi(v)
+	if err != nil {
+		return defaultCardinalityLimit
+	}
+	return n
+}
diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index a297e2e9721..ed6a1d32e9a 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -6,6 +6,7 @@ package metric
 import (
 	"context"
 	"errors"
+	"os"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -307,18 +308,44 @@ func TestWithExemplarFilterOff(t *testing.T) {
 }
 
 func TestWithCardinalityLimit(t *testing.T) {
+	const envVar = "OTEL_GO_X_CARDINALITY_LIMIT"
+
+	originalEnv := os.Getenv(envVar)
+	defer t.Setenv(envVar, originalEnv)
+
 	cases := []struct {
 		name          string
+		envValue      string
 		options       []Option
 		expectedLimit int
 	}{
 		{
-			name:          "explicit cardinality limit",
+			name:          "only cardinality limit from option",
+			envValue:      "",
 			options:       []Option{WithCardinalityLimit(1000)},
 			expectedLimit: 1000,
 		},
 		{
-			name:          "default cardinality limit",
+			name:          "cardinality limit from option overrides env",
+			envValue:      "500",
+			options:       []Option{WithCardinalityLimit(1000)},
+			expectedLimit: 1000,
+		},
+		{
+			name:          "cardinality limit from env",
+			envValue:      "1234",
+			options:       []Option{},
+			expectedLimit: 1234,
+		},
+		{
+			name:          "invalid env value uses default",
+			envValue:      "not-a-number",
+			options:       []Option{},
+			expectedLimit: defaultCardinalityLimit,
+		},
+		{
+			name:          "empty env and no option uses default",
+			envValue:      "",
 			options:       []Option{},
 			expectedLimit: defaultCardinalityLimit,
 		},
@@ -326,6 +353,7 @@ func TestWithCardinalityLimit(t *testing.T) {
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
+			os.Setenv(envVar, tc.envValue)
 			c := newConfig(tc.options)
 			assert.Equal(t, tc.expectedLimit, c.cardinalityLimit)
 		})

From a583ea94324b44a18432ff15a470b7b97482652f Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:56:41 +0200
Subject: [PATCH 12/22] fix test

---
 sdk/metric/config_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index ed6a1d32e9a..900b1bbd127 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -353,7 +353,7 @@ func TestWithCardinalityLimit(t *testing.T) {
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
-			os.Setenv(envVar, tc.envValue)
+			t.Setenv(envVar, tc.envValue)
 			c := newConfig(tc.options)
 			assert.Equal(t, tc.expectedLimit, c.cardinalityLimit)
 		})

From 0ae2f4e75dafb35b685f13c0e4b771918faa4ed6 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 12:56:55 +0200
Subject: [PATCH 13/22] fix test

---
 sdk/metric/config_test.go | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index 900b1bbd127..b13d17a6972 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -6,7 +6,6 @@ package metric
 import (
 	"context"
 	"errors"
-	"os"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -310,9 +309,6 @@ func TestWithExemplarFilterOff(t *testing.T) {
 func TestWithCardinalityLimit(t *testing.T) {
 	const envVar = "OTEL_GO_X_CARDINALITY_LIMIT"
 
-	originalEnv := os.Getenv(envVar)
-	defer t.Setenv(envVar, originalEnv)
-
 	cases := []struct {
 		name          string
 		envValue      string

From c3ac6c41641aa777e2724d0bb5ab34a6f994509f Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 13:13:14 +0200
Subject: [PATCH 14/22] Update CHANGELOG.md
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Robert Pająk <pellared@hotmail.com>
---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 680bb2b9c3a..d94b1fa67ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,7 +41,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `RPCGRPCResponseMetadata`
 - Add `ErrorType` attribute helper function to the `go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
 - Add `WithAllowKeyDuplication` in `go.opentelemetry.io/otel/sdk/log` which can be used to disable deduplication for log records. (#6968)
-- Add `WithCardinalityLimit` option to configure the `cardinalityLimit` used by `go.opentelemetry.io/otel/sdk/metric`. (#6996)
+- Add `WithCardinalityLimit` option to configure the cardinality limit in `go.opentelemetry.io/otel/sdk/metric`. (#6996)
 
 ### Changed
 

From 0650c7044fdb15bb090cd4ae844c5bb34f15443e Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 13:15:33 +0200
Subject: [PATCH 15/22] remove comment

---
 sdk/metric/config.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index a9b275e0c95..d3ee01cc8fa 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -25,7 +25,6 @@ type config struct {
 	cardinalityLimit int
 }
 
-// default cardinality limit.
 const defaultCardinalityLimit = 2000
 
 // readerSignals returns a force-flush and shutdown function for a

From 3f33729637c440c3e6ca0570103d4da2e915fd06 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 13:16:35 +0200
Subject: [PATCH 16/22] inline envvar in test

---
 sdk/metric/config_test.go | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/sdk/metric/config_test.go b/sdk/metric/config_test.go
index b13d17a6972..b3d728d29fc 100644
--- a/sdk/metric/config_test.go
+++ b/sdk/metric/config_test.go
@@ -307,8 +307,6 @@ func TestWithExemplarFilterOff(t *testing.T) {
 }
 
 func TestWithCardinalityLimit(t *testing.T) {
-	const envVar = "OTEL_GO_X_CARDINALITY_LIMIT"
-
 	cases := []struct {
 		name          string
 		envValue      string
@@ -349,7 +347,7 @@ func TestWithCardinalityLimit(t *testing.T) {
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
-			t.Setenv(envVar, tc.envValue)
+			t.Setenv("OTEL_GO_X_CARDINALITY_LIMIT", tc.envValue)
 			c := newConfig(tc.options)
 			assert.Equal(t, tc.expectedLimit, c.cardinalityLimit)
 		})

From eaa667c860e9f2fbc34db2b6dd617d5dddc80547 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 13:25:26 +0200
Subject: [PATCH 17/22] update docs

---
 sdk/metric/config.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index d3ee01cc8fa..44932ad8ab4 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -166,7 +166,8 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 // that can be collected for a single instrument.
 //
 // By default, the cardinality limit is set to 2000.
-// To disable the limit, set the value to 0 or a negative number.
+//
+// Setting this to a zero or negative value means no limit is applied.
 func WithCardinalityLimit(limit int) Option {
 	return optionFunc(func(cfg config) config {
 		cfg.cardinalityLimit = limit

From 6d2678685f6e02e262819e09c338add49e9f1332 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Fri, 11 Jul 2025 14:53:39 +0200
Subject: [PATCH 18/22] Handle error

---
 sdk/metric/config.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 44932ad8ab4..23f6eb838f1 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -199,6 +199,7 @@ func cardinalityLimitFromEnv() int {
 	}
 	n, err := strconv.Atoi(v)
 	if err != nil {
+		otel.Handle(err)
 		return defaultCardinalityLimit
 	}
 	return n

From 338964e36d3af4193f6aea6bbdc6706e45bf56ca Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Mon, 14 Jul 2025 09:34:10 +0200
Subject: [PATCH 19/22] update WithCardinalityLimit docs

---
 sdk/metric/config.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 23f6eb838f1..8702e0c3add 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -163,11 +163,14 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 // WithCardinalityLimit sets the cardinality limit for the MeterProvider.
 //
 // The cardinality limit is the hard limit on the number of metric streams
-// that can be collected for a single instrument.
+// that can be collected for a single instrument in a single collect cycle.
 //
 // By default, the cardinality limit is set to 2000.
 //
 // Setting this to a zero or negative value means no limit is applied.
+//
+// For backward compatibility, the environment variable `OTEL_GO_X_CARDINALITY_LIMIT`
+// can also be used to set this value.
 func WithCardinalityLimit(limit int) Option {
 	return optionFunc(func(cfg config) config {
 		cfg.cardinalityLimit = limit

From 37ce2a9c738978e33145fb38530ff3a6ad22a914 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Wed, 16 Jul 2025 09:14:01 +0200
Subject: [PATCH 20/22] change default to no limit

---
 CHANGELOG.md         | 3 +--
 sdk/metric/config.go | 9 ++++-----
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index eea098a1209..04282bcefbf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,8 +41,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   - `RPCGRPCResponseMetadata`
 - Add `ErrorType` attribute helper function to the `go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
 - Add `WithAllowKeyDuplication` in `go.opentelemetry.io/otel/sdk/log` which can be used to disable deduplication for log records. (#6968)
-- Add `WithCardinalityLimit` option to configure the cardinality limit in `go.opentelemetry.io/otel/sdk/metric`.
-  Now applies a default cardinality limit of 2000, which didn’t exist before. This is a breaking change. (#6996)
+- Add `WithCardinalityLimit` option to configure the cardinality limit in `go.opentelemetry.io/otel/sdk/metric`. (#6996)
 - Add `Clone` method to `Record` in `go.opentelemetry.io/otel/log` that returns a copy of the record with no shared state. (#7001)
 
 ### Changed
diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 8702e0c3add..cb817459bfc 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -25,7 +25,7 @@ type config struct {
 	cardinalityLimit int
 }
 
-const defaultCardinalityLimit = 2000
+const defaultCardinalityLimit = 0
 
 // readerSignals returns a force-flush and shutdown function for a
 // MeterProvider to call in their respective options. All Readers c contains
@@ -165,13 +165,12 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 // The cardinality limit is the hard limit on the number of metric streams
 // that can be collected for a single instrument in a single collect cycle.
 //
-// By default, the cardinality limit is set to 2000.
+// By default, the cardinality limit is set to 0.
 //
 // Setting this to a zero or negative value means no limit is applied.
-//
-// For backward compatibility, the environment variable `OTEL_GO_X_CARDINALITY_LIMIT`
-// can also be used to set this value.
 func WithCardinalityLimit(limit int) Option {
+	// For backward compatibility, the environment variable `OTEL_GO_X_CARDINALITY_LIMIT`
+	// can also be used to set this value.
 	return optionFunc(func(cfg config) config {
 		cfg.cardinalityLimit = limit
 		return cfg

From 9e210431f30c1e822c525e3dc02d6eacbcce03df Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Wed, 16 Jul 2025 09:38:45 +0200
Subject: [PATCH 21/22] Update sdk/metric/config.go

Co-authored-by: Damien Mathieu <42@dmathieu.com>
---
 sdk/metric/config.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index cb817459bfc..6da93a3f917 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -165,7 +165,7 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 // The cardinality limit is the hard limit on the number of metric streams
 // that can be collected for a single instrument in a single collect cycle.
 //
-// By default, the cardinality limit is set to 0.
+// By default, there is no limit applied.
 //
 // Setting this to a zero or negative value means no limit is applied.
 func WithCardinalityLimit(limit int) Option {

From 304b6d4f41d1c8eccec4c80b5df2bea079d6fe67 Mon Sep 17 00:00:00 2001
From: Yevhenii Solomchenko <ysolomchenko@splunk.com>
Date: Thu, 17 Jul 2025 09:53:07 +0200
Subject: [PATCH 22/22] Update sdk/metric/config.go

Co-authored-by: Cijo Thomas <cithomas@microsoft.com>
---
 sdk/metric/config.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/metric/config.go b/sdk/metric/config.go
index 6da93a3f917..7580c074019 100644
--- a/sdk/metric/config.go
+++ b/sdk/metric/config.go
@@ -162,7 +162,7 @@ func WithExemplarFilter(filter exemplar.Filter) Option {
 
 // WithCardinalityLimit sets the cardinality limit for the MeterProvider.
 //
-// The cardinality limit is the hard limit on the number of metric streams
+// The cardinality limit is the hard limit on the number of metric datapoints
 // that can be collected for a single instrument in a single collect cycle.
 //
 // By default, there is no limit applied.