diff --git a/internal/generate/serviceendpointtests/file.tmpl b/internal/generate/serviceendpointtests/file.tmpl
index ab0b5823ab9..f10ccd84f79 100644
--- a/internal/generate/serviceendpointtests/file.tmpl
+++ b/internal/generate/serviceendpointtests/file.tmpl
@@ -38,6 +38,9 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	{{- if gt (len .Aliases) 0 }}
+    "github.com/hashicorp/go-cty/cty"
+	{{- end }}
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -129,7 +132,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName{{ $i }}EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 {{ end }}
 
@@ -205,7 +208,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName{{ $i }}EndpointInConfig,
 				withAliasName{{ $j }}EndpointInConfig,
 		},
-			expected: expectAliasName{{ $i }}ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName{{ $i }}ConfigEndpoint()),
 		},
 {{ end }}
 
@@ -592,6 +595,19 @@ func withAliasName{{ $i }}EndpointInConfig(setup *caseSetup) {
 }
 {{ end }}
 
+{{ if gt (len .Aliases) 0 }}
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		{{ range $i, $alias := .Aliases -}}
+		aliasName{{ $i }},
+		{{ end }}
+	))
+	return e
+}
+{{ end }}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/provider/provider.go b/internal/provider/provider.go
index 6c8f39dedce..ee399ccb860 100644
--- a/internal/provider/provider.go
+++ b/internal/provider/provider.go
@@ -8,12 +8,14 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/YakDriver/regexache"
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/feature/ec2/imds"
 	awsbase "github.com/hashicorp/aws-sdk-go-base/v2"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-log/tflog"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
@@ -865,18 +867,50 @@ func expandIgnoreTags(ctx context.Context, tfMap map[string]interface{}) *tftags
 func expandEndpoints(_ context.Context, tfList []interface{}) (map[string]string, diag.Diagnostics) {
 	var diags diag.Diagnostics
 
+	endpointsPath := cty.GetAttrPath("endpoints")
+
+	if l := len(tfList); l > 1 {
+		diags = append(diags, errs.NewAttributeWarningDiagnostic(
+			endpointsPath,
+			"Invalid Attribute Value",
+			fmt.Sprintf("Attribute %q should have at most 1 element, got %d."+
+				"\n\nThis will be an error in a future release.",
+				errs.PathString(endpointsPath), l),
+		))
+	}
+
 	endpoints := make(map[string]string)
 
-	for _, tfMapRaw := range tfList {
+	for i, tfMapRaw := range tfList {
 		tfMap, ok := tfMapRaw.(map[string]interface{})
 
 		if !ok {
 			continue
 		}
 
+		elementPath := endpointsPath.IndexInt(i)
+
 		for _, endpoint := range names.Endpoints() {
 			pkg := endpoint.ProviderPackage
 
+			if len(endpoint.Aliases) > 0 {
+				count := 0
+				attrs := []string{pkg}
+				if tfMap[pkg] != "" {
+					count++
+				}
+				for _, alias := range endpoint.Aliases {
+					attrs = append(attrs, alias)
+					if tfMap[alias] != "" {
+						count++
+					}
+				}
+
+				if count > 1 {
+					diags = append(diags, ConflictingEndpointsWarningDiag(elementPath, attrs...))
+				}
+			}
+
 			if endpoints[pkg] == "" {
 				if v := tfMap[pkg].(string); v != "" {
 					endpoints[pkg] = v
@@ -941,3 +975,18 @@ func DeprecatedEnvVarDiag(envvar, replacement string) diag.Diagnostic {
 		fmt.Sprintf(`The environment variable "%s" is deprecated. Use environment variable "%s" instead.`, envvar, replacement),
 	)
 }
+
+func ConflictingEndpointsWarningDiag(elementPath cty.Path, attrs ...string) diag.Diagnostic {
+	attrPaths := make([]string, len(attrs))
+	for i, attr := range attrs {
+		path := elementPath.GetAttr(attr)
+		attrPaths[i] = `"` + errs.PathString(path) + `"`
+	}
+	return errs.NewAttributeWarningDiagnostic(
+		elementPath,
+		"Invalid Attribute Combination",
+		fmt.Sprintf("Only one of the following attributes should be set: %s"+
+			"\n\nThis will be an error in a future release.",
+			strings.Join(attrPaths, ", ")),
+	)
+}
diff --git a/internal/provider/provider_test.go b/internal/provider/provider_test.go
index cd39a1d3d9a..3b279ba06f6 100644
--- a/internal/provider/provider_test.go
+++ b/internal/provider/provider_test.go
@@ -10,6 +10,7 @@ import (
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-provider-aws/internal/errs/sdkdiag"
 	"github.com/hashicorp/terraform-provider-aws/names"
@@ -64,6 +65,7 @@ func TestEndpointMultipleKeys(t *testing.T) { //nolint:paralleltest
 		endpoints        map[string]string
 		expectedService  string
 		expectedEndpoint string
+		expectedDiags    diag.Diagnostics
 	}{
 		{
 			endpoints: map[string]string{
@@ -86,6 +88,11 @@ func TestEndpointMultipleKeys(t *testing.T) { //nolint:paralleltest
 			},
 			expectedService:  names.Transcribe,
 			expectedEndpoint: "https://transcribe.fake.test",
+			expectedDiags: diag.Diagnostics{ConflictingEndpointsWarningDiag(
+				cty.GetAttrPath("endpoints").IndexInt(0),
+				"transcribe",
+				"transcribeservice",
+			)},
 		},
 	}
 
@@ -101,10 +108,8 @@ func TestEndpointMultipleKeys(t *testing.T) { //nolint:paralleltest
 			endpoints[k] = v
 		}
 
-		var expectedDiags diag.Diagnostics
-
 		results, diags := expandEndpoints(ctx, []interface{}{endpoints})
-		if diff := cmp.Diff(diags, expectedDiags, cmp.Comparer(sdkdiag.Comparer)); diff != "" {
+		if diff := cmp.Diff(diags, testcase.expectedDiags, cmp.Comparer(sdkdiag.Comparer)); diff != "" {
 			t.Errorf("unexpected diagnostics difference: %s", diff)
 		}
 
diff --git a/internal/service/amp/service_endpoints_gen_test.go b/internal/service/amp/service_endpoints_gen_test.go
index d4f73b6e29c..f90a42643b1 100644
--- a/internal/service/amp/service_endpoints_gen_test.go
+++ b/internal/service/amp/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -398,6 +399,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/appautoscaling/service_endpoints_gen_test.go b/internal/service/appautoscaling/service_endpoints_gen_test.go
index 86afd209161..1443fc2c249 100644
--- a/internal/service/appautoscaling/service_endpoints_gen_test.go
+++ b/internal/service/appautoscaling/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/appintegrations/service_endpoints_gen_test.go b/internal/service/appintegrations/service_endpoints_gen_test.go
index fce8e4f48ee..7300197c2f7 100644
--- a/internal/service/appintegrations/service_endpoints_gen_test.go
+++ b/internal/service/appintegrations/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/ce/service_endpoints_gen_test.go b/internal/service/ce/service_endpoints_gen_test.go
index 433fae70550..a41c959506f 100644
--- a/internal/service/ce/service_endpoints_gen_test.go
+++ b/internal/service/ce/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/cloudcontrol/service_endpoints_gen_test.go b/internal/service/cloudcontrol/service_endpoints_gen_test.go
index fcf267e9159..8a6b3972ecf 100644
--- a/internal/service/cloudcontrol/service_endpoints_gen_test.go
+++ b/internal/service/cloudcontrol/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/cloudhsmv2/service_endpoints_gen_test.go b/internal/service/cloudhsmv2/service_endpoints_gen_test.go
index a5057648ae3..501c1480170 100644
--- a/internal/service/cloudhsmv2/service_endpoints_gen_test.go
+++ b/internal/service/cloudhsmv2/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/cognitoidp/service_endpoints_gen_test.go b/internal/service/cognitoidp/service_endpoints_gen_test.go
index b2c9756daf2..e5c8706b3bd 100644
--- a/internal/service/cognitoidp/service_endpoints_gen_test.go
+++ b/internal/service/cognitoidp/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/configservice/service_endpoints_gen_test.go b/internal/service/configservice/service_endpoints_gen_test.go
index be10a3c2bb4..cc6259c353c 100644
--- a/internal/service/configservice/service_endpoints_gen_test.go
+++ b/internal/service/configservice/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/cur/service_endpoints_gen_test.go b/internal/service/cur/service_endpoints_gen_test.go
index d067a9c26a4..4f0f425ebf9 100644
--- a/internal/service/cur/service_endpoints_gen_test.go
+++ b/internal/service/cur/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/deploy/service_endpoints_gen_test.go b/internal/service/deploy/service_endpoints_gen_test.go
index 23a67f0de19..66bc5169420 100644
--- a/internal/service/deploy/service_endpoints_gen_test.go
+++ b/internal/service/deploy/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/dms/service_endpoints_gen_test.go b/internal/service/dms/service_endpoints_gen_test.go
index 4d16212d5c8..f739a1f8155 100644
--- a/internal/service/dms/service_endpoints_gen_test.go
+++ b/internal/service/dms/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -388,6 +389,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/ds/service_endpoints_gen_test.go b/internal/service/ds/service_endpoints_gen_test.go
index 072de5eb7c1..3efc0fd5bae 100644
--- a/internal/service/ds/service_endpoints_gen_test.go
+++ b/internal/service/ds/service_endpoints_gen_test.go
@@ -19,6 +19,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -95,7 +96,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -356,6 +357,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/elasticbeanstalk/service_endpoints_gen_test.go b/internal/service/elasticbeanstalk/service_endpoints_gen_test.go
index e1362d4a2a9..fa174162af4 100644
--- a/internal/service/elasticbeanstalk/service_endpoints_gen_test.go
+++ b/internal/service/elasticbeanstalk/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/elasticsearch/service_endpoints_gen_test.go b/internal/service/elasticsearch/service_endpoints_gen_test.go
index a056b2b3654..2b2bbc23d99 100644
--- a/internal/service/elasticsearch/service_endpoints_gen_test.go
+++ b/internal/service/elasticsearch/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -388,6 +389,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/elb/service_endpoints_gen_test.go b/internal/service/elb/service_endpoints_gen_test.go
index 503f847ef3f..0b097f80895 100644
--- a/internal/service/elb/service_endpoints_gen_test.go
+++ b/internal/service/elb/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/elbv2/service_endpoints_gen_test.go b/internal/service/elbv2/service_endpoints_gen_test.go
index 0ed668e8a4c..bf3b294dd1b 100644
--- a/internal/service/elbv2/service_endpoints_gen_test.go
+++ b/internal/service/elbv2/service_endpoints_gen_test.go
@@ -19,6 +19,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -95,7 +96,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -356,6 +357,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/events/service_endpoints_gen_test.go b/internal/service/events/service_endpoints_gen_test.go
index 05e07af7586..ff3c08e04f0 100644
--- a/internal/service/events/service_endpoints_gen_test.go
+++ b/internal/service/events/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -388,6 +389,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/evidently/service_endpoints_gen_test.go b/internal/service/evidently/service_endpoints_gen_test.go
index bd01fcbab84..ea83fc1063e 100644
--- a/internal/service/evidently/service_endpoints_gen_test.go
+++ b/internal/service/evidently/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/grafana/service_endpoints_gen_test.go b/internal/service/grafana/service_endpoints_gen_test.go
index 60c4a41b6ea..b7f2038d8c3 100644
--- a/internal/service/grafana/service_endpoints_gen_test.go
+++ b/internal/service/grafana/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -388,6 +389,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/inspector2/service_endpoints_gen_test.go b/internal/service/inspector2/service_endpoints_gen_test.go
index f20ed492eb0..5a6166f7163 100644
--- a/internal/service/inspector2/service_endpoints_gen_test.go
+++ b/internal/service/inspector2/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/kafka/service_endpoints_gen_test.go b/internal/service/kafka/service_endpoints_gen_test.go
index 5ffe034ad41..42beb5403a9 100644
--- a/internal/service/kafka/service_endpoints_gen_test.go
+++ b/internal/service/kafka/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/lexmodels/service_endpoints_gen_test.go b/internal/service/lexmodels/service_endpoints_gen_test.go
index dff0aa2d0cf..0b3874a6752 100644
--- a/internal/service/lexmodels/service_endpoints_gen_test.go
+++ b/internal/service/lexmodels/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -98,7 +99,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -106,7 +107,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 2 config": {
@@ -114,7 +115,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName2EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -163,7 +164,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides alias name 2 config": {
@@ -171,7 +172,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName2EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -220,7 +221,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName1EndpointInConfig,
 				withAliasName2EndpointInConfig,
 			},
-			expected: expectAliasName1ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName1ConfigEndpoint()),
 		},
 
 		"alias name 1 endpoint config overrides aws service envvar": {
@@ -465,6 +466,17 @@ func withAliasName2EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName2] = aliasName2ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+		aliasName2,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/lexv2models/service_endpoints_gen_test.go b/internal/service/lexv2models/service_endpoints_gen_test.go
index 6c64017921b..2f48c1aa82f 100644
--- a/internal/service/lexv2models/service_endpoints_gen_test.go
+++ b/internal/service/lexv2models/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/location/service_endpoints_gen_test.go b/internal/service/location/service_endpoints_gen_test.go
index ea2b3d2f63e..e6f3945b584 100644
--- a/internal/service/location/service_endpoints_gen_test.go
+++ b/internal/service/location/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/logs/service_endpoints_gen_test.go b/internal/service/logs/service_endpoints_gen_test.go
index b292d3650cc..a44d09f23aa 100644
--- a/internal/service/logs/service_endpoints_gen_test.go
+++ b/internal/service/logs/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -398,6 +399,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/oam/service_endpoints_gen_test.go b/internal/service/oam/service_endpoints_gen_test.go
index 30871e193d6..e0f2937fd7e 100644
--- a/internal/service/oam/service_endpoints_gen_test.go
+++ b/internal/service/oam/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/opensearch/service_endpoints_gen_test.go b/internal/service/opensearch/service_endpoints_gen_test.go
index 7b02c20b97f..42acbb1c23c 100644
--- a/internal/service/opensearch/service_endpoints_gen_test.go
+++ b/internal/service/opensearch/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/osis/service_endpoints_gen_test.go b/internal/service/osis/service_endpoints_gen_test.go
index 2ead9d805d0..bd64fefeff3 100644
--- a/internal/service/osis/service_endpoints_gen_test.go
+++ b/internal/service/osis/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/rbin/service_endpoints_gen_test.go b/internal/service/rbin/service_endpoints_gen_test.go
index 138bc6e2595..a088c44598a 100644
--- a/internal/service/rbin/service_endpoints_gen_test.go
+++ b/internal/service/rbin/service_endpoints_gen_test.go
@@ -19,6 +19,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -95,7 +96,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -332,6 +333,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/redshiftdata/service_endpoints_gen_test.go b/internal/service/redshiftdata/service_endpoints_gen_test.go
index 22eefab8f27..5ebaf492d91 100644
--- a/internal/service/redshiftdata/service_endpoints_gen_test.go
+++ b/internal/service/redshiftdata/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -331,6 +332,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/resourcegroupstaggingapi/service_endpoints_gen_test.go b/internal/service/resourcegroupstaggingapi/service_endpoints_gen_test.go
index f6bec1f4e95..f41ab6ef241 100644
--- a/internal/service/resourcegroupstaggingapi/service_endpoints_gen_test.go
+++ b/internal/service/resourcegroupstaggingapi/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/rum/service_endpoints_gen_test.go b/internal/service/rum/service_endpoints_gen_test.go
index d6826d33b3f..7f31be1de94 100644
--- a/internal/service/rum/service_endpoints_gen_test.go
+++ b/internal/service/rum/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/s3/service_endpoints_gen_test.go b/internal/service/s3/service_endpoints_gen_test.go
index 7b2f144e359..46b97af4805 100644
--- a/internal/service/s3/service_endpoints_gen_test.go
+++ b/internal/service/s3/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -453,6 +454,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/serverlessrepo/service_endpoints_gen_test.go b/internal/service/serverlessrepo/service_endpoints_gen_test.go
index fc560f384e9..f65a160dfd5 100644
--- a/internal/service/serverlessrepo/service_endpoints_gen_test.go
+++ b/internal/service/serverlessrepo/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -96,7 +97,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides alias name 1 config": {
@@ -104,7 +105,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -153,7 +154,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withAliasName0EndpointInConfig,
 				withAliasName1EndpointInConfig,
 			},
-			expected: expectAliasName0ConfigEndpoint(),
+			expected: conflictsWith(expectAliasName0ConfigEndpoint()),
 		},
 
 		"alias name 0 endpoint config overrides aws service envvar": {
@@ -388,6 +389,16 @@ func withAliasName1EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName1] = aliasName1ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+		aliasName1,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/servicecatalogappregistry/service_endpoints_gen_test.go b/internal/service/servicecatalogappregistry/service_endpoints_gen_test.go
index 61db3f7fad0..8a415e84acc 100644
--- a/internal/service/servicecatalogappregistry/service_endpoints_gen_test.go
+++ b/internal/service/servicecatalogappregistry/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/sfn/service_endpoints_gen_test.go b/internal/service/sfn/service_endpoints_gen_test.go
index 2efaf2fb681..2b3aee2c8bc 100644
--- a/internal/service/sfn/service_endpoints_gen_test.go
+++ b/internal/service/sfn/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/simpledb/service_endpoints_gen_test.go b/internal/service/simpledb/service_endpoints_gen_test.go
index db4ad4da404..af83226b7e7 100644
--- a/internal/service/simpledb/service_endpoints_gen_test.go
+++ b/internal/service/simpledb/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -319,6 +320,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }
diff --git a/internal/service/transcribe/service_endpoints_gen_test.go b/internal/service/transcribe/service_endpoints_gen_test.go
index 5ebe78a6663..424dc5543db 100644
--- a/internal/service/transcribe/service_endpoints_gen_test.go
+++ b/internal/service/transcribe/service_endpoints_gen_test.go
@@ -18,6 +18,7 @@ import (
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"github.com/google/go-cmp/cmp"
 	"github.com/hashicorp/aws-sdk-go-base/v2/servicemocks"
+	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	terraformsdk "github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 	"github.com/hashicorp/terraform-provider-aws/internal/conns"
@@ -94,7 +95,7 @@ func TestEndpointConfiguration(t *testing.T) { //nolint:paralleltest // uses t.S
 				withPackageNameEndpointInConfig,
 				withAliasName0EndpointInConfig,
 			},
-			expected: expectPackageNameConfigEndpoint(),
+			expected: conflictsWith(expectPackageNameConfigEndpoint()),
 		},
 
 		"package name endpoint config overrides aws service envvar": {
@@ -329,6 +330,15 @@ func withAliasName0EndpointInConfig(setup *caseSetup) {
 	endpoints[aliasName0] = aliasName0ConfigEndpoint
 }
 
+func conflictsWith(e caseExpectations) caseExpectations {
+	e.diags = append(e.diags, provider.ConflictingEndpointsWarningDiag(
+		cty.GetAttrPath("endpoints").IndexInt(0),
+		packageName,
+		aliasName0,
+	))
+	return e
+}
+
 func withAwsEnvVar(setup *caseSetup) {
 	setup.environmentVariables[awsEnvVar] = awsServiceEnvvarEndpoint
 }