diff --git a/Makefile b/Makefile
index 88d01fe4909..4ae6fc07ac7 100644
--- a/Makefile
+++ b/Makefile
@@ -525,14 +525,18 @@ workflowcheck: $(WORKFLOWCHECK)
 check: lint shell-check
 
 ##### Tests #####
+# verify-test-log reads the whole file, so a log left behind by an earlier run
+# would be judged as if it belonged to this one.
 clean-test-output:
 	@printf $(COLOR) "Delete test output..."
 	@rm -rf $(TEST_OUTPUT_ROOT)
+	@rm -f test.log
 	@go clean -testcache
 
 build-tests:
 	@printf $(COLOR) "Build tests..."
-	@CGO_ENABLED=$(CGO_ENABLED) go test $(TEST_TAG_FLAG) -exec="true" -count=0 $(TEST_DIRS)
+	@CGO_ENABLED=$(CGO_ENABLED) go test $(TEST_TAG_FLAG) -exec="true" -count=0 $(filter-out $(MIXED_BRAIN_TEST_ROOT)%,$(TEST_DIRS))
+	@cd $(MIXED_BRAIN_TEST_ROOT) && CGO_ENABLED=1 go test $(TEST_TAG_FLAG) -exec="true" -count=0 ./...
 
 unit-test: clean-test-output
 	@printf $(COLOR) "Run unit tests..."
diff --git a/cmd/tools/getproto/files.go b/cmd/tools/getproto/files.go
index 4006de0ad41..3b1e31ca412 100644
--- a/cmd/tools/getproto/files.go
+++ b/cmd/tools/getproto/files.go
@@ -28,6 +28,7 @@ import (
 	rules "go.temporal.io/api/rules/v1"
 	schedule "go.temporal.io/api/schedule/v1"
 	sdk "go.temporal.io/api/sdk/v1"
+	stream "go.temporal.io/api/stream/v1"
 	taskqueue "go.temporal.io/api/taskqueue/v1"
 	update "go.temporal.io/api/update/v1"
 	version "go.temporal.io/api/version/v1"
@@ -93,6 +94,7 @@ func init() {
 	importMap["temporal/api/sdk/v1/task_complete_metadata.proto"] = sdk.File_temporal_api_sdk_v1_task_complete_metadata_proto
 	importMap["temporal/api/sdk/v1/user_metadata.proto"] = sdk.File_temporal_api_sdk_v1_user_metadata_proto
 	importMap["temporal/api/sdk/v1/worker_config.proto"] = sdk.File_temporal_api_sdk_v1_worker_config_proto
+	importMap["temporal/api/stream/v1/message.proto"] = stream.File_temporal_api_stream_v1_message_proto
 	importMap["temporal/api/taskqueue/v1/message.proto"] = taskqueue.File_temporal_api_taskqueue_v1_message_proto
 	importMap["temporal/api/update/v1/message.proto"] = update.File_temporal_api_update_v1_message_proto
 	importMap["temporal/api/version/v1/message.proto"] = version.File_temporal_api_version_v1_message_proto
diff --git a/common/metrics/otel_metrics_handler_test.go b/common/metrics/otel_metrics_handler_test.go
index a2d0b34eb53..bf08a9460e1 100644
--- a/common/metrics/otel_metrics_handler_test.go
+++ b/common/metrics/otel_metrics_handler_test.go
@@ -193,9 +193,14 @@ func TestMeter(t *testing.T) {
 		cmpopts.SortSlices(func(x, y metricdata.Metrics) bool {
 			return x.Name < y.Name
 		}),
-		cmpopts.IgnoreFields(metricdata.DataPoint[int64]{}, "StartTime", "Time"),
-		cmpopts.IgnoreFields(metricdata.DataPoint[float64]{}, "StartTime", "Time"),
-		cmpopts.IgnoreFields(metricdata.HistogramDataPoint[int64]{}, "StartTime", "Time", "Bounds"),
+		// Exemplars are ignored rather than equated empty: the SDK hands back
+		// either a nil or an allocated-but-empty slice depending on whether
+		// its reservoir was ever touched, and equating empty globally would
+		// also hide a nil-versus-empty attribute set or data point.
+		cmpopts.IgnoreFields(metricdata.DataPoint[int64]{}, "StartTime", "Time", "Exemplars"),
+		cmpopts.IgnoreFields(metricdata.DataPoint[float64]{}, "StartTime", "Time", "Exemplars"),
+		cmpopts.IgnoreFields(
+			metricdata.HistogramDataPoint[int64]{}, "StartTime", "Time", "Bounds", "Exemplars"),
 	); diff != "" {
 		t.Errorf("mismatch (-want, +got):\n%s", diff)
 	}
@@ -264,7 +269,8 @@ func TestMeter_TimerInSeconds(t *testing.T) {
 		cmp.Comparer(func(a1, a2 attribute.Set) bool {
 			return a1.Equals(&a2)
 		}),
-		cmpopts.IgnoreFields(metricdata.HistogramDataPoint[float64]{}, "StartTime", "Time", "Bounds"),
+		cmpopts.IgnoreFields(
+			metricdata.HistogramDataPoint[float64]{}, "StartTime", "Time", "Bounds", "Exemplars"),
 	); diff != "" {
 		t.Errorf("mismatch (-want, +got):\n%s", diff)
 	}
diff --git a/go.mod b/go.mod
index b9c7674a01d..cb3edd1f83d 100644
--- a/go.mod
+++ b/go.mod
@@ -236,3 +236,5 @@ require (
 )
 
 tool golang.org/x/perf/cmd/benchstat
+
+replace go.temporal.io/api => github.com/moedash/api-go v1.63.6-0.20260925231147-63d1722ce567
diff --git a/go.sum b/go.sum
index ec1c673c1b4..2eff8776cb5 100644
--- a/go.sum
+++ b/go.sum
@@ -321,6 +321,8 @@ github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJ
 github.com/modern-go/reflect2 v1.0.2/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
 github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee h1:W5t00kpgFdJifH4BDsTlE89Zl93FEloxaWZfGcifgq8=
 github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
+github.com/moedash/api-go v1.63.6-0.20260925231147-63d1722ce567 h1:lKAIMDl+aIBL3Y4GxDXab40rR6eVhGnPDnFbzzSCD2Y=
+github.com/moedash/api-go v1.63.6-0.20260925231147-63d1722ce567/go.mod h1:acM0I9WPuYg8W3Pd9jOZvEgi7mRUttUQ4+e7fowKVnM=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/ncruces/go-strftime v1.0.0 h1:HMFp8mLCTPp341M/ZnA4qaf7ZlsbTc+miZjCLOFAw7w=
@@ -481,8 +483,6 @@ go.opentelemetry.io/proto/slim/otlp/collector/profiles/v1development v0.3.0 h1:R
 go.opentelemetry.io/proto/slim/otlp/collector/profiles/v1development v0.3.0/go.mod h1:I89cynRj8y+383o7tEQVg2SVA6SRgDVIouWPUVXjx0U=
 go.opentelemetry.io/proto/slim/otlp/profiles/v1development v0.3.0 h1:CQvJSldHRUN6Z8jsUeYv8J0lXRvygALXIzsmAeCcZE0=
 go.opentelemetry.io/proto/slim/otlp/profiles/v1development v0.3.0/go.mod h1:xSQ+mEfJe/GjK1LXEyVOoSI1N9JV9ZI923X5kup43W4=
-go.temporal.io/api v1.63.6-0.20260909222256-20151aa90480 h1:1w2xEZFpL7R9NagEQeWTh7oZmZU3YUJGogusn9/LfCg=
-go.temporal.io/api v1.63.6-0.20260909222256-20151aa90480/go.mod h1:acM0I9WPuYg8W3Pd9jOZvEgi7mRUttUQ4+e7fowKVnM=
 go.temporal.io/auto-scaled-workers v0.0.0-20260811170210-91f6fe1d10ab h1:99wXW0317BBi49d6xgMdA0EZtvA+xbBUWV4HsTEGEcg=
 go.temporal.io/auto-scaled-workers v0.0.0-20260811170210-91f6fe1d10ab/go.mod h1:hhHijO9XRPIkAflLJJHix61M9FzbRPqk8fSydkcLkqw=
 go.temporal.io/sdk v1.48.0 h1:WDctKDVuh0Z8Nf7euAyqs/EwcPg1JTIIq1Fut8Tq118=
diff --git a/tests/api_fork_test.go b/tests/api_fork_test.go
new file mode 100644
index 00000000000..c4e092ed005
--- /dev/null
+++ b/tests/api_fork_test.go
@@ -0,0 +1,59 @@
+package tests
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	commandpb "go.temporal.io/api/command/v1"
+	enumspb "go.temporal.io/api/enums/v1"
+	historypb "go.temporal.io/api/history/v1"
+	streampb "go.temporal.io/api/stream/v1"
+	"go.temporal.io/api/workflowservice/v1"
+	"google.golang.org/protobuf/proto"
+)
+
+// The api fork has to round-trip the new shapes over the wire, not merely
+// compile. A field added without its descriptor would compile and silently
+// drop on marshal.
+func TestApiForkCarriesStreamShapes(t *testing.T) {
+	require.Equal(t, enumspb.COMMAND_TYPE_APPEND_STREAM_RECORDS, enumspb.CommandType(19))
+
+	cmd := &commandpb.Command{
+		CommandType: enumspb.COMMAND_TYPE_APPEND_STREAM_RECORDS,
+		Attributes: &commandpb.Command_AppendStreamRecordsCommandAttributes{
+			AppendStreamRecordsCommandAttributes: &commandpb.AppendStreamRecordsCommandAttributes{
+				StreamName: "s1",
+				Records:    []*streampb.StreamRecord{{Topic: "tokens"}},
+			},
+		},
+	}
+	b, err := proto.Marshal(cmd)
+	require.NoError(t, err)
+	var back commandpb.Command
+	require.NoError(t, proto.Unmarshal(b, &back))
+	require.Equal(t, "s1", back.GetAppendStreamRecordsCommandAttributes().GetStreamName())
+	require.Equal(t, "tokens",
+		back.GetAppendStreamRecordsCommandAttributes().GetRecords()[0].GetTopic())
+
+	resp := &workflowservice.PollWorkflowTaskQueueResponse{
+		StreamSlices: []*streampb.StreamSlice{{StreamId: "s1", FromOffset: 4, ToOffset: 7}},
+	}
+	rb, err := proto.Marshal(resp)
+	require.NoError(t, err)
+	var rback workflowservice.PollWorkflowTaskQueueResponse
+	require.NoError(t, proto.Unmarshal(rb, &rback))
+	require.Equal(t, int64(7), rback.GetStreamSlices()[0].GetToOffset())
+
+	attrs := &historypb.WorkflowTaskCompletedEventAttributes{
+		ConsumedStreamRanges: []*streampb.StreamRange{{StreamId: "s1", FromOffset: 4, ToOffset: 4}},
+	}
+	ab, err := proto.Marshal(attrs)
+	require.NoError(t, err)
+	var aback historypb.WorkflowTaskCompletedEventAttributes
+	require.NoError(t, proto.Unmarshal(ab, &aback))
+	// An empty range has to survive the round trip: it is the fact that a
+	// subscription observed nothing, which replay must reproduce.
+	require.Len(t, aback.GetConsumedStreamRanges(), 1)
+	require.Equal(t,
+		aback.GetConsumedStreamRanges()[0].GetFromOffset(), aback.GetConsumedStreamRanges()[0].GetToOffset())
+}