Add Nix flake for mcp and mcp-agent

Exposes two packages:
- default (mcp CLI) for operator workstations
- mcp-agent for managed nodes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/google.golang.org/grpc/internal/stats/labels.go

@@ -0,0 +1,42 @@
+/*
+ *
+ * Copyright 2024 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package stats provides internal stats related functionality.
+package stats
+
+import "context"
+
+// Labels are the labels for metrics.
+type Labels struct {
+	// TelemetryLabels are the telemetry labels to record.
+	TelemetryLabels map[string]string
+}
+
+type labelsKey struct{}
+
+// GetLabels returns the Labels stored in the context, or nil if there is one.
+func GetLabels(ctx context.Context) *Labels {
+	labels, _ := ctx.Value(labelsKey{}).(*Labels)
+	return labels
+}
+
+// SetLabels sets the Labels in the context.
+func SetLabels(ctx context.Context, labels *Labels) context.Context {
+	// could also append
+	return context.WithValue(ctx, labelsKey{}, labels)
+}

vendor/google.golang.org/grpc/internal/stats/metrics_recorder_list.go

@@ -0,0 +1,175 @@
+/*
+ * Copyright 2024 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package stats
+
+import (
+	"fmt"
+
+	estats "google.golang.org/grpc/experimental/stats"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/stats"
+)
+
+// MetricsRecorderList forwards Record calls to all of its metricsRecorders.
+//
+// It eats any record calls where the label values provided do not match the
+// number of label keys.
+type MetricsRecorderList struct {
+	internal.EnforceMetricsRecorderEmbedding
+	// metricsRecorders are the metrics recorders this list will forward to.
+	metricsRecorders []estats.MetricsRecorder
+}
+
+// NewMetricsRecorderList creates a new metric recorder list with all the stats
+// handlers provided which implement the MetricsRecorder interface.
+// If no stats handlers provided implement the MetricsRecorder interface,
+// the MetricsRecorder list returned is a no-op.
+func NewMetricsRecorderList(shs []stats.Handler) *MetricsRecorderList {
+	var mrs []estats.MetricsRecorder
+	for _, sh := range shs {
+		if mr, ok := sh.(estats.MetricsRecorder); ok {
+			mrs = append(mrs, mr)
+		}
+	}
+	return &MetricsRecorderList{
+		metricsRecorders: mrs,
+	}
+}
+
+func verifyLabels(desc *estats.MetricDescriptor, labelsRecv ...string) {
+	if got, want := len(labelsRecv), len(desc.Labels)+len(desc.OptionalLabels); got != want {
+		panic(fmt.Sprintf("Received %d labels in call to record metric %q, but expected %d.", got, desc.Name, want))
+	}
+}
+
+// RecordInt64Count records the measurement alongside labels on the int
+// count associated with the provided handle.
+func (l *MetricsRecorderList) RecordInt64Count(handle *estats.Int64CountHandle, incr int64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordInt64Count(handle, incr, labels...)
+	}
+}
+
+// RecordInt64UpDownCount records the measurement alongside labels on the int
+// count associated with the provided handle.
+func (l *MetricsRecorderList) RecordInt64UpDownCount(handle *estats.Int64UpDownCountHandle, incr int64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordInt64UpDownCount(handle, incr, labels...)
+	}
+}
+
+// RecordFloat64Count records the measurement alongside labels on the float
+// count associated with the provided handle.
+func (l *MetricsRecorderList) RecordFloat64Count(handle *estats.Float64CountHandle, incr float64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordFloat64Count(handle, incr, labels...)
+	}
+}
+
+// RecordInt64Histo records the measurement alongside labels on the int
+// histo associated with the provided handle.
+func (l *MetricsRecorderList) RecordInt64Histo(handle *estats.Int64HistoHandle, incr int64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordInt64Histo(handle, incr, labels...)
+	}
+}
+
+// RecordFloat64Histo records the measurement alongside labels on the float
+// histo associated with the provided handle.
+func (l *MetricsRecorderList) RecordFloat64Histo(handle *estats.Float64HistoHandle, incr float64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordFloat64Histo(handle, incr, labels...)
+	}
+}
+
+// RecordInt64Gauge records the measurement alongside labels on the int
+// gauge associated with the provided handle.
+func (l *MetricsRecorderList) RecordInt64Gauge(handle *estats.Int64GaugeHandle, incr int64, labels ...string) {
+	verifyLabels(handle.Descriptor(), labels...)
+
+	for _, metricRecorder := range l.metricsRecorders {
+		metricRecorder.RecordInt64Gauge(handle, incr, labels...)
+	}
+}
+
+// RegisterAsyncReporter forwards the registration to all underlying metrics
+// recorders.
+//
+// It returns a cleanup function that, when called, invokes the cleanup function
+// returned by each underlying recorder, ensuring the reporter is unregistered
+// from all of them.
+func (l *MetricsRecorderList) RegisterAsyncReporter(reporter estats.AsyncMetricReporter, metrics ...estats.AsyncMetric) func() {
+	descriptorsMap := make(map[*estats.MetricDescriptor]bool, len(metrics))
+	for _, m := range metrics {
+		descriptorsMap[m.Descriptor()] = true
+	}
+	unregisterFns := make([]func(), 0, len(l.metricsRecorders))
+	for _, mr := range l.metricsRecorders {
+		// Wrap the AsyncMetricsRecorder to intercept calls to RecordInt64Gauge
+		// and validate the labels.
+		wrappedCallback := func(recorder estats.AsyncMetricsRecorder) error {
+			wrappedRecorder := &asyncRecorderWrapper{
+				delegate:    recorder,
+				descriptors: descriptorsMap,
+			}
+			return reporter.Report(wrappedRecorder)
+		}
+		unregisterFns = append(unregisterFns, mr.RegisterAsyncReporter(estats.AsyncMetricReporterFunc(wrappedCallback), metrics...))
+	}
+
+	// Wrap the cleanup function using the internal delegate.
+	// In production, this returns realCleanup as-is.
+	// In tests, the leak checker can swap this to track the registration lifetime.
+	return internal.AsyncReporterCleanupDelegate(defaultCleanUp(unregisterFns))
+}
+
+func defaultCleanUp(unregisterFns []func()) func() {
+	return func() {
+		for _, unregister := range unregisterFns {
+			unregister()
+		}
+	}
+}
+
+type asyncRecorderWrapper struct {
+	delegate    estats.AsyncMetricsRecorder
+	descriptors map[*estats.MetricDescriptor]bool
+}
+
+// RecordIntAsync64Gauge records the measurement alongside labels on the int
+// gauge associated with the provided handle.
+func (w *asyncRecorderWrapper) RecordInt64AsyncGauge(handle *estats.Int64AsyncGaugeHandle, value int64, labels ...string) {
+	// Ensure only metrics for descriptors passed during callback registration
+	// are emitted.
+	d := handle.Descriptor()
+	if _, ok := w.descriptors[d]; !ok {
+		return
+	}
+	// Validate labels and delegate.
+	verifyLabels(d, labels...)
+	w.delegate.RecordInt64AsyncGauge(handle, value, labels...)
+}

vendor/google.golang.org/grpc/internal/stats/stats.go

@@ -0,0 +1,70 @@
+/*
+ *
+ * Copyright 2025 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package stats
+
+import (
+	"context"
+
+	"google.golang.org/grpc/stats"
+)
+
+type combinedHandler struct {
+	handlers []stats.Handler
+}
+
+// NewCombinedHandler combines multiple stats.Handlers into a single handler.
+//
+// It returns nil if no handlers are provided. If only one handler is
+// provided, it is returned directly without wrapping.
+func NewCombinedHandler(handlers ...stats.Handler) stats.Handler {
+	switch len(handlers) {
+	case 0:
+		return nil
+	case 1:
+		return handlers[0]
+	default:
+		return &combinedHandler{handlers: handlers}
+	}
+}
+
+func (ch *combinedHandler) TagRPC(ctx context.Context, info *stats.RPCTagInfo) context.Context {
+	for _, h := range ch.handlers {
+		ctx = h.TagRPC(ctx, info)
+	}
+	return ctx
+}
+
+func (ch *combinedHandler) HandleRPC(ctx context.Context, stats stats.RPCStats) {
+	for _, h := range ch.handlers {
+		h.HandleRPC(ctx, stats)
+	}
+}
+
+func (ch *combinedHandler) TagConn(ctx context.Context, info *stats.ConnTagInfo) context.Context {
+	for _, h := range ch.handlers {
+		ctx = h.TagConn(ctx, info)
+	}
+	return ctx
+}
+
+func (ch *combinedHandler) HandleConn(ctx context.Context, stats stats.ConnStats) {
+	for _, h := range ch.handlers {
+		h.HandleConn(ctx, stats)
+	}
+}