feat: add authoritative worker runtime capacity

api/proto/controlplane/v1/controlplane.proto

@@ -182,6 +182,7 @@ message ReportRuntimeRequest {
   uint64 ownership_epoch = 4;
   repeated ProxyRuntime counters = 5;
   google.protobuf.Timestamp observed_at = 6;
+  uint64 report_sequence = 7;
 }
 
 message ProxyRuntime {

internal/adapters/redisactivity/adapter.go

@@ -19,11 +19,13 @@ var (
 )
 
 type Options struct {
-	Namespace        string
+	Namespace          string
-	Credentials      credentials.Store
+	Credentials        credentials.Store
-	OperationTTL     time.Duration
+	OperationTTL       time.Duration
-	MaxCandidateScan int
+	MaxCandidateScan   int
-	CleanupLimit     int
+	MaxRuntimeCounters int
+	MaxInventoryScan   int
+	CleanupLimit       int
 }
 
 type Adapter struct {
@@ -35,9 +37,16 @@ type Adapter struct {
 
 func New(client redis.Scripter, options Options) (*Adapter, error) {
 	options.Namespace = strings.TrimSpace(options.Namespace)
+	if options.MaxRuntimeCounters == 0 {
+		options.MaxRuntimeCounters = options.MaxCandidateScan
+	}
+	if options.MaxInventoryScan == 0 {
+		options.MaxInventoryScan = options.MaxCandidateScan
+	}
 	if nilInterface(client) || nilInterface(options.Credentials) ||
 		!namespacePattern.MatchString(options.Namespace) || options.OperationTTL <= 0 ||
-		options.MaxCandidateScan <= 0 || options.CleanupLimit <= 0 {
+		options.MaxCandidateScan <= 0 || options.MaxRuntimeCounters <= 0 ||
+		options.MaxInventoryScan <= 0 || options.CleanupLimit <= 0 {
 		return nil, ErrInvalidOptions
 	}
 	return &Adapter{

internal/adapters/redisactivity/adapter_test.go

@@ -58,6 +58,8 @@ func TestNewRejectsInvalidDependenciesAndOptions(t *testing.T) {
 		{name: "colon in namespace", client: client, options: withNamespace(valid, "tenant:other")},
 		{name: "zero operation ttl", client: client, options: withOperationTTL(valid, 0)},
 		{name: "zero candidate scan", client: client, options: withMaxCandidateScan(valid, 0)},
+		{name: "negative runtime counters", client: client, options: withMaxRuntimeCounters(valid, -1)},
+		{name: "negative inventory scan", client: client, options: withMaxInventoryScan(valid, -1)},
 		{name: "negative cleanup limit", client: client, options: withCleanupLimit(valid, -1)},
 	}
 	for _, tt := range tests {
@@ -93,7 +95,9 @@ func TestNewBuildsClusterSafeKeyspaceAndHashesDynamicTokens(t *testing.T) {
 		adapter.keys.records, adapter.keys.unique, adapter.keys.idkeys,
 		adapter.keys.expiry, adapter.keys.available, adapter.keys.owners,
 		adapter.keys.ownerExpiry, adapter.keys.epoch, adapter.keys.inventory,
-		adapter.keys.stateInventory,
+		adapter.keys.stateInventory, adapter.keys.workerSessions,
+		adapter.keys.workerSessionExpiry, adapter.keys.workerRuntime,
+		adapter.keys.workerRuntimeExpiry,
 	}
 	for _, key := range staticKeys {
 		if strings.Count(key, "{activity}") != 1 || strings.Count(key, "{") != 1 || strings.Count(key, "}") != 1 {
@@ -109,6 +113,7 @@ func TestNewBuildsClusterSafeKeyspaceAndHashesDynamicTokens(t *testing.T) {
 		adapter.keys.region(raw),
 		adapter.keys.carrier(raw),
 		adapter.keys.upstream(raw),
+		adapter.keys.owned(raw),
 	}
 	for _, key := range dynamicKeys {
 		if strings.Contains(key, raw) || strings.Count(key, "{activity}") != 1 || strings.Count(key, "{") != 1 {
@@ -161,6 +166,7 @@ func TestProxyRecordCodecIsDeterministicStrictAndRedacted(t *testing.T) {
 		UsableUntilMS: 58_000, LastCheckedAtMS: 2_000, LastSuccessAtMS: 2_000,
 		LatencyNS: int64(25 * time.Millisecond), MaxConcurrency: 8,
 		State: string(proxyDomain.StateAvailable), Tags: map[string]string{"region": "cn", "carrier": "ct"},
+		OwnerIndexKey: "pp:{activity}:test:owned:index",
 	}
 	first, err := encodeProxyRecord(record)
 	if err != nil {
@@ -260,6 +266,16 @@ func withMaxCandidateScan(options Options, limit int) Options {
 	return options
 }
 
+func withMaxRuntimeCounters(options Options, limit int) Options {
+	options.MaxRuntimeCounters = limit
+	return options
+}
+
+func withMaxInventoryScan(options Options, limit int) Options {
+	options.MaxInventoryScan = limit
+	return options
+}
+
 func withCleanupLimit(options Options, limit int) Options {
 	options.CleanupLimit = limit
 	return options

internal/adapters/redisactivity/capacity.go

@@ -0,0 +1,45 @@
+package redisactivity
+
+import (
+	"context"
+	"time"
+
+	controllerPool "proxy-pool/internal/controller/pool"
+	"proxy-pool/internal/domain/activitypool"
+)
+
+var _ controllerPool.InventoryReader = (*Adapter)(nil)
+
+func (a *Adapter) ReadInventory(
+	ctx context.Context,
+	upstreamID string,
+	safetyMargin time.Duration,
+) (controllerPool.InventorySnapshot, error) {
+	if ctx == nil || a == nil || !runtimeClean(upstreamID) || safetyMargin < 0 {
+		return controllerPool.InventorySnapshot{}, activitypool.ErrInvalidInventory
+	}
+	if err := ctx.Err(); err != nil {
+		return controllerPool.InventorySnapshot{}, err
+	}
+	result, err := runScript(ctx, a.client, capacityScript, []string{
+		a.keys.records, a.keys.inventory, a.keys.upstream(upstreamID), a.keys.owned(upstreamID), a.keys.owners,
+		a.keys.workerSessions, a.keys.workerSessionExpiry,
+		a.keys.workerRuntime, a.keys.workerRuntimeExpiry,
+	}, upstreamID, durationMillis(safetyMargin), a.options.MaxInventoryScan, a.options.CleanupLimit)
+	if err != nil {
+		return controllerPool.InventorySnapshot{}, err
+	}
+	var reply capacityScriptReply
+	if err := decodeScriptResult(result, &reply); err != nil {
+		return controllerPool.InventorySnapshot{}, err
+	}
+	if reply.Status == scriptInvalid {
+		return controllerPool.InventorySnapshot{}, activitypool.ErrInvalidInventory
+	}
+	if reply.Status != scriptOK || reply.Managed < 0 || reply.AvailableSlots < 0 {
+		return controllerPool.InventorySnapshot{}, invalidScriptReply("capacity inventory is unavailable")
+	}
+	return controllerPool.InventorySnapshot{
+		Managed: reply.Managed, AvailableSlots: reply.AvailableSlots,
+	}, nil
+}

internal/adapters/redisactivity/capacity_integration_test.go

@@ -0,0 +1,105 @@
+//go:build integration
+
+package redisactivity
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	controllerPool "proxy-pool/internal/controller/pool"
+	"proxy-pool/internal/domain/workerruntime"
+)
+
+func TestRedisCapacityInventoryCombinesProxyAndWorkerRuntime(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	now := redisTestNow()
+	unowned := testProxy("proxy-unowned", "192.0.2.10")
+	unowned.MaxConcurrency = 10
+	owned := testProxy("proxy-owned", "192.0.2.11")
+	owned.MaxConcurrency = 10
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute, unowned)
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute, owned)
+	assignment, err := fixture.Adapter.Assign(context.Background(), now.Add(2*time.Second),
+		"proxy-owned", "worker-a", time.Minute)
+	if err != nil {
+		t.Fatalf("Assign(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceSession(context.Background(), workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: "session-a",
+		AckedSnapshotVersion: 1, AckedOwnershipEpoch: assignment.Epoch,
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), workerruntime.Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 1, OwnershipEpoch: assignment.Epoch, ObservedAt: now,
+		Counters: []workerruntime.Counter{{ProxyID: "proxy-owned", Active: 3, Reserved: 2}},
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(): %v", err)
+	}
+
+	inventory, err := fixture.Adapter.ReadInventory(context.Background(), "provider-a", 0)
+	if err != nil || inventory.Managed != 2 || inventory.AvailableSlots != 15 {
+		t.Fatalf("ReadInventory() = %+v, %v; want managed=2 slots=15", inventory, err)
+	}
+	if _, ok := any(fixture.Adapter).(controllerPool.InventoryReader); !ok {
+		t.Fatal("Adapter does not implement pool.InventoryReader")
+	}
+	inventory, err = fixture.Adapter.ReadInventory(context.Background(), "provider-a", 2*time.Hour)
+	if err != nil || inventory.Managed != 2 || inventory.AvailableSlots != 0 {
+		t.Fatalf("ReadInventory(safety margin) = %+v, %v", inventory, err)
+	}
+	fixture.Adapter.options.MaxInventoryScan = 1
+	if _, err := fixture.Adapter.ReadInventory(context.Background(), "provider-a", 0); err == nil {
+		t.Fatal("ReadInventory(over scan limit) error = nil")
+	}
+}
+
+func TestRedisCapacityInventoryFailsClosedForExpiredRuntime(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	now := redisTestNow()
+	owned := testProxy("proxy-owned", "192.0.2.11")
+	owned.MaxConcurrency = 10
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute, owned)
+	assignment, err := fixture.Adapter.Assign(context.Background(), now.Add(2*time.Second),
+		"proxy-owned", "worker-a", time.Minute)
+	if err != nil {
+		t.Fatalf("Assign(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceSession(context.Background(), workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: "session-a",
+		AckedSnapshotVersion: 1, AckedOwnershipEpoch: assignment.Epoch,
+	}, 100*time.Millisecond); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), workerruntime.Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 1, OwnershipEpoch: assignment.Epoch, ObservedAt: now,
+	}, 100*time.Millisecond); err != nil {
+		t.Fatalf("ReplaceRuntime(): %v", err)
+	}
+	time.Sleep(150 * time.Millisecond)
+	inventory, err := fixture.Adapter.ReadInventory(context.Background(), "provider-a", 0)
+	if err != nil || inventory.Managed != 1 || inventory.AvailableSlots != 0 {
+		t.Fatalf("ReadInventory(expired runtime) = %+v, %v", inventory, err)
+	}
+}
+
+func TestRedisCapacityInventoryScanIsIsolatedPerUpstream(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	fixture.Adapter.options.MaxInventoryScan = 1
+	now := redisTestNow()
+	target := testProxy("proxy-target", "192.0.2.10")
+	target.MaxConcurrency = 4
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute, target)
+	seedRedisAvailable(t, fixture.Adapter, "provider-b", now, now.Add(time.Second), 2*time.Minute,
+		testProxy("proxy-other-1", "192.0.2.11"))
+	seedRedisAvailable(t, fixture.Adapter, "provider-b", now, now.Add(2*time.Second), 2*time.Minute,
+		testProxy("proxy-other-2", "192.0.2.12"))
+
+	inventory, err := fixture.Adapter.ReadInventory(context.Background(), "provider-a", 0)
+	if err != nil || inventory.Managed != 1 || inventory.AvailableSlots != 4 {
+		t.Fatalf("ReadInventory(provider-a) = %+v, %v; want isolated managed=1 slots=4", inventory, err)
+	}
+}

internal/adapters/redisactivity/codec.go

@@ -37,6 +37,7 @@ type proxyRecord struct {
 	State             string            `json:"state"`
 	Tags              map[string]string `json:"tags,omitempty"`
 	OwnerWorkerID     string            `json:"ownerWorkerId,omitempty"`
+	OwnerIndexKey     string            `json:"ownerIndexKey"`
 	IndexKeys         []string          `json:"indexKeys,omitempty"`
 }
 
@@ -203,7 +204,8 @@ func validateProxyRecord(record proxyRecord) error {
 		record.CreatedAtMS <= 0 || record.ExpiresAtMS <= 0 || record.UsableUntilMS <= 0 ||
 		record.UsableUntilMS > record.ExpiresAtMS || record.LastCheckedAtMS < 0 ||
 		record.LastSuccessAtMS < 0 || record.LatencyNS < 0 || record.MaxConcurrency < 0 ||
-		!validScheme(record.Scheme) || !validProxyState(record.State) {
+		!validScheme(record.Scheme) || !validProxyState(record.State) ||
+		record.OwnerIndexKey == "" || !strings.Contains(record.OwnerIndexKey, "{activity}") {
 		return ErrInvalidRecord
 	}
 	for _, key := range record.IndexKeys {

internal/adapters/redisactivity/keys.go

@@ -9,33 +9,41 @@ import (
 const redisKeyPrefix = "pp:{activity}:"
 
 type keyspace struct {
-	prefix         string
+	prefix              string
-	records        string
+	records             string
-	unique         string
+	unique              string
-	idkeys         string
+	idkeys              string
-	expiry         string
+	expiry              string
-	available      string
+	available           string
-	owners         string
+	owners              string
-	ownerExpiry    string
+	ownerExpiry         string
-	epoch          string
+	epoch               string
-	inventory      string
+	inventory           string
-	stateInventory string
+	stateInventory      string
+	workerSessions      string
+	workerSessionExpiry string
+	workerRuntime       string
+	workerRuntimeExpiry string
 }
 
 func newKeyspace(namespace string) keyspace {
 	prefix := redisKeyPrefix + namespace
 	return keyspace{
-		prefix:         prefix,
+		prefix:              prefix,
-		records:        prefix + ":records",
+		records:             prefix + ":records",
-		unique:         prefix + ":unique",
+		unique:              prefix + ":unique",
-		idkeys:         prefix + ":idkeys",
+		idkeys:              prefix + ":idkeys",
-		expiry:         prefix + ":expiry",
+		expiry:              prefix + ":expiry",
-		available:      prefix + ":available",
+		available:           prefix + ":available",
-		owners:         prefix + ":owners",
+		owners:              prefix + ":owners",
-		ownerExpiry:    prefix + ":owner-expiry",
+		ownerExpiry:         prefix + ":owner-expiry",
-		epoch:          prefix + ":epoch",
+		epoch:               prefix + ":epoch",
-		inventory:      prefix + ":inventory",
+		inventory:           prefix + ":inventory",
-		stateInventory: prefix + ":state-inventory",
+		stateInventory:      prefix + ":state-inventory",
+		workerSessions:      prefix + ":worker-sessions",
+		workerSessionExpiry: prefix + ":worker-session-expiry",
+		workerRuntime:       prefix + ":worker-runtime",
+		workerRuntimeExpiry: prefix + ":worker-runtime-expiry",
 	}
 }
 
@@ -67,6 +75,10 @@ func (keys keyspace) upstream(value string) string {
 	return keys.facet("upstream", value)
 }
 
+func (keys keyspace) owned(value string) string {
+	return keys.facet("owned", value)
+}
+
 func (keys keyspace) facet(name, value string) string {
 	return keys.prefix + ":" + name + ":" + digestToken(value)
 }

internal/adapters/redisactivity/runtime.go

@@ -0,0 +1,248 @@
+package redisactivity
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"proxy-pool/internal/domain/workerruntime"
+)
+
+const runtimeWireVersion = 1
+
+const (
+	runtimeReplaceSession = "replace_session"
+	runtimeReplaceReport  = "replace_report"
+	runtimeRead           = "read"
+)
+
+type runtimeSessionWire struct {
+	Version              int    `json:"version"`
+	WorkerID             string `json:"workerId"`
+	InstanceID           string `json:"instanceId"`
+	SessionID            string `json:"sessionId"`
+	AckedSnapshotVersion string `json:"ackedSnapshotVersion"`
+	AckedOwnershipEpoch  string `json:"ackedOwnershipEpoch"`
+}
+
+type runtimeCounterWire struct {
+	ProxyID  string `json:"proxyId"`
+	Active   int64  `json:"active"`
+	Reserved int64  `json:"reserved"`
+	Draining bool   `json:"draining"`
+}
+
+type runtimeReportWire struct {
+	Version         int                  `json:"version"`
+	WorkerID        string               `json:"workerId"`
+	SessionID       string               `json:"sessionId"`
+	Sequence        string               `json:"sequence"`
+	SnapshotVersion string               `json:"snapshotVersion"`
+	OwnershipEpoch  string               `json:"ownershipEpoch"`
+	ObservedAtMS    int64                `json:"observedAtMs"`
+	Counters        []runtimeCounterWire `json:"counters"`
+}
+
+type runtimeOwnedProxyWire struct {
+	ProxyID        string `json:"proxyId"`
+	WorkerID       string `json:"workerId"`
+	OwnershipEpoch string `json:"ownershipEpoch"`
+}
+
+type runtimeSnapshotWire struct {
+	ProxyID  string `json:"proxyId"`
+	Active   int64  `json:"active"`
+	Reserved int64  `json:"reserved"`
+	Draining bool   `json:"draining"`
+	Fresh    bool   `json:"fresh"`
+}
+
+var (
+	_ workerruntime.SessionWriter = (*Adapter)(nil)
+	_ workerruntime.ReportWriter  = (*Adapter)(nil)
+	_ workerruntime.RuntimeReader = (*Adapter)(nil)
+)
+
+func (a *Adapter) ReplaceSession(ctx context.Context, session workerruntime.Session, ttl time.Duration) error {
+	if err := validateRuntimeCall(ctx, a); err != nil {
+		return err
+	}
+	if !runtimeClean(session.WorkerID) || !runtimeClean(session.InstanceID) || !runtimeClean(session.SessionID) ||
+		session.AckedSnapshotVersion == 0 || session.AckedOwnershipEpoch == 0 || ttl <= 0 {
+		return workerruntime.ErrInvalidSession
+	}
+	payload, err := json.Marshal(runtimeSessionWire{
+		Version: runtimeWireVersion, WorkerID: session.WorkerID,
+		InstanceID: session.InstanceID, SessionID: session.SessionID,
+		AckedSnapshotVersion: strconv.FormatUint(session.AckedSnapshotVersion, 10),
+		AckedOwnershipEpoch:  strconv.FormatUint(session.AckedOwnershipEpoch, 10),
+	})
+	if err != nil {
+		return workerruntime.ErrInvalidSession
+	}
+	reply, err := a.runRuntime(ctx, runtimeReplaceSession, durationMillis(ttl), payload, "")
+	if err != nil {
+		return err
+	}
+	switch reply.Status {
+	case scriptOK:
+		return nil
+	case scriptInvalid:
+		return workerruntime.ErrInvalidSession
+	case scriptStale:
+		return workerruntime.ErrStaleSession
+	default:
+		return invalidScriptReply("unexpected worker session reply")
+	}
+}
+
+func (a *Adapter) ReplaceRuntime(ctx context.Context, report workerruntime.Report, ttl time.Duration) error {
+	if err := validateRuntimeCall(ctx, a); err != nil {
+		return err
+	}
+	payload, digest, err := a.encodeRuntimeReport(report, ttl)
+	if err != nil {
+		return err
+	}
+	reply, err := a.runRuntime(ctx, runtimeReplaceReport, durationMillis(ttl), payload, digest)
+	if err != nil {
+		return err
+	}
+	switch reply.Status {
+	case scriptOK:
+		return nil
+	case scriptInvalid:
+		return workerruntime.ErrInvalidReport
+	case scriptStale:
+		return workerruntime.ErrStaleReport
+	case scriptConflict:
+		return workerruntime.ErrConflictingReport
+	case scriptUnavailable:
+		return workerruntime.ErrStaleSession
+	default:
+		return invalidScriptReply("unexpected worker runtime reply")
+	}
+}
+
+func (a *Adapter) ReadRuntime(ctx context.Context, proxies []workerruntime.OwnedProxy) ([]workerruntime.Snapshot, error) {
+	if err := validateRuntimeCall(ctx, a); err != nil {
+		return nil, err
+	}
+	if len(proxies) > a.options.MaxRuntimeCounters {
+		return nil, workerruntime.ErrInvalidQuery
+	}
+	wires := make([]runtimeOwnedProxyWire, len(proxies))
+	seen := make(map[string]struct{}, len(proxies))
+	for index, proxy := range proxies {
+		if !runtimeClean(proxy.ProxyID) || !runtimeClean(proxy.WorkerID) || proxy.OwnershipEpoch == 0 {
+			return nil, workerruntime.ErrInvalidQuery
+		}
+		key := proxy.WorkerID + "\x00" + proxy.ProxyID
+		if _, exists := seen[key]; exists {
+			return nil, workerruntime.ErrInvalidQuery
+		}
+		seen[key] = struct{}{}
+		wires[index] = runtimeOwnedProxyWire{
+			ProxyID: proxy.ProxyID, WorkerID: proxy.WorkerID,
+			OwnershipEpoch: strconv.FormatUint(proxy.OwnershipEpoch, 10),
+		}
+	}
+	payload, err := json.Marshal(wires)
+	if err != nil {
+		return nil, workerruntime.ErrInvalidQuery
+	}
+	reply, err := a.runRuntime(ctx, runtimeRead, 0, payload, "")
+	if err != nil {
+		return nil, err
+	}
+	if reply.Status == scriptInvalid {
+		return nil, workerruntime.ErrInvalidQuery
+	}
+	if reply.Status != scriptOK || len(reply.Snapshots) != len(proxies) {
+		return nil, invalidScriptReply("unexpected worker runtime read reply")
+	}
+	result := make([]workerruntime.Snapshot, len(reply.Snapshots))
+	for index, snapshot := range reply.Snapshots {
+		if snapshot.ProxyID != proxies[index].ProxyID || snapshot.Active < 0 || snapshot.Reserved < 0 {
+			return nil, invalidScriptReply("invalid worker runtime snapshot")
+		}
+		result[index] = workerruntime.Snapshot{
+			ProxyID: snapshot.ProxyID, Active: snapshot.Active, Reserved: snapshot.Reserved,
+			Draining: snapshot.Draining, Fresh: snapshot.Fresh,
+		}
+	}
+	return result, nil
+}
+
+func (a *Adapter) encodeRuntimeReport(report workerruntime.Report, ttl time.Duration) ([]byte, string, error) {
+	if ttl <= 0 || !runtimeClean(report.WorkerID) || !runtimeClean(report.SessionID) ||
+		report.Sequence == 0 || report.SnapshotVersion == 0 || report.OwnershipEpoch == 0 || report.ObservedAt.IsZero() ||
+		len(report.Counters) > a.options.MaxRuntimeCounters {
+		return nil, "", workerruntime.ErrInvalidReport
+	}
+	counters := append([]workerruntime.Counter(nil), report.Counters...)
+	sort.Slice(counters, func(left, right int) bool { return counters[left].ProxyID < counters[right].ProxyID })
+	wires := make([]runtimeCounterWire, len(counters))
+	for index, counter := range counters {
+		if !runtimeClean(counter.ProxyID) || counter.Active < 0 || counter.Reserved < 0 ||
+			(index > 0 && counters[index-1].ProxyID == counter.ProxyID) {
+			return nil, "", workerruntime.ErrInvalidReport
+		}
+		wires[index] = runtimeCounterWire{
+			ProxyID: counter.ProxyID, Active: counter.Active,
+			Reserved: counter.Reserved, Draining: counter.Draining,
+		}
+	}
+	payload, err := json.Marshal(runtimeReportWire{
+		Version: runtimeWireVersion, WorkerID: report.WorkerID, SessionID: report.SessionID,
+		Sequence:        strconv.FormatUint(report.Sequence, 10),
+		SnapshotVersion: strconv.FormatUint(report.SnapshotVersion, 10),
+		OwnershipEpoch:  strconv.FormatUint(report.OwnershipEpoch, 10),
+		ObservedAtMS:    report.ObservedAt.UTC().UnixMilli(), Counters: wires,
+	})
+	if err != nil {
+		return nil, "", workerruntime.ErrInvalidReport
+	}
+	digest := sha256.Sum256(payload)
+	return payload, hex.EncodeToString(digest[:]), nil
+}
+
+func (a *Adapter) runRuntime(
+	ctx context.Context,
+	operation string,
+	ttlMS int64,
+	payload []byte,
+	digest string,
+) (runtimeScriptReply, error) {
+	result, err := runScript(ctx, a.client, runtimeScript, []string{
+		a.keys.workerSessions, a.keys.workerSessionExpiry,
+		a.keys.workerRuntime, a.keys.workerRuntimeExpiry, a.keys.owners,
+	}, operation, ttlMS, a.options.CleanupLimit, string(payload), digest)
+	if err != nil {
+		return runtimeScriptReply{}, err
+	}
+	var reply runtimeScriptReply
+	if err := decodeScriptResult(result, &reply); err != nil {
+		return runtimeScriptReply{}, err
+	}
+	return reply, nil
+}
+
+func validateRuntimeCall(ctx context.Context, adapter *Adapter) error {
+	if ctx == nil || adapter == nil {
+		return workerruntime.ErrInvalidStore
+	}
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func runtimeClean(value string) bool {
+	return value != "" && strings.TrimSpace(value) == value
+}

internal/adapters/redisactivity/runtime_integration_test.go

@@ -0,0 +1,147 @@
+//go:build integration
+
+package redisactivity
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+
+	"proxy-pool/internal/domain/workerruntime"
+)
+
+func TestRedisWorkerRuntimeReplacesSparseCountersAndFencesReports(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	now := redisTestNow()
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute,
+		testProxy("proxy-a", "192.0.2.10"))
+	assignment, err := fixture.Adapter.Assign(context.Background(), now.Add(2*time.Second),
+		"proxy-a", "worker-a", time.Minute)
+	if err != nil {
+		t.Fatalf("Assign(): %v", err)
+	}
+	session := workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: "session-a",
+		AckedSnapshotVersion: 3, AckedOwnershipEpoch: assignment.Epoch,
+	}
+	if err := fixture.Adapter.ReplaceSession(context.Background(), session, time.Minute); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+	report := workerruntime.Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 2,
+		SnapshotVersion: 3, OwnershipEpoch: assignment.Epoch, ObservedAt: now,
+		Counters: []workerruntime.Counter{{ProxyID: "proxy-a", Active: 2, Reserved: 1}},
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(first): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(replay): %v", err)
+	}
+	conflict := report
+	conflict.Counters = []workerruntime.Counter{{ProxyID: "proxy-a", Active: 3}}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), conflict, time.Minute); !errors.Is(err, workerruntime.ErrConflictingReport) {
+		t.Fatalf("ReplaceRuntime(conflict) error = %v", err)
+	}
+	stale := report
+	stale.Sequence = 1
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), stale, time.Minute); !errors.Is(err, workerruntime.ErrStaleReport) {
+		t.Fatalf("ReplaceRuntime(stale) error = %v", err)
+	}
+
+	query := []workerruntime.OwnedProxy{{
+		ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: assignment.Epoch,
+	}}
+	got, err := fixture.Adapter.ReadRuntime(context.Background(), query)
+	if err != nil || len(got) != 1 || got[0] != (workerruntime.Snapshot{
+		ProxyID: "proxy-a", Active: 2, Reserved: 1, Fresh: true,
+	}) {
+		t.Fatalf("ReadRuntime(first) = %+v, %v", got, err)
+	}
+	report.Sequence = 3
+	report.Counters = nil
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(empty): %v", err)
+	}
+	got, err = fixture.Adapter.ReadRuntime(context.Background(), query)
+	if err != nil || len(got) != 1 || got[0] != (workerruntime.Snapshot{ProxyID: "proxy-a", Fresh: true}) {
+		t.Fatalf("ReadRuntime(empty) = %+v, %v", got, err)
+	}
+
+	if err := fixture.Adapter.ReplaceSession(context.Background(), workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-b", SessionID: "session-b",
+		AckedSnapshotVersion: 4, AckedOwnershipEpoch: assignment.Epoch + 1,
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceSession(new): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), report, time.Minute); !errors.Is(err, workerruntime.ErrStaleSession) {
+		t.Fatalf("ReplaceRuntime(old session) error = %v", err)
+	}
+}
+
+func TestRedisWorkerRuntimeExpiresFailClosed(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	now := redisTestNow()
+	seedRedisAvailable(t, fixture.Adapter, "provider-a", now, now.Add(time.Second), 2*time.Minute,
+		testProxy("proxy-a", "192.0.2.10"))
+	assignment, err := fixture.Adapter.Assign(context.Background(), now.Add(2*time.Second),
+		"proxy-a", "worker-a", time.Minute)
+	if err != nil {
+		t.Fatalf("Assign(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceSession(context.Background(), workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: "session-a",
+		AckedSnapshotVersion: 1, AckedOwnershipEpoch: assignment.Epoch,
+	}, 100*time.Millisecond); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+	if err := fixture.Adapter.ReplaceRuntime(context.Background(), workerruntime.Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 1, OwnershipEpoch: assignment.Epoch, ObservedAt: now,
+	}, 100*time.Millisecond); err != nil {
+		t.Fatalf("ReplaceRuntime(): %v", err)
+	}
+	time.Sleep(150 * time.Millisecond)
+	got, err := fixture.Adapter.ReadRuntime(context.Background(), []workerruntime.OwnedProxy{{
+		ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: assignment.Epoch,
+	}})
+	if err != nil || len(got) != 1 || got[0].Fresh {
+		t.Fatalf("ReadRuntime(expired) = %+v, %v", got, err)
+	}
+}
+
+func TestRedisWorkerRuntimeRejectsEmptyReportBeyondAcknowledgedSnapshot(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	now := redisTestNow()
+	if err := fixture.Adapter.ReplaceSession(context.Background(), workerruntime.Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: "session-a",
+		AckedSnapshotVersion: 3, AckedOwnershipEpoch: 9,
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+	for name, report := range map[string]workerruntime.Report{
+		"version": {
+			WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+			SnapshotVersion: 4, OwnershipEpoch: 9, ObservedAt: now,
+		},
+		"epoch": {
+			WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+			SnapshotVersion: 3, OwnershipEpoch: 10, ObservedAt: now,
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			if err := fixture.Adapter.ReplaceRuntime(context.Background(), report, time.Minute); !errors.Is(err, workerruntime.ErrStaleReport) {
+				t.Fatalf("ReplaceRuntime() error = %v, want ErrStaleReport", err)
+			}
+		})
+	}
+}
+
+func TestRedisWorkerRuntimeAcceptsEmptyRead(t *testing.T) {
+	fixture := newRedisTestFixture(t)
+	got, err := fixture.Adapter.ReadRuntime(context.Background(), nil)
+	if err != nil || got == nil || len(got) != 0 {
+		t.Fatalf("ReadRuntime(empty) = %#v, %v", got, err)
+	}
+}

internal/adapters/redisactivity/scripts.go

@@ -74,6 +74,17 @@ type statusScriptInventory struct {
 	Extracted  int64  `json:"extracted"`
 }
 
+type runtimeScriptReply struct {
+	Status    scriptStatus          `json:"status"`
+	Snapshots []runtimeSnapshotWire `json:"snapshots"`
+}
+
+type capacityScriptReply struct {
+	Status         scriptStatus `json:"status"`
+	Managed        int          `json:"managed"`
+	AvailableSlots int64        `json:"availableSlots,string"`
+}
+
 //go:embed scripts/upsert.lua
 var upsertSource string
 
@@ -92,6 +103,12 @@ var sweepSource string
 //go:embed scripts/status.lua
 var statusSource string
 
+//go:embed scripts/runtime.lua
+var runtimeSource string
+
+//go:embed scripts/capacity.lua
+var capacitySource string
+
 var (
 	upsertScript    = redis.NewScript(upsertSource)
 	healthScript    = redis.NewScript(healthSource)
@@ -99,6 +116,8 @@ var (
 	ownershipScript = redis.NewScript(ownershipSource)
 	sweepScript     = redis.NewScript(sweepSource)
 	statusScript    = redis.NewScript(statusSource)
+	runtimeScript   = redis.NewScript(runtimeSource)
+	capacityScript  = redis.NewScript(capacitySource)
 )
 
 func runScript(ctx context.Context, client redis.Scripter, script *redis.Script, keys []string, args ...any) (any, error) {

internal/adapters/redisactivity/scripts/capacity.lua

@@ -0,0 +1,177 @@
+local records_key = KEYS[1]
+local inventory_key = KEYS[2]
+local available_upstream_key = KEYS[3]
+local owned_upstream_key = KEYS[4]
+local owners_key = KEYS[5]
+local sessions_key = KEYS[6]
+local session_expiry_key = KEYS[7]
+local runtime_key = KEYS[8]
+local runtime_expiry_key = KEYS[9]
+
+local upstream_id = ARGV[1]
+local safety_margin_ms = tonumber(ARGV[2])
+local scan_limit = tonumber(ARGV[3])
+local cleanup_limit = tonumber(ARGV[4])
+
+local function reply(status, managed, available_slots)
+    return cjson.encode({
+        status = status,
+        managed = managed or 0,
+        availableSlots = tostring(available_slots or 0)
+    })
+end
+
+local function now_ms()
+    local value = redis.call('TIME')
+    return tonumber(value[1]) * 1000 + math.floor(tonumber(value[2]) / 1000)
+end
+
+local function decode_table(value)
+    if not value then
+        return nil
+    end
+    local ok, decoded = pcall(cjson.decode, value)
+    if not ok or type(decoded) ~= 'table' then
+        return nil
+    end
+    return decoded
+end
+
+local function valid_uint(value)
+    return type(value) == 'string' and string.match(value, '^[0-9]+$') and
+        value ~= '0' and (string.len(value) == 1 or string.sub(value, 1, 1) ~= '0')
+end
+
+local function compare_uint(left, right)
+    if string.len(left) ~= string.len(right) then
+        return string.len(left) < string.len(right) and -1 or 1
+    end
+    if left == right then
+        return 0
+    end
+    return left < right and -1 or 1
+end
+
+local function cleanup(now)
+    local expired_sessions = redis.call('ZRANGEBYSCORE', session_expiry_key, '-inf', now, 'LIMIT', 0, cleanup_limit)
+    for _, worker_id in ipairs(expired_sessions) do
+        redis.call('HDEL', sessions_key, worker_id)
+        redis.call('HDEL', runtime_key, worker_id)
+        redis.call('ZREM', session_expiry_key, worker_id)
+        redis.call('ZREM', runtime_expiry_key, worker_id)
+    end
+    local expired_reports = redis.call('ZRANGEBYSCORE', runtime_expiry_key, '-inf', now, 'LIMIT', 0, cleanup_limit)
+    for _, worker_id in ipairs(expired_reports) do
+        redis.call('HDEL', runtime_key, worker_id)
+        redis.call('ZREM', runtime_expiry_key, worker_id)
+    end
+end
+
+if type(upstream_id) ~= 'string' or upstream_id == '' or not safety_margin_ms or safety_margin_ms < 0 or
+    not scan_limit or scan_limit <= 0 or not cleanup_limit or cleanup_limit <= 0 then
+    return reply('invalid', 0, 0)
+end
+
+local now = now_ms()
+cleanup(now)
+local threshold = now + safety_margin_ms
+local available_ids = redis.call('ZRANGEBYSCORE', available_upstream_key, '(' .. threshold, '+inf',
+    'LIMIT', 0, scan_limit + 1)
+if #available_ids > scan_limit then
+    return reply('unavailable', 0, 0)
+end
+local remaining = scan_limit - #available_ids
+local owned_ids = redis.call('ZRANGEBYSCORE', owned_upstream_key, '(' .. threshold, '+inf',
+    'LIMIT', 0, remaining + 1)
+if #owned_ids > remaining then
+    return reply('unavailable', 0, 0)
+end
+
+local managed = tonumber(redis.call('HGET', inventory_key, upstream_id) or '0')
+if not managed or managed < 0 or managed ~= math.floor(managed) then
+    return reply('unavailable', 0, 0)
+end
+local available_slots = 0
+local worker_cache = {}
+local seen = {}
+for _, proxy_id in ipairs(available_ids) do
+    seen[proxy_id] = true
+    local record = decode_table(redis.call('HGET', records_key, proxy_id))
+    if not record or type(record.sourceUpstream) ~= 'string' or type(record.state) ~= 'string' or
+        record.sourceUpstream ~= upstream_id or record.state ~= 'AVAILABLE' or
+        type(record.usableUntilMs) ~= 'number' or record.usableUntilMs <= threshold or
+        type(record.maxConcurrency) ~= 'number' or record.maxConcurrency < 0 or
+        record.maxConcurrency ~= math.floor(record.maxConcurrency) or
+        (record.ownerWorkerId and record.ownerWorkerId ~= '') or redis.call('HGET', owners_key, proxy_id) then
+        return reply('unavailable', 0, 0)
+    end
+    available_slots = available_slots + record.maxConcurrency
+end
+
+for _, proxy_id in ipairs(owned_ids) do
+    if seen[proxy_id] then
+        return reply('unavailable', 0, 0)
+    end
+    local record = decode_table(redis.call('HGET', records_key, proxy_id))
+    if not record or record.sourceUpstream ~= upstream_id or record.state ~= 'AVAILABLE' or
+        type(record.usableUntilMs) ~= 'number' or record.usableUntilMs <= threshold or
+        type(record.maxConcurrency) ~= 'number' or record.maxConcurrency < 0 or
+        record.maxConcurrency ~= math.floor(record.maxConcurrency) or
+        type(record.ownerWorkerId) ~= 'string' or record.ownerWorkerId == '' then
+        return reply('unavailable', 0, 0)
+    end
+    local owner_worker_id = record.ownerWorkerId
+    local owner = decode_table(redis.call('HGET', owners_key, proxy_id))
+    if not owner or owner.workerId ~= owner_worker_id or type(owner.epoch) ~= 'number' or
+        type(owner.expiresAtMs) ~= 'number' or owner.expiresAtMs <= now or
+        type(owner.draining) ~= 'boolean' then
+        return reply('unavailable', 0, 0)
+    end
+    local cached = worker_cache[owner_worker_id]
+    if not cached then
+        local session = decode_table(redis.call('HGET', sessions_key, owner_worker_id))
+        local report = decode_table(redis.call('HGET', runtime_key, owner_worker_id))
+        cached = {fresh = false, counters = {}}
+        if session and report and session.workerId == owner_worker_id and
+            report.workerId == owner_worker_id and session.sessionId == report.sessionId and
+            type(session.expiresAtMs) == 'number' and session.expiresAtMs > now and
+            type(report.expiresAtMs) == 'number' and report.expiresAtMs > now and
+            valid_uint(session.ackedSnapshotVersion) and valid_uint(session.ackedOwnershipEpoch) and
+            report.snapshotVersion == session.ackedSnapshotVersion and
+            report.ownershipEpoch == session.ackedOwnershipEpoch then
+            cached.fresh = true
+            cached.ownershipEpoch = report.ownershipEpoch
+            if type(report.counters) == 'table' then
+                for _, counter in pairs(report.counters) do
+                    if type(counter) == 'table' and type(counter.proxyId) == 'string' then
+                        cached.counters[counter.proxyId] = counter
+                    end
+                end
+            end
+        end
+        worker_cache[owner_worker_id] = cached
+    end
+    local owner_epoch = tostring(owner.epoch)
+    if cached.fresh and valid_uint(owner_epoch) and
+        compare_uint(cached.ownershipEpoch, owner_epoch) >= 0 then
+        local counter = cached.counters[proxy_id]
+        local active = 0
+        local reserved = 0
+        local draining = false
+        if counter then
+            active = counter.active
+            reserved = counter.reserved
+            draining = counter.draining
+        end
+        if type(active) == 'number' and type(reserved) == 'number' and active >= 0 and reserved >= 0 and
+            active == math.floor(active) and reserved == math.floor(reserved) and
+            not draining and not owner.draining then
+            local slots = record.maxConcurrency - active - reserved
+            if slots > 0 then
+                available_slots = available_slots + slots
+            end
+        end
+    end
+end
+
+return reply('ok', managed, available_slots)

internal/adapters/redisactivity/scripts/extract.lua

@@ -113,6 +113,12 @@ local function remove_available(proxy_id, record)
     end
 end
 
+local function remove_owned(proxy_id, record)
+    if record and type(record.ownerIndexKey) == 'string' and record.ownerIndexKey ~= '' then
+        redis.call('ZREM', record.ownerIndexKey, proxy_id)
+    end
+end
+
 local function remove_proxy(proxy_id)
     local raw = redis.call('HGET', records_key, proxy_id)
     local record = nil
@@ -120,6 +126,7 @@ local function remove_proxy(proxy_id)
         local decoded
         decoded, record = pcall(cjson.decode, raw)
         remove_available(proxy_id, decoded and record or nil)
+        remove_owned(proxy_id, decoded and record or nil)
         if decoded and type(record) == 'table' and is_managed(record.state) then
             decrement_inventory(record.sourceUpstream)
         end

internal/adapters/redisactivity/scripts/health.lua

@@ -70,12 +70,19 @@ local function remove_available(id, record)
     end
 end
 
+local function remove_owned(id, record)
+    if record and type(record.ownerIndexKey) == 'string' and record.ownerIndexKey ~= '' then
+        redis.call('ZREM', record.ownerIndexKey, id)
+    end
+end
+
 local function remove_proxy(id)
     local raw = redis.call('HGET', records_key, id)
     local record = nil
     if raw then
         record = cjson.decode(raw)
         remove_available(id, record)
+        remove_owned(id, record)
         if is_managed(record.state) then
             decrement_inventory(record.sourceUpstream)
         end
@@ -142,6 +149,9 @@ if not raw then
     return finish({status = 'not_found'})
 end
 local record = cjson.decode(raw)
+if type(record.ownerIndexKey) ~= 'string' or record.ownerIndexKey == '' then
+    return finish({status = 'invalid'})
+end
 if tonumber(record.expiresAtMs) <= checked_at_ms then
     remove_proxy(proxy_id)
     return finish({status = 'not_found'})
@@ -184,11 +194,17 @@ end
 local encoded = cjson.encode(record)
 redis.call('HSET', records_key, proxy_id, encoded)
 local owned = (record.ownerWorkerId and record.ownerWorkerId ~= '') or redis.call('HEXISTS', owners_key, proxy_id) == 1
-if next_state == 'AVAILABLE' and not owned and tonumber(record.usableUntilMs) > checked_at_ms then
+remove_owned(proxy_id, record)
-    redis.call('ZADD', available_key, record.usableUntilMs, proxy_id)
+if next_state == 'AVAILABLE' and tonumber(record.usableUntilMs) > checked_at_ms then
-    for _, index_key in ipairs(record.indexKeys or {}) do
+    if owned then
-        redis.call('ZADD', index_key, record.usableUntilMs, proxy_id)
+        redis.call('ZADD', record.ownerIndexKey, record.usableUntilMs, proxy_id)
-        touch(index_key, tonumber(record.expiresAtMs))
+        touch(record.ownerIndexKey, tonumber(record.expiresAtMs))
+    else
+        redis.call('ZADD', available_key, record.usableUntilMs, proxy_id)
+        for _, index_key in ipairs(record.indexKeys or {}) do
+            redis.call('ZADD', index_key, record.usableUntilMs, proxy_id)
+            touch(index_key, tonumber(record.expiresAtMs))
+        end
     end
 end
 touch(records_key, tonumber(record.expiresAtMs))

internal/adapters/redisactivity/scripts/ownership.lua

@@ -94,6 +94,12 @@ local function remove_available(id, record)
     end
 end
 
+local function remove_owned(id, record)
+    if record and type(record.ownerIndexKey) == 'string' and record.ownerIndexKey ~= '' then
+        redis.call('ZREM', record.ownerIndexKey, id)
+    end
+end
+
 local function add_available(id, record, at_ms)
     local usable_until_ms = record and tonumber(record.usableUntilMs)
     if not usable_until_ms or record.state ~= 'AVAILABLE' or usable_until_ms <= at_ms then
@@ -118,6 +124,7 @@ local function remove_proxy(id)
         local decoded
         decoded, record = pcall(cjson.decode, raw)
         remove_available(id, decoded and record or nil)
+        remove_owned(id, decoded and record or nil)
         if decoded and type(record) == 'table' and is_managed(record.state) then
             decrement_inventory(record.sourceUpstream)
         end
@@ -169,6 +176,7 @@ local function clear_owner(id, assignment, at_ms, restore)
     local raw_record = redis.call('HGET', records_key, id)
     local record = decode_table(raw_record)
     if record and (not assignment or record.ownerWorkerId == assignment.workerId) then
+        remove_owned(id, record)
         record.ownerWorkerId = nil
         redis.call('HSET', records_key, id, cjson.encode(record))
         if restore then
@@ -195,6 +203,7 @@ if operation == 'assign' then
 
     local record = decode_table(redis.call('HGET', records_key, proxy_id))
     if not record or record.state ~= 'AVAILABLE' or
+        type(record.ownerIndexKey) ~= 'string' or record.ownerIndexKey == '' or
         (record.ownerWorkerId and record.ownerWorkerId ~= '') or
         redis.call('HEXISTS', owners_key, proxy_id) == 1 or
         not tonumber(record.usableUntilMs) or tonumber(record.usableUntilMs) <= now_ms then
@@ -223,6 +232,8 @@ if operation == 'assign' then
     record.ownerWorkerId = worker_id
     redis.call('HSET', records_key, proxy_id, cjson.encode(record))
     remove_available(proxy_id, record)
+    redis.call('ZADD', record.ownerIndexKey, record.usableUntilMs, proxy_id)
+    touch(record.ownerIndexKey, tonumber(record.expiresAtMs))
     return finish({status = 'ok', record = encoded})
 end
 
@@ -267,6 +278,8 @@ if operation == 'begin_drain' then
         current.assignmentVersion = tonumber(current.assignmentVersion) + 1
         local encoded = cjson.encode(current)
         redis.call('HSET', owners_key, proxy_id, encoded)
+        local record = decode_table(redis.call('HGET', records_key, proxy_id))
+        remove_owned(proxy_id, record)
         return finish({status = 'ok', record = encoded})
     end
     return finish({status = 'ok', record = cjson.encode(current)})

internal/adapters/redisactivity/scripts/runtime.lua

@@ -0,0 +1,229 @@
+local sessions_key = KEYS[1]
+local session_expiry_key = KEYS[2]
+local runtime_key = KEYS[3]
+local runtime_expiry_key = KEYS[4]
+local owners_key = KEYS[5]
+
+local operation = ARGV[1]
+local ttl_ms = tonumber(ARGV[2])
+local cleanup_limit = tonumber(ARGV[3])
+local payload = ARGV[4]
+local digest = ARGV[5]
+
+local function reply(status, snapshots)
+    if snapshots then
+        return cjson.encode({status = status, snapshots = snapshots})
+    end
+    return '{"status":' .. cjson.encode(status) .. ',"snapshots":[]}'
+end
+
+local function now_ms()
+    local value = redis.call('TIME')
+    return tonumber(value[1]) * 1000 + math.floor(tonumber(value[2]) / 1000)
+end
+
+local function decode_table(value)
+    if not value then
+        return nil
+    end
+    local ok, decoded = pcall(cjson.decode, value)
+    if not ok or type(decoded) ~= 'table' then
+        return nil
+    end
+    return decoded
+end
+
+local function valid_uint(value)
+    return type(value) == 'string' and string.match(value, '^[0-9]+$') and
+        value ~= '0' and (string.len(value) == 1 or string.sub(value, 1, 1) ~= '0')
+end
+
+local function compare_uint(left, right)
+    if string.len(left) ~= string.len(right) then
+        return string.len(left) < string.len(right) and -1 or 1
+    end
+    if left == right then
+        return 0
+    end
+    return left < right and -1 or 1
+end
+
+local function cleanup(now)
+    local expired_sessions = redis.call('ZRANGEBYSCORE', session_expiry_key, '-inf', now, 'LIMIT', 0, cleanup_limit)
+    for _, worker_id in ipairs(expired_sessions) do
+        redis.call('HDEL', sessions_key, worker_id)
+        redis.call('HDEL', runtime_key, worker_id)
+        redis.call('ZREM', session_expiry_key, worker_id)
+        redis.call('ZREM', runtime_expiry_key, worker_id)
+    end
+    local expired_reports = redis.call('ZRANGEBYSCORE', runtime_expiry_key, '-inf', now, 'LIMIT', 0, cleanup_limit)
+    for _, worker_id in ipairs(expired_reports) do
+        redis.call('HDEL', runtime_key, worker_id)
+        redis.call('ZREM', runtime_expiry_key, worker_id)
+    end
+end
+
+local function valid_session(value)
+    return value and value.version == 1 and type(value.workerId) == 'string' and value.workerId ~= '' and
+        type(value.instanceId) == 'string' and value.instanceId ~= '' and
+        type(value.sessionId) == 'string' and value.sessionId ~= '' and
+        valid_uint(value.ackedSnapshotVersion) and valid_uint(value.ackedOwnershipEpoch)
+end
+
+local function valid_owner(value, worker_id, ownership_epoch, now)
+    return value and type(value.workerId) == 'string' and value.workerId == worker_id and
+        type(value.epoch) == 'number' and valid_uint(tostring(value.epoch)) and
+        compare_uint(ownership_epoch, tostring(value.epoch)) >= 0 and
+        type(value.expiresAtMs) == 'number' and value.expiresAtMs > now
+end
+
+local now = now_ms()
+cleanup(now)
+
+if operation == 'replace_session' then
+    if not ttl_ms or ttl_ms <= 0 then
+        return reply('invalid')
+    end
+    local session = decode_table(payload)
+    if not valid_session(session) then
+        return reply('invalid')
+    end
+    local current = decode_table(redis.call('HGET', sessions_key, session.workerId))
+    if current and valid_session(current) and current.sessionId == session.sessionId and
+        current.instanceId == session.instanceId and type(current.expiresAtMs) == 'number' and
+        current.expiresAtMs > now then
+        local epoch_order = compare_uint(session.ackedOwnershipEpoch, current.ackedOwnershipEpoch)
+        local version_order = compare_uint(session.ackedSnapshotVersion, current.ackedSnapshotVersion)
+        if epoch_order < 0 or (epoch_order == 0 and version_order < 0) then
+            return reply('stale')
+        end
+        if epoch_order > 0 or version_order > 0 then
+            redis.call('HDEL', runtime_key, session.workerId)
+            redis.call('ZREM', runtime_expiry_key, session.workerId)
+        end
+    else
+        redis.call('HDEL', runtime_key, session.workerId)
+        redis.call('ZREM', runtime_expiry_key, session.workerId)
+    end
+    session.expiresAtMs = now + ttl_ms
+    redis.call('HSET', sessions_key, session.workerId, cjson.encode(session))
+    redis.call('ZADD', session_expiry_key, session.expiresAtMs, session.workerId)
+    return reply('ok')
+end
+
+if operation == 'replace_report' then
+    if not ttl_ms or ttl_ms <= 0 or type(digest) ~= 'string' or digest == '' then
+        return reply('invalid')
+    end
+    local report = decode_table(payload)
+    if not report or report.version ~= 1 or type(report.workerId) ~= 'string' or report.workerId == '' or
+        type(report.sessionId) ~= 'string' or report.sessionId == '' or not valid_uint(report.sequence) or
+        not valid_uint(report.snapshotVersion) or not valid_uint(report.ownershipEpoch) or
+        type(report.observedAtMs) ~= 'number' or type(report.counters) ~= 'table' then
+        return reply('invalid')
+    end
+    local session = decode_table(redis.call('HGET', sessions_key, report.workerId))
+    if not valid_session(session) or session.workerId ~= report.workerId or session.sessionId ~= report.sessionId or
+        type(session.expiresAtMs) ~= 'number' or session.expiresAtMs <= now then
+        return reply('unavailable')
+    end
+    if report.snapshotVersion ~= session.ackedSnapshotVersion or
+        report.ownershipEpoch ~= session.ackedOwnershipEpoch then
+        return reply('stale')
+    end
+    local current = decode_table(redis.call('HGET', runtime_key, report.workerId))
+    if current and current.sessionId == report.sessionId and valid_uint(current.sequence) then
+        local ordering = compare_uint(report.sequence, current.sequence)
+        if ordering < 0 then
+            return reply('stale')
+        end
+        if ordering == 0 then
+            if current.digest == digest then
+                return reply('ok')
+            end
+            return reply('conflict')
+        end
+    end
+    local seen = {}
+    for _, counter in pairs(report.counters) do
+        if type(counter) ~= 'table' or type(counter.proxyId) ~= 'string' or counter.proxyId == '' or
+            type(counter.active) ~= 'number' or counter.active < 0 or counter.active ~= math.floor(counter.active) or
+            type(counter.reserved) ~= 'number' or counter.reserved < 0 or counter.reserved ~= math.floor(counter.reserved) or
+            type(counter.draining) ~= 'boolean' or seen[counter.proxyId] then
+            return reply('invalid')
+        end
+        seen[counter.proxyId] = true
+        local owner = decode_table(redis.call('HGET', owners_key, counter.proxyId))
+        if not valid_owner(owner, report.workerId, report.ownershipEpoch, now) then
+            return reply('stale')
+        end
+    end
+    report.digest = digest
+    report.expiresAtMs = now + ttl_ms
+    redis.call('HSET', runtime_key, report.workerId, cjson.encode(report))
+    redis.call('ZADD', runtime_expiry_key, report.expiresAtMs, report.workerId)
+    session.expiresAtMs = now + ttl_ms
+    redis.call('HSET', sessions_key, report.workerId, cjson.encode(session))
+    redis.call('ZADD', session_expiry_key, session.expiresAtMs, report.workerId)
+    return reply('ok')
+end
+
+if operation == 'read' then
+    local queries = decode_table(payload)
+    if not queries then
+        return reply('invalid')
+    end
+    if next(queries) == nil then
+        return '{"status":"ok","snapshots":[]}'
+    end
+    local snapshots = cjson.decode('[]')
+    local cache = {}
+    for _, query in ipairs(queries) do
+        if type(query) ~= 'table' or type(query.proxyId) ~= 'string' or query.proxyId == '' or
+            type(query.workerId) ~= 'string' or query.workerId == '' or not valid_uint(query.ownershipEpoch) then
+            return reply('invalid')
+        end
+        local snapshot = {proxyId = query.proxyId, active = 0, reserved = 0, draining = false, fresh = false}
+        local owner = decode_table(redis.call('HGET', owners_key, query.proxyId))
+        if valid_owner(owner, query.workerId, query.ownershipEpoch, now) and
+            compare_uint(query.ownershipEpoch, tostring(owner.epoch)) == 0 then
+            local cached = cache[query.workerId]
+            if not cached then
+                local session = decode_table(redis.call('HGET', sessions_key, query.workerId))
+                local report = decode_table(redis.call('HGET', runtime_key, query.workerId))
+                cached = {fresh = false, counters = {}}
+                if valid_session(session) and session.workerId == query.workerId and report and
+                    report.workerId == query.workerId and report.sessionId == session.sessionId and
+                    type(session.expiresAtMs) == 'number' and session.expiresAtMs > now and
+                    type(report.expiresAtMs) == 'number' and report.expiresAtMs > now and
+                    valid_uint(report.ownershipEpoch) and
+                    report.snapshotVersion == session.ackedSnapshotVersion and
+                    report.ownershipEpoch == session.ackedOwnershipEpoch then
+                    cached.fresh = true
+                    cached.ownershipEpoch = report.ownershipEpoch
+                    if type(report.counters) == 'table' then
+                        for _, counter in pairs(report.counters) do
+                            if type(counter) == 'table' and type(counter.proxyId) == 'string' then
+                                cached.counters[counter.proxyId] = counter
+                            end
+                        end
+                    end
+                end
+                cache[query.workerId] = cached
+            end
+            if cached.fresh and compare_uint(cached.ownershipEpoch, query.ownershipEpoch) >= 0 then
+                snapshot.fresh = true
+                local counter = cached.counters[query.proxyId]
+                if counter then
+                    snapshot.active = counter.active
+                    snapshot.reserved = counter.reserved
+                    snapshot.draining = counter.draining
+                end
+            end
+        end
+        snapshots[#snapshots + 1] = snapshot
+    end
+    return reply('ok', snapshots)
+end
+
+return reply('invalid')

internal/adapters/redisactivity/scripts/sweep.lua

@@ -73,6 +73,12 @@ local function remove_available(proxy_id, record)
     end
 end
 
+local function remove_owned(proxy_id, record)
+    if record and type(record.ownerIndexKey) == 'string' and record.ownerIndexKey ~= '' then
+        redis.call('ZREM', record.ownerIndexKey, proxy_id)
+    end
+end
+
 local function remove_proxy(proxy_id)
     local raw = redis.call('HGET', records_key, proxy_id)
     local record = nil
@@ -80,6 +86,7 @@ local function remove_proxy(proxy_id)
         local decoded
         decoded, record = pcall(cjson.decode, raw)
         remove_available(proxy_id, decoded and record or nil)
+        remove_owned(proxy_id, decoded and record or nil)
         if decoded and type(record) == 'table' and is_managed(record.state) then
             decrement_inventory(record.sourceUpstream)
         end

internal/adapters/redisactivity/scripts/upsert.lua

@@ -70,12 +70,19 @@ local function remove_available(proxy_id, record)
     end
 end
 
+local function remove_owned(proxy_id, record)
+    if record and type(record.ownerIndexKey) == 'string' and record.ownerIndexKey ~= '' then
+        redis.call('ZREM', record.ownerIndexKey, proxy_id)
+    end
+end
+
 local function remove_proxy(proxy_id)
     local raw = redis.call('HGET', records_key, proxy_id)
     local record = nil
     if raw then
         record = cjson.decode(raw)
         remove_available(proxy_id, record)
+        remove_owned(proxy_id, record)
         if is_managed(record.state) then
             decrement_inventory(record.sourceUpstream)
         end
@@ -123,6 +130,16 @@ local function add_available(proxy_id, record)
     end
 end
 
+local function sync_owned(proxy_id, record)
+    if record.state == 'AVAILABLE' and record.ownerWorkerId and record.ownerWorkerId ~= '' and
+        tonumber(record.usableUntilMs) > now_ms then
+        redis.call('ZADD', record.ownerIndexKey, record.usableUntilMs, proxy_id)
+        touch(record.ownerIndexKey, tonumber(record.expiresAtMs))
+    else
+        redis.call('ZREM', record.ownerIndexKey, proxy_id)
+    end
+end
+
 local function finish(reply)
     local encoded = cjson.encode(reply)
     redis.call('SET', operation_key, encoded, 'PX', operation_ttl_ms)
@@ -132,6 +149,11 @@ end
 cleanup_expired()
 
 for _, candidate in ipairs(candidates) do
+    local decoded, incoming = pcall(cjson.decode, candidate.record)
+    if not decoded or type(incoming) ~= 'table' or
+        type(incoming.ownerIndexKey) ~= 'string' or incoming.ownerIndexKey == '' then
+        return finish({status = 'invalid', accepted = 0, inserted = 0, refreshed = 0, dropped = 0})
+    end
     local mapped = redis.call('HGET', idkeys_key, candidate.proxyId)
     if mapped and mapped ~= candidate.uniqueDigest then
         return finish({status = 'invalid', accepted = 0, inserted = 0, refreshed = 0, dropped = 0})
@@ -174,6 +196,7 @@ for _, candidate in ipairs(candidates) do
             local encoded = cjson.encode(incoming)
             redis.call('HSET', records_key, incumbent_id, encoded)
             redis.call('ZADD', expiry_key, incoming.expiresAtMs, incumbent_id)
+            sync_owned(incumbent_id, incoming)
             add_available(incumbent_id, incoming)
             if tonumber(incoming.expiresAtMs) > max_expiry_ms then
                 max_expiry_ms = tonumber(incoming.expiresAtMs)
@@ -192,6 +215,7 @@ for _, candidate in ipairs(candidates) do
             redis.call('HSET', unique_key, candidate.uniqueDigest, candidate.proxyId)
             redis.call('HSET', idkeys_key, candidate.proxyId, candidate.uniqueDigest)
             redis.call('ZADD', expiry_key, incoming.expiresAtMs, candidate.proxyId)
+            sync_owned(candidate.proxyId, incoming)
             if is_managed(incoming.state) then
                 redis.call('HINCRBY', inventory_key, candidate.upstream, 1)
             end

internal/adapters/redisactivity/upsert.go

@@ -139,7 +139,8 @@ func (a *Adapter) prepareUpsertCandidate(
 		CreatedAtMS: candidate.CreatedAt.UnixMilli(), ExpiresAtMS: expiresAt.UnixMilli(),
 		UsableUntilMS: usableUntil.UnixMilli(), LatencyNS: int64(candidate.Latency),
 		MaxConcurrency: candidate.MaxConcurrency, State: string(candidate.State),
-		Tags: cloneTags(candidate.Tags), IndexKeys: a.availableIndexKeys(candidate),
+		Tags: cloneTags(candidate.Tags), OwnerIndexKey: a.keys.owned(upstreamID),
+		IndexKeys: a.availableIndexKeys(candidate),
 	}
 	if candidate.LastCheckedAt != nil {
 		record.LastCheckedAtMS = candidate.LastCheckedAt.UnixMilli()

internal/controller/bootstrap/infrastructure.go

@@ -100,11 +100,13 @@ func (*productionInfrastructure) Open(
 			return ports{}, err
 		}
 		adapter, err := redisactivity.New(redisClient, redisactivity.Options{
-			Namespace:        redisNamespace,
+			Namespace:          redisNamespace,
-			Credentials:      credentialStore,
+			Credentials:        credentialStore,
-			OperationTTL:     redisOperationTTL,
+			OperationTTL:       redisOperationTTL,
-			MaxCandidateScan: candidateScan(configuration),
+			MaxCandidateScan:   candidateScan(configuration),
-			CleanupLimit:     redisCleanupLimit,
+			MaxRuntimeCounters: credentialCapacity(configuration),
+			MaxInventoryScan:   credentialCapacity(configuration),
+			CleanupLimit:       redisCleanupLimit,
 		})
 		if err != nil {
 			return ports{}, err

internal/controller/pool/inventory.go

@@ -0,0 +1,17 @@
+package pool
+
+import (
+	"context"
+	"time"
+)
+
+type InventorySnapshot struct {
+	Managed        int
+	AvailableSlots int64
+}
+
+type InventoryReader interface {
+	// ReadInventory returns a bounded, authoritative aggregate. Unknown Worker
+	// runtime must reduce capacity rather than being treated as idle.
+	ReadInventory(context.Context, string, time.Duration) (InventorySnapshot, error)
+}

internal/controller/pool/reconciler.go

@@ -62,15 +62,29 @@ func NewReconciler(policy ReconcilePolicy, budget *FetchBudget, notifier FetchNo
 // Reconcile centralizes the cold-path decision. The notifier may coalesce many
 // calls; Provider Reconciler atomically reserves the budget before doing I/O.
 func (r *Reconciler) Reconcile(now time.Time, inventory upstream.Inventory) ReconcileDecision {
+	return r.reconcileSnapshot(
+		InventorySnapshot{AvailableSlots: inventory.AvailableSlots(now, r.policy.SafetyMargin)},
+		false,
+	)
+}
+
+func (r *Reconciler) ReconcileSnapshot(inventory InventorySnapshot) ReconcileDecision {
+	return r.reconcileSnapshot(inventory, true)
+}
+
+func (r *Reconciler) reconcileSnapshot(inventory InventorySnapshot, synchronizeManaged bool) ReconcileDecision {
 	usage := r.budget.Snapshot()
-	availableSlots := inventory.AvailableSlots(now, r.policy.SafetyMargin)
+	if synchronizeManaged && inventory.Managed >= 0 && usage.PendingExpected == 0 {
+		_ = r.budget.SynchronizeManaged(inventory.Managed)
+		usage = r.budget.Snapshot()
+	}
 	pendingSlots := saturatingMultiply(int64(usage.PendingExpected), r.slotsPerProxy)
 	decision := ReconcileDecision{
-		AvailableSlots:  availableSlots,
+		AvailableSlots:  inventory.AvailableSlots,
 		PendingExpected: usage.PendingExpected,
 		FetchedTotal:    usage.FetchedTotal,
 		FetchAllowance:  r.budget.FetchAllowance(),
-		EffectiveSlots:  saturatingAdd(availableSlots, pendingSlots),
+		EffectiveSlots:  saturatingAdd(inventory.AvailableSlots, pendingSlots),
 	}
 	r.mu.Lock()
 	if r.refilling {

internal/controller/pool/reconciler_test.go

@@ -141,6 +141,53 @@ func TestPoolReconcilerPendingEstimatePausesWithoutEndingRefillEpisode(t *testin
 	}
 }
 
+func TestPoolReconcilerConsumesAuthoritativeInventorySnapshot(t *testing.T) {
+	budget, err := NewFetchBudget(FetchBudgetConfig{
+		UpstreamID: "provider-a", MaxSize: 10, ExpectedPerFetch: 2,
+	})
+	if err != nil {
+		t.Fatalf("NewFetchBudget(): %v", err)
+	}
+	notifier := &recordingFetchNotifier{}
+	reconciler, err := NewReconciler(ReconcilePolicy{
+		MinimumAvailableSlots: 3, TargetAvailableSlots: 8,
+		ExpectedPerFetch: 2, ExpectedSlotsPerFetch: 2,
+	}, budget, notifier)
+	if err != nil {
+		t.Fatalf("NewReconciler(): %v", err)
+	}
+	decision := reconciler.ReconcileSnapshot(InventorySnapshot{Managed: 9, AvailableSlots: 2})
+	if decision.Triggered || decision.AvailableSlots != 2 || decision.FetchAllowance != 0 {
+		t.Fatalf("ReconcileSnapshot() = %+v, want authoritative managed inventory to close budget", decision)
+	}
+	if usage := budget.Snapshot(); usage.Managed != 9 {
+		t.Fatalf("FetchBudget.Managed = %d, want 9", usage.Managed)
+	}
+}
+
+func TestPoolReconcilerLegacyInventoryDoesNotClearManagedBudget(t *testing.T) {
+	budget, err := NewFetchBudget(FetchBudgetConfig{
+		UpstreamID: "provider-a", MaxSize: 10, ExpectedPerFetch: 2, Managed: 9,
+	})
+	if err != nil {
+		t.Fatalf("NewFetchBudget(): %v", err)
+	}
+	reconciler, err := NewReconciler(ReconcilePolicy{
+		MinimumAvailableSlots: 3, TargetAvailableSlots: 8,
+		ExpectedPerFetch: 2, ExpectedSlotsPerFetch: 2,
+	}, budget, &recordingFetchNotifier{})
+	if err != nil {
+		t.Fatalf("NewReconciler(): %v", err)
+	}
+	decision := reconciler.Reconcile(time.Now(), upstream.Inventory{})
+	if decision.Triggered || decision.FetchAllowance != 0 {
+		t.Fatalf("Reconcile(legacy) = %+v, want preserved managed budget", decision)
+	}
+	if usage := budget.Snapshot(); usage.Managed != 9 {
+		t.Fatalf("FetchBudget.Managed = %d, want 9", usage.Managed)
+	}
+}
+
 func inventoryWithSlots(now time.Time, slots int64) upstream.Inventory {
 	return upstream.Inventory{Proxies: []upstream.ProxyCapacity{{
 		State: proxyDomain.StateAvailable, ExpiresAt: now.Add(time.Minute), Max: slots,

internal/domain/proxy/capacity.go

@@ -13,19 +13,46 @@ var (
 )
 
 type Capacity struct {
-	max      atomic.Uint32
+	max                atomic.Uint32
-	counters atomic.Uint64
+	counters           atomic.Uint64
+	configuredObserver *activityObserver
+	observer           atomic.Pointer[activityObserver]
 }
 
+type activityObserver struct{ notify func(bool) }
+
 func NewCapacity(max int64) *Capacity {
+	return NewCapacityWithActivityObserver(max, nil)
+}
+
+// NewCapacityWithActivityObserver reports successful zero-to-nonzero and
+// nonzero-to-zero transitions. The observer must tolerate concurrent calls.
+func NewCapacityWithActivityObserver(max int64, observer func(nonzero bool)) *Capacity {
 	capacity := &Capacity{}
 	if max < 0 || max > int64(counterMask) {
 		max = 0
 	}
 	capacity.max.Store(uint32(max))
+	if observer != nil {
+		capacity.configuredObserver = &activityObserver{notify: observer}
+		capacity.observer.Store(capacity.configuredObserver)
+	}
 	return capacity
 }
 
+// SetActivityObservationEnabled lets snapshot ownership disable callbacks for
+// current Proxies and enable them only while a runtime is retired and draining.
+func (c *Capacity) SetActivityObservationEnabled(enabled bool) {
+	if c == nil || c.configuredObserver == nil {
+		return
+	}
+	if enabled {
+		c.observer.Store(c.configuredObserver)
+		return
+	}
+	c.observer.Store(nil)
+}
+
 func (c *Capacity) SetMax(max int64) bool {
 	if max < 0 || max > int64(counterMask) {
 		return false
@@ -36,6 +63,15 @@ func (c *Capacity) SetMax(max int64) bool {
 
 func (c *Capacity) Max() int64 { return int64(c.max.Load()) }
 
+func (c *Capacity) Counters() (active, reserved, maximum int64) {
+	if c == nil {
+		return 0, 0, 0
+	}
+	packed := c.counters.Load()
+	activeCounter, reservedCounter := unpack(packed)
+	return int64(activeCounter), int64(reservedCounter), int64(c.max.Load())
+}
+
 func (c *Capacity) Reserve() (*Reservation, bool) {
 	for {
 		current := c.counters.Load()
@@ -45,6 +81,11 @@ func (c *Capacity) Reserve() (*Reservation, bool) {
 		}
 		next := pack(active, reserved+1)
 		if c.counters.CompareAndSwap(current, next) {
+			if active+reserved == 0 {
+				if observer := c.observer.Load(); observer != nil {
+					observer.notify(true)
+				}
+			}
 			return &Reservation{capacity: c}, true
 		}
 	}
@@ -77,7 +118,16 @@ func (c *Capacity) cancel() {
 	for {
 		current := c.counters.Load()
 		active, reserved := unpack(current)
-		if reserved == 0 || c.counters.CompareAndSwap(current, pack(active, reserved-1)) {
+		if reserved == 0 {
+			return
+		}
+		next := pack(active, reserved-1)
+		if c.counters.CompareAndSwap(current, next) {
+			if active+reserved == 1 {
+				if observer := c.observer.Load(); observer != nil {
+					observer.notify(false)
+				}
+			}
 			return
 		}
 	}
@@ -87,7 +137,16 @@ func (c *Capacity) release() {
 	for {
 		current := c.counters.Load()
 		active, reserved := unpack(current)
-		if active == 0 || c.counters.CompareAndSwap(current, pack(active-1, reserved)) {
+		if active == 0 {
+			return
+		}
+		next := pack(active-1, reserved)
+		if c.counters.CompareAndSwap(current, next) {
+			if active+reserved == 1 {
+				if observer := c.observer.Load(); observer != nil {
+					observer.notify(false)
+				}
+			}
 			return
 		}
 	}

internal/domain/proxy/capacity_test.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"errors"
+	"reflect"
 	"sync"
 	"sync/atomic"
 	"testing"
@@ -38,6 +39,56 @@ func TestReservationCancelReleasesReservedCapacity(t *testing.T) {
 	assertCapacityCounters(t, capacity, 0, 0)
 }
 
+func TestCapacityCountersReadsOnePackedSnapshot(t *testing.T) {
+	capacity := NewCapacity(3)
+	first, ok := capacity.Reserve()
+	if !ok {
+		t.Fatal("first Reserve() = false")
+	}
+	second, ok := capacity.Reserve()
+	if !ok {
+		t.Fatal("second Reserve() = false")
+	}
+	if err := first.Commit(); err != nil {
+		t.Fatalf("Commit(): %v", err)
+	}
+
+	active, reserved, maximum := capacity.Counters()
+	if active != 1 || reserved != 1 || maximum != 3 {
+		t.Fatalf("Counters() = (%d, %d, %d), want (1, 1, 3)", active, reserved, maximum)
+	}
+	if err := first.Release(); err != nil {
+		t.Fatalf("Release(): %v", err)
+	}
+	if err := second.Cancel(); err != nil {
+		t.Fatalf("Cancel(): %v", err)
+	}
+}
+
+func TestCapacityActivityObserverTracksOnlyNonzeroTransitions(t *testing.T) {
+	var transitions []bool
+	capacity := NewCapacityWithActivityObserver(2, func(nonzero bool) {
+		transitions = append(transitions, nonzero)
+	})
+	first, ok := capacity.Reserve()
+	if !ok {
+		t.Fatal("Reserve(first) = false")
+	}
+	second, ok := capacity.Reserve()
+	if !ok {
+		t.Fatal("Reserve(second) = false")
+	}
+	if err := first.Cancel(); err != nil {
+		t.Fatalf("Cancel(first): %v", err)
+	}
+	if err := second.Cancel(); err != nil {
+		t.Fatalf("Cancel(second): %v", err)
+	}
+	if !reflect.DeepEqual(transitions, []bool{true, false}) {
+		t.Fatalf("transitions = %v, want [true false]", transitions)
+	}
+}
+
 func TestReservationCommitAndReleaseAreSingleUse(t *testing.T) {
 	capacity := NewCapacity(1)
 	reservation, ok := capacity.Reserve()

internal/domain/workerruntime/memory.go

@@ -0,0 +1,211 @@
+package workerruntime
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/json"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+type MemoryStore struct {
+	mu       sync.Mutex
+	now      func() time.Time
+	sessions map[string]memorySession
+	reports  map[string]memoryReport
+}
+
+type memorySession struct {
+	value     Session
+	expiresAt time.Time
+}
+
+type memoryReport struct {
+	value     Report
+	digest    [sha256.Size]byte
+	expiresAt time.Time
+	counters  map[string]Counter
+}
+
+var (
+	_ SessionWriter = (*MemoryStore)(nil)
+	_ ReportWriter  = (*MemoryStore)(nil)
+	_ RuntimeReader = (*MemoryStore)(nil)
+)
+
+func NewMemoryStore(now func() time.Time) (*MemoryStore, error) {
+	if now == nil {
+		return nil, ErrInvalidStore
+	}
+	return &MemoryStore{
+		now: now, sessions: make(map[string]memorySession), reports: make(map[string]memoryReport),
+	}, nil
+}
+
+func (store *MemoryStore) ReplaceSession(ctx context.Context, session Session, ttl time.Duration) error {
+	if ctx == nil || store == nil || !validSession(session) || ttl <= 0 {
+		return ErrInvalidSession
+	}
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	now := store.now().UTC()
+	if now.IsZero() {
+		return ErrInvalidStore
+	}
+	store.mu.Lock()
+	defer store.mu.Unlock()
+	current, exists := store.sessions[session.WorkerID]
+	identityChanged := exists && (current.value.SessionID != session.SessionID || current.value.InstanceID != session.InstanceID)
+	expired := exists && !current.expiresAt.After(now)
+	if exists && !identityChanged && !expired && sessionBefore(session, current.value) {
+		return ErrStaleSession
+	}
+	ackAdvanced := exists && !identityChanged && !expired && sessionAfter(session, current.value)
+	if identityChanged || expired || ackAdvanced {
+		delete(store.reports, session.WorkerID)
+	}
+	store.sessions[session.WorkerID] = memorySession{value: session, expiresAt: now.Add(ttl)}
+	return nil
+}
+
+func (store *MemoryStore) ReplaceRuntime(ctx context.Context, report Report, ttl time.Duration) error {
+	if ctx == nil || store == nil || ttl <= 0 {
+		return ErrInvalidReport
+	}
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	normalized, counterIndex, err := normalizeReport(report)
+	if err != nil {
+		return err
+	}
+	payload, err := json.Marshal(normalized)
+	if err != nil {
+		return ErrInvalidReport
+	}
+	digest := sha256.Sum256(payload)
+	now := store.now().UTC()
+	if now.IsZero() {
+		return ErrInvalidStore
+	}
+	store.mu.Lock()
+	defer store.mu.Unlock()
+	session, exists := store.sessions[report.WorkerID]
+	if !exists || !session.expiresAt.After(now) || session.value.SessionID != report.SessionID {
+		return ErrStaleSession
+	}
+	if report.SnapshotVersion != session.value.AckedSnapshotVersion ||
+		report.OwnershipEpoch != session.value.AckedOwnershipEpoch {
+		return ErrStaleReport
+	}
+	if current, exists := store.reports[report.WorkerID]; exists && current.value.SessionID == report.SessionID {
+		switch {
+		case normalized.Sequence < current.value.Sequence:
+			return ErrStaleReport
+		case normalized.Sequence == current.value.Sequence && digest != current.digest:
+			return ErrConflictingReport
+		case normalized.Sequence == current.value.Sequence:
+			return nil
+		}
+	}
+	store.reports[report.WorkerID] = memoryReport{
+		value: normalized, digest: digest, expiresAt: now.Add(ttl), counters: counterIndex,
+	}
+	session.expiresAt = now.Add(ttl)
+	store.sessions[report.WorkerID] = session
+	return nil
+}
+
+func (store *MemoryStore) ReadRuntime(ctx context.Context, proxies []OwnedProxy) ([]Snapshot, error) {
+	if ctx == nil || store == nil {
+		return nil, ErrInvalidQuery
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	seen := make(map[string]struct{}, len(proxies))
+	for _, proxy := range proxies {
+		if !clean(proxy.ProxyID) || !clean(proxy.WorkerID) || proxy.OwnershipEpoch == 0 {
+			return nil, ErrInvalidQuery
+		}
+		key := proxy.WorkerID + "\x00" + proxy.ProxyID
+		if _, exists := seen[key]; exists {
+			return nil, ErrInvalidQuery
+		}
+		seen[key] = struct{}{}
+	}
+	now := store.now().UTC()
+	if now.IsZero() {
+		return nil, ErrInvalidStore
+	}
+	store.mu.Lock()
+	defer store.mu.Unlock()
+	result := make([]Snapshot, len(proxies))
+	for index, proxy := range proxies {
+		result[index].ProxyID = proxy.ProxyID
+		session, sessionExists := store.sessions[proxy.WorkerID]
+		report, reportExists := store.reports[proxy.WorkerID]
+		if !sessionExists || !reportExists || !session.expiresAt.After(now) || !report.expiresAt.After(now) ||
+			report.value.SessionID != session.value.SessionID ||
+			report.value.SnapshotVersion != session.value.AckedSnapshotVersion ||
+			report.value.OwnershipEpoch != session.value.AckedOwnershipEpoch ||
+			report.value.OwnershipEpoch < proxy.OwnershipEpoch {
+			continue
+		}
+		result[index].Fresh = true
+		if counter, exists := report.counters[proxy.ProxyID]; exists {
+			result[index].Active = counter.Active
+			result[index].Reserved = counter.Reserved
+			result[index].Draining = counter.Draining
+		}
+	}
+	return result, nil
+}
+
+func normalizeReport(report Report) (Report, map[string]Counter, error) {
+	if !clean(report.WorkerID) || !clean(report.SessionID) || report.Sequence == 0 ||
+		report.SnapshotVersion == 0 || report.OwnershipEpoch == 0 || report.ObservedAt.IsZero() {
+		return Report{}, nil, ErrInvalidReport
+	}
+	normalized := report
+	normalized.ObservedAt = report.ObservedAt.UTC()
+	normalized.Counters = append([]Counter(nil), report.Counters...)
+	sort.Slice(normalized.Counters, func(left, right int) bool {
+		return normalized.Counters[left].ProxyID < normalized.Counters[right].ProxyID
+	})
+	index := make(map[string]Counter, len(normalized.Counters))
+	for _, counter := range normalized.Counters {
+		if !clean(counter.ProxyID) || counter.Active < 0 || counter.Reserved < 0 {
+			return Report{}, nil, ErrInvalidReport
+		}
+		if _, exists := index[counter.ProxyID]; exists {
+			return Report{}, nil, ErrInvalidReport
+		}
+		index[counter.ProxyID] = counter
+	}
+	return normalized, index, nil
+}
+
+func validSession(session Session) bool {
+	return clean(session.WorkerID) && clean(session.InstanceID) && clean(session.SessionID) &&
+		session.AckedSnapshotVersion > 0 && session.AckedOwnershipEpoch > 0
+}
+
+func sessionBefore(left, right Session) bool {
+	return left.AckedOwnershipEpoch < right.AckedOwnershipEpoch ||
+		(left.AckedOwnershipEpoch == right.AckedOwnershipEpoch &&
+			left.AckedSnapshotVersion < right.AckedSnapshotVersion)
+}
+
+func sessionAfter(left, right Session) bool {
+	return left.AckedOwnershipEpoch > right.AckedOwnershipEpoch ||
+		(left.AckedOwnershipEpoch == right.AckedOwnershipEpoch &&
+			left.AckedSnapshotVersion > right.AckedSnapshotVersion)
+}
+
+func clean(value string) bool {
+	return value != "" && strings.TrimSpace(value) == value
+}

internal/domain/workerruntime/memory_test.go

@@ -0,0 +1,156 @@
+package workerruntime
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestMemoryStoreReplacesSparseRuntimeAndClearsMissingCounters(t *testing.T) {
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	store := newRuntimeStore(t, &now)
+	ctx := context.Background()
+	registerRuntimeSession(t, store, "session-a", time.Minute)
+	report := Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 3, OwnershipEpoch: 9, ObservedAt: now,
+		Counters: []Counter{{ProxyID: "proxy-a", Active: 2, Reserved: 1}},
+	}
+	if err := store.ReplaceRuntime(ctx, report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(first): %v", err)
+	}
+	got, err := store.ReadRuntime(ctx, []OwnedProxy{{ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: 9}})
+	if err != nil || len(got) != 1 || got[0] != (Snapshot{ProxyID: "proxy-a", Active: 2, Reserved: 1, Fresh: true}) {
+		t.Fatalf("ReadRuntime(first) = %+v, %v", got, err)
+	}
+
+	report.Sequence = 2
+	report.ObservedAt = now.Add(time.Second)
+	report.Counters = nil
+	if err := store.ReplaceRuntime(ctx, report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(empty): %v", err)
+	}
+	got, err = store.ReadRuntime(ctx, []OwnedProxy{{ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: 9}})
+	if err != nil || len(got) != 1 || got[0] != (Snapshot{ProxyID: "proxy-a", Fresh: true}) {
+		t.Fatalf("ReadRuntime(empty) = %+v, %v", got, err)
+	}
+}
+
+func TestMemoryStoreFencesSessionsAndReportSequence(t *testing.T) {
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	store := newRuntimeStore(t, &now)
+	ctx := context.Background()
+	registerRuntimeSession(t, store, "session-a", time.Minute)
+	report := Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 2,
+		SnapshotVersion: 3, OwnershipEpoch: 9, ObservedAt: now,
+		Counters: []Counter{{ProxyID: "proxy-a", Active: 1}},
+	}
+	if err := store.ReplaceRuntime(ctx, report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(first): %v", err)
+	}
+	if err := store.ReplaceRuntime(ctx, report, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(idempotent): %v", err)
+	}
+	conflict := report
+	conflict.Counters = []Counter{{ProxyID: "proxy-a", Active: 2}}
+	if err := store.ReplaceRuntime(ctx, conflict, time.Minute); !errors.Is(err, ErrConflictingReport) {
+		t.Fatalf("ReplaceRuntime(conflict) error = %v", err)
+	}
+	stale := report
+	stale.Sequence = 1
+	if err := store.ReplaceRuntime(ctx, stale, time.Minute); !errors.Is(err, ErrStaleReport) {
+		t.Fatalf("ReplaceRuntime(stale) error = %v", err)
+	}
+	registerRuntimeSession(t, store, "session-b", time.Minute)
+	if err := store.ReplaceRuntime(ctx, report, time.Minute); !errors.Is(err, ErrStaleSession) {
+		t.Fatalf("ReplaceRuntime(old session) error = %v", err)
+	}
+}
+
+func TestMemoryStoreFailsClosedForExpiredOrOlderOwnershipReport(t *testing.T) {
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	store := newRuntimeStore(t, &now)
+	ctx := context.Background()
+	registerRuntimeSession(t, store, "session-a", time.Minute)
+	if err := store.ReplaceRuntime(ctx, Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 3, OwnershipEpoch: 9, ObservedAt: now,
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(): %v", err)
+	}
+	queries := []OwnedProxy{
+		{ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: 10},
+		{ProxyID: "proxy-b", WorkerID: "worker-a", OwnershipEpoch: 9},
+	}
+	got, err := store.ReadRuntime(ctx, queries)
+	if err != nil || got[0].Fresh || !got[1].Fresh {
+		t.Fatalf("ReadRuntime(ownership fence) = %+v, %v", got, err)
+	}
+	now = now.Add(time.Minute)
+	got, err = store.ReadRuntime(ctx, queries[1:])
+	if err != nil || len(got) != 1 || got[0].Fresh {
+		t.Fatalf("ReadRuntime(expired) = %+v, %v", got, err)
+	}
+}
+
+func TestMemoryStoreRejectsRuntimeBeyondAcknowledgedSnapshot(t *testing.T) {
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	store := newRuntimeStore(t, &now)
+	registerRuntimeSession(t, store, "session-a", time.Minute)
+	report := Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 4, OwnershipEpoch: 9, ObservedAt: now,
+	}
+	if err := store.ReplaceRuntime(context.Background(), report, time.Minute); !errors.Is(err, ErrStaleReport) {
+		t.Fatalf("ReplaceRuntime(ahead snapshot) error = %v, want ErrStaleReport", err)
+	}
+	report.SnapshotVersion = 3
+	report.OwnershipEpoch = 10
+	if err := store.ReplaceRuntime(context.Background(), report, time.Minute); !errors.Is(err, ErrStaleReport) {
+		t.Fatalf("ReplaceRuntime(ahead epoch) error = %v, want ErrStaleReport", err)
+	}
+}
+
+func TestMemoryStoreExpiredSameIdentitySessionDoesNotReactivateOldReport(t *testing.T) {
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	store := newRuntimeStore(t, &now)
+	registerRuntimeSession(t, store, "session-a", time.Second)
+	if err := store.ReplaceRuntime(context.Background(), Report{
+		WorkerID: "worker-a", SessionID: "session-a", Sequence: 1,
+		SnapshotVersion: 3, OwnershipEpoch: 9, ObservedAt: now,
+	}, time.Minute); err != nil {
+		t.Fatalf("ReplaceRuntime(): %v", err)
+	}
+	session := store.sessions["worker-a"]
+	session.expiresAt = now.Add(time.Second)
+	store.sessions["worker-a"] = session
+	now = now.Add(2 * time.Second)
+	registerRuntimeSession(t, store, "session-a", time.Minute)
+	got, err := store.ReadRuntime(context.Background(), []OwnedProxy{{
+		ProxyID: "proxy-a", WorkerID: "worker-a", OwnershipEpoch: 9,
+	}})
+	if err != nil || len(got) != 1 || got[0].Fresh {
+		t.Fatalf("ReadRuntime(after re-register) = %+v, %v; want stale", got, err)
+	}
+}
+
+func newRuntimeStore(t *testing.T, now *time.Time) *MemoryStore {
+	t.Helper()
+	store, err := NewMemoryStore(func() time.Time { return *now })
+	if err != nil {
+		t.Fatalf("NewMemoryStore(): %v", err)
+	}
+	return store
+}
+
+func registerRuntimeSession(t *testing.T, store *MemoryStore, sessionID string, ttl time.Duration) {
+	t.Helper()
+	if err := store.ReplaceSession(context.Background(), Session{
+		WorkerID: "worker-a", InstanceID: "instance-a", SessionID: sessionID,
+		AckedSnapshotVersion: 3, AckedOwnershipEpoch: 9,
+	}, ttl); err != nil {
+		t.Fatalf("ReplaceSession(): %v", err)
+	}
+}

internal/domain/workerruntime/runtime.go

@@ -0,0 +1,70 @@
+package workerruntime
+
+import (
+	"context"
+	"errors"
+	"time"
+)
+
+var (
+	ErrInvalidStore      = errors.New("invalid worker runtime store")
+	ErrInvalidSession    = errors.New("invalid worker runtime session")
+	ErrInvalidReport     = errors.New("invalid worker runtime report")
+	ErrInvalidQuery      = errors.New("invalid worker runtime query")
+	ErrStaleSession      = errors.New("stale worker runtime session")
+	ErrStaleReport       = errors.New("stale worker runtime report")
+	ErrConflictingReport = errors.New("conflicting worker runtime report")
+)
+
+type Session struct {
+	WorkerID             string
+	InstanceID           string
+	SessionID            string
+	AckedSnapshotVersion uint64
+	AckedOwnershipEpoch  uint64
+}
+
+type Counter struct {
+	ProxyID  string
+	Active   int64
+	Reserved int64
+	Draining bool
+}
+
+// Report is a complete sparse replacement. Missing counters are zero for the
+// reported Worker snapshot; callers must increase Sequence for every update.
+type Report struct {
+	WorkerID        string
+	SessionID       string
+	Sequence        uint64
+	SnapshotVersion uint64
+	OwnershipEpoch  uint64
+	ObservedAt      time.Time
+	Counters        []Counter
+}
+
+type OwnedProxy struct {
+	ProxyID        string
+	WorkerID       string
+	OwnershipEpoch uint64
+}
+
+type Snapshot struct {
+	ProxyID  string
+	Active   int64
+	Reserved int64
+	Draining bool
+	Fresh    bool
+}
+
+type SessionWriter interface {
+	ReplaceSession(context.Context, Session, time.Duration) error
+}
+
+type ReportWriter interface {
+	ReplaceRuntime(context.Context, Report, time.Duration) error
+}
+
+type RuntimeReader interface {
+	ReadRuntime(context.Context, []OwnedProxy) ([]Snapshot, error)
+}

internal/gateway/snapshot/store.go

@@ -7,19 +7,90 @@ import (
 	"errors"
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
 
 	proxyDomain "proxy-pool/internal/domain/proxy"
+	"proxy-pool/internal/domain/workerruntime"
 )
 
 var (
-	ErrWrongTarget      = errors.New("snapshot targets another cluster or worker")
+	ErrWrongTarget          = errors.New("snapshot targets another cluster or worker")
-	ErrResyncRequired   = errors.New("snapshot sequence requires a full resync")
+	ErrResyncRequired       = errors.New("snapshot sequence requires a full resync")
-	ErrChecksumMismatch = errors.New("snapshot checksum mismatch")
+	ErrChecksumMismatch     = errors.New("snapshot checksum mismatch")
+	ErrInvalidRuntimeReport = errors.New("invalid worker runtime report")
+	ErrInvalidRuntimeLimit  = errors.New("invalid snapshot runtime limit")
+	ErrRuntimeLimitExceeded = errors.New("snapshot runtime limit exceeded")
 )
 
+const defaultRuntimeLimit = 1_000_000
+
+const activeRuntimeShardCount = 64
+
+type activeRuntimeShard struct {
+	mu      sync.Mutex
+	entries map[string]*proxyDomain.Capacity
+}
+
+type activeRuntimeIndex [activeRuntimeShardCount]activeRuntimeShard
+
+func (index *activeRuntimeIndex) track(proxyID string, runtime *proxyDomain.Capacity, nonzero bool) {
+	shard := &index[activeRuntimeShardIndex(proxyID)]
+	shard.mu.Lock()
+	defer shard.mu.Unlock()
+	if nonzero {
+		if shard.entries == nil {
+			shard.entries = make(map[string]*proxyDomain.Capacity)
+		}
+		shard.entries[proxyID] = runtime
+		return
+	}
+	active, reserved, _ := runtime.Counters()
+	if active == 0 && reserved == 0 && shard.entries[proxyID] == runtime {
+		delete(shard.entries, proxyID)
+	}
+}
+
+func (index *activeRuntimeIndex) remove(proxyID string, runtime *proxyDomain.Capacity) {
+	shard := &index[activeRuntimeShardIndex(proxyID)]
+	shard.mu.Lock()
+	defer shard.mu.Unlock()
+	if shard.entries[proxyID] == runtime {
+		delete(shard.entries, proxyID)
+	}
+}
+
+func (index *activeRuntimeIndex) rangeEntries(visit func(string, *proxyDomain.Capacity)) {
+	for shardIndex := range index {
+		shard := &index[shardIndex]
+		shard.mu.Lock()
+		for proxyID, runtime := range shard.entries {
+			visit(proxyID, runtime)
+		}
+		shard.mu.Unlock()
+	}
+}
+
+func activeRuntimeShardIndex(proxyID string) uint64 {
+	const (
+		offset = uint64(14695981039346656037)
+		prime  = uint64(1099511628211)
+	)
+	hash := offset
+	for index := 0; index < len(proxyID); index++ {
+		hash ^= uint64(proxyID[index])
+		hash *= prime
+	}
+	return hash % activeRuntimeShardCount
+}
+
+type runtimeRegistration struct {
+	capacity *proxyDomain.Capacity
+	current  atomic.Bool
+}
+
 type Envelope struct {
 	ClusterID string
 	WorkerID  string
@@ -70,17 +141,29 @@ type Store struct {
 	current   atomic.Pointer[View]
 
 	mu       sync.Mutex
-	runtimes map[string]*proxyDomain.Capacity
+	runtimes map[string]*runtimeRegistration
+	active   activeRuntimeIndex
+	limit    int
 }
 
 func NewStore(clusterID, workerID string) *Store {
 	return &Store{
 		clusterID: clusterID,
 		workerID:  workerID,
-		runtimes:  make(map[string]*proxyDomain.Capacity),
+		runtimes:  make(map[string]*runtimeRegistration),
+		limit:     defaultRuntimeLimit,
 	}
 }
 
+func NewStoreWithRuntimeLimit(clusterID, workerID string, limit int) (*Store, error) {
+	if limit <= 0 {
+		return nil, ErrInvalidRuntimeLimit
+	}
+	store := NewStore(clusterID, workerID)
+	store.limit = limit
+	return store, nil
+}
+
 func (s *Store) Current() *View {
 	if s == nil {
 		return nil
@@ -88,6 +171,49 @@ func (s *Store) Current() *View {
 	return s.current.Load()
 }
 
+func (s *Store) RuntimeReport(sessionID string, sequence uint64, observedAt time.Time) (workerruntime.Report, error) {
+	if s == nil || strings.TrimSpace(sessionID) != sessionID || sessionID == "" || sequence == 0 || observedAt.IsZero() {
+		return workerruntime.Report{}, ErrInvalidRuntimeReport
+	}
+	current := s.current.Load()
+	if current == nil {
+		return workerruntime.Report{}, ErrInvalidRuntimeReport
+	}
+	visible := make(map[string]struct{}, len(current.Entries))
+	counters := make([]workerruntime.Counter, 0)
+	for _, entry := range current.Entries {
+		visible[entry.Proxy.ID] = struct{}{}
+		active, reserved, _ := entry.Runtime.Counters()
+		if active == 0 && reserved == 0 {
+			continue
+		}
+		counters = append(counters, workerruntime.Counter{
+			ProxyID: entry.Proxy.ID, Active: active, Reserved: reserved,
+			Draining: entry.Proxy.State == proxyDomain.StateDraining,
+		})
+	}
+	s.active.rangeEntries(func(proxyID string, runtime *proxyDomain.Capacity) {
+		if _, currentProxy := visible[proxyID]; currentProxy {
+			return
+		}
+		active, reserved, _ := runtime.Counters()
+		if active == 0 && reserved == 0 {
+			return
+		}
+		counters = append(counters, workerruntime.Counter{
+			ProxyID: proxyID, Active: active, Reserved: reserved, Draining: true,
+		})
+	})
+	sort.Slice(counters, func(left, right int) bool {
+		return counters[left].ProxyID < counters[right].ProxyID
+	})
+	return workerruntime.Report{
+		WorkerID: s.workerID, SessionID: sessionID, Sequence: sequence,
+		SnapshotVersion: current.Version, OwnershipEpoch: current.Epoch,
+		ObservedAt: observedAt.UTC(), Counters: counters,
+	}, nil
+}
+
 func (s *Store) Apply(envelope Envelope) error {
 	if s == nil {
 		return fmt.Errorf("apply snapshot: nil store")
@@ -118,19 +244,47 @@ func (s *Store) Apply(envelope Envelope) error {
 	}
 
 	proxies := cloneAndSort(envelope.Proxies)
+	newRuntimeCount := 0
+	for _, descriptor := range proxies {
+		if s.runtimes[descriptor.ID] == nil {
+			newRuntimeCount++
+		}
+	}
+	if len(s.runtimes)+newRuntimeCount > s.limit {
+		return ErrRuntimeLimitExceeded
+	}
+	if current != nil {
+		for _, entry := range current.Entries {
+			registration := s.runtimes[entry.Proxy.ID]
+			registration.capacity.SetActivityObservationEnabled(true)
+			registration.current.Store(false)
+			active, reserved, _ := registration.capacity.Counters()
+			s.active.track(entry.Proxy.ID, registration.capacity, active+reserved > 0)
+		}
+	}
 	entries := make([]Entry, 0, len(proxies))
 	for _, descriptor := range proxies {
-		runtime := s.runtimes[descriptor.ID]
+		registration := s.runtimes[descriptor.ID]
-		if runtime == nil {
+		if registration == nil {
-			runtime = proxyDomain.NewCapacity(descriptor.MaxConcurrency)
+			proxyID := descriptor.ID
+			registration = &runtimeRegistration{}
+			registration.capacity = proxyDomain.NewCapacityWithActivityObserver(descriptor.MaxConcurrency, func(nonzero bool) {
+				if registration.current.Load() {
+					return
+				}
+				s.active.track(proxyID, registration.capacity, nonzero)
+			})
 		} else {
-			runtime.SetMax(descriptor.MaxConcurrency)
+			registration.capacity.SetMax(descriptor.MaxConcurrency)
 		}
+		registration.current.Store(true)
+		registration.capacity.SetActivityObservationEnabled(false)
+		s.active.remove(descriptor.ID, registration.capacity)
 		// Keep runtimes for temporarily absent IDs. Old immutable views may still
 		// hold in-flight leases, so reclaiming here could reset active capacity if
 		// the same Proxy reappears in a later snapshot.
-		s.runtimes[descriptor.ID] = runtime
+		s.runtimes[descriptor.ID] = registration
-		entries = append(entries, Entry{Proxy: descriptor, Runtime: runtime})
+		entries = append(entries, Entry{Proxy: descriptor, Runtime: registration.capacity})
 	}
 
 	next := &View{

internal/gateway/snapshot/store_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	proxyDomain "proxy-pool/internal/domain/proxy"
+	"proxy-pool/internal/domain/workerruntime"
 )
 
 func TestStoreAppliesCompleteSnapshotsInOrder(t *testing.T) {
@@ -266,6 +267,165 @@ func TestStoreReusesRuntimeWhenProxyDisappearsAndReappears(t *testing.T) {
 	}
 }
 
+func TestStoreRuntimeReportKeepsRemovedActiveProxyUntilRelease(t *testing.T) {
+	store := NewStore("cluster-a", "worker-a")
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	proxy := proxyDomain.Proxy{
+		ID: "proxy-a", Scheme: proxyDomain.SchemeHTTP, SourceUpstream: "provider-a",
+		State: proxyDomain.StateAvailable, MaxConcurrency: 1,
+	}
+	initial := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 1, Full: true,
+		Proxies: []proxyDomain.Proxy{proxy},
+	}
+	initial.Checksum = Checksum(initial.Proxies)
+	if err := store.Apply(initial); err != nil {
+		t.Fatalf("Apply(initial): %v", err)
+	}
+	runtime := store.Current().Entries[0].Runtime
+	reservation, ok := runtime.Reserve()
+	if !ok {
+		t.Fatal("Reserve() = false")
+	}
+	if err := reservation.Commit(); err != nil {
+		t.Fatalf("Commit(): %v", err)
+	}
+	removed := Envelope{ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 2, Full: true}
+	removed.Checksum = Checksum(nil)
+	if err := store.Apply(removed); err != nil {
+		t.Fatalf("Apply(remove): %v", err)
+	}
+	if got := store.activeRuntimeCount(); got != 1 {
+		t.Fatalf("activeRuntimeCount(removed) = %d, want 1", got)
+	}
+
+	report, err := store.RuntimeReport("session-a", 7, now)
+	if err != nil {
+		t.Fatalf("RuntimeReport(): %v", err)
+	}
+	if report.WorkerID != "worker-a" || report.SessionID != "session-a" || report.Sequence != 7 ||
+		report.SnapshotVersion != 2 || report.OwnershipEpoch != 1 || !report.ObservedAt.Equal(now) ||
+		len(report.Counters) != 1 || report.Counters[0] != (workerruntime.Counter{
+		ProxyID: "proxy-a", Active: 1, Draining: true,
+	}) {
+		t.Fatalf("RuntimeReport() = %+v", report)
+	}
+	if err := reservation.Release(); err != nil {
+		t.Fatalf("Release(): %v", err)
+	}
+	if got := store.activeRuntimeCount(); got != 0 {
+		t.Fatalf("activeRuntimeCount(released) = %d, want 0", got)
+	}
+	report, err = store.RuntimeReport("session-a", 8, now.Add(time.Second))
+	if err != nil || len(report.Counters) != 0 {
+		t.Fatalf("RuntimeReport(after release) = %+v, %v", report, err)
+	}
+}
+
+func TestStoreRuntimeReportMarksCurrentDrainingProxy(t *testing.T) {
+	store := NewStore("cluster-a", "worker-a")
+	now := time.Date(2026, 7, 30, 15, 0, 0, 0, time.UTC)
+	proxy := proxyDomain.Proxy{
+		ID: "proxy-a", Scheme: proxyDomain.SchemeHTTP,
+		State: proxyDomain.StateDraining, MaxConcurrency: 1,
+	}
+	envelope := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 1, Full: true,
+		Proxies: []proxyDomain.Proxy{proxy},
+	}
+	envelope.Checksum = Checksum(envelope.Proxies)
+	if err := store.Apply(envelope); err != nil {
+		t.Fatalf("Apply(): %v", err)
+	}
+	reservation, ok := store.Current().Entries[0].Runtime.Reserve()
+	if !ok {
+		t.Fatal("Reserve() = false")
+	}
+	report, err := store.RuntimeReport("session-a", 1, now)
+	if err != nil || len(report.Counters) != 1 || !report.Counters[0].Draining {
+		t.Fatalf("RuntimeReport() = %+v, %v", report, err)
+	}
+	if err := reservation.Cancel(); err != nil {
+		t.Fatalf("Cancel(): %v", err)
+	}
+}
+
+func TestStoreBoundsHistoricalRuntimeRegistryAndKeepsApplyTransactional(t *testing.T) {
+	store, err := NewStoreWithRuntimeLimit("cluster-a", "worker-a", 1)
+	if err != nil {
+		t.Fatalf("NewStoreWithRuntimeLimit(): %v", err)
+	}
+	first := proxyDomain.Proxy{
+		ID: "proxy-a", Scheme: proxyDomain.SchemeHTTP,
+		State: proxyDomain.StateAvailable, MaxConcurrency: 1,
+	}
+	envelope := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 1,
+		Full: true, Proxies: []proxyDomain.Proxy{first},
+	}
+	envelope.Checksum = Checksum(envelope.Proxies)
+	if err := store.Apply(envelope); err != nil {
+		t.Fatalf("Apply(first): %v", err)
+	}
+	removed := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 2, Full: true,
+	}
+	removed.Checksum = Checksum(nil)
+	if err := store.Apply(removed); err != nil {
+		t.Fatalf("Apply(removed): %v", err)
+	}
+	second := first
+	second.ID = "proxy-b"
+	overLimit := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 3,
+		Full: true, Proxies: []proxyDomain.Proxy{second},
+	}
+	overLimit.Checksum = Checksum(overLimit.Proxies)
+	if err := store.Apply(overLimit); !errors.Is(err, ErrRuntimeLimitExceeded) {
+		t.Fatalf("Apply(over limit) error = %v, want ErrRuntimeLimitExceeded", err)
+	}
+	if current := store.Current(); current.Version != 2 || len(current.Entries) != 0 {
+		t.Fatalf("Current() after rejected apply = version %d entries %d", current.Version, len(current.Entries))
+	}
+}
+
+func TestStoreRuntimeActiveIndexDropsZeroCounters(t *testing.T) {
+	store := NewStore("cluster-a", "worker-a")
+	proxy := proxyDomain.Proxy{
+		ID: "proxy-a", Scheme: proxyDomain.SchemeHTTP,
+		State: proxyDomain.StateAvailable, MaxConcurrency: 1,
+	}
+	envelope := Envelope{
+		ClusterID: "cluster-a", WorkerID: "worker-a", Epoch: 1, Version: 1,
+		Full: true, Proxies: []proxyDomain.Proxy{proxy},
+	}
+	envelope.Checksum = Checksum(envelope.Proxies)
+	if err := store.Apply(envelope); err != nil {
+		t.Fatalf("Apply(): %v", err)
+	}
+	reservation, ok := store.Current().Entries[0].Runtime.Reserve()
+	if !ok {
+		t.Fatal("Reserve() = false")
+	}
+	if got := store.activeRuntimeCount(); got != 0 {
+		t.Fatalf("activeRuntimeCount(current) = %d, want 0", got)
+	}
+	if err := reservation.Cancel(); err != nil {
+		t.Fatalf("Cancel(): %v", err)
+	}
+	if got := store.activeRuntimeCount(); got != 0 {
+		t.Fatalf("activeRuntimeCount() = %d, want 0", got)
+	}
+}
+
+func (s *Store) activeRuntimeCount() int {
+	count := 0
+	s.active.rangeEntries(func(_ string, _ *proxyDomain.Capacity) {
+		count++
+	})
+	return count
+}
+
 func collectSelectionIDs(selection Selection) []string {
 	ids := make([]string, 0, selection.Len())
 	for index := 0; index < selection.Len(); index++ {