@@ -28,3 +28,6 @@ vendor/
 # Internal planning docs (not OSS-ready)
 /PRD-*.md
 dist/
+
+# Local benchmark data, profiles, and Go caches
+/.cache/
@@ -1,4 +1,4 @@
-.PHONY: build build-verify run test docker lint clean
+.PHONY: build build-verify run test docker lint clean bench-e2e bench-e2e-open-loop
 
 build:
 	CGO_ENABLED=0 go build -o bin/agentgate ./cmd/agentgw
@@ -12,6 +12,17 @@ run:
 test:
 	CGO_ENABLED=0 go test -v -count=1 ./...
 
+BENCHTIME ?= 20000x
+BENCH_FILTER ?= ^BenchmarkHandleActE2E$$
+
+bench-e2e-open-loop: BENCH_FILTER = ^BenchmarkHandleActOpenLoop$$
+
+bench-e2e bench-e2e-open-loop:
+	mkdir -p .cache/tmp .cache/go-tmp .cache/go-build
+	TMPDIR="$(CURDIR)/.cache/tmp" GOTMPDIR="$(CURDIR)/.cache/go-tmp" \
+		GOCACHE="$(CURDIR)/.cache/go-build" GOMAXPROCS=4 \
+		go test -tags=bench ./bench -run '^$$' -bench '$(BENCH_FILTER)' -benchtime=$(BENCHTIME) -count=1
+
 docker:
 	docker-compose up --build
 
 
@@ -0,0 +1,359 @@
+//go:build bench
+
+package bench
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log/slog"
+	"math"
+	"net/http"
+	"net/http/httptest"
+	"path/filepath"
+	"runtime"
+	"slices"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/Clawdlinux/agentgate/internal/auth"
+	agentgatedb "github.com/Clawdlinux/agentgate/internal/db"
+	"github.com/Clawdlinux/agentgate/internal/gateway"
+	"github.com/Clawdlinux/agentgate/internal/ratelimit"
+	"github.com/Clawdlinux/agentgate/internal/receipt"
+	"github.com/Clawdlinux/agentgate/internal/registry"
+	"github.com/Clawdlinux/agentgate/internal/signer"
+	"github.com/Clawdlinux/agentgate/internal/vault"
+)
+
+const warmupRequests = 256
+
+type stack struct {
+	db       *sql.DB
+	ledger   *receipt.Ledger
+	client   *http.Client
+	url      string
+	key      string
+	upstream []chan time.Duration
+}
+
+type stackOptions struct {
+	timingSlots  int
+	spinUpstream bool
+}
+
+type benchmarkLogWriter struct {
+	b *testing.B
+}
+
+func (w benchmarkLogWriter) Write(data []byte) (int, error) {
+	if bytes.Contains(data, []byte(`"level":"ERROR"`)) {
+		w.b.Logf("gateway error: %s", data)
+	}
+	return len(data), nil
+}
+
+func newStack(b *testing.B, concurrency int, delay time.Duration) *stack {
+	b.Helper()
+	return newStackWithOptions(b, concurrency, delay, stackOptions{})
+}
+
+func newStackWithOptions(b *testing.B, concurrency int, delay time.Duration, options stackOptions) *stack {
+	b.Helper()
+	database, err := agentgatedb.Open(filepath.Join(b.TempDir(), "agentgate.db"))
+	must(b, err)
+	b.Cleanup(func() { database.Close() })
+	must(b, agentgatedb.RunMigrations(database))
+
+	masterKey := make([]byte, 32)
+	_, err = rand.Read(masterKey)
+	must(b, err)
+	pepper, err := auth.DeriveKeyPepper(masterKey)
+	must(b, err)
+	keys, err := auth.NewKeyStore(database, pepper)
+	must(b, err)
+	_, plaintext, err := keys.Create(context.Background(), "e2e-bench", []string{"mock"}, []string{"bench-user"})
+	must(b, err)
+	store, err := vault.NewSQLiteStore(database, masterKey)
+	must(b, err)
+	cached, err := vault.NewCachedStore(store)
+	must(b, err)
+	token := make([]byte, 32)
+	_, err = rand.Read(token)
+	must(b, err)
+	credential := fmt.Sprintf("%x", token)
+	must(b, cached.Put("bench-user", "mock", vault.Token{AccessToken: credential, TokenType: "Bearer"}))
+
+	signers, err := signer.NewStore(database, masterKey)
+	must(b, err)
+	b.Cleanup(signers.Close)
+	_, signingKey, err := signers.LoadOrCreateActive(1)
+	clear(signingKey)
+	must(b, err)
+	ledger := receipt.NewLedger(database, signers)
+	b.Cleanup(ledger.Close)
+
+	timings := make([]chan time.Duration, max(concurrency, options.timingSlots))
+	for i := range timings {
+		timings[i] = make(chan time.Duration, 1)
+	}
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+		var params struct {
+			Worker int `json:"worker"`
+		}
+		if r.Method != http.MethodPost || r.Header.Get("Authorization") != "Bearer "+credential {
+			http.Error(w, "unexpected upstream request", http.StatusBadRequest)
+			return
+		}
+		if err := json.NewDecoder(r.Body).Decode(&params); err != nil || params.Worker < 0 || params.Worker >= len(timings) {
+			http.Error(w, "invalid worker", http.StatusBadRequest)
+			return
+		}
+		// Closed-loop workers serialize requests. Open-loop requests each have their own slot.
+		defer func() { timings[params.Worker] <- time.Since(start) }()
+		if delay > 0 {
+			if options.spinUpstream {
+				until := time.Now().Add(delay)
+				for time.Now().Before(until) {
+				}
+			} else {
+				time.Sleep(delay)
+			}
+		}
+		w.Header().Set("Content-Type", "application/json")
+		io.WriteString(w, `{"ok":true}`)
+	}))
+	b.Cleanup(upstream.Close)
+
+	reg := registry.New()
+	must(b, reg.LoadBytes([]byte(fmt.Sprintf(`services:
+  mock:
+    base_url: %s
+    auth:
+      type: bearer
+    rate_limit:
+      requests_per_second: 1000000
+      burst: 1000000
+    actions:
+      echo:
+        method: POST
+        path: /echo
+        params:
+          worker: int
+`, upstream.URL))))
+	limiter := ratelimit.New(reg.RateLimits(), ratelimit.WithSettings(ratelimit.Settings{
+		KeyRPS: 1e6, KeyBurst: 1e6, TenantRPS: 1e6, TenantBurst: 1e6, TenantMaxInflight: 1024,
+	}))
+	handler := gateway.New(gateway.Config{
+		Registry: reg, Vault: cached, Authorizer: keys, Receipts: ledger, Limiter: limiter,
+		Logger: slog.New(slog.NewJSONHandler(benchmarkLogWriter{b}, &slog.HandlerOptions{Level: slog.LevelInfo})),
+	})
+	b.Cleanup(handler.CloseIdleConnections)
+	server := httptest.NewServer(handler)
+	b.Cleanup(server.Close)
+	transport := &http.Transport{
+		MaxIdleConns: concurrency, MaxIdleConnsPerHost: concurrency, MaxConnsPerHost: concurrency,
+	}
+	b.Cleanup(transport.CloseIdleConnections)
+	return &stack{
+		db: database, ledger: ledger, client: &http.Client{Transport: transport, Timeout: 10 * time.Second},
+		url: server.URL + "/v1/act", key: plaintext, upstream: timings,
+	}
+}
+
+type sample struct {
+	total       time.Duration
+	upstream    time.Duration
+	dispatchLag time.Duration
+}
+
+func (s *stack) act(ctx context.Context, worker int, body string) (sample, error) {
+	return s.actAt(ctx, worker, body, time.Time{})
+}
+
+func (s *stack) actAt(ctx context.Context, worker int, body string, scheduled time.Time) (sample, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.url, strings.NewReader(body))
+	if err != nil {
+		return sample{}, err
+	}
+	req.Header.Set("Authorization", "Bearer "+s.key)
+	req.Header.Set("Content-Type", "application/json")
+	start := time.Now()
+	resp, err := s.client.Do(req)
+	if err != nil {
+		return sample{}, err
+	}
+	data, err := io.ReadAll(resp.Body)
+	resp.Body.Close()
+	finished := time.Now()
+	total := finished.Sub(start)
+	if err != nil {
+		return sample{}, err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return sample{}, fmt.Errorf("act status %d: %s", resp.StatusCode, data)
+	}
+	var envelope struct {
+		Status int `json:"status"`
+		Body   struct {
+			OK bool `json:"ok"`
+		} `json:"body"`
+	}
+	if err := json.Unmarshal(data, &envelope); err != nil {
+		return sample{}, err
+	}
+	if envelope.Status != http.StatusOK || !envelope.Body.OK {
+		return sample{}, fmt.Errorf("unexpected act response: %s", data)
+	}
+	select {
+	case duration := <-s.upstream[worker]:
+		if duration > total {
+			return sample{}, fmt.Errorf("upstream time %s exceeds total %s", duration, total)
+		}
+		return timedSample(scheduled, start, finished, duration), nil
+	case <-ctx.Done():
+		return sample{}, ctx.Err()
+	}
+}
+
+func timedSample(scheduled, started, finished time.Time, upstream time.Duration) sample {
+	if scheduled.IsZero() {
+		scheduled = started
+	}
+	return sample{
+		total: finished.Sub(scheduled), upstream: upstream, dispatchLag: started.Sub(scheduled),
+	}
+}
+
+func (s *stack) run(count, concurrency int, samples []sample) error {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	errors := make(chan error, concurrency)
+	start := make(chan struct{})
+	var ready, done sync.WaitGroup
+	for worker := range min(count, concurrency) {
+		ready.Add(1)
+		done.Add(1)
+		go func() {
+			defer done.Done()
+			body := fmt.Sprintf(`{"service":"mock","action":"echo","on_behalf_of":"bench-user","params":{"worker":%d}}`, worker)
+			ready.Done()
+			<-start
+			for i := worker; i < count; i += concurrency {
+				result, err := s.act(ctx, worker, body)
+				if err != nil {
+					errors <- err
+					cancel()
+					return
+				}
+				if samples != nil {
+					samples[i] = result
+				}
+			}
+		}()
+	}
+	ready.Wait()
+	close(start)
+	done.Wait()
+	close(errors)
+	for err := range errors {
+		return err
+	}
+	return nil
+}
+
+func BenchmarkHandleActE2E(b *testing.B) {
+	if runtime.GOMAXPROCS(0) != 4 {
+		b.Fatal("run with GOMAXPROCS=4 for the Phase 0 comparison")
+	}
+	for _, delay := range []time.Duration{0, 5 * time.Millisecond} {
+		b.Run("delay="+delay.String(), func(b *testing.B) {
+			for _, concurrency := range []int{1, 16, 64} {
+				b.Run(fmt.Sprintf("c=%d", concurrency), func(b *testing.B) {
+					benchmarkAct(b, concurrency, delay)
+				})
+			}
+		})
+	}
+}
+
+func benchmarkAct(b *testing.B, concurrency int, delay time.Duration) {
+	s := newStack(b, concurrency, delay)
+	must(b, s.run(warmupRequests, concurrency, nil))
+	samples := make([]sample, b.N)
+	b.ResetTimer()
+	start := time.Now()
+	err := s.run(b.N, concurrency, samples)
+	elapsed := time.Since(start)
+	b.StopTimer()
+	must(b, err)
+	s.checkReceipts(b, warmupRequests+b.N)
+	reportSamples(b, samples, elapsed)
+}
+
+func (s *stack) checkReceipts(b *testing.B, expected int) {
+	b.Helper()
+	var count, invalid int
+	must(b, s.db.QueryRow(`SELECT COUNT(*), COALESCE(SUM(
+		CASE WHEN status_code != 200 OR policy_decision != 'allow' OR error_code != ''
+		OR length(signature) != 64 THEN 1 ELSE 0 END), 0) FROM receipts`).Scan(&count, &invalid))
+	head, _, err := s.ledger.Head(context.Background())
+	must(b, err)
+	if count != expected || head != uint64(count) || invalid != 0 {
+		b.Fatalf("receipt mismatch: count=%d head=%d invalid=%d expected=%d", count, head, invalid, expected)
+	}
+}
+
+func reportSamples(b *testing.B, samples []sample, elapsed time.Duration) {
+	b.Helper()
+	overheads := make([]time.Duration, b.N)
+	totals := make([]time.Duration, b.N)
+	var upstreamTotal time.Duration
+	for i, result := range samples {
+		overheads[i] = result.total - result.upstream
+		totals[i] = result.total
+		upstreamTotal += result.upstream
+	}
+	slices.Sort(overheads)
+	slices.Sort(totals)
+	for _, p := range []float64{50, 90, 99, 99.9} {
+		b.ReportMetric(float64(percentile(overheads, p))/float64(time.Microsecond), fmt.Sprintf("p%g-overhead-us", p))
+	}
+	b.ReportMetric(float64(percentile(totals, 99))/float64(time.Microsecond), "p99-total-us")
+	b.ReportMetric(float64(upstreamTotal)/float64(b.N)/float64(time.Microsecond), "upstream-mean-us")
+	b.ReportMetric(float64(b.N)/elapsed.Seconds(), "req/s")
+}
+
+// percentile uses the nearest rank. Subtract upstream time before sorting, never between independently sorted percentiles.
+func percentile(sorted []time.Duration, p float64) time.Duration {
+	return sorted[max(0, int(math.Ceil(p*float64(len(sorted))/100))-1)]
+}
+
+func must(b *testing.B, err error) {
+	b.Helper()
+	if err != nil {
+		b.Fatal(err)
+	}
+}
+
+func TestPercentile(t *testing.T) {
+	samples := make([]time.Duration, 1000)
+	for i := range samples {
+		samples[i] = time.Duration(i + 1)
+	}
+	for _, p := range []float64{50, 90, 99, 99.9} {
+		if got, want := percentile(samples, p), time.Duration(math.Round(p*10)); got != want {
+			t.Errorf("p%g: got %d, want %d", p, got, want)
+		}
+	}
+	if got := percentile([]time.Duration{42}, 99.9); got != 42 {
+		t.Errorf("single sample: got %d, want 42", got)
+	}
+}