tests: integration suite

integration/README.md

@@ -0,0 +1,72 @@
+# Integration Tests
+
+`integration` owns only true inter-service black-box tests.
+Each suite must raise real service processes, speak only over public HTTP/gRPC/Redis contracts, and avoid imports from `internal/...` packages of tested services.
+
+## Layout
+
+```text
+integration/
+├── README.md
+├── go.mod
+├── gatewayauthsession/
+│   ├── harness_test.go
+│   └── gateway_authsession_test.go
+└── internal/
+    ├── contracts/
+    │   └── gatewayv1/
+    │       └── contract.go
+    └── harness/
+        ├── binary.go
+        ├── keys.go
+        ├── mail_stub.go
+        ├── process.go
+        └── user_stub.go
+```
+
+## Rules
+
+- Keep suites black-box. Do not import `galaxy/gateway/internal/...`, `galaxy/authsession/internal/...`, or any other service-owned internal package.
+- Start real binaries from `cmd/...` and talk to them only through their published HTTP, gRPC, and Redis contracts.
+- Put boundary-specific orchestration and assertions into the owning suite package, not into shared helpers.
+- Put only generic process/runtime utilities into `internal/harness`.
+- Put only public-contract helpers into `internal/contracts/...`.
+
+## Current Boundary Suites
+
+- `gatewayauthsession` verifies the integration boundary between real `Edge Gateway` and real `Auth / Session Service`.
+
+The current fast suite uses one isolated `miniredis` instance plus external stateful HTTP stubs for mail and user services.
+
+## Running
+
+Run from the module directory:
+
+```bash
+cd integration
+go test ./gatewayauthsession/...
+```
+
+Useful regression commands after boundary changes:
+
+```bash
+go test ./gatewayauthsession/...
+cd ../gateway && go test ./...
+cd ../authsession && go test ./... -run GatewayCompatibility
+```
+
+Do not use `go test ./...` from the repository root. The repository is organized through `go.work`, so verification should stay module-scoped.
+
+## Adding A New Boundary Suite
+
+1. Create `integration/<boundary>/` for the new inter-service boundary.
+2. Keep suite-local fixtures, scenario helpers, and assertion helpers inside that package.
+3. Reuse `internal/harness` only for generic concerns such as binary build/run, ports, keys, Redis, and shared external stubs.
+4. Add new helpers to `internal/contracts/<contract>/` only when they describe a reusable public wire contract.
+5. Prefer fast deterministic infrastructure by default: in-memory test doubles, `httptest` stubs, and `miniredis`.
+
+## Future Real Redis Smoke Suites
+
+Fast suites stay on `miniredis` by default.
+When a boundary needs one real Redis smoke suite later, keep it in the same boundary package and gate it explicitly with environment-driven configuration such as `INTEGRATION_REAL_REDIS_ADDR`.
+That smoke suite should complement, not replace, the deterministic `miniredis` coverage.

integration/gatewayauthsession/gateway_authsession_test.go

@@ -0,0 +1,265 @@
+package gatewayauthsession_test
+
+import (
+	"context"
+	"crypto/ed25519"
+	"encoding/base64"
+	"net/http"
+	"testing"
+	"time"
+
+	"galaxy/integration/internal/harness"
+
+	gatewayv1 "galaxy/gateway/proto/galaxy/gateway/v1"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+func TestGatewayAuthSessionSendEmailCodeReachesAuthsessionMailDelivery(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/send-email-code", map[string]string{
+		"email": testEmail,
+	})
+	require.Equal(t, http.StatusOK, response.StatusCode)
+
+	var body struct {
+		ChallengeID string `json:"challenge_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(response.Body), &body))
+	require.NotEmpty(t, body.ChallengeID)
+
+	deliveries := h.mailStub.RecordedDeliveries()
+	require.Len(t, deliveries, 1)
+	require.Equal(t, testEmail, deliveries[0].Email)
+	require.Len(t, deliveries[0].Code, 6)
+}
+
+func TestGatewayAuthSessionConfirmCreatesProjectionAndAllowsSubscribeEvents(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	clientPrivateKey := newClientPrivateKey("confirm-projection")
+	challengeID, code := h.sendChallenge(t, testEmail)
+
+	response := h.confirmCode(t, challengeID, code, clientPrivateKey)
+	require.Equal(t, http.StatusOK, response.StatusCode)
+
+	var confirmBody struct {
+		DeviceSessionID string `json:"device_session_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(response.Body), &confirmBody))
+	require.NotEmpty(t, confirmBody.DeviceSessionID)
+
+	record := h.readGatewaySessionRecord(t, confirmBody.DeviceSessionID)
+	require.Equal(t, gatewaySessionRecord{
+		DeviceSessionID: confirmBody.DeviceSessionID,
+		UserID:          "user-1",
+		ClientPublicKey: base64.StdEncoding.EncodeToString(clientPrivateKey.Public().(ed25519.PublicKey)),
+		Status:          "active",
+	}, record)
+
+	ensureCalls := h.userStub.EnsureCalls()
+	require.Len(t, ensureCalls, 1)
+	require.Equal(t, testEmail, ensureCalls[0].Email)
+	require.Equal(t, "en", ensureCalls[0].PreferredLanguage)
+	require.Equal(t, testTimeZone, ensureCalls[0].TimeZone)
+
+	conn := h.dialGateway(t)
+	client := gatewayv1.NewEdgeGatewayClient(conn)
+
+	stream, err := client.SubscribeEvents(context.Background(), newSubscribeEventsRequest(confirmBody.DeviceSessionID, "request-bootstrap", clientPrivateKey))
+	require.NoError(t, err)
+
+	event, err := stream.Recv()
+	require.NoError(t, err)
+	assertBootstrapEvent(t, event, h.responseSignerPublicKey, "request-bootstrap")
+}
+
+func TestGatewayAuthSessionRepeatedConfirmReturnsSameSessionID(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	clientPrivateKey := newClientPrivateKey("repeated-confirm")
+	challengeID, code := h.sendChallenge(t, testEmail)
+
+	first := h.confirmCode(t, challengeID, code, clientPrivateKey)
+	second := h.confirmCode(t, challengeID, code, clientPrivateKey)
+	require.Equal(t, http.StatusOK, first.StatusCode)
+	require.Equal(t, http.StatusOK, second.StatusCode)
+
+	var firstBody struct {
+		DeviceSessionID string `json:"device_session_id"`
+	}
+	var secondBody struct {
+		DeviceSessionID string `json:"device_session_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(first.Body), &firstBody))
+	require.NoError(t, decodeStrictJSONPayload([]byte(second.Body), &secondBody))
+	require.Equal(t, firstBody.DeviceSessionID, secondBody.DeviceSessionID)
+}
+
+func TestGatewayAuthSessionInvalidClientPublicKeyPassesThroughUnchanged(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	challengeID, _ := h.sendChallenge(t, testEmail)
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/confirm-email-code", map[string]string{
+		"challenge_id":      challengeID,
+		"code":              "123456",
+		"client_public_key": "invalid",
+		"time_zone":         testTimeZone,
+	})
+
+	require.Equal(t, http.StatusBadRequest, response.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"invalid_client_public_key","message":"client_public_key is not a valid base64-encoded raw 32-byte Ed25519 public key"}}`, response.Body)
+}
+
+func TestGatewayAuthSessionChallengeNotFoundPassesThroughUnchanged(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	response := h.confirmCode(t, "missing-challenge", "123456", newClientPrivateKey("missing-challenge"))
+
+	require.Equal(t, http.StatusNotFound, response.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"challenge_not_found","message":"challenge not found"}}`, response.Body)
+}
+
+func TestGatewayAuthSessionInvalidCodePassesThroughUnchanged(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	clientPrivateKey := newClientPrivateKey("invalid-code")
+	challengeID, code := h.sendChallenge(t, testEmail)
+	invalidCode := "000000"
+	if code == invalidCode {
+		invalidCode = "111111"
+	}
+
+	response := h.confirmCode(t, challengeID, invalidCode, clientPrivateKey)
+
+	require.Equal(t, http.StatusBadRequest, response.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"invalid_code","message":"confirmation code is invalid"}}`, response.Body)
+}
+
+func TestGatewayAuthSessionBlockedSendRemainsSuccessShapedWithoutDelivery(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+	h.userStub.SeedBlockedEmail(testEmail, "policy_blocked")
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/send-email-code", map[string]string{
+		"email": testEmail,
+	})
+
+	require.Equal(t, http.StatusOK, response.StatusCode)
+	var body struct {
+		ChallengeID string `json:"challenge_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(response.Body), &body))
+	require.NotEmpty(t, body.ChallengeID)
+	require.Empty(t, h.mailStub.RecordedDeliveries())
+}
+
+func TestGatewayAuthSessionSessionLimitExceededPassesThroughUnchanged(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+	h.seedSessionLimit(t, 1)
+
+	firstClientPrivateKey := newClientPrivateKey("session-limit-first")
+	firstChallengeID, firstCode := h.sendChallenge(t, testEmail)
+	firstConfirm := h.confirmCode(t, firstChallengeID, firstCode, firstClientPrivateKey)
+	require.Equal(t, http.StatusOK, firstConfirm.StatusCode)
+
+	const secondEmail = "pilot-second@example.com"
+	h.userStub.SeedExisting(secondEmail, "user-1")
+
+	secondClientPrivateKey := newClientPrivateKey("session-limit-second")
+	secondChallengeID, secondCode := h.sendChallenge(t, secondEmail)
+	secondConfirm := h.confirmCode(t, secondChallengeID, secondCode, secondClientPrivateKey)
+
+	require.Equal(t, http.StatusConflict, secondConfirm.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"session_limit_exceeded","message":"active session limit would be exceeded"}}`, secondConfirm.Body)
+}
+
+func TestGatewayAuthSessionRevokeClosesPushStreamAndRejectsReopen(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{})
+
+	clientPrivateKey := newClientPrivateKey("revoke")
+	challengeID, code := h.sendChallenge(t, testEmail)
+	confirm := h.confirmCode(t, challengeID, code, clientPrivateKey)
+	require.Equal(t, http.StatusOK, confirm.StatusCode)
+
+	var confirmBody struct {
+		DeviceSessionID string `json:"device_session_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(confirm.Body), &confirmBody))
+
+	conn := h.dialGateway(t)
+	client := gatewayv1.NewEdgeGatewayClient(conn)
+
+	stream, err := client.SubscribeEvents(context.Background(), newSubscribeEventsRequest(confirmBody.DeviceSessionID, "request-revoke", clientPrivateKey))
+	require.NoError(t, err)
+
+	event, err := stream.Recv()
+	require.NoError(t, err)
+	assertBootstrapEvent(t, event, h.responseSignerPublicKey, "request-revoke")
+
+	revokeResponse := postJSONValue(t, h.authsessionInternalURL+"/api/v1/internal/sessions/"+confirmBody.DeviceSessionID+"/revoke", map[string]any{
+		"reason_code": "admin_revoke",
+		"actor": map[string]string{
+			"type": "system",
+		},
+	})
+	require.Equal(t, http.StatusOK, revokeResponse.StatusCode)
+
+	recvErrCh := make(chan error, 1)
+	go func() {
+		_, recvErr := stream.Recv()
+		recvErrCh <- recvErr
+	}()
+
+	select {
+	case recvErr := <-recvErrCh:
+		require.Equal(t, codes.FailedPrecondition, status.Code(recvErr))
+		require.Equal(t, "device session is revoked", status.Convert(recvErr).Message())
+	case <-time.After(5 * time.Second):
+		t.Fatal("gateway stream did not close after authsession revoke")
+	}
+
+	reopened, err := client.SubscribeEvents(context.Background(), newSubscribeEventsRequest(confirmBody.DeviceSessionID, "request-reopen", clientPrivateKey))
+	if err == nil {
+		_, err = reopened.Recv()
+	}
+
+	require.Equal(t, codes.FailedPrecondition, status.Code(err))
+	require.Equal(t, "device session is revoked", status.Convert(err).Message())
+}
+
+func TestGatewayAuthSessionGatewayTimeoutMappingOverridesAuthsessionMessage(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{
+		gatewayAuthUpstreamTimeout:   50 * time.Millisecond,
+		authsessionPublicHTTPTimeout: time.Second,
+		authsessionMailBehavior: harness.MailBehavior{
+			Delay: 200 * time.Millisecond,
+		},
+	})
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/send-email-code", map[string]string{
+		"email": testEmail,
+	})
+
+	require.Equal(t, http.StatusServiceUnavailable, response.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"service_unavailable","message":"auth service is unavailable"}}`, response.Body)
+}
+
+func TestGatewayAuthSessionAuthsessionServiceUnavailablePassesThroughUnchanged(t *testing.T) {
+	h := newGatewayAuthSessionHarness(t, gatewayAuthSessionOptions{
+		authsessionMailBehavior: harness.MailBehavior{
+			StatusCode: http.StatusServiceUnavailable,
+			RawBody:    `{"error":"mail backend unavailable"}`,
+		},
+	})
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/send-email-code", map[string]string{
+		"email": testEmail,
+	})
+
+	require.Equal(t, http.StatusServiceUnavailable, response.StatusCode)
+	require.JSONEq(t, `{"error":{"code":"service_unavailable","message":"service is unavailable"}}`, response.Body)
+}

integration/gatewayauthsession/harness_test.go

@@ -0,0 +1,406 @@
+package gatewayauthsession_test
+
+import (
+	"bytes"
+	"context"
+	"crypto/ed25519"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"path/filepath"
+	"testing"
+	"time"
+
+	contractsgatewayv1 "galaxy/integration/internal/contracts/gatewayv1"
+	"galaxy/integration/internal/harness"
+
+	gatewayv1 "galaxy/gateway/proto/galaxy/gateway/v1"
+
+	"github.com/redis/go-redis/v9"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+)
+
+const (
+	testEmail    = "pilot@example.com"
+	testTimeZone = "Europe/Kaliningrad"
+
+	defaultGatewayAuthUpstreamTimeout     = 500 * time.Millisecond
+	defaultAuthsessionPublicHTTPTimeout   = time.Second
+	defaultAuthsessionInternalHTTPTimeout = time.Second
+	defaultAuthsessionDependencyTimeout   = time.Second
+)
+
+type gatewayAuthSessionOptions struct {
+	gatewayAuthUpstreamTimeout   time.Duration
+	authsessionPublicHTTPTimeout time.Duration
+	authsessionMailBehavior      harness.MailBehavior
+}
+
+type gatewayAuthSessionHarness struct {
+	redis *redis.Client
+
+	mailStub *harness.MailStub
+	userStub *harness.UserStub
+
+	authsessionPublicURL   string
+	authsessionInternalURL string
+	gatewayPublicURL       string
+	gatewayGRPCAddr        string
+
+	responseSignerPublicKey ed25519.PublicKey
+
+	gatewayProcess     *harness.Process
+	authsessionProcess *harness.Process
+}
+
+func newGatewayAuthSessionHarness(t *testing.T, opts gatewayAuthSessionOptions) *gatewayAuthSessionHarness {
+	t.Helper()
+
+	if opts.gatewayAuthUpstreamTimeout <= 0 {
+		opts.gatewayAuthUpstreamTimeout = defaultGatewayAuthUpstreamTimeout
+	}
+	if opts.authsessionPublicHTTPTimeout <= 0 {
+		opts.authsessionPublicHTTPTimeout = defaultAuthsessionPublicHTTPTimeout
+	}
+
+	redisServer := harness.StartMiniredis(t)
+	redisClient := redis.NewClient(&redis.Options{
+		Addr:            redisServer.Addr(),
+		Protocol:        2,
+		DisableIdentity: true,
+	})
+	t.Cleanup(func() {
+		require.NoError(t, redisClient.Close())
+	})
+
+	mailStub := harness.NewMailStub(t)
+	mailStub.SetBehavior(opts.authsessionMailBehavior)
+
+	userStub := harness.NewUserStub(t)
+
+	responseSignerPath, responseSignerPublicKey := harness.WriteResponseSignerPEM(t, t.Name())
+	authsessionPublicAddr := harness.FreeTCPAddress(t)
+	authsessionInternalAddr := harness.FreeTCPAddress(t)
+	gatewayPublicAddr := harness.FreeTCPAddress(t)
+	gatewayGRPCAddr := harness.FreeTCPAddress(t)
+
+	authsessionBinary := harness.BuildBinary(t, "authsession", "./authsession/cmd/authsession")
+	gatewayBinary := harness.BuildBinary(t, "gateway", "./gateway/cmd/gateway")
+
+	authsessionEnv := map[string]string{
+		"AUTHSESSION_LOG_LEVEL":                              "info",
+		"AUTHSESSION_PUBLIC_HTTP_ADDR":                       authsessionPublicAddr,
+		"AUTHSESSION_PUBLIC_HTTP_REQUEST_TIMEOUT":            opts.authsessionPublicHTTPTimeout.String(),
+		"AUTHSESSION_INTERNAL_HTTP_ADDR":                     authsessionInternalAddr,
+		"AUTHSESSION_INTERNAL_HTTP_REQUEST_TIMEOUT":          defaultAuthsessionInternalHTTPTimeout.String(),
+		"AUTHSESSION_REDIS_ADDR":                             redisServer.Addr(),
+		"AUTHSESSION_USER_SERVICE_MODE":                      "rest",
+		"AUTHSESSION_USER_SERVICE_BASE_URL":                  userStub.BaseURL(),
+		"AUTHSESSION_USER_SERVICE_REQUEST_TIMEOUT":           defaultAuthsessionDependencyTimeout.String(),
+		"AUTHSESSION_MAIL_SERVICE_MODE":                      "rest",
+		"AUTHSESSION_MAIL_SERVICE_BASE_URL":                  mailStub.BaseURL(),
+		"AUTHSESSION_MAIL_SERVICE_REQUEST_TIMEOUT":           defaultAuthsessionDependencyTimeout.String(),
+		"AUTHSESSION_REDIS_GATEWAY_SESSION_CACHE_KEY_PREFIX": "gateway:session:",
+		"AUTHSESSION_REDIS_GATEWAY_SESSION_EVENTS_STREAM":    "gateway:session_events",
+		"OTEL_TRACES_EXPORTER":                               "none",
+		"OTEL_METRICS_EXPORTER":                              "none",
+	}
+	authsessionProcess := harness.StartProcess(t, "authsession", authsessionBinary, authsessionEnv)
+	waitForAuthsessionPublicReady(t, authsessionProcess, "http://"+authsessionPublicAddr)
+	waitForAuthsessionInternalReady(t, authsessionProcess, "http://"+authsessionInternalAddr)
+
+	gatewayEnv := map[string]string{
+		"GATEWAY_LOG_LEVEL":                                                              "info",
+		"GATEWAY_PUBLIC_HTTP_ADDR":                                                       gatewayPublicAddr,
+		"GATEWAY_AUTHENTICATED_GRPC_ADDR":                                                gatewayGRPCAddr,
+		"GATEWAY_SESSION_CACHE_REDIS_ADDR":                                               redisServer.Addr(),
+		"GATEWAY_SESSION_CACHE_REDIS_KEY_PREFIX":                                         "gateway:session:",
+		"GATEWAY_SESSION_EVENTS_REDIS_STREAM":                                            "gateway:session_events",
+		"GATEWAY_CLIENT_EVENTS_REDIS_STREAM":                                             "gateway:client_events",
+		"GATEWAY_REPLAY_REDIS_KEY_PREFIX":                                                "gateway:replay:",
+		"GATEWAY_RESPONSE_SIGNER_PRIVATE_KEY_PEM_PATH":                                   filepath.Clean(responseSignerPath),
+		"GATEWAY_AUTH_SERVICE_BASE_URL":                                                  "http://" + authsessionPublicAddr,
+		"GATEWAY_PUBLIC_AUTH_UPSTREAM_TIMEOUT":                                           opts.gatewayAuthUpstreamTimeout.String(),
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_PUBLIC_AUTH_RATE_LIMIT_REQUESTS":                 "100",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_PUBLIC_AUTH_RATE_LIMIT_WINDOW":                   "1s",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_PUBLIC_AUTH_RATE_LIMIT_BURST":                    "100",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_SEND_EMAIL_CODE_IDENTITY_RATE_LIMIT_REQUESTS":    "100",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_SEND_EMAIL_CODE_IDENTITY_RATE_LIMIT_WINDOW":      "1s",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_SEND_EMAIL_CODE_IDENTITY_RATE_LIMIT_BURST":       "100",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_CONFIRM_EMAIL_CODE_IDENTITY_RATE_LIMIT_REQUESTS": "100",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_CONFIRM_EMAIL_CODE_IDENTITY_RATE_LIMIT_WINDOW":   "1s",
+		"GATEWAY_PUBLIC_HTTP_ANTI_ABUSE_CONFIRM_EMAIL_CODE_IDENTITY_RATE_LIMIT_BURST":    "100",
+		"OTEL_TRACES_EXPORTER":                                                           "none",
+		"OTEL_METRICS_EXPORTER":                                                          "none",
+	}
+	gatewayProcess := harness.StartProcess(t, "gateway", gatewayBinary, gatewayEnv)
+	harness.WaitForHTTPStatus(t, gatewayProcess, "http://"+gatewayPublicAddr+"/healthz", http.StatusOK)
+	harness.WaitForTCP(t, gatewayProcess, gatewayGRPCAddr)
+
+	return &gatewayAuthSessionHarness{
+		redis:                   redisClient,
+		mailStub:                mailStub,
+		userStub:                userStub,
+		authsessionPublicURL:    "http://" + authsessionPublicAddr,
+		authsessionInternalURL:  "http://" + authsessionInternalAddr,
+		gatewayPublicURL:        "http://" + gatewayPublicAddr,
+		gatewayGRPCAddr:         gatewayGRPCAddr,
+		responseSignerPublicKey: responseSignerPublicKey,
+		gatewayProcess:          gatewayProcess,
+		authsessionProcess:      authsessionProcess,
+	}
+}
+
+func (h *gatewayAuthSessionHarness) dialGateway(t *testing.T) *grpc.ClientConn {
+	t.Helper()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	conn, err := grpc.DialContext(
+		ctx,
+		h.gatewayGRPCAddr,
+		grpc.WithTransportCredentials(insecure.NewCredentials()),
+		grpc.WithBlock(),
+	)
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		require.NoError(t, conn.Close())
+	})
+
+	return conn
+}
+
+func (h *gatewayAuthSessionHarness) seedSessionLimit(t *testing.T, limit int) {
+	t.Helper()
+
+	require.NoError(t, h.redis.Set(context.Background(), "authsession:config:active-session-limit", fmt.Sprint(limit), 0).Err())
+}
+
+func (h *gatewayAuthSessionHarness) readGatewaySessionRecord(t *testing.T, deviceSessionID string) gatewaySessionRecord {
+	t.Helper()
+
+	payload, err := h.redis.Get(context.Background(), "gateway:session:"+deviceSessionID).Bytes()
+	require.NoError(t, err)
+
+	var record gatewaySessionRecord
+	require.NoError(t, decodeStrictJSONPayload(payload, &record))
+	return record
+}
+
+func (h *gatewayAuthSessionHarness) sendChallenge(t *testing.T, email string) (string, string) {
+	t.Helper()
+
+	response := postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/send-email-code", map[string]string{
+		"email": email,
+	})
+	require.Equal(t, http.StatusOK, response.StatusCode)
+
+	var body struct {
+		ChallengeID string `json:"challenge_id"`
+	}
+	require.NoError(t, decodeStrictJSONPayload([]byte(response.Body), &body))
+
+	deliveries := h.mailStub.RecordedDeliveries()
+	require.NotEmpty(t, deliveries)
+	return body.ChallengeID, deliveries[len(deliveries)-1].Code
+}
+
+func (h *gatewayAuthSessionHarness) confirmCode(t *testing.T, challengeID string, code string, clientPrivateKey ed25519.PrivateKey) httpResponse {
+	t.Helper()
+
+	return postJSONValue(t, h.gatewayPublicURL+"/api/v1/public/auth/confirm-email-code", map[string]string{
+		"challenge_id":      challengeID,
+		"code":              code,
+		"client_public_key": encodePublicKey(clientPrivateKey.Public().(ed25519.PublicKey)),
+		"time_zone":         testTimeZone,
+	})
+}
+
+func newClientPrivateKey(label string) ed25519.PrivateKey {
+	seed := sha256.Sum256([]byte("galaxy-integration-gateway-authsession-client-" + label))
+	return ed25519.NewKeyFromSeed(seed[:])
+}
+
+func newSubscribeEventsRequest(deviceSessionID string, requestID string, clientPrivateKey ed25519.PrivateKey) *gatewayv1.SubscribeEventsRequest {
+	payloadHash := contractsgatewayv1.ComputePayloadHash(nil)
+
+	request := &gatewayv1.SubscribeEventsRequest{
+		ProtocolVersion: contractsgatewayv1.ProtocolVersionV1,
+		DeviceSessionId: deviceSessionID,
+		MessageType:     contractsgatewayv1.SubscribeMessageType,
+		TimestampMs:     time.Now().UnixMilli(),
+		RequestId:       requestID,
+		PayloadHash:     payloadHash,
+		TraceId:         "trace-" + requestID,
+	}
+	request.Signature = contractsgatewayv1.SignRequest(clientPrivateKey, contractsgatewayv1.RequestSigningFields{
+		ProtocolVersion: request.GetProtocolVersion(),
+		DeviceSessionID: request.GetDeviceSessionId(),
+		MessageType:     request.GetMessageType(),
+		TimestampMS:     request.GetTimestampMs(),
+		RequestID:       request.GetRequestId(),
+		PayloadHash:     request.GetPayloadHash(),
+	})
+	return request
+}
+
+func assertBootstrapEvent(t *testing.T, event *gatewayv1.GatewayEvent, responseSignerPublicKey ed25519.PublicKey, wantRequestID string) {
+	t.Helper()
+
+	require.Equal(t, contractsgatewayv1.ServerTimeEventType, event.GetEventType())
+	require.Equal(t, wantRequestID, event.GetEventId())
+	require.Equal(t, wantRequestID, event.GetRequestId())
+	require.NoError(t, contractsgatewayv1.VerifyPayloadHash(event.GetPayloadBytes(), event.GetPayloadHash()))
+	require.NoError(t, contractsgatewayv1.VerifyEventSignature(responseSignerPublicKey, event.GetSignature(), contractsgatewayv1.EventSigningFields{
+		EventType:   event.GetEventType(),
+		EventID:     event.GetEventId(),
+		TimestampMS: event.GetTimestampMs(),
+		RequestID:   event.GetRequestId(),
+		TraceID:     event.GetTraceId(),
+		PayloadHash: event.GetPayloadHash(),
+	}))
+}
+
+type httpResponse struct {
+	StatusCode int
+	Body       string
+	Header     http.Header
+}
+
+type gatewaySessionRecord struct {
+	DeviceSessionID string `json:"device_session_id"`
+	UserID          string `json:"user_id"`
+	ClientPublicKey string `json:"client_public_key"`
+	Status          string `json:"status"`
+	RevokedAtMS     *int64 `json:"revoked_at_ms,omitempty"`
+}
+
+func postJSONValue(t *testing.T, targetURL string, body any) httpResponse {
+	t.Helper()
+
+	payload, err := json.Marshal(body)
+	require.NoError(t, err)
+
+	request, err := http.NewRequest(http.MethodPost, targetURL, bytes.NewReader(payload))
+	require.NoError(t, err)
+	request.Header.Set("Content-Type", "application/json")
+
+	client := &http.Client{Timeout: 5 * time.Second}
+
+	response, err := client.Do(request)
+	require.NoError(t, err)
+	defer response.Body.Close()
+
+	responseBody, err := io.ReadAll(response.Body)
+	require.NoError(t, err)
+
+	return httpResponse{
+		StatusCode: response.StatusCode,
+		Body:       string(responseBody),
+		Header:     response.Header.Clone(),
+	}
+}
+
+func decodeStrictJSONPayload(payload []byte, target any) error {
+	decoder := json.NewDecoder(bytes.NewReader(payload))
+	decoder.DisallowUnknownFields()
+
+	if err := decoder.Decode(target); err != nil {
+		return err
+	}
+	if err := decoder.Decode(&struct{}{}); err != io.EOF {
+		if err == nil {
+			return fmt.Errorf("unexpected trailing JSON input")
+		}
+		return err
+	}
+
+	return nil
+}
+
+func encodePublicKey(publicKey ed25519.PublicKey) string {
+	return base64.StdEncoding.EncodeToString(publicKey)
+}
+
+func waitForAuthsessionPublicReady(t *testing.T, process *harness.Process, baseURL string) {
+	t.Helper()
+
+	client := &http.Client{Timeout: 250 * time.Millisecond}
+	deadline := time.Now().Add(10 * time.Second)
+
+	for time.Now().Before(deadline) {
+		response, err := postJSONValueMaybe(client, baseURL+"/api/v1/public/auth/send-email-code", map[string]string{
+			"email": "",
+		})
+		if err == nil && response.StatusCode == http.StatusBadRequest {
+			return
+		}
+
+		time.Sleep(25 * time.Millisecond)
+	}
+
+	t.Fatalf("wait for authsession public readiness: timeout\n%s", process.Logs())
+}
+
+func waitForAuthsessionInternalReady(t *testing.T, process *harness.Process, baseURL string) {
+	t.Helper()
+
+	client := &http.Client{Timeout: 250 * time.Millisecond}
+	deadline := time.Now().Add(10 * time.Second)
+
+	for time.Now().Before(deadline) {
+		request, err := http.NewRequest(http.MethodGet, baseURL+"/api/v1/internal/sessions/missing", nil)
+		if err != nil {
+			t.Fatalf("build authsession internal readiness request: %v", err)
+		}
+
+		response, err := client.Do(request)
+		if err == nil {
+			_, _ = io.Copy(io.Discard, response.Body)
+			response.Body.Close()
+			if response.StatusCode == http.StatusNotFound {
+				return
+			}
+		}
+
+		time.Sleep(25 * time.Millisecond)
+	}
+
+	t.Fatalf("wait for authsession internal readiness: timeout\n%s", process.Logs())
+}
+
+func postJSONValueMaybe(client *http.Client, targetURL string, body any) (httpResponse, error) {
+	payload, err := json.Marshal(body)
+	if err != nil {
+		return httpResponse{}, err
+	}
+
+	request, err := http.NewRequest(http.MethodPost, targetURL, bytes.NewReader(payload))
+	if err != nil {
+		return httpResponse{}, err
+	}
+	request.Header.Set("Content-Type", "application/json")
+
+	response, err := client.Do(request)
+	if err != nil {
+		return httpResponse{}, err
+	}
+	defer response.Body.Close()
+
+	responseBody, err := io.ReadAll(response.Body)
+	if err != nil {
+		return httpResponse{}, err
+	}
+
+	return httpResponse{
+		StatusCode: response.StatusCode,
+		Body:       string(responseBody),
+		Header:     response.Header.Clone(),
+	}, nil
+}

integration/go.mod

@@ -0,0 +1,31 @@
+module galaxy/integration
+
+go 1.26.0
+
+require (
+	github.com/alicebob/miniredis/v2 v2.37.0
+	github.com/redis/go-redis/v9 v9.18.0
+	github.com/stretchr/testify v1.11.1
+	google.golang.org/grpc v1.80.0
+)
+
+require (
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
+	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
+	github.com/kr/pretty v0.3.1 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
+	github.com/rogpeppe/go-internal v1.14.1 // indirect
+	github.com/yuin/gopher-lua v1.1.1 // indirect
+	go.opentelemetry.io/otel v1.42.0 // indirect
+	go.opentelemetry.io/otel/sdk/metric v1.42.0 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	golang.org/x/net v0.52.0 // indirect
+	golang.org/x/sys v0.42.0 // indirect
+	golang.org/x/text v0.35.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20260401024825-9d38bb4040a9 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
+	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

integration/go.sum

@@ -0,0 +1,57 @@
+github.com/alicebob/miniredis/v2 v2.37.0 h1:RheObYW32G1aiJIj81XVt78ZHJpHonHLHW7OLIshq68=
+github.com/alicebob/miniredis/v2 v2.37.0/go.mod h1:TcL7YfarKPGDAthEtl5NBeHZfeUQj6OXMm/+iu5cLMM=
+github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
+github.com/bsm/ginkgo/v2 v2.12.0/go.mod h1:SwYbGRRDovPVboqFv0tPTcG1sN61LM1Z4ARdbAV9g4c=
+github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
+github.com/bsm/gomega v1.27.10/go.mod h1:JyEr/xRbxbtgWNi8tIEVPUYZ5Dzef52k01W3YH0H+O0=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
+github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
+github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
+github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
+github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
+github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
+github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
+github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/klauspost/cpuid/v2 v2.3.0 h1:S4CRMLnYUhGeDFDqkGriYKdfoFlDnMtqTiI/sFzhA9Y=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
+github.com/redis/go-redis/v9 v9.18.0 h1:pMkxYPkEbMPwRdenAzUNyFNrDgHx9U+DrBabWNfSRQs=
+github.com/redis/go-redis/v9 v9.18.0/go.mod h1:k3ufPphLU5YXwNTUcCRXGxUoF1fqxnhFQmscfkCoDA0=
+github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+github.com/yuin/gopher-lua v1.1.1 h1:kYKnWBjvbNP4XLT3+bPEwAXJx262OhaHDWDVOPjL46M=
+github.com/yuin/gopher-lua v1.1.1/go.mod h1:GBR0iDaNXjAgGg9zfCvksxSRnQx76gclCIb7kdAd1Pw=
+github.com/zeebo/xxh3 v1.0.2 h1:xZmwmqxHZA8AI603jOQ0tMqmBr9lPeFwGg6d+xy9DC0=
+github.com/zeebo/xxh3 v1.0.2/go.mod h1:5NWz9Sef7zIDm2JHfFlcQvNekmcEl9ekUZQQKCYaDcA=
+go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
+go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
+go.opentelemetry.io/otel v1.42.0 h1:lSQGzTgVR3+sgJDAU/7/ZMjN9Z+vUip7leaqBKy4sho=
+go.opentelemetry.io/otel/metric v1.42.0 h1:2jXG+3oZLNXEPfNmnpxKDeZsFI5o4J+nz6xUlaFdF/4=
+go.opentelemetry.io/otel/sdk v1.42.0 h1:LyC8+jqk6UJwdrI/8VydAq/hvkFKNHZVIWuslJXYsDo=
+go.opentelemetry.io/otel/sdk/metric v1.42.0 h1:D/1QR46Clz6ajyZ3G8SgNlTJKBdGp84q9RKCAZ3YGuA=
+go.opentelemetry.io/otel/trace v1.42.0 h1:OUCgIPt+mzOnaUTpOQcBiM/PLQ/Op7oq6g4LenLmOYY=
+go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=
+go.uber.org/atomic v1.11.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
+golang.org/x/net v0.52.0 h1:He/TN1l0e4mmR3QqHMT2Xab3Aj3L9qjbhRm78/6jrW0=
+golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
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+gonum.org/v1/gonum v0.17.0 h1:VbpOemQlsSMrYmn7T2OUvQ4dqxQXU+ouZFQsZOx50z4=
+gonum.org/v1/gonum v0.17.0/go.mod h1:El3tOrEuMpv2UdMrbNlKEh9vd86bmQ6vqIcDwxEOc1E=
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+google.golang.org/grpc v1.80.0 h1:Xr6m2WmWZLETvUNvIUmeD5OAagMw3FiKmMlTdViWsHM=
+google.golang.org/grpc v1.80.0/go.mod h1:ho/dLnxwi3EDJA4Zghp7k2Ec1+c2jqup0bFkw07bwF4=
+google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
+google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

integration/internal/contracts/gatewayv1/contract.go

@@ -0,0 +1,184 @@
+// Package gatewayv1contract provides public-contract helpers for the gateway
+// v1 authenticated transport without importing service-internal packages.
+package gatewayv1contract
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"crypto/sha256"
+	"encoding/binary"
+	"errors"
+)
+
+const (
+	// ProtocolVersionV1 is the supported public protocol version literal.
+	ProtocolVersionV1 = "v1"
+
+	// SubscribeMessageType is the authenticated message type used to open the
+	// gateway push stream.
+	SubscribeMessageType = "gateway.subscribe"
+
+	// ServerTimeEventType is the bootstrap event type emitted by the gateway
+	// immediately after a push stream is opened.
+	ServerTimeEventType = "gateway.server_time"
+
+	requestDomainMarkerV1 = "galaxy-request-v1"
+	eventDomainMarkerV1   = "galaxy-event-v1"
+)
+
+var (
+	// ErrInvalidPayloadHash reports that payloadHash is not a raw SHA-256
+	// digest.
+	ErrInvalidPayloadHash = errors.New("payload_hash must be a 32-byte SHA-256 digest")
+
+	// ErrPayloadHashMismatch reports that payloadHash does not match
+	// payloadBytes.
+	ErrPayloadHashMismatch = errors.New("payload_hash does not match payload_bytes")
+
+	// ErrInvalidEventSignature reports that one gateway event signature is not
+	// a raw Ed25519 signature for the canonical event signing input.
+	ErrInvalidEventSignature = errors.New("invalid event signature")
+)
+
+// RequestSigningFields stores the canonical public request fields bound into
+// one client signature input.
+type RequestSigningFields struct {
+	// ProtocolVersion identifies the gateway transport envelope version.
+	ProtocolVersion string
+
+	// DeviceSessionID identifies the authenticated device session bound to the
+	// request.
+	DeviceSessionID string
+
+	// MessageType is the stable authenticated gateway message type.
+	MessageType string
+
+	// TimestampMS carries the client request timestamp in milliseconds.
+	TimestampMS int64
+
+	// RequestID is the transport correlation and anti-replay identifier.
+	RequestID string
+
+	// PayloadHash stores the raw SHA-256 digest of PayloadBytes.
+	PayloadHash []byte
+}
+
+// EventSigningFields stores the canonical public stream-event fields bound
+// into one gateway event signature input.
+type EventSigningFields struct {
+	// EventType identifies the stable client-facing event category.
+	EventType string
+
+	// EventID is the stable event correlation identifier.
+	EventID string
+
+	// TimestampMS carries the gateway event timestamp in milliseconds.
+	TimestampMS int64
+
+	// RequestID optionally correlates the event to the opening client request.
+	RequestID string
+
+	// TraceID optionally carries the client-supplied trace correlation value.
+	TraceID string
+
+	// PayloadHash stores the raw SHA-256 digest of PayloadBytes.
+	PayloadHash []byte
+}
+
+// ComputePayloadHash returns the canonical raw SHA-256 digest for payloadBytes.
+func ComputePayloadHash(payloadBytes []byte) []byte {
+	sum := sha256.Sum256(payloadBytes)
+	return bytes.Clone(sum[:])
+}
+
+// VerifyPayloadHash reports whether payloadHash matches payloadBytes under the
+// public gateway payload-hash contract.
+func VerifyPayloadHash(payloadBytes, payloadHash []byte) error {
+	if len(payloadHash) != sha256.Size {
+		return ErrInvalidPayloadHash
+	}
+
+	sum := sha256.Sum256(payloadBytes)
+	if !bytes.Equal(sum[:], payloadHash) {
+		return ErrPayloadHashMismatch
+	}
+
+	return nil
+}
+
+// BuildRequestSigningInput returns the canonical byte sequence the v1 client
+// request signature covers.
+func BuildRequestSigningInput(fields RequestSigningFields) []byte {
+	size := len(requestDomainMarkerV1) +
+		len(fields.ProtocolVersion) +
+		len(fields.DeviceSessionID) +
+		len(fields.MessageType) +
+		len(fields.RequestID) +
+		len(fields.PayloadHash) +
+		(6 * binary.MaxVarintLen64) +
+		8
+
+	buf := make([]byte, 0, size)
+	buf = appendLengthPrefixedString(buf, requestDomainMarkerV1)
+	buf = appendLengthPrefixedString(buf, fields.ProtocolVersion)
+	buf = appendLengthPrefixedString(buf, fields.DeviceSessionID)
+	buf = appendLengthPrefixedString(buf, fields.MessageType)
+	buf = binary.BigEndian.AppendUint64(buf, uint64(fields.TimestampMS))
+	buf = appendLengthPrefixedString(buf, fields.RequestID)
+	buf = appendLengthPrefixedBytes(buf, fields.PayloadHash)
+
+	return buf
+}
+
+// BuildEventSigningInput returns the canonical byte sequence the v1 gateway
+// event signature covers.
+func BuildEventSigningInput(fields EventSigningFields) []byte {
+	size := len(eventDomainMarkerV1) +
+		len(fields.EventType) +
+		len(fields.EventID) +
+		len(fields.RequestID) +
+		len(fields.TraceID) +
+		len(fields.PayloadHash) +
+		(6 * binary.MaxVarintLen64) +
+		8
+
+	buf := make([]byte, 0, size)
+	buf = appendLengthPrefixedString(buf, eventDomainMarkerV1)
+	buf = appendLengthPrefixedString(buf, fields.EventType)
+	buf = appendLengthPrefixedString(buf, fields.EventID)
+	buf = binary.BigEndian.AppendUint64(buf, uint64(fields.TimestampMS))
+	buf = appendLengthPrefixedString(buf, fields.RequestID)
+	buf = appendLengthPrefixedString(buf, fields.TraceID)
+	buf = appendLengthPrefixedBytes(buf, fields.PayloadHash)
+
+	return buf
+}
+
+// SignRequest returns one raw Ed25519 client signature for the canonical v1
+// request signing input.
+func SignRequest(privateKey ed25519.PrivateKey, fields RequestSigningFields) []byte {
+	return ed25519.Sign(privateKey, BuildRequestSigningInput(fields))
+}
+
+// VerifyEventSignature reports whether signature authenticates fields under
+// publicKey using the canonical gateway event signing input.
+func VerifyEventSignature(publicKey ed25519.PublicKey, signature []byte, fields EventSigningFields) error {
+	if len(publicKey) != ed25519.PublicKeySize || len(signature) != ed25519.SignatureSize {
+		return ErrInvalidEventSignature
+	}
+	if !ed25519.Verify(publicKey, BuildEventSigningInput(fields), signature) {
+		return ErrInvalidEventSignature
+	}
+
+	return nil
+}
+
+func appendLengthPrefixedString(dst []byte, value string) []byte {
+	return appendLengthPrefixedBytes(dst, []byte(value))
+}
+
+func appendLengthPrefixedBytes(dst []byte, value []byte) []byte {
+	dst = binary.AppendUvarint(dst, uint64(len(value)))
+	dst = append(dst, value...)
+	return dst
+}

integration/internal/harness/binary.go

@@ -0,0 +1,71 @@
+// Package harness provides reusable black-box integration helpers shared by
+// inter-service suites.
+package harness
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+)
+
+var binaryCache struct {
+	mu    sync.Mutex
+	paths map[string]string
+}
+
+// BuildBinary builds packagePath once per test process and returns the
+// resulting executable path.
+func BuildBinary(t testing.TB, name string, packagePath string) string {
+	t.Helper()
+
+	root := repositoryRoot(t)
+	key := name + ":" + packagePath
+
+	binaryCache.mu.Lock()
+	if binaryCache.paths == nil {
+		binaryCache.paths = make(map[string]string)
+	}
+	if path, ok := binaryCache.paths[key]; ok {
+		binaryCache.mu.Unlock()
+		return path
+	}
+
+	outputDir := filepath.Join(os.TempDir(), "galaxy-integration-binaries")
+	if err := os.MkdirAll(outputDir, 0o755); err != nil {
+		binaryCache.mu.Unlock()
+		t.Fatalf("create integration binary directory: %v", err)
+	}
+
+	outputPath := filepath.Join(outputDir, sanitizeBinaryName(key))
+	cmd := exec.Command("go", "build", "-o", outputPath, packagePath)
+	cmd.Dir = root
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		binaryCache.mu.Unlock()
+		t.Fatalf("build %s: %v\n%s", packagePath, err, output)
+	}
+
+	binaryCache.paths[key] = outputPath
+	binaryCache.mu.Unlock()
+	return outputPath
+}
+
+func repositoryRoot(t testing.TB) string {
+	t.Helper()
+
+	_, file, _, ok := runtime.Caller(0)
+	if !ok {
+		t.Fatal("resolve harness repository root: runtime caller is unavailable")
+	}
+
+	return filepath.Clean(filepath.Join(filepath.Dir(file), "..", "..", ".."))
+}
+
+func sanitizeBinaryName(value string) string {
+	replacer := strings.NewReplacer("/", "_", "\\", "_", ":", "_", ".", "_")
+	return replacer.Replace(value)
+}

integration/internal/harness/keys.go

@@ -0,0 +1,54 @@
+package harness
+
+import (
+	"crypto/ed25519"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/pem"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/alicebob/miniredis/v2"
+)
+
+// StartMiniredis starts one isolated Redis-compatible in-memory server and
+// registers automatic cleanup.
+func StartMiniredis(t testing.TB) *miniredis.Miniredis {
+	t.Helper()
+
+	server, err := miniredis.Run()
+	if err != nil {
+		t.Fatalf("start miniredis: %v", err)
+	}
+
+	t.Cleanup(server.Close)
+	return server
+}
+
+// WriteResponseSignerPEM writes one deterministic PKCS#8 PEM-encoded Ed25519
+// private key for gateway response signing and returns the file path plus the
+// matching public key.
+func WriteResponseSignerPEM(t testing.TB, label string) (string, ed25519.PublicKey) {
+	t.Helper()
+
+	seed := sha256.Sum256([]byte("galaxy-integration-response-signer-" + label))
+	privateKey := ed25519.NewKeyFromSeed(seed[:])
+
+	encoded, err := x509.MarshalPKCS8PrivateKey(privateKey)
+	if err != nil {
+		t.Fatalf("marshal response signer private key: %v", err)
+	}
+
+	pemBytes := pem.EncodeToMemory(&pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: encoded,
+	})
+
+	path := filepath.Join(t.TempDir(), "response-signer.pem")
+	if err := os.WriteFile(path, pemBytes, 0o600); err != nil {
+		t.Fatalf("write response signer private key: %v", err)
+	}
+
+	return path, privateKey.Public().(ed25519.PublicKey)
+}

integration/internal/harness/mail_stub.go

@@ -0,0 +1,182 @@
+package harness
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+)
+
+const mailStubPath = "/api/v1/internal/login-code-deliveries"
+
+// LoginCodeDelivery stores one mail-delivery request received by the external
+// mail stub.
+type LoginCodeDelivery struct {
+	// Email identifies the target e-mail address requested by authsession.
+	Email string
+
+	// Code stores the cleartext login code requested by authsession.
+	Code string
+}
+
+// MailBehavior overrides one external mail-stub response.
+type MailBehavior struct {
+	// Delay waits before the stub writes its response.
+	Delay time.Duration
+
+	// StatusCode overrides the HTTP status returned by the stub. Zero keeps the
+	// default `200 OK`.
+	StatusCode int
+
+	// RawBody overrides the exact response body returned by the stub. Empty
+	// value keeps the default JSON payload for the chosen status.
+	RawBody string
+}
+
+// MailStub provides one stateful external HTTP mail-service stub.
+type MailStub struct {
+	server *httptest.Server
+
+	mu         sync.Mutex
+	deliveries []LoginCodeDelivery
+	behavior   MailBehavior
+}
+
+// NewMailStub starts one stateful external HTTP mail-service stub.
+func NewMailStub(t testing.TB) *MailStub {
+	t.Helper()
+
+	stub := &MailStub{}
+	stub.server = httptest.NewServer(http.HandlerFunc(stub.handle))
+	t.Cleanup(stub.server.Close)
+	return stub
+}
+
+// BaseURL returns the stub base URL suitable for service runtime wiring.
+func (s *MailStub) BaseURL() string {
+	if s == nil || s.server == nil {
+		return ""
+	}
+	return s.server.URL
+}
+
+// SetBehavior replaces the current response behavior used by subsequent
+// requests.
+func (s *MailStub) SetBehavior(behavior MailBehavior) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.behavior = behavior
+}
+
+// RecordedDeliveries returns a snapshot of all delivery requests received by
+// the stub so far.
+func (s *MailStub) RecordedDeliveries() []LoginCodeDelivery {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	cloned := make([]LoginCodeDelivery, len(s.deliveries))
+	copy(cloned, s.deliveries)
+	return cloned
+}
+
+// Reset clears the recorded deliveries and restores default behavior.
+func (s *MailStub) Reset() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.deliveries = nil
+	s.behavior = MailBehavior{}
+}
+
+func (s *MailStub) handle(writer http.ResponseWriter, request *http.Request) {
+	if request.Method != http.MethodPost || request.URL.Path != mailStubPath {
+		http.NotFound(writer, request)
+		return
+	}
+
+	var payload struct {
+		Email string `json:"email"`
+		Code  string `json:"code"`
+	}
+	if err := decodeStrictJSONRequest(request, &payload); err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	s.deliveries = append(s.deliveries, LoginCodeDelivery{
+		Email: payload.Email,
+		Code:  payload.Code,
+	})
+	behavior := s.behavior
+	s.mu.Unlock()
+
+	if behavior.Delay > 0 {
+		timer := time.NewTimer(behavior.Delay)
+		defer timer.Stop()
+
+		select {
+		case <-request.Context().Done():
+			return
+		case <-timer.C:
+		}
+	}
+
+	statusCode := behavior.StatusCode
+	if statusCode == 0 {
+		statusCode = http.StatusOK
+	}
+
+	body := behavior.RawBody
+	if body == "" {
+		switch statusCode {
+		case http.StatusOK:
+			body = `{"outcome":"sent"}`
+		default:
+			body = `{"error":"stubbed mail failure"}`
+		}
+	}
+
+	writer.Header().Set("Content-Type", "application/json")
+	writer.WriteHeader(statusCode)
+	_, _ = io.WriteString(writer, body)
+}
+
+func decodeStrictJSONRequest(request *http.Request, target any) error {
+	decoder := json.NewDecoder(request.Body)
+	decoder.DisallowUnknownFields()
+
+	if err := decoder.Decode(target); err != nil {
+		return err
+	}
+	if err := decoder.Decode(&struct{}{}); err != io.EOF {
+		if err == nil {
+			return errors.New("unexpected trailing JSON input")
+		}
+		return err
+	}
+
+	return nil
+}
+
+func decodeStrictJSONPayload(payload []byte, target any) error {
+	decoder := json.NewDecoder(bytes.NewReader(payload))
+	decoder.DisallowUnknownFields()
+
+	if err := decoder.Decode(target); err != nil {
+		return err
+	}
+	if err := decoder.Decode(&struct{}{}); err != io.EOF {
+		if err == nil {
+			return errors.New("unexpected trailing JSON input")
+		}
+		return err
+	}
+
+	return nil
+}

integration/internal/harness/process.go

@@ -0,0 +1,276 @@
+package harness
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"syscall"
+	"testing"
+	"time"
+)
+
+const (
+	defaultStartupWait  = 10 * time.Second
+	defaultPollInterval = 25 * time.Millisecond
+	defaultStopWait     = 5 * time.Second
+)
+
+// Process represents one long-lived external service process started by an
+// integration suite.
+type Process struct {
+	name string
+	cmd  *exec.Cmd
+
+	logsMu sync.Mutex
+	logs   bytes.Buffer
+
+	doneCh  chan struct{}
+	waitErr error
+}
+
+// StartProcess starts binaryPath with envOverrides and registers cleanup that
+// stops the process and prints captured logs on failed tests.
+func StartProcess(t testing.TB, name string, binaryPath string, envOverrides map[string]string) *Process {
+	t.Helper()
+
+	cmd := exec.Command(binaryPath)
+	cmd.Env = mergeEnvironment(os.Environ(), envOverrides)
+
+	process := &Process{
+		name:   name,
+		cmd:    cmd,
+		doneCh: make(chan struct{}),
+	}
+	cmd.Stdout = process.logWriter()
+	cmd.Stderr = process.logWriter()
+
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start %s: %v", name, err)
+	}
+
+	go func() {
+		process.waitErr = cmd.Wait()
+		close(process.doneCh)
+	}()
+
+	t.Cleanup(func() {
+		process.Stop(t)
+		if t.Failed() {
+			t.Logf("%s logs:\n%s", name, process.Logs())
+		}
+	})
+
+	return process
+}
+
+// Stop asks the process to terminate gracefully and waits for completion.
+func (p *Process) Stop(t testing.TB) {
+	t.Helper()
+
+	if p == nil {
+		return
+	}
+
+	select {
+	case <-p.doneCh:
+		err := p.waitErr
+		if err != nil && !isExpectedProcessExit(err) {
+			t.Errorf("%s exited unexpectedly: %v", p.name, err)
+		}
+		return
+	default:
+	}
+
+	if p.cmd.Process != nil {
+		_ = p.cmd.Process.Signal(syscall.SIGTERM)
+	}
+
+	select {
+	case <-p.doneCh:
+		err := p.waitErr
+		if err != nil && !isExpectedProcessExit(err) {
+			t.Errorf("%s exited unexpectedly: %v", p.name, err)
+		}
+	case <-time.After(defaultStopWait):
+		if p.cmd.Process != nil {
+			_ = p.cmd.Process.Kill()
+		}
+		<-p.doneCh
+		err := p.waitErr
+		if err != nil && !isExpectedProcessExit(err) {
+			t.Errorf("%s exited unexpectedly: %v", p.name, err)
+		}
+	}
+}
+
+// Logs returns the captured combined stdout/stderr output of the process.
+func (p *Process) Logs() string {
+	if p == nil {
+		return ""
+	}
+
+	p.logsMu.Lock()
+	defer p.logsMu.Unlock()
+	return p.logs.String()
+}
+
+// FreeTCPAddress reserves one ephemeral loopback TCP address and releases it
+// immediately so a service process can bind to it.
+func FreeTCPAddress(t testing.TB) string {
+	t.Helper()
+
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("reserve free TCP address: %v", err)
+	}
+
+	addr := listener.Addr().String()
+	if err := listener.Close(); err != nil {
+		t.Fatalf("release reserved TCP address: %v", err)
+	}
+
+	return addr
+}
+
+// WaitForHTTPStatus waits until url responds with wantStatus or fails when the
+// backing process exits early.
+func WaitForHTTPStatus(t testing.TB, process *Process, url string, wantStatus int) {
+	t.Helper()
+
+	client := &http.Client{
+		Timeout: 250 * time.Millisecond,
+		Transport: &http.Transport{
+			DisableKeepAlives: true,
+		},
+	}
+	defer client.CloseIdleConnections()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultStartupWait)
+	defer cancel()
+
+	ticker := time.NewTicker(defaultPollInterval)
+	defer ticker.Stop()
+
+	for {
+		if err := processErr(process); err != nil {
+			t.Fatalf("%s exited before %s became ready: %v\n%s", process.name, url, err, process.Logs())
+		}
+
+		request, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+		if err != nil {
+			t.Fatalf("build readiness request for %s: %v", url, err)
+		}
+
+		response, err := client.Do(request)
+		if err == nil {
+			_, _ = io.Copy(io.Discard, response.Body)
+			response.Body.Close()
+			if response.StatusCode == wantStatus {
+				return
+			}
+		}
+
+		select {
+		case <-ctx.Done():
+			t.Fatalf("wait for %s status %d: %v\n%s", url, wantStatus, ctx.Err(), process.Logs())
+		case <-ticker.C:
+		}
+	}
+}
+
+// WaitForTCP waits until address accepts TCP connections or fails when the
+// backing process exits early.
+func WaitForTCP(t testing.TB, process *Process, address string) {
+	t.Helper()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultStartupWait)
+	defer cancel()
+
+	ticker := time.NewTicker(defaultPollInterval)
+	defer ticker.Stop()
+
+	for {
+		if err := processErr(process); err != nil {
+			t.Fatalf("%s exited before %s became reachable: %v\n%s", process.name, address, err, process.Logs())
+		}
+
+		conn, err := net.DialTimeout("tcp", address, 100*time.Millisecond)
+		if err == nil {
+			_ = conn.Close()
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			t.Fatalf("wait for %s TCP readiness: %v\n%s", address, ctx.Err(), process.Logs())
+		case <-ticker.C:
+		}
+	}
+}
+
+func (p *Process) logWriter() io.Writer {
+	return writerFunc(func(data []byte) (int, error) {
+		p.logsMu.Lock()
+		defer p.logsMu.Unlock()
+		return p.logs.Write(data)
+	})
+}
+
+func mergeEnvironment(base []string, overrides map[string]string) []string {
+	values := make(map[string]string, len(base)+len(overrides))
+	for _, entry := range base {
+		name, value, ok := strings.Cut(entry, "=")
+		if ok {
+			values[name] = value
+		}
+	}
+	for name, value := range overrides {
+		values[name] = value
+	}
+
+	merged := make([]string, 0, len(values))
+	for name, value := range values {
+		merged = append(merged, fmt.Sprintf("%s=%s", name, value))
+	}
+	return merged
+}
+
+func processErr(process *Process) error {
+	if process == nil {
+		return errors.New("nil process")
+	}
+
+	select {
+	case <-process.doneCh:
+		return process.waitErr
+	default:
+		return nil
+	}
+}
+
+func isExpectedProcessExit(err error) bool {
+	if err == nil {
+		return true
+	}
+
+	var exitErr *exec.ExitError
+	if !errors.As(err, &exitErr) {
+		return false
+	}
+
+	return exitErr.ExitCode() == -1
+}
+
+type writerFunc func([]byte) (int, error)
+
+func (f writerFunc) Write(data []byte) (int, error) {
+	return f(data)
+}

integration/internal/harness/user_stub.go

@@ -0,0 +1,323 @@
+package harness
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"sync"
+	"testing"
+)
+
+const (
+	resolveByEmailPath = "/api/v1/internal/user-resolutions/by-email"
+	ensureByEmailPath  = "/api/v1/internal/users/ensure-by-email"
+	blockByEmailPath   = "/api/v1/internal/user-blocks/by-email"
+)
+
+// EnsureUserCall stores one ensure-by-email request received by the external
+// user-service stub.
+type EnsureUserCall struct {
+	// Email identifies the requested login or registration e-mail.
+	Email string
+
+	// PreferredLanguage stores the forwarded registration-context language.
+	PreferredLanguage string
+
+	// TimeZone stores the forwarded registration-context time zone.
+	TimeZone string
+}
+
+// UserStub provides one stateful external HTTP user-service stub.
+type UserStub struct {
+	server *httptest.Server
+
+	mu sync.Mutex
+
+	emailToUserID map[string]string
+	userIDToEmail map[string]string
+	blockedEmails map[string]string
+	blockedUsers  map[string]string
+	ensureCalls   []EnsureUserCall
+	nextUserID    int
+}
+
+// NewUserStub starts one stateful external HTTP user-service stub.
+func NewUserStub(t testing.TB) *UserStub {
+	t.Helper()
+
+	stub := &UserStub{
+		emailToUserID: make(map[string]string),
+		userIDToEmail: make(map[string]string),
+		blockedEmails: make(map[string]string),
+		blockedUsers:  make(map[string]string),
+		nextUserID:    1,
+	}
+	stub.server = httptest.NewServer(http.HandlerFunc(stub.handle))
+	t.Cleanup(stub.server.Close)
+	return stub
+}
+
+// BaseURL returns the stub base URL suitable for authsession runtime wiring.
+func (s *UserStub) BaseURL() string {
+	if s == nil || s.server == nil {
+		return ""
+	}
+	return s.server.URL
+}
+
+// SeedExisting adds one existing unblocked user record into the stub state.
+func (s *UserStub) SeedExisting(email string, userID string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.emailToUserID[email] = userID
+	s.userIDToEmail[userID] = email
+}
+
+// SeedBlockedEmail adds one blocked e-mail into the stub state.
+func (s *UserStub) SeedBlockedEmail(email string, reasonCode string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.blockedEmails[email] = reasonCode
+	if userID, ok := s.emailToUserID[email]; ok {
+		s.blockedUsers[userID] = reasonCode
+	}
+}
+
+// EnsureCalls returns a snapshot of ensure-by-email requests observed by the
+// stub so far.
+func (s *UserStub) EnsureCalls() []EnsureUserCall {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	cloned := make([]EnsureUserCall, len(s.ensureCalls))
+	copy(cloned, s.ensureCalls)
+	return cloned
+}
+
+// Reset clears all stub state and recorded calls.
+func (s *UserStub) Reset() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.emailToUserID = make(map[string]string)
+	s.userIDToEmail = make(map[string]string)
+	s.blockedEmails = make(map[string]string)
+	s.blockedUsers = make(map[string]string)
+	s.ensureCalls = nil
+	s.nextUserID = 1
+}
+
+func (s *UserStub) handle(writer http.ResponseWriter, request *http.Request) {
+	switch {
+	case request.Method == http.MethodPost && request.URL.Path == resolveByEmailPath:
+		s.handleResolveByEmail(writer, request)
+	case request.Method == http.MethodGet && strings.HasPrefix(request.URL.Path, "/api/v1/internal/users/") && strings.HasSuffix(request.URL.Path, "/exists"):
+		s.handleExistsByUserID(writer, request)
+	case request.Method == http.MethodPost && request.URL.Path == ensureByEmailPath:
+		s.handleEnsureByEmail(writer, request)
+	case request.Method == http.MethodPost && strings.HasPrefix(request.URL.Path, "/api/v1/internal/users/") && strings.HasSuffix(request.URL.Path, "/block"):
+		s.handleBlockByUserID(writer, request)
+	case request.Method == http.MethodPost && request.URL.Path == blockByEmailPath:
+		s.handleBlockByEmail(writer, request)
+	default:
+		http.NotFound(writer, request)
+	}
+}
+
+func (s *UserStub) handleResolveByEmail(writer http.ResponseWriter, request *http.Request) {
+	var payload struct {
+		Email string `json:"email"`
+	}
+	if err := decodeStrictJSONRequest(request, &payload); err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if reason, ok := s.blockedEmails[payload.Email]; ok {
+		writeJSON(writer, http.StatusOK, map[string]any{
+			"kind":              "blocked",
+			"block_reason_code": reason,
+		})
+		return
+	}
+
+	if userID, ok := s.emailToUserID[payload.Email]; ok {
+		if reason, blocked := s.blockedUsers[userID]; blocked {
+			writeJSON(writer, http.StatusOK, map[string]any{
+				"kind":              "blocked",
+				"block_reason_code": reason,
+			})
+			return
+		}
+
+		writeJSON(writer, http.StatusOK, map[string]any{
+			"kind":    "existing",
+			"user_id": userID,
+		})
+		return
+	}
+
+	writeJSON(writer, http.StatusOK, map[string]any{"kind": "creatable"})
+}
+
+func (s *UserStub) handleExistsByUserID(writer http.ResponseWriter, request *http.Request) {
+	userIDValue := strings.TrimSuffix(strings.TrimPrefix(request.URL.Path, "/api/v1/internal/users/"), "/exists")
+	userIDValue, err := url.PathUnescape(userIDValue)
+	if err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	_, exists := s.userIDToEmail[userIDValue]
+	writeJSON(writer, http.StatusOK, map[string]bool{"exists": exists})
+}
+
+func (s *UserStub) handleEnsureByEmail(writer http.ResponseWriter, request *http.Request) {
+	var payload struct {
+		Email               string `json:"email"`
+		RegistrationContext *struct {
+			PreferredLanguage string `json:"preferred_language"`
+			TimeZone          string `json:"time_zone"`
+		} `json:"registration_context"`
+	}
+	if err := decodeStrictJSONRequest(request, &payload); err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+	if payload.RegistrationContext == nil {
+		http.Error(writer, "registration_context must be present", http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.ensureCalls = append(s.ensureCalls, EnsureUserCall{
+		Email:             payload.Email,
+		PreferredLanguage: payload.RegistrationContext.PreferredLanguage,
+		TimeZone:          payload.RegistrationContext.TimeZone,
+	})
+
+	if reason, ok := s.blockedEmails[payload.Email]; ok {
+		writeJSON(writer, http.StatusOK, map[string]any{
+			"outcome":           "blocked",
+			"block_reason_code": reason,
+		})
+		return
+	}
+
+	if userID, ok := s.emailToUserID[payload.Email]; ok {
+		if reason, blocked := s.blockedUsers[userID]; blocked {
+			writeJSON(writer, http.StatusOK, map[string]any{
+				"outcome":           "blocked",
+				"block_reason_code": reason,
+			})
+			return
+		}
+
+		writeJSON(writer, http.StatusOK, map[string]any{
+			"outcome": "existing",
+			"user_id": userID,
+		})
+		return
+	}
+
+	userID := fmt.Sprintf("user-%d", s.nextUserID)
+	s.nextUserID++
+	s.emailToUserID[payload.Email] = userID
+	s.userIDToEmail[userID] = payload.Email
+
+	writeJSON(writer, http.StatusOK, map[string]any{
+		"outcome": "created",
+		"user_id": userID,
+	})
+}
+
+func (s *UserStub) handleBlockByUserID(writer http.ResponseWriter, request *http.Request) {
+	userIDValue := strings.TrimSuffix(strings.TrimPrefix(request.URL.Path, "/api/v1/internal/users/"), "/block")
+	userIDValue, err := url.PathUnescape(userIDValue)
+	if err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	var payload struct {
+		ReasonCode string `json:"reason_code"`
+	}
+	if err := decodeStrictJSONRequest(request, &payload); err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	email, exists := s.userIDToEmail[userIDValue]
+	if !exists {
+		writeJSON(writer, http.StatusNotFound, map[string]string{"error": "not found"})
+		return
+	}
+
+	outcome := "blocked"
+	if _, already := s.blockedUsers[userIDValue]; already {
+		outcome = "already_blocked"
+	}
+	s.blockedUsers[userIDValue] = payload.ReasonCode
+	s.blockedEmails[email] = payload.ReasonCode
+
+	writeJSON(writer, http.StatusOK, map[string]any{
+		"outcome": outcome,
+		"user_id": userIDValue,
+	})
+}
+
+func (s *UserStub) handleBlockByEmail(writer http.ResponseWriter, request *http.Request) {
+	var payload struct {
+		Email      string `json:"email"`
+		ReasonCode string `json:"reason_code"`
+	}
+	if err := decodeStrictJSONRequest(request, &payload); err != nil {
+		http.Error(writer, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	outcome := "blocked"
+	if _, already := s.blockedEmails[payload.Email]; already {
+		outcome = "already_blocked"
+	}
+	s.blockedEmails[payload.Email] = payload.ReasonCode
+
+	response := map[string]any{"outcome": outcome}
+	if userID, ok := s.emailToUserID[payload.Email]; ok {
+		s.blockedUsers[userID] = payload.ReasonCode
+		response["user_id"] = userID
+	}
+
+	writeJSON(writer, http.StatusOK, response)
+}
+
+func writeJSON(writer http.ResponseWriter, statusCode int, value any) {
+	payload, err := json.Marshal(value)
+	if err != nil {
+		http.Error(writer, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	writer.Header().Set("Content-Type", "application/json")
+	writer.WriteHeader(statusCode)
+	_, _ = writer.Write(payload)
+}