chore(agentnetwork): fix config grouping, dead code, comments, coverage

- Move the new zone config key into the existing AgentNetwork config
  group (management/internals/server/config/config.go) instead of a
  sibling top-level field, wire modules.go to the new path, add the
  matching field to combined/cmd/config.go's AgentNetworkConfig and its
  mapping (it was previously unreachable in the combined binary), and
  document the key in infrastructure_files/management.json.tmpl and
  combined/config.yaml.example.

- Delete PickUnique and its three tests: Task 5 removed its last
  production caller, leaving it dead exported code with a stale
  words.go comment pointing at it.

- Reword two test comments that referenced our private review process
  instead of stating what the test locks down / why TargetId stays
  pinned to Cluster.

- Add TestBootstrapSettings_NonRetryableErrorFailsImmediately: a
  regression that dropped the isUniqueConstraintError gate and retried
  on every error would leave every existing allocator test green.

- Fix TestSynthesizeServiceForDomain_DegenerateInput's docstring: the
  early-return guard is an optimisation, not what makes "" and
  "localhost" resolve to no service.

- Replace manager.go's allocation-comment archaeology (a deleted
  per-cluster "taken" set, an `accountID[:4]` suffix, "~68 minutes") with
  the actual invariant, and note why each retry attempt gets its own
  transaction (a failed statement poisons the enclosing transaction on
  postgres).

- Collapse the per-service "no matching zone apex" debug log in
  account.go into a single line per call instead of one per skipped
  service.

- Document why idx_agent_network_settings_cluster_subdomain must stay
  on mysql: its index tag is what sizes subdomain as varchar(191)
  rather than longtext, which the new unique index requires.

combined/cmd/config.go

@@ -83,6 +83,7 @@ type ServerConfig struct {
 // AgentNetworkConfig contains agent-network (LLM gateway) configuration.
 type AgentNetworkConfig struct {
 	PricingDefaultsFile string `yaml:"pricingDefaultsFile"`
+	Zone                string `yaml:"zone"`
 }
 
 // TLSConfig contains TLS/HTTPS settings
@@ -732,6 +733,7 @@ func (c *CombinedConfig) ToManagementConfig() (*nbconfig.Config, error) {
 		PerAccountHighestSupportedSyncMessageVersion: c.Server.PerAccountSupportedSyncMessageVersions,
 		AgentNetwork: nbconfig.AgentNetwork{
 			PricingDefaultsFile: c.Server.AgentNetwork.PricingDefaultsFile,
+			Zone:                c.Server.AgentNetwork.Zone,
 		},
 	}, nil
 }

combined/config.yaml.example

@@ -147,3 +147,11 @@ server:
   #   # is re-read periodically (mtime poll). An explicitly configured path that
   #   # fails to load fails startup; runtime reload errors keep the previous table.
   #   pricingDefaultsFile: "pricing.yaml"
+  #
+  #   # Parent DNS zone that Agent Network gateway endpoints are allocated
+  #   # under, producing <subdomain>.<zone>. Empty (the default) preserves the
+  #   # legacy behaviour of deriving the endpoint from the serving cluster, so
+  #   # self-hosted deployments are unaffected. Captured onto each settings row
+  #   # when that row is created; changing it later does not move existing
+  #   # tenants.
+  #   zone: "gateway.example.com"

infrastructure_files/management.json.tmpl

@@ -39,6 +39,9 @@
         ]
     },
     "DisableDefaultPolicy": $NETBIRD_MGMT_DISABLE_DEFAULT_POLICY,
+    "AgentNetwork": {
+        "Zone": "$NETBIRD_AGENT_NETWORK_ZONE"
+    },
     "Datadir": "",
     "DataStoreEncryptionKey": "$NETBIRD_DATASTORE_ENC_KEY",
     "StoreConfig": {

management/internals/modules/agentnetwork/allocate_test.go

@@ -234,7 +234,9 @@ func TestBootstrapSettings_ConcurrentBootstrapReturnsWinnersRow(t *testing.T) {
 			Return(nil, status.Errorf(status.NotFound, "agent network settings not found")),
 		// The insert loses the race. The message shape is the sqlite wording
 		// for a primary-key violation on account_id (not the subdomain
-		// index), per the review finding this test locks down.
+		// index); this test locks down that the retry path recognizes that
+		// shape as a race loss and re-reads the winner's row, rather than
+		// misclassifying it as a subdomain conflict.
 		mockStore.EXPECT().
 			ExecuteInTransaction(gomock.Any(), gomock.Any()).
 			DoAndReturn(func(_ context.Context, f func(store.Store) error) error {
@@ -259,3 +261,36 @@ func TestBootstrapSettings_ConcurrentBootstrapReturnsWinnersRow(t *testing.T) {
 	require.NotNil(t, settings)
 	assert.Same(t, winner, settings, "the loser must return the concurrent winner's row, not retry past it")
 }
+
+// TestBootstrapSettings_NonRetryableErrorFailsImmediately guards the
+// isUniqueConstraintError branch itself: a regression that dropped that check
+// and retried on every ExecuteInTransaction error would leave every other test
+// in this file green, because none of them feed the loop a non-collision
+// failure. A generic store error must surface immediately, wrapped, and must
+// not be retried — asserting ExecuteInTransaction was called exactly once is
+// what proves the loop didn't retry.
+func TestBootstrapSettings_NonRetryableErrorFailsImmediately(t *testing.T) {
+	ctx := context.Background()
+	ctrl := gomock.NewController(t)
+	mockStore := store.NewMockStore(ctrl)
+
+	mockStore.EXPECT().
+		GetAgentNetworkSettings(gomock.Any(), store.LockingStrengthNone, "account1").
+		Return(nil, status.Errorf(status.NotFound, "agent network settings not found"))
+
+	mockStore.EXPECT().
+		ExecuteInTransaction(gomock.Any(), gomock.Any()).
+		Return(errors.New("connection refused")).
+		Times(1)
+
+	m := &managerImpl{
+		store:    mockStore,
+		labelRng: rand.New(rand.NewSource(5)),
+	}
+
+	settings, err := m.bootstrapSettingsIfNeeded(ctx, "account1", "cluster1.example.com")
+	require.Error(t, err, "a non-collision store error must surface, not be swallowed")
+	assert.Nil(t, settings)
+	assert.Contains(t, err.Error(), "create agent network settings",
+		"the non-retryable error must be wrapped and returned, not retried past")
+}

management/internals/modules/agentnetwork/domainlookup_test.go

@@ -100,7 +100,12 @@ func TestSynthesizeServiceForDomain_UnknownLabel(t *testing.T) {
 }
 
 // TestSynthesizeServiceForDomain_DegenerateInput — empty and single-label
-// hostnames have no subdomain to look up and must not reach the store.
+// hostnames have no dot to cut a subdomain label from, so they resolve to no
+// service, same as any other unowned hostname. The early-return guard that
+// catches them is an optimisation (it skips a store round trip that would
+// only miss anyway), not what makes this case correct — "" and "localhost"
+// would still come back nil, nil even without it, via the same not-found
+// fallthrough TestSynthesizeServiceForDomain_UnknownLabel exercises.
 func TestSynthesizeServiceForDomain_DegenerateInput(t *testing.T) {
 	ctx := context.Background()
 	s, cleanup, err := store.NewTestStoreFromSQL(ctx, "", t.TempDir())

management/internals/modules/agentnetwork/labelgen/labelgen.go

@@ -2,18 +2,11 @@
 package labelgen
 
 import (
-	"fmt"
 	"math/rand"
 	"sort"
 	"sync"
 )
 
-// pickAttempts caps the random retries before falling back to the
-// suffixed form. Eight is a soft compromise: with a near-empty taken
-// set the very first pick almost always succeeds; when the wordlist is
-// densely populated the fallback eventually fires anyway.
-const pickAttempts = 8
-
 var (
 	dedupOnce sync.Once
 	uniqWords []string
@@ -37,43 +30,15 @@ func uniqueWords() []string {
 	return uniqWords
 }
 
-// PickUnique selects a label not already in `taken`. It tries up to
-// pickAttempts random picks; on exhaustion it scans the deduplicated
-// wordlist for any remaining free entry, and if none is left appends
-// `-<fallbackSuffix>` to a deterministic word and returns. The caller
-// is responsible for seeding rng (math/rand).
-func PickUnique(rng *rand.Rand, taken map[string]struct{}, fallbackSuffix string) string {
-	pool := uniqueWords()
-	if len(pool) == 0 {
-		return fallbackSuffix
-	}
-
-	for i := 0; i < pickAttempts; i++ {
-		w := pool[rng.Intn(len(pool))]
-		if _, ok := taken[w]; !ok {
-			return w
-		}
-	}
-
-	for _, w := range pool {
-		if _, ok := taken[w]; !ok {
-			return w
-		}
-	}
-
-	w := pool[rng.Intn(len(pool))]
-	return fmt.Sprintf("%s-%s", w, fallbackSuffix)
-}
-
 // PickTuple returns an adjective-noun label such as "brave-otter". It is still
 // a single DNS label.
 //
-// Unlike PickUnique it takes no `taken` set and has no fallback suffix. The
-// noun pool holds 857 entries, which is ample per cluster but a hard ceiling
-// once labels must be unique across one shared zone; pairing an adjective with
-// a noun spans len(adjectives) * 857 instead. Uniqueness is enforced by a
-// database constraint and retried by the caller, rather than guessed from a
-// pre-read set that a concurrent allocation can invalidate.
+// It takes no `taken` set and has no fallback suffix. The noun pool holds 857
+// entries, which is ample per cluster but a hard ceiling once labels must be
+// unique across one shared zone; pairing an adjective with a noun spans
+// len(adjectives) * 857 instead. Uniqueness is enforced by a database
+// constraint and retried by the caller, rather than guessed from a pre-read
+// set that a concurrent allocation can invalidate.
 func PickTuple(rng *rand.Rand) string {
 	nouns := uniqueWords()
 	if len(nouns) == 0 || len(adjectives) == 0 {

management/internals/modules/agentnetwork/labelgen/labelgen_test.go

@@ -9,78 +9,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-// TestPickUnique_DeterministicWithSeededRng locks the property the
-// caller relies on: same seed + same taken set → same pick. Without
-// that, the bootstrap flow can't reproduce a label across retries.
-func TestPickUnique_DeterministicWithSeededRng(t *testing.T) {
-	taken := map[string]struct{}{}
-
-	rngA := rand.New(rand.NewSource(42))
-	rngB := rand.New(rand.NewSource(42))
-
-	a := PickUnique(rngA, taken, "abcd")
-	b := PickUnique(rngB, taken, "abcd")
-
-	assert.Equal(t, a, b, "Same seed and taken set must produce identical pick")
-}
-
-// TestPickUnique_AvoidsTakenWordsWhenMostAreReserved seeds taken with
-// every word in the pool except a handful and confirms PickUnique
-// finds one of the remaining free entries instead of returning the
-// fallback form.
-func TestPickUnique_AvoidsTakenWordsWhenMostAreReserved(t *testing.T) {
-	pool := uniqueWords()
-	require.NotEmpty(t, pool, "wordlist must be populated for the test to mean anything")
-
-	free := map[string]struct{}{
-		pool[0]:           {},
-		pool[len(pool)/2]: {},
-		pool[len(pool)-1]: {},
-	}
-
-	taken := make(map[string]struct{}, len(pool))
-	for _, w := range pool {
-		if _, ok := free[w]; ok {
-			continue
-		}
-		taken[w] = struct{}{}
-	}
-
-	rng := rand.New(rand.NewSource(7))
-	got := PickUnique(rng, taken, "abcd")
-
-	_, isFree := free[got]
-	assert.True(t, isFree, "PickUnique must return one of the free words; got %q", got)
-	assert.NotContains(t, got, "-", "Free pick must not be the suffix fallback form")
-}
-
-// TestPickUnique_FallsBackWhenAllReserved exhausts the pool and
-// confirms PickUnique appends the supplied suffix instead of
-// returning a duplicate.
-func TestPickUnique_FallsBackWhenAllReserved(t *testing.T) {
-	pool := uniqueWords()
-
-	taken := make(map[string]struct{}, len(pool))
-	for _, w := range pool {
-		taken[w] = struct{}{}
-	}
-
-	rng := rand.New(rand.NewSource(99))
-	got := PickUnique(rng, taken, "abcd")
-
-	assert.True(t, strings.HasSuffix(got, "-abcd"), "Exhausted pool must produce <word>-<suffix>; got %q", got)
-
-	prefix := strings.TrimSuffix(got, "-abcd")
-	found := false
-	for _, w := range pool {
-		if w == prefix {
-			found = true
-			break
-		}
-	}
-	assert.True(t, found, "Fallback prefix must be drawn from the wordlist; got %q", prefix)
-}
-
 // TestUniqueWords_DropsDuplicates guards against authoring slips in
 // words.go: every entry must be unique and DNS-safe.
 func TestUniqueWords_DropsDuplicates(t *testing.T) {

management/internals/modules/agentnetwork/labelgen/words.go

@@ -6,7 +6,7 @@
 // hand-checked to avoid offensive, brand, or region-specific terms.
 package labelgen
 
-// words is the pool PickUnique selects from. The slice is intentionally
+// words is the pool PickTuple draws its noun from. The slice is intentionally
 // not sorted — random picks distribute across the list naturally.
 var words = []string{
 	"acorn", "adobe", "agate", "alder", "almond", "alpine", "amber", "amethyst",

management/internals/modules/agentnetwork/manager.go

@@ -690,13 +690,9 @@ func (m *managerImpl) bootstrapSettingsIfNeeded(ctx context.Context, accountID,
 		return nil, fmt.Errorf("get agent network settings: %w", err)
 	}
 
-	// Allocate a subdomain and insert in one transaction, retrying on a unique
-	// violation. This replaces a read-then-write over a pre-computed "taken"
-	// set, which had three defects: the set was per-cluster (wrong once the
-	// endpoint hangs off a shared zone), the read and the write were not
-	// atomic, and the exhaustion fallback appended accountID[:4] — constant for
-	// every account created within the same ~68 minutes — with no retry and no
-	// uniqueness check, so two such accounts could be handed the same label.
+	// Labels must be unique across the whole zone; the database's unique index
+	// enforces that, and the loop below retries with a fresh label whenever an
+	// attempt is rejected.
 	now := time.Now().UTC()
 	settings := &types.Settings{
 		AccountID:              accountID,
@@ -723,6 +719,10 @@ func (m *managerImpl) bootstrapSettingsIfNeeded(ctx context.Context, accountID,
 				accountID)
 		}
 
+		// Each attempt gets its own transaction wrapping a single INSERT: on
+		// postgres a failed statement poisons the enclosing transaction, so a
+		// fresh transaction per attempt is what makes the retry loop work on
+		// that dialect at all.
 		err := m.store.ExecuteInTransaction(ctx, func(transaction store.Store) error {
 			return transaction.CreateAgentNetworkSettings(ctx, settings)
 		})

management/internals/server/config/config.go

@@ -67,15 +67,6 @@ type Config struct {
 	HighestSupportedSyncMessageVersion *int
 
 	PerAccountHighestSupportedSyncMessageVersion map[string]int
-
-	// AgentNetworkZone is the parent DNS zone that Agent Network gateway
-	// endpoints are allocated under, producing <subdomain>.<zone>.
-	//
-	// Empty (the default) preserves the legacy behaviour of deriving the
-	// endpoint from the serving cluster, so self-hosted deployments are
-	// unaffected. It is captured onto each settings row when that row is
-	// created; changing it later does not move existing tenants.
-	AgentNetworkZone string
 }
 
 // GetAuthAudiences returns the audience from the http config and device authorization flow config
@@ -213,6 +204,15 @@ type AgentNetwork struct {
 	// prefill with). An explicitly configured path that fails to load
 	// fails startup; runtime reload errors keep the previous table.
 	PricingDefaultsFile string
+
+	// Zone is the parent DNS zone that Agent Network gateway endpoints are
+	// allocated under, producing <subdomain>.<zone>.
+	//
+	// Empty (the default) preserves the legacy behaviour of deriving the
+	// endpoint from the serving cluster, so self-hosted deployments are
+	// unaffected. It is captured onto each settings row when that row is
+	// created; changing it later does not move existing tenants.
+	Zone string
 }
 
 // ReverseProxy contains reverse proxy configuration in front of management.

management/internals/server/modules.go

@@ -202,7 +202,7 @@ func (s *BaseServer) AgentNetworkManager() agentnetwork.Manager {
 			s.PermissionsManager(),
 			s.AccountManager(),
 			s.ServiceProxyController(),
-			s.Config.AgentNetworkZone,
+			s.Config.AgentNetwork.Zone,
 		)
 		// Sweep expired agent-network access logs per account retention,
 		// reusing the reverse-proxy cleanup interval config.

management/server/store/store.go

@@ -672,6 +672,12 @@ func getMigrationsPostAuto(ctx context.Context) []migrationFunc {
 			// The pre-existing idx_agent_network_settings_cluster_subdomain is
 			// left in place: it is non-unique and indexes subdomain alone
 			// (Cluster carries no tag), so it neither conflicts nor suffices.
+			// It must also stay for a second, load-bearing reason on mysql:
+			// its gorm:"index:" tag on the Subdomain field is what makes gorm
+			// size that column as varchar(191) instead of longtext. mysql
+			// cannot put a longtext column in a unique index at all, so
+			// dropping this "redundant" index as unneeded would silently
+			// break the migration above on that dialect.
 			return migration.CreateIndexIfNotExists[agentNetworkTypes.Settings](
 				ctx, db, "idx_agent_network_settings_subdomain_unique", "subdomain",
 			)

management/server/types/account.go

@@ -254,6 +254,7 @@ func (a *Account) SynthesizePrivateServiceZones(peerID string) []nbdns.CustomZon
 
 	peerGroups := a.GetPeerGroups(peerID)
 	zonesByApex := map[string]*nbdns.CustomZone{}
+	var skippedNoZoneApex []string
 
 	for _, svc := range a.Services {
 		if svc == nil || !svc.Enabled || !svc.Private {
@@ -275,9 +276,12 @@ func (a *Account) SynthesizePrivateServiceZones(peerID string) []nbdns.CustomZon
 			// This service passed every gate above (enabled, private,
 			// AccessGroups, connected proxy peers) and would otherwise have
 			// emitted a record, but its domain matches neither its DNSZone,
-			// its ProxyCluster, nor any validated custom-domain row.
-			log.Debugf("private-zone synth: svc %s domain=%s cluster=%s dns_zone=%q has no matching zone apex, skipping",
-				svc.ID, svc.Domain, svc.ProxyCluster, svc.DNSZone)
+			// its ProxyCluster, nor any validated custom-domain row. Collected
+			// rather than logged here — this runs per peer x per service, and
+			// logging inline here would reintroduce the per-peer noise the
+			// "0 zones" diagnostic below deliberately avoids.
+			skippedNoZoneApex = append(skippedNoZoneApex,
+				fmt.Sprintf("%s(domain=%s cluster=%s dns_zone=%q)", svc.ID, svc.Domain, svc.ProxyCluster, svc.DNSZone))
 			continue
 		}
 
@@ -331,6 +335,10 @@ func (a *Account) SynthesizePrivateServiceZones(peerID string) []nbdns.CustomZon
 				svc.ID, svc.Domain, svc.ProxyCluster, len(proxyPeers), skippedDisconnected)
 		}
 	}
+	if len(skippedNoZoneApex) > 0 {
+		log.Debugf("private-zone synth: peer %s account %s skipped %d service(s) with no matching zone apex: %s",
+			peerID, a.Id, len(skippedNoZoneApex), strings.Join(skippedNoZoneApex, ", "))
+	}
 
 	out := make([]nbdns.CustomZone, 0, len(zonesByApex))
 	for _, zone := range zonesByApex {