Set the chart's placeholder version to 0.37.0

replicas and strategy: Recreate were the chart's only guard against the
archiver, notifier and migration races; v0.36.0 closed all three with
advisory locks and a conflict-resolving incident insert, which made
that guard redundant rather than load-bearing. Expose replicaCount
(new, no values.yaml key existed before) defaulting to 2, and switch
to strategy: RollingUpdate with no explicit maxUnavailable/maxSurge --
the 25%/25% default rounds to 0/1 at replicaCount: 2, which is already
zero-downtime.

The chart does not gate this on image.tag, so pointing it at a
pre-v0.36.0 image with the new default is a foot-gun by omission --
noted in both the values.yaml comment and the deployment.yaml comment,
not guarded in code, same as the chart does for every other
version-coupled assumption today.

Co-authored-by: Claude <noreply@anthropic.com>

charts/terdut-server/Chart.yaml

@@ -15,5 +15,5 @@ type: application
 # appVersion and image.tag in values.yaml no longer agree, and that is not an oversight:
 # image.tag stays "latest", which is what a local install actually pulls. appVersion is
 # metadata and drives nothing.
-version: 0.35.0
+version: 0.37.0
-appVersion: "v0.35.0"
+appVersion: "v0.37.0"

charts/terdut-server/templates/deployment.yaml

@@ -6,15 +6,19 @@ metadata:
   labels:
     {{- include "terdut-server.labels" . | nindent 4 }}
 spec:
-  replicas: 1
+  replicas: {{ .Values.replicaCount }}
   selector:
     matchLabels:
       {{- include "terdut-server.selectorLabels" . | nindent 6 }}
-  # Recreate, not RollingUpdate, even though the PVC that forced it is gone: the
+  # RollingUpdate, not Recreate: the sweeper, notifier and migration runner
-  # sweeper and the notifier are unsynchronised singletons, and two replicas
+  # each take a Postgres advisory lock around their own pass, and new-incident
-  # overlapping during a rollout would both page for the same incident.
+  # creation on the first webhook for a brand-new groupKey resolves its own
+  # insert conflict -- so two replicas overlapping during a rollout no longer
+  # double-page, race a migration, or drop a webhook payload (v0.36.0). No
+  # explicit maxUnavailable/maxSurge: the 25%/25% default rounds to 0/1 at
+  # replicaCount: 2, which is zero-downtime already.
   strategy:
-    type: Recreate
+    type: RollingUpdate
   template:
     metadata:
       labels:

charts/terdut-server/values.yaml

@@ -1,3 +1,10 @@
+# Safe above 1 since v0.36.0: the sweeper, notifier and migration runner each
+# take a Postgres advisory lock around their own pass, and a webhook that
+# loses the race to open a brand-new incident attaches to the winner's row
+# instead of dropping its payload. An image older than v0.36.0 does not have
+# these guards -- do not raise this against one.
+replicaCount: 2
+
 networking:
   hostname: "terdut.example.com"
   servicePort: 8080

internal/api/advisory_lock_test.go

@@ -0,0 +1,122 @@
+package api
+
+// This file is internal (package api, not api_test) because withAdvisoryLock is
+// unexported and these tests exercise its locking semantics directly rather than
+// through the full StartArchiver/StartNotifier loop, which would make the "does
+// not run while held" case timing-dependent instead of deterministic. It opens a
+// plain connection to TERDUT_TEST_DSN rather than reusing testdb_test.go's
+// newTestDB, since that helper lives in the separate, already-compiled
+// api_test package and a Postgres advisory lock needs no schema or migration
+// to exercise.
+
+import (
+	"context"
+	"database/sql"
+	"os"
+	"testing"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+)
+
+// advisoryTestDB opens a plain, unmigrated connection to the test database. An
+// unset DSN fails rather than skips, matching testdb_test.go's rationale: a
+// suite that quietly tests nothing is worse than one that does not run.
+func advisoryTestDB(t *testing.T) *sql.DB {
+	t.Helper()
+
+	dsn := os.Getenv("TERDUT_TEST_DSN")
+	if dsn == "" {
+		t.Fatalf("TERDUT_TEST_DSN is not set: these tests need Postgres.\n" +
+			"Run `make test-db` for a local one, then\n" +
+			"  export TERDUT_TEST_DSN=postgres://terdut:terdut@localhost:5432/terdut_test?sslmode=disable")
+	}
+
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatalf("connect to TERDUT_TEST_DSN: %v", err)
+	}
+	t.Cleanup(func() { db.Close() })
+	return db
+}
+
+func TestWithAdvisoryLock_RunsWhenFree(t *testing.T) {
+	db := advisoryTestDB(t)
+	ctx := context.Background()
+
+	ran := false
+	withAdvisoryLock(ctx, db, archiverLockKey, "test", func() { ran = true })
+
+	if !ran {
+		t.Fatal("fn did not run although the lock was free")
+	}
+}
+
+func TestWithAdvisoryLock_SkipsWhileHeldElsewhere(t *testing.T) {
+	db := advisoryTestDB(t)
+	ctx := context.Background()
+
+	// Hold the lock on a connection of our own, standing in for another
+	// replica mid-pass.
+	holder, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatalf("acquire holder connection: %v", err)
+	}
+	defer holder.Close()
+	if _, err := holder.ExecContext(ctx, "SELECT pg_advisory_lock($1)", archiverLockKey); err != nil {
+		t.Fatalf("pre-acquire lock: %v", err)
+	}
+
+	ran := false
+	withAdvisoryLock(ctx, db, archiverLockKey, "test", func() { ran = true })
+	if ran {
+		t.Fatal("fn ran although another connection already held the lock")
+	}
+
+	if _, err := holder.ExecContext(ctx, "SELECT pg_advisory_unlock($1)", archiverLockKey); err != nil {
+		t.Fatalf("release held lock: %v", err)
+	}
+
+	// Now that the holder released it, the next caller should get it.
+	ran = false
+	withAdvisoryLock(ctx, db, archiverLockKey, "test", func() { ran = true })
+	if !ran {
+		t.Fatal("fn did not run after the other connection released the lock")
+	}
+}
+
+func TestWithAdvisoryLock_ReleasesAfterFnReturns(t *testing.T) {
+	db := advisoryTestDB(t)
+	ctx := context.Background()
+
+	withAdvisoryLock(ctx, db, notifierLockKey, "test", func() {})
+
+	// If the first call had leaked the lock, this one would see it held and
+	// skip, leaving ran false.
+	ran := false
+	withAdvisoryLock(ctx, db, notifierLockKey, "test", func() { ran = true })
+	if !ran {
+		t.Fatal("fn did not run on a later call: the earlier call leaked its lock")
+	}
+}
+
+func TestWithAdvisoryLock_KeysAreIndependent(t *testing.T) {
+	db := advisoryTestDB(t)
+	ctx := context.Background()
+
+	holder, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatalf("acquire holder connection: %v", err)
+	}
+	defer holder.Close()
+	if _, err := holder.ExecContext(ctx, "SELECT pg_advisory_lock($1)", archiverLockKey); err != nil {
+		t.Fatalf("pre-acquire archiver lock: %v", err)
+	}
+	defer holder.ExecContext(ctx, "SELECT pg_advisory_unlock($1)", archiverLockKey)
+
+	// Holding archiverLockKey must not block notifierLockKey.
+	ran := false
+	withAdvisoryLock(ctx, db, notifierLockKey, "test", func() { ran = true })
+	if !ran {
+		t.Fatal("fn did not run under a different key although only archiverLockKey was held")
+	}
+}

internal/api/alertmanager.go

@@ -376,6 +376,17 @@ func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, team
 // its own. Hence the querier rather than a *sql.Tx. A nil severity leaves the
 // column for refreshSeverity to fill from the member alerts; the sweeper passes
 // one because its incidents have no members to derive it from.
+//
+// Both callers get here only after their own SELECT found no open incident for
+// this group_key — but on more than one replica, two webhook deliveries for the
+// very first occurrence of a brand-new group_key can both pass that SELECT
+// before either INSERTs. ON CONFLICT DO NOTHING against
+// incidents_open_group_key_idx is what makes the loser's INSERT a no-op instead
+// of a unique-violation error that would otherwise roll back its entire
+// payload; existingOpenIncident then hands it the winner's row. Postgres
+// resolves that conflict only once the winner's transaction has committed (or
+// rolled back), so by the time this RETURNING comes back empty, the winner's
+// row is guaranteed visible to that follow-up SELECT.
 func openIncident(ctx context.Context, q querier, notify NotifyConfig, teamID int64, groupKey, title string, groupLabels map[string]string, severity *string) (int64, error) {
 	onCall, err := currentOnCall(ctx, q, teamID)
 	if err != nil {
@@ -391,10 +402,18 @@ func openIncident(ctx context.Context, q querier, notify NotifyConfig, teamID in
 	err = q.QueryRowContext(ctx, `
 		INSERT INTO incidents (team_id, group_key, title, group_labels, signature, status, severity, triggered_at, assigned_to)
 		VALUES ($1, $2, $3, $4::jsonb, $5, 'triggered', $6, $7, $8)
+		ON CONFLICT (team_id, group_key) WHERE resolved_at IS NULL DO NOTHING
 		RETURNING id`,
 		teamID, groupKey, title, string(labelsJSON), incidentSignature(groupLabels, title), severity,
 		time.Now().Unix(), onCall).Scan(&id)
-	if err != nil {
+	switch {
+	case err == sql.ErrNoRows:
+		// Lost the race: someone else's incident for this group_key exists now.
+		// Everything below — the trigger event, assignment, page, escalation
+		// clock — already happened for that row when it was created; attach to
+		// it rather than fail this call (and the whole payload) outright.
+		return existingOpenIncident(ctx, q, teamID, groupKey)
+	case err != nil:
 		return 0, err
 	}
 
@@ -423,6 +442,21 @@ func openIncident(ctx context.Context, q querier, notify NotifyConfig, teamID in
 	return id, nil
 }
 
+// existingOpenIncident looks up the open incident openIncident's own INSERT just
+// lost a conflict against — the same lookup incidentForGroup does before ever
+// calling openIncident, repeated here for the caller that arrived second.
+func existingOpenIncident(ctx context.Context, q querier, teamID int64, groupKey string) (int64, error) {
+	var id int64
+	err := q.QueryRowContext(ctx,
+		"SELECT id FROM incidents WHERE team_id = $1 AND group_key = $2 AND resolved_at IS NULL",
+		teamID, groupKey,
+	).Scan(&id)
+	if err != nil {
+		return 0, err
+	}
+	return id, nil
+}
+
 // linkAlert adds an alert to an incident, emitting a timeline entry only the
 // first time. Re-sends of an already-linked alert are silent.
 func linkAlert(ctx context.Context, tx *sql.Tx, incidentID, alertID int64) error {

internal/api/alertmanager_test.go

@@ -0,0 +1,112 @@
+package api_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"sync"
+	"testing"
+)
+
+// TestWebhook_ConcurrentFirstOccurrenceOpensOneIncident reproduces two
+// replicas racing the very first webhook delivery for a brand-new group_key:
+// both see no open incident yet (incidentForGroup's own SELECT finds
+// nothing) and race openIncident's INSERT.
+//
+// The DB's own unique index already guarantees at most one incident either
+// way, with or without this fix — so "exactly one incident" alone cannot
+// tell a fixed run from a broken one. What ON CONFLICT handling actually
+// changes is what happens to the *loser*: before it, the loser's INSERT hit
+// incidents_open_group_key_idx's unique violation, which — since
+// upsertAlerts ran earlier in that same transaction — rolled back its whole
+// payload, alert insert included. ingest's error is only logged and
+// receiveWebhook answers 200 regardless, so nothing ever retried it: the
+// loser's alert silently never existed. That is the regression signal this
+// test checks — every caller's fingerprint must show up in /api/alerts, not
+// just the winner's.
+func TestWebhook_ConcurrentFirstOccurrenceOpensOneIncident(t *testing.T) {
+	s := newTS(t)
+
+	const callers = 8
+	const groupKey = "race-group"
+
+	// Every caller needs its own fingerprint. A shared one would serialize all
+	// of them at upsertAlerts' own ON CONFLICT (team_id, fingerprint) row lock,
+	// long before any of them reached incidentForGroup — which would hide the
+	// very race this test exists to force.
+	bodies := make([][]byte, callers)
+	for i := range callers {
+		payload := map[string]any{
+			"version":     "4",
+			"status":      "firing",
+			"groupKey":    groupKey,
+			"groupLabels": map[string]string{"alertname": "RaceAlert"},
+			"alerts": []map[string]any{amAlert(fmt.Sprintf("fp-race-%d", i), "RaceAlert", "firing",
+				"2026-05-20T10:00:00Z", "0001-01-01T00:00:00Z", nil)},
+		}
+		bodies[i], _ = json.Marshal(payload)
+	}
+
+	// A start line, so every request is fired as close to simultaneously as
+	// goroutine scheduling allows, rather than trickling out one dial at a
+	// time — the race window is the gap between incidentForGroup's SELECT and
+	// openIncident's INSERT, which a staggered start could easily miss.
+	var ready sync.WaitGroup
+	start := make(chan struct{})
+	statuses := make([]int, callers)
+	var wg sync.WaitGroup
+	for i := range callers {
+		ready.Add(1)
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			ready.Done()
+			<-start
+			resp, err := http.Post(s.URL+"/api/integrations/"+s.ingestKey+"/alertmanager",
+				"application/json", bytes.NewReader(bodies[i]))
+			if err != nil {
+				t.Errorf("post webhook #%d: %v", i, err)
+				return
+			}
+			defer resp.Body.Close()
+			statuses[i] = resp.StatusCode
+		}(i)
+	}
+	ready.Wait()
+	close(start)
+	wg.Wait()
+
+	for i, code := range statuses {
+		if code != http.StatusOK {
+			t.Errorf("webhook #%d returned %d, want 200", i, code)
+		}
+	}
+
+	var matched []any
+	for _, inc := range listIncidents(t, s, "") {
+		if inc["group_key"] == groupKey {
+			matched = append(matched, inc["id"])
+		}
+	}
+	if len(matched) != 1 {
+		t.Fatalf("expected exactly 1 incident for group_key %q after %d concurrent deliveries, got %d: %v",
+			groupKey, callers, len(matched), matched)
+	}
+
+	var alerts []map[string]any
+	decode(t, s.req(t, http.MethodGet, "/api/alerts", nil), &alerts)
+	seen := map[string]bool{}
+	for _, a := range alerts {
+		if fp, ok := a["fingerprint"].(string); ok {
+			seen[fp] = true
+		}
+	}
+	for i := range callers {
+		fp := fmt.Sprintf("fp-race-%d", i)
+		if !seen[fp] {
+			t.Errorf("alert %q is missing: its delivery's whole payload was silently rolled back "+
+				"when it lost the race for the incident", fp)
+		}
+	}
+}

internal/api/archiver.go

@@ -15,6 +15,12 @@ const (
 	// expiryGrace absorbs clock skew and notification latency before an alert
 	// whose ends_at watermark has passed is treated as stale.
 	expiryGrace = 5 * time.Minute
+
+	// archiverLockKey is the Postgres advisory lock the sweeper takes for the
+	// duration of each pass, so that running more than one replica does not run
+	// the sweep concurrently on all of them. Its value has no meaning beyond
+	// being distinct from notifierLockKey.
+	archiverLockKey int64 = 7265_0001
 )
 
 // StartArchiver runs the alert sweeper until ctx is cancelled, starting with an
@@ -23,15 +29,25 @@ const (
 // the fallback, not the setting: each pass reads the current value from the
 // settings table, so an administrator's change takes effect on the next tick
 // instead of at the next restart.
+//
+// Each pass runs under archiverLockKey (see withAdvisoryLock), so that on more
+// than one replica only whichever instance's tick takes the lock first actually
+// sweeps; the rest skip that tick rather than racing the same pass.
 func StartArchiver(ctx context.Context, db *sql.DB, archiveAfter, staleAfter time.Duration, notify NotifyConfig) {
 	ticker := time.NewTicker(sweepInterval)
 	defer ticker.Stop()
 
+	sweep := func() {
+		withAdvisoryLock(ctx, db, archiverLockKey, "sweeper", func() {
 			Sweep(ctx, db, archiveAfter, staleAfter, notify)
+		})
+	}
+
+	sweep()
 	for {
 		select {
 		case <-ticker.C:
-			Sweep(ctx, db, archiveAfter, staleAfter, notify)
+			sweep()
 		case <-ctx.Done():
 			return
 		}

internal/api/helpers.go

@@ -1,8 +1,11 @@
 package api
 
 import (
+	"context"
+	"database/sql"
 	"encoding/json"
 	"errors"
+	"log"
 	"net/http"
 	"strconv"
 	"strings"
@@ -77,3 +80,39 @@ func decodeJSON(r *http.Request, v any) error {
 func errResp(msg string) map[string]string {
 	return map[string]string{"error": msg}
 }
+
+// withAdvisoryLock runs fn only if it can take the named Postgres advisory lock on a
+// dedicated connection, and skips fn otherwise. This is what keeps the archiver and
+// notifier safe to run on more than one replica: whichever instance's tick gets there
+// first does the work; the rest see the lock held and simply wait for their next tick
+// instead of running the same pass concurrently.
+//
+// pg_try_advisory_lock is session-scoped, so taking and releasing it must happen on the
+// same connection, reserved via db.Conn rather than borrowed from the pool's shared
+// connections fn itself may use — and released (unlocked, then closed) before returning,
+// since a session lock otherwise outlives this call and leaks onto whatever reuses the
+// pooled connection next.
+func withAdvisoryLock(ctx context.Context, db *sql.DB, key int64, name string, fn func()) {
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		log.Printf("%s: advisory lock: acquire connection: %v", name, err)
+		return
+	}
+	defer conn.Close()
+
+	var locked bool
+	if err := conn.QueryRowContext(ctx, "SELECT pg_try_advisory_lock($1)", key).Scan(&locked); err != nil {
+		log.Printf("%s: advisory lock: %v", name, err)
+		return
+	}
+	if !locked {
+		return // another replica is already running this pass
+	}
+	defer func() {
+		if _, err := conn.ExecContext(ctx, "SELECT pg_advisory_unlock($1)", key); err != nil {
+			log.Printf("%s: advisory unlock: %v", name, err)
+		}
+	}()
+
+	fn()
+}

internal/api/notifier.go

@@ -38,6 +38,13 @@ const (
 	ackTokenTTL = 24 * time.Hour
 )
 
+// notifierLockKey is the Postgres advisory lock the notifier takes for the
+// duration of each pass, so that running more than one replica does not
+// deliver (or double-deliver) the same notification from more than one of
+// them at once. Its value has no meaning beyond being distinct from
+// archiverLockKey.
+const notifierLockKey int64 = 7265_0002
+
 // Notification kinds, recording why a push was sent.
 const (
 	notifyTriggered = "triggered"
@@ -97,6 +104,10 @@ var notifyClient = &http.Client{Timeout: 10 * time.Second}
 
 // StartNotifier delivers queued notifications until ctx is cancelled, starting
 // with an immediate pass so a restart flushes whatever the last one left behind.
+//
+// Each pass runs under notifierLockKey (see withAdvisoryLock), so that on more
+// than one replica only whichever instance's tick takes the lock first actually
+// delivers; the rest skip that tick rather than racing the same pass.
 func StartNotifier(ctx context.Context, db *sql.DB, cfg NotifyConfig) {
 	if !cfg.enabled() {
 		log.Print("notifier: disabled (no ntfy URL configured)")
@@ -107,11 +118,17 @@ func StartNotifier(ctx context.Context, db *sql.DB, cfg NotifyConfig) {
 	ticker := time.NewTicker(notifyInterval)
 	defer ticker.Stop()
 
+	sweep := func() {
+		withAdvisoryLock(ctx, db, notifierLockKey, "notifier", func() {
 			NotifySweep(ctx, db, cfg)
+		})
+	}
+
+	sweep()
 	for {
 		select {
 		case <-ticker.C:
-			NotifySweep(ctx, db, cfg)
+			sweep()
 		case <-ctx.Done():
 			return
 		}

internal/db/db.go

@@ -1,6 +1,7 @@
 package db
 
 import (
+	"context"
 	"database/sql"
 	"embed"
 	"fmt"
@@ -62,6 +63,16 @@ func Open(dsn string) (*sql.DB, error) {
 	}
 }
 
+// migrationLockKey is the Postgres advisory lock Migrate holds for its whole
+// run. Two replicas starting at once would otherwise race the check-then-apply
+// loop below against schema_migrations: the loser could crash on a
+// duplicate-key insert, or contend with the winner's uncommitted DDL. Blocking
+// (pg_advisory_lock, not pg_try_advisory_lock as the archiver and notifier
+// use): on boot there is no later tick to defer to, so the right behaviour is
+// to wait for the other replica to finish migrating, not to skip ahead and
+// start serving against an unmigrated schema.
+const migrationLockKey int64 = 7265_0003
+
 // Migrate applies every embedded migration that has not been applied yet, in
 // filename order, recording each in schema_migrations.
 //
@@ -69,6 +80,22 @@ func Open(dsn string) (*sql.DB, error) {
 // migration that failed half way used to leave the schema in whatever state it
 // had reached. Postgres has transactional DDL, so the rollback is real.
 func Migrate(db *sql.DB) error {
+	ctx := context.Background()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		return fmt.Errorf("migrate: acquire connection: %w", err)
+	}
+	defer conn.Close()
+
+	if _, err := conn.ExecContext(ctx, "SELECT pg_advisory_lock($1)", migrationLockKey); err != nil {
+		return fmt.Errorf("migrate: acquire advisory lock: %w", err)
+	}
+	defer func() {
+		if _, err := conn.ExecContext(ctx, "SELECT pg_advisory_unlock($1)", migrationLockKey); err != nil {
+			log.Printf("migrate: release advisory lock: %v", err)
+		}
+	}()
+
 	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
 		version    TEXT PRIMARY KEY,
 		applied_at BIGINT NOT NULL DEFAULT FLOOR(EXTRACT(EPOCH FROM now()))::bigint

internal/db/db_test.go

@@ -0,0 +1,125 @@
+package db_test
+
+import (
+	"database/sql"
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+	"sync"
+	"testing"
+
+	"git.ryuvia.com/niklas/terdut-server/internal/db"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+)
+
+// TERDUT_TEST_DSN must point at a database the test role may create schemas
+// in; see internal/api/testdb_test.go for the fuller rationale this mirrors.
+// An unset DSN fails rather than skips, deliberately.
+const testDSNEnv = "TERDUT_TEST_DSN"
+
+// TestMigrate_ConcurrentCallersDoNotRace reproduces two replicas starting at
+// once against a brand-new, unmigrated schema: both call db.Migrate at the
+// same time. Before migrationLockKey, the loser could crash on a
+// duplicate-key insert into schema_migrations, or contend with the winner's
+// uncommitted DDL; with the advisory lock, one blocks until the other
+// finishes and both return cleanly.
+func TestMigrate_ConcurrentCallersDoNotRace(t *testing.T) {
+	dsn := os.Getenv(testDSNEnv)
+	if dsn == "" {
+		t.Fatalf("%s is not set: these tests need Postgres.\n"+
+			"Run `make test-db` for a local one, then\n"+
+			"  export %s=postgres://terdut:terdut@localhost:5432/terdut_test?sslmode=disable",
+			testDSNEnv, testDSNEnv)
+	}
+
+	schema := fmt.Sprintf("migrate_race_%d", os.Getpid())
+	admin, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatalf("connect to %s: %v", testDSNEnv, err)
+	}
+	defer admin.Close()
+	if _, err := admin.Exec("CREATE SCHEMA " + schema); err != nil {
+		t.Fatalf("create schema %s: %v", schema, err)
+	}
+	t.Cleanup(func() {
+		cleanup, err := sql.Open("pgx", dsn)
+		if err != nil {
+			return
+		}
+		defer cleanup.Close()
+		if _, err := cleanup.Exec("DROP SCHEMA " + schema + " CASCADE"); err != nil {
+			t.Logf("drop schema %s: %v", schema, err)
+		}
+	})
+
+	scoped := withSearchPath(dsn, schema)
+
+	const callers = 2
+	errs := make([]error, callers)
+	var wg sync.WaitGroup
+	for i := range callers {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			database, err := db.Open(scoped)
+			if err != nil {
+				errs[i] = fmt.Errorf("open: %w", err)
+				return
+			}
+			defer database.Close()
+			errs[i] = db.Migrate(database)
+		}(i)
+	}
+	wg.Wait()
+
+	for i, err := range errs {
+		if err != nil {
+			t.Fatalf("Migrate #%d: %v", i, err)
+		}
+	}
+
+	entries, err := os.ReadDir("migrations")
+	if err != nil {
+		t.Fatalf("read migrations dir: %v", err)
+	}
+	var want int
+	for _, e := range entries {
+		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
+			want++
+		}
+	}
+
+	check, err := sql.Open("pgx", scoped)
+	if err != nil {
+		t.Fatalf("connect for verification: %v", err)
+	}
+	defer check.Close()
+
+	var got int
+	if err := check.QueryRow("SELECT COUNT(*) FROM schema_migrations").Scan(&got); err != nil {
+		t.Fatalf("count schema_migrations: %v", err)
+	}
+	if got != want {
+		t.Fatalf("schema_migrations has %d row(s) after two concurrent Migrate calls, want %d (one per migration file, no duplicates)", got, want)
+	}
+}
+
+// withSearchPath pins a DSN to one schema. Copied from
+// internal/api/testdb_test.go rather than shared: that helper lives in the
+// api_test package, a separate compiled package this one cannot import.
+func withSearchPath(dsn, schema string) string {
+	opt := "-csearch_path=" + schema
+
+	if strings.HasPrefix(dsn, "postgres://") || strings.HasPrefix(dsn, "postgresql://") {
+		u, err := url.Parse(dsn)
+		if err == nil {
+			q := u.Query()
+			q.Set("options", opt)
+			u.RawQuery = q.Encode()
+			return u.String()
+		}
+	}
+	return dsn + " options='" + opt + "'"
+}

internal/web/static/app.css

@@ -255,7 +255,6 @@ input:focus, textarea:focus { outline: none; border-color: var(--accent); box-sh
 /* Hidden here (shown from 900px below): on the phone bar the team switcher
    lives in the topbar instead, as #team-selector-mobile. */
 .nav-team-selector { display: none; }
-.nav-link-secondary { display: none; }
 .nav-link {
   position: relative;
   /* flex: 1 spreads the tabs evenly across the bar's width; the desktop
@@ -267,6 +266,10 @@ input:focus, textarea:focus { outline: none; border-color: var(--accent); box-sh
      what stops six tabs widening the bar past the screen. */
   min-width: 0; padding: 0 2px;
 }
+/* Must come after .nav-link above: same specificity (one class each), so
+   whichever is later in the file wins for an element wearing both classes,
+   and this needs to beat .nav-link's display:flex here on the phone bar. */
+.nav-link-secondary { display: none; }
 .nav-label {
   max-width: 100%; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
 }
@@ -323,6 +326,7 @@ input:focus, textarea:focus { outline: none; border-color: var(--accent); box-sh
 /* ---------- chips ---------- */
 
 .chips {
+  position: relative;
   display: flex; gap: 6px;
   padding: 12px 16px 8px;
   overflow-x: auto; scrollbar-width: none;
@@ -338,11 +342,14 @@ input:focus, textarea:focus { outline: none; border-color: var(--accent); box-sh
 }
 .chip[aria-selected="true"] { background: var(--text); border-color: var(--text); color: var(--bg); }
 .chip .count { margin-left: 4px; opacity: 0.7; }
-/* Pinned to the visible right edge of the scrolling row (sticky, not
+/* An overlay, not a flex item: absolute against .chips' own (non-scrolling)
-   absolute, so it tracks the scroll position rather than the content). */
+   box stays flush with its real right edge regardless of scroll position,
+   which turned out not to be true of position:sticky here — as a flex
+   item, its sticky offset interacted with the row's gap and its own
+   negative margin, landing short of the edge by about one gap's width. */
 .chips-fade {
-  position: sticky; right: -1px; flex: none;
+  position: absolute; top: 0; right: 0; bottom: 0;
-  width: 24px; margin-left: -24px;
+  width: 24px;
   background: linear-gradient(to right, transparent, var(--bg));
   pointer-events: none;
 }