diff --git a/README.md b/README.md
index ee4d561..faf5ddf 100644
--- a/README.md
+++ b/README.md
@@ -459,6 +459,16 @@ nobody can delete or demote themselves.
 Endpoints that require the flag answer `403` with
 `{"error":"administrator access required"}`.
 
+**Teams** are the unit of tenancy, and are a separate axis from the administrator
+flag. A team owns its incidents, alerts, schedule and integrations, and a user
+sees exactly the teams they belong to — an administrator is not implicitly in
+every team, because administration is about accounts, not about reading other
+people's incidents. Within a team an **owner** configures it (schedule,
+integrations, membership) and a **member** works its incidents.
+
+Anything belonging to a team you are not in answers `404`, not `403`: whether an
+incident exists is itself something only its team should learn.
+
 | Method | Path | Description |
 |---|---|---|
 | `POST` | `/api/login` | `{"username","password"}` → sets the session cookie, returns `{user, has_password}`. `429` after too many failures |
@@ -487,9 +497,32 @@ on anybody's.
 
 ### Alert ingestion
 
+Alerts arrive on a team's integration key. The key is both the credential and the
+routing: it says that the sender may post, and which team the alerts belong to.
+Create one with `POST /api/teams/{teamID}/integrations`, which returns the key
+and the full URL once and stores only a SHA-256 hash.
+
 | Method | Path | Description |
 |---|---|---|
-| `POST` | `/api/alertmanager/webhook` | Alertmanager v4 webhook receiver (no auth) |
+| `POST` | `/api/integrations/{key}/alertmanager` | Alertmanager v4 webhook receiver for the key's team. `401` for an unknown key |
+| `POST` | `/api/alertmanager/webhook` | **Deprecated, unauthenticated.** The pre-teams receiver, kept for one release so an upgrade does not stop delivering while the Alertmanager config is edited. Routes everything to the oldest team |
+
+The deprecated path is why anything that can reach the port can still open an
+incident. Move senders to a key and it goes away.
+
+### Teams
+
+| Method | Path | Who | Description |
+|---|---|---|---|
+| `GET` | `/api/teams` | any | The caller's own teams, each with their role |
+| `POST` | `/api/teams` | any | Create a team `{"name"}`; the creator becomes its first owner |
+| `DELETE` | `/api/teams/{teamID}` | **owner** | Delete a team and everything under it. `409` while it has open incidents |
+| `GET` | `/api/teams/{teamID}/members` | member | Who is in the team |
+| `POST` | `/api/teams/{teamID}/members` | **owner** | Add a member, or change their role `{"user_id","role"}` |
+| `DELETE` | `/api/teams/{teamID}/members/{userID}` | **owner** | Remove a member. `409` for the last owner |
+| `GET` | `/api/teams/{teamID}/integrations` | member | List integrations. Never returns keys |
+| `POST` | `/api/teams/{teamID}/integrations` | **owner** | Mint an integration `{"name","kind"}` — key and URL shown once |
+| `DELETE` | `/api/teams/{teamID}/integrations/{integrationID}` | **owner** | Revoke an integration |
 
 ### Notifications
 
@@ -676,13 +709,23 @@ unknown" rather than being rejected.
 
 | Method | Path | Description |
 |---|---|---|
-| `POST` | `/api/schedule` | Assign user to dates `{"user_id", "dates":["YYYY-MM-DD",...], "replace"}` — all-or-nothing |
-| `GET` | `/api/schedule` | List entries. Filters: `?from=YYYY-MM-DD`, `?to=YYYY-MM-DD` |
-| `GET` | `/api/schedule/current` | Today's on-call user (UTC), 404 if none |
-| `DELETE` | `/api/schedule/{id}` | Remove schedule entry |
+Each team keeps its own rota, so two teams can have two different people on call
+on the same day. The person taking a shift has to be in the team — paging
+somebody who cannot open the incident is worse than paging nobody.
+
+| Method | Path | Who | Description |
+|---|---|---|---|
+| `POST` | `/api/teams/{teamID}/schedule` | **owner** | Assign user to dates `{"user_id", "dates":["YYYY-MM-DD",...], "replace"}` — all-or-nothing |
+| `GET` | `/api/teams/{teamID}/schedule` | member | List entries. Filters: `?from=YYYY-MM-DD`, `?to=YYYY-MM-DD` |
+| `DELETE` | `/api/teams/{teamID}/schedule/{id}` | **owner** | Remove schedule entry |
+| `GET` | `/api/schedule/current` | any | Who is on call today (UTC) in **every** team the caller is in — one entry per team, `[]` when nobody anywhere |
 
 ### Statistics
 
+Every figure counts the caller's own teams only: a report that counted other
+teams' incidents would leak their volume, and their alert names through the
+top-alerts list, and would not be a number about the reader's work anyway.
+
 All stat endpoints accept optional `?from=YYYY-MM-DD` and `?to=YYYY-MM-DD`, and exclude archived rows to match the default list views. Alert stats filter on `received_at`; incident stats filter on `triggered_at`.
 
 | Method | Path | Description |
@@ -699,6 +742,31 @@ averages over incidents that have actually been acknowledged or resolved, and ar
 
 ---
 
+## Upgrading to teams
+
+Everything that existed before teams moves into one team called **Default**, and
+every existing user becomes an owner of it. The upgrade is a no-op for the
+people using it: the same queue, the same schedule, the same incidents, with a
+name on them.
+
+What changes, and will need attention:
+
+- **Alert ingestion moved.** `POST /api/alertmanager/webhook` still works but is
+  deprecated and unauthenticated, and routes everything to the oldest team. Mint
+  a key with `POST /api/teams/{teamID}/integrations` and point Alertmanager at
+  the URL it returns. The old path goes away in a later release.
+- **The schedule endpoints moved** under `/api/teams/{teamID}/schedule`, and
+  editing the rota is now an owner's job. `GET /api/schedule/current` stayed
+  where it was but now returns an **array** — one entry per team with somebody
+  on call — instead of a single object or a 404. This is a breaking API change
+  for anything that reads it, terdut-tui included.
+- **Uniqueness is per team now.** Two teams can legitimately see the same alert
+  fingerprint, the same Alertmanager groupKey, and put somebody on call on the
+  same date.
+
+Nothing else about an incident changes, and incidents never move between teams:
+an alert belongs to whichever team's key it arrived on.
+
 ## Upgrading to roles
 
 Before this release every authenticated caller could create and delete users,
diff --git a/internal/api/admin_test.go b/internal/api/admin_test.go
index 2ac083a..97f199d 100644
--- a/internal/api/admin_test.go
+++ b/internal/api/admin_test.go
@@ -35,6 +35,15 @@ func member(t *testing.T, s *ts, username string) (id int64, call func(method, p
 		t.Fatalf("a created user must not be an administrator")
 	}
 
+	// Into the default team as a plain member: being in a team is what lets
+	// somebody work its incidents, and is separate from administering accounts.
+	resp = s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/members",
+		map[string]any{"user_id": user.ID, "role": "member"})
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("add %s to the team: %d", username, resp.StatusCode)
+	}
+
 	resp = s.req(t, http.MethodPost, "/api/users/"+id64(user.ID)+"/api-keys",
 		map[string]string{"name": "test"})
 	if resp.StatusCode != http.StatusCreated {
diff --git a/internal/api/alertmanager.go b/internal/api/alertmanager.go
index 2190e60..f714970 100644
--- a/internal/api/alertmanager.go
+++ b/internal/api/alertmanager.go
@@ -4,9 +4,12 @@ import (
 	"context"
 	"database/sql"
 	"encoding/json"
+	"errors"
 	"log"
 	"net/http"
 	"time"
+
+	"github.com/go-chi/chi/v5"
 )
 
 // Values for alerts.resolution_source, recording why an alert left the firing
@@ -70,36 +73,76 @@ type ingested struct {
 	deadman bool
 }
 
-func handleAlertmanagerWebhook(db *sql.DB, notify NotifyConfig, deadman DeadmanConfig) http.HandlerFunc {
+// handleIntegrationWebhook receives alerts on a team's own integration key.
+// The key in the path is both the credential and the routing: it says who may
+// post, and which team the alerts belong to.
+func handleIntegrationWebhook(db *sql.DB, notify NotifyConfig, deadman DeadmanConfig) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		var payload amPayload
-		if err := decodeJSON(r, &payload); err != nil {
-			respond(w, http.StatusBadRequest, errResp("invalid payload"))
+		teamID, err := teamIDForKey(r.Context(), db, chi.URLParam(r, "key"))
+		if err != nil {
+			if errors.Is(err, errUnknownIntegration) {
+				// 401 and not 404: the path is real, the key is not, and a
+				// sender misconfigured this way should say so in its own logs
+				// rather than believe it is delivering.
+				respond(w, http.StatusUnauthorized, errResp("unknown integration key"))
+				return
+			}
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
 			return
 		}
-
-		// Alertmanager retries anything that is not 2xx, and a retry of a payload
-		// we failed to store is more useful than an error it cannot act on — so
-		// failures are logged, not surfaced.
-		if err := ingest(r.Context(), db, notify, deadman, payload); err != nil {
-			log.Printf("webhook ingest (group %q): %v", payload.GroupKey, err)
-		}
-
-		w.WriteHeader(http.StatusOK)
+		receiveWebhook(w, r, db, notify, deadman, teamID)
 	}
 }
 
+// handleLegacyWebhook is the pre-teams unauthenticated endpoint, kept for one
+// release so an upgrade does not silently stop delivering while somebody edits
+// the Alertmanager config. It routes to the oldest team, which on an upgraded
+// install is the Default team everything was moved into.
+//
+// It is deprecated and unauthenticated — anything that can reach the port can
+// open an incident. Move senders to an integration key and this goes away.
+func handleLegacyWebhook(db *sql.DB, notify NotifyConfig, deadman DeadmanConfig) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, err := defaultTeamID(r.Context(), db)
+		if err != nil {
+			log.Printf("legacy webhook: no team to route to: %v", err)
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+		log.Printf("legacy webhook: unauthenticated payload routed to team %d; "+
+			"move this sender to an integration key", teamID)
+		receiveWebhook(w, r, db, notify, deadman, teamID)
+	}
+}
+
+func receiveWebhook(w http.ResponseWriter, r *http.Request, db *sql.DB, notify NotifyConfig, deadman DeadmanConfig, teamID int64) {
+	var payload amPayload
+	if err := decodeJSON(r, &payload); err != nil {
+		respond(w, http.StatusBadRequest, errResp("invalid payload"))
+		return
+	}
+
+	// Alertmanager retries anything that is not 2xx, and a retry of a payload
+	// we failed to store is more useful than an error it cannot act on — so
+	// failures are logged, not surfaced.
+	if err := ingest(r.Context(), db, notify, deadman, teamID, payload); err != nil {
+		log.Printf("webhook ingest (team %d, group %q): %v", teamID, payload.GroupKey, err)
+	}
+
+	w.WriteHeader(http.StatusOK)
+}
+
 // ingest stores a payload's alerts and reconciles the incident for its group.
 // The whole payload is one transaction: an incident that opened but whose alerts
 // failed to link would be a work item nobody could act on.
-func ingest(ctx context.Context, db *sql.DB, notify NotifyConfig, deadman DeadmanConfig, payload amPayload) error {
+func ingest(ctx context.Context, db *sql.DB, notify NotifyConfig, deadman DeadmanConfig, teamID int64, payload amPayload) error {
 	tx, err := db.BeginTx(ctx, nil)
 	if err != nil {
 		return err
 	}
 	defer tx.Rollback() //nolint:errcheck
 
-	accepted, err := upsertAlerts(ctx, tx, deadman, payload.Alerts)
+	accepted, err := upsertAlerts(ctx, tx, deadman, teamID, payload.Alerts)
 	if err != nil {
 		return err
 	}
@@ -108,7 +151,7 @@ func ingest(ctx context.Context, db *sql.DB, notify NotifyConfig, deadman Deadma
 	// resolution cascade are recomputed once per incident at the end.
 	touched := map[int64]bool{}
 
-	incidentID, err := incidentForGroup(ctx, tx, notify, payload, accepted)
+	incidentID, err := incidentForGroup(ctx, tx, notify, teamID, payload, accepted)
 	if err != nil {
 		return err
 	}
@@ -156,7 +199,7 @@ func ingest(ctx context.Context, db *sql.DB, notify NotifyConfig, deadman Deadma
 
 // upsertAlerts stores each alert of a payload and reports what changed. Payloads
 // the ordering guard rejected are left out entirely.
-func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts []amAlert) ([]ingested, error) {
+func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, teamID int64, alerts []amAlert) ([]ingested, error) {
 	now := time.Now().Unix()
 	accepted := make([]ingested, 0, len(alerts))
 
@@ -171,7 +214,8 @@ func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts
 		var prevStartsAt int64
 		existed := true
 		switch err := tx.QueryRowContext(ctx,
-			"SELECT status, starts_at FROM alerts WHERE fingerprint = $1", a.Fingerprint,
+			"SELECT status, starts_at FROM alerts WHERE team_id = $1 AND fingerprint = $2",
+			teamID, a.Fingerprint,
 		).Scan(&prevStatus, &prevStartsAt); {
 		case err == sql.ErrNoRows:
 			existed = false
@@ -210,10 +254,10 @@ func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts
 		// undone by a stale retry.
 		if _, err := tx.ExecContext(ctx, `
 			INSERT INTO alerts
-				(fingerprint, name, status, labels, annotations, starts_at, ends_at,
+				(team_id, fingerprint, name, status, labels, annotations, starts_at, ends_at,
 				 generator_url, received_at, resolution_source)
-			VALUES ($1, $2, $3, $4::jsonb, $5::jsonb, $6, $7, $8, $9, $10)
-			ON CONFLICT (fingerprint) DO UPDATE SET
+			VALUES ($1, $2, $3, $4, $5::jsonb, $6::jsonb, $7, $8, $9, $10, $11)
+			ON CONFLICT (team_id, fingerprint) DO UPDATE SET
 				status            = excluded.status,
 				labels            = excluded.labels,
 				annotations       = excluded.annotations,
@@ -233,7 +277,7 @@ func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts
 			   OR (excluded.starts_at = alerts.starts_at
 			       AND (alerts.resolution_source = '`+resolutionDeadman+`'
 			            OR NOT (alerts.status = 'resolved' AND excluded.status = 'firing')))`,
-			a.Fingerprint, name, a.Status,
+			teamID, a.Fingerprint, name, a.Status,
 			string(labelsJSON), string(annotationsJSON),
 			a.StartsAt.Unix(), endsAtUnix,
 			a.GeneratorURL, now, resolutionSource,
@@ -245,7 +289,8 @@ func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts
 		var curStatus string
 		var curStartsAt int64
 		if err := tx.QueryRowContext(ctx,
-			"SELECT id, status, starts_at FROM alerts WHERE fingerprint = $1", a.Fingerprint,
+			"SELECT id, status, starts_at FROM alerts WHERE team_id = $1 AND fingerprint = $2",
+			teamID, a.Fingerprint,
 		).Scan(&id, &curStatus, &curStartsAt); err != nil {
 			return nil, err
 		}
@@ -284,7 +329,7 @@ func upsertAlerts(ctx context.Context, tx *sql.Tx, deadman DeadmanConfig, alerts
 // Heartbeats do not count as anything here. A group of nothing but dead man's
 // switch alerts opens no incident at all, and a mixed group gets an incident for
 // its real alerts only.
-func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, payload amPayload, accepted []ingested) (int64, error) {
+func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, teamID int64, payload amPayload, accepted []ingested) (int64, error) {
 	var firstName string
 	anyFiring, anyNew := false, false
 	for _, a := range accepted {
@@ -315,7 +360,8 @@ func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, payl
 
 	var id int64
 	switch err := tx.QueryRowContext(ctx,
-		"SELECT id FROM incidents WHERE group_key = $1 AND resolved_at IS NULL", groupKey,
+		"SELECT id FROM incidents WHERE team_id = $1 AND group_key = $2 AND resolved_at IS NULL",
+		teamID, groupKey,
 	).Scan(&id); {
 	case err == nil:
 		return id, nil
@@ -326,7 +372,7 @@ func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, payl
 	if !anyNew {
 		return 0, nil
 	}
-	return openIncident(ctx, tx, notify, groupKey,
+	return openIncident(ctx, tx, notify, teamID, groupKey,
 		incidentTitle(payload.GroupLabels, firstName), payload.GroupLabels, nil)
 }
 
@@ -338,8 +384,8 @@ func incidentForGroup(ctx context.Context, tx *sql.Tx, notify NotifyConfig, payl
 // 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.
-func openIncident(ctx context.Context, q querier, notify NotifyConfig, groupKey, title string, groupLabels map[string]string, severity *string) (int64, error) {
-	onCall, err := currentOnCall(ctx, q)
+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 {
 		return 0, err
 	}
@@ -351,10 +397,10 @@ func openIncident(ctx context.Context, q querier, notify NotifyConfig, groupKey,
 
 	var id int64
 	err = q.QueryRowContext(ctx, `
-		INSERT INTO incidents (group_key, title, group_labels, status, severity, triggered_at, assigned_to)
-		VALUES ($1, $2, $3::jsonb, 'triggered', $4, $5, $6)
+		INSERT INTO incidents (team_id, group_key, title, group_labels, status, severity, triggered_at, assigned_to)
+		VALUES ($1, $2, $3, $4::jsonb, 'triggered', $5, $6, $7)
 		RETURNING id`,
-		groupKey, title, string(labelsJSON), severity,
+		teamID, groupKey, title, string(labelsJSON), severity,
 		time.Now().Unix(), onCall).Scan(&id)
 	if err != nil {
 		return 0, err
diff --git a/internal/api/alerts.go b/internal/api/alerts.go
index f9d666a..a2b0b2b 100644
--- a/internal/api/alerts.go
+++ b/internal/api/alerts.go
@@ -19,7 +19,7 @@ import (
 // incident_alerts rather than as a column here, because one alert row is reused
 // across occurrences and belongs to a different incident each time.
 const alertSelectFrom = `
-	SELECT a.id, a.fingerprint, a.name, a.status,
+	SELECT a.id, a.team_id, t.name, a.fingerprint, a.name, a.status,
 	       a.labels, a.annotations,
 	       a.starts_at, a.ends_at, a.generator_url, a.received_at,
 	       (SELECT ia.incident_id
@@ -29,7 +29,8 @@ const alertSelectFrom = `
 	         ORDER BY i.triggered_at DESC, i.id DESC
 	         LIMIT 1),
 	       a.resolution_source, a.archived_at
-	FROM   alerts a`
+	FROM   alerts a
+	JOIN   teams t ON t.id = a.team_id`
 
 func handleListAlerts(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -38,6 +39,13 @@ func handleListAlerts(db *sql.DB) http.HandlerFunc {
 		where := []string{}
 		args := &sqlArgs{}
 
+		where = append(where, "a.team_id = ANY("+args.add(callerTeamIDs(r.Context()))+")")
+		if team := q.Get("team_id"); team != "" {
+			if n, err := strconv.ParseInt(team, 10, 64); err == nil {
+				where = append(where, "a.team_id = "+args.add(n))
+			}
+		}
+
 		if status := q.Get("status"); status != "" {
 			where = append(where, "a.status = "+args.add(status))
 		}
@@ -107,7 +115,7 @@ func handleGetAlert(db *sql.DB) http.HandlerFunc {
 			respond(w, http.StatusBadRequest, errResp("invalid alert id"))
 			return
 		}
-		a, err := fetchAlert(r.Context(), db, id)
+		a, err := fetchAlert(r.Context(), db, id, callerTeamIDs(r.Context()))
 		if err == sql.ErrNoRows {
 			respond(w, http.StatusNotFound, errResp("alert not found"))
 			return
@@ -121,8 +129,9 @@ func handleGetAlert(db *sql.DB) http.HandlerFunc {
 }
 
 // fetchAlert loads a single alert by ID using the shared query.
-func fetchAlert(ctx context.Context, db *sql.DB, id int64) (models.Alert, error) {
-	return scanAlert(db.QueryRowContext(ctx, alertSelectFrom+" WHERE a.id = $1", id))
+func fetchAlert(ctx context.Context, db *sql.DB, id int64, teamIDs []int64) (models.Alert, error) {
+	return scanAlert(db.QueryRowContext(ctx,
+		alertSelectFrom+" WHERE a.id = $1 AND a.team_id = ANY($2)", id, teamIDs))
 }
 
 // scanner is satisfied by both *sql.Row and *sql.Rows.
@@ -137,7 +146,7 @@ func scanAlert(s scanner) (models.Alert, error) {
 	var endsAtUnix, archivedAtUnix *int64
 
 	if err := s.Scan(
-		&a.ID, &a.Fingerprint, &a.Name, &a.Status,
+		&a.ID, &a.TeamID, &a.TeamName, &a.Fingerprint, &a.Name, &a.Status,
 		&labelsJSON, &annotationsJSON,
 		&startsAtUnix, &endsAtUnix,
 		&a.GeneratorURL, &receivedAtUnix,
diff --git a/internal/api/api_test.go b/internal/api/api_test.go
index 5092b69..dfd9a0c 100644
--- a/internal/api/api_test.go
+++ b/internal/api/api_test.go
@@ -276,14 +276,14 @@ func TestAlertUpsert_DifferentFingerprintsStored(t *testing.T) {
 func TestSchedule_ConflictOnSameDate(t *testing.T) {
 	s := newTS(t)
 
-	first := s.req(t, http.MethodPost, "/api/schedule",
+	first := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-01"}})
 	if first.StatusCode != http.StatusCreated {
 		t.Fatalf("first assignment returned %d", first.StatusCode)
 	}
 	first.Body.Close()
 
-	second := s.req(t, http.MethodPost, "/api/schedule",
+	second := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-01"}})
 	if second.StatusCode != http.StatusConflict {
 		t.Errorf("expected 409 on duplicate date, got %d", second.StatusCode)
@@ -295,11 +295,11 @@ func TestSchedule_MultiDateRollbackOnConflict(t *testing.T) {
 	s := newTS(t)
 
 	// Claim 2026-06-10 first.
-	s.req(t, http.MethodPost, "/api/schedule",
+	s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-10"}}).Body.Close()
 
 	// Try to assign two dates in one request where the second conflicts.
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-09", "2026-06-10"}})
 	if resp.StatusCode != http.StatusConflict {
 		t.Fatalf("expected 409, got %d", resp.StatusCode)
@@ -307,7 +307,7 @@ func TestSchedule_MultiDateRollbackOnConflict(t *testing.T) {
 	resp.Body.Close()
 
 	// 2026-06-09 must NOT have been committed (transaction rolled back).
-	listResp := s.req(t, http.MethodGet, "/api/schedule?from=2026-06-09&to=2026-06-09", nil)
+	listResp := s.req(t, http.MethodGet, "/api/teams/"+defaultTeam+"/schedule?from=2026-06-09&to=2026-06-09", nil)
 	var entries []any
 	decode(t, listResp, &entries)
 	if len(entries) != 0 {
@@ -321,21 +321,35 @@ func TestSchedule_MultiDateRollbackOnConflict(t *testing.T) {
 
 // addUser creates a second person to hand a shift to. The bootstrap user is
 // admin, id 1.
+// addUser creates a user and puts them in the default team, because a user who
+// is in no team can be paged by nobody and take no shift — which is the rule
+// these tests exercise around, not the one they are testing.
 func addUser(t *testing.T, s *ts, username string) {
 	t.Helper()
 	resp := s.req(t, http.MethodPost, "/api/users",
 		map[string]any{"username": username, "email": username + "@test.com"})
-	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusCreated {
+		resp.Body.Close()
 		t.Fatalf("create user returned %d", resp.StatusCode)
 	}
+	var user struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, resp, &user)
+
+	member := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/members",
+		map[string]any{"user_id": user.ID, "role": "member"})
+	defer member.Body.Close()
+	if member.StatusCode != http.StatusNoContent {
+		t.Fatalf("add %s to the team returned %d", username, member.StatusCode)
+	}
 }
 
 // scheduleHolder reports who is on call for one date, or "" for nobody.
 func scheduleHolder(t *testing.T, s *ts, date string) string {
 	t.Helper()
 	var entries []map[string]any
-	decode(t, s.req(t, http.MethodGet, "/api/schedule?from="+date+"&to="+date, nil), &entries)
+	decode(t, s.req(t, http.MethodGet, "/api/teams/"+defaultTeam+"/schedule?from="+date+"&to="+date, nil), &entries)
 	if len(entries) == 0 {
 		return ""
 	}
@@ -347,10 +361,10 @@ func TestSchedule_ReplaceTakesAnAssignedDate(t *testing.T) {
 	s := newTS(t)
 	addUser(t, s, "alex")
 
-	s.req(t, http.MethodPost, "/api/schedule",
+	s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-01"}}).Body.Close()
 
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 2, "dates": []string{"2026-06-01"}, "replace": true})
 	if resp.StatusCode != http.StatusCreated {
 		t.Fatalf("expected replace to succeed, got %d", resp.StatusCode)
@@ -364,7 +378,7 @@ func TestSchedule_ReplaceTakesAnAssignedDate(t *testing.T) {
 	// One row, not two: two entries for a date would mean two people believing
 	// they are on call for it.
 	var entries []map[string]any
-	decode(t, s.req(t, http.MethodGet, "/api/schedule?from=2026-06-01&to=2026-06-01", nil), &entries)
+	decode(t, s.req(t, http.MethodGet, "/api/teams/"+defaultTeam+"/schedule?from=2026-06-01&to=2026-06-01", nil), &entries)
 	if len(entries) != 1 {
 		t.Errorf("expected exactly one entry for the date, got %d", len(entries))
 	}
@@ -376,11 +390,11 @@ func TestSchedule_ReplaceMixedWeek(t *testing.T) {
 	s := newTS(t)
 	addUser(t, s, "alex")
 
-	s.req(t, http.MethodPost, "/api/schedule",
+	s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-02", "2026-06-04"}}).Body.Close()
 
 	week := []string{"2026-06-01", "2026-06-02", "2026-06-03", "2026-06-04", "2026-06-05"}
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 2, "dates": week, "replace": true})
 	if resp.StatusCode != http.StatusCreated {
 		t.Fatalf("expected the mixed week to succeed, got %d", resp.StatusCode)
@@ -399,10 +413,10 @@ func TestSchedule_ReplaceDefaultsOff(t *testing.T) {
 	s := newTS(t)
 	addUser(t, s, "alex")
 
-	s.req(t, http.MethodPost, "/api/schedule",
+	s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-01"}}).Body.Close()
 
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 2, "dates": []string{"2026-06-01"}})
 	if resp.StatusCode != http.StatusConflict {
 		t.Fatalf("expected 409 without replace, got %d", resp.StatusCode)
@@ -420,7 +434,7 @@ func TestSchedule_ReplaceDefaultsOff(t *testing.T) {
 func TestSchedule_ReplaceCollapsesRepeatedDates(t *testing.T) {
 	s := newTS(t)
 
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{"2026-06-01", "2026-06-01"}, "replace": true})
 	if resp.StatusCode != http.StatusCreated {
 		t.Fatalf("expected a repeated date to be accepted under replace, got %d", resp.StatusCode)
@@ -428,7 +442,7 @@ func TestSchedule_ReplaceCollapsesRepeatedDates(t *testing.T) {
 	resp.Body.Close()
 
 	var entries []map[string]any
-	decode(t, s.req(t, http.MethodGet, "/api/schedule?from=2026-06-01&to=2026-06-01", nil), &entries)
+	decode(t, s.req(t, http.MethodGet, "/api/teams/"+defaultTeam+"/schedule?from=2026-06-01&to=2026-06-01", nil), &entries)
 	if len(entries) != 1 {
 		t.Errorf("expected one entry for the repeated date, got %d", len(entries))
 	}
diff --git a/internal/api/deadman.go b/internal/api/deadman.go
index e1e524d..8c1fa91 100644
--- a/internal/api/deadman.go
+++ b/internal/api/deadman.go
@@ -171,6 +171,7 @@ func ParseDeadmanConfig(matchers string, timeout time.Duration, severity string)
 // deadmanAlert is one switch: the alert row carrying its last heartbeat.
 type deadmanAlert struct {
 	id          int64
+	teamID      int64
 	fingerprint string
 	labels      map[string]string
 	matcher     DeadmanMatcher
@@ -236,7 +237,7 @@ func deadmanAlerts(ctx context.Context, db *sql.DB, cfg DeadmanConfig) ([]deadma
 	}
 
 	rows, err := db.QueryContext(ctx, `
-		SELECT id, fingerprint, labels, status, received_at
+		SELECT id, team_id, fingerprint, labels, status, received_at
 		FROM   alerts
 		WHERE  name IN (`+args.addList(nameList)+`)
 		  AND  archived_at IS NULL`, args.all()...)
@@ -249,7 +250,7 @@ func deadmanAlerts(ctx context.Context, db *sql.DB, cfg DeadmanConfig) ([]deadma
 	for rows.Next() {
 		var a deadmanAlert
 		var labelsJSON, status string
-		if err := rows.Scan(&a.id, &a.fingerprint, &labelsJSON, &status, &a.receivedAt); err != nil {
+		if err := rows.Scan(&a.id, &a.teamID, &a.fingerprint, &labelsJSON, &status, &a.receivedAt); err != nil {
 			return nil, err
 		}
 		json.Unmarshal([]byte(labelsJSON), &a.labels) //nolint:errcheck
@@ -280,8 +281,8 @@ func deadmanDied(ctx context.Context, db *sql.DB, cfg DeadmanConfig, notify Noti
 	if err := db.QueryRowContext(ctx, `
 		SELECT COALESCE(MAX(triggered_at), 0),
 		       COUNT(*) FILTER (WHERE resolved_at IS NULL)
-		FROM   incidents WHERE group_key = $1`,
-		sw.groupKey()).Scan(&lastTriggered, &open); err != nil {
+		FROM   incidents WHERE team_id = $1 AND group_key = $2`,
+		sw.teamID, sw.groupKey()).Scan(&lastTriggered, &open); err != nil {
 		return err
 	}
 	if open > 0 || sw.receivedAt <= lastTriggered {
@@ -314,7 +315,9 @@ func deadmanDied(ctx context.Context, db *sql.DB, cfg DeadmanConfig, notify Noti
 		sev = &severity
 	}
 
-	incidentID, err := openIncident(ctx, tx, notify, sw.groupKey(),
+	// The incident opens in the team whose integration received the heartbeat:
+	// the switch belongs to whoever is watching that source, not to the install.
+	incidentID, err := openIncident(ctx, tx, notify, sw.teamID, sw.groupKey(),
 		"No heartbeat from "+sw.matcher.String(), sw.labels, sev)
 	if err != nil {
 		return err
@@ -343,7 +346,8 @@ func deadmanRecovered(ctx context.Context, db *sql.DB, sw deadmanAlert) error {
 	var incidentID int64
 	switch err := db.QueryRowContext(ctx, `
 		SELECT id FROM incidents
-		 WHERE group_key = $1 AND resolved_at IS NULL`, sw.groupKey()).Scan(&incidentID); {
+		 WHERE team_id = $1 AND group_key = $2 AND resolved_at IS NULL`,
+		sw.teamID, sw.groupKey()).Scan(&incidentID); {
 	case err == sql.ErrNoRows:
 		return nil
 	case err != nil:
diff --git a/internal/api/incident_store.go b/internal/api/incident_store.go
index 26def15..63d2d1f 100644
--- a/internal/api/incident_store.go
+++ b/internal/api/incident_store.go
@@ -51,12 +51,13 @@ type querier interface {
 }
 
 const incidentSelectFrom = `
-	SELECT i.id, i.group_key, i.title, i.group_labels, i.status, i.severity,
+	SELECT i.id, i.team_id, t.name, i.group_key, i.title, i.group_labels, i.status, i.severity,
 	       i.triggered_at,
 	       i.acknowledged_by, i.acknowledged_at, ack.username,
 	       i.assigned_to, asg.username, i.snoozed_until,
 	       i.resolved_at, i.resolution_source, i.archived_at
 	FROM   incidents i
+	JOIN   teams t ON t.id = i.team_id
 	LEFT   JOIN users ack ON ack.id = i.acknowledged_by
 	LEFT   JOIN users asg ON asg.id = i.assigned_to`
 
@@ -67,7 +68,7 @@ func scanIncident(s scanner) (models.Incident, error) {
 	var ackAt, snoozedUntil, resolvedAt, archivedAt *int64
 
 	if err := s.Scan(
-		&i.ID, &i.GroupKey, &i.Title, &groupLabelsJSON, &i.Status, &i.Severity,
+		&i.ID, &i.TeamID, &i.TeamName, &i.GroupKey, &i.Title, &groupLabelsJSON, &i.Status, &i.Severity,
 		&triggeredAt,
 		&i.AcknowledgedByID, &ackAt, &i.AcknowledgedByUser,
 		&i.AssignedToID, &i.AssignedToUser, &snoozedUntil,
@@ -113,12 +114,17 @@ func todayUTC() string {
 	return time.Now().UTC().Format("2006-01-02")
 }
 
-// currentOnCall returns today's on-call user, or nil when nobody is scheduled.
-// A missing schedule entry is not an error — incidents just open unassigned.
-func currentOnCall(ctx context.Context, q querier) (*int64, error) {
+// currentOnCall returns a team's on-call user for today, or nil when nobody is
+// scheduled. A missing schedule entry is not an error — incidents just open
+// unassigned.
+//
+// Per team: each team keeps its own rota, so two teams can have two different
+// people on call on the same day, which was the point of scoping the schedule.
+func currentOnCall(ctx context.Context, q querier, teamID int64) (*int64, error) {
 	var userID int64
 	err := q.QueryRowContext(ctx,
-		"SELECT user_id FROM schedule_entries WHERE date = $1", todayUTC()).Scan(&userID)
+		"SELECT user_id FROM schedule_entries WHERE team_id = $1 AND date = $2",
+		teamID, todayUTC()).Scan(&userID)
 	if err == sql.ErrNoRows {
 		return nil, nil
 	}
diff --git a/internal/api/incidents.go b/internal/api/incidents.go
index 3369676..756b037 100644
--- a/internal/api/incidents.go
+++ b/internal/api/incidents.go
@@ -19,6 +19,15 @@ func handleListIncidents(db *sql.DB) http.HandlerFunc {
 		where := []string{}
 		args := &sqlArgs{}
 
+		// The combined queue: every team the caller belongs to, in one list. A
+		// caller in no team sees an empty queue rather than everybody's.
+		where = append(where, "i.team_id = ANY("+args.add(callerTeamIDs(r.Context()))+")")
+		if team := q.Get("team_id"); team != "" {
+			if n, err := strconv.ParseInt(team, 10, 64); err == nil {
+				where = append(where, "i.team_id = "+args.add(n))
+			}
+		}
+
 		// Without an explicit status the queue shows open work, which is what an
 		// on-call person opens the tool to see.
 		if status := q.Get("status"); status != "" {
@@ -96,7 +105,7 @@ func handleListIncidents(db *sql.DB) http.HandlerFunc {
 
 func handleGetIncident(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -119,7 +128,7 @@ func handleGetIncident(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentAlerts(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -137,7 +146,7 @@ func handleIncidentAlerts(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentTimeline(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -176,7 +185,7 @@ func handleIncidentTimeline(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentAcknowledge(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -199,7 +208,7 @@ func handleIncidentAcknowledge(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentUnacknowledge(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -223,7 +232,7 @@ func handleIncidentUnacknowledge(db *sql.DB) http.HandlerFunc {
 // re-send of an alert that never stopped firing. Use snooze for "not now".
 func handleIncidentResolve(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -244,7 +253,7 @@ func handleIncidentResolve(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentAssign(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -285,7 +294,7 @@ func handleIncidentAssign(db *sql.DB) http.HandlerFunc {
 // {"duration": "2h"}.
 func handleIncidentSnooze(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -340,7 +349,7 @@ func handleIncidentSnooze(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentUnsnooze(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -359,7 +368,7 @@ func handleIncidentUnsnooze(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentArchive(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -379,7 +388,7 @@ func handleIncidentArchive(db *sql.DB) http.HandlerFunc {
 
 func handleIncidentUnarchive(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -401,7 +410,7 @@ func handleIncidentUnarchive(db *sql.DB) http.HandlerFunc {
 // single query renders the whole story of an incident in order.
 func handleCreateNote(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -448,7 +457,7 @@ func handleCreateNote(db *sql.DB) http.HandlerFunc {
 // rest of the timeline is what actually happened, and is not editable.
 func handleDeleteNote(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		id, ok := incidentIDParam(w, r)
+		id, ok := incidentIDParam(w, r, db)
 		if !ok {
 			return
 		}
@@ -479,19 +488,32 @@ func handleDeleteNote(db *sql.DB) http.HandlerFunc {
 // Shared handler plumbing
 // ---------------------------------------------------------------------------
 
-func incidentIDParam(w http.ResponseWriter, r *http.Request) (int64, bool) {
+// incidentIDParam reads {id} from the path AND confirms the incident belongs to
+// a team the caller is in. Both in one place, deliberately: every incident route
+// goes through here, so scoping cannot be forgotten by writing a new handler
+// that only remembers the first half.
+//
+// An incident in somebody else's team is reported as not found rather than
+// forbidden, because "there is an incident 41 you may not see" is itself
+// something only that team should know.
+func incidentIDParam(w http.ResponseWriter, r *http.Request, db *sql.DB) (int64, bool) {
 	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
 	if err != nil {
 		respond(w, http.StatusBadRequest, errResp("invalid incident id"))
 		return 0, false
 	}
+	if !incidentExists(w, r, db, id) {
+		return 0, false
+	}
 	return id, true
 }
 
+// incidentExists reports whether the incident is one the caller may see at all.
 func incidentExists(w http.ResponseWriter, r *http.Request, db *sql.DB, id int64) bool {
 	var exists int
 	if err := db.QueryRowContext(r.Context(),
-		"SELECT 1 FROM incidents WHERE id = $1", id).Scan(&exists); err != nil {
+		"SELECT 1 FROM incidents WHERE id = $1 AND team_id = ANY($2)",
+		id, callerTeamIDs(r.Context())).Scan(&exists); err != nil {
 		respond(w, http.StatusNotFound, errResp("incident not found"))
 		return false
 	}
diff --git a/internal/api/incidents_test.go b/internal/api/incidents_test.go
index 04757d1..745c0cd 100644
--- a/internal/api/incidents_test.go
+++ b/internal/api/incidents_test.go
@@ -425,7 +425,7 @@ func TestIncident_AutoAssignedToCurrentOnCall(t *testing.T) {
 	s := newTS(t)
 
 	today := time.Now().UTC().Format("2006-01-02")
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": 1, "dates": []string{today}})
 	if resp.StatusCode != http.StatusCreated {
 		t.Fatalf("schedule assignment returned %d", resp.StatusCode)
diff --git a/internal/api/middleware.go b/internal/api/middleware.go
index 7058ca2..0e983b9 100644
--- a/internal/api/middleware.go
+++ b/internal/api/middleware.go
@@ -17,6 +17,7 @@ type contextKey string
 const (
 	ctxUser    contextKey = "user"
 	ctxSession contextKey = "session"
+	ctxTeams   contextKey = "teams"
 )
 
 // AuthMiddleware accepts either of the two credentials the server issues: an
@@ -151,7 +152,17 @@ func serveAs(w http.ResponseWriter, r *http.Request, next http.Handler, db *sql.
 	}
 	u.CreatedAt = time.Unix(createdUnix, 0).UTC()
 
-	ctx := context.WithValue(r.Context(), ctxUser, u)
+	// Every scoped query needs the caller's teams, so they are loaded once here
+	// rather than per handler. One extra round trip per request, against a
+	// table with one row per membership.
+	teams, err := callerMemberships(r.Context(), db, userID)
+	if err != nil {
+		respond(w, http.StatusInternalServerError, errResp("internal error"))
+		return
+	}
+
+	ctx := context.WithValue(r.Context(), ctxTeams, teams)
+	ctx = context.WithValue(ctx, ctxUser, u)
 	if sessionID != 0 {
 		ctx = context.WithValue(ctx, ctxSession, sessionID)
 	}
@@ -168,6 +179,90 @@ func userFromContext(ctx context.Context) (models.User, bool) {
 	return u, ok
 }
 
+// membership is the caller's role in one team.
+type membership struct {
+	teamID int64
+	role   string
+}
+
+func callerMemberships(ctx context.Context, db *sql.DB, userID int64) ([]membership, error) {
+	rows, err := db.QueryContext(ctx,
+		"SELECT team_id, role FROM team_members WHERE user_id = $1 ORDER BY team_id", userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []membership
+	for rows.Next() {
+		var m membership
+		if err := rows.Scan(&m.teamID, &m.role); err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}
+
+// callerTeamIDs lists the teams the caller belongs to, for the `team_id = ANY`
+// filter every list query carries. An admin is NOT implicitly in every team:
+// administration is about accounts, not about reading other people's incidents,
+// and an admin who needs to see a team's queue can add themselves to it.
+func callerTeamIDs(ctx context.Context) []int64 {
+	ms, _ := ctx.Value(ctxTeams).([]membership)
+	ids := make([]int64, 0, len(ms))
+	for _, m := range ms {
+		ids = append(ids, m.teamID)
+	}
+	return ids
+}
+
+// callerRole reports the caller's role in one team, and whether they are in it
+// at all.
+func callerRole(ctx context.Context, teamID int64) (string, bool) {
+	ms, _ := ctx.Value(ctxTeams).([]membership)
+	for _, m := range ms {
+		if m.teamID == teamID {
+			return m.role, true
+		}
+	}
+	return "", false
+}
+
+// requireTeamMember answers the request and reports false unless the caller
+// belongs to teamID.
+//
+// 404, not 403: whether a team exists is itself something only its members
+// should learn, and the same reasoning applies to every incident and alert
+// under it.
+func requireTeamMember(w http.ResponseWriter, r *http.Request, teamID int64) bool {
+	if _, ok := callerRole(r.Context(), teamID); !ok {
+		respond(w, http.StatusNotFound, errResp("not found"))
+		return false
+	}
+	return true
+}
+
+// requireTeamOwner is requireTeamMember for the things only an owner may change:
+// the schedule, the integrations and who is in the team. A system administrator
+// passes without being a member, because somebody has to be able to repair a
+// team whose owner has left.
+func requireTeamOwner(w http.ResponseWriter, r *http.Request, teamID int64) bool {
+	role, ok := callerRole(r.Context(), teamID)
+	if ok && role == models.RoleOwner {
+		return true
+	}
+	if caller, _ := userFromContext(r.Context()); caller.IsAdmin {
+		return true
+	}
+	if !ok {
+		respond(w, http.StatusNotFound, errResp("not found"))
+		return false
+	}
+	respond(w, http.StatusForbidden, errResp("team owner access required"))
+	return false
+}
+
 // sessionFromContext returns the id of the session a request was authenticated
 // with, or false for an API-key request.
 func sessionFromContext(ctx context.Context) (int64, bool) {
diff --git a/internal/api/notify_test.go b/internal/api/notify_test.go
index 7b29a2f..3b4dc0b 100644
--- a/internal/api/notify_test.go
+++ b/internal/api/notify_test.go
@@ -95,7 +95,7 @@ func notifyTS(t *testing.T, cfg api.NotifyConfig) (*ts, *fakeNtfy) {
 func putOnCall(t *testing.T, s *ts, userID int) {
 	t.Helper()
 	today := time.Now().UTC().Format("2006-01-02")
-	resp := s.req(t, http.MethodPost, "/api/schedule",
+	resp := s.req(t, http.MethodPost, "/api/teams/"+defaultTeam+"/schedule",
 		map[string]any{"user_id": userID, "dates": []string{today}})
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusCreated {
diff --git a/internal/api/router.go b/internal/api/router.go
index 2f0a2da..e42b79b 100644
--- a/internal/api/router.go
+++ b/internal/api/router.go
@@ -27,9 +27,18 @@ func NewRouter(db *sql.DB, notify NotifyConfig, deadman DeadmanConfig) http.Hand
 	// the scoped token in its path rather than an API key, and has to stay
 	// reachable from outside the cluster for the button to work.
 	r.Post("/api/bootstrap", handleBootstrap(db))
-	r.Post("/api/alertmanager/webhook", handleAlertmanagerWebhook(db, notify, deadman))
 	r.Post("/api/notify/ack/{token}", handleNotifyAck(db))
 
+	// Alert ingestion. The key in the path says both that the sender may post
+	// and which team the alerts belong to, which is why it needs no session.
+	r.Post("/api/integrations/{key}/alertmanager", handleIntegrationWebhook(db, notify, deadman))
+
+	// DEPRECATED, and unauthenticated: anything that can reach the port can
+	// open an incident here. Kept for one release so an upgrade does not stop
+	// delivering while the Alertmanager config is edited; it routes everything
+	// to the oldest team. Remove it once senders carry a key.
+	r.Post("/api/alertmanager/webhook", handleLegacyWebhook(db, notify, deadman))
+
 	// Signing in to the web UI. Login trades a password for a session cookie,
 	// which AuthMiddleware accepts in place of an API key.
 	r.Post("/api/login", handleLogin(db, newLoginLimiter(), notify.PublicURL))
@@ -84,10 +93,26 @@ func NewRouter(db *sql.DB, notify NotifyConfig, deadman DeadmanConfig) http.Hand
 		r.Post("/api/incidents/{id}/notes", handleCreateNote(db))
 		r.Delete("/api/incidents/{id}/notes/{eventID}", handleDeleteNote(db))
 
-		r.Post("/api/schedule", handleCreateSchedule(db))
-		r.Get("/api/schedule/current", handleCurrentSchedule(db)) // must be before /{id}
-		r.Get("/api/schedule", handleListSchedule(db))
-		r.Delete("/api/schedule/{id}", handleDeleteSchedule(db))
+		// Teams. A user sees the teams they belong to; an owner configures one.
+		r.Get("/api/teams", handleListTeams(db))
+		r.Post("/api/teams", handleCreateTeam(db))
+		r.Delete("/api/teams/{teamID}", handleDeleteTeam(db))
+		r.Get("/api/teams/{teamID}/members", handleListTeamMembers(db))
+		r.Post("/api/teams/{teamID}/members", handleAddTeamMember(db))
+		r.Delete("/api/teams/{teamID}/members/{userID}", handleRemoveTeamMember(db))
+
+		// Integrations: where a team's alerts come in, and the key that says so.
+		r.Get("/api/teams/{teamID}/integrations", handleListIntegrations(db))
+		r.Post("/api/teams/{teamID}/integrations", handleCreateIntegration(db, notify.PublicURL))
+		r.Delete("/api/teams/{teamID}/integrations/{integrationID}", handleDeleteIntegration(db))
+
+		// The rota is per team. /api/schedule/current is the exception: it
+		// answers across every team the caller is in, which is what somebody on
+		// two rotas wants to see.
+		r.Get("/api/schedule/current", handleCurrentSchedule(db))
+		r.Post("/api/teams/{teamID}/schedule", handleCreateSchedule(db))
+		r.Get("/api/teams/{teamID}/schedule", handleListSchedule(db))
+		r.Delete("/api/teams/{teamID}/schedule/{id}", handleDeleteSchedule(db))
 
 		r.Get("/api/stats/incidents", handleStatsIncidents(db))
 		r.Get("/api/stats/alerts", handleStatsAlerts(db))
diff --git a/internal/api/schedule.go b/internal/api/schedule.go
index 9e96501..6374592 100644
--- a/internal/api/schedule.go
+++ b/internal/api/schedule.go
@@ -12,8 +12,18 @@ import (
 	"github.com/go-chi/chi/v5"
 )
 
+// The schedule is per team: each team keeps its own rota, so two teams can have
+// two different people on call on the same day. Editing it is an owner's job,
+// like the rest of a team's configuration; reading it is any member's.
 func handleCreateSchedule(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
 		var req struct {
 			UserID int64    `json:"user_id"`
 			Dates  []string `json:"dates"`
@@ -43,10 +53,13 @@ func handleCreateSchedule(db *sql.DB) http.HandlerFunc {
 			}
 		}
 
-		// Verify the user exists.
+		// The person taking the shift has to be in the team: paging somebody
+		// who cannot open the incident is worse than paging nobody.
 		var exists int
-		if err := db.QueryRowContext(r.Context(), "SELECT 1 FROM users WHERE id = $1", req.UserID).Scan(&exists); err != nil {
-			respond(w, http.StatusNotFound, errResp("user not found"))
+		if err := db.QueryRowContext(r.Context(),
+			"SELECT 1 FROM team_members WHERE team_id = $1 AND user_id = $2",
+			teamID, req.UserID).Scan(&exists); err != nil {
+			respond(w, http.StatusNotFound, errResp("user is not a member of this team"))
 			return
 		}
 
@@ -64,13 +77,15 @@ func handleCreateSchedule(db *sql.DB) http.HandlerFunc {
 		for _, d := range req.Dates {
 			if req.Replace {
 				if _, err := tx.ExecContext(r.Context(),
-					"DELETE FROM schedule_entries WHERE date = $1", d); err != nil {
+					"DELETE FROM schedule_entries WHERE team_id = $1 AND date = $2",
+					teamID, d); err != nil {
 					respond(w, http.StatusInternalServerError, errResp("internal error"))
 					return
 				}
 			}
 			if _, err := tx.ExecContext(r.Context(),
-				"INSERT INTO schedule_entries (user_id, date) VALUES ($1, $2)", req.UserID, d); err != nil {
+				"INSERT INTO schedule_entries (team_id, user_id, date) VALUES ($1, $2, $3)",
+				teamID, req.UserID, d); err != nil {
 				if isUniqueViolation(err) {
 					respond(w, http.StatusConflict,
 						errResp("date already assigned: "+d+" (pass replace to take it)"))
@@ -90,7 +105,7 @@ func handleCreateSchedule(db *sql.DB) http.HandlerFunc {
 		for _, d := range req.Dates {
 			dateSet[d] = true
 		}
-		all, err := scheduleRange(r.Context(), db, req.Dates[0], req.Dates[len(req.Dates)-1])
+		all, err := scheduleRange(r.Context(), db, teamID, req.Dates[0], req.Dates[len(req.Dates)-1])
 		if err != nil {
 			respond(w, http.StatusInternalServerError, errResp("internal error"))
 			return
@@ -107,6 +122,13 @@ func handleCreateSchedule(db *sql.DB) http.HandlerFunc {
 
 func handleListSchedule(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamMember(w, r, teamID) {
+			return
+		}
 		q := r.URL.Query()
 		from, to := q.Get("from"), q.Get("to")
 
@@ -123,7 +145,7 @@ func handleListSchedule(db *sql.DB) http.HandlerFunc {
 			}
 		}
 
-		entries, err := scheduleRange(r.Context(), db, from, to)
+		entries, err := scheduleRange(r.Context(), db, teamID, from, to)
 		if err != nil {
 			respond(w, http.StatusInternalServerError, errResp("internal error"))
 			return
@@ -134,12 +156,20 @@ func handleListSchedule(db *sql.DB) http.HandlerFunc {
 
 func handleDeleteSchedule(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
 		id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
 		if err != nil {
 			respond(w, http.StatusBadRequest, errResp("invalid schedule id"))
 			return
 		}
-		res, err := db.ExecContext(r.Context(), "DELETE FROM schedule_entries WHERE id = $1", id)
+		res, err := db.ExecContext(r.Context(),
+			"DELETE FROM schedule_entries WHERE id = $1 AND team_id = $2", id, teamID)
 		if err != nil {
 			respond(w, http.StatusInternalServerError, errResp("internal error"))
 			return
@@ -152,35 +182,50 @@ func handleDeleteSchedule(db *sql.DB) http.HandlerFunc {
 	}
 }
 
+// handleCurrentSchedule answers "who is on call right now" for every team the
+// caller belongs to — one entry per team, so somebody on two rotas sees both.
+// A team with nobody scheduled today simply does not appear.
 func handleCurrentSchedule(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		today := time.Now().UTC().Format("2006-01-02")
 
-		var e models.ScheduleEntry
-		var ts int64
-		err := db.QueryRowContext(r.Context(), `
-			SELECT s.id, s.user_id, u.username, s.date, s.created_at
+		rows, err := db.QueryContext(r.Context(), `
+			SELECT s.id, s.team_id, t.name, s.user_id, u.username, s.date, s.created_at
 			FROM   schedule_entries s
 			JOIN   users u ON u.id = s.user_id
-			WHERE  s.date = $1`, today).Scan(&e.ID, &e.UserID, &e.Username, &e.Date, &ts)
-		if err == sql.ErrNoRows {
-			respond(w, http.StatusNotFound, errResp("no one is on call today"))
-			return
-		}
+			JOIN   teams t ON t.id = s.team_id
+			WHERE  s.date = $1 AND s.team_id = ANY($2)
+			ORDER  BY t.name`, today, callerTeamIDs(r.Context()))
 		if err != nil {
 			respond(w, http.StatusInternalServerError, errResp("internal error"))
 			return
 		}
-		e.CreatedAt = time.Unix(ts, 0).UTC()
-		respond(w, http.StatusOK, e)
+		defer rows.Close()
+
+		entries := []models.ScheduleEntry{}
+		for rows.Next() {
+			var e models.ScheduleEntry
+			var ts int64
+			if err := rows.Scan(&e.ID, &e.TeamID, &e.TeamName, &e.UserID, &e.Username, &e.Date, &ts); err != nil {
+				respond(w, http.StatusInternalServerError, errResp("internal error"))
+				return
+			}
+			e.CreatedAt = time.Unix(ts, 0).UTC()
+			entries = append(entries, e)
+		}
+		if err := rows.Err(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		respond(w, http.StatusOK, entries)
 	}
 }
 
 // scheduleRange returns schedule entries ordered by date.
 // from and to are YYYY-MM-DD strings; an empty string means unbounded on that side.
-func scheduleRange(ctx context.Context, db *sql.DB, from, to string) ([]models.ScheduleEntry, error) {
-	where := []string{}
+func scheduleRange(ctx context.Context, db *sql.DB, teamID int64, from, to string) ([]models.ScheduleEntry, error) {
 	args := &sqlArgs{}
+	where := []string{"s.team_id = " + args.add(teamID)}
 	if from != "" {
 		where = append(where, "s.date >= "+args.add(from))
 	}
@@ -188,15 +233,13 @@ func scheduleRange(ctx context.Context, db *sql.DB, from, to string) ([]models.S
 		where = append(where, "s.date <= "+args.add(to))
 	}
 
-	clause := "1=1"
-	if len(where) > 0 {
-		clause = strings.Join(where, " AND ")
-	}
+	clause := strings.Join(where, " AND ")
 
 	rows, err := db.QueryContext(ctx, `
-		SELECT s.id, s.user_id, u.username, s.date, s.created_at
+		SELECT s.id, s.team_id, t.name, s.user_id, u.username, s.date, s.created_at
 		FROM   schedule_entries s
 		JOIN   users u ON u.id = s.user_id
+		JOIN   teams t ON t.id = s.team_id
 		WHERE  `+clause+`
 		ORDER  BY s.date ASC`, args.all()...)
 	if err != nil {
@@ -208,7 +251,7 @@ func scheduleRange(ctx context.Context, db *sql.DB, from, to string) ([]models.S
 	for rows.Next() {
 		var e models.ScheduleEntry
 		var ts int64
-		if err := rows.Scan(&e.ID, &e.UserID, &e.Username, &e.Date, &ts); err != nil {
+		if err := rows.Scan(&e.ID, &e.TeamID, &e.TeamName, &e.UserID, &e.Username, &e.Date, &ts); err != nil {
 			return nil, err
 		}
 		e.CreatedAt = time.Unix(ts, 0).UTC()
diff --git a/internal/api/stats.go b/internal/api/stats.go
index 01f0ce6..bd55be6 100644
--- a/internal/api/stats.go
+++ b/internal/api/stats.go
@@ -11,7 +11,7 @@ import (
 
 func handleStatsAlerts(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		where, args := statsFilter(r.URL.Query(), "received_at")
+		where, args := statsFilter(r.URL.Query(), "received_at", callerTeamIDs(r.Context()))
 
 		// COALESCE because SUM over zero rows is NULL, not 0, and a count of
 		// nothing is 0 — without it an empty window is a 500 rather than a
@@ -37,7 +37,7 @@ func handleStatsAlerts(db *sql.DB) http.HandlerFunc {
 
 func handleStatsTop(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		where, args := statsFilter(r.URL.Query(), "received_at")
+		where, args := statsFilter(r.URL.Query(), "received_at", callerTeamIDs(r.Context()))
 
 		limit := 10
 		if l := r.URL.Query().Get("limit"); l != "" {
@@ -79,7 +79,7 @@ func handleStatsTop(db *sql.DB) http.HandlerFunc {
 
 func handleStatsByHour(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		where, args := statsFilter(r.URL.Query(), "received_at")
+		where, args := statsFilter(r.URL.Query(), "received_at", callerTeamIDs(r.Context()))
 
 		rows, err := db.QueryContext(r.Context(), fmt.Sprintf(`
 			SELECT EXTRACT(HOUR FROM to_timestamp(received_at) AT TIME ZONE 'UTC')::int AS hr,
@@ -119,7 +119,7 @@ func handleStatsByHour(db *sql.DB) http.HandlerFunc {
 
 func handleStatsByDay(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		where, args := statsFilter(r.URL.Query(), "received_at")
+		where, args := statsFilter(r.URL.Query(), "received_at", callerTeamIDs(r.Context()))
 
 		// Postgres EXTRACT(DOW …) → 0=Sunday … 6=Saturday, the same numbering
 		// SQLite's strftime('%w') returned, so the frontend needs no change.
@@ -167,7 +167,7 @@ func handleStatsByDay(db *sql.DB) http.HandlerFunc {
 // mutated in place and carry no acknowledgement or closure time.
 func handleStatsIncidents(db *sql.DB) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		where, args := statsFilter(r.URL.Query(), "triggered_at")
+		where, args := statsFilter(r.URL.Query(), "triggered_at", callerTeamIDs(r.Context()))
 
 		// The counts are COALESCEd because SUM over zero rows is NULL, not 0.
 		// The averages are not: mtta and mttr stay null on purpose, since zero
@@ -206,9 +206,13 @@ func handleStatsIncidents(db *sql.DB) http.HandlerFunc {
 // statsFilter builds a WHERE clause and args from optional ?from and ?to query
 // params, filtering on timeCol. Archived rows are always excluded, matching the
 // default list views.
-func statsFilter(q url.Values, timeCol string) (where string, args *sqlArgs) {
+//
+// teamIDs scopes every figure to the caller's own teams: a report that counted
+// other teams' incidents would leak their volume and their names through the
+// top-alerts list, and would not be a number about the reader's work anyway.
+func statsFilter(q url.Values, timeCol string, teamIDs []int64) (where string, args *sqlArgs) {
 	args = &sqlArgs{}
-	clauses := []string{"archived_at IS NULL"}
+	clauses := []string{"archived_at IS NULL", "team_id = ANY(" + args.add(teamIDs) + ")"}
 	if from := q.Get("from"); from != "" {
 		if t, err := time.Parse("2006-01-02", from); err == nil {
 			clauses = append(clauses, timeCol+" >= "+args.add(t.UTC().Unix()))
diff --git a/internal/api/teams.go b/internal/api/teams.go
new file mode 100644
index 0000000..24523e4
--- /dev/null
+++ b/internal/api/teams.go
@@ -0,0 +1,473 @@
+package api
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.ryuvia.com/niklas/terdut-server/internal/models"
+	"github.com/go-chi/chi/v5"
+)
+
+// handleListTeams lists the caller's own teams, each with their role in it. An
+// administrator listing every team goes through the admin endpoint instead:
+// this one answers "what am I part of", which is what the UI's team filter and
+// the combined queue are built from.
+func handleListTeams(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		caller, _ := userFromContext(r.Context())
+		rows, err := db.QueryContext(r.Context(), `
+			SELECT t.id, t.name, t.created_at, m.role
+			FROM   teams t
+			JOIN   team_members m ON m.team_id = t.id
+			WHERE  m.user_id = $1
+			ORDER  BY t.name`, caller.ID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		defer rows.Close()
+
+		teams := []models.Team{}
+		for rows.Next() {
+			var t models.Team
+			var created int64
+			if err := rows.Scan(&t.ID, &t.Name, &created, &t.Role); err != nil {
+				respond(w, http.StatusInternalServerError, errResp("internal error"))
+				return
+			}
+			t.CreatedAt = time.Unix(created, 0).UTC()
+			teams = append(teams, t)
+		}
+		if err := rows.Err(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		respond(w, http.StatusOK, teams)
+	}
+}
+
+// handleCreateTeam creates a team and makes its creator the first owner. A team
+// with no owner would need an administrator to repair before anybody could use
+// it, so the two happen in one transaction.
+func handleCreateTeam(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req struct {
+			Name string `json:"name"`
+		}
+		if err := decodeJSON(r, &req); err != nil {
+			respond(w, http.StatusBadRequest, errResp("invalid request body"))
+			return
+		}
+		req.Name = strings.TrimSpace(req.Name)
+		if req.Name == "" {
+			respond(w, http.StatusBadRequest, errResp("name is required"))
+			return
+		}
+
+		caller, _ := userFromContext(r.Context())
+
+		tx, err := db.BeginTx(r.Context(), nil)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		defer tx.Rollback() //nolint:errcheck
+
+		var team models.Team
+		var created int64
+		if err := tx.QueryRowContext(r.Context(),
+			"INSERT INTO teams (name) VALUES ($1) RETURNING id, name, created_at",
+			req.Name).Scan(&team.ID, &team.Name, &created); err != nil {
+			if isUniqueViolation(err) {
+				respond(w, http.StatusConflict, errResp("a team with that name already exists"))
+				return
+			}
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if _, err := tx.ExecContext(r.Context(),
+			"INSERT INTO team_members (team_id, user_id, role) VALUES ($1, $2, $3)",
+			team.ID, caller.ID, models.RoleOwner); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if err := tx.Commit(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+
+		team.CreatedAt = time.Unix(created, 0).UTC()
+		team.Role = models.RoleOwner
+		respond(w, http.StatusCreated, team)
+	}
+}
+
+// handleDeleteTeam removes a team and, by cascade, its incidents, alerts,
+// schedule and integrations.
+//
+// Refused while the team still has open incidents: deleting a team is tidying
+// up, and tidying up should never be how an unacknowledged page disappears.
+// Resolve or archive them first, deliberately.
+func handleDeleteTeam(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
+
+		var open int
+		if err := db.QueryRowContext(r.Context(),
+			"SELECT COUNT(*) FROM incidents WHERE team_id = $1 AND resolved_at IS NULL", teamID).
+			Scan(&open); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if open > 0 {
+			respond(w, http.StatusConflict, errResp("team still has open incidents"))
+			return
+		}
+
+		res, err := db.ExecContext(r.Context(), "DELETE FROM teams WHERE id = $1", teamID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if n, _ := res.RowsAffected(); n == 0 {
+			respond(w, http.StatusNotFound, errResp("not found"))
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}
+}
+
+// handleListTeamMembers names everybody in a team. Visible to any member: you
+// can see who else is on the rota you are on.
+func handleListTeamMembers(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamMember(w, r, teamID) {
+			return
+		}
+
+		rows, err := db.QueryContext(r.Context(), `
+			SELECT m.team_id, m.user_id, u.username, m.role, m.joined_at
+			FROM   team_members m
+			JOIN   users u ON u.id = m.user_id
+			WHERE  m.team_id = $1
+			ORDER  BY u.username`, teamID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		defer rows.Close()
+
+		members := []models.TeamMember{}
+		for rows.Next() {
+			var m models.TeamMember
+			var joined int64
+			if err := rows.Scan(&m.TeamID, &m.UserID, &m.Username, &m.Role, &joined); err != nil {
+				respond(w, http.StatusInternalServerError, errResp("internal error"))
+				return
+			}
+			m.JoinedAt = time.Unix(joined, 0).UTC()
+			members = append(members, m)
+		}
+		if err := rows.Err(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		respond(w, http.StatusOK, members)
+	}
+}
+
+// handleAddTeamMember adds a user to a team, or changes the role of somebody
+// already in it.
+func handleAddTeamMember(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
+
+		var req struct {
+			UserID int64  `json:"user_id"`
+			Role   string `json:"role"`
+		}
+		if err := decodeJSON(r, &req); err != nil || req.UserID == 0 {
+			respond(w, http.StatusBadRequest, errResp("user_id is required"))
+			return
+		}
+		if req.Role == "" {
+			req.Role = models.RoleMember
+		}
+		if req.Role != models.RoleOwner && req.Role != models.RoleMember {
+			respond(w, http.StatusBadRequest, errResp("role must be owner or member"))
+			return
+		}
+
+		_, err := db.ExecContext(r.Context(), `
+			INSERT INTO team_members (team_id, user_id, role)
+			VALUES ($1, $2, $3)
+			ON CONFLICT (team_id, user_id) DO UPDATE SET role = excluded.role`,
+			teamID, req.UserID, req.Role)
+		if err != nil {
+			// The only foreign key that can fail here is the user: the team was
+			// resolved from the caller's own membership.
+			respond(w, http.StatusNotFound, errResp("user not found"))
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}
+}
+
+// handleRemoveTeamMember takes a user out of a team.
+//
+// A team must keep an owner, for the same reason the install must keep an
+// administrator: otherwise nobody can configure it, and repairing that needs
+// somebody with more access than the team has.
+func handleRemoveTeamMember(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
+		userID, err := strconv.ParseInt(chi.URLParam(r, "userID"), 10, 64)
+		if err != nil {
+			respond(w, http.StatusBadRequest, errResp("invalid user id"))
+			return
+		}
+
+		last, err := isLastTeamOwner(r.Context(), db, teamID, userID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if last {
+			respond(w, http.StatusConflict, errResp("cannot remove the last owner of a team"))
+			return
+		}
+
+		res, err := db.ExecContext(r.Context(),
+			"DELETE FROM team_members WHERE team_id = $1 AND user_id = $2", teamID, userID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if n, _ := res.RowsAffected(); n == 0 {
+			respond(w, http.StatusNotFound, errResp("not a member of this team"))
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}
+}
+
+func isLastTeamOwner(ctx context.Context, db *sql.DB, teamID, userID int64) (bool, error) {
+	var last bool
+	err := db.QueryRowContext(ctx, `
+		SELECT EXISTS (SELECT 1 FROM team_members
+		                WHERE team_id = $1 AND user_id = $2 AND role = 'owner')
+		   AND NOT EXISTS (SELECT 1 FROM team_members
+		                    WHERE team_id = $1 AND user_id <> $2 AND role = 'owner')`,
+		teamID, userID).Scan(&last)
+	return last, err
+}
+
+// ---------------------------------------------------------------------------
+// Integrations
+// ---------------------------------------------------------------------------
+
+// handleListIntegrations lists a team's integrations. Never the keys: those
+// exist in plaintext only in the response that created them.
+func handleListIntegrations(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamMember(w, r, teamID) {
+			return
+		}
+
+		rows, err := db.QueryContext(r.Context(), `
+			SELECT id, team_id, kind, name, created_at, last_used_at
+			FROM   integrations
+			WHERE  team_id = $1
+			ORDER  BY id`, teamID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		defer rows.Close()
+
+		integrations := []models.Integration{}
+		for rows.Next() {
+			var i models.Integration
+			var created int64
+			var lastUsed *int64
+			if err := rows.Scan(&i.ID, &i.TeamID, &i.Kind, &i.Name, &created, &lastUsed); err != nil {
+				respond(w, http.StatusInternalServerError, errResp("internal error"))
+				return
+			}
+			i.CreatedAt = time.Unix(created, 0).UTC()
+			i.LastUsedAt = unixPtr(lastUsed)
+			integrations = append(integrations, i)
+		}
+		if err := rows.Err(); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		respond(w, http.StatusOK, integrations)
+	}
+}
+
+// handleCreateIntegration mints an integration key. The key is returned once,
+// in this response, and only its hash is kept — the same handling as an API key
+// or an acknowledgement token.
+func handleCreateIntegration(db *sql.DB, publicURL string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
+
+		var req struct {
+			Name string `json:"name"`
+			Kind string `json:"kind"`
+		}
+		if err := decodeJSON(r, &req); err != nil {
+			respond(w, http.StatusBadRequest, errResp("invalid request body"))
+			return
+		}
+		req.Name = strings.TrimSpace(req.Name)
+		if req.Name == "" {
+			respond(w, http.StatusBadRequest, errResp("name is required"))
+			return
+		}
+		if req.Kind == "" {
+			req.Kind = models.IntegrationAlertmanager
+		}
+		if req.Kind != models.IntegrationAlertmanager {
+			respond(w, http.StatusBadRequest, errResp("unsupported integration kind"))
+			return
+		}
+
+		raw, hash, err := randomToken()
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+
+		var i models.Integration
+		var created int64
+		if err := db.QueryRowContext(r.Context(), `
+			INSERT INTO integrations (team_id, kind, name, key_hash)
+			VALUES ($1, $2, $3, $4)
+			RETURNING id, team_id, kind, name, created_at`,
+			teamID, req.Kind, req.Name, hash).
+			Scan(&i.ID, &i.TeamID, &i.Kind, &i.Name, &created); err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		i.CreatedAt = time.Unix(created, 0).UTC()
+		i.Key = raw
+		i.URL = strings.TrimSuffix(publicURL, "/") + integrationPath(raw, i.Kind)
+		respond(w, http.StatusCreated, i)
+	}
+}
+
+func handleDeleteIntegration(db *sql.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		teamID, ok := teamParam(w, r)
+		if !ok {
+			return
+		}
+		if !requireTeamOwner(w, r, teamID) {
+			return
+		}
+		id, err := strconv.ParseInt(chi.URLParam(r, "integrationID"), 10, 64)
+		if err != nil {
+			respond(w, http.StatusBadRequest, errResp("invalid integration id"))
+			return
+		}
+
+		res, err := db.ExecContext(r.Context(),
+			"DELETE FROM integrations WHERE id = $1 AND team_id = $2", id, teamID)
+		if err != nil {
+			respond(w, http.StatusInternalServerError, errResp("internal error"))
+			return
+		}
+		if n, _ := res.RowsAffected(); n == 0 {
+			respond(w, http.StatusNotFound, errResp("not found"))
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}
+}
+
+// integrationPath is where a sender of this kind posts. Built in one place so
+// the URL handed out at creation and the route the router registers cannot
+// drift apart.
+func integrationPath(key, kind string) string {
+	return "/api/integrations/" + key + "/" + kind
+}
+
+// teamIDForKey resolves an integration key to its team, and stamps the key's
+// last use. An unknown key is not an error worth distinguishing: the caller is
+// told nothing beyond "no".
+func teamIDForKey(ctx context.Context, db *sql.DB, key string) (int64, error) {
+	var teamID int64
+	err := db.QueryRowContext(ctx,
+		"SELECT team_id FROM integrations WHERE key_hash = $1", hashToken(key)).Scan(&teamID)
+	if errors.Is(err, sql.ErrNoRows) {
+		return 0, errUnknownIntegration
+	}
+	if err != nil {
+		return 0, err
+	}
+	// Best effort, like an API key's: a failed stamp must not reject an alert.
+	db.ExecContext(ctx, //nolint:errcheck
+		"UPDATE integrations SET last_used_at = $1 WHERE key_hash = $2",
+		time.Now().Unix(), hashToken(key))
+	return teamID, nil
+}
+
+var errUnknownIntegration = errors.New("unknown integration key")
+
+// teamParam reads {teamID} from the path.
+func teamParam(w http.ResponseWriter, r *http.Request) (int64, bool) {
+	id, err := strconv.ParseInt(chi.URLParam(r, "teamID"), 10, 64)
+	if err != nil {
+		respond(w, http.StatusBadRequest, errResp("invalid team id"))
+		return 0, false
+	}
+	return id, true
+}
+
+// defaultTeamID is the team the deprecated unauthenticated webhook routes to:
+// the oldest one, which on an upgraded install is the "Default" team every
+// pre-teams row was moved into.
+func defaultTeamID(ctx context.Context, db *sql.DB) (int64, error) {
+	var id int64
+	err := db.QueryRowContext(ctx, "SELECT id FROM teams ORDER BY id LIMIT 1").Scan(&id)
+	return id, err
+}
diff --git a/internal/api/teams_test.go b/internal/api/teams_test.go
new file mode 100644
index 0000000..1a49d37
--- /dev/null
+++ b/internal/api/teams_test.go
@@ -0,0 +1,350 @@
+package api_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"testing"
+)
+
+// The whole point of #4: two teams sharing one server must not see each other's
+// work. These tests build two of them and check the boundary from both sides.
+
+type teamFixture struct {
+	id   int64
+	key  string // integration key: how alerts get in
+	call func(method, path string, body any) *http.Response
+}
+
+// newTeam creates a team with its own member, integration key and API key. The
+// admin does the creating, as an install's first user would.
+func newTeam(t *testing.T, s *ts, name string) teamFixture {
+	t.Helper()
+
+	var team struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/teams", map[string]string{"name": name}), &team)
+
+	var integration struct {
+		Key string `json:"key"`
+		URL string `json:"url"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/teams/"+id64(team.ID)+"/integrations",
+		map[string]string{"name": name + " alertmanager"}), &integration)
+	if integration.Key == "" {
+		t.Fatalf("%s: integration key was not returned", name)
+	}
+
+	// A member of this team and no other.
+	var user struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/users",
+		map[string]string{"username": name + "-user", "email": name + "@test.com"}), &user)
+
+	resp := s.req(t, http.MethodPost, "/api/teams/"+id64(team.ID)+"/members",
+		map[string]any{"user_id": user.ID, "role": "owner"})
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("%s: add member: %d", name, resp.StatusCode)
+	}
+
+	var key struct {
+		Key string `json:"key"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/users/"+id64(user.ID)+"/api-keys",
+		map[string]string{"name": "test"}), &key)
+
+	return teamFixture{
+		id:  team.ID,
+		key: integration.Key,
+		call: func(method, path string, body any) *http.Response {
+			t.Helper()
+			var r io.Reader
+			if body != nil {
+				data, _ := json.Marshal(body)
+				r = bytes.NewReader(data)
+			}
+			req, _ := http.NewRequest(method, s.URL+path, r)
+			req.Header.Set("Authorization", "Bearer "+key.Key)
+			if body != nil {
+				req.Header.Set("Content-Type", "application/json")
+			}
+			resp, err := http.DefaultClient.Do(req)
+			if err != nil {
+				t.Fatalf("%s %s: %v", method, path, err)
+			}
+			return resp
+		},
+	}
+}
+
+// postToIntegration sends one firing alert on a team's integration key, the way
+// a real Alertmanager receiver would.
+func postToIntegration(t *testing.T, s *ts, key, fingerprint, name string) {
+	t.Helper()
+	payload := map[string]any{
+		"version":     "4",
+		"status":      "firing",
+		"groupKey":    "{}:{alertname=\"" + name + "\"}",
+		"groupLabels": map[string]string{"alertname": name},
+		"alerts": []map[string]any{
+			amAlert(fingerprint, name, "firing", "2026-09-20T10:00:00Z", zeroTime, nil),
+		},
+	}
+	data, _ := json.Marshal(payload)
+	resp, err := http.Post(s.URL+"/api/integrations/"+key+"/alertmanager",
+		"application/json", bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("post alert: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("post alert: %d", resp.StatusCode)
+	}
+}
+
+func list(t *testing.T, resp *http.Response) []map[string]any {
+	t.Helper()
+	var out []map[string]any
+	decode(t, resp, &out)
+	return out
+}
+
+// An alert posted on one team's key opens an incident in that team and nowhere
+// else, and neither team can read the other's queue.
+func TestTeams_IncidentsAreScopedToTheReceivingTeam(t *testing.T) {
+	s := newTS(t)
+	red := newTeam(t, s, "red")
+	blue := newTeam(t, s, "blue")
+
+	postToIntegration(t, s, red.key, "fp-red", "RedDiskFull")
+	postToIntegration(t, s, blue.key, "fp-blue", "BlueDiskFull")
+
+	redIncidents := list(t, red.call(http.MethodGet, "/api/incidents", nil))
+	if len(redIncidents) != 1 {
+		t.Fatalf("red should see exactly its own incident, saw %d", len(redIncidents))
+	}
+	if title := redIncidents[0]["title"]; title != "RedDiskFull" {
+		t.Errorf("red saw %v", title)
+	}
+	if teamID := int64(redIncidents[0]["team_id"].(float64)); teamID != red.id {
+		t.Errorf("red's incident belongs to team %d, want %d", teamID, red.id)
+	}
+
+	blueIncidents := list(t, blue.call(http.MethodGet, "/api/incidents", nil))
+	if len(blueIncidents) != 1 || blueIncidents[0]["title"] != "BlueDiskFull" {
+		t.Fatalf("blue should see exactly its own incident, saw %v", blueIncidents)
+	}
+
+	// Reading the other team's incident by id is not found rather than
+	// forbidden: its existence is the other team's business.
+	otherID := int64(blueIncidents[0]["id"].(float64))
+	for _, path := range []string{
+		"/api/incidents/" + id64(otherID),
+		"/api/incidents/" + id64(otherID) + "/alerts",
+		"/api/incidents/" + id64(otherID) + "/timeline",
+	} {
+		resp := red.call(http.MethodGet, path, nil)
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusNotFound {
+			t.Errorf("red reading %s: expected 404, got %d", path, resp.StatusCode)
+		}
+	}
+
+	// And cannot act on it either.
+	for _, path := range []string{"/acknowledge", "/resolve", "/archive"} {
+		resp := red.call(http.MethodPost, "/api/incidents/"+id64(otherID)+path, nil)
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusNotFound {
+			t.Errorf("red posting %s: expected 404, got %d", path, resp.StatusCode)
+		}
+	}
+}
+
+// Alerts, the raw signal record, are scoped the same way.
+func TestTeams_AlertsAndStatsAreScoped(t *testing.T) {
+	s := newTS(t)
+	red := newTeam(t, s, "red")
+	blue := newTeam(t, s, "blue")
+
+	postToIntegration(t, s, red.key, "fp-red", "RedDiskFull")
+	postToIntegration(t, s, blue.key, "fp-blue-1", "BlueDiskFull")
+	postToIntegration(t, s, blue.key, "fp-blue-2", "BlueMemory")
+
+	if alerts := list(t, red.call(http.MethodGet, "/api/alerts", nil)); len(alerts) != 1 {
+		t.Errorf("red should see 1 alert, saw %d", len(alerts))
+	}
+	if alerts := list(t, blue.call(http.MethodGet, "/api/alerts", nil)); len(alerts) != 2 {
+		t.Errorf("blue should see 2 alerts, saw %d", len(alerts))
+	}
+
+	// Statistics count your own work only — otherwise a team's volume, and the
+	// names of its alerts, leak through the totals.
+	var stats map[string]any
+	decode(t, red.call(http.MethodGet, "/api/stats/alerts", nil), &stats)
+	if total := stats["total"].(float64); total != 1 {
+		t.Errorf("red's alert stats counted %v alerts, want 1", total)
+	}
+
+	top := list(t, red.call(http.MethodGet, "/api/stats/alerts/top", nil))
+	for _, row := range top {
+		if name := row["name"].(string); name != "RedDiskFull" {
+			t.Errorf("red's top alerts named %q, which is not theirs", name)
+		}
+	}
+}
+
+// The same fingerprint, the same groupKey and the same date are all legitimate
+// in two teams at once: two clusters running the same rules, two rotas.
+func TestTeams_SameFingerprintInTwoTeams(t *testing.T) {
+	s := newTS(t)
+	red := newTeam(t, s, "red")
+	blue := newTeam(t, s, "blue")
+
+	postToIntegration(t, s, red.key, "fp-shared", "DiskFull")
+	postToIntegration(t, s, blue.key, "fp-shared", "DiskFull")
+
+	for _, team := range []struct {
+		name string
+		f    teamFixture
+	}{{"red", red}, {"blue", blue}} {
+		incidents := list(t, team.f.call(http.MethodGet, "/api/incidents", nil))
+		if len(incidents) != 1 {
+			t.Errorf("%s: expected its own incident for the shared fingerprint, saw %d",
+				team.name, len(incidents))
+		}
+	}
+
+	// And both rotas can name somebody for the same day.
+	for _, team := range []struct {
+		name string
+		f    teamFixture
+	}{{"red", red}, {"blue", blue}} {
+		var members []map[string]any
+		decode(t, team.f.call(http.MethodGet, "/api/teams/"+id64(team.f.id)+"/members", nil), &members)
+		userID := int64(members[0]["user_id"].(float64))
+
+		resp := team.f.call(http.MethodPost, "/api/teams/"+id64(team.f.id)+"/schedule",
+			map[string]any{"user_id": userID, "dates": []string{"2026-10-01"}})
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusCreated {
+			t.Errorf("%s: taking 2026-10-01 returned %d", team.name, resp.StatusCode)
+		}
+	}
+}
+
+// An unknown key delivers nothing, and says so rather than accepting silently.
+func TestTeams_UnknownIntegrationKeyIsRejected(t *testing.T) {
+	s := newTS(t)
+	team := newTeam(t, s, "red")
+
+	resp, err := http.Post(s.URL+"/api/integrations/not-a-real-key/alertmanager",
+		"application/json", bytes.NewReader([]byte(`{"version":"4","status":"firing","alerts":[]}`)))
+	if err != nil {
+		t.Fatalf("post: %v", err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusUnauthorized {
+		t.Errorf("expected 401 for an unknown key, got %d", resp.StatusCode)
+	}
+
+	if incidents := list(t, team.call(http.MethodGet, "/api/incidents", nil)); len(incidents) != 0 {
+		t.Errorf("a rejected payload opened %d incident(s)", len(incidents))
+	}
+}
+
+// Team configuration is an owner's job; working incidents is a member's.
+func TestTeams_MemberCannotConfigureTheTeam(t *testing.T) {
+	s := newTS(t)
+	team := newTeam(t, s, "red")
+
+	// A plain member of the same team.
+	var user struct {
+		ID int64 `json:"id"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/users",
+		map[string]string{"username": "plain", "email": "plain@test.com"}), &user)
+	resp := s.req(t, http.MethodPost, "/api/teams/"+id64(team.id)+"/members",
+		map[string]any{"user_id": user.ID, "role": "member"})
+	resp.Body.Close()
+	var key struct {
+		Key string `json:"key"`
+	}
+	decode(t, s.req(t, http.MethodPost, "/api/users/"+id64(user.ID)+"/api-keys",
+		map[string]string{"name": "test"}), &key)
+
+	call := func(method, path string, body any) *http.Response {
+		t.Helper()
+		var r io.Reader
+		if body != nil {
+			data, _ := json.Marshal(body)
+			r = bytes.NewReader(data)
+		}
+		req, _ := http.NewRequest(method, s.URL+path, r)
+		req.Header.Set("Authorization", "Bearer "+key.Key)
+		if body != nil {
+			req.Header.Set("Content-Type", "application/json")
+		}
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("%s %s: %v", method, path, err)
+		}
+		return resp
+	}
+
+	base := "/api/teams/" + id64(team.id)
+	for _, c := range []struct {
+		name   string
+		method string
+		path   string
+		body   any
+	}{
+		{"mint an integration key", http.MethodPost, base + "/integrations",
+			map[string]string{"name": "mine"}},
+		{"take a shift", http.MethodPost, base + "/schedule",
+			map[string]any{"user_id": user.ID, "dates": []string{"2026-11-01"}}},
+		{"add a member", http.MethodPost, base + "/members",
+			map[string]any{"user_id": 1}},
+		{"delete the team", http.MethodDelete, base, nil},
+	} {
+		resp := call(c.method, c.path, c.body)
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusForbidden {
+			t.Errorf("%s: expected 403, got %d", c.name, resp.StatusCode)
+		}
+	}
+
+	// But they can read what the team is doing.
+	for _, path := range []string{base + "/members", base + "/integrations", base + "/schedule"} {
+		resp := call(http.MethodGet, path, nil)
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			t.Errorf("reading %s: expected 200, got %d", path, resp.StatusCode)
+		}
+	}
+}
+
+// A team is not somewhere an outsider can look, whatever they know about it.
+func TestTeams_OutsiderSeesNothing(t *testing.T) {
+	s := newTS(t)
+	red := newTeam(t, s, "red")
+	blue := newTeam(t, s, "blue")
+
+	base := "/api/teams/" + id64(red.id)
+	for _, path := range []string{base + "/members", base + "/integrations", base + "/schedule"} {
+		resp := blue.call(http.MethodGet, path, nil)
+		resp.Body.Close()
+		if resp.StatusCode != http.StatusNotFound {
+			t.Errorf("blue reading %s: expected 404, got %d", path, resp.StatusCode)
+		}
+	}
+
+	// /api/teams lists your own, never the install's.
+	teams := list(t, blue.call(http.MethodGet, "/api/teams", nil))
+	if len(teams) != 1 || teams[0]["name"] != "blue" {
+		t.Errorf("blue's team list: %v", teams)
+	}
+}
diff --git a/internal/api/testdb_test.go b/internal/api/testdb_test.go
index d8f4c9a..647add3 100644
--- a/internal/api/testdb_test.go
+++ b/internal/api/testdb_test.go
@@ -30,6 +30,10 @@ import (
 // tests nothing is worse than one that does not run.
 const testDSNEnv = "TERDUT_TEST_DSN"
 
+// defaultTeam is the team migration 003 creates and the bootstrap user owns, as
+// a path segment. Every test that does not say otherwise works inside it.
+const defaultTeam = "1"
+
 var schemaSeq int
 
 // newTestDB returns a migrated database private to this test, and drops it
diff --git a/internal/api/users.go b/internal/api/users.go
index f1955f9..ab28337 100644
--- a/internal/api/users.go
+++ b/internal/api/users.go
@@ -77,6 +77,16 @@ func handleBootstrap(db *sql.DB) http.HandlerFunc {
 			return
 		}
 
+		// The default team exists from migration 003, on a fresh install too.
+		// Without a membership the first user signs in to a working server with
+		// no queue, no schedule and nowhere for an integration to hang off.
+		if teamID, err := defaultTeamID(r.Context(), db); err == nil {
+			db.ExecContext(r.Context(), //nolint:errcheck
+				"INSERT INTO team_members (team_id, user_id, role) VALUES ($1, $2, $3) "+
+					"ON CONFLICT (team_id, user_id) DO NOTHING",
+				teamID, userID, models.RoleOwner)
+		}
+
 		user, _ := fetchUser(r.Context(), db, userID)
 		key := models.APIKey{ID: keyID, UserID: userID, Name: "bootstrap", Key: raw, CreatedAt: user.CreatedAt}
 		respond(w, http.StatusCreated, map[string]any{"user": user, "api_key": key})
diff --git a/internal/db/migrations/003_teams.sql b/internal/db/migrations/003_teams.sql
new file mode 100644
index 0000000..ea1358d
--- /dev/null
+++ b/internal/db/migrations/003_teams.sql
@@ -0,0 +1,103 @@
+-- Teams: the unit of tenancy. Everything a person works on now belongs to one.
+--
+-- Until this migration the install was one shared space — every user saw every
+-- alert and every incident, and the Alertmanager webhook was unauthenticated, so
+-- anything that could reach the port could open an incident for everybody.
+--
+-- The shape, in one paragraph: a team owns its incidents, alerts, schedule and
+-- integrations. A user belongs to as many teams as they like, with a role in
+-- each: an `owner` configures the team, a `member` works its incidents. An
+-- integration key is what an alert arrives on, and the key is what says which
+-- team the alert belongs to.
+--
+-- EVERYTHING EXISTING MOVES INTO ONE DEFAULT TEAM, and every existing user
+-- becomes an owner of it. That keeps an upgrade a no-op for the people using it:
+-- the same queue, the same schedule, the same incidents, with a name on them.
+
+CREATE TABLE teams (
+    id         BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+    name       TEXT   NOT NULL UNIQUE,
+    created_at BIGINT NOT NULL DEFAULT FLOOR(EXTRACT(EPOCH FROM now()))::bigint
+);
+
+-- role is free text with a CHECK rather than an enum, so adding a third role
+-- later is a migration and not a type rewrite.
+CREATE TABLE team_members (
+    team_id   BIGINT NOT NULL REFERENCES teams(id) ON DELETE CASCADE,
+    user_id   BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    role      TEXT   NOT NULL CHECK (role IN ('owner', 'member')),
+    joined_at BIGINT NOT NULL DEFAULT FLOOR(EXTRACT(EPOCH FROM now()))::bigint,
+    PRIMARY KEY (team_id, user_id)
+);
+
+CREATE INDEX team_members_user_idx ON team_members(user_id);
+
+-- How alerts get in, and the only thing that says which team they belong to.
+-- The key is stored as a SHA-256 hash, like api_keys and the ack tokens: a
+-- leaked database gives nobody the ability to post alerts.
+CREATE TABLE integrations (
+    id           BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+    team_id      BIGINT NOT NULL REFERENCES teams(id) ON DELETE CASCADE,
+    kind         TEXT   NOT NULL CHECK (kind IN ('alertmanager')),
+    name         TEXT   NOT NULL,
+    key_hash     TEXT   NOT NULL UNIQUE,
+    created_at   BIGINT NOT NULL DEFAULT FLOOR(EXTRACT(EPOCH FROM now()))::bigint,
+    last_used_at BIGINT
+);
+
+CREATE INDEX integrations_team_idx ON integrations(team_id);
+
+-- ---------------------------------------------------------------------------
+-- The default team, and everything that already exists moving into it.
+--
+-- Created unconditionally, even on an empty install, so there is always a team
+-- for the bootstrap user to land in and for the first integration to hang off.
+-- ---------------------------------------------------------------------------
+
+INSERT INTO teams (name) VALUES ('Default');
+
+INSERT INTO team_members (team_id, user_id, role)
+SELECT (SELECT id FROM teams WHERE name = 'Default'), id, 'owner' FROM users;
+
+-- ---------------------------------------------------------------------------
+-- team_id on everything a team owns.
+--
+-- Added nullable, backfilled, then made NOT NULL: adding a NOT NULL column with
+-- no default to a table with rows is rejected, and a DEFAULT pointing at the
+-- default team would quietly keep working after the default team is gone.
+-- ---------------------------------------------------------------------------
+
+ALTER TABLE alerts            ADD COLUMN team_id BIGINT REFERENCES teams(id) ON DELETE CASCADE;
+ALTER TABLE incidents         ADD COLUMN team_id BIGINT REFERENCES teams(id) ON DELETE CASCADE;
+ALTER TABLE schedule_entries  ADD COLUMN team_id BIGINT REFERENCES teams(id) ON DELETE CASCADE;
+
+UPDATE alerts           SET team_id = (SELECT id FROM teams WHERE name = 'Default');
+UPDATE incidents        SET team_id = (SELECT id FROM teams WHERE name = 'Default');
+UPDATE schedule_entries SET team_id = (SELECT id FROM teams WHERE name = 'Default');
+
+ALTER TABLE alerts           ALTER COLUMN team_id SET NOT NULL;
+ALTER TABLE incidents        ALTER COLUMN team_id SET NOT NULL;
+ALTER TABLE schedule_entries ALTER COLUMN team_id SET NOT NULL;
+
+-- ---------------------------------------------------------------------------
+-- The uniqueness rules were all written for one tenant, and every one of them
+-- is wrong now: two teams monitoring two clusters legitimately see the same
+-- fingerprint, the same groupKey, and want somebody on call on the same day.
+-- ---------------------------------------------------------------------------
+
+ALTER TABLE alerts DROP CONSTRAINT alerts_fingerprint_key;
+CREATE UNIQUE INDEX alerts_team_fingerprint_idx ON alerts(team_id, fingerprint);
+
+DROP INDEX incidents_open_group_key_idx;
+-- Still load-bearing, now per team: at most one OPEN incident per group_key
+-- within a team. This is what makes "resolved incident + a new alert occurrence
+-- = a new incident" work, and what the webhook's find-or-open lookup relies on.
+CREATE UNIQUE INDEX incidents_open_group_key_idx
+    ON incidents(team_id, group_key) WHERE resolved_at IS NULL;
+
+ALTER TABLE schedule_entries DROP CONSTRAINT schedule_entries_date_key;
+CREATE UNIQUE INDEX schedule_entries_team_date_idx ON schedule_entries(team_id, date);
+
+-- The list views all filter by team first.
+CREATE INDEX alerts_team_received_idx    ON alerts(team_id, received_at DESC);
+CREATE INDEX incidents_team_triggered_idx ON incidents(team_id, triggered_at DESC);
diff --git a/internal/models/alert.go b/internal/models/alert.go
index 13bf2a2..01047e8 100644
--- a/internal/models/alert.go
+++ b/internal/models/alert.go
@@ -7,7 +7,13 @@ import "time"
 // to it — acknowledgement, assignment, notes and closure all live on the
 // Incident an alert belongs to.
 type Alert struct {
-	ID           int64             `json:"id"`
+	ID int64 `json:"id"`
+
+	// TeamID is the team whose integration received this alert, and TeamName
+	// rides along so a combined list can label a row without a second request.
+	TeamID   int64  `json:"team_id"`
+	TeamName string `json:"team_name,omitempty"`
+
 	Fingerprint  string            `json:"fingerprint"`
 	Name         string            `json:"name"`
 	Status       string            `json:"status"` // "firing" or "resolved"
diff --git a/internal/models/incident.go b/internal/models/incident.go
index d771600..91dc89e 100644
--- a/internal/models/incident.go
+++ b/internal/models/incident.go
@@ -11,6 +11,12 @@ import "time"
 // the webhook and the sweeper may flip to "resolved" once every member alert has
 // stopped firing.
 type Incident struct {
+	// TeamID is the team that owns this incident, fixed when it opens: an
+	// incident never moves between teams. TeamName rides along so the combined
+	// queue can badge each row without a second request.
+	TeamID   int64  `json:"team_id"`
+	TeamName string `json:"team_name,omitempty"`
+
 	ID          int64             `json:"id"`
 	GroupKey    string            `json:"group_key"`
 	Title       string            `json:"title"`
diff --git a/internal/models/schedule.go b/internal/models/schedule.go
index e85d9bd..aad427c 100644
--- a/internal/models/schedule.go
+++ b/internal/models/schedule.go
@@ -3,7 +3,14 @@ package models
 import "time"
 
 type ScheduleEntry struct {
-	ID        int64     `json:"id"`
+	ID int64 `json:"id"`
+
+	// TeamID is whose rota this shift belongs to; TeamName rides along so the
+	// combined "who is on call" view can label each entry without a second
+	// request.
+	TeamID   int64  `json:"team_id"`
+	TeamName string `json:"team_name,omitempty"`
+
 	UserID    int64     `json:"user_id"`
 	Username  string    `json:"username"`
 	Date      string    `json:"date"` // YYYY-MM-DD
diff --git a/internal/models/team.go b/internal/models/team.go
new file mode 100644
index 0000000..8695b8d
--- /dev/null
+++ b/internal/models/team.go
@@ -0,0 +1,54 @@
+package models
+
+import "time"
+
+// Team is the unit of tenancy: it owns its incidents, alerts, schedule and
+// integrations, and a user sees exactly the teams they belong to.
+type Team struct {
+	ID        int64     `json:"id"`
+	Name      string    `json:"name"`
+	CreatedAt time.Time `json:"created_at"`
+
+	// Role is the caller's own role in this team, populated when a team is
+	// listed for a particular person. Empty when nobody in particular is
+	// asking, as in the admin listing.
+	Role string `json:"role,omitempty"`
+}
+
+// Team roles. An owner configures the team — its schedule, its integrations and
+// who is in it. A member works its incidents.
+const (
+	RoleOwner  = "owner"
+	RoleMember = "member"
+)
+
+// TeamMember is one person's membership of one team.
+type TeamMember struct {
+	TeamID   int64     `json:"team_id"`
+	UserID   int64     `json:"user_id"`
+	Username string    `json:"username"`
+	Role     string    `json:"role"`
+	JoinedAt time.Time `json:"joined_at"`
+}
+
+// Integration is how alerts get in, and the only thing that says which team an
+// arriving alert belongs to.
+type Integration struct {
+	ID         int64      `json:"id"`
+	TeamID     int64      `json:"team_id"`
+	Kind       string     `json:"kind"`
+	Name       string     `json:"name"`
+	CreatedAt  time.Time  `json:"created_at"`
+	LastUsedAt *time.Time `json:"last_used_at,omitempty"`
+
+	// Key is the raw integration key, shown once when the integration is
+	// created and never stored. URL is the address to point the sender at,
+	// likewise only complete at creation time.
+	Key string `json:"key,omitempty"`
+	URL string `json:"url,omitempty"`
+}
+
+// Integration kinds.
+const (
+	IntegrationAlertmanager = "alertmanager"
+)
diff --git a/internal/web/static/js/api.js b/internal/web/static/js/api.js
index 33e6096..150e3f1 100644
--- a/internal/web/static/js/api.js
+++ b/internal/web/static/js/api.js
@@ -87,12 +87,11 @@ export const deleteNote = (id, eventID) => call('DELETE', `/incidents/${id}/note
 export const alerts = (query, opts) => call('GET', '/alerts', { query, ...opts });
 
 // schedule
-export const schedule = (from, to) => call('GET', '/schedule', { query: { from, to } });
-export async function onCallNow() {
-  try {
-    return await call('GET', '/schedule/current');
-  } catch (err) {
-    if (err instanceof ApiError && err.status === 404) return null;
-    throw err;
-  }
-}
+export const teams = () => call('GET', '/teams');
+export const schedule = (teamID, from, to) =>
+  call('GET', `/teams/${teamID}/schedule`, { query: { from, to } });
+
+// One entry per team the viewer belongs to, for the teams that have somebody
+// scheduled today. An empty array means nobody anywhere, which is a real answer
+// rather than an error — unlike the pre-teams endpoint, which 404ed.
+export const onCallNow = () => call('GET', '/schedule/current');
diff --git a/internal/web/static/js/app.js b/internal/web/static/js/app.js
index 9aa28e2..5415278 100644
--- a/internal/web/static/js/app.js
+++ b/internal/web/static/js/app.js
@@ -3,7 +3,7 @@
 import * as api from './api.js';
 import * as ui from './ui.js';
 import * as poll from './poll.js';
-import { state, reset } from './state.js';
+import { state, reset, loadTeams } from './state.js';
 import * as queue from './queue.js';
 import * as incident from './incident.js';
 import * as oncall from './oncall.js';
@@ -141,6 +141,7 @@ async function boot() {
 
   try {
     state.me = await api.me();
+    await loadTeams();
     showApp();
   } catch (err) {
     if (err.status === 401) showLogin();
diff --git a/internal/web/static/js/oncall.js b/internal/web/static/js/oncall.js
index dfd22a0..26394d1 100644
--- a/internal/web/static/js/oncall.js
+++ b/internal/web/static/js/oncall.js
@@ -1,10 +1,14 @@
 // On-call: who is on duty now, the week around it, and your own next shifts.
 // Read-only for now; the TUI edits the schedule.
+//
+// One team's rota at a time — the viewer's first team, since a viewer in one
+// team has nothing to choose between. "On call now" is the exception and shows
+// every team the viewer is in, because somebody on two rotas wants both.
 
 import * as api from './api.js';
 import { h, clear, icon, spinner } from './ui.js';
 import { isoDate, mondayOf, addDays, isoWeek, initial } from './format.js';
-import { myID } from './state.js';
+import { myID, currentTeam } from './state.js';
 
 const view = () => document.getElementById('view-oncall');
 
@@ -24,10 +28,17 @@ export async function refresh() {
   const start = weekStart;
   const today = new Date();
   try {
+    const team = currentTeam();
+    if (!team) {
+      data = { now: [], week: [], upcoming: [] };
+      error = null;
+      render();
+      return;
+    }
     const [now, week, upcoming] = await Promise.all([
       api.onCallNow(),
-      api.schedule(isoDate(start), isoDate(addDays(start, 6))),
-      api.schedule(isoDate(today), isoDate(addDays(today, 60))),
+      api.schedule(team.id, isoDate(start), isoDate(addDays(start, 6))),
+      api.schedule(team.id, isoDate(today), isoDate(addDays(today, 60))),
     ]);
     if (start !== weekStart) return;
     data = { now, week, upcoming };
@@ -60,15 +71,32 @@ function you(userID) {
   return userID === myID() ? h('span', { class: 'you', text: 'you' }) : null;
 }
 
+// One card per team with somebody on call, and a single empty card when there
+// is nobody anywhere. The team's name is shown only when the viewer is in more
+// than one, so the common case reads exactly as it did before teams existed.
 function nowCard() {
-  const n = data.now;
-  return h('div', { class: 'card now-card' },
-    h('div', { class: `avatar ${n ? '' : 'none'}`, text: n ? initial(n.username) : '–' }),
-    h('div', {},
-      h('div', { class: 'now-label', text: 'On call now' }),
-      h('div', { class: 'now-name' }, n ? n.username : 'Nobody', n && you(n.user_id)),
-    ),
-  );
+  const entries = data.now || [];
+  const showTeam = entries.length > 1;
+  if (entries.length === 0) {
+    return h('div', { class: 'card now-card' },
+      h('div', { class: 'avatar none', text: '–' }),
+      h('div', {},
+        h('div', { class: 'now-label', text: 'On call now' }),
+        h('div', { class: 'now-name', text: 'Nobody' }),
+      ),
+    );
+  }
+  return h('div', {}, ...entries.map((n) =>
+    h('div', { class: 'card now-card' },
+      h('div', { class: 'avatar', text: initial(n.username) }),
+      h('div', {},
+        h('div', {
+          class: 'now-label',
+          text: showTeam ? `On call now · ${n.team_name}` : 'On call now',
+        }),
+        h('div', { class: 'now-name' }, n.username, you(n.user_id)),
+      ),
+    )));
 }
 
 function weekCard() {
diff --git a/internal/web/static/js/state.js b/internal/web/static/js/state.js
index 9a05cc1..f14addc 100644
--- a/internal/web/static/js/state.js
+++ b/internal/web/static/js/state.js
@@ -6,8 +6,15 @@ import * as api from './api.js';
 export const state = {
   me: null, // { user, has_password }
   open: [], // the default queue: open, not snoozed
+  teams: [], // the teams the viewer belongs to, each with their role
 };
 
+// The team whose schedule and settings the views act on. A viewer in one team —
+// which is everybody until somebody makes a second — never has to choose.
+export function currentTeam() {
+  return state.teams[0] || null;
+}
+
 export function myID() {
   return state.me ? state.me.user.id : null;
 }
@@ -24,8 +31,14 @@ export async function users() {
   return usersCache;
 }
 
+export async function loadTeams() {
+  state.teams = await api.teams();
+  return state.teams;
+}
+
 export function reset() {
   state.me = null;
   state.open = [];
+  state.teams = [];
   usersCache = null;
 }