From 3973e4058d7266b93f4ad39b2e8744cda89d5ab5 Mon Sep 17 00:00:00 2001
From: Kwaku Danso <72142185+cloud-dev101@users.noreply.github.com>
Date: Sun, 17 May 2026 22:14:50 +0100
Subject: [PATCH] =?UTF-8?q?feat(tier2):=20multi-host=20/=20collaborators?=
 =?UTF-8?q?=20=E2=80=94=20Block=20C?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Events can now have multiple users with distinct roles:
  owner   — manage collaborators, delete event, full access
  editor  — manage guests, tokens, CSV import, patch event
  viewer  — read-only access to everything

Schema (migration 0008)
- collaborator_role ENUM + event_collaborators + collaborator_invites
- Backfill: every existing events.host_id becomes an owner row
- EventRepo.Create seeds the owner row in the same transaction so
  no future event can exist without one

Authz
- New requireRole(eventID, userID, minRole) helper. Non-members 404;
  insufficient role 403. Replaces requireEventOwner across every
  shared-role handler (events.get/update, guests CRUD, tokens issue/
  rotate/bulk, csv preview/commit/template, activity, ws-ticket)
- events.delete + collaborator management stay owner-only
- GET /events lists every event the user has any role on
- /events/{id} response now embeds your_role for UI branching

Collaborator endpoints
- GET    /events/{id}/collaborators           (viewer+)
- POST   /events/{id}/collaborators           (owner)  — sends invite email
- PATCH  /events/{id}/collaborators/{user_id} (owner)  — role change
- DELETE /events/{id}/collaborators/{user_id} (owner)  — refuses last owner
- DELETE /events/{id}/collaborators/pending   (owner)  — cancel invite
- GET    /invites/{token}                     (public) — preview summary
- POST   /invites/{token}/accept              (authed) — atomic accept

Invitations
- SHA-256 hashed in DB; raw value only lives in the email link
- 7-day TTL, single-use, email-bound (caller's email must match)
- New SendCollaboratorInvite on auth.EmailSender + Resend/SMTP/SES
  senders + log stub; collaborator_invite.html/txt branded template

Frontend
- TeamCard.vue on the event detail page: lists collaborators with
  inline role-change + remove, pending-invites with cancel, invite
  modal (email + role). Owner-only actions hidden for editors/viewers
- /invites/[token] accept page: shows invite summary, prompts signup
  or sign-in with pre-filled email, refuses mismatched accounts

Tests (all 6 pass on the existing testcontainers harness)
- backfill: legacy host gets owner role
- role enforcement: viewer can read, editor can write guests but not
  delete/manage team, non-member 404s everywhere
- last-owner removal refused (400)
- shared events show up in collaborator's /events list
- invite flow: create → preview → accept → role granted → replay 410
- email mismatch on accept returns 403
- expired invite returns 410

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 frontend/components/TeamCard.vue              | 267 ++++++++++
 frontend/pages/dashboard/events/[id].vue      |   9 +
 frontend/pages/invites/[token].vue            | 136 ++++++
 internal/api/activity.go                      |   4 +-
 internal/api/authz.go                         |  49 ++
 internal/api/collaborators.go                 | 455 ++++++++++++++++++
 internal/api/csv_import.go                    |   8 +-
 internal/api/events.go                        |  36 +-
 internal/api/guests.go                        |  11 +-
 internal/api/server.go                        |  42 +-
 internal/api/tokens.go                        |   7 +-
 internal/api/ws_auth.go                       |   6 +-
 internal/auth/email.go                        |  15 +-
 internal/domain/collaborator.go               |  93 ++++
 internal/domain/collaborator_test.go          |  43 ++
 internal/notification/email_ses.go            |  12 +
 internal/notification/factory.go              |   7 +
 internal/notification/resend_sender.go        |  12 +
 internal/notification/smtp_sender.go          |  11 +
 internal/notification/templates.go            |  11 +-
 .../templates/collaborator_invite.html        |  16 +
 .../templates/collaborator_invite.txt         |   7 +
 internal/storage/collaborators.go             | 381 +++++++++++++++
 internal/storage/events.go                    |  96 +++-
 .../migrations/0008_collaborators.down.sql    |   7 +
 .../migrations/0008_collaborators.up.sql      |  65 +++
 test/integration/auth_test.go                 |   6 +
 test/integration/collaborators_test.go        | 328 +++++++++++++
 28 files changed, 2108 insertions(+), 32 deletions(-)
 create mode 100644 frontend/components/TeamCard.vue
 create mode 100644 frontend/pages/invites/[token].vue
 create mode 100644 internal/api/collaborators.go
 create mode 100644 internal/domain/collaborator.go
 create mode 100644 internal/domain/collaborator_test.go
 create mode 100644 internal/notification/templates/collaborator_invite.html
 create mode 100644 internal/notification/templates/collaborator_invite.txt
 create mode 100644 internal/storage/collaborators.go
 create mode 100644 internal/storage/migrations/0008_collaborators.down.sql
 create mode 100644 internal/storage/migrations/0008_collaborators.up.sql
 create mode 100644 test/integration/collaborators_test.go

diff --git a/frontend/components/TeamCard.vue b/frontend/components/TeamCard.vue
new file mode 100644
index 0000000..a8b3297
--- /dev/null
+++ b/frontend/components/TeamCard.vue
@@ -0,0 +1,267 @@
+<script setup lang="ts">
+// Tier 2 Block C — multi-host team management. Shown as a card on the event
+// detail page; visible to anyone with viewer+ role. Action buttons (invite,
+// role change, remove) are gated to owners — the server enforces this too.
+
+interface Collaborator {
+  user_id: string
+  name: string
+  email: string
+  role: 'owner' | 'editor' | 'viewer'
+  invited_at: string
+  accepted_at?: string | null
+}
+
+interface PendingInvite {
+  email: string
+  role: 'owner' | 'editor' | 'viewer'
+  expires_at: string
+  created_at: string
+}
+
+interface TeamResponse {
+  collaborators: Collaborator[]
+  pending: PendingInvite[]
+  your_role: 'owner' | 'editor' | 'viewer'
+}
+
+const props = defineProps<{
+  eventId: string
+  yourRole?: 'owner' | 'editor' | 'viewer' | null
+}>()
+
+const collaborators = ref<Collaborator[]>([])
+const pending = ref<PendingInvite[]>([])
+const loading = ref(true)
+const error = ref<string | null>(null)
+
+const isOwner = computed(() => props.yourRole === 'owner')
+
+async function refresh() {
+  try {
+    const data = await useApi<TeamResponse>(`/events/${props.eventId}/collaborators`)
+    collaborators.value = data.collaborators || []
+    pending.value = data.pending || []
+  } catch (e: any) {
+    error.value = useErrMessage(e, 'Could not load team')
+  } finally {
+    loading.value = false
+  }
+}
+onMounted(refresh)
+
+// --- invite modal ---
+const inviting = ref(false)
+const inviteEmail = ref('')
+const inviteRole = ref<'editor' | 'viewer'>('editor')
+const inviteInFlight = ref(false)
+const inviteError = ref<string | null>(null)
+
+function openInvite() {
+  inviteEmail.value = ''
+  inviteRole.value = 'editor'
+  inviteError.value = null
+  inviting.value = true
+}
+
+async function sendInvite() {
+  inviteInFlight.value = true
+  inviteError.value = null
+  try {
+    await useApi(`/events/${props.eventId}/collaborators`, {
+      method: 'POST',
+      body: { email: inviteEmail.value.trim(), role: inviteRole.value },
+    })
+    inviting.value = false
+    await refresh()
+  } catch (e: any) {
+    inviteError.value = useErrMessage(e, 'Could not send invite')
+  } finally {
+    inviteInFlight.value = false
+  }
+}
+
+// --- role change ---
+async function changeRole(c: Collaborator, role: 'owner' | 'editor' | 'viewer') {
+  if (c.role === role) return
+  try {
+    await useApi(`/events/${props.eventId}/collaborators/${c.user_id}`, {
+      method: 'PATCH',
+      body: { role },
+    })
+    await refresh()
+  } catch (e: any) {
+    error.value = useErrMessage(e, 'Could not change role')
+  }
+}
+
+// --- remove ---
+async function removeCollaborator(c: Collaborator) {
+  if (!confirm(`Remove ${c.name || c.email} from this event?`)) return
+  try {
+    await useApi(`/events/${props.eventId}/collaborators/${c.user_id}`, { method: 'DELETE' })
+    await refresh()
+  } catch (e: any) {
+    error.value = useErrMessage(e, 'Could not remove collaborator')
+  }
+}
+
+async function cancelPending(p: PendingInvite) {
+  if (!confirm(`Cancel invitation to ${p.email}?`)) return
+  try {
+    await useApi(`/events/${props.eventId}/collaborators/pending?email=${encodeURIComponent(p.email)}`, {
+      method: 'DELETE',
+    })
+    await refresh()
+  } catch (e: any) {
+    error.value = useErrMessage(e, 'Could not cancel invitation')
+  }
+}
+
+function fmtDate(iso?: string | null) {
+  if (!iso) return ''
+  try { return new Date(iso).toLocaleDateString() } catch { return iso }
+}
+</script>
+
+<template>
+  <section class="card">
+    <header class="mb-3 flex items-center justify-between">
+      <h2 class="text-lg font-semibold">Team</h2>
+      <button
+        v-if="isOwner"
+        type="button"
+        class="btn-primary text-sm"
+        @click="openInvite"
+      >Invite</button>
+    </header>
+    <p class="mb-4 text-xs text-zinc-500">
+      Collaborators can help manage this event. Owners can invite + change roles;
+      editors can manage guests + send messages; viewers can read but not change.
+    </p>
+
+    <p v-if="error" class="mb-3 text-sm text-red-400">{{ error }}</p>
+
+    <div v-if="loading" class="text-sm text-zinc-500">Loading team…</div>
+
+    <ul v-else-if="collaborators.length" class="space-y-2">
+      <li
+        v-for="c in collaborators"
+        :key="c.user_id"
+        class="flex items-center justify-between rounded-md border border-zinc-800 bg-zinc-950 px-3 py-2"
+      >
+        <div class="min-w-0 flex-1">
+          <div class="truncate text-sm font-medium text-zinc-100">{{ c.name || c.email }}</div>
+          <div class="truncate text-xs text-zinc-500">{{ c.email }}</div>
+        </div>
+        <div class="flex items-center gap-2">
+          <select
+            v-if="isOwner"
+            :value="c.role"
+            class="rounded border border-zinc-700 bg-zinc-900 px-2 py-1 text-xs text-zinc-100"
+            :aria-label="`Change role for ${c.name || c.email}`"
+            @change="(e) => changeRole(c, ((e.target as HTMLSelectElement).value as any))"
+          >
+            <option value="owner">Owner</option>
+            <option value="editor">Editor</option>
+            <option value="viewer">Viewer</option>
+          </select>
+          <span v-else class="badge bg-zinc-800 capitalize text-zinc-300">{{ c.role }}</span>
+          <button
+            v-if="isOwner"
+            type="button"
+            class="rounded-md p-1 text-zinc-500 transition hover:bg-red-500/10 hover:text-red-300"
+            :title="`Remove ${c.name || c.email}`"
+            :aria-label="`Remove ${c.name || c.email}`"
+            @click="removeCollaborator(c)"
+          >
+            <svg class="h-4 w-4" viewBox="0 0 20 20" fill="currentColor" aria-hidden="true">
+              <path d="M6 6L14 14M14 6L6 14" stroke="currentColor" stroke-width="2" stroke-linecap="round" />
+            </svg>
+          </button>
+        </div>
+      </li>
+    </ul>
+
+    <p v-else class="text-sm text-zinc-500">No collaborators yet.</p>
+
+    <div v-if="pending.length" class="mt-4">
+      <p class="mb-2 text-xs font-medium uppercase tracking-wider text-zinc-500">Pending invitations</p>
+      <ul class="space-y-2">
+        <li
+          v-for="p in pending"
+          :key="p.email"
+          class="flex items-center justify-between rounded-md border border-amber-900/40 bg-amber-950/10 px-3 py-2"
+        >
+          <div class="min-w-0 flex-1">
+            <div class="truncate text-sm font-medium text-zinc-100">{{ p.email }}</div>
+            <div class="text-xs text-zinc-500">
+              <span class="capitalize">{{ p.role }}</span> · expires {{ fmtDate(p.expires_at) }}
+            </div>
+          </div>
+          <button
+            v-if="isOwner"
+            type="button"
+            class="text-xs text-zinc-400 hover:text-red-300"
+            @click="cancelPending(p)"
+          >Cancel</button>
+        </li>
+      </ul>
+    </div>
+
+    <!-- Invite modal -->
+    <Teleport to="body">
+      <div
+        v-if="inviting"
+        class="fixed inset-0 z-40 flex items-center justify-center bg-black/60 p-4 backdrop-blur-sm"
+        @click.self="inviting = false"
+      >
+        <div
+          role="dialog"
+          aria-modal="true"
+          aria-labelledby="invite-title"
+          class="w-full max-w-md rounded-lg border border-zinc-800 bg-zinc-900 p-5 shadow-2xl"
+        >
+          <h3 id="invite-title" class="mb-1 text-base font-semibold">Invite a collaborator</h3>
+          <p class="mb-4 text-xs text-zinc-500">
+            They'll get an email with a link that's valid for 7 days. If they don't have a
+            GuestGuard account yet, they'll be prompted to create one.
+          </p>
+          <form class="space-y-3" @submit.prevent="sendInvite">
+            <div>
+              <label class="label">Email</label>
+              <input
+                v-model="inviteEmail"
+                type="email"
+                required
+                class="input"
+                placeholder="teammate@example.com"
+              />
+            </div>
+            <div>
+              <label class="label">Role</label>
+              <select v-model="inviteRole" class="input">
+                <option value="editor">Editor — manage guests + send messages</option>
+                <option value="viewer">Viewer — read-only access</option>
+              </select>
+            </div>
+            <p v-if="inviteError" class="text-sm text-red-400">{{ inviteError }}</p>
+            <div class="flex items-center justify-end gap-2 pt-2">
+              <button
+                type="button"
+                class="text-sm text-zinc-400 hover:text-zinc-200"
+                :disabled="inviteInFlight"
+                @click="inviting = false"
+              >Cancel</button>
+              <button
+                type="submit"
+                class="btn-primary"
+                :disabled="inviteInFlight || !inviteEmail.trim()"
+              >{{ inviteInFlight ? 'Sending…' : 'Send invite' }}</button>
+            </div>
+          </form>
+        </div>
+      </div>
+    </Teleport>
+  </section>
+</template>
diff --git a/frontend/pages/dashboard/events/[id].vue b/frontend/pages/dashboard/events/[id].vue
index 0bc2cf9..e145d97 100644
--- a/frontend/pages/dashboard/events/[id].vue
+++ b/frontend/pages/dashboard/events/[id].vue
@@ -35,6 +35,9 @@ interface EventDetail {
   status: string
   created_at: string
   updated_at: string
+  // Tier 2 Block C — caller's role on this event. The dashboard branches
+  // UI affordances off this rather than the legacy host_id check.
+  your_role?: 'owner' | 'editor' | 'viewer'
 }
 
 interface IssuedToken {
@@ -1117,6 +1120,12 @@ function checkLabel(band?: string): string {
       </aside>
     </div>
 
+    <!-- Team (Tier 2 Block C). Visible to anyone with viewer+ access; action
+         buttons gated to owners. -->
+    <div v-if="event" class="mt-6">
+      <TeamCard :event-id="eventId" :your-role="event.your_role" />
+    </div>
+
     <!-- ===== Modals ===== -->
     <!-- All modals share the same pattern: backdrop click + Esc close,
          role=dialog + aria-modal, primary action on the right.
diff --git a/frontend/pages/invites/[token].vue b/frontend/pages/invites/[token].vue
new file mode 100644
index 0000000..35e77a0
--- /dev/null
+++ b/frontend/pages/invites/[token].vue
@@ -0,0 +1,136 @@
+<script setup lang="ts">
+// Collaborator invite acceptance — Tier 2 Block C.
+//
+// Flow:
+//   1. Preview the invite (unauthed) so we can show the event name + role.
+//   2. If the visitor isn't signed in, redirect them to signup (preserving
+//      the invite path as redirect). The signup must use the invited email.
+//   3. After signup/login the user lands back here; POST /invites/{token}/accept
+//      and on success bounce them to /dashboard/events/{event_id}.
+
+interface InviteSummary {
+  event_id: string
+  event_name: string
+  role: 'owner' | 'editor' | 'viewer'
+  email: string
+  expires_at: string
+}
+
+const route = useRoute()
+const auth = useAuth()
+const token = route.params.token as string
+
+const loading = ref(true)
+const summary = ref<InviteSummary | null>(null)
+const loadError = ref<string | null>(null)
+
+const accepting = ref(false)
+const acceptError = ref<string | null>(null)
+
+onMounted(async () => {
+  try {
+    summary.value = await useApi<InviteSummary>(`/invites/${token}`)
+  } catch (e: any) {
+    loadError.value = useErrMessage(e, 'Invitation is invalid or expired.')
+  } finally {
+    loading.value = false
+  }
+})
+
+const signedIn = computed(() => !!auth.user.value)
+const emailMatches = computed(() => {
+  if (!summary.value || !auth.user.value) return false
+  return auth.user.value.email.trim().toLowerCase() === summary.value.email.trim().toLowerCase()
+})
+
+function goToSignup() {
+  // Pre-fill the email so the visitor isn't tempted to register a different
+  // one. The accept handler refuses to consume the invite if emails differ.
+  if (!summary.value) return
+  const target = `/signup?email=${encodeURIComponent(summary.value.email)}&redirect=${encodeURIComponent(route.fullPath)}`
+  navigateTo(target)
+}
+
+function goToLogin() {
+  if (!summary.value) return
+  const target = `/login?email=${encodeURIComponent(summary.value.email)}&redirect=${encodeURIComponent(route.fullPath)}`
+  navigateTo(target)
+}
+
+async function accept() {
+  if (!summary.value) return
+  accepting.value = true
+  acceptError.value = null
+  try {
+    const res = await useApi<{ event_id: string }>(`/invites/${token}/accept`, { method: 'POST' })
+    navigateTo(`/dashboard/events/${res.event_id}`)
+  } catch (e: any) {
+    acceptError.value = useErrMessage(e, 'Could not accept invitation')
+  } finally {
+    accepting.value = false
+  }
+}
+
+function fmtDate(iso?: string) {
+  if (!iso) return ''
+  try { return new Date(iso).toLocaleString() } catch { return iso }
+}
+</script>
+
+<template>
+  <section class="mx-auto max-w-xl py-10">
+    <div v-if="loading" class="text-sm text-zinc-500">Looking up your invitation…</div>
+
+    <div v-else-if="loadError" class="card border-red-900/60 bg-red-950/30">
+      <h1 class="mb-2 text-xl font-semibold text-red-200">Invitation unavailable</h1>
+      <p class="text-sm text-red-300">{{ loadError }}</p>
+      <p class="mt-4 text-xs text-zinc-500">
+        Ask the person who sent the invitation to resend it from the event's Team tab.
+      </p>
+    </div>
+
+    <div v-else-if="summary" class="card border-brand-900/60 bg-brand-950/20">
+      <p class="text-xs uppercase tracking-widest text-brand-500">Team invitation</p>
+      <h1 class="mb-1 text-2xl font-semibold">{{ summary.event_name }}</h1>
+      <p class="mb-5 text-sm text-zinc-400">
+        You've been invited as
+        <strong class="capitalize text-brand-300">{{ summary.role }}</strong>.
+      </p>
+
+      <div v-if="!signedIn" class="space-y-3">
+        <p class="text-sm">
+          Sign in or create a GuestGuard account for
+          <strong class="text-zinc-100">{{ summary.email }}</strong>
+          to accept.
+        </p>
+        <div class="flex gap-2">
+          <button class="btn-primary flex-1" @click="goToSignup">Create account</button>
+          <button class="btn-ghost flex-1" @click="goToLogin">Sign in</button>
+        </div>
+      </div>
+
+      <div v-else-if="!emailMatches" class="rounded-md border border-amber-900/60 bg-amber-950/20 p-3 text-sm">
+        <p class="text-amber-200">
+          You're signed in as <strong>{{ auth.user.value?.email }}</strong>,
+          but this invitation was sent to
+          <strong>{{ summary.email }}</strong>.
+        </p>
+        <p class="mt-2 text-xs text-amber-300/80">
+          Sign out and sign back in with the right account to accept.
+        </p>
+      </div>
+
+      <div v-else class="space-y-3">
+        <p class="text-sm">Ready to join? Accept the invitation below.</p>
+        <button class="btn-primary w-full" :disabled="accepting" @click="accept">
+          {{ accepting ? 'Accepting…' : `Accept and open event` }}
+        </button>
+        <p v-if="acceptError" class="text-sm text-red-400">{{ acceptError }}</p>
+      </div>
+
+      <p class="mt-5 border-t border-zinc-800 pt-4 text-xs text-zinc-500">
+        Expires {{ fmtDate(summary.expires_at) }}.
+      </p>
+    </div>
+  </section>
+</template>
diff --git a/internal/api/activity.go b/internal/api/activity.go
index 13600e8..ac5756a 100644
--- a/internal/api/activity.go
+++ b/internal/api/activity.go
@@ -5,6 +5,7 @@ import (
 	"sort"
 	"time"
 
+	"github.com/alchemistkay/guestguard/internal/domain"
 	"github.com/alchemistkay/guestguard/internal/storage"
 )
 
@@ -14,6 +15,7 @@ import (
 // who weren't watching when activity happened.
 type activityHandler struct {
 	events     *storage.EventRepo
+	collabs    *storage.CollaboratorRepo
 	rsvps      *storage.RSVPRepo
 	accessLogs *storage.AccessLogRepo
 }
@@ -48,7 +50,7 @@ func (h *activityHandler) list(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleViewer); !ok {
 		return
 	}
 
diff --git a/internal/api/authz.go b/internal/api/authz.go
index 36ee0e5..3410b4e 100644
--- a/internal/api/authz.go
+++ b/internal/api/authz.go
@@ -25,6 +25,11 @@ func hostFromContext(w http.ResponseWriter, r *http.Request) (uuid.UUID, bool) {
 // On mismatch (or missing event) it returns 404 — never 403 — so a cross-
 // tenant probe cannot tell the difference between "event doesn't exist" and
 // "exists but belongs to someone else".
+//
+// Pre-Block-C this checked the events.host_id column directly. Block C
+// preserves the same semantics for the owner-only handlers (events.Update,
+// events.Delete, collaborator management) — but for shared-role endpoints,
+// callers should use requireRole instead.
 func requireEventOwner(
 	w http.ResponseWriter,
 	r *http.Request,
@@ -42,3 +47,47 @@ func requireEventOwner(
 	}
 	return ev, true
 }
+
+// requireRole is the Block C authz gate. It resolves the user's role on the
+// event and confirms it's at least `min`. Missing role → 404 (avoids leaking
+// existence to outsiders). Role-too-low → 403 (the user IS on the event,
+// just not privileged enough — that's safe to surface; the UI will hide the
+// action anyway).
+//
+// On success it returns the event and the user's role so the handler can
+// branch on owner-only behaviours without a second lookup.
+func requireRole(
+	w http.ResponseWriter,
+	r *http.Request,
+	events *storage.EventRepo,
+	collabs *storage.CollaboratorRepo,
+	eventID, userID uuid.UUID,
+	min domain.Role,
+) (*domain.Event, domain.Role, bool) {
+	role, ok, err := collabs.RoleFor(r.Context(), eventID, userID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to resolve role")
+		return nil, "", false
+	}
+	if !ok {
+		// Not a collaborator. Treat the same way the legacy host_id check
+		// did: 404, no leak.
+		writeError(w, http.StatusNotFound, "event not found")
+		return nil, "", false
+	}
+	if !role.AtLeast(min) {
+		writeError(w, http.StatusForbidden, "insufficient role for this action")
+		return nil, "", false
+	}
+	ev, err := events.Get(r.Context(), eventID)
+	if err != nil {
+		if errors.Is(err, domain.ErrEventNotFound) {
+			// Race: the event was deleted between the role lookup and now.
+			writeError(w, http.StatusNotFound, "event not found")
+			return nil, "", false
+		}
+		writeError(w, http.StatusInternalServerError, "failed to load event")
+		return nil, "", false
+	}
+	return ev, role, true
+}
diff --git a/internal/api/collaborators.go b/internal/api/collaborators.go
new file mode 100644
index 0000000..33312c2
--- /dev/null
+++ b/internal/api/collaborators.go
@@ -0,0 +1,455 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/alchemistkay/guestguard/internal/auth"
+	"github.com/alchemistkay/guestguard/internal/domain"
+	"github.com/alchemistkay/guestguard/internal/storage"
+)
+
+// collaboratorHandler powers the per-event Team endpoints and the public
+// invite-accept flow. Tier 2 Block C.
+type collaboratorHandler struct {
+	logger        *slog.Logger
+	events        *storage.EventRepo
+	users         *storage.UserRepo
+	collabs       *storage.CollaboratorRepo
+	invites       *storage.InviteRepo
+	emails        auth.EmailSender
+	publicBaseURL string
+	inviteTTL     time.Duration
+}
+
+// --- responses ---
+
+type collaboratorView struct {
+	UserID     uuid.UUID  `json:"user_id"`
+	Name       string     `json:"name"`
+	Email      string     `json:"email"`
+	Role       domain.Role `json:"role"`
+	InvitedAt  time.Time  `json:"invited_at"`
+	AcceptedAt *time.Time `json:"accepted_at,omitempty"`
+}
+
+type pendingInviteView struct {
+	Email     string      `json:"email"`
+	Role      domain.Role `json:"role"`
+	InvitedBy uuid.UUID   `json:"invited_by"`
+	ExpiresAt time.Time   `json:"expires_at"`
+	CreatedAt time.Time   `json:"created_at"`
+}
+
+type listCollaboratorsResponse struct {
+	Collaborators []collaboratorView  `json:"collaborators"`
+	Pending       []pendingInviteView `json:"pending"`
+	// YourRole tells the UI which actions to hide. Echoed from requireRole
+	// so the client doesn't need a separate /me lookup per event view.
+	YourRole domain.Role `json:"your_role"`
+}
+
+// GET /events/{id}/collaborators — viewer+ can see the team list. Pending
+// invites are exposed too so editors can chase up unaccepted invitations,
+// not just owners.
+func (h *collaboratorHandler) list(w http.ResponseWriter, r *http.Request) {
+	hostID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	eventID, ok := parseIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	_, role, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleViewer)
+	if !ok {
+		return
+	}
+
+	members, err := h.collabs.List(r.Context(), eventID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to list collaborators")
+		return
+	}
+	views := make([]collaboratorView, 0, len(members))
+	for _, m := range members {
+		views = append(views, collaboratorView{
+			UserID:     m.UserID,
+			Name:       m.Name,
+			Email:      m.Email,
+			Role:       m.Role,
+			InvitedAt:  m.InvitedAt,
+			AcceptedAt: m.AcceptedAt,
+		})
+	}
+
+	pending, err := h.invites.ListPendingForEvent(r.Context(), eventID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to list pending invites")
+		return
+	}
+	pendingViews := make([]pendingInviteView, 0, len(pending))
+	for _, p := range pending {
+		pendingViews = append(pendingViews, pendingInviteView{
+			Email:     p.Email,
+			Role:      p.Role,
+			InvitedBy: p.InvitedBy,
+			ExpiresAt: p.ExpiresAt,
+			CreatedAt: p.CreatedAt,
+		})
+	}
+
+	writeJSON(w, http.StatusOK, listCollaboratorsResponse{
+		Collaborators: views,
+		Pending:       pendingViews,
+		YourRole:      role,
+	})
+}
+
+type inviteRequest struct {
+	Email string      `json:"email"`
+	Role  domain.Role `json:"role"`
+}
+
+type inviteResponse struct {
+	Email     string      `json:"email"`
+	Role      domain.Role `json:"role"`
+	ExpiresAt time.Time   `json:"expires_at"`
+	// Sent reports whether the email send succeeded. The invite is still
+	// usable from the host's side either way — they can resend.
+	Sent bool `json:"sent"`
+}
+
+// POST /events/{id}/collaborators — owner-only. Creates an invitation
+// token, emails it to the recipient. The recipient can accept whether or
+// not they already have a GuestGuard account.
+func (h *collaboratorHandler) invite(w http.ResponseWriter, r *http.Request) {
+	hostID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	eventID, ok := parseIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	event, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleOwner)
+	if !ok {
+		return
+	}
+
+	var req inviteRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid json")
+		return
+	}
+	email := strings.ToLower(strings.TrimSpace(req.Email))
+	if email == "" || !strings.Contains(email, "@") {
+		writeError(w, http.StatusBadRequest, "valid email required")
+		return
+	}
+	if !req.Role.Valid() {
+		writeError(w, http.StatusBadRequest, "role must be owner|editor|viewer")
+		return
+	}
+
+	// If the invitee already has an account AND is already a collaborator,
+	// short-circuit with a friendly 409 — no email, no DB churn.
+	if existing, err := h.users.GetByEmail(r.Context(), email); err == nil && existing != nil {
+		if _, already, err := h.collabs.RoleFor(r.Context(), eventID, existing.ID); err == nil && already {
+			writeError(w, http.StatusConflict, "user is already a collaborator on this event")
+			return
+		}
+	}
+
+	raw, hash, err := auth.NewOpaqueToken()
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to mint invite")
+		return
+	}
+	expiresAt := time.Now().UTC().Add(h.ttl())
+	if err := h.invites.Create(r.Context(), storage.CreateInviteParams{
+		EventID:   eventID,
+		Email:     email,
+		Role:      req.Role,
+		InvitedBy: hostID,
+		TokenHash: hash,
+		ExpiresAt: expiresAt,
+	}); err != nil {
+		h.logger.Error("create invite", "err", err, "event_id", eventID)
+		writeError(w, http.StatusInternalServerError, "failed to create invite")
+		return
+	}
+
+	// Email send is best-effort. Failure still leaves the invite in the DB
+	// so a Resend action from the UI can retry; we report `sent: false`
+	// so the host knows.
+	sent := h.emailInvite(r.Context(), email, hostID, event.Name, req.Role, raw)
+
+	writeJSON(w, http.StatusCreated, inviteResponse{
+		Email:     email,
+		Role:      req.Role,
+		ExpiresAt: expiresAt,
+		Sent:      sent,
+	})
+}
+
+// PATCH /events/{id}/collaborators/{user_id} — owner-only. Change another
+// collaborator's role. Demoting the last owner returns 400.
+type updateRoleRequest struct {
+	Role domain.Role `json:"role"`
+}
+
+func (h *collaboratorHandler) updateRole(w http.ResponseWriter, r *http.Request) {
+	hostID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	eventID, ok := parseIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleOwner); !ok {
+		return
+	}
+	userID, ok := parseIDParam(w, r, "user_id")
+	if !ok {
+		return
+	}
+
+	var req updateRoleRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid json")
+		return
+	}
+	if !req.Role.Valid() {
+		writeError(w, http.StatusBadRequest, "role must be owner|editor|viewer")
+		return
+	}
+
+	if err := h.collabs.UpdateRole(r.Context(), eventID, userID, req.Role); err != nil {
+		switch {
+		case errors.Is(err, domain.ErrCollaboratorNotFound):
+			writeError(w, http.StatusNotFound, "collaborator not found")
+		case errors.Is(err, domain.ErrLastOwner):
+			writeError(w, http.StatusBadRequest, "cannot demote the last owner — promote someone else first")
+		default:
+			h.logger.Error("update role", "err", err)
+			writeError(w, http.StatusInternalServerError, "failed to update role")
+		}
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// DELETE /events/{id}/collaborators/{user_id} — owner-only. Removing the
+// last owner returns 400.
+func (h *collaboratorHandler) remove(w http.ResponseWriter, r *http.Request) {
+	hostID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	eventID, ok := parseIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleOwner); !ok {
+		return
+	}
+	userID, ok := parseIDParam(w, r, "user_id")
+	if !ok {
+		return
+	}
+
+	if err := h.collabs.Remove(r.Context(), eventID, userID); err != nil {
+		switch {
+		case errors.Is(err, domain.ErrCollaboratorNotFound):
+			writeError(w, http.StatusNotFound, "collaborator not found")
+		case errors.Is(err, domain.ErrLastOwner):
+			writeError(w, http.StatusBadRequest, "cannot remove the last owner — promote someone else first")
+		default:
+			h.logger.Error("remove collaborator", "err", err)
+			writeError(w, http.StatusInternalServerError, "failed to remove collaborator")
+		}
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// DELETE /events/{id}/collaborators/pending — owner-only. Cancels a
+// still-unconsumed invite for the given email. Idempotent: no rows is a 204.
+func (h *collaboratorHandler) cancelInvite(w http.ResponseWriter, r *http.Request) {
+	hostID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	eventID, ok := parseIDParam(w, r, "id")
+	if !ok {
+		return
+	}
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleOwner); !ok {
+		return
+	}
+
+	email := strings.TrimSpace(r.URL.Query().Get("email"))
+	if email == "" {
+		writeError(w, http.StatusBadRequest, "email query parameter required")
+		return
+	}
+	if err := h.invites.DeletePendingByEmail(r.Context(), eventID, email); err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to cancel invite")
+		return
+	}
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// --- public invite-accept flow ---
+
+type inviteSummary struct {
+	EventID   uuid.UUID   `json:"event_id"`
+	EventName string      `json:"event_name"`
+	Role      domain.Role `json:"role"`
+	Email     string      `json:"email"`
+	ExpiresAt time.Time   `json:"expires_at"`
+}
+
+// GET /invites/{token} — preview the invitation. Used by the frontend
+// accept page to render "Foo invited you to Bar as Editor" before the user
+// hits Accept. Doesn't require auth — the caller might not have an account
+// yet. Returns the same error codes accept does so the UI can branch
+// cleanly.
+func (h *collaboratorHandler) previewInvite(w http.ResponseWriter, r *http.Request) {
+	inv, event, ok := h.loadInvite(w, r)
+	if !ok {
+		return
+	}
+	writeJSON(w, http.StatusOK, inviteSummary{
+		EventID:   inv.EventID,
+		EventName: event.Name,
+		Role:      inv.Role,
+		Email:     inv.Email,
+		ExpiresAt: inv.ExpiresAt,
+	})
+}
+
+type acceptResponse struct {
+	EventID uuid.UUID   `json:"event_id"`
+	Role    domain.Role `json:"role"`
+}
+
+// POST /invites/{token}/accept — authed: the caller must be logged in as
+// the invitee. If the email on the invite doesn't match the caller's
+// account, we 403 (mirrors how multi-tenant tools handle "this link was
+// sent to someone else"). Single-use; token is consumed atomically with
+// the collaborator insert.
+func (h *collaboratorHandler) acceptInvite(w http.ResponseWriter, r *http.Request) {
+	userID, ok := hostFromContext(w, r)
+	if !ok {
+		return
+	}
+	caller, err := h.users.GetByID(r.Context(), userID)
+	if err != nil || caller == nil {
+		writeError(w, http.StatusUnauthorized, "unauthenticated")
+		return
+	}
+	inv, event, ok := h.loadInvite(w, r)
+	if !ok {
+		return
+	}
+	if !strings.EqualFold(strings.TrimSpace(caller.Email), strings.TrimSpace(inv.Email)) {
+		writeError(w, http.StatusForbidden, "invitation was sent to a different email")
+		return
+	}
+
+	tokenHash := auth.HashOpaque(r.PathValue("token"))
+	if err := h.collabs.AcceptInvite(r.Context(), tokenHash, userID, inv.EventID, inv.InvitedBy, inv.Role); err != nil {
+		switch {
+		case errors.Is(err, domain.ErrInviteAlreadyConsumed):
+			writeError(w, http.StatusGone, "invitation already used")
+		case errors.Is(err, domain.ErrCollaboratorExists):
+			// Already on the event — treat as success (idempotent accept).
+			writeJSON(w, http.StatusOK, acceptResponse{EventID: inv.EventID, Role: inv.Role})
+		default:
+			h.logger.Error("accept invite", "err", err)
+			writeError(w, http.StatusInternalServerError, "failed to accept invite")
+		}
+		return
+	}
+	_ = event
+	writeJSON(w, http.StatusOK, acceptResponse{EventID: inv.EventID, Role: inv.Role})
+}
+
+// loadInvite validates the path token, fetches the invite (rejecting
+// expired/consumed/missing with the right status), and resolves the
+// associated event. Returns the invite + event on success.
+func (h *collaboratorHandler) loadInvite(w http.ResponseWriter, r *http.Request) (*domain.CollaboratorInvite, *domain.Event, bool) {
+	raw := r.PathValue("token")
+	if raw == "" {
+		writeError(w, http.StatusBadRequest, "missing invite token")
+		return nil, nil, false
+	}
+	inv, err := h.invites.Get(r.Context(), auth.HashOpaque(raw))
+	if err != nil {
+		switch {
+		case errors.Is(err, domain.ErrInviteNotFound):
+			writeError(w, http.StatusNotFound, "invitation not found")
+		case errors.Is(err, domain.ErrInviteExpired):
+			writeError(w, http.StatusGone, "invitation expired")
+		case errors.Is(err, domain.ErrInviteAlreadyConsumed):
+			writeError(w, http.StatusGone, "invitation already used")
+		default:
+			writeError(w, http.StatusInternalServerError, "failed to load invite")
+		}
+		return nil, nil, false
+	}
+	event, err := h.events.Get(r.Context(), inv.EventID)
+	if err != nil {
+		if errors.Is(err, domain.ErrEventNotFound) {
+			writeError(w, http.StatusNotFound, "event no longer exists")
+			return nil, nil, false
+		}
+		writeError(w, http.StatusInternalServerError, "failed to load event")
+		return nil, nil, false
+	}
+	return inv, event, true
+}
+
+// emailInvite dispatches the invite email via the configured sender.
+// Best-effort: a failure is logged + returns false so the response can flag
+// it; the invitation row is preserved in either case.
+func (h *collaboratorHandler) emailInvite(ctx context.Context, to string, inviterID uuid.UUID, eventName string, role domain.Role, raw string) bool {
+	if h.emails == nil {
+		return false
+	}
+	inviterName := ""
+	if inv, err := h.users.GetByID(ctx, inviterID); err == nil && inv != nil {
+		inviterName = inv.Name
+	}
+	link := h.acceptLink(raw)
+	if err := h.emails.SendCollaboratorInvite(ctx, to, inviterName, eventName, string(role), link); err != nil {
+		h.logger.Warn("send collaborator invite (continuing)", "err", err, "to", to)
+		return false
+	}
+	return true
+}
+
+func (h *collaboratorHandler) acceptLink(raw string) string {
+	base := h.publicBaseURL
+	if base == "" {
+		base = "http://localhost:3000"
+	}
+	return base + "/invites/" + raw
+}
+
+func (h *collaboratorHandler) ttl() time.Duration {
+	if h.inviteTTL > 0 {
+		return h.inviteTTL
+	}
+	return domain.DefaultInviteTTL
+}
diff --git a/internal/api/csv_import.go b/internal/api/csv_import.go
index 7933bb4..624d254 100644
--- a/internal/api/csv_import.go
+++ b/internal/api/csv_import.go
@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"github.com/alchemistkay/guestguard/internal/csvimport"
+	"github.com/alchemistkay/guestguard/internal/domain"
 	"github.com/alchemistkay/guestguard/internal/storage"
 )
 
@@ -18,6 +19,7 @@ const (
 type csvImportHandler struct {
 	guests   *storage.GuestRepo
 	events   *storage.EventRepo
+	collabs  *storage.CollaboratorRepo
 	enforcer *tierEnforcer
 }
 
@@ -46,7 +48,7 @@ func (h *csvImportHandler) preview(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 
@@ -80,7 +82,7 @@ func (h *csvImportHandler) commit(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 
@@ -141,7 +143,7 @@ func (h *csvImportHandler) template(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 	w.Header().Set("Content-Type", "text/csv; charset=utf-8")
diff --git a/internal/api/events.go b/internal/api/events.go
index 6121a7f..a436493 100644
--- a/internal/api/events.go
+++ b/internal/api/events.go
@@ -16,6 +16,7 @@ import (
 
 type eventHandler struct {
 	repo     *storage.EventRepo
+	collabs  *storage.CollaboratorRepo
 	enforcer *tierEnforcer
 }
 
@@ -90,6 +91,13 @@ func (h *eventHandler) create(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusCreated, ev)
 }
 
+// eventView wraps an Event with the caller's role so the dashboard UI can
+// branch (e.g. hide the "Delete event" button for editors/viewers).
+type eventView struct {
+	*domain.Event
+	YourRole domain.Role `json:"your_role"`
+}
+
 func (h *eventHandler) get(w http.ResponseWriter, r *http.Request) {
 	hostID, ok := hostFromContext(w, r)
 	if !ok {
@@ -99,11 +107,11 @@ func (h *eventHandler) get(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	ev, ok := requireEventOwner(w, r, h.repo, id, hostID)
+	ev, role, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleViewer)
 	if !ok {
 		return
 	}
-	writeJSON(w, http.StatusOK, ev)
+	writeJSON(w, http.StatusOK, eventView{Event: ev, YourRole: role})
 }
 
 func (h *eventHandler) list(w http.ResponseWriter, r *http.Request) {
@@ -116,7 +124,15 @@ func (h *eventHandler) list(w http.ResponseWriter, r *http.Request) {
 	limit := atoiOr(q.Get("limit"), 50)
 	offset := atoiOr(q.Get("offset"), 0)
 
-	events, err := h.repo.List(r.Context(), hostID, limit, offset)
+	// Block C: the dashboard shows every event the user has any role on,
+	// not just events they own. The collaborators repo gives us the id set;
+	// the events repo paginates the merged list.
+	collabIDs, err := h.collabs.ListEventIDsForUser(r.Context(), hostID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to resolve memberships")
+		return
+	}
+	events, err := h.repo.ListForUser(r.Context(), hostID, collabIDs, limit, offset)
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, "failed to list events")
 		return
@@ -150,6 +166,11 @@ func (h *eventHandler) update(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
+	// Block C: editor+ can patch event metadata. The plan reserves DELETE
+	// (and the existing host_id row) for owners only.
+	if _, _, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleEditor); !ok {
+		return
+	}
 
 	var req updateEventRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
@@ -180,7 +201,7 @@ func (h *eventHandler) update(w http.ResponseWriter, r *http.Request) {
 		params.Status = &s
 	}
 
-	ev, err := h.repo.Update(r.Context(), id, hostID, params)
+	ev, err := h.repo.UpdateByID(r.Context(), id, params)
 	if err != nil {
 		switch {
 		case errors.Is(err, domain.ErrEventNotFound):
@@ -204,7 +225,12 @@ func (h *eventHandler) delete(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if err := h.repo.Delete(r.Context(), id, hostID); err != nil {
+	// Block C: only owners can delete an event. Editors get 403; viewers
+	// and non-members get 404.
+	if _, _, ok := requireRole(w, r, h.repo, h.collabs, id, hostID, domain.RoleOwner); !ok {
+		return
+	}
+	if err := h.repo.DeleteByID(r.Context(), id); err != nil {
 		if errors.Is(err, domain.ErrEventNotFound) {
 			writeError(w, http.StatusNotFound, "event not found")
 			return
diff --git a/internal/api/guests.go b/internal/api/guests.go
index 3665bc6..e8f8b64 100644
--- a/internal/api/guests.go
+++ b/internal/api/guests.go
@@ -12,6 +12,7 @@ import (
 type guestHandler struct {
 	guests   *storage.GuestRepo
 	events   *storage.EventRepo
+	collabs  *storage.CollaboratorRepo
 	enforcer *tierEnforcer
 }
 
@@ -33,7 +34,7 @@ func (h *guestHandler) create(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 	if !h.enforcer.allowGuestCreate(w, r, hostID, eventID) {
@@ -93,7 +94,7 @@ func (h *guestHandler) update(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 
@@ -143,7 +144,7 @@ func (h *guestHandler) delete(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor); !ok {
 		return
 	}
 	if err := h.guests.Delete(r.Context(), eventID, guestID); err != nil {
@@ -166,7 +167,9 @@ func (h *guestHandler) list(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	// Listing guests is viewer+. Editing is gated separately at the
+	// PATCH/POST/DELETE call sites.
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleViewer); !ok {
 		return
 	}
 
diff --git a/internal/api/server.go b/internal/api/server.go
index 1de6761..611b665 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -36,6 +36,7 @@ type Server struct {
 	billing   *billingHandler
 	stripeWH  *stripeWebhookHandler
 	privacy   *privacyHandler
+	collabs   *collaboratorHandler
 }
 
 type ServerDeps struct {
@@ -84,6 +85,8 @@ func NewServer(deps ServerDeps) (*Server, error) {
 	rsvpRepo := storage.NewRSVPRepo(deps.DB)
 	accessRepo := storage.NewAccessLogRepo(deps.DB)
 	userRepo := storage.NewUserRepo(deps.DB)
+	collabRepo := storage.NewCollaboratorRepo(deps.DB)
+	inviteRepo := storage.NewInviteRepo(deps.DB)
 	verifRepo := storage.NewEmailVerificationRepo(deps.DB)
 	resetRepo := storage.NewPasswordResetRepo(deps.DB)
 	refreshRepo := storage.NewRefreshTokenRepo(deps.DB)
@@ -152,8 +155,8 @@ func NewServer(deps ServerDeps) (*Server, error) {
 		hub:    hub,
 		authH:  authH,
 		me:     &meHandler{users: userRepo},
-		events: &eventHandler{repo: eventRepo, enforcer: enforcer},
-		guests: &guestHandler{guests: guestRepo, events: eventRepo, enforcer: enforcer},
+		events: &eventHandler{repo: eventRepo, collabs: collabRepo, enforcer: enforcer},
+		guests: &guestHandler{guests: guestRepo, events: eventRepo, collabs: collabRepo, enforcer: enforcer},
 		tokens: &tokenHandler{
 			logger:        deps.Logger,
 			guests:        guestRepo,
@@ -162,6 +165,7 @@ func NewServer(deps ServerDeps) (*Server, error) {
 			users:         userRepo,
 			accessLogs:    accessRepo,
 			rsvps:         rsvpRepo,
+			collabs:       collabRepo,
 			gen:           auth.NewGenerator(),
 			ttl:           deps.TokenTTL,
 			pub:           deps.AccessPublisher,
@@ -180,11 +184,12 @@ func NewServer(deps ServerDeps) (*Server, error) {
 		},
 		activity: &activityHandler{
 			events:     eventRepo,
+			collabs:    collabRepo,
 			rsvps:      rsvpRepo,
 			accessLogs: accessRepo,
 		},
 		ws:       &wsHandler{logger: deps.Logger, hub: hub, tickets: wsTickets},
-		wsTicket: &wsTicketHandler{tickets: wsTickets, events: eventRepo},
+		wsTicket: &wsTicketHandler{tickets: wsTickets, events: eventRepo, collabs: collabRepo},
 		health:  &healthHandler{pool: deps.DB.Pool},
 		signer:  signer,
 		limiter: limiter,
@@ -198,7 +203,7 @@ func NewServer(deps ServerDeps) (*Server, error) {
 			notifs:    deps.NotificationRepo,
 			suppress:  deps.SuppressionRepo,
 		},
-		csv: &csvImportHandler{guests: guestRepo, events: eventRepo, enforcer: enforcer},
+		csv: &csvImportHandler{guests: guestRepo, events: eventRepo, collabs: collabRepo, enforcer: enforcer},
 		billing: &billingHandler{
 			logger:        deps.Logger,
 			stripe:        deps.StripeClient,
@@ -211,6 +216,15 @@ func NewServer(deps ServerDeps) (*Server, error) {
 			stripe: deps.StripeClient,
 			subs:   subRepo,
 		},
+		collabs: &collaboratorHandler{
+			logger:        deps.Logger,
+			events:        eventRepo,
+			users:         userRepo,
+			collabs:       collabRepo,
+			invites:       inviteRepo,
+			emails:        emails,
+			publicBaseURL: deps.PublicBaseURL,
+		},
 		privacy: &privacyHandler{
 			logger:  deps.Logger,
 			users:   userRepo,
@@ -293,6 +307,26 @@ func (s *Server) Handler() http.Handler {
 
 	mux.Handle("GET /events/{id}/activity", authed(http.HandlerFunc(s.activity.list)))
 
+	// Block C — collaborators (multi-host). All under /events/{id}/collaborators.
+	// requireRole inside each handler enforces the right minimum role.
+	mux.Handle("GET /events/{id}/collaborators",
+		authed(http.HandlerFunc(s.collabs.list)))
+	mux.Handle("POST /events/{id}/collaborators",
+		authed(rl("collab_invite", 50, 24*time.Hour, userIDKey, http.HandlerFunc(s.collabs.invite))))
+	mux.Handle("PATCH /events/{id}/collaborators/{user_id}",
+		authed(http.HandlerFunc(s.collabs.updateRole)))
+	mux.Handle("DELETE /events/{id}/collaborators/{user_id}",
+		authed(http.HandlerFunc(s.collabs.remove)))
+	mux.Handle("DELETE /events/{id}/collaborators/pending",
+		authed(http.HandlerFunc(s.collabs.cancelInvite)))
+
+	// Invite acceptance — preview is unauthed (the invitee may not be
+	// logged in yet); accept requires auth (the caller's account must
+	// exist + match the invited email).
+	mux.HandleFunc("GET /invites/{token}", s.collabs.previewInvite)
+	mux.Handle("POST /invites/{token}/accept",
+		authed(http.HandlerFunc(s.collabs.acceptInvite)))
+
 	mux.Handle("POST /events/{id}/guests/{guest_id}/tokens",
 		authed(rl("tokens_issue", 500, 24*time.Hour, userIDKey, http.HandlerFunc(s.tokens.issue))))
 	mux.Handle("POST /events/{id}/guests/{guest_id}/tokens/rotate",
diff --git a/internal/api/tokens.go b/internal/api/tokens.go
index 89322d6..dd87e3d 100644
--- a/internal/api/tokens.go
+++ b/internal/api/tokens.go
@@ -34,6 +34,7 @@ type tokenHandler struct {
 	users         *storage.UserRepo
 	accessLogs    *storage.AccessLogRepo
 	rsvps         *storage.RSVPRepo
+	collabs       *storage.CollaboratorRepo
 	gen           *auth.Generator
 	ttl           time.Duration
 	pub           accessPublisher
@@ -63,7 +64,7 @@ func (h *tokenHandler) issue(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
+	event, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor)
 	if !ok {
 		return
 	}
@@ -214,7 +215,7 @@ func (h *tokenHandler) bulkIssue(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
+	event, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor)
 	if !ok {
 		return
 	}
@@ -344,7 +345,7 @@ func (h *tokenHandler) rotate(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	event, ok := requireEventOwner(w, r, h.events, eventID, hostID)
+	event, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleEditor)
 	if !ok {
 		return
 	}
diff --git a/internal/api/ws_auth.go b/internal/api/ws_auth.go
index f070ed8..65fa49c 100644
--- a/internal/api/ws_auth.go
+++ b/internal/api/ws_auth.go
@@ -5,12 +5,14 @@ import (
 	"net/http"
 	"time"
 
+	"github.com/alchemistkay/guestguard/internal/domain"
 	"github.com/alchemistkay/guestguard/internal/storage"
 )
 
 type wsTicketHandler struct {
 	tickets *wsTicketStore
 	events  *storage.EventRepo
+	collabs *storage.CollaboratorRepo
 }
 
 type wsTicketResponse struct {
@@ -38,7 +40,9 @@ func (h *wsTicketHandler) issue(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
-	if _, ok := requireEventOwner(w, r, h.events, eventID, hostID); !ok {
+	// Block C: viewers can subscribe to the live monitor too — the WS stream
+	// only carries read-only events (RSVPs, fraud scores, check-ins).
+	if _, _, ok := requireRole(w, r, h.events, h.collabs, eventID, hostID, domain.RoleViewer); !ok {
 		return
 	}
 
diff --git a/internal/auth/email.go b/internal/auth/email.go
index 27e8102..5a3ad9f 100644
--- a/internal/auth/email.go
+++ b/internal/auth/email.go
@@ -5,12 +5,14 @@ import (
 	"log/slog"
 )
 
-// EmailSender delivers transactional auth emails (verification, reset).
-// Block A ships LogSender so dev environments work without Twilio/SES.
-// Block D replaces this with a real SES-backed sender.
+// EmailSender delivers transactional auth emails (verification, reset,
+// collaborator-invite). Block A ships LogSender so dev environments work
+// without Twilio/SES. Tier 1 Block D replaced this with a real SES-backed
+// sender; Tier 2 Block C added the collaborator-invite method.
 type EmailSender interface {
 	SendVerification(ctx context.Context, to, name, link string) error
 	SendPasswordReset(ctx context.Context, to, name, link string) error
+	SendCollaboratorInvite(ctx context.Context, to, inviterName, eventName, role, link string) error
 }
 
 type LogEmailSender struct {
@@ -30,3 +32,10 @@ func (l LogEmailSender) SendPasswordReset(_ context.Context, to, name, link stri
 	)
 	return nil
 }
+
+func (l LogEmailSender) SendCollaboratorInvite(_ context.Context, to, inviterName, eventName, role, link string) error {
+	l.Logger.Info("auth email (stub): collaborator invite",
+		"to", to, "inviter", inviterName, "event", eventName, "role", role, "link", link,
+	)
+	return nil
+}
diff --git a/internal/domain/collaborator.go b/internal/domain/collaborator.go
new file mode 100644
index 0000000..d9dde9c
--- /dev/null
+++ b/internal/domain/collaborator.go
@@ -0,0 +1,93 @@
+package domain
+
+import (
+	"errors"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Role is the trio of collaborator permissions on an event. Comparisons are
+// done with the numeric `rank()` rather than string equality so handlers can
+// say `requireRole(RoleEditor)` and accept both editor and owner.
+type Role string
+
+const (
+	RoleOwner  Role = "owner"
+	RoleEditor Role = "editor"
+	RoleViewer Role = "viewer"
+)
+
+// Valid reports whether r is one of the three known roles.
+func (r Role) Valid() bool {
+	switch r {
+	case RoleOwner, RoleEditor, RoleViewer:
+		return true
+	}
+	return false
+}
+
+// rank returns a comparable integer: higher = more privilege.
+// Owner=30 / Editor=20 / Viewer=10 leaves room for future intermediate
+// roles (e.g. "guest-manager" at 15) without renumbering callers.
+func (r Role) rank() int {
+	switch r {
+	case RoleOwner:
+		return 30
+	case RoleEditor:
+		return 20
+	case RoleViewer:
+		return 10
+	}
+	return 0
+}
+
+// AtLeast reports whether r is at least as privileged as min.
+// requireRole helpers compare with `r.AtLeast(RoleEditor)`.
+func (r Role) AtLeast(min Role) bool {
+	return r.rank() >= min.rank()
+}
+
+// Collaborator is one user's membership on an event. AcceptedAt is nil while
+// the invite is still pending — those rows are surfaced separately, not via
+// this struct (see CollaboratorInvite).
+type Collaborator struct {
+	EventID    uuid.UUID  `json:"event_id"`
+	UserID     uuid.UUID  `json:"user_id"`
+	Role       Role       `json:"role"`
+	InvitedBy  *uuid.UUID `json:"invited_by,omitempty"`
+	InvitedAt  time.Time  `json:"invited_at"`
+	AcceptedAt *time.Time `json:"accepted_at,omitempty"`
+
+	// Display fields joined from users — populated by List, omitted by point
+	// lookups that don't need them.
+	Name  string `json:"name,omitempty"`
+	Email string `json:"email,omitempty"`
+}
+
+// CollaboratorInvite is a pending invitation that hasn't been accepted yet.
+// The raw token lives only in the email link; what we store is its SHA-256
+// hash, so a database leak doesn't hand attackers usable invites.
+type CollaboratorInvite struct {
+	EventID   uuid.UUID `json:"event_id"`
+	Email     string    `json:"email"`
+	Role      Role      `json:"role"`
+	InvitedBy uuid.UUID `json:"invited_by"`
+	ExpiresAt time.Time `json:"expires_at"`
+	CreatedAt time.Time `json:"created_at"`
+}
+
+// DefaultInviteTTL is how long a fresh collaborator invitation stays valid.
+// Seven days mirrors the password-reset flow's expiry. Resend mints a new
+// token rather than extending an old one.
+const DefaultInviteTTL = 7 * 24 * time.Hour
+
+var (
+	ErrCollaboratorNotFound    = errors.New("collaborator not found")
+	ErrCollaboratorExists      = errors.New("user is already a collaborator")
+	ErrLastOwner               = errors.New("cannot remove the last owner")
+	ErrInviteNotFound          = errors.New("invitation not found")
+	ErrInviteExpired           = errors.New("invitation expired")
+	ErrInviteAlreadyConsumed   = errors.New("invitation already used")
+	ErrInviteEmailMismatch     = errors.New("invitation was sent to a different email")
+)
diff --git a/internal/domain/collaborator_test.go b/internal/domain/collaborator_test.go
new file mode 100644
index 0000000..b6f77de
--- /dev/null
+++ b/internal/domain/collaborator_test.go
@@ -0,0 +1,43 @@
+package domain
+
+import "testing"
+
+func TestRoleAtLeast(t *testing.T) {
+	tests := []struct {
+		have Role
+		min  Role
+		want bool
+	}{
+		{RoleOwner, RoleOwner, true},
+		{RoleOwner, RoleEditor, true},
+		{RoleOwner, RoleViewer, true},
+		{RoleEditor, RoleOwner, false},
+		{RoleEditor, RoleEditor, true},
+		{RoleEditor, RoleViewer, true},
+		{RoleViewer, RoleOwner, false},
+		{RoleViewer, RoleEditor, false},
+		{RoleViewer, RoleViewer, true},
+
+		// Empty / unknown role should not satisfy any minimum.
+		{Role(""), RoleViewer, false},
+		{Role("admin"), RoleViewer, false},
+	}
+	for _, tt := range tests {
+		if got := tt.have.AtLeast(tt.min); got != tt.want {
+			t.Errorf("Role(%q).AtLeast(%q) = %v, want %v", tt.have, tt.min, got, tt.want)
+		}
+	}
+}
+
+func TestRoleValid(t *testing.T) {
+	for _, r := range []Role{RoleOwner, RoleEditor, RoleViewer} {
+		if !r.Valid() {
+			t.Errorf("expected %q to be valid", r)
+		}
+	}
+	for _, r := range []Role{Role(""), Role("admin"), Role("OWNER")} {
+		if r.Valid() {
+			t.Errorf("expected %q to be invalid", r)
+		}
+	}
+}
diff --git a/internal/notification/email_ses.go b/internal/notification/email_ses.go
index c2ee207..a63ca67 100644
--- a/internal/notification/email_ses.go
+++ b/internal/notification/email_ses.go
@@ -90,6 +90,18 @@ func (s *SESEmailSender) SendPasswordReset(ctx context.Context, to, name, link s
 		})
 }
 
+// SendCollaboratorInvite renders the team-invite template and posts it to SES.
+func (s *SESEmailSender) SendCollaboratorInvite(ctx context.Context, to, inviterName, eventName, role, link string) error {
+	return s.sendTemplated(ctx, to,
+		inviterName+" invited you to "+eventName,
+		TmplCollaboratorInvite, map[string]any{
+			"InviterName": inviterName,
+			"EventName":   eventName,
+			"Role":        role,
+			"Link":        link,
+		})
+}
+
 // SendGuest is used by the notifier worker for invitation / confirmation /
 // reminder emails — anything addressed at a guest.
 func (s *SESEmailSender) SendGuest(ctx context.Context, to, subject string, name TemplateName, data map[string]any) (providerMessageID string, err error) {
diff --git a/internal/notification/factory.go b/internal/notification/factory.go
index dbdff80..30f7de3 100644
--- a/internal/notification/factory.go
+++ b/internal/notification/factory.go
@@ -33,6 +33,7 @@ type EmailSenderConfig struct {
 type CombinedEmailSender interface {
 	SendVerification(ctx context.Context, to, name, link string) error
 	SendPasswordReset(ctx context.Context, to, name, link string) error
+	SendCollaboratorInvite(ctx context.Context, to, inviterName, eventName, role, link string) error
 	SendGuest(ctx context.Context, to, subject string, name TemplateName, data map[string]any) (string, error)
 }
 
@@ -81,6 +82,12 @@ func (l *logCombinedSender) SendPasswordReset(_ context.Context, to, name, link
 	return nil
 }
 
+func (l *logCombinedSender) SendCollaboratorInvite(_ context.Context, to, inviterName, eventName, role, link string) error {
+	l.logger.Info("auth email (stub): collaborator invite",
+		"to", to, "inviter", inviterName, "event", eventName, "role", role, "link", link)
+	return nil
+}
+
 func (l *logCombinedSender) SendGuest(_ context.Context, to, subject string, name TemplateName, data map[string]any) (string, error) {
 	if data == nil {
 		data = map[string]any{}
diff --git a/internal/notification/resend_sender.go b/internal/notification/resend_sender.go
index 6873205..bc82489 100644
--- a/internal/notification/resend_sender.go
+++ b/internal/notification/resend_sender.go
@@ -71,6 +71,18 @@ func (s *ResendEmailSender) SendPasswordReset(ctx context.Context, to, name, lin
 	return err
 }
 
+func (s *ResendEmailSender) SendCollaboratorInvite(ctx context.Context, to, inviterName, eventName, role, link string) error {
+	_, err := s.sendTemplated(ctx, to,
+		inviterName+" invited you to "+eventName,
+		TmplCollaboratorInvite, map[string]any{
+			"InviterName": inviterName,
+			"EventName":   eventName,
+			"Role":        role,
+			"Link":        link,
+		})
+	return err
+}
+
 // --- GuestEmailDispatcher ---
 
 func (s *ResendEmailSender) SendGuest(ctx context.Context, to, subject string, name TemplateName, data map[string]any) (string, error) {
diff --git a/internal/notification/smtp_sender.go b/internal/notification/smtp_sender.go
index e7b60ee..679ccad 100644
--- a/internal/notification/smtp_sender.go
+++ b/internal/notification/smtp_sender.go
@@ -72,6 +72,17 @@ func (s *SMTPEmailSender) SendPasswordReset(ctx context.Context, to, name, link
 		TmplPasswordReset, map[string]any{"Name": name, "Link": link, "ExpiryHumane": "1 hour"})
 }
 
+func (s *SMTPEmailSender) SendCollaboratorInvite(ctx context.Context, to, inviterName, eventName, role, link string) error {
+	return s.sendTemplated(ctx, to,
+		inviterName+" invited you to "+eventName,
+		TmplCollaboratorInvite, map[string]any{
+			"InviterName": inviterName,
+			"EventName":   eventName,
+			"Role":        role,
+			"Link":        link,
+		})
+}
+
 // --- GuestEmailDispatcher ---
 
 func (s *SMTPEmailSender) SendGuest(ctx context.Context, to, subject string, name TemplateName, data map[string]any) (string, error) {
diff --git a/internal/notification/templates.go b/internal/notification/templates.go
index 4f1f58a..9e8b7cd 100644
--- a/internal/notification/templates.go
+++ b/internal/notification/templates.go
@@ -19,11 +19,12 @@ var templatesFS embed.FS
 type TemplateName string
 
 const (
-	TmplVerification  TemplateName = "verification"
-	TmplPasswordReset TemplateName = "reset"
-	TmplInvitation    TemplateName = "invitation"
-	TmplConfirmation  TemplateName = "confirmation"
-	TmplReminder      TemplateName = "reminder"
+	TmplVerification        TemplateName = "verification"
+	TmplPasswordReset       TemplateName = "reset"
+	TmplInvitation          TemplateName = "invitation"
+	TmplConfirmation        TemplateName = "confirmation"
+	TmplReminder            TemplateName = "reminder"
+	TmplCollaboratorInvite  TemplateName = "collaborator_invite"
 )
 
 // Templates renders branded transactional emails for both HTML and
diff --git a/internal/notification/templates/collaborator_invite.html b/internal/notification/templates/collaborator_invite.html
new file mode 100644
index 0000000..20fff0c
--- /dev/null
+++ b/internal/notification/templates/collaborator_invite.html
@@ -0,0 +1,16 @@
+{{define "body"}}
+<p style="font-size:13px;letter-spacing:0.2em;text-transform:uppercase;color:#16a34a;margin:0 0 16px;">✦ Team invitation</p>
+<h1 style="font-size:24px;margin:0 0 4px;color:#0a0a0a;">{{.EventName}}</h1>
+<p style="margin:16px 0 20px;">
+  {{.InviterName}} invited you to collaborate on this event as
+  <strong>{{.Role}}</strong>.
+</p>
+<p style="margin:0 0 24px;text-align:center;">
+  <a href="{{.Link}}" style="background:#22c55e;color:#0a0a0a;padding:12px 22px;border-radius:8px;font-weight:600;text-decoration:none;display:inline-block;">Accept invitation</a>
+</p>
+<p style="margin:0 0 8px;color:#64748b;font-size:13px;">
+  This invitation expires in 7 days. If you don't have a GuestGuard account
+  yet, you'll be able to create one before accepting.
+</p>
+<p style="margin:8px 0 0;word-break:break-all;font-size:12px;color:#0f172a;">{{.Link}}</p>
+{{end}}
diff --git a/internal/notification/templates/collaborator_invite.txt b/internal/notification/templates/collaborator_invite.txt
new file mode 100644
index 0000000..6275ff3
--- /dev/null
+++ b/internal/notification/templates/collaborator_invite.txt
@@ -0,0 +1,7 @@
+{{.InviterName}} invited you to collaborate on "{{.EventName}}" as {{.Role}}.
+
+Accept the invitation:
+{{.Link}}
+
+This link expires in 7 days. If you don't have a GuestGuard account yet,
+you'll be able to create one before accepting.
diff --git a/internal/storage/collaborators.go b/internal/storage/collaborators.go
new file mode 100644
index 0000000..8eb5781
--- /dev/null
+++ b/internal/storage/collaborators.go
@@ -0,0 +1,381 @@
+package storage
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/alchemistkay/guestguard/internal/domain"
+)
+
+// CollaboratorRepo manages the event_collaborators table. The original host
+// has an "owner" row inserted by the migration backfill; everyone else lands
+// here via the invite-accept flow.
+type CollaboratorRepo struct {
+	pool *pgxpool.Pool
+}
+
+func NewCollaboratorRepo(db *DB) *CollaboratorRepo {
+	return &CollaboratorRepo{pool: db.Pool}
+}
+
+// RoleFor returns the user's role on the event, or empty + false when they
+// have none. The role-gate middleware uses this exact signature so a missing
+// row is rendered as 404 (matching the existing pre-Block-C behaviour where
+// the event "didn't exist" from the perspective of a non-owner).
+func (r *CollaboratorRepo) RoleFor(ctx context.Context, eventID, userID uuid.UUID) (domain.Role, bool, error) {
+	var role domain.Role
+	err := r.pool.QueryRow(ctx, `
+        SELECT role FROM event_collaborators
+        WHERE event_id = $1 AND user_id = $2 AND accepted_at IS NOT NULL
+    `, eventID, userID).Scan(&role)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return "", false, nil
+		}
+		return "", false, err
+	}
+	return role, true, nil
+}
+
+// AddAccepted inserts a collaborator row already marked as accepted (used by
+// the invite-accept flow). Returns ErrCollaboratorExists when the user is
+// already on the event regardless of role — the Team UI prevents the
+// duplicate, but we double-check at the DB layer.
+func (r *CollaboratorRepo) AddAccepted(ctx context.Context, eventID, userID, invitedBy uuid.UUID, role domain.Role) error {
+	_, err := r.pool.Exec(ctx, `
+        INSERT INTO event_collaborators (event_id, user_id, role, invited_by, invited_at, accepted_at)
+        VALUES ($1, $2, $3, $4, now(), now())
+    `, eventID, userID, role, invitedBy)
+	if err != nil {
+		var pgErr *pgconn.PgError
+		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
+			return domain.ErrCollaboratorExists
+		}
+		return err
+	}
+	return nil
+}
+
+// List returns every collaborator on the event with their user details
+// joined in. Owners + editors + viewers, ordered by role precedence then by
+// invited_at so the host's view stays stable.
+func (r *CollaboratorRepo) List(ctx context.Context, eventID uuid.UUID) ([]domain.Collaborator, error) {
+	rows, err := r.pool.Query(ctx, `
+        SELECT c.event_id, c.user_id, c.role, c.invited_by,
+               c.invited_at, c.accepted_at,
+               u.name, u.email
+        FROM event_collaborators c
+        JOIN users u ON u.id = c.user_id
+        WHERE c.event_id = $1
+        ORDER BY
+          CASE c.role
+            WHEN 'owner'  THEN 1
+            WHEN 'editor' THEN 2
+            WHEN 'viewer' THEN 3
+          END,
+          c.invited_at ASC
+    `, eventID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	out := []domain.Collaborator{}
+	for rows.Next() {
+		var c domain.Collaborator
+		if err := rows.Scan(
+			&c.EventID, &c.UserID, &c.Role, &c.InvitedBy,
+			&c.InvitedAt, &c.AcceptedAt, &c.Name, &c.Email,
+		); err != nil {
+			return nil, err
+		}
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// UpdateRole changes a collaborator's role. Refuses to demote the last
+// owner — if you'd be left with zero owners after the change, returns
+// ErrLastOwner and leaves the row untouched.
+func (r *CollaboratorRepo) UpdateRole(ctx context.Context, eventID, userID uuid.UUID, newRole domain.Role) error {
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback(ctx)
+
+	var currentRole domain.Role
+	err = tx.QueryRow(ctx, `
+        SELECT role FROM event_collaborators
+        WHERE event_id = $1 AND user_id = $2
+        FOR UPDATE
+    `, eventID, userID).Scan(&currentRole)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return domain.ErrCollaboratorNotFound
+		}
+		return err
+	}
+
+	// Demoting the last owner is the only ordering trap. Promote → owner is
+	// always fine.
+	if currentRole == domain.RoleOwner && newRole != domain.RoleOwner {
+		if err := assertNotLastOwner(ctx, tx, eventID); err != nil {
+			return err
+		}
+	}
+
+	if _, err := tx.Exec(ctx, `
+        UPDATE event_collaborators SET role = $3
+        WHERE event_id = $1 AND user_id = $2
+    `, eventID, userID, newRole); err != nil {
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+// Remove deletes a collaborator. Refuses to remove the last owner so the
+// event can't be orphaned. The host can demote-then-leave if they really
+// want out, but only after promoting someone else.
+func (r *CollaboratorRepo) Remove(ctx context.Context, eventID, userID uuid.UUID) error {
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback(ctx)
+
+	var currentRole domain.Role
+	err = tx.QueryRow(ctx, `
+        SELECT role FROM event_collaborators
+        WHERE event_id = $1 AND user_id = $2
+        FOR UPDATE
+    `, eventID, userID).Scan(&currentRole)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return domain.ErrCollaboratorNotFound
+		}
+		return err
+	}
+	if currentRole == domain.RoleOwner {
+		if err := assertNotLastOwner(ctx, tx, eventID); err != nil {
+			return err
+		}
+	}
+
+	if _, err := tx.Exec(ctx, `
+        DELETE FROM event_collaborators
+        WHERE event_id = $1 AND user_id = $2
+    `, eventID, userID); err != nil {
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+// assertNotLastOwner refuses to proceed when the event has exactly one
+// owner. Call inside a transaction that holds a row lock on the candidate
+// row so the count is accurate against concurrent removals.
+func assertNotLastOwner(ctx context.Context, tx pgx.Tx, eventID uuid.UUID) error {
+	var owners int
+	if err := tx.QueryRow(ctx, `
+        SELECT count(*) FROM event_collaborators
+        WHERE event_id = $1 AND role = 'owner'
+    `, eventID).Scan(&owners); err != nil {
+		return err
+	}
+	if owners <= 1 {
+		return domain.ErrLastOwner
+	}
+	return nil
+}
+
+// ListEventIDsForUser returns the set of event IDs the user has any accepted
+// role on. Used by GET /events to widen the dashboard list beyond just
+// `events.host_id = userID`.
+func (r *CollaboratorRepo) ListEventIDsForUser(ctx context.Context, userID uuid.UUID) ([]uuid.UUID, error) {
+	rows, err := r.pool.Query(ctx, `
+        SELECT event_id FROM event_collaborators
+        WHERE user_id = $1 AND accepted_at IS NOT NULL
+    `, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []uuid.UUID
+	for rows.Next() {
+		var id uuid.UUID
+		if err := rows.Scan(&id); err != nil {
+			return nil, err
+		}
+		out = append(out, id)
+	}
+	return out, rows.Err()
+}
+
+// --- invites ---
+
+type InviteRepo struct {
+	pool *pgxpool.Pool
+}
+
+func NewInviteRepo(db *DB) *InviteRepo {
+	return &InviteRepo{pool: db.Pool}
+}
+
+type CreateInviteParams struct {
+	EventID   uuid.UUID
+	Email     string
+	Role      domain.Role
+	InvitedBy uuid.UUID
+	TokenHash string
+	ExpiresAt time.Time
+}
+
+// Create writes an invite row. Multiple pending invites for the same email
+// on the same event are allowed; the most recent one wins because the user
+// only ever clicks the latest email. Old tokens stay valid until they
+// expire — that's fine, they all point at the same event/role tuple.
+func (r *InviteRepo) Create(ctx context.Context, p CreateInviteParams) error {
+	_, err := r.pool.Exec(ctx, `
+        INSERT INTO collaborator_invites
+            (token_hash, event_id, email, role, invited_by, expires_at)
+        VALUES ($1, $2, $3, $4, $5, $6)
+    `, p.TokenHash, p.EventID, strings.ToLower(strings.TrimSpace(p.Email)),
+		p.Role, p.InvitedBy, p.ExpiresAt)
+	return err
+}
+
+// Get loads an invite by token hash. Returns ErrInviteNotFound on miss,
+// ErrInviteExpired when the row exists but `expires_at` has passed, and
+// ErrInviteAlreadyConsumed when the invite was already accepted.
+func (r *InviteRepo) Get(ctx context.Context, tokenHash string) (*domain.CollaboratorInvite, error) {
+	var (
+		inv         domain.CollaboratorInvite
+		consumedAt  *time.Time
+	)
+	err := r.pool.QueryRow(ctx, `
+        SELECT event_id, email, role, invited_by, expires_at, consumed_at, created_at
+        FROM collaborator_invites
+        WHERE token_hash = $1
+    `, tokenHash).Scan(
+		&inv.EventID, &inv.Email, &inv.Role, &inv.InvitedBy,
+		&inv.ExpiresAt, &consumedAt, &inv.CreatedAt,
+	)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrInviteNotFound
+		}
+		return nil, err
+	}
+	if consumedAt != nil {
+		return nil, domain.ErrInviteAlreadyConsumed
+	}
+	if time.Now().UTC().After(inv.ExpiresAt) {
+		return nil, domain.ErrInviteExpired
+	}
+	return &inv, nil
+}
+
+// MarkConsumed flags the invite as used. Called inside the same transaction
+// that inserts the new event_collaborators row so the two states stay in
+// sync (no "accepted but invite still pending" race).
+func (r *InviteRepo) MarkConsumed(ctx context.Context, tokenHash string) error {
+	tag, err := r.pool.Exec(ctx, `
+        UPDATE collaborator_invites
+        SET consumed_at = now()
+        WHERE token_hash = $1 AND consumed_at IS NULL
+    `, tokenHash)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrInviteNotFound
+	}
+	return nil
+}
+
+// AcceptInvite atomically consumes the invite and inserts the collaborator
+// row. Returns ErrCollaboratorExists if the user already has a role on the
+// event (the invite is still consumed so the link can't be replayed).
+func (r *CollaboratorRepo) AcceptInvite(
+	ctx context.Context,
+	tokenHash string,
+	userID uuid.UUID,
+	eventID uuid.UUID,
+	invitedBy uuid.UUID,
+	role domain.Role,
+) error {
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback(ctx)
+
+	tag, err := tx.Exec(ctx, `
+        UPDATE collaborator_invites
+        SET consumed_at = now()
+        WHERE token_hash = $1 AND consumed_at IS NULL
+    `, tokenHash)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrInviteAlreadyConsumed
+	}
+
+	_, err = tx.Exec(ctx, `
+        INSERT INTO event_collaborators (event_id, user_id, role, invited_by, invited_at, accepted_at)
+        VALUES ($1, $2, $3, $4, now(), now())
+        ON CONFLICT (event_id, user_id) DO NOTHING
+    `, eventID, userID, role, invitedBy)
+	if err != nil {
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+// ListPendingForEvent returns invitations the host hasn't seen accepted yet,
+// shown alongside accepted collaborators on the Team tab.
+func (r *InviteRepo) ListPendingForEvent(ctx context.Context, eventID uuid.UUID) ([]domain.CollaboratorInvite, error) {
+	rows, err := r.pool.Query(ctx, `
+        SELECT event_id, email, role, invited_by, expires_at, created_at
+        FROM collaborator_invites
+        WHERE event_id = $1 AND consumed_at IS NULL
+        ORDER BY created_at DESC
+    `, eventID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := []domain.CollaboratorInvite{}
+	for rows.Next() {
+		var inv domain.CollaboratorInvite
+		if err := rows.Scan(
+			&inv.EventID, &inv.Email, &inv.Role, &inv.InvitedBy,
+			&inv.ExpiresAt, &inv.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		out = append(out, inv)
+	}
+	return out, rows.Err()
+}
+
+// DeletePendingByEmail clears any unconsumed invites for the (event, email)
+// pair. Called when the host cancels a pending invite from the Team UI.
+func (r *InviteRepo) DeletePendingByEmail(ctx context.Context, eventID uuid.UUID, email string) error {
+	_, err := r.pool.Exec(ctx, `
+        DELETE FROM collaborator_invites
+        WHERE event_id = $1
+          AND lower(email) = lower($2)
+          AND consumed_at IS NULL
+    `, eventID, strings.TrimSpace(email))
+	return err
+}
diff --git a/internal/storage/events.go b/internal/storage/events.go
index 048f2b1..6d59cd4 100644
--- a/internal/storage/events.go
+++ b/internal/storage/events.go
@@ -44,12 +44,22 @@ func (r *EventRepo) Create(ctx context.Context, p CreateEventParams) (*domain.Ev
 		return nil, fmt.Errorf("marshal settings: %w", err)
 	}
 
+	// Block C: every new event needs a row in event_collaborators pointing
+	// the host at the owner role. We do both inserts in one transaction so
+	// an event can never exist without its owner row (the migration backfill
+	// handles legacy events but not new ones).
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer tx.Rollback(ctx)
+
 	const q = `
         INSERT INTO events (host_id, name, slug, event_date, venue, max_capacity, settings, status)
         VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
         RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
     `
-	row := r.pool.QueryRow(ctx, q,
+	row := tx.QueryRow(ctx, q,
 		p.HostID, p.Name, p.Slug, p.EventDate, p.Venue, p.MaxCapacity, settingsJSON, p.Status,
 	)
 	ev, err := scanEvent(row)
@@ -60,6 +70,17 @@ func (r *EventRepo) Create(ctx context.Context, p CreateEventParams) (*domain.Ev
 		}
 		return nil, err
 	}
+
+	if _, err := tx.Exec(ctx, `
+        INSERT INTO event_collaborators (event_id, user_id, role, invited_at, accepted_at)
+        VALUES ($1, $2, 'owner', now(), now())
+    `, ev.ID, p.HostID); err != nil {
+		return nil, fmt.Errorf("seed owner collaborator: %w", err)
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return nil, err
+	}
 	return ev, nil
 }
 
@@ -96,6 +117,42 @@ func (r *EventRepo) GetForHost(ctx context.Context, id, hostID uuid.UUID) (*doma
 	return ev, nil
 }
 
+// ListForUser returns every event the user has any accepted role on. The
+// query unions events where the user is the legacy host_id with events
+// they collaborate on (via Block C). Duplicates are deduped on event id.
+// Block C — preferred over List for the dashboard since collaborators
+// should see shared events too.
+func (r *EventRepo) ListForUser(ctx context.Context, userID uuid.UUID, collabEventIDs []uuid.UUID, limit, offset int) ([]*domain.Event, error) {
+	if limit <= 0 || limit > 200 {
+		limit = 50
+	}
+	if offset < 0 {
+		offset = 0
+	}
+	rows, err := r.pool.Query(ctx, `
+        SELECT DISTINCT
+               id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
+        FROM events
+        WHERE host_id = $1
+           OR id = ANY($2::uuid[])
+        ORDER BY created_at DESC
+        LIMIT $3 OFFSET $4
+    `, userID, collabEventIDs, limit, offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []*domain.Event
+	for rows.Next() {
+		ev, err := scanEvent(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, ev)
+	}
+	return out, rows.Err()
+}
+
 func (r *EventRepo) List(ctx context.Context, hostID uuid.UUID, limit, offset int) ([]*domain.Event, error) {
 	if limit <= 0 || limit > 200 {
 		limit = 50
@@ -150,8 +207,21 @@ type UpdateEventParams struct {
 	Status      *domain.EventStatus
 }
 
+// UpdateByID applies the patch without an authz scope. Block C handlers
+// run requireRole first, so re-checking host_id here would block legitimate
+// editor-collaborators on someone else's event.
+func (r *EventRepo) UpdateByID(ctx context.Context, id uuid.UUID, p UpdateEventParams) (*domain.Event, error) {
+	return r.update(ctx, id, uuid.Nil, p, false)
+}
+
+// Update is the legacy host-scoped variant — preserved so a few owner-only
+// call sites stay terse. New code should prefer UpdateByID + requireRole.
 func (r *EventRepo) Update(ctx context.Context, id, hostID uuid.UUID, p UpdateEventParams) (*domain.Event, error) {
-	const q = `
+	return r.update(ctx, id, hostID, p, true)
+}
+
+func (r *EventRepo) update(ctx context.Context, id, hostID uuid.UUID, p UpdateEventParams, scopeToHost bool) (*domain.Event, error) {
+	q := `
         UPDATE events SET
             name         = COALESCE($3, name),
             slug         = COALESCE($4, slug),
@@ -161,7 +231,14 @@ func (r *EventRepo) Update(ctx context.Context, id, hostID uuid.UUID, p UpdateEv
             settings     = COALESCE($8, settings),
             status       = COALESCE($9, status),
             updated_at   = now()
-        WHERE id = $1 AND host_id = $2
+        WHERE id = $1`
+	if scopeToHost {
+		q += ` AND host_id = $2`
+	} else {
+		// Bind $2 anyway so the parameter count matches the call below.
+		q += ` AND ($2::uuid IS NULL OR $2::uuid = host_id OR TRUE)`
+	}
+	q += `
         RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
     `
 
@@ -202,6 +279,19 @@ func (r *EventRepo) Delete(ctx context.Context, id, hostID uuid.UUID) error {
 	return nil
 }
 
+// DeleteByID is the post-Block-C path: requireRole(Owner) is enforced by
+// the handler, so this query doesn't double-check host_id.
+func (r *EventRepo) DeleteByID(ctx context.Context, id uuid.UUID) error {
+	tag, err := r.pool.Exec(ctx, `DELETE FROM events WHERE id = $1`, id)
+	if err != nil {
+		return err
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrEventNotFound
+	}
+	return nil
+}
+
 type rowScanner interface {
 	Scan(dest ...any) error
 }
diff --git a/internal/storage/migrations/0008_collaborators.down.sql b/internal/storage/migrations/0008_collaborators.down.sql
new file mode 100644
index 0000000..33338b1
--- /dev/null
+++ b/internal/storage/migrations/0008_collaborators.down.sql
@@ -0,0 +1,7 @@
+DROP INDEX IF EXISTS idx_collab_invites_event;
+DROP TABLE IF EXISTS collaborator_invites;
+
+DROP INDEX IF EXISTS idx_collaborators_user;
+DROP TABLE IF EXISTS event_collaborators;
+
+DROP TYPE IF EXISTS collaborator_role;
diff --git a/internal/storage/migrations/0008_collaborators.up.sql b/internal/storage/migrations/0008_collaborators.up.sql
new file mode 100644
index 0000000..56ca0fd
--- /dev/null
+++ b/internal/storage/migrations/0008_collaborators.up.sql
@@ -0,0 +1,65 @@
+-- Tier 2 Block C — multi-host / collaborators.
+--
+-- An event can now have multiple users with one of three roles:
+--   owner   — full access incl. delete + manage collaborators
+--   editor  — guests/tokens/branding/messages/analytics
+--   viewer  — read-only
+--
+-- The existing events.host_id stays as a denormalised "primary owner"
+-- pointer (cheap join key, useful for the existing GET /events query). The
+-- source of truth for authz is event_collaborators — every handler resolves
+-- the caller's role through it.
+--
+-- Schema #0005 in TIER2_PLAN.md; landing at 0008 because earlier slots are
+-- taken by Tier 1 work.
+
+DO $$ BEGIN
+    CREATE TYPE collaborator_role AS ENUM ('owner', 'editor', 'viewer');
+EXCEPTION WHEN duplicate_object THEN NULL; END $$;
+
+CREATE TABLE IF NOT EXISTS event_collaborators (
+    event_id     UUID NOT NULL REFERENCES events(id) ON DELETE CASCADE,
+    user_id      UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    role         collaborator_role NOT NULL,
+    invited_by   UUID REFERENCES users(id) ON DELETE SET NULL,
+    invited_at   TIMESTAMPTZ NOT NULL DEFAULT now(),
+    accepted_at  TIMESTAMPTZ,
+    PRIMARY KEY (event_id, user_id)
+);
+
+-- Fast lookup of "what events does this user have any role on" — used by
+-- the dashboard list and the role-resolution middleware.
+CREATE INDEX IF NOT EXISTS idx_collaborators_user
+    ON event_collaborators(user_id);
+
+-- Pending invitations. The invitee may not have a GuestGuard account yet;
+-- the accept flow creates one (or links to an existing one by email) and
+-- promotes the row into event_collaborators.
+--
+-- token_hash is sha256(raw); the raw token only ever lives in the email
+-- link, never in the DB. consumed_at is set on successful accept so re-
+-- using the link returns 410 Gone instead of silently re-adding the user.
+CREATE TABLE IF NOT EXISTS collaborator_invites (
+    token_hash   TEXT PRIMARY KEY,
+    event_id     UUID NOT NULL REFERENCES events(id) ON DELETE CASCADE,
+    email        TEXT NOT NULL,
+    role         collaborator_role NOT NULL,
+    invited_by   UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    expires_at   TIMESTAMPTZ NOT NULL,
+    consumed_at  TIMESTAMPTZ,
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+-- Find pending invites for an event quickly (the "Team" tab lists them).
+-- Partial index keeps the working set small even on a busy event.
+CREATE INDEX IF NOT EXISTS idx_collab_invites_event
+    ON collaborator_invites(event_id)
+    WHERE consumed_at IS NULL;
+
+-- Backfill: every existing event's host becomes its owner. Idempotent so
+-- re-running this migration after a partial failure (or against a freshly
+-- restored backup that already has rows) does the right thing.
+INSERT INTO event_collaborators (event_id, user_id, role, accepted_at, invited_at)
+SELECT id, host_id, 'owner', created_at, created_at
+FROM events
+ON CONFLICT (event_id, user_id) DO NOTHING;
diff --git a/test/integration/auth_test.go b/test/integration/auth_test.go
index eb840e6..fe08d9c 100644
--- a/test/integration/auth_test.go
+++ b/test/integration/auth_test.go
@@ -29,6 +29,7 @@ const authTestPassword = "correct-horse-battery-staple"
 type recordingEmailSender struct {
 	verifyLink string
 	resetLink  string
+	inviteLink string
 }
 
 func (s *recordingEmailSender) SendVerification(_ context.Context, _, _, link string) error {
@@ -41,6 +42,11 @@ func (s *recordingEmailSender) SendPasswordReset(_ context.Context, _, _, link s
 	return nil
 }
 
+func (s *recordingEmailSender) SendCollaboratorInvite(_ context.Context, _, _, _, _, link string) error {
+	s.inviteLink = link
+	return nil
+}
+
 func TestAuthFlow(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping integration test in -short mode")
diff --git a/test/integration/collaborators_test.go b/test/integration/collaborators_test.go
new file mode 100644
index 0000000..e2f365f
--- /dev/null
+++ b/test/integration/collaborators_test.go
@@ -0,0 +1,328 @@
+//go:build integration
+
+package integration_test
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// Tier 2 Block C — multi-host / collaborators.
+
+// TestCollaboratorBackfill confirms the migration creates an `owner` row in
+// event_collaborators for every legacy event whose host_id pointed at a user.
+// Existing single-host events must keep working after Block C lands.
+func TestCollaboratorBackfill(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, host, token := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, token, "Backfill Test", "backfill-test")
+
+	var role string
+	must(t, db.Pool.QueryRow(ctx,
+		`SELECT role FROM event_collaborators
+         WHERE event_id = $1 AND user_id = $2`,
+		eventID, uuid.UUID(host),
+	).Scan(&role), "load backfilled role")
+	if role != "owner" {
+		t.Fatalf("backfilled role: got %q, want owner", role)
+	}
+}
+
+// TestCollaboratorRoleEnforcement exercises every endpoint at every role
+// boundary. This is the big regression net for the authz refactor — if any
+// handler dropped its requireRole call this test will catch it.
+func TestCollaboratorRoleEnforcement(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, ownerID, ownerToken := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, ownerToken, "Roles Test", "roles-test")
+
+	// Spin up two more verified users we can promote to editor / viewer.
+	editor, editorToken := makeAuthedUser(t, ctx, db.Pool)
+	viewer, viewerToken := makeAuthedUser(t, ctx, db.Pool)
+	directlyInsertCollaborator(t, ctx, db.Pool, eventID, editor, "editor", uuid.UUID(ownerID))
+	directlyInsertCollaborator(t, ctx, db.Pool, eventID, viewer, "viewer", uuid.UUID(ownerID))
+
+	guestID := createGuest(t, srv.URL, ownerToken, eventID, "Test Guest")
+
+	t.Run("viewer can read but not write", func(t *testing.T) {
+		// Read endpoints — 200.
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			viewerToken, nil, http.StatusOK)
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s/guests", srv.URL, eventID),
+			viewerToken, nil, http.StatusOK)
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s/activity", srv.URL, eventID),
+			viewerToken, nil, http.StatusOK)
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s/collaborators", srv.URL, eventID),
+			viewerToken, nil, http.StatusOK)
+
+		// Write endpoints — 403.
+		assertStatus(t, http.MethodPost, fmt.Sprintf("%s/events/%s/guests", srv.URL, eventID),
+			viewerToken, map[string]any{"name": "Should fail"}, http.StatusForbidden)
+		assertStatus(t, http.MethodPatch, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			viewerToken, map[string]any{"venue": "Other"}, http.StatusForbidden)
+		assertStatus(t, http.MethodDelete, fmt.Sprintf("%s/events/%s/guests/%s", srv.URL, eventID, guestID),
+			viewerToken, nil, http.StatusForbidden)
+
+		// Owner-only — 403 for both editor and viewer.
+		assertStatus(t, http.MethodDelete, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			viewerToken, nil, http.StatusForbidden)
+		assertStatus(t, http.MethodPost, fmt.Sprintf("%s/events/%s/collaborators", srv.URL, eventID),
+			viewerToken, map[string]any{"email": "x@x.com", "role": "viewer"}, http.StatusForbidden)
+	})
+
+	t.Run("editor can write guests + patch event but not delete or manage team", func(t *testing.T) {
+		// Editor adds a guest.
+		var g struct{ ID uuid.UUID `json:"id"` }
+		postJSONAuthed(t, fmt.Sprintf("%s/events/%s/guests", srv.URL, eventID),
+			editorToken, map[string]any{"name": "Editor's guest"}, http.StatusCreated, &g)
+
+		// Editor patches the event.
+		assertStatus(t, http.MethodPatch, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			editorToken, map[string]any{"venue": "Editor's Hall"}, http.StatusOK)
+
+		// Editor cannot delete the event.
+		assertStatus(t, http.MethodDelete, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			editorToken, nil, http.StatusForbidden)
+		// Editor cannot invite collaborators.
+		assertStatus(t, http.MethodPost, fmt.Sprintf("%s/events/%s/collaborators", srv.URL, eventID),
+			editorToken, map[string]any{"email": "x@x.com", "role": "viewer"}, http.StatusForbidden)
+	})
+
+	t.Run("non-member gets 404 even for read endpoints", func(t *testing.T) {
+		_, outsiderToken := makeAuthedUser(t, ctx, db.Pool)
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s", srv.URL, eventID),
+			outsiderToken, nil, http.StatusNotFound)
+		assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s/guests", srv.URL, eventID),
+			outsiderToken, nil, http.StatusNotFound)
+	})
+
+	t.Run("GET /events lists shared events for collaborators", func(t *testing.T) {
+		var list struct {
+			Events []struct {
+				ID uuid.UUID `json:"id"`
+			} `json:"events"`
+		}
+		getJSONAuthed(t, srv.URL+"/events", editorToken, http.StatusOK, &list)
+		found := false
+		for _, e := range list.Events {
+			if e.ID == eventID {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Fatalf("editor's /events did not include the shared event: %+v", list)
+		}
+	})
+}
+
+// TestCollaboratorRemoveLastOwner covers the "you can't orphan the event"
+// guarantee. Demote-then-remove must work for non-last owners; refusing on
+// the last is mandatory.
+func TestCollaboratorRemoveLastOwner(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, ownerID, ownerToken := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, ownerToken, "Last Owner", "last-owner")
+
+	// Cannot remove yourself when you're the only owner.
+	assertStatus(t, http.MethodDelete,
+		fmt.Sprintf("%s/events/%s/collaborators/%s", srv.URL, eventID, uuid.UUID(ownerID)),
+		ownerToken, nil, http.StatusBadRequest)
+
+	// Promote a second user to owner; now removing the first is allowed.
+	second, _ := makeAuthedUser(t, ctx, db.Pool)
+	directlyInsertCollaborator(t, ctx, db.Pool, eventID, second, "owner", uuid.UUID(ownerID))
+
+	assertStatus(t, http.MethodDelete,
+		fmt.Sprintf("%s/events/%s/collaborators/%s", srv.URL, eventID, uuid.UUID(ownerID)),
+		ownerToken, nil, http.StatusNoContent)
+}
+
+// TestCollaboratorInviteFlow walks the happy path: owner creates an invite,
+// the invitee accepts, they show up as a collaborator. Then re-using the
+// same invite token returns 410 Gone.
+func TestCollaboratorInviteFlow(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, _, ownerToken := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, ownerToken, "Invite Flow", "invite-flow")
+
+	// Make the invitee's account ahead of time so we can sign them in.
+	inviteeEmail := fmt.Sprintf("invitee-%d@guestguard.test", time.Now().UnixNano())
+	inviteeID := insertVerifiedUser(t, ctx, db.Pool, inviteeEmail, "Invitee")
+	inviteeToken := issueHostToken(t, inviteeID)
+
+	// Owner invites the user as editor.
+	assertStatus(t, http.MethodPost, fmt.Sprintf("%s/events/%s/collaborators", srv.URL, eventID),
+		ownerToken, map[string]any{"email": inviteeEmail, "role": "editor"}, http.StatusCreated)
+
+	// Pull the raw token out of the DB the way the email link would have.
+	// We don't surface it via the API (security), so reach into the table.
+	var tokenHash string
+	must(t, db.Pool.QueryRow(ctx, `
+        SELECT token_hash FROM collaborator_invites
+        WHERE event_id = $1 AND lower(email) = lower($2) AND consumed_at IS NULL
+        ORDER BY created_at DESC LIMIT 1
+    `, eventID, inviteeEmail).Scan(&tokenHash), "load invite hash")
+
+	// To get the raw token from the hash we can't reverse SHA256; so for
+	// tests we generate our own invite via the DB and use that raw value
+	// instead. Cleaner: replace the row with a known-token invite.
+	rawToken := fmt.Sprintf("test-raw-token-%d", time.Now().UnixNano())
+	sum := sha256.Sum256([]byte(rawToken))
+	knownHash := hex.EncodeToString(sum[:])
+	_, err := db.Pool.Exec(ctx, `
+        UPDATE collaborator_invites
+        SET token_hash = $1
+        WHERE token_hash = $2
+    `, knownHash, tokenHash)
+	must(t, err, "rewrite invite token_hash")
+
+	// Preview the invite (unauthed) — confirms the summary endpoint works.
+	previewResp, err := http.Get(srv.URL + "/invites/" + rawToken)
+	must(t, err, "preview invite")
+	previewResp.Body.Close()
+	if previewResp.StatusCode != http.StatusOK {
+		t.Fatalf("preview status: %d", previewResp.StatusCode)
+	}
+
+	// Accept (authed as invitee). Single-use; first call → 200.
+	assertStatus(t, http.MethodPost, srv.URL+"/invites/"+rawToken+"/accept",
+		inviteeToken, nil, http.StatusOK)
+
+	// Now the invitee has an editor role — they can list guests.
+	assertStatus(t, http.MethodGet, fmt.Sprintf("%s/events/%s/guests", srv.URL, eventID),
+		inviteeToken, nil, http.StatusOK)
+
+	// Replay the same token — already consumed → 410.
+	assertStatus(t, http.MethodPost, srv.URL+"/invites/"+rawToken+"/accept",
+		inviteeToken, nil, http.StatusGone)
+}
+
+// TestCollaboratorInviteEmailMismatch ensures a leaked invite link can't be
+// accepted by a different account.
+func TestCollaboratorInviteEmailMismatch(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, _, ownerToken := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, ownerToken, "Email Mismatch", "email-mismatch")
+
+	intendedEmail := fmt.Sprintf("intended-%d@guestguard.test", time.Now().UnixNano())
+	assertStatus(t, http.MethodPost, fmt.Sprintf("%s/events/%s/collaborators", srv.URL, eventID),
+		ownerToken, map[string]any{"email": intendedEmail, "role": "editor"}, http.StatusCreated)
+
+	// Replace with a known token, as in the happy-path test.
+	rawToken := fmt.Sprintf("test-mismatch-token-%d", time.Now().UnixNano())
+	sum := sha256.Sum256([]byte(rawToken))
+	hash := hex.EncodeToString(sum[:])
+	_, err := db.Pool.Exec(ctx, `
+        UPDATE collaborator_invites
+        SET token_hash = $1
+        WHERE event_id = $2 AND lower(email) = lower($3) AND consumed_at IS NULL
+    `, hash, eventID, intendedEmail)
+	must(t, err, "rewrite invite")
+
+	// A different user tries to accept the link.
+	otherID, otherToken := makeAuthedUser(t, ctx, db.Pool)
+	_ = otherID
+	assertStatus(t, http.MethodPost, srv.URL+"/invites/"+rawToken+"/accept",
+		otherToken, nil, http.StatusForbidden)
+}
+
+// TestCollaboratorInviteExpired tests that an old invite returns 410.
+func TestCollaboratorInviteExpired(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	t.Cleanup(cancel)
+
+	srv, db, ownerID, ownerToken := setupAuthedAPI(t, ctx)
+	eventID := createEvent(t, srv.URL, ownerToken, "Expired", "expired")
+
+	// Insert an already-expired invite directly so we don't have to wait
+	// seven days during the test.
+	rawToken := fmt.Sprintf("test-expired-%d", time.Now().UnixNano())
+	sum := sha256.Sum256([]byte(rawToken))
+	hash := hex.EncodeToString(sum[:])
+	_, err := db.Pool.Exec(ctx, `
+        INSERT INTO collaborator_invites
+            (token_hash, event_id, email, role, invited_by, expires_at)
+        VALUES ($1, $2, 'doesnt@matter.test', 'editor', $3, now() - interval '1 hour')
+    `, hash, eventID, uuid.UUID(ownerID))
+	must(t, err, "insert expired invite")
+
+	resp, err := http.Get(srv.URL + "/invites/" + rawToken)
+	must(t, err, "get expired preview")
+	resp.Body.Close()
+	if resp.StatusCode != http.StatusGone {
+		t.Fatalf("expected 410 Gone, got %d", resp.StatusCode)
+	}
+}
+
+// --- helpers used across collaborator tests ---
+
+// makeAuthedUser creates a verified user with a Business subscription and
+// returns the id + a bearer token signed with the test JWT secret.
+func makeAuthedUser(t *testing.T, ctx context.Context, pool *pgxpool.Pool) (uuid.UUID, string) {
+	t.Helper()
+	email := fmt.Sprintf("collab-%d@guestguard.test", time.Now().UnixNano())
+	id := insertVerifiedUser(t, ctx, pool, email, "Collab User")
+	grantBusinessTier(t, ctx, pool, id)
+	return id, issueHostToken(t, id)
+}
+
+// insertVerifiedUser creates a user row directly, bypassing signup/verify
+// so tests stay fast.
+func insertVerifiedUser(t *testing.T, ctx context.Context, pool *pgxpool.Pool, email, name string) uuid.UUID {
+	t.Helper()
+	var id uuid.UUID
+	must(t, pool.QueryRow(ctx, `
+        INSERT INTO users (email, name, email_verified, email_verified_at)
+        VALUES ($1, $2, TRUE, now())
+        RETURNING id
+    `, strings.ToLower(email), name).Scan(&id), "insert verified user")
+	return id
+}
+
+func directlyInsertCollaborator(t *testing.T, ctx context.Context, pool *pgxpool.Pool, eventID, userID uuid.UUID, role string, invitedBy uuid.UUID) {
+	t.Helper()
+	_, err := pool.Exec(ctx, `
+        INSERT INTO event_collaborators (event_id, user_id, role, invited_by, invited_at, accepted_at)
+        VALUES ($1, $2, $3, $4, now(), now())
+        ON CONFLICT (event_id, user_id) DO UPDATE SET role = EXCLUDED.role
+    `, eventID, userID, role, invitedBy)
+	must(t, err, "insert collaborator")
+}