diff --git a/internal/db/migrations/064_users_forum_pref.down.sql b/internal/db/migrations/064_users_forum_pref.down.sql
new file mode 100644
index 0000000..4e32db7
--- /dev/null
+++ b/internal/db/migrations/064_users_forum_pref.down.sql
@@ -0,0 +1,5 @@
+-- Reverse t-paliad-157 / m/paliad#15: drops the persisted
+-- Fristenrechner inbox-channel preference column.
+
+ALTER TABLE paliad.users DROP CONSTRAINT IF EXISTS users_forum_pref_check;
+ALTER TABLE paliad.users DROP COLUMN IF EXISTS forum_pref;
diff --git a/internal/db/migrations/064_users_forum_pref.up.sql b/internal/db/migrations/064_users_forum_pref.up.sql
new file mode 100644
index 0000000..6b1b094
--- /dev/null
+++ b/internal/db/migrations/064_users_forum_pref.up.sql
@@ -0,0 +1,32 @@
+-- t-paliad-157 / m/paliad#15: persisted Fristenrechner inbox-channel
+-- preference.
+--
+-- Stores the user's typical inbox channel (cms = UPC, bea = national-DE,
+-- posteingang = national-DE — slower channel, same set of forums) so
+-- /tools/fristenrechner can pre-narrow the proceeding picker without
+-- re-asking on every visit. The chip on the page persists changes here
+-- via the existing PATCH /api/me endpoint. URL ?inbox= overrides for
+-- the current visit so a colleague can share a CMS-narrowed link
+-- without flipping anyone's saved preference.
+--
+-- The 3-value CHECK keeps the schema honest while leaving room to add
+-- epa / dpma channels later (the Fristenrechner already supports those
+-- forums via the fine-grained B2 chips; the inbox-channel chip starts
+-- with the channels m named explicitly in t-paliad-157).
+--
+-- NULL = no preference, picker shows everything. Default for existing
+-- rows.
+
+ALTER TABLE paliad.users
+    ADD COLUMN forum_pref text;
+
+ALTER TABLE paliad.users
+    ADD CONSTRAINT users_forum_pref_check
+    CHECK (forum_pref IS NULL OR forum_pref IN ('cms', 'bea', 'posteingang'));
+
+COMMENT ON COLUMN paliad.users.forum_pref IS
+    'Persisted Fristenrechner inbox-channel preference (#15). '
+    'cms = UPC; bea = national-DE; posteingang = national-DE (slower '
+    'channel, same forums). NULL = no preference (picker shows '
+    'everything). URL ?inbox= overrides for the current visit. Set via '
+    'PATCH /api/me.';
diff --git a/internal/models/models.go b/internal/models/models.go
index 4f0d81a..6053f39 100644
--- a/internal/models/models.go
+++ b/internal/models/models.go
@@ -56,8 +56,13 @@ type User struct {
 	// for overdue / DRINGEND mail. NULL means "fall back to global_admins".
 	// Settings UI dropdown shipped 2026-04-29 (t-paliad-066).
 	EscalationContactID *uuid.UUID `db:"escalation_contact_id" json:"escalation_contact_id,omitempty"`
-	CreatedAt           time.Time  `db:"created_at"            json:"created_at"`
-	UpdatedAt           time.Time  `db:"updated_at"            json:"updated_at"`
+	// ForumPref is the user's persisted Fristenrechner inbox-channel
+	// preference (#15): "cms" → UPC; "bea" → national-DE;
+	// "posteingang" → national-DE (slower channel, same forums). NULL =
+	// no preference. URL ?inbox= overrides per-visit.
+	ForumPref *string   `db:"forum_pref" json:"forum_pref,omitempty"`
+	CreatedAt time.Time `db:"created_at" json:"created_at"`
+	UpdatedAt time.Time `db:"updated_at" json:"updated_at"`
 }
 
 // Project is one node in the paliad.projects tree. Visibility is team-based
diff --git a/internal/services/user_service.go b/internal/services/user_service.go
index b35ee4b..57858a9 100644
--- a/internal/services/user_service.go
+++ b/internal/services/user_service.go
@@ -73,6 +73,7 @@ const userColumns = `id, email, display_name, office, additional_offices, practi
 	reminder_timezone,
 	reminder_warning_offset_days,
 	escalation_contact_id,
+	forum_pref,
 	created_at, updated_at`
 
 // GetByID returns the user row, or (nil, nil) if the user hasn't completed
@@ -283,6 +284,10 @@ type UpdateProfileInput struct {
 	// encode the clear signal as "" rather than juggling JSON null / missing
 	// semantics).
 	EscalationContactID *string `json:"escalation_contact_id,omitempty"`
+	// ForumPref is the persisted Fristenrechner inbox-channel preference
+	// (#15). Allowed values: "cms" | "bea" | "posteingang". Empty string
+	// clears the preference (NULL in the DB). nil = don't touch.
+	ForumPref *string `json:"forum_pref,omitempty"`
 }
 
 // UpdateProfile mutates the paliad.users row for the authenticated user.
@@ -409,6 +414,21 @@ func (s *UserService) UpdateProfile(ctx context.Context, id uuid.UUID, input Upd
 		args = append(args, val)
 		i++
 	}
+	if input.ForumPref != nil {
+		raw := strings.TrimSpace(*input.ForumPref)
+		var val any
+		if raw == "" {
+			val = nil
+		} else {
+			if !isValidForumPref(raw) {
+				return nil, fmt.Errorf("invalid forum_pref %q (expected cms, bea, or posteingang)", raw)
+			}
+			val = raw
+		}
+		sets = append(sets, fmt.Sprintf("forum_pref = $%d", i))
+		args = append(args, val)
+		i++
+	}
 
 	if len(sets) == 0 {
 		// No-op PATCH is legal — just return the current row.
@@ -832,6 +852,27 @@ func (s *UserService) AdminDeleteUser(ctx context.Context, id uuid.UUID) error {
 	return nil
 }
 
+// ForumPref* are the allowed values of paliad.users.forum_pref (#15).
+// CMS = UPC; beA / Posteingang = national-DE (Posteingang is the slower
+// channel for the same forums). Empty string clears the preference.
+const (
+	ForumPrefCMS         = "cms"
+	ForumPrefBeA         = "bea"
+	ForumPrefPosteingang = "posteingang"
+)
+
+// isValidForumPref returns true when v is one of the allowed channel
+// slugs. The DB CHECK constraint mirrors this list; we validate in the
+// service layer so callers see a typed error instead of a raw pq
+// constraint violation.
+func isValidForumPref(v string) bool {
+	switch v {
+	case ForumPrefCMS, ForumPrefBeA, ForumPrefPosteingang:
+		return true
+	}
+	return false
+}
+
 // UnonboardedAuthUser is one row in auth.users that has no matching
 // paliad.users entry — i.e. the user logged in once via Supabase but never
 // completed onboarding. Surfaced to admins so they can bulk-add real