fix(ui): combobox viewport flip, multi-user picker, merge data migration

- fix(ui): combobox dropdown flips above input near viewport bottom using
  bottom-anchored positioning so filtered items shrink upward correctly
- fix(ui): add onSelect callback to Combobox for commit-only events,
  preventing keystroke-adds-badge bug in multi-select mode
- feat(ui): MultiUserPicker shared component for allow/deny user fields
- fix(ui): migrate channel allow_from textarea, team allowed/denied users,
  and config allow_from input to MultiUserPicker with unified search
- fix(ui): remove dead getKnownUsers from use-teams hook
- feat: migrate per-user data on contact merge (context files, overrides,
  profiles, memory) with DO NOTHING conflict strategy — canonical tenant
  user data always wins over newly merged contact data

internal/http/contact_merge_handlers.go

@@ -50,6 +50,7 @@ func (h *ChannelInstancesHandler) handleMergeContacts(w http.ResponseWriter, r *
 	}
 
 	var targetID uuid.UUID
+	var targetUserID string // tenant_user.user_id string for context file migration
 
 	if hasTU {
 		// Link to existing tenant_user — verify same tenant.
@@ -63,6 +64,7 @@ func (h *ChannelInstancesHandler) handleMergeContacts(w http.ResponseWriter, r *
 			return
 		}
 		targetID = tu.ID
+		targetUserID = tu.UserID
 	} else {
 		// Create new tenant_user.
 		userID := body.CreateUser.UserID
@@ -82,6 +84,7 @@ func (h *ChannelInstancesHandler) handleMergeContacts(w http.ResponseWriter, r *
 			return
 		}
 		targetID = tu.ID
+		targetUserID = tu.UserID
 	}
 
 	if err := h.contactStore.MergeContacts(r.Context(), body.ContactIDs, targetID); err != nil {
@@ -90,6 +93,9 @@ func (h *ChannelInstancesHandler) handleMergeContacts(w http.ResponseWriter, r *
 		return
 	}
 
+	// Migrate user_context_files from old sender_ids to new tenant_user_id.
+	h.migrateContextFilesOnMerge(r.Context(), body.ContactIDs, targetUserID)
+
 	emitAudit(h.msgBus, r, "contacts.merged", "tenant_user", targetID.String())
 	writeJSON(w, http.StatusOK, map[string]any{
 		"merged_id":    targetID,
@@ -182,6 +188,30 @@ func (h *ChannelInstancesHandler) handleListTenantUsers(w http.ResponseWriter, r
 	writeJSON(w, http.StatusOK, map[string]any{"users": users})
 }
 
+// migrateContextFilesOnMerge moves user_context_files from old sender_ids to the new tenant_user_id.
+// Best-effort: log errors but don't fail the merge.
+func (h *ChannelInstancesHandler) migrateContextFilesOnMerge(ctx context.Context, contactIDs []uuid.UUID, newUserID string) {
+	// Batch-fetch sender_ids from merged contacts in one query.
+	oldUserIDs, err := h.contactStore.GetSenderIDsByContactIDs(ctx, contactIDs)
+	if err != nil {
+		slog.Warn("contacts.merge.get_sender_ids", "error", err)
+		return
+	}
+	// Filter out the target user_id itself (no self-migration needed).
+	filtered := oldUserIDs[:0]
+	for _, id := range oldUserIDs {
+		if id != newUserID {
+			filtered = append(filtered, id)
+		}
+	}
+	if len(filtered) == 0 {
+		return
+	}
+	if err := h.agentStore.MigrateUserDataOnMerge(ctx, filtered, newUserID); err != nil {
+		slog.Warn("contacts.merge.migrate_context_files", "error", err, "old_ids", filtered, "new_id", newUserID)
+	}
+}
+
 // deriveUserIDFromContacts returns the first contact's username or sender_id as fallback user_id.
 func (h *ChannelInstancesHandler) deriveUserIDFromContacts(ctx context.Context, contactIDs []uuid.UUID) string {
 	if len(contactIDs) == 0 {

internal/store/agent_store.go

@@ -505,6 +505,10 @@ type AgentContextStore interface {
 	GetUserContextFiles(ctx context.Context, agentID uuid.UUID, userID string) ([]UserContextFileData, error)
 	SetUserContextFile(ctx context.Context, agentID uuid.UUID, userID, fileName, content string) error
 	DeleteUserContextFile(ctx context.Context, agentID uuid.UUID, userID, fileName string) error
+	// MigrateUserDataOnMerge moves per-user data from oldUserIDs to newUserID when contacts are merged.
+	// Covers: user_context_files, user_agent_overrides, user_agent_profiles, memory_documents/chunks.
+	// On conflict, keeps the newest by updated_at. Best-effort per table.
+	MigrateUserDataOnMerge(ctx context.Context, oldUserIDs []string, newUserID string) error
 	GetUserOverride(ctx context.Context, agentID uuid.UUID, userID string) (*UserAgentOverrideData, error)
 	SetUserOverride(ctx context.Context, override *UserAgentOverrideData) error
 }

internal/store/contact_store.go

@@ -53,6 +53,9 @@ type ContactStore interface {
 	// GetContactByID returns a single contact by primary key. Tenant-scoped via context.
 	GetContactByID(ctx context.Context, id uuid.UUID) (*ChannelContact, error)
 
+	// GetSenderIDsByContactIDs returns sender_id strings for the given contact UUIDs in one query.
+	GetSenderIDsByContactIDs(ctx context.Context, contactIDs []uuid.UUID) ([]string, error)
+
 	// MergeContacts sets merged_id = tenantUserID on all given contact IDs,
 	// linking them to a tenant_users identity. Tenant-scoped via context.
 	MergeContacts(ctx context.Context, contactIDs []uuid.UUID, tenantUserID uuid.UUID) error

internal/store/pg/agents_context.go

@@ -5,7 +5,10 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
+	"fmt"
+	"log/slog"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -123,6 +126,89 @@ func (s *PGAgentStore) DeleteUserContextFile(ctx context.Context, agentID uuid.U
 	return err
 }
 
+func (s *PGAgentStore) MigrateUserDataOnMerge(ctx context.Context, oldUserIDs []string, newUserID string) error {
+	if len(oldUserIDs) == 0 {
+		return nil
+	}
+	tClause, tArgs, _, err := scopeClause(ctx, len(oldUserIDs)+2)
+	if err != nil {
+		return err
+	}
+
+	placeholders := make([]string, len(oldUserIDs))
+	baseArgs := make([]any, 0, len(oldUserIDs)+1+len(tArgs))
+	for i, id := range oldUserIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		baseArgs = append(baseArgs, id)
+	}
+	inClause := strings.Join(placeholders, ",")
+	newP := fmt.Sprintf("$%d", len(oldUserIDs)+1)
+	baseArgs = append(baseArgs, newUserID)
+	baseArgs = append(baseArgs, tArgs...)
+
+	// Args for delete (no newUserID param needed).
+	delArgs := make([]any, len(oldUserIDs))
+	copy(delArgs, baseArgs[:len(oldUserIDs)])
+	delArgs = append(delArgs, tArgs...)
+
+	// Helper: migrate + delete for one table. DO NOTHING on conflict —
+	// existing tenant user data always wins (canonical identity).
+	migrate := func(insertQ, deleteQ string) {
+		if _, err := s.db.ExecContext(ctx, insertQ, baseArgs...); err != nil {
+			slog.Warn("merge.migrate", "error", err)
+		}
+		if _, err := s.db.ExecContext(ctx, deleteQ, delArgs...); err != nil {
+			slog.Warn("merge.cleanup", "error", err)
+		}
+	}
+
+	// 1. user_context_files: UNIQUE(agent_id, user_id, file_name)
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_context_files (id, agent_id, user_id, file_name, content, updated_at, tenant_id)
+			SELECT gen_random_uuid(), agent_id, %s, file_name, content, updated_at, tenant_id
+			FROM user_context_files WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id, file_name) DO NOTHING`, newP, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_context_files WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 2. user_agent_overrides: UNIQUE(agent_id, user_id)
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_agent_overrides (id, agent_id, user_id, provider, model, settings, created_at, updated_at, tenant_id)
+			SELECT gen_random_uuid(), agent_id, %s, provider, model, settings, created_at, updated_at, tenant_id
+			FROM user_agent_overrides WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id) DO NOTHING`, newP, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_agent_overrides WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 3. user_agent_profiles: PK(agent_id, user_id)
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_agent_profiles (agent_id, user_id, workspace, first_seen_at, last_seen_at, metadata, tenant_id)
+			SELECT agent_id, %s, workspace, first_seen_at, last_seen_at, metadata, tenant_id
+			FROM user_agent_profiles WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id) DO NOTHING`, newP, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_agent_profiles WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 4. memory_documents: UNIQUE(agent_id, COALESCE(user_id,''), path)
+	migrate(
+		fmt.Sprintf(`INSERT INTO memory_documents (id, agent_id, user_id, path, content, hash, updated_at, created_at, tenant_id)
+			SELECT gen_random_uuid(), agent_id, %s, path, content, hash, updated_at, created_at, tenant_id
+			FROM memory_documents WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, COALESCE(user_id,''), path) DO NOTHING`, newP, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM memory_documents WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 5. memory_chunks: FK on document_id — cascade from memory_documents delete handles this.
+	// But orphan chunks (where document was already migrated) need cleanup.
+	// Simply re-point remaining chunks whose document still has old user_id.
+	repoint := fmt.Sprintf(`UPDATE memory_chunks SET user_id = %s WHERE user_id IN (%s)%s`, newP, inClause, tClause)
+	if _, err := s.db.ExecContext(ctx, repoint, baseArgs...); err != nil {
+		slog.Warn("merge.migrate_chunks", "error", err)
+	}
+
+	return nil
+}
+
 // --- User-Agent Profiles ---
 
 func (s *PGAgentStore) GetOrCreateUserProfile(ctx context.Context, agentID uuid.UUID, userID, workspace, channel string) (bool, string, error) {

internal/store/pg/channel_contacts.go

@@ -194,6 +194,36 @@ func (s *PGContactStore) GetContactByID(ctx context.Context, id uuid.UUID) (*sto
 	return &c, nil
 }
 
+func (s *PGContactStore) GetSenderIDsByContactIDs(ctx context.Context, contactIDs []uuid.UUID) ([]string, error) {
+	if len(contactIDs) == 0 {
+		return nil, nil
+	}
+	tid := store.TenantIDFromContext(ctx)
+	placeholders := make([]string, len(contactIDs))
+	args := make([]any, len(contactIDs)+1)
+	for i, id := range contactIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		args[i] = id
+	}
+	args[len(contactIDs)] = tid
+	q := fmt.Sprintf("SELECT sender_id FROM channel_contacts WHERE id IN (%s) AND tenant_id = $%d",
+		strings.Join(placeholders, ","), len(contactIDs)+1)
+	rows, err := s.db.QueryContext(ctx, q, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var result []string
+	for rows.Next() {
+		var sid string
+		if err := rows.Scan(&sid); err != nil {
+			return nil, err
+		}
+		result = append(result, sid)
+	}
+	return result, rows.Err()
+}
+
 func (s *PGContactStore) MergeContacts(ctx context.Context, contactIDs []uuid.UUID, tenantUserID uuid.UUID) error {
 	if len(contactIDs) == 0 {
 		return nil

internal/store/sqlitestore/agents_context.go

@@ -7,7 +7,10 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
+	"fmt"
+	"log/slog"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -133,6 +136,86 @@ func (s *SQLiteAgentStore) DeleteUserContextFile(ctx context.Context, agentID uu
 	return err
 }
 
+func (s *SQLiteAgentStore) MigrateUserDataOnMerge(ctx context.Context, oldUserIDs []string, newUserID string) error {
+	if len(oldUserIDs) == 0 {
+		return nil
+	}
+	tClause, tArgs, err := scopeClause(ctx)
+	if err != nil {
+		return err
+	}
+
+	placeholders := make([]string, len(oldUserIDs))
+	baseArgs := make([]any, 0, len(oldUserIDs)+1+len(tArgs))
+	for i, id := range oldUserIDs {
+		placeholders[i] = "?"
+		baseArgs = append(baseArgs, id)
+	}
+	inClause := strings.Join(placeholders, ",")
+	baseArgs = append(baseArgs, newUserID)
+	baseArgs = append(baseArgs, tArgs...)
+
+	delArgs := make([]any, len(oldUserIDs))
+	copy(delArgs, baseArgs[:len(oldUserIDs)])
+	delArgs = append(delArgs, tArgs...)
+
+	uuid := `lower(hex(randomblob(4))||'-'||hex(randomblob(2))||'-'||hex(randomblob(2))||'-'||hex(randomblob(2))||'-'||hex(randomblob(6)))`
+
+	// DO NOTHING on conflict — existing tenant user data always wins.
+	migrate := func(insertQ, deleteQ string) {
+		if _, err := s.db.ExecContext(ctx, insertQ, baseArgs...); err != nil {
+			slog.Warn("merge.migrate", "error", err)
+		}
+		if _, err := s.db.ExecContext(ctx, deleteQ, delArgs...); err != nil {
+			slog.Warn("merge.cleanup", "error", err)
+		}
+	}
+
+	// 1. user_context_files
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_context_files (id, agent_id, user_id, file_name, content, updated_at, tenant_id)
+			SELECT %s, agent_id, ?, file_name, content, updated_at, tenant_id
+			FROM user_context_files WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id, file_name) DO NOTHING`, uuid, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_context_files WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 2. user_agent_overrides
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_agent_overrides (id, agent_id, user_id, provider, model, settings, created_at, updated_at, tenant_id)
+			SELECT %s, agent_id, ?, provider, model, settings, created_at, updated_at, tenant_id
+			FROM user_agent_overrides WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id) DO NOTHING`, uuid, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_agent_overrides WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 3. user_agent_profiles
+	migrate(
+		fmt.Sprintf(`INSERT INTO user_agent_profiles (agent_id, user_id, workspace, first_seen_at, last_seen_at, metadata, tenant_id)
+			SELECT agent_id, ?, workspace, first_seen_at, last_seen_at, metadata, tenant_id
+			FROM user_agent_profiles WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, user_id) DO NOTHING`, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM user_agent_profiles WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 4. memory_documents
+	migrate(
+		fmt.Sprintf(`INSERT INTO memory_documents (id, agent_id, user_id, path, content, hash, updated_at, created_at, tenant_id)
+			SELECT %s, agent_id, ?, path, content, hash, updated_at, created_at, tenant_id
+			FROM memory_documents WHERE user_id IN (%s)%s
+			ON CONFLICT (agent_id, COALESCE(user_id,''), path) DO NOTHING`, uuid, inClause, tClause),
+		fmt.Sprintf(`DELETE FROM memory_documents WHERE user_id IN (%s)%s`, inClause, tClause),
+	)
+
+	// 5. memory_chunks: re-point remaining chunks.
+	repoint := fmt.Sprintf(`UPDATE memory_chunks SET user_id = ? WHERE user_id IN (%s)%s`, inClause, tClause)
+	if _, err := s.db.ExecContext(ctx, repoint, baseArgs...); err != nil {
+		slog.Warn("merge.migrate_chunks", "error", err)
+	}
+
+	return nil
+}
+
 // --- User-Agent Profiles ---
 
 // GetOrCreateUserProfile upserts a user profile and returns (isNew, effectiveWorkspace, error).

internal/store/sqlitestore/contacts.go

@@ -191,6 +191,36 @@ func (s *SQLiteContactStore) GetContactByID(ctx context.Context, id uuid.UUID) (
 	return &c, nil
 }
 
+func (s *SQLiteContactStore) GetSenderIDsByContactIDs(ctx context.Context, contactIDs []uuid.UUID) ([]string, error) {
+	if len(contactIDs) == 0 {
+		return nil, nil
+	}
+	tid := store.TenantIDFromContext(ctx)
+	placeholders := make([]string, len(contactIDs))
+	args := make([]any, len(contactIDs)+1)
+	for i, id := range contactIDs {
+		placeholders[i] = "?"
+		args[i] = id
+	}
+	args[len(contactIDs)] = tid
+	q := fmt.Sprintf("SELECT sender_id FROM channel_contacts WHERE id IN (%s) AND tenant_id = ?",
+		strings.Join(placeholders, ","))
+	rows, err := s.db.QueryContext(ctx, q, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var result []string
+	for rows.Next() {
+		var sid string
+		if err := rows.Scan(&sid); err != nil {
+			return nil, err
+		}
+		result = append(result, sid)
+	}
+	return result, rows.Err()
+}
+
 func (s *SQLiteContactStore) MergeContacts(ctx context.Context, contactIDs []uuid.UUID, tenantUserID uuid.UUID) error {
 	if len(contactIDs) == 0 {
 		return nil

ui/web/src/components/shared/multi-user-picker.tsx

@@ -0,0 +1,76 @@
+import { useState } from "react";
+import { X } from "lucide-react";
+import { Badge } from "@/components/ui/badge";
+import { UserPickerCombobox } from "./user-picker-combobox";
+
+interface MultiUserPickerProps {
+  value: string[];
+  onChange: (values: string[]) => void;
+  placeholder?: string;
+  /** Filter by source: "contact" | "tenant_user" | undefined (both). */
+  source?: "contact" | "tenant_user";
+  /** Filter contacts by peer_kind. */
+  peerKind?: "direct" | "group";
+  /** Allow typing custom values not in the list. Default true. */
+  allowCustom?: boolean;
+  /** Render dropdown into a portal container (useful inside dialogs). */
+  portalContainer?: React.RefObject<HTMLElement | null>;
+}
+
+/**
+ * Multi-select user picker: search + select → badge list.
+ * Wraps UserPickerCombobox for multi-value fields (allow_from, deny lists).
+ *
+ * Uses `onSelect` (fires on dropdown click / custom commit) instead of
+ * `onChange` (fires on every keystroke) to avoid adding partial text.
+ */
+export function MultiUserPicker({
+  value,
+  onChange,
+  placeholder,
+  source,
+  peerKind,
+  allowCustom = true,
+  portalContainer,
+}: MultiUserPickerProps) {
+  const [inputValue, setInputValue] = useState("");
+
+  const handleCommit = (val: string) => {
+    const trimmed = val.trim();
+    if (trimmed && !value.includes(trimmed)) {
+      onChange([...value, trimmed]);
+    }
+    setInputValue("");
+  };
+
+  return (
+    <div className="space-y-2">
+      <UserPickerCombobox
+        value={inputValue}
+        onChange={setInputValue}
+        onSelect={handleCommit}
+        placeholder={placeholder}
+        source={source}
+        peerKind={peerKind}
+        allowCustom={allowCustom}
+        portalContainer={portalContainer}
+      />
+      {value.length > 0 && (
+        <div className="flex flex-wrap gap-1.5">
+          {value.map((id) => (
+            <Badge key={id} variant="secondary" className="gap-1 pr-1">
+              {id}
+              <button
+                type="button"
+                onClick={() => onChange(value.filter((v) => v !== id))}
+                className="relative ml-0.5 cursor-pointer rounded-full p-0.5 hover:bg-muted after:absolute after:-inset-2 after:content-[''] md:after:hidden"
+              >
+                <X className="h-3 w-3" />
+              </button>
+            </Badge>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

ui/web/src/components/shared/user-picker-combobox.tsx

@@ -4,6 +4,8 @@ import { useUserPicker } from "@/hooks/use-user-picker";
 interface UserPickerComboboxProps {
   value: string;
   onChange: (value: string) => void;
+  /** Fires only on dropdown item click or custom value commit (not keystrokes). */
+  onSelect?: (value: string) => void;
   placeholder?: string;
   className?: string;
   /** Filter contacts by peer_kind: "direct" | "group" | undefined (all). */
@@ -31,6 +33,7 @@ interface UserPickerComboboxProps {
 export function UserPickerCombobox({
   value,
   onChange,
+  onSelect,
   placeholder,
   className,
   peerKind,
@@ -44,6 +47,7 @@ export function UserPickerCombobox({
     <Combobox
       value={value}
       onChange={onChange}
+      onSelect={onSelect}
       options={options}
       placeholder={placeholder}
       className={className}

ui/web/src/components/ui/combobox.tsx

@@ -11,6 +11,9 @@ export interface ComboboxOption {
 interface ComboboxProps {
   value: string;
   onChange: (value: string) => void;
+  /** Fires only on dropdown item click or custom value commit (not on keystrokes).
+   *  Use this for multi-select wrappers that need to distinguish typing from selection. */
+  onSelect?: (value: string) => void;
   options: ComboboxOption[];
   placeholder?: string;
   className?: string;
@@ -25,6 +28,7 @@ interface ComboboxProps {
 export function Combobox({
   value,
   onChange,
+  onSelect,
   options,
   placeholder,
   className,
@@ -75,28 +79,62 @@ export function Combobox({
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [portalContainer, open]);
 
-  // Compute dropdown position — always use fixed positioning for portal rendering
+  // Compute dropdown position — flip above input when near viewport bottom.
+  // When flipped up, use `bottom` anchoring so the dropdown grows upward
+  // from the input edge (filtering reduces items without creating a gap).
   React.useLayoutEffect(() => {
     if (!open || !containerRef.current) return;
     const inputRect = containerRef.current.getBoundingClientRect();
+    const DROP_H = 256; // max-h-60 ≈ 240px + border/padding
+    const GAP = 4;
+    const spaceBelow = window.innerHeight - inputRect.bottom;
+    const flipUp = spaceBelow < DROP_H && inputRect.top > DROP_H;
+
     if (resolvedPortal) {
       const portalRect = resolvedPortal.getBoundingClientRect();
       const scrollTop = resolvedPortal.scrollTop || 0;
       const scrollLeft = resolvedPortal.scrollLeft || 0;
       const left = inputRect.left - portalRect.left + scrollLeft;
       const maxWidth = portalRect.width - (inputRect.left - portalRect.left);
+      const portalRelativeTop = inputRect.top - portalRect.top + scrollTop;
+      const portalFlipUp = spaceBelow < DROP_H && portalRelativeTop > DROP_H;
+      if (portalFlipUp) {
+        // Anchor bottom edge to input top — dropdown grows upward.
+        const portalH = resolvedPortal.scrollHeight || portalRect.height;
+        setDropdownStyle({
+          position: "absolute",
+          bottom: portalH - portalRelativeTop + GAP,
+          left,
+          width: inputRect.width,
+          maxWidth,
+          maxHeight: DROP_H,
+          zIndex: 50,
+        });
+      } else {
+        setDropdownStyle({
+          position: "absolute",
+          top: inputRect.bottom - portalRect.top + scrollTop + GAP,
+          left,
+          width: inputRect.width,
+          maxWidth,
+          zIndex: 50,
+        });
+      }
+    } else if (flipUp) {
+      // Fixed: anchor bottom edge to input top — dropdown grows upward.
+      const bottomFromViewport = window.innerHeight - inputRect.top;
       setDropdownStyle({
-        position: "absolute",
-        top: inputRect.bottom - portalRect.top + scrollTop + 4,
-        left,
+        position: "fixed",
+        bottom: bottomFromViewport + GAP,
+        left: inputRect.left,
         width: inputRect.width,
-        maxWidth,
-        zIndex: 50,
+        maxHeight: DROP_H,
+        zIndex: 9999,
       });
     } else {
       setDropdownStyle({
         position: "fixed",
-        top: inputRect.bottom + 4,
+        top: inputRect.bottom + GAP,
         left: inputRect.left,
         width: inputRect.width,
         zIndex: 9999,
@@ -125,6 +163,7 @@ export function Combobox({
 
   const handleSelect = (val: string) => {
     onChange(val);
+    onSelect?.(val);
     const match = options.find((o) => o.value === val);
     setSearch(match?.label || val);
     setOpen(false);

ui/web/src/pages/channels/channel-fields.tsx

@@ -3,6 +3,7 @@ import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import { Switch } from "@/components/ui/switch";
 import { Textarea } from "@/components/ui/textarea";
+import { MultiUserPicker } from "@/components/shared/multi-user-picker";
 import {
   Select,
   SelectContent,
@@ -274,16 +275,10 @@ function FieldRenderer({
       return (
         <div className="grid gap-1.5">
           <Label htmlFor={id}>{label}</Label>
-          <Textarea
-            id={id}
-            value={Array.isArray(value) ? (value as string[]).join("\n") : ""}
-            onChange={(e) => {
-              const lines = e.target.value.split(/[\n,]/).map((l) => l.trim()).filter(Boolean);
-              onChange(lines.length > 0 ? lines : undefined);
-            }}
+          <MultiUserPicker
+            value={(value as string[]) ?? []}
+            onChange={(v) => onChange(v.length > 0 ? v : undefined)}
             placeholder={field.placeholder ?? t("groupOverrides.fields.allowedUsersPlaceholder")}
-            rows={3}
-            className="font-mono text-sm"
           />
           {help && <p className="text-xs text-muted-foreground">{help}</p>}
         </div>

ui/web/src/pages/config/sections/channels-section.tsx

@@ -8,6 +8,7 @@ import { Switch } from "@/components/ui/switch";
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card";
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
 import { Badge } from "@/components/ui/badge";
+import { MultiUserPicker } from "@/components/shared/multi-user-picker";
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 type ChannelsData = Record<string, any>;
@@ -177,11 +178,11 @@ export function ChannelsSection({ data, onSave, saving }: Props) {
                     {chData.allow_from !== undefined && (
                       <div className="grid gap-1.5">
                         <Label>{t("channels.allowFrom")}</Label>
-                        <Input
-                          value={(chData.allow_from ?? []).join(", ")}
-                          onChange={(e) =>
+                        <MultiUserPicker
+                          value={chData.allow_from ?? []}
+                          onChange={(v) =>
                             updateChannel(ch, {
-                              allow_from: e.target.value.split(",").map((s: string) => s.trim()).filter(Boolean),
+                              allow_from: v.length > 0 ? v : undefined,
                             })
                           }
                           placeholder={t("channels.allowFromPlaceholder")}

ui/web/src/pages/teams/hooks/use-teams.ts

@@ -269,21 +269,10 @@ export function useTeams() {
     [ws],
   );
 
-  const getKnownUsers = useCallback(
-    async (teamId: string): Promise<string[]> => {
-      const res = await ws.call<{ users: string[] }>(
-        Methods.TEAMS_KNOWN_USERS,
-        { teamId },
-      );
-      return res.users ?? [];
-    },
-    [ws],
-  );
-
   return {
     teams, loading, load, createTeam, deleteTeam, getTeam, getTeamTasks, getTeamScopes,
     getTaskDetail, getTaskLight, approveTask, rejectTask, addTaskComment, getTaskComments, getTaskEvents,
     createTask, deleteTask, deleteTasksBulk, assignTask,
-    addMember, removeMember, updateTeamSettings, getKnownUsers,
+    addMember, removeMember, updateTeamSettings,
   };
 }

ui/web/src/pages/teams/team-settings-tab.tsx

@@ -6,6 +6,7 @@ import { Combobox } from "@/components/ui/combobox";
 import { X, Save, Bell, ShieldAlert, Clock, FolderLock, FolderSync, Zap, Bot, Loader2 } from "lucide-react";
 import { useTranslation } from "react-i18next";
 import { CHANNEL_TYPES } from "@/constants/channels";
+import { MultiUserPicker } from "@/components/shared/multi-user-picker";
 import type { TeamData, TeamAccessSettings, TeamNotifyConfig, EscalationMode, EscalationAction } from "@/types/team";
 import { useTeams } from "./hooks/use-teams";
 
@@ -15,6 +16,7 @@ interface TeamSettingsTabProps {
   onSaved: () => void;
 }
 
+/** Generic multi-select with static options (used for channel type selection). */
 function MultiSelect({
   options,
   selected,
@@ -46,7 +48,7 @@ function MultiSelect({
               <button
                 type="button"
                 onClick={() => onChange(selected.filter((s) => s !== id))}
-                className="ml-0.5 rounded-full p-0.5 hover:bg-muted"
+                className="ml-0.5 cursor-pointer rounded-full p-0.5 hover:bg-muted"
               >
                 <X className="h-3 w-3" />
               </button>
@@ -60,8 +62,7 @@ function MultiSelect({
 
 export function TeamSettingsTab({ teamId, team, onSaved }: TeamSettingsTabProps) {
   const { t } = useTranslation("teams");
-  const { updateTeamSettings, getKnownUsers } = useTeams();
-  const [knownUsers, setKnownUsers] = useState<string[]>([]);
+  const { updateTeamSettings } = useTeams();
 
   // Parse initial settings
   const initial = (team.settings ?? {}) as TeamAccessSettings;
@@ -91,11 +92,6 @@ export function TeamSettingsTab({ teamId, team, onSaved }: TeamSettingsTabProps)
 
   const [saving, setSaving] = useState(false);
 
-  // Load known users for combobox
-  useEffect(() => {
-    getKnownUsers(teamId).then(setKnownUsers).catch(() => {});
-  }, [teamId, getKnownUsers]);
-
   // Reset when team changes
   useEffect(() => {
     const s = (team.settings ?? {}) as TeamAccessSettings;
@@ -165,7 +161,6 @@ export function TeamSettingsTab({ teamId, team, onSaved }: TeamSettingsTabProps)
     }
   }, [teamId, allowUserIds, denyUserIds, allowChannels, denyChannels, notifyDispatched, notifyProgress, notifyFailed, notifyCompleted, notifyCommented, notifyNewTask, notifySlowTool, notifyMode, memberRequestsEnabled, memberRequestsAutoDispatch, escalationMode, escalationActions, blockerEscalationEnabled, followupInterval, followupMaxReminders, workspaceScope, updateTeamSettings, onSaved]);
 
-  const userOptions = knownUsers.map((u) => ({ value: u, label: u }));
   const channelOptions = CHANNEL_TYPES.map((c) => ({ value: c.value, label: c.label }));
 
   return (
@@ -407,9 +402,8 @@ export function TeamSettingsTab({ teamId, team, onSaved }: TeamSettingsTabProps)
             <p className="text-xs text-muted-foreground">
               {t("settings.allowedUsersHint")}
             </p>
-            <MultiSelect
-              options={userOptions}
-              selected={allowUserIds}
+            <MultiUserPicker
+              value={allowUserIds}
               onChange={setAllowUserIds}
               placeholder={t("settings.searchUsers")}
             />
@@ -419,9 +413,8 @@ export function TeamSettingsTab({ teamId, team, onSaved }: TeamSettingsTabProps)
             <p className="text-xs text-muted-foreground">
               {t("settings.deniedUsersHint")}
             </p>
-            <MultiSelect
-              options={userOptions}
-              selected={denyUserIds}
+            <MultiUserPicker
+              value={denyUserIds}
               onChange={setDenyUserIds}
               placeholder={t("settings.searchUsers")}
             />