diff --git a/runners/agent-runner/src/ipc-mcp-stdio.ts b/runners/agent-runner/src/ipc-mcp-stdio.ts
index 9cd57f6..8685d6f 100644
--- a/runners/agent-runner/src/ipc-mcp-stdio.ts
+++ b/runners/agent-runner/src/ipc-mcp-stdio.ts
@@ -491,6 +491,62 @@ if (allowGenericScheduling) {
   );
 }
 
+server.tool(
+  'assign_room',
+  `Assign or update a room using room-level settings. Main group only.
+
+This is the room-level replacement for legacy register_group. If folder is omitted, the host generates one automatically.`,
+  {
+    jid: z.string().describe('The chat JID (e.g., "120363336345536173@g.us", "tg:-1001234567890", "dc:1234567890123456")'),
+    name: z.string().describe('Display name for the room'),
+    room_mode: z.enum(['single', 'tribunal']).default('single').describe('single=owner only, tribunal=owner/reviewer roles enabled'),
+    owner_agent_type: z.enum(['claude-code', 'codex']).optional().describe('Preferred owner agent type for the room'),
+    folder: z.string().optional().describe('Optional folder override. If omitted, the host generates one automatically.'),
+    trigger: z.string().optional().describe('Optional canonical trigger label to store for the room'),
+    requires_trigger: z.boolean().optional().describe('Whether direct trigger mention is required'),
+    is_main: z.boolean().optional().describe('Whether this room is the privileged main control room'),
+    work_dir: z.string().optional().describe('Optional working directory override'),
+  },
+  async (args: {
+    jid: string;
+    name: string;
+    room_mode?: 'single' | 'tribunal';
+    owner_agent_type?: 'claude-code' | 'codex';
+    folder?: string;
+    trigger?: string;
+    requires_trigger?: boolean;
+    is_main?: boolean;
+    work_dir?: string;
+  }) => {
+    if (!isMain) {
+      return {
+        content: [{ type: 'text' as const, text: 'Only the main group can assign rooms.' }],
+        isError: true,
+      };
+    }
+
+    const data = {
+      type: 'assign_room',
+      jid: args.jid,
+      name: args.name,
+      room_mode: args.room_mode || 'single',
+      owner_agent_type: args.owner_agent_type,
+      folder: args.folder,
+      trigger: args.trigger,
+      requiresTrigger: args.requires_trigger,
+      isMain: args.is_main,
+      workDir: args.work_dir,
+      timestamp: new Date().toISOString(),
+    };
+
+    writeIpcFile(TASKS_DIR, data);
+
+    return {
+      content: [{ type: 'text' as const, text: `Room "${args.name}" assignment requested.` }],
+    };
+  },
+);
+
 server.tool(
   'register_group',
   `Register a new chat/group so the agent can respond to messages there. Main group only.
@@ -522,7 +578,7 @@ Use available_groups.json to find the JID for a group. The folder name must be c
     writeIpcFile(TASKS_DIR, data);
 
     return {
-      content: [{ type: 'text' as const, text: `Group "${args.name}" registered. It will start receiving messages immediately.` }],
+      content: [{ type: 'text' as const, text: `Group "${args.name}" registration requested.` }],
     };
   },
 );
diff --git a/src/db.test.ts b/src/db.test.ts
index bf2de8e..e56cc10 100644
--- a/src/db.test.ts
+++ b/src/db.test.ts
@@ -7,6 +7,7 @@ import { describe, it, expect, beforeEach } from 'vitest';
 import {
   _initTestDatabase,
   _initTestDatabaseFromFile,
+  assignRoom,
   claimServiceHandoff,
   completeServiceHandoffAndAdvanceTargetCursor,
   createPairedTask,
@@ -774,6 +775,57 @@ describe('registered group isMain', () => {
   });
 });
 
+describe('room assignment writes', () => {
+  it('assigns a single room with an auto-generated folder', () => {
+    const group = assignRoom('tg:-1001', {
+      name: 'Telegram Dev Team',
+      roomMode: 'single',
+      ownerAgentType: 'claude-code',
+    });
+
+    expect(group).toBeDefined();
+    expect(group!.folder).toMatch(/^grp_telegram_/);
+    expect(group!.agentType).toBe('claude-code');
+    expect(getStoredRoomSettings('tg:-1001')).toMatchObject({
+      chatJid: 'tg:-1001',
+      roomMode: 'single',
+      modeSource: 'explicit',
+      name: 'Telegram Dev Team',
+      ownerAgentType: 'claude-code',
+    });
+    expect(getRegisteredAgentTypesForJid('tg:-1001')).toEqual(['claude-code']);
+  });
+
+  it('materializes tribunal capability rows while serving metadata from room_settings', () => {
+    assignRoom('dc:assigned-room', {
+      name: 'Assigned Room',
+      roomMode: 'tribunal',
+      ownerAgentType: 'codex',
+      folder: 'assigned-room',
+    });
+
+    const allGroups = getAllRegisteredGroups();
+    const claudeGroups = getAllRegisteredGroups('claude-code');
+    const codexGroups = getAllRegisteredGroups('codex');
+
+    expect(allGroups['dc:assigned-room']).toMatchObject({
+      name: 'Assigned Room',
+      folder: 'assigned-room',
+      agentType: 'codex',
+    });
+    expect(claudeGroups['dc:assigned-room']).toMatchObject({
+      name: 'Assigned Room',
+      folder: 'assigned-room',
+      agentType: 'claude-code',
+    });
+    expect(codexGroups['dc:assigned-room']).toMatchObject({
+      name: 'Assigned Room',
+      folder: 'assigned-room',
+      agentType: 'codex',
+    });
+  });
+});
+
 describe('paired room registration', () => {
   it('detects when both Claude and Codex are registered on the same jid', () => {
     setRegisteredGroup('dc:123', {
diff --git a/src/db.ts b/src/db.ts
index 706d50e..d34428b 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -59,6 +59,19 @@ export interface StoredRoomSettings {
   workDir?: string;
 }
 
+export interface AssignRoomInput {
+  name: string;
+  roomMode?: RoomMode;
+  ownerAgentType?: AgentType;
+  folder?: string;
+  trigger?: string;
+  requiresTrigger?: boolean;
+  isMain?: boolean;
+  workDir?: string;
+  addedAt?: string;
+  ownerAgentConfig?: RegisteredGroup['agentConfig'];
+}
+
 interface RoomRegistrationSnapshot {
   name: string;
   folder: string;
@@ -69,6 +82,19 @@ interface RoomRegistrationSnapshot {
   workDir: string | null;
 }
 
+interface RegisteredGroupDatabaseRow {
+  jid: string;
+  name: string;
+  folder: string;
+  trigger_pattern: string;
+  added_at: string;
+  agent_config: string | null;
+  requires_trigger: number | null;
+  is_main: number | null;
+  agent_type: string | null;
+  work_dir: string | null;
+}
+
 export interface WorkItem {
   id: number;
   group_folder: string;
@@ -1899,53 +1925,66 @@ export function getLastRespondingAgentType(
 
 // --- Registered group accessors ---
 
+function buildRegisteredGroupFromStoredSettings(
+  database: Database,
+  stored: StoredRoomSettings,
+  requestedAgentType?: AgentType,
+): (RegisteredGroup & { jid: string }) | undefined {
+  const capabilityTypes = collectRegisteredAgentTypes(database, stored.chatJid);
+  const resolvedAgentType = requestedAgentType
+    ? capabilityTypes.includes(requestedAgentType)
+      ? requestedAgentType
+      : undefined
+    : stored.ownerAgentType ||
+      (capabilityTypes.length > 0
+        ? inferOwnerAgentTypeFromRegisteredAgentTypes(capabilityTypes)
+        : undefined);
+
+  if (!resolvedAgentType) return undefined;
+  if (!stored.folder || !isValidGroupFolder(stored.folder)) {
+    logger.warn(
+      { jid: stored.chatJid, folder: stored.folder ?? null },
+      'Skipping stored room with invalid folder',
+    );
+    return undefined;
+  }
+
+  const capabilityMetadata = getRegisteredGroupCapabilityMetadata(
+    database,
+    stored.chatJid,
+    resolvedAgentType,
+  );
+
+  return {
+    jid: stored.chatJid,
+    name: stored.name || stored.chatJid,
+    folder: stored.folder,
+    trigger: stored.trigger || `@${ASSISTANT_NAME}`,
+    added_at:
+      capabilityMetadata?.added_at || new Date(0).toISOString(),
+    agentConfig: capabilityMetadata?.agentConfig,
+    requiresTrigger: stored.requiresTrigger,
+    isMain: stored.isMain ? true : undefined,
+    agentType: resolvedAgentType,
+    workDir: stored.workDir,
+  };
+}
+
 export function getRegisteredGroup(
   jid: string,
   agentType?: string,
 ): (RegisteredGroup & { jid: string }) | undefined {
-  const row = (
-    agentType
-      ? db
-          .prepare(
-            'SELECT * FROM registered_groups WHERE jid = ? AND agent_type = ?',
-          )
-          .get(jid, agentType)
-      : db.prepare('SELECT * FROM registered_groups WHERE jid = ?').get(jid)
-  ) as
-    | {
-        jid: string;
-        name: string;
-        folder: string;
-        trigger_pattern: string;
-        added_at: string;
-        agent_config: string | null;
-        requires_trigger: number | null;
-        is_main: number | null;
-        agent_type: string | null;
-        work_dir: string | null;
-      }
-    | undefined;
-  if (!row) return undefined;
-  if (!isValidGroupFolder(row.folder)) {
-    logger.warn(
-      { jid: row.jid, folder: row.folder },
-      'Skipping registered group with invalid folder',
+  const requestedAgentType = normalizeStoredAgentType(agentType);
+  const stored = getStoredRoomSettingsRowFromDatabase(db, jid);
+  if (stored) {
+    const group = buildRegisteredGroupFromStoredSettings(
+      db,
+      stored,
+      requestedAgentType,
     );
-    return undefined;
+    if (group) return group;
   }
-  return {
-    jid: row.jid,
-    name: row.name,
-    folder: row.folder,
-    trigger: row.trigger_pattern,
-    added_at: row.added_at,
-    agentConfig: row.agent_config ? JSON.parse(row.agent_config) : undefined,
-    requiresTrigger:
-      row.requires_trigger === null ? undefined : row.requires_trigger === 1,
-    isMain: row.is_main === 1 ? true : undefined,
-    agentType: (row.agent_type as RegisteredGroup['agentType']) || undefined,
-    workDir: row.work_dir || undefined,
-  };
+  return getLegacyRegisteredGroup(db, jid, agentType);
 }
 
 export function setRegisteredGroup(jid: string, group: RegisteredGroup): void {
@@ -1978,68 +2017,115 @@ export function setRegisteredGroup(jid: string, group: RegisteredGroup): void {
   tx();
 }
 
+export function assignRoom(
+  chatJid: string,
+  input: AssignRoomInput,
+): (RegisteredGroup & { jid: string }) | undefined {
+  const existing = getStoredRoomSettingsRowFromDatabase(db, chatJid);
+  const roomMode = input.roomMode || existing?.roomMode || 'single';
+  const ownerAgentType =
+    input.ownerAgentType || existing?.ownerAgentType || OWNER_AGENT_TYPE;
+  const folder = resolveAssignedRoomFolder(db, chatJid, input.name, input.folder);
+  const snapshot: RoomRegistrationSnapshot = {
+    name: input.name,
+    folder,
+    triggerPattern:
+      input.trigger || existing?.trigger || `@${ASSISTANT_NAME}`,
+    requiresTrigger: input.requiresTrigger ?? existing?.requiresTrigger ?? true,
+    isMain: input.isMain ?? existing?.isMain ?? false,
+    ownerAgentType,
+    workDir: input.workDir ?? existing?.workDir ?? null,
+  };
+  const now = new Date().toISOString();
+
+  db.transaction(() => {
+    if (existing) {
+      db.prepare(
+        `UPDATE room_settings
+         SET room_mode = ?,
+             mode_source = 'explicit',
+             name = ?,
+             folder = ?,
+             trigger_pattern = ?,
+             requires_trigger = ?,
+             is_main = ?,
+             owner_agent_type = ?,
+             work_dir = ?,
+             updated_at = ?
+         WHERE chat_jid = ?`,
+      ).run(
+        roomMode,
+        snapshot.name,
+        snapshot.folder,
+        snapshot.triggerPattern,
+        snapshot.requiresTrigger ? 1 : 0,
+        snapshot.isMain ? 1 : 0,
+        snapshot.ownerAgentType,
+        snapshot.workDir,
+        now,
+        chatJid,
+      );
+    } else {
+      insertStoredRoomSettings(db, chatJid, roomMode, 'explicit', snapshot);
+    }
+
+    materializeRegisteredGroupsForRoom(
+      db,
+      chatJid,
+      snapshot,
+      roomMode,
+      ownerAgentType,
+      input.ownerAgentConfig,
+      input.addedAt ?? now,
+    );
+  })();
+
+  return getRegisteredGroup(chatJid);
+}
+
 export function updateRegisteredGroupName(jid: string, name: string): void {
+  db.prepare(
+    `UPDATE room_settings
+     SET name = ?, updated_at = ?
+     WHERE chat_jid = ?`,
+  ).run(name, new Date().toISOString(), jid);
   db.prepare('UPDATE registered_groups SET name = ? WHERE jid = ?').run(
     name,
     jid,
   );
-  syncStoredRoomRegistrationSnapshotForJid(jid);
+  if (!getStoredRoomSettingsRowFromDatabase(db, jid)) {
+    syncStoredRoomRegistrationSnapshotForJid(jid);
+  }
 }
 
 export function getAllRegisteredGroups(
   agentTypeFilter?: string,
 ): Record<string, RegisteredGroup> {
-  const rows = (
-    agentTypeFilter
-      ? db
-          .prepare('SELECT * FROM registered_groups WHERE agent_type = ?')
-          .all(agentTypeFilter)
-      : db.prepare('SELECT * FROM registered_groups').all()
-  ) as Array<{
-    jid: string;
-    name: string;
-    folder: string;
-    trigger_pattern: string;
-    added_at: string;
-    agent_config: string | null;
-    requires_trigger: number | null;
-    is_main: number | null;
-    agent_type: string | null;
-    work_dir: string | null;
-  }>;
   const result: Record<string, RegisteredGroup> = {};
-  for (const row of rows) {
-    if (!isValidGroupFolder(row.folder)) {
-      logger.warn(
-        { jid: row.jid, folder: row.folder },
-        'Skipping registered group with invalid folder',
-      );
-      continue;
-    }
-    const group: RegisteredGroup = {
-      name: row.name,
-      folder: row.folder,
-      trigger: row.trigger_pattern,
-      added_at: row.added_at,
-      agentConfig: row.agent_config ? JSON.parse(row.agent_config) : undefined,
-      requiresTrigger:
-        row.requires_trigger === null ? undefined : row.requires_trigger === 1,
-      isMain: row.is_main === 1 ? true : undefined,
-      agentType: (row.agent_type as RegisteredGroup['agentType']) || undefined,
-      workDir: row.work_dir || undefined,
-    };
-    // In unified mode (no agentTypeFilter), when the same JID has both
-    // claude-code and codex rows, prefer the codex entry (owner).
-    const existing = result[row.jid];
-    if (existing && !agentTypeFilter) {
-      if (group.agentType === 'codex') {
-        result[row.jid] = group;
-      }
-      // else keep existing (already codex or first-seen)
-    } else {
-      result[row.jid] = group;
+  const requestedAgentType = normalizeStoredAgentType(agentTypeFilter);
+  const storedRows = getStoredRoomRowsFromDatabase(db);
+
+  for (const stored of storedRows) {
+    const group = buildRegisteredGroupFromStoredSettings(
+      db,
+      stored,
+      requestedAgentType,
+    );
+    if (group) {
+      const { jid, ...rest } = group;
+      result[jid] = rest;
     }
   }
+
+  for (const legacyRow of getLegacyRegisteredGroupRows(db, agentTypeFilter)) {
+    if (result[legacyRow.jid]) continue;
+    const group = parseRegisteredGroupRow(legacyRow);
+    if (group) {
+      const { jid, ...rest } = group;
+      result[jid] = rest;
+    }
+  }
+
   return result;
 }
 
@@ -2107,6 +2193,293 @@ function normalizeStoredAgentType(
     : undefined;
 }
 
+function parseRegisteredGroupRow(
+  row: RegisteredGroupDatabaseRow | undefined,
+): (RegisteredGroup & { jid: string }) | undefined {
+  if (!row) return undefined;
+  if (!isValidGroupFolder(row.folder)) {
+    logger.warn(
+      { jid: row.jid, folder: row.folder },
+      'Skipping registered group with invalid folder',
+    );
+    return undefined;
+  }
+  return {
+    jid: row.jid,
+    name: row.name,
+    folder: row.folder,
+    trigger: row.trigger_pattern,
+    added_at: row.added_at,
+    agentConfig: row.agent_config ? JSON.parse(row.agent_config) : undefined,
+    requiresTrigger:
+      row.requires_trigger === null ? undefined : row.requires_trigger === 1,
+    isMain: row.is_main === 1 ? true : undefined,
+    agentType: normalizeStoredAgentType(row.agent_type),
+    workDir: row.work_dir || undefined,
+  };
+}
+
+function getLegacyRegisteredGroupRows(
+  database: Database,
+  agentTypeFilter?: string,
+): RegisteredGroupDatabaseRow[] {
+  return (
+    agentTypeFilter
+      ? database
+          .prepare('SELECT * FROM registered_groups WHERE agent_type = ?')
+          .all(agentTypeFilter)
+      : database.prepare('SELECT * FROM registered_groups').all()
+  ) as RegisteredGroupDatabaseRow[];
+}
+
+function getLegacyRegisteredGroup(
+  database: Database,
+  jid: string,
+  agentType?: string,
+): (RegisteredGroup & { jid: string }) | undefined {
+  const row = (
+    agentType
+      ? database
+          .prepare(
+            'SELECT * FROM registered_groups WHERE jid = ? AND agent_type = ?',
+          )
+          .get(jid, agentType)
+      : database.prepare('SELECT * FROM registered_groups WHERE jid = ?').get(jid)
+  ) as RegisteredGroupDatabaseRow | undefined;
+  return parseRegisteredGroupRow(row);
+}
+
+function getRegisteredGroupCapabilityMetadata(
+  database: Database,
+  jid: string,
+  preferredAgentType?: AgentType,
+): Pick<RegisteredGroup, 'added_at' | 'agentConfig'> | undefined {
+  const row = (
+    preferredAgentType
+      ? database
+          .prepare(
+            `SELECT added_at, agent_config
+             FROM registered_groups
+             WHERE jid = ? AND agent_type = ?
+             LIMIT 1`,
+          )
+          .get(jid, preferredAgentType)
+      : database
+          .prepare(
+            `SELECT added_at, agent_config
+             FROM registered_groups
+             WHERE jid = ?
+             ORDER BY CASE WHEN agent_type = ? THEN 0 ELSE 1 END, added_at
+             LIMIT 1`,
+          )
+          .get(jid, OWNER_AGENT_TYPE)
+  ) as { added_at: string; agent_config: string | null } | undefined;
+
+  if (!row) return undefined;
+  return {
+    added_at: row.added_at,
+    agentConfig: row.agent_config ? JSON.parse(row.agent_config) : undefined,
+  };
+}
+
+function getStoredRoomRowsFromDatabase(database: Database): StoredRoomSettings[] {
+  return database
+    .prepare(
+      `SELECT chat_jid
+       FROM room_settings
+       ORDER BY chat_jid`,
+    )
+    .all()
+    .map((row) =>
+      getStoredRoomSettingsRowFromDatabase(database, (row as { chat_jid: string }).chat_jid),
+    )
+    .filter((row): row is StoredRoomSettings => Boolean(row));
+}
+
+function detectChannelPrefixForFolder(chatJid: string): string {
+  if (chatJid.startsWith('dc:')) return 'discord';
+  if (chatJid.startsWith('tg:')) return 'telegram';
+  return 'whatsapp';
+}
+
+function slugifyGroupFolderSegment(value: string): string {
+  const slug = value
+    .trim()
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, '-')
+    .replace(/^-+|-+$/g, '')
+    .replace(/-{2,}/g, '-');
+  return slug || 'room';
+}
+
+function collectReservedFolders(
+  database: Database,
+  exceptChatJid?: string,
+): Set<string> {
+  const folders = new Set<string>();
+  const rows = database
+    .prepare(
+      `SELECT folder
+       FROM room_settings
+       WHERE folder IS NOT NULL
+         AND (? IS NULL OR chat_jid != ?)
+       UNION
+       SELECT folder
+       FROM registered_groups
+       WHERE ? IS NULL OR jid != ?`,
+    )
+    .all(exceptChatJid ?? null, exceptChatJid ?? null, exceptChatJid ?? null, exceptChatJid ?? null) as Array<{
+    folder: string | null;
+  }>;
+
+  for (const row of rows) {
+    if (row.folder) folders.add(row.folder);
+  }
+  return folders;
+}
+
+function buildGeneratedRoomFolder(
+  database: Database,
+  chatJid: string,
+  name: string,
+): string {
+  const prefix = detectChannelPrefixForFolder(chatJid);
+  const slug = slugifyGroupFolderSegment(name);
+  const fallback = slugifyGroupFolderSegment(chatJid.replace(/[:@.]/g, '-'));
+  const baseCore = slug || fallback;
+  const maxBaseLength = 64 - (`grp_${prefix}_`.length + 4);
+  const truncatedCore = baseCore.slice(0, Math.max(8, maxBaseLength));
+  const candidateBase = `grp_${prefix}_${truncatedCore}`;
+  const reserved = collectReservedFolders(database, chatJid);
+
+  if (!reserved.has(candidateBase) && isValidGroupFolder(candidateBase)) {
+    return candidateBase;
+  }
+
+  for (let suffix = 2; suffix < 1000; suffix += 1) {
+    const candidate = `${candidateBase.slice(0, Math.max(1, 64 - `${suffix}`.length - 1))}-${suffix}`;
+    if (!reserved.has(candidate) && isValidGroupFolder(candidate)) {
+      return candidate;
+    }
+  }
+
+  throw new Error(`Unable to generate unique group folder for ${chatJid}`);
+}
+
+function resolveAssignedRoomFolder(
+  database: Database,
+  chatJid: string,
+  name: string,
+  explicitFolder?: string,
+): string {
+  const reserved = collectReservedFolders(database, chatJid);
+  if (explicitFolder) {
+    if (!isValidGroupFolder(explicitFolder)) {
+      throw new Error(`Invalid group folder "${explicitFolder}" for JID ${chatJid}`);
+    }
+    if (reserved.has(explicitFolder)) {
+      throw new Error(`Group folder "${explicitFolder}" is already assigned`);
+    }
+    return explicitFolder;
+  }
+
+  const existingFolder = getStoredRoomSettingsRowFromDatabase(database, chatJid)?.folder;
+  if (existingFolder) return existingFolder;
+
+  return buildGeneratedRoomFolder(database, chatJid, name);
+}
+
+function getDesiredRegisteredAgentTypes(
+  roomMode: RoomMode,
+  ownerAgentType: AgentType,
+): AgentType[] {
+  const types = new Set<AgentType>([ownerAgentType]);
+  if (roomMode === 'tribunal') {
+    types.add(REVIEWER_AGENT_TYPE);
+  }
+  return [...types];
+}
+
+function materializeRegisteredGroupsForRoom(
+  database: Database,
+  chatJid: string,
+  snapshot: RoomRegistrationSnapshot,
+  roomMode: RoomMode,
+  ownerAgentType: AgentType,
+  ownerAgentConfig?: RegisteredGroup['agentConfig'],
+  addedAt?: string,
+): void {
+  const now = new Date().toISOString();
+  const desiredTypes = getDesiredRegisteredAgentTypes(roomMode, ownerAgentType);
+  const existingRows = database
+    .prepare(
+      `SELECT agent_type, added_at, agent_config
+       FROM registered_groups
+       WHERE jid = ?`,
+    )
+    .all(chatJid) as Array<{
+    agent_type: string | null;
+    added_at: string;
+    agent_config: string | null;
+  }>;
+  const existingByType = new Map<AgentType, { added_at: string; agent_config: string | null }>();
+  for (const row of existingRows) {
+    const agentType = normalizeStoredAgentType(row.agent_type);
+    if (agentType) {
+      existingByType.set(agentType, row);
+    }
+  }
+
+  for (const agentType of desiredTypes) {
+    const existing = existingByType.get(agentType);
+    const agentConfig =
+      agentType === ownerAgentType
+        ? ownerAgentConfig ??
+          (existing?.agent_config ? JSON.parse(existing.agent_config) : undefined)
+        : existing?.agent_config
+          ? JSON.parse(existing.agent_config)
+          : undefined;
+    const rowAddedAt = existing?.added_at ?? addedAt ?? now;
+
+    database
+      .prepare(
+        `INSERT OR REPLACE INTO registered_groups (
+          jid,
+          name,
+          folder,
+          trigger_pattern,
+          added_at,
+          agent_config,
+          requires_trigger,
+          is_main,
+          agent_type,
+          work_dir
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+      )
+      .run(
+        chatJid,
+        snapshot.name,
+        snapshot.folder,
+        snapshot.triggerPattern,
+        rowAddedAt,
+        agentConfig ? JSON.stringify(agentConfig) : null,
+        snapshot.requiresTrigger ? 1 : 0,
+        snapshot.isMain ? 1 : 0,
+        agentType,
+        snapshot.workDir,
+      );
+  }
+
+  const placeholders = desiredTypes.map(() => '?').join(',');
+  database
+    .prepare(
+      `DELETE FROM registered_groups
+       WHERE jid = ?
+         AND agent_type NOT IN (${placeholders})`,
+    )
+    .run(chatJid, ...desiredTypes);
+}
+
 function getStoredRoomSettingsRowFromDatabase(
   database: Database,
   chatJid: string,
diff --git a/src/index.ts b/src/index.ts
index c1c78ba..081ea01 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -24,15 +24,15 @@ import {
 import { writeGroupsSnapshot } from './agent-runner.js';
 import { listAvailableGroups } from './available-groups.js';
 import {
+  type AssignRoomInput,
+  assignRoom,
   getAllRegisteredGroups,
   getAllSessions,
   getAllTasks,
   getLatestMessageSeqAtOrBefore,
   hasRecentRestartAnnouncement,
-  getRegisteredGroup,
   getRouterState,
   initDatabase,
-  setRegisteredGroup,
   setRouterState,
   deleteAllSessionsForGroup,
   deleteSession,
@@ -217,29 +217,68 @@ function clearSession(
 }
 
 function registerGroup(jid: string, group: RegisteredGroup): void {
+  const assignedGroup = assignRoom(jid, {
+    name: group.name,
+    ownerAgentType: group.agentType,
+    folder: group.folder,
+    trigger: group.trigger,
+    requiresTrigger: group.requiresTrigger,
+    isMain: group.isMain,
+    workDir: group.workDir,
+    addedAt: group.added_at,
+    ownerAgentConfig: group.agentConfig,
+  });
+  if (!assignedGroup) {
+    logger.warn({ jid }, 'Failed to assign room during legacy registration');
+    return;
+  }
+
   let groupDir: string;
   try {
-    groupDir = resolveGroupFolderPath(group.folder);
+    groupDir = resolveGroupFolderPath(assignedGroup.folder);
   } catch (err) {
     logger.warn(
-      { jid, folder: group.folder, err },
+      { jid, folder: assignedGroup.folder, err },
       'Rejecting group registration with invalid folder',
     );
     return;
   }
 
-  registeredGroups[jid] = group;
-  setRegisteredGroup(jid, group);
+  const { jid: _ignoredJid, ...storedGroup } = assignedGroup;
+  registeredGroups[jid] = storedGroup;
 
   // Create group folder
   fs.mkdirSync(path.join(groupDir, 'logs'), { recursive: true });
 
   logger.info(
-    { jid, name: group.name, folder: group.folder },
+    { jid, name: assignedGroup.name, folder: assignedGroup.folder },
     'Group registered',
   );
 }
 
+function assignRoomForIpc(jid: string, input: AssignRoomInput): void {
+  const assignedGroup = assignRoom(jid, input);
+  if (!assignedGroup) {
+    logger.warn({ jid }, 'Failed to assign room from IPC');
+    return;
+  }
+
+  let groupDir: string;
+  try {
+    groupDir = resolveGroupFolderPath(assignedGroup.folder);
+  } catch (err) {
+    logger.warn(
+      { jid, folder: assignedGroup.folder, err },
+      'Rejecting room assignment with invalid folder',
+    );
+    return;
+  }
+
+  const { jid: _ignoredJid, ...storedGroup } = assignedGroup;
+  registeredGroups[jid] = storedGroup;
+  fs.mkdirSync(path.join(groupDir, 'logs'), { recursive: true });
+}
+
 /**
  * Get available groups list for the agent.
  * Returns groups ordered by most recent activity.
@@ -483,6 +522,7 @@ async function main(): Promise<void> {
     nudgeScheduler: nudgeSchedulerLoop,
     registeredGroups: () => registeredGroups,
     registerGroup,
+    assignRoom: assignRoomForIpc,
     syncGroups: async (force: boolean) => {
       await Promise.all(
         channels
diff --git a/src/ipc-auth.test.ts b/src/ipc-auth.test.ts
index c6ec8ec..f8dc7a3 100644
--- a/src/ipc-auth.test.ts
+++ b/src/ipc-auth.test.ts
@@ -1,10 +1,14 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest';
 
+import { ASSISTANT_NAME } from './config.js';
 import {
   _initTestDatabase,
+  assignRoom,
   createTask,
   getAllTasks,
+  getRegisteredAgentTypesForJid,
   getRegisteredGroup,
+  getStoredRoomSettings,
   getTaskById,
   setRegisteredGroup,
 } from './db.js';
@@ -61,6 +65,12 @@ beforeEach(() => {
       setRegisteredGroup(jid, group);
       // Mock the fs.mkdirSync that registerGroup does
     },
+    assignRoom: (jid, room) => {
+      const assigned = assignRoom(jid, room);
+      if (!assigned) return;
+      const { jid: _ignoredJid, ...group } = assigned;
+      groups[jid] = group;
+    },
     syncGroups: async () => {},
     getAvailableGroups: () => [],
     writeGroupsSnapshot: () => {},
@@ -794,19 +804,99 @@ describe('register_group success', () => {
     expect(group!.trigger).toBe('@Andy');
   });
 
-  it('register_group rejects request with missing fields', async () => {
+  it('register_group auto-fills missing folder and trigger for single rooms', async () => {
     await processTaskIpc(
       {
         type: 'register_group',
         jid: 'partial@g.us',
         name: 'Partial',
-        // missing folder and trigger
       },
       'whatsapp_main',
       true,
       deps,
     );
 
-    expect(getRegisteredGroup('partial@g.us')).toBeUndefined();
+    const group = getRegisteredGroup('partial@g.us');
+    expect(group).toBeDefined();
+    expect(group!.folder).toMatch(/^grp_whatsapp_/);
+    expect(group!.trigger).toBe(`@${ASSISTANT_NAME}`);
+    expect(getStoredRoomSettings('partial@g.us')?.roomMode).toBe('single');
+  });
+
+  it('register_group preserves an existing tribunal room mode', async () => {
+    assignRoom('legacy-tribunal@g.us', {
+      name: 'Legacy Tribunal',
+      roomMode: 'tribunal',
+      ownerAgentType: 'codex',
+      folder: 'legacy-tribunal',
+    });
+
+    await processTaskIpc(
+      {
+        type: 'register_group',
+        jid: 'legacy-tribunal@g.us',
+        name: 'Legacy Tribunal Renamed',
+        folder: 'legacy-tribunal',
+      },
+      'whatsapp_main',
+      true,
+      deps,
+    );
+
+    expect(getStoredRoomSettings('legacy-tribunal@g.us')).toMatchObject({
+      chatJid: 'legacy-tribunal@g.us',
+      roomMode: 'tribunal',
+      modeSource: 'explicit',
+      name: 'Legacy Tribunal Renamed',
+    });
+    expect(getRegisteredAgentTypesForJid('legacy-tribunal@g.us').sort()).toEqual([
+      'claude-code',
+      'codex',
+    ]);
+  });
+});
+
+describe('assign_room success', () => {
+  it('main group can assign a tribunal room and materialize capability rows', async () => {
+    await processTaskIpc(
+      {
+        type: 'assign_room',
+        jid: 'tribunal@g.us',
+        name: 'Tribunal Room',
+        room_mode: 'tribunal',
+        owner_agent_type: 'codex',
+      },
+      'whatsapp_main',
+      true,
+      deps,
+    );
+
+    const stored = getStoredRoomSettings('tribunal@g.us');
+    expect(stored).toMatchObject({
+      chatJid: 'tribunal@g.us',
+      roomMode: 'tribunal',
+      modeSource: 'explicit',
+      name: 'Tribunal Room',
+      ownerAgentType: 'codex',
+    });
+    expect(stored?.folder).toMatch(/^grp_whatsapp_/);
+    expect(getRegisteredAgentTypesForJid('tribunal@g.us').sort()).toEqual([
+      'claude-code',
+      'codex',
+    ]);
+  });
+
+  it('assign_room rejects request with missing fields', async () => {
+    await processTaskIpc(
+      {
+        type: 'assign_room',
+        jid: 'broken@g.us',
+      },
+      'whatsapp_main',
+      true,
+      deps,
+    );
+
+    expect(getRegisteredGroup('broken@g.us')).toBeUndefined();
   });
 });
diff --git a/src/ipc.ts b/src/ipc.ts
index 3ac2abc..c8d4605 100644
--- a/src/ipc.ts
+++ b/src/ipc.ts
@@ -7,6 +7,7 @@ import { DATA_DIR, IPC_POLL_INTERVAL, TIMEZONE } from './config.js';
 import { readJsonFile } from './utils.js';
 import { AvailableGroup } from './agent-runner.js';
 import {
+  type AssignRoomInput,
   createTask,
   deleteTask,
   findDuplicateCiWatcher,
@@ -19,13 +20,14 @@ import {
   DEFAULT_WATCH_CI_MAX_DURATION_MS,
   isWatchCiTask,
 } from './task-watch-status.js';
-import { RegisteredGroup } from './types.js';
+import { AgentType, RegisteredGroup, RoomMode } from './types.js';
 
 export interface IpcDeps {
   sendMessage: (jid: string, text: string) => Promise<void>;
   nudgeScheduler?: () => void;
   registeredGroups: () => Record<string, RegisteredGroup>;
   registerGroup: (jid: string, group: RegisteredGroup) => void;
+  assignRoom: (jid: string, room: AssignRoomInput) => void;
   syncGroups: (force: boolean) => Promise<void>;
   getAvailableGroups: () => AvailableGroup[];
   writeGroupsSnapshot: (
@@ -292,12 +294,16 @@ export async function processTaskIpc(
     groupFolder?: string;
     chatJid?: string;
     targetJid?: string;
-    // For register_group
+    // For assign_room / register_group
     jid?: string;
     name?: string;
     folder?: string;
     trigger?: string;
     requiresTrigger?: boolean;
+    room_mode?: RoomMode;
+    owner_agent_type?: AgentType;
+    isMain?: boolean;
+    workDir?: string;
     agentConfig?: RegisteredGroup['agentConfig'];
   },
   sourceGroup: string, // Verified identity from IPC directory
@@ -595,36 +601,74 @@ export async function processTaskIpc(
       }
       break;
 
+    case 'assign_room':
     case 'register_group':
-      // Only main group can register new groups
+      // Only main group can assign/register rooms
       if (!isMain) {
         logger.warn(
-          { sourceGroup },
-          'Unauthorized register_group attempt blocked',
+          { sourceGroup, type: data.type },
+          `Unauthorized ${data.type} attempt blocked`,
         );
         break;
       }
-      if (data.jid && data.name && data.folder && data.trigger) {
-        if (!isValidGroupFolder(data.folder)) {
+      if (data.jid && data.name) {
+        if (data.folder && !isValidGroupFolder(data.folder)) {
           logger.warn(
             { sourceGroup, folder: data.folder },
-            'Invalid register_group request - unsafe folder name',
+            `Invalid ${data.type} request - unsafe folder name`,
           );
           break;
         }
-        // Defense in depth: agent cannot set isMain via IPC
-        deps.registerGroup(data.jid, {
+        if (
+          data.room_mode !== undefined &&
+          data.room_mode !== 'single' &&
+          data.room_mode !== 'tribunal'
+        ) {
+          logger.warn(
+            { sourceGroup, roomMode: data.room_mode },
+            'Invalid assign_room request - unknown room_mode',
+          );
+          break;
+        }
+        if (
+          data.owner_agent_type !== undefined &&
+          data.owner_agent_type !== 'claude-code' &&
+          data.owner_agent_type !== 'codex'
+        ) {
+          logger.warn(
+            { sourceGroup, ownerAgentType: data.owner_agent_type },
+            'Invalid assign_room request - unknown owner_agent_type',
+          );
+          break;
+        }
+
+        if (data.type === 'assign_room') {
+          deps.assignRoom(data.jid, {
+            name: data.name,
+            roomMode: data.room_mode,
+            ownerAgentType: data.owner_agent_type,
+            folder: data.folder,
+            trigger: data.trigger,
+            requiresTrigger: data.requiresTrigger,
+            isMain: data.isMain,
+            workDir: data.workDir,
+          });
+          break;
+        }
+
+        deps.assignRoom(data.jid, {
           name: data.name,
+          ownerAgentType: data.owner_agent_type,
           folder: data.folder,
           trigger: data.trigger,
-          added_at: new Date().toISOString(),
-          agentConfig: data.agentConfig,
           requiresTrigger: data.requiresTrigger,
+          ownerAgentConfig: data.agentConfig,
+          addedAt: new Date().toISOString(),
         });
       } else {
         logger.warn(
           { data },
-          'Invalid register_group request - missing required fields',
+          `Invalid ${data.type} request - missing required fields`,
         );
       }
       break;