diff --git a/src/db.test.ts b/src/db.test.ts
index 81012c4..0db9786 100644
--- a/src/db.test.ts
+++ b/src/db.test.ts
@@ -10,11 +10,14 @@ import {
   createTask,
   createServiceHandoff,
   createProducedWorkItem,
+  clearExplicitRoomMode,
   deleteSession,
   deleteTask,
   getAllChats,
   getAllRegisteredGroups,
   getDueTasks,
+  getEffectiveRoomMode,
+  getExplicitRoomMode,
   getLatestMessageSeqAtOrBefore,
   getLatestPairedTaskForChat,
   getMessagesSinceSeq,
@@ -37,6 +40,7 @@ import {
   setSession,
   setRegisteredGroup,
   setRouterStateForService,
+  setExplicitRoomMode,
   storeChatMetadata,
   storeMessage,
   updatePairedTask,
@@ -801,6 +805,73 @@ describe('paired room registration', () => {
     expect(getRegisteredAgentTypesForJid('dc:solo')).toEqual(['claude-code']);
     expect(isPairedRoomJid('dc:solo')).toBe(false);
   });
+
+  it('falls back to legacy paired-room inference when no explicit room mode exists', () => {
+    setRegisteredGroup('dc:legacy-paired', {
+      name: 'Legacy Paired Claude',
+      folder: 'legacy-paired-claude',
+      trigger: '@Andy',
+      added_at: '2024-01-01T00:00:00.000Z',
+      agentType: 'claude-code',
+    });
+    setRegisteredGroup('dc:legacy-paired', {
+      name: 'Legacy Paired Codex',
+      folder: 'legacy-paired-codex',
+      trigger: '@Codex',
+      added_at: '2024-01-01T00:00:00.000Z',
+      agentType: 'codex',
+    });
+
+    expect(getExplicitRoomMode('dc:legacy-paired')).toBeUndefined();
+    expect(getEffectiveRoomMode('dc:legacy-paired')).toBe(
+      isPairedRoomJid('dc:legacy-paired') ? 'tribunal' : 'single',
+    );
+  });
+
+  it('lets explicit single override dual registration without changing legacy paired inference yet', () => {
+    setRegisteredGroup('dc:explicit-single', {
+      name: 'Explicit Single Claude',
+      folder: 'explicit-single-claude',
+      trigger: '@Andy',
+      added_at: '2024-01-01T00:00:00.000Z',
+      agentType: 'claude-code',
+    });
+    setRegisteredGroup('dc:explicit-single', {
+      name: 'Explicit Single Codex',
+      folder: 'explicit-single-codex',
+      trigger: '@Codex',
+      added_at: '2024-01-01T00:00:00.000Z',
+      agentType: 'codex',
+    });
+
+    setExplicitRoomMode('dc:explicit-single', 'single');
+
+    expect(getExplicitRoomMode('dc:explicit-single')).toBe('single');
+    expect(getEffectiveRoomMode('dc:explicit-single')).toBe('single');
+    expect(isPairedRoomJid('dc:explicit-single')).toBe(true);
+  });
+
+  it('lets explicit tribunal override solo fallback and clears back to inferred mode', () => {
+    setRegisteredGroup('dc:explicit-tribunal', {
+      name: 'Explicit Tribunal Claude',
+      folder: 'explicit-tribunal-claude',
+      trigger: '@Andy',
+      added_at: '2024-01-01T00:00:00.000Z',
+      agentType: 'claude-code',
+    });
+
+    expect(getEffectiveRoomMode('dc:explicit-tribunal')).toBe('single');
+
+    setExplicitRoomMode('dc:explicit-tribunal', 'tribunal');
+
+    expect(getExplicitRoomMode('dc:explicit-tribunal')).toBe('tribunal');
+    expect(getEffectiveRoomMode('dc:explicit-tribunal')).toBe('tribunal');
+
+    clearExplicitRoomMode('dc:explicit-tribunal');
+
+    expect(getExplicitRoomMode('dc:explicit-tribunal')).toBeUndefined();
+    expect(getEffectiveRoomMode('dc:explicit-tribunal')).toBe('single');
+  });
 });
 
 describe('service handoff completion', () => {
diff --git a/src/db.ts b/src/db.ts
index 7b3aeaa..a99dd05 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -26,6 +26,7 @@ import {
   AgentType,
   PairedProject,
   PairedRoomRole,
+  RoomMode,
   PairedTask,
   PairedTurnOutput,
   PairedWorkspace,
@@ -298,6 +299,12 @@ function createSchema(database: Database): void {
       activated_at TEXT,
       reason TEXT
     );
+    CREATE TABLE IF NOT EXISTS room_settings (
+      chat_jid TEXT PRIMARY KEY,
+      room_mode TEXT NOT NULL,
+      updated_at TEXT NOT NULL,
+      CHECK (room_mode IN ('single', 'tribunal'))
+    );
     CREATE TABLE IF NOT EXISTS service_handoffs (
       id INTEGER PRIMARY KEY AUTOINCREMENT,
       chat_jid TEXT NOT NULL,
@@ -1925,6 +1932,52 @@ export function getRegisteredAgentTypesForJid(jid: string): AgentType[] {
   return [...types];
 }
 
+export function inferRoomModeFromRegisteredAgentTypes(
+  agentTypes: readonly AgentType[],
+): RoomMode {
+  const types = new Set(agentTypes);
+  return types.has('claude-code') && types.has('codex')
+    ? 'tribunal'
+    : 'single';
+}
+
+export function inferRoomModeForJid(jid: string): RoomMode {
+  return inferRoomModeFromRegisteredAgentTypes(getRegisteredAgentTypesForJid(jid));
+}
+
+export function getExplicitRoomMode(chatJid: string): RoomMode | undefined {
+  if (!db) return undefined;
+
+  const row = db
+    .prepare(
+      `SELECT room_mode
+       FROM room_settings
+       WHERE chat_jid = ?`,
+    )
+    .get(chatJid) as { room_mode: string | null } | undefined;
+  return row?.room_mode === 'single' || row?.room_mode === 'tribunal'
+    ? row.room_mode
+    : undefined;
+}
+
+export function setExplicitRoomMode(chatJid: string, roomMode: RoomMode): void {
+  db.prepare(
+    `INSERT OR REPLACE INTO room_settings (
+      chat_jid,
+      room_mode,
+      updated_at
+    ) VALUES (?, ?, ?)`,
+  ).run(chatJid, roomMode, new Date().toISOString());
+}
+
+export function clearExplicitRoomMode(chatJid: string): void {
+  db.prepare('DELETE FROM room_settings WHERE chat_jid = ?').run(chatJid);
+}
+
+export function getEffectiveRoomMode(chatJid: string): RoomMode {
+  return getExplicitRoomMode(chatJid) ?? inferRoomModeForJid(chatJid);
+}
+
 export function isPairedRoomJid(jid: string): boolean {
   const types = getRegisteredAgentTypesForJid(jid);
   return types.includes('claude-code') && types.includes('codex');
diff --git a/src/types.ts b/src/types.ts
index e2c392c..1a91729 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -10,6 +10,7 @@ export interface AgentConfig {
 }
 
 export type AgentType = 'claude-code' | 'codex';
+export type RoomMode = 'single' | 'tribunal';
 
 /** Phase of agent output as emitted by the runner. */
 export type AgentOutputPhase =