Add /branch command to fork conversations from any message (#1342, fixes #465)

Fix: gate parent_session_id emission in compact() on truthiness so
sessions without a fork link don't leak parent_session_id: None and
break the v0.50.251 lineage end_reason gating in agent_sessions.py.
The /branch endpoint sets the field on saved forks; everything else
keeps the v0.50.251 sidebar lineage path as the canonical source.

api/models.py

@@ -320,6 +320,7 @@ class Session:
                  compression_anchor_message_key=None,
                  context_length=None, threshold_tokens=None,
                  last_prompt_tokens=None,
+                 parent_session_id: str=None,
                  **kwargs):
         self.session_id = session_id or uuid.uuid4().hex[:12]
         self.title = title
@@ -347,6 +348,7 @@ class Session:
         self.context_length = context_length
         self.threshold_tokens = threshold_tokens
         self.last_prompt_tokens = last_prompt_tokens
+        self.parent_session_id = parent_session_id
         self.is_cli_session = bool(kwargs.get('is_cli_session', False))
         self.source_tag = kwargs.get('source_tag')
         self.session_source = kwargs.get('session_source')
@@ -371,6 +373,7 @@ class Session:
             'pending_user_message', 'pending_attachments', 'pending_started_at',
             'compression_anchor_visible_idx', 'compression_anchor_message_key',
             'context_length', 'threshold_tokens', 'last_prompt_tokens',
+            'parent_session_id',
             'is_cli_session', 'source_tag', 'session_source', 'source_label',
         ]
         meta = {k: getattr(self, k, None) for k in METADATA_FIELDS}
@@ -466,6 +469,9 @@ class Session:
             'context_length': self.context_length,
             'threshold_tokens': self.threshold_tokens,
             'last_prompt_tokens': self.last_prompt_tokens,
+            # Only emit 'parent_session_id' when set (the /branch fork link, #1342).
+            # Sessions without a fork must not leak None — see test_session_lineage_metadata_api.
+            **({'parent_session_id': self.parent_session_id} if self.parent_session_id else {}),
             'active_stream_id': self.active_stream_id,
             'is_cli_session': self.is_cli_session,
             'source_tag': self.source_tag,

api/routes.py

@@ -1702,6 +1702,70 @@ def handle_post(handler, parsed) -> bool:
             handler, {"ok": True, "session": s.compact() | {"messages": s.messages}}
         )
 
+    if parsed.path == "/api/session/branch":
+        # Fork a conversation from any message point (#465).
+        # Accepts: {session_id, keep_count?, title?}
+        #   keep_count: number of messages to copy (0=empty, undefined=full history)
+        #   title: custom title (defaults to "<original title> (fork)")
+        try:
+            require(body, "session_id")
+        except ValueError as e:
+            return bad(handler, str(e))
+        try:
+            source = get_session(body["session_id"])
+        except KeyError:
+            return bad(handler, "Session not found", 404)
+
+        keep_count = body.get("keep_count")
+        if keep_count is not None:
+            try:
+                keep_count = int(keep_count)
+            except (ValueError, TypeError):
+                return bad(handler, "keep_count must be an integer")
+
+        custom_title = body.get("title")
+        if custom_title:
+            custom_title = str(custom_title).strip()[:80] or None
+
+        # Build messages slice
+        source_messages = source.messages or []
+        if keep_count is not None:
+            forked_messages = source_messages[:keep_count]
+        else:
+            forked_messages = list(source_messages)
+
+        # Derive title
+        if custom_title:
+            branch_title = custom_title
+        else:
+            source_title = source.title or "Untitled"
+            branch_title = f"{source_title} (fork)"
+
+        # Create new session inheriting workspace/model/profile
+        branch = Session(
+            workspace=source.workspace,
+            model=source.model,
+            profile=getattr(source, "profile", None),
+            title=branch_title,
+            messages=forked_messages,
+            parent_session_id=source.session_id,
+        )
+        with LOCK:
+            SESSIONS[branch.session_id] = branch
+            SESSIONS.move_to_end(branch.session_id)
+            while len(SESSIONS) > SESSIONS_MAX:
+                SESSIONS.popitem(last=False)
+
+        # Persist only if there are messages (matches new_session pattern)
+        if forked_messages:
+            branch.save()
+
+        return j(handler, {
+            "session_id": branch.session_id,
+            "title": branch_title,
+            "parent_session_id": source.session_id,
+        })
+
     if parsed.path == "/api/session/compress":
         return _handle_session_compress(handler, body)
 

static/commands.js

@@ -30,6 +30,7 @@ const COMMANDS=[
   {name:'voice',     desc:t('cmd_voice'),    fn:cmdVoice,     noEcho:true},
   {name:'reasoning', desc:t('cmd_reasoning'), fn:cmdReasoning, arg:'show|hide|none|minimal|low|medium|high|xhigh', subArgs:['show','hide','none','minimal','low','medium','high','xhigh'], noEcho:true},
   {name:'yolo', desc:t('cmd_yolo'), fn:cmdYolo, noEcho:true},
+  {name:'branch', desc:t('cmd_branch'), fn:cmdBranch, arg:'[name]', noEcho:true},
 ];
 
 const SLASH_SUBARG_SOURCES={
@@ -903,6 +904,49 @@ async function cmdYolo(){
   }catch(e){showToast('YOLO: '+e.message);}
 }
 
+// ── Branch / fork command ──
+// Forks the current conversation into a new session (#465).
+// /branch           → full history copy
+// /branch My Name   → full history copy with custom title
+async function cmdBranch(args){
+  if(!S.session){showToast(t('no_active_session'));return;}
+  const customTitle=(args||'').trim()||null;
+  try{
+    const data=await api('/api/session/branch',{
+      method:'POST',
+      body:JSON.stringify({
+        session_id:S.session.session_id,
+        title:customTitle||undefined,
+      }),
+    });
+    if(data&&data.session_id){
+      await loadSession(data.session_id);
+      if(typeof renderSessionList==='function') await renderSessionList();
+      showToast(t('branch_forked'));
+    }
+  }catch(e){showToast(t('branch_failed')+e.message);}
+}
+
+// ── Fork from a specific message point ──
+// Called from the "Fork from here" button on message hover actions.
+async function forkFromMessage(msgIdx){
+  if(!S.session||S.busy)return;
+  try{
+    const data=await api('/api/session/branch',{
+      method:'POST',
+      body:JSON.stringify({
+        session_id:S.session.session_id,
+        keep_count:msgIdx,
+      }),
+    });
+    if(data&&data.session_id){
+      await loadSession(data.session_id);
+      if(typeof renderSessionList==='function') await renderSessionList();
+      showToast(t('branch_forked'));
+    }
+  }catch(e){showToast(t('branch_failed')+e.message);}
+}
+
 let _skillCommandCache=[];
 let _skillCommandLoadPromise=null;
 let _skillCommandCacheReady=false;

static/i18n.js

@@ -177,9 +177,15 @@ const LOCALES = {
   cmd_undo:'Remove the last exchange',
   cmd_btw:'Ask a side question (ephemeral)',
   cmd_btw_usage:'/btw <question> — ask a side question using session context',
-  cmd_background:'Run a prompt in background',
-  cmd_background_usage:'/background <prompt> — run in parallel without blocking',
-  btw_asking:'Asking side question...',
+   cmd_background:'Run a prompt in background',
+   cmd_background_usage:'/background <prompt> — run in parallel without blocking',
+   cmd_branch:'Fork this conversation into a new session',
+   cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+   branch_forked:'Forked into new session',
+   branch_failed:'Fork failed: ',
+   fork_from_here:'Fork from here',
+   forked_from:'Forked from',
+   btw_asking:'Asking side question...',
   btw_label:'Side question — not in history',
   btw_done:'Side question answered',
   btw_no_answer:'No answer received.',
@@ -587,6 +593,15 @@ const LOCALES = {
     onboarding_error_workspace_required: 'Workspace is required.',
     onboarding_error_model_required: 'Model is required.',
     onboarding_complete: 'Onboarding complete',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: 'Enable or disable the LLM Wiki knowledge base integration.',
+    wiki_status_label: 'Status',
+    wiki_entry_count: '{0} entries',
+    wiki_last_modified: 'Last modified',
+    wiki_not_available: 'N/A',
+    wiki_enabled: 'Wiki enabled',
+    wiki_disabled: 'Wiki disabled',
+    wiki_toggle_failed: 'Failed to toggle wiki: ',
     // panel/runtime i18n
     error_prefix: 'Error: ',
     not_available: 'N/A',
@@ -1482,6 +1497,12 @@ const LOCALES = {
     status_started: 'Started',
     status_tokens: 'Tokens',
     status_unknown: 'Unknown',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     cmd_yolo: 'Переключить YOLO режим (без подтверждений)',
     yolo_no_session: 'Нет активного сеанса',
     yolo_enabled: '⚡ YOLO режим ВКЛ — подтверждения пропущены',
@@ -1537,6 +1558,15 @@ const LOCALES = {
     settings_desc_tts_voice: 'Выберите голос для синтеза речи',
     settings_label_tts_rate: 'Скорость речи',
     settings_label_tts_pitch: 'Тон речи',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: '\u0412\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u0435 \u0438\u043b\u0438 \u043e\u0442\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u0435 \u0438\u043d\u0442\u0435\u0433\u0440\u0430\u0446\u0438\u0438 \u0431\u0430\u0437\u044b \u0437\u043d\u0430\u043d\u0438\u0439 LLM Wiki.',
+    wiki_status_label: '\u0421\u0442\u0430\u0442\u0443\u0441',
+    wiki_entry_count: '{0} \u0437\u0430\u043f\u0438\u0441\u0435\u0439',
+    wiki_last_modified: '\u041f\u043e\u0441\u043b\u0435\u0434\u043d\u0435\u0435 \u0438\u0437\u043c\u0435\u043d\u0435\u043d\u0438\u0435',
+    wiki_not_available: '\u041d\u0435\u0442 \u0434\u0430\u043d\u043d\u044b\u0445',
+    wiki_enabled: '\u0412\u0438\u043a\u0438 \u0432\u043a\u043b\u044e\u0447\u0435\u043d\u0430',
+    wiki_disabled: '\u0412\u0438\u043a\u0438 \u043e\u0442\u043a\u043b\u044e\u0447\u0435\u043d\u0430',
+    wiki_toggle_failed: '\u041d\u0435 \u0443\u0434\u0430\u043b\u043e\u0441\u044c \u043f\u0435\u0440\u0435\u043a\u043b\u044e\u0447\u0438\u0442\u044c \u0432\u0438\u043a\u0438: ',
   },
 
   es: {
@@ -1970,6 +2000,15 @@ const LOCALES = {
     onboarding_error_workspace_required: 'El espacio de trabajo es obligatorio.',
     onboarding_error_model_required: 'El modelo es obligatorio.',
     onboarding_complete: 'Onboarding completado',
+    wiki_panel_title: 'Wiki LLM',
+    wiki_panel_desc: 'Habilitar o deshabilitar la integraci\u00f3n de la base de conocimientos LLM Wiki.',
+    wiki_status_label: 'Estado',
+    wiki_entry_count: '{0} entradas',
+    wiki_last_modified: '\u00daltima modificaci\u00f3n',
+    wiki_not_available: 'N/D',
+    wiki_enabled: 'Wiki habilitado',
+    wiki_disabled: 'Wiki deshabilitado',
+    wiki_toggle_failed: 'Error al cambiar wiki: ',
     // panel/runtime i18n
     error_prefix: 'Error: ',
     not_available: 'N/A',
@@ -2216,6 +2255,12 @@ const LOCALES = {
     status_tokens: 'Tokens',
     status_unknown: 'Unknown',
     cmd_yolo: 'Alternar modo YOLO (saltar aprobaciones)',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     yolo_no_session: 'No hay sesión activa',
     yolo_enabled: '⚡ Modo YOLO activado — aprobaciones omitidas',
     yolo_disabled: 'Modo YOLO desactivado',
@@ -2724,6 +2769,12 @@ const LOCALES = {
     status_unknown: 'Unknown',
     cmd_yolo: 'YOLO-Modus umschalten',
     yolo_no_session: 'Keine aktive Sitzung',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     yolo_enabled: '⚡ YOLO-Modus AN — Genehmigungen übersprungen',
     yolo_disabled: 'YOLO-Modus AUS',
     yolo_pill_label: 'YOLO',
@@ -3007,6 +3058,15 @@ const LOCALES = {
     settings_desc_tts_voice: 'Stimme für Sprachsynthese auswählen',
     settings_label_tts_rate: 'Sprechgeschwindigkeit',
     settings_label_tts_pitch: 'Tonhöhe',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: 'Aktivieren oder Deaktivieren der LLM Wiki-Wissensdatenbankintegration.',
+    wiki_status_label: 'Status',
+    wiki_entry_count: '{0} Eintr\u00e4ge',
+    wiki_last_modified: 'Zuletzt ge\u00e4ndert',
+    wiki_not_available: 'N/V',
+    wiki_enabled: 'Wiki aktiviert',
+    wiki_disabled: 'Wiki deaktiviert',
+    wiki_toggle_failed: 'Wiki-Umschaltung fehlgeschlagen: ',
   },
 
   zh: {
@@ -3438,6 +3498,15 @@ const LOCALES = {
     onboarding_error_workspace_required: '必须填写工作区。',
     onboarding_error_model_required: '必须填写模型。',
     onboarding_complete: '引导完成',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: '\u542f\u7528\u6216\u7981\u7528 LLM Wiki \u77e5\u8bc6\u5e93\u6574\u5408\u3002',
+    wiki_status_label: '\u72b6\u6001',
+    wiki_entry_count: '{0} \u6761\u76ee',
+    wiki_last_modified: '\u6700\u540e\u4fee\u6539',
+    wiki_not_available: '\u65e0\u6570\u636e',
+    wiki_enabled: 'Wiki \u5df2\u542f\u7528',
+    wiki_disabled: 'Wiki \u5df2\u7981\u7528',
+    wiki_toggle_failed: '\u5207\u6362 Wiki \u5931\u8d25: ',
     // panel/runtime i18n
     error_prefix: '错误：',
     not_available: '无',
@@ -3685,6 +3754,12 @@ const LOCALES = {
     cmd_yolo: 'YOLO 模式切换',
     yolo_no_session: '无活动会话',
     yolo_enabled: '⚡ YOLO 模式已开启 — 将跳过所有审批',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     yolo_disabled: 'YOLO 模式已关闭',
     yolo_pill_label: 'YOLO',
     yolo_pill_title_active: 'YOLO 模式激活 — 点击关闭',
@@ -4468,6 +4543,12 @@ const LOCALES = {
     yolo_no_session: '無活動工作階段',
     yolo_enabled: '⚡ YOLO 模式已開啟 — 將跳過所有審批',
     yolo_disabled: 'YOLO 模式已關閉',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     yolo_pill_label: 'YOLO',
     yolo_pill_title_active: 'YOLO 模式激活 — 點擊關閉',
     approval_skip_all: '⚡ 本次工作階段全部跳過',
@@ -4577,6 +4658,15 @@ const LOCALES = {
     settings_desc_tts_voice: '選擇語音合成聲音',
     settings_label_tts_rate: '語速',
     settings_label_tts_pitch: '音調',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: '\u555f\u7528\u6216\u505c\u7528 LLM Wiki \u77e5\u8b58\u5eab\u6574\u5408\u3002',
+    wiki_status_label: '\u72b6\u614b',
+    wiki_entry_count: '{0} \u689d\u76ee',
+    wiki_last_modified: '\u6700\u5f8c\u4fee\u6539',
+    wiki_not_available: '\u7121\u6578\u64da',
+    wiki_enabled: 'Wiki \u5df2\u555f\u7528',
+    wiki_disabled: 'Wiki \u5df2\u505c\u7528',
+    wiki_toggle_failed: '\u5207\u63db Wiki \u5931\u6557: ',
   },
 
 
@@ -4714,6 +4804,12 @@ const LOCALES = {
     btw_done: 'Pergunta lateral respondida',
     btw_no_answer: 'Nenhuma resposta recebida.',
     btw_failed: 'Pergunta lateral falhou: ',
+    cmd_branch:'Fork this conversation into a new session',
+    cmd_branch_usage:'/branch [name] — fork conversation (optionally with a name)',
+    branch_forked:'Forked into new session',
+    branch_failed:'Fork failed: ',
+    fork_from_here:'Fork from here',
+    forked_from:'Forked from',
     bg_running: 'Rodando em background...',
     bg_complete: 'Tarefa de background completa',
     bg_label: 'Resultado de background:',
@@ -5070,6 +5166,15 @@ const LOCALES = {
     onboarding_error_model_required: 'Modelo é necessário.',
     onboarding_complete: 'Configuração completa',
 
+    wiki_panel_title: 'Wiki LLM',
+    wiki_panel_desc: 'Ativar ou desativar a integra\u00e7\u00e3o da base de conhecimento LLM Wiki.',
+    wiki_status_label: 'Estado',
+    wiki_entry_count: '{0} entradas',
+    wiki_last_modified: '\u00daltima modifica\u00e7\u00e3o',
+    wiki_not_available: 'N/D',
+    wiki_enabled: 'Wiki ativado',
+    wiki_disabled: 'Wiki desativado',
+    wiki_toggle_failed: 'Falha ao alternar wiki: ',
     // panel/runtime i18n
     error_prefix: 'Erro: ',
     not_available: 'N/D',
@@ -5782,6 +5887,15 @@ const LOCALES = {
     onboarding_error_workspace_required: 'Workspace is required.',
     onboarding_error_model_required: 'Model is required.',
     onboarding_complete: '설정 완료',
+    wiki_panel_title: 'LLM Wiki',
+    wiki_panel_desc: 'LLM Wiki \uc9c0\uc2dd \ubca0\uc774\uc2a4 \ud56d\ubaa9 \ud1b5\ud565\uc744 \ud65c\uc131\ud654\uac78\ub9b4 \uc9c0 \uc2eb\uc74c\uc744 \uc124\uc815\ud569\ub2c8\ub2e4.',
+    wiki_status_label: '\uc0c1\ud0dc',
+    wiki_entry_count: '{0}\uac1c \ud56d\ubaa9',
+    wiki_last_modified: '\ub9c8\uc9c0\ub9c9 \uc218\uc815',
+    wiki_not_available: '\uc0ac\uc6a9 \uc218\uc5c6\uc74c',
+    wiki_enabled: 'Wiki \ud65c\uc131\ud654\ub428',
+    wiki_disabled: 'Wiki \ub044\ud658\ub428',
+    wiki_toggle_failed: 'Wiki \ud1b5\uad6c \uc2dc\ub3c4 \uc2e4\ud328: ',
     // panel/runtime i18n
     error_prefix: 'Error: ',
     not_available: 'N/A',
@@ -5960,6 +6074,12 @@ const LOCALES = {
     profile_base_url_label: 'Base URL',
     profile_api_key_label: 'API key',
     cmd_yolo: 'YOLO 모드 전환',
+    cmd_branch: 'Fork this conversation into a new session',
+    cmd_branch_usage: '/branch [name] — fork conversation (optionally with a name)',
+    branch_forked: 'Forked into new session',
+    branch_failed: 'Fork failed: ',
+    fork_from_here: 'Fork from here',
+    forked_from: 'Forked from',
     yolo_no_session: '활성 세션 없음',
     yolo_enabled: '⚡ YOLO 모드 켜짐 — 이 세션에서 승인 건너뜀',
     yolo_disabled: 'YOLO 모드 꺼짐',

static/icons.js

@@ -61,6 +61,7 @@ const LI_PATHS = {
   // Suggestion buttons
   'clipboard-list':  '<path d="M16 4h2a2 2 0 0 1 2 2v14a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2V6a2 2 0 0 1 2-2h2"/><rect x="8" y="2" width="8" height="4" rx="1" ry="1"/><line x1="9" y1="12" x2="15" y2="12"/><line x1="9" y1="16" x2="12" y2="16"/>',
   'map':             '<polygon points="1 6 1 22 8 18 16 22 23 18 23 2 16 6 8 2 1 6"/><line x1="8" y1="2" x2="8" y2="18"/><line x1="16" y1="6" x2="16" y2="22"/>',
+  'git-branch':      '<line x1="6" y1="3" x2="6" y2="15"/><circle cx="18" cy="6" r="3"/><circle cx="6" cy="18" r="3"/><path d="M18 9a9 9 0 0 1-9 9"/>',
 };
 
 /**

static/sessions.js

@@ -1442,6 +1442,19 @@ function renderSessionListFromCache(){
       pinInd.innerHTML=ICONS.pin;
       titleRow.appendChild(pinInd);
     }
+    // Parent session indicator for forked/branched sessions (#465)
+    if(s.parent_session_id){
+      const branchInd=document.createElement('span');
+      branchInd.className='session-branch-indicator';
+      branchInd.textContent='\u2482'; // ⑂
+      branchInd.title=(typeof t==='function'?t('forked_from'):'Forked from')+' '+s.parent_session_id;
+      branchInd.style.cursor='pointer';
+      branchInd.onclick=(e)=>{
+        e.stopPropagation();
+        if(typeof loadSession==='function') loadSession(s.parent_session_id);
+      };
+      titleRow.appendChild(branchInd);
+    }
     const title=document.createElement('span');
     title.className='session-title';
     title.textContent=cleanTitle||'Untitled';

static/ui.js

@@ -3127,6 +3127,7 @@ function renderMessages(){
     const undoBtn  = isLastAssistant ? `<button class="msg-action-btn" title="${t('undo_exchange')}" onclick="undoLastExchange()">${li('undo',13)}</button>` : '';
     const retryBtn = isLastAssistant ? `<button class="msg-action-btn" title="${t('regenerate')}" onclick="regenerateResponse(this)">${li('rotate-ccw',13)}</button>` : '';
     const copyBtn  = `<button class="msg-copy-btn msg-action-btn" title="${t('copy')}" onclick="copyMsg(this)">${li('copy',13)}</button>`;
+    const forkBtn  = `<button class="msg-action-btn" title="${t('fork_from_here')}" onclick="forkFromMessage(${rawIdx+1})">${li('git-branch',13)}</button>`;
     const ttsBtn   = !isUser ? `<button class="msg-action-btn msg-tts-btn" title="${t('tts_listen')||'Listen'}" onclick="speakMessage(this)">${li('volume-2',13)}</button>` : '';
     const tsVal=m._ts||m.timestamp;
     // _formatInServerTz handles fractional-hour offsets (India +0530 etc.)
@@ -3135,7 +3136,7 @@ function renderMessages(){
     const tsTitle=tsVal?(_fmtSv?_fmtSv(new Date(tsVal*1000),{}):new Date(tsVal*1000).toLocaleString()):'';
     const tsTime=_formatMessageFooterTimestamp(tsVal);
     const timeHtml = tsTime ? `<span class="msg-time" title="${esc(tsTitle)}">${tsTime}</span>` : '';
-    const footHtml = `<div class="msg-foot">${timeHtml}<span class="msg-actions">${editBtn}${ttsBtn}${copyBtn}${retryBtn}</span></div>`;
+    const footHtml = `<div class="msg-foot">${timeHtml}<span class="msg-actions">${editBtn}${ttsBtn}${forkBtn}${copyBtn}${retryBtn}</span></div>`;
 
     if(_isContextCompactionMessage(m)){
       if(compressionState || referenceNode){

tests/test_465_session_branching.py

@@ -0,0 +1,273 @@
+"""Tests for issue #465 — session branching (/branch).
+
+Verifies:
+  1. Backend endpoint POST /api/session/branch exists in routes.py
+  2. Session model supports parent_session_id field
+  3. Frontend /branch slash command is registered
+  4. forkFromMessage function exists in commands.js
+  5. Fork button (git-branch icon) is rendered in ui.js message actions
+  6. Parent session indicator (⑂) is rendered in sessions.js sidebar
+  7. i18n keys exist for all branch-related strings
+  8. git-branch icon exists in icons.js
+"""
+import re
+
+
+# ── Backend ────────────────────────────────────────────────────────────────────
+
+def test_branch_endpoint_exists():
+    """Verify the POST /api/session/branch route handler exists."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    assert '"POST /api/session/branch"' in src or '"/api/session/branch"' in src, \
+        "Missing /api/session/branch route"
+
+
+def test_branch_endpoint_validates_session_id():
+    """Verify the branch endpoint requires session_id."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    # Find the branch block
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match, "Could not find /api/session/branch handler block"
+    block = branch_match.group(1)
+    assert 'require(body, "session_id")' in block, \
+        "Branch handler should validate session_id"
+
+
+def test_branch_endpoint_returns_new_session_id():
+    """Verify the branch endpoint returns session_id and title."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match
+    block = branch_match.group(1)
+    assert '"session_id"' in block, "Branch handler should return session_id"
+    assert '"title"' in block, "Branch handler should return title"
+    assert '"parent_session_id"' in block, \
+        "Branch handler should return parent_session_id"
+
+
+def test_branch_creates_session_with_parent():
+    """Verify the branch creates a Session with parent_session_id set."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match
+    block = branch_match.group(1)
+    assert 'parent_session_id=source.session_id' in block, \
+        "Branch handler should set parent_session_id to source session"
+
+
+def test_branch_keep_count_support():
+    """Verify the branch endpoint supports keep_count parameter."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match
+    block = branch_match.group(1)
+    assert 'keep_count' in block, "Branch handler should support keep_count"
+    assert 'forked_messages = source_messages[:keep_count]' in block, \
+        "Branch handler should slice messages by keep_count"
+
+
+def test_branch_auto_title():
+    """Verify fork title defaults to '<original> (fork)'."""
+    with open('api/routes.py') as f:
+        src = f.read()
+    branch_match = re.search(
+        r'parsed\.path == "/api/session/branch"(.*?)(?=\n    if parsed\.path|$)',
+        src, re.DOTALL
+    )
+    assert branch_match
+    block = branch_match.group(1)
+    assert '(fork)' in block, "Branch handler should auto-title as '(fork)'"
+
+
+# ── Session model ──────────────────────────────────────────────────────────────
+
+def test_session_model_parent_session_id():
+    """Verify Session model supports parent_session_id."""
+    with open('api/models.py') as f:
+        src = f.read()
+    assert 'parent_session_id' in src, "Session model should have parent_session_id"
+    # Check __init__ parameter
+    assert 'parent_session_id: str=None' in src, \
+        "Session.__init__ should accept parent_session_id parameter"
+    # Check it's set on self
+    assert 'self.parent_session_id = parent_session_id' in src, \
+        "Session.__init__ should assign parent_session_id"
+
+
+def test_session_compact_includes_parent():
+    """Verify compact() includes parent_session_id."""
+    with open('api/models.py') as f:
+        src = f.read()
+    # Use simpler search - find the compact method and check for parent_session_id after it
+    compact_def_match = re.search(r"def compact\(self", src)
+    assert compact_def_match, "Could not find compact() method"
+    # Check the next 1000 chars after def compact for parent_session_id
+    snippet = src[compact_def_match.start():compact_def_match.start() + 1500]
+    assert "'parent_session_id'" in snippet, \
+        "compact() should include parent_session_id"
+
+
+def test_session_metadata_fields_includes_parent():
+    """Verify parent_session_id is in METADATA_FIELDS for persistence."""
+    with open('api/models.py') as f:
+        src = f.read()
+    assert "'parent_session_id'" in src, \
+        "METADATA_FIELDS should include parent_session_id"
+
+
+# ── Frontend: slash command ────────────────────────────────────────────────────
+
+def test_branch_slash_command_registered():
+    """Verify /branch is registered as a slash command."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    assert "name:'branch'" in src, "/branch should be registered as a command"
+    assert 'cmdBranch' in src, "cmdBranch handler should be defined"
+
+
+def test_cmdBranch_function_exists():
+    """Verify cmdBranch function is defined."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    assert 'async function cmdBranch(' in src, \
+        "cmdBranch should be an async function"
+
+
+def test_cmdBranch_calls_branch_endpoint():
+    """Verify cmdBranch calls the /api/session/branch endpoint."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    branch_fn = re.search(r'async function cmdBranch\(.*?\n\}', src, re.DOTALL)
+    assert branch_fn, "Could not find cmdBranch function"
+    block = branch_fn.group(0)
+    assert "'/api/session/branch'" in block, \
+        "cmdBranch should call /api/session/branch"
+
+
+def test_cmdBranch_switches_session():
+    """Verify cmdBranch calls loadSession after branching."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    branch_fn = re.search(r'async function cmdBranch\(.*?\n\}', src, re.DOTALL)
+    assert branch_fn
+    block = branch_fn.group(0)
+    assert 'loadSession(' in block, \
+        "cmdBranch should switch to the new session via loadSession"
+
+
+# ── Frontend: forkFromMessage ─────────────────────────────────────────────────
+
+def test_forkFromMessage_function_exists():
+    """Verify forkFromMessage function exists."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    assert 'async function forkFromMessage(' in src, \
+        "forkFromMessage should be defined"
+
+
+def test_forkFromMessage_passes_keep_count():
+    """Verify forkFromMessage passes keep_count to the endpoint."""
+    with open('static/commands.js') as f:
+        src = f.read()
+    fn = re.search(r'async function forkFromMessage\(.*?\n\}', src, re.DOTALL)
+    assert fn
+    block = fn.group(0)
+    assert 'keep_count' in block, \
+        "forkFromMessage should pass keep_count to /api/session/branch"
+
+
+# ── Frontend: fork button in messages ──────────────────────────────────────────
+
+def test_fork_button_rendered_in_ui():
+    """Verify fork button is rendered in message actions."""
+    with open('static/ui.js') as f:
+        src = f.read()
+    assert "forkBtn" in src, "forkBtn variable should exist in ui.js"
+    assert "fork_from_here" in src, \
+        "fork_from_here i18n key should be referenced for tooltip"
+    assert "forkFromMessage(" in src, \
+        "forkFromMessage should be called from the button"
+
+
+def test_fork_button_in_message_actions():
+    """Verify fork button is included in the msg-actions span."""
+    with open('static/ui.js') as f:
+        src = f.read()
+    # The footHtml template should include forkBtn
+    assert '${forkBtn}' in src, \
+        "forkBtn should be included in message actions template"
+
+
+# ── Frontend: sidebar parent indicator ────────────────────────────────────────
+
+def test_sidebar_parent_indicator():
+    """Verify parent session indicator is rendered in session list."""
+    with open('static/sessions.js') as f:
+        src = f.read()
+    assert 'parent_session_id' in src, \
+        "sessions.js should check parent_session_id"
+    assert 'session-branch-indicator' in src, \
+        "Should have session-branch-indicator class"
+    assert '\\u2482' in src, \
+        "Should use ⑂ character for parent indicator"
+
+
+def test_parent_indicator_clickable():
+    """Verify parent indicator navigates to parent session on click."""
+    with open('static/sessions.js') as f:
+        src = f.read()
+    # Find the parent indicator block
+    parent_block = re.search(
+        r'parent_session_id\).*?(?=titleRow\.appendChild)',
+        src, re.DOTALL
+    )
+    assert parent_block, "Could not find parent indicator block"
+    block = parent_block.group(0)
+    assert 'loadSession(' in block, \
+        "Parent indicator should call loadSession on click"
+
+
+# ── Frontend: i18n keys ────────────────────────────────────────────────────────
+
+def test_i18n_branch_keys():
+    """Verify all branch-related i18n keys exist in English locale."""
+    with open('static/i18n.js') as f:
+        src = f.read()
+    required_keys = [
+        'cmd_branch',
+        'cmd_branch_usage',
+        'branch_forked',
+        'branch_failed',
+        'fork_from_here',
+        'forked_from',
+    ]
+    for key in required_keys:
+        assert f"{key}:" in src or f"{key} :" in src, \
+            f"Missing i18n key: {key}"
+
+
+# ── Frontend: icon ─────────────────────────────────────────────────────────────
+
+def test_git_branch_icon_exists():
+    """Verify git-branch icon is defined in icons.js."""
+    with open('static/icons.js') as f:
+        src = f.read()
+    assert "'git-branch'" in src, \
+        "git-branch icon should be defined in LI_PATHS"

tests/test_issue1195_session_profile_routing.py

@@ -1,81 +1,116 @@
-"""Tests for issue #1195: sessions must route to the correct profile directory
-even when that profile directory does not exist yet on disk."""
+"""Regression tests for issue #1195.
 
+When the WebUI creates a session for a profile whose directory doesn't exist yet
+(e.g. 'ayan' in ~/.hermes/profiles/ayan/), the session must be routed to that
+profile's sessions dir — NOT to the default ~/.hermes/ dir.  Otherwise sessions
+created in WebUI for 'ayan' appear in TUI under 'awen' or 'default', breaking
+profile isolation.
+"""
+import importlib
 import os
+import sys
 import tempfile
 from pathlib import Path
-from unittest.mock import patch
 
 import pytest
 
-
-# ── helpers ──────────────────────────────────────────────────────────────────
-
-def _make_hermes_home(base: Path, profile_name: str | None = None) -> Path:
-    """Create a temp HERMES_HOME (with optional profile dir) and return it."""
-    hermes_home = base / ".hermes"
-    hermes_home.mkdir(parents=True, exist_ok=True)
-    if profile_name:
-        (hermes_home / "profiles" / profile_name).mkdir(parents=True, exist_ok=True)
-    return hermes_home
+REPO_ROOT = Path(__file__).parent.parent.resolve()
+if str(REPO_ROOT) not in sys.path:
+    sys.path.insert(0, str(REPO_ROOT))
 
 
-# ── tests ────────────────────────────────────────────────────────────────────
+def _reload_profiles_module(base_home: Path):
+    """Hot-reload api.profiles with a fresh _DEFAULT_HERMES_HOME."""
+    os.environ["HERMES_BASE_HOME"] = str(base_home)
+    os.environ["HERMES_HOME"] = str(base_home)
 
-class TestGetHermesHomeForProfile:
-    """get_hermes_home_for_profile() must return the profile path regardless of
-    whether the directory already exists on disk (#1195)."""
+    # Save and remove so we get a fresh import
+    _saved = {name: sys.modules[name] for name in ["api.config", "api.profiles"]
+              if name in sys.modules}
+    for name in ["api.config", "api.profiles"]:
+        if name in sys.modules:
+            del sys.modules[name]
 
-    @pytest.fixture(autouse=True)
-    def _patch_default_home(self, tmp_path):
-        """Patch _DEFAULT_HERMES_HOME to a temp directory for isolation."""
-        from api.profiles import _DEFAULT_HERMES_HOME as real_default
+    profiles = importlib.import_module("api.profiles")
 
-        fake_home = tmp_path / ".hermes"
-        fake_home.mkdir(parents=True)
-        with patch("api.profiles._DEFAULT_HERMES_HOME", fake_home):
-            yield fake_home, real_default
+    # Restore so other tests aren't broken
+    sys.modules.update(_saved)
+    return profiles
 
-    def test_existing_profile_returns_profile_dir(self, _patch_default_home):
-        fake_home, _ = _patch_default_home
-        from api.profiles import get_hermes_home_for_profile
 
-        # Create an existing profile directory
-        profile_dir = fake_home / "profiles" / "ayan"
+def test_get_hermes_home_routes_to_profile_dir_when_dir_missing():
+    """Issue #1195: get_hermes_home_for_profile should return the profile dir
+    even when that directory does not exist yet.
+
+    WebUI can create sessions for a profile before TUI has ever initialised it.
+    The routing must NOT fallback to default home in that case — otherwise
+    session files end up in the wrong profile directory.
+    """
+    with tempfile.TemporaryDirectory() as td:
+        base = Path(td) / ".hermes"
+        base.mkdir(parents=True)
+        # Deliberately NO profiles/ayan subdir — simulating a WebUI-only profile
+
+        profiles = _reload_profiles_module(base)
+
+        result = profiles.get_hermes_home_for_profile("ayan")
+        expected = base / "profiles" / "ayan"
+
+        assert result == expected, (
+            f"Expected {expected}, got {result}. "
+            "Sessions for 'ayan' would be saved to the wrong directory!"
+        )
+
+
+def test_get_hermes_home_routes_to_existing_profile_dir():
+    """Existing profile dir should still be returned as-is."""
+    with tempfile.TemporaryDirectory() as td:
+        base = Path(td) / ".hermes"
+        base.mkdir(parents=True)
+        profile_dir = base / "profiles" / "ayan"
         profile_dir.mkdir(parents=True)
 
-        result = get_hermes_home_for_profile("ayan")
+        profiles = _reload_profiles_module(base)
+        result = profiles.get_hermes_home_for_profile("ayan")
+
         assert result == profile_dir
 
-    def test_nonexistent_profile_still_returns_profile_path(self, _patch_default_home):
-        """Core bug fix: profile dir doesn't exist yet but should still route there."""
-        fake_home, _ = _patch_default_home
-        from api.profiles import get_hermes_home_for_profile
 
-        # Do NOT create the profile directory
-        expected = fake_home / "profiles" / "newprofile"
-        assert not expected.exists()  # confirm it doesn't exist
+def test_default_profile_routes_to_default_home():
+    """'default' profile should always route to _DEFAULT_HERMES_HOME."""
+    with tempfile.TemporaryDirectory() as td:
+        base = Path(td) / ".hermes"
+        base.mkdir(parents=True)
 
-        result = get_hermes_home_for_profile("newprofile")
-        assert result == expected, "Should route to profile path even when dir missing"
+        profiles = _reload_profiles_module(base)
+        result = profiles.get_hermes_home_for_profile("default")
 
-    def test_none_returns_default(self, _patch_default_home):
-        fake_home, _ = _patch_default_home
-        from api.profiles import get_hermes_home_for_profile
+        assert result == base
 
-        result = get_hermes_home_for_profile(None)
-        assert result == fake_home
 
-    def test_empty_string_returns_default(self, _patch_default_home):
-        fake_home, _ = _patch_default_home
-        from api.profiles import get_hermes_home_for_profile
+def test_none_empty_profile_routes_to_default_home():
+    """None / empty profile should route to default home."""
+    with tempfile.TemporaryDirectory() as td:
+        base = Path(td) / ".hermes"
+        base.mkdir(parents=True)
 
-        result = get_hermes_home_for_profile("")
-        assert result == fake_home
+        profiles = _reload_profiles_module(base)
 
-    def test_default_string_returns_default(self, _patch_default_home):
-        fake_home, _ = _patch_default_home
-        from api.profiles import get_hermes_home_for_profile
+        for name in [None, "", "default"]:
+            result = profiles.get_hermes_home_for_profile(name)
+            assert result == base, f"Profile {name!r} should route to default home"
 
-        result = get_hermes_home_for_profile("default")
-        assert result == fake_home
+
+def test_path_traversal_still_rejected():
+    """Path traversal attempts must still be rejected (security regression guard)."""
+    with tempfile.TemporaryDirectory() as td:
+        base = Path(td) / ".hermes"
+        base.mkdir(parents=True)
+
+        profiles = _reload_profiles_module(base)
+
+        for malicious in ["../../etc", "../..", "%2e%2e/etc"]:
+            result = profiles.get_hermes_home_for_profile(malicious)
+            assert result == base, (
+                f"Path traversal {malicious!r} should be rejected and fallback to default"
+            )