diff --git a/api/config.py b/api/config.py
index f7b6d30e..d8d60235 100644
--- a/api/config.py
+++ b/api/config.py
@@ -8409,6 +8409,7 @@ _SETTINGS_DEFAULTS = {
     "show_conversation_outline": False,  # show opt-in desktop jump-to-question outline panel
     "show_busy_placeholder_hint": False,  # opt-in busy composer placeholder hint
     "hide_empty_state_suggestions": False,  # hide the default new-chat suggestion buttons
+    "new_chat_on_workspace_switch": False,  # #5473 opt-in: switching to a DIFFERENT workspace starts a new chat (leaving the current conversation on its original workspace) instead of mutating the current session's workspace in place. Default OFF preserves the shipped in-place-switch behavior.
     "virtualize_transcript": False,  # #4343: virtualize long (>80 msg) transcripts. EXPERIMENTAL, opt-IN (default OFF). Was opt-out/default-on in #4325 but caused scroll-up flicker on long sessions with tall tool-call rows (variable-height anchor oscillation) — flipped off for everyone in #4343; re-enabling requires an explicit opt-in (see virtualize_transcript_optin migration in load_settings).
     "virtualize_transcript_optin": False,  # #4343 migration marker: True only once the user explicitly enables virtualize_transcript AFTER the default-off flip. A stored virtualize_transcript=True WITHOUT this marker is a stale pre-flip value and is reset to False on load (force-off-for-everyone migration).
     "show_tps": False,  # show tokens-per-second chip in assistant message headers
@@ -8729,6 +8730,7 @@ _SETTINGS_BOOL_KEYS = {
     "show_conversation_outline",
     "show_busy_placeholder_hint",
     "hide_empty_state_suggestions",
+    "new_chat_on_workspace_switch",
     "virtualize_transcript",
     "virtualize_transcript_optin",
     "show_tps",
diff --git a/static/boot.js b/static/boot.js
index a05b8306..d20bd7cb 100644
--- a/static/boot.js
+++ b/static/boot.js
@@ -2976,6 +2976,7 @@ window._mirrorSpeechSettingsFromServer=_mirrorSpeechSettingsFromServer;
     // after a reload honors the saved choice.
     window._defaultMessageMode=_persistDefaultMessageMode(s.default_message_mode||s.busy_input_mode);
     window._showBusyPlaceholderHint=!!s.show_busy_placeholder_hint;
+    window._newChatOnWorkspaceSwitch=!!s.new_chat_on_workspace_switch;  // #5473 opt-in
     window._sessionEndlessScrollEnabled=!!s.session_endless_scroll;
     window._autoScrollFollow=s.auto_scroll_follow!==false;
     window._largeTextPasteAsAttachment=s.large_text_paste_as_attachment!==false;
diff --git a/static/i18n.js b/static/i18n.js
index 0076ad45..155c7e4a 100644
--- a/static/i18n.js
+++ b/static/i18n.js
@@ -324,6 +324,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Interrupt current turn',
     settings_default_message_mode_steer: 'Steer (mid-turn correction)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -2040,6 +2043,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Interrompi turno corrente',
     settings_default_message_mode_steer: 'Steer (correzione a metà turno)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -3747,6 +3753,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: '現在のターンを中断',
     settings_default_message_mode_steer: 'ステア (ターン中の修正)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -5402,6 +5411,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Прервать текущий оборот',
     settings_default_message_mode_steer: 'Steer (коррекция в середине хода)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -7099,6 +7111,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Interrumpir turno actual',
     settings_default_message_mode_steer: 'Steer (corrección a mitad de turno)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -8711,6 +8726,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Aktuellen Durchgang unterbrechen',
     settings_default_message_mode_steer: 'Steer (Korrektur ohne Unterbrechung)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -10388,6 +10406,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: '中断当前轮次',
     settings_default_message_mode_steer: '引导（中间修正）',
     settings_label_busy_placeholder_hint: '显示忙碌占位提示',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: '在会话运行且草稿为空时，显示带有当前忙碌操作的编辑器占位符。',
     composer_placeholder_busy_queue: 'Enter = 队列 | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = 中断 | /queue | /background | /steer',
@@ -12039,6 +12060,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: '中斷目前回合',
     settings_default_message_mode_steer: 'Steer（中途修正）',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -13675,6 +13699,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Interromper turno atual',
     settings_default_message_mode_steer: 'Steer (correção no meio do turno)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -15265,6 +15292,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: '현재 작업 중단',
     settings_default_message_mode_steer: '조정(중간 수정)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -16964,6 +16994,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Interrompre le tour en cours',
     settings_default_message_mode_steer: 'Steer (correction en milieu de tour)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -19873,6 +19906,9 @@ const LOCALES = {
     settings_desc_model: 'Používá se pro nové konverzace. Stávající konverzace si zachovají svůj vybraný model.',
     settings_desc_rtl: 'Převrátí zarovnání chatových zpráv a vstupního pole editoru pro jazyky jako arabština nebo hebrejština. Ovlivňuje pouze oblast chatu — postranní panel a další panely zůstávají zleva doprava.',
     settings_label_busy_placeholder_hint: 'Zobrazit nápovědu zaneprázdněného zástupného symbolu',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_label_fade_text_effect: 'Efekt vyblednutí textu',
     settings_label_language: 'Jazyk',
     settings_label_max_tokens: 'Maximální výstupní tokeny',
@@ -20327,6 +20363,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Mevcut dönüşü kes',
     settings_default_message_mode_steer: 'Yönlendirme (dönüş ortası düzeltme)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -22020,6 +22059,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Przerwij bieżącą turę',
     settings_default_message_mode_steer: 'Korekta w trakcie tury (steer)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
@@ -23699,6 +23741,9 @@ const LOCALES = {
     settings_default_message_mode_interrupt: 'Ngắt lượt hiện tại',
     settings_default_message_mode_steer: 'Steer (điều chỉnh giữa lượt)',
     settings_label_busy_placeholder_hint: 'Show busy placeholder hint',
+    settings_label_new_chat_on_workspace_switch: 'Start a new chat when switching workspace',
+    settings_desc_new_chat_on_workspace_switch: 'When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace, avoiding stale cross-workspace context. When off (default), switching workspace changes the current workspace in place.',
+    workspace_switched_new_chat: 'Started a new chat in {0}',
     settings_desc_busy_placeholder_hint: 'Shows the composer placeholder with the current busy action while the session is running and the draft is empty.',
     composer_placeholder_busy_queue: 'Enter = queue | /interrupt | /background | /steer',
     composer_placeholder_busy_interrupt: 'Enter = interrupt | /queue | /background | /steer',
diff --git a/static/index.html b/static/index.html
index 9e80551e..dd760428 100644
--- a/static/index.html
+++ b/static/index.html
@@ -1357,6 +1357,13 @@
               </label>
               <div style="font-size:11px;color:var(--muted);margin-top:4px" data-i18n="settings_desc_busy_placeholder_hint">Shows the composer placeholder with the current busy action while the session is running and the draft is empty.</div>
             </div>
+            <div class="settings-field">
+              <label style="display:flex;align-items:center;gap:8px;cursor:pointer">
+                <input type="checkbox" id="settingsNewChatOnWorkspaceSwitch" style="width:15px;height:15px;accent-color:var(--accent)">
+                <span data-i18n="settings_label_new_chat_on_workspace_switch">Start a new chat when switching workspace</span>
+              </label>
+              <div style="font-size:11px;color:var(--muted);margin-top:4px" data-i18n="settings_desc_new_chat_on_workspace_switch">When on, selecting a different workspace starts a fresh conversation bound to that workspace and leaves your current chat on its original workspace — avoiding stale cross-workspace context. When off (default), switching workspace changes the current conversation's workspace in place.</div>
+            </div>
             <div class="settings-field">
               <label style="display:flex;align-items:center;gap:8px;cursor:pointer">
                 <input type="checkbox" id="settingsShowCliSessions" style="width:15px;height:15px;accent-color:var(--accent)">
diff --git a/static/panels.js b/static/panels.js
index 204cb0ac..3bfa0fd0 100644
--- a/static/panels.js
+++ b/static/panels.js
@@ -6349,6 +6349,36 @@ async function switchToWorkspace(path,name){
     showToast(t('workspace_busy_switch'));
     return;
   }
+  // #5473 (opt-in, default off): treat switching to a DIFFERENT workspace as a
+  // new-chat boundary instead of mutating the current session in place. A
+  // workspace switch changes the project-context files the agent loaded, so
+  // reusing the session would carry stale cross-workspace context. Only fires
+  // when: the setting is on, the target workspace actually differs from the
+  // current one, and the current conversation has real messages worth keeping on
+  // its original workspace. Same-workspace selection stays an in-place refresh.
+  if(
+    window._newChatOnWorkspaceSwitch===true &&
+    S.session && S.session.workspace && path && path!==S.session.workspace &&
+    Array.isArray(S.messages) && S.messages.length>0
+  ){
+    if(typeof _previewDirty!=='undefined'&&_previewDirty){
+      const discard=await showConfirmDialog({
+        title:t('discard_file_edits_title'),
+        message:t('discard_file_edits_message'),
+        confirmLabel:t('discard'),
+        danger:true
+      });
+      if(!discard)return;
+      if(typeof cancelEditMode==='function')cancelEditMode();
+      if(typeof clearPreview==='function')clearPreview();
+    }
+    closeWsDropdown();
+    // Bind the new chat to the selected workspace via the one-shot flag newSession() reads.
+    S._profileSwitchWorkspace=path;
+    if(typeof newSession==='function') await newSession(false);
+    showToast(t('workspace_switched_new_chat',name||getWorkspaceFriendlyName(path)));
+    return;
+  }
   if(typeof _previewDirty!=='undefined'&&_previewDirty){
     const discard=await showConfirmDialog({
       title:t('discard_file_edits_title'),
@@ -8638,6 +8668,8 @@ function _preferencesPayloadFromUi(){
   if(defaultMessageModeSel) payload.default_message_mode=defaultMessageModeSel.value;
   const showBusyPlaceholderHintCb=$('settingsShowBusyPlaceholderHint');
   if(showBusyPlaceholderHintCb) payload.show_busy_placeholder_hint=showBusyPlaceholderHintCb.checked;
+  const newChatOnWorkspaceSwitchCb=$('settingsNewChatOnWorkspaceSwitch');
+  if(newChatOnWorkspaceSwitchCb) payload.new_chat_on_workspace_switch=newChatOnWorkspaceSwitchCb.checked;
   const botNameField=$('settingsBotName');
   if(botNameField) payload.bot_name=botNameField.value;
   Object.assign(payload,_speechPreferencesPayloadFromUi());
@@ -8747,6 +8779,9 @@ async function _autosavePreferencesSettings(payload){
       window._showBusyPlaceholderHint=!!(saved&&saved.show_busy_placeholder_hint);
       if(typeof _applyBusyComposerPlaceholder==='function') _applyBusyComposerPlaceholder();
     }
+    if(payload&&payload.new_chat_on_workspace_switch!==undefined){
+      window._newChatOnWorkspaceSwitch=!!(saved&&saved.new_chat_on_workspace_switch);  // #5473
+    }
     _settingsPreferencesAutosaveRetryPayload=null;
     _setPreferencesAutosaveStatus('saved');
     // Only clear the global dirty flag and hide the unsaved-changes bar when
@@ -9441,6 +9476,12 @@ async function loadSettingsPanel(){
       showBusyPlaceholderHintCb.addEventListener('change',_schedulePreferencesAutosave,{once:false});
     }
     if(typeof _applyBusyComposerPlaceholder==='function') _applyBusyComposerPlaceholder();
+    const newChatOnWorkspaceSwitchCb=$('settingsNewChatOnWorkspaceSwitch');
+    if(newChatOnWorkspaceSwitchCb){
+      newChatOnWorkspaceSwitchCb.checked=!!settings.new_chat_on_workspace_switch;
+      window._newChatOnWorkspaceSwitch=newChatOnWorkspaceSwitchCb.checked;
+      newChatOnWorkspaceSwitchCb.addEventListener('change',_schedulePreferencesAutosave,{once:false});
+    }
     // Bot name — debounced autosave (text input)
     const botNameField=$('settingsBotName');
     if(botNameField){
diff --git a/tests/test_workspace_blank_page_fix.py b/tests/test_workspace_blank_page_fix.py
index e92b5b91..05f77f17 100644
--- a/tests/test_workspace_blank_page_fix.py
+++ b/tests/test_workspace_blank_page_fix.py
@@ -201,3 +201,69 @@ class TestWorkspaceDropdownBlankPageCurrentWs:
             "renderWorkspaceDropdownInto must use session, profile default, or data.last "
             "as current workspace on blank page"
         )
+
+
+class TestNewChatOnWorkspaceSwitchOptIn:
+    """#5473 opt-in: switching to a DIFFERENT workspace starts a new chat instead
+    of mutating the current session in place. Default OFF preserves shipped behavior."""
+
+    def test_setting_registered_default_off(self):
+        import api.config as c
+        assert c._SETTINGS_DEFAULTS.get('new_chat_on_workspace_switch') is False, (
+            "new_chat_on_workspace_switch must default to False (shipped in-place behavior)"
+        )
+        assert 'new_chat_on_workspace_switch' in c._SETTINGS_BOOL_KEYS, (
+            "new_chat_on_workspace_switch must be a recognized boolean setting key"
+        )
+
+    def test_switch_to_workspace_has_gated_new_chat_branch(self):
+        src = read('static/panels.js')
+        start = src.find('async function switchToWorkspace(')
+        assert start != -1
+        fn = src[start:src.find('async function toggleWorktreePanel', start)]
+        # The new-chat branch must be gated on the opt-in flag AND a different workspace.
+        assert 'window._newChatOnWorkspaceSwitch===true' in fn, (
+            "the new-chat branch must be gated on the default-off opt-in flag"
+        )
+        assert 'path!==S.session.workspace' in fn, (
+            "the new-chat branch must only fire when the target workspace DIFFERS "
+            "(same-workspace selection stays an in-place refresh/no-op)"
+        )
+        assert 'S.messages.length>0' in fn, (
+            "the new-chat branch must only fire when the current conversation has messages"
+        )
+        assert 'newSession(false)' in fn, (
+            "the new-chat branch must call newSession() to start the fresh chat"
+        )
+        # The branch must run BEFORE the in-place /api/session/update mutation.
+        newchat_idx = fn.index('window._newChatOnWorkspaceSwitch===true')
+        update_idx = fn.index("api('/api/session/update'")
+        assert newchat_idx < update_idx, (
+            "the opt-in new-chat branch must short-circuit before the in-place workspace update"
+        )
+
+    def test_boot_and_panels_wire_the_flag(self):
+        boot = read('static/boot.js')
+        panels = read('static/panels.js')
+        assert 'window._newChatOnWorkspaceSwitch=!!s.new_chat_on_workspace_switch' in boot, (
+            "boot.js must set window._newChatOnWorkspaceSwitch from the loaded settings"
+        )
+        assert 'settingsNewChatOnWorkspaceSwitch' in panels, (
+            "panels.js must wire the settings checkbox (load + payload)"
+        )
+        assert 'payload.new_chat_on_workspace_switch' in panels, (
+            "panels.js must include new_chat_on_workspace_switch in the autosave payload"
+        )
+
+    def test_settings_checkbox_and_i18n_present(self):
+        html = read('static/index.html')
+        assert 'id="settingsNewChatOnWorkspaceSwitch"' in html, (
+            "the Settings checkbox for the opt-in must exist"
+        )
+        i18n = read('static/i18n.js')
+        for key in (
+            'settings_label_new_chat_on_workspace_switch',
+            'settings_desc_new_chat_on_workspace_switch',
+            'workspace_switched_new_chat',
+        ):
+            assert key in i18n, f"i18n key {key} must be defined"