feat: expand collapsed session lineage segments

static/sessions.js

@@ -1097,6 +1097,7 @@ let _sessionActionMenu = null;
 let _sessionActionAnchor = null;
 let _sessionActionSessionId = null;
 const _expandedChildSessionKeys = new Set();
+const _expandedLineageKeys = new Set();
 let _sessionVisibleSidebarIds = [];
 const SESSION_VIRTUAL_ROW_HEIGHT = 52;
 const SESSION_VIRTUAL_BUFFER_ROWS = 12;
@@ -1943,6 +1944,9 @@ function _syncSidebarExpansionForActiveSession(rows, activeSid){
     if(Array.isArray(row._child_sessions)&&row._child_sessions.some(child=>child&&child.session_id===activeSid)){
       _expandedChildSessionKeys.add(key);
     }
+    if(Array.isArray(row._lineage_segments)&&row._lineage_segments.some(seg=>seg&&seg.session_id===activeSid&&seg.session_id!==row.session_id)){
+      _expandedLineageKeys.add(key);
+    }
   }
 }
 
@@ -2426,13 +2430,34 @@ function renderSessionListFromCache(){
     ts.className='session-time'+(hasAttentionState?' is-hidden':'');
     ts.textContent=hasAttentionState?'':_formatRelativeSessionTime(tsMs);
     titleRow.appendChild(title);
+    const lineageKey=_sidebarLineageKeyForRow(s);
     const segmentCount=_sessionSegmentCount(s);
+    const lineageSegments=Array.isArray(s._lineage_segments)?s._lineage_segments.filter(seg=>seg&&seg.session_id&&seg.session_id!==s.session_id):[];
+    const canExpandLineageSegments=Boolean(lineageKey&&segmentCount>1&&lineageSegments.length>0);
+    const lineageSegmentsExpanded=canExpandLineageSegments&&_expandedLineageKeys.has(lineageKey);
     if(segmentCount>0){
       const segmentCountEl=document.createElement('span');
-      segmentCountEl.className='session-lineage-count';
+      segmentCountEl.className='session-lineage-count'+(canExpandLineageSegments?' expandable':'');
       const segmentLabel=t('session_meta_segments', segmentCount);
       segmentCountEl.textContent=segmentLabel;
       segmentCountEl.title=segmentLabel;
+      if(canExpandLineageSegments){
+        segmentCountEl.setAttribute('role','button');
+        segmentCountEl.setAttribute('tabindex','0');
+        segmentCountEl.setAttribute('aria-expanded',lineageSegmentsExpanded?'true':'false');
+        ['pointerdown','pointerup','click'].forEach(ev=>segmentCountEl.addEventListener(ev,e=>e.stopPropagation()));
+        const toggleLineageSegments=(e)=>{
+          e.preventDefault();
+          e.stopPropagation();
+          if(_expandedLineageKeys.has(lineageKey)) _expandedLineageKeys.delete(lineageKey);
+          else _expandedLineageKeys.add(lineageKey);
+          renderSessionListFromCache();
+        };
+        segmentCountEl.onclick=toggleLineageSegments;
+        segmentCountEl.onkeydown=(e)=>{
+          if(e.key==='Enter'||e.key===' '){toggleLineageSegments(e);}
+        };
+      }
       titleRow.appendChild(segmentCountEl);
     }
     const childCount=typeof s._child_session_count==='number'?s._child_session_count:(Array.isArray(s._child_sessions)?s._child_sessions.length:0);
@@ -2489,7 +2514,32 @@ function renderSessionListFromCache(){
       meta.textContent=metaBits.join(' · ');
       sessionText.appendChild(meta);
     }
-    const lineageKey=_sidebarLineageKeyForRow(s);
+    if(lineageSegmentsExpanded){
+      const lineageList=document.createElement('div');
+      lineageList.className='session-lineage-segments';
+      ['pointerdown','pointerup','click'].forEach(ev=>lineageList.addEventListener(ev,e=>e.stopPropagation()));
+      const sortedSegments=[...lineageSegments].sort((a,b)=>_sessionTimestampMs(b)-_sessionTimestampMs(a));
+      for(const seg of sortedSegments){
+        const row=document.createElement('button');
+        row.type='button';
+        row.className='session-lineage-segment'+(activeSidForSidebar&&seg.session_id===activeSidForSidebar?' active':'');
+        const segTitle=seg.title||'Untitled segment';
+        const segTime=_formatRelativeSessionTime(_sessionTimestampMs(seg));
+        row.textContent=`-> ${segTitle} - ${segTime}`;
+        row.title='Open lineage segment';
+        row.onclick=async(e)=>{
+          e.stopPropagation();
+          if(seg.is_cli_session){
+            try{await api('/api/session/import_cli',{method:'POST',body:JSON.stringify({session_id:seg.session_id})});}
+            catch(_e){ /* read-only fallback */ }
+          }
+          await loadSession(seg.session_id);
+          renderSessionListFromCache();
+        };
+        lineageList.appendChild(row);
+      }
+      sessionText.appendChild(lineageList);
+    }
     if(childCount>0&&Array.isArray(s._child_sessions)&&_expandedChildSessionKeys.has(lineageKey)){
       const childList=document.createElement('div');
       childList.className='session-child-sessions';
@@ -2686,7 +2736,7 @@ function renderSessionListFromCache(){
       _pointerActive=false;
       if(_renamingSid) return;
       if(actions&&actions.contains(e.target)) return;
-      if(e.target&&e.target.closest&&e.target.closest('.session-child-count,.session-child-sessions,.session-child-session')) return;
+      if(e.target&&e.target.closest&&e.target.closest('.session-child-count,.session-child-sessions,.session-child-session,.session-lineage-count,.session-lineage-segments,.session-lineage-segment')) return;
       if(_sessionSelectMode){e.stopPropagation();if(!readOnly)toggleSessionSelect(s.session_id);return;}
       // If the pointer moved enough to be a drag, cancel any pending tap
       if(_isDragging){clearTimeout(_tapTimer);_tapTimer=null;_lastTapTime=0;_clearDragTimer=setTimeout(()=>{el.classList.remove('dragging');_clearDragTimer=null;},50);return;}

static/style.css

@@ -2670,7 +2670,12 @@ main.main.showing-logs > #mainLogs{display:flex;}
 
 /* ── Subagent session tree (#494) ── */
 .session-lineage-count{display:inline-flex;align-items:center;justify-content:center;height:16px;font-size:10px;font-weight:600;padding:0 6px;border-radius:999px;background:rgba(148,163,184,.14);color:var(--muted);margin-left:6px;flex-shrink:0;user-select:none;cursor:default;}
+.session-lineage-count.expandable{cursor:pointer;}
+.session-lineage-count.expandable:hover{background:rgba(148,163,184,.24);color:var(--text);}
 .session-item.active .session-lineage-count{color:var(--accent-text);background:rgba(255,255,255,.14);}
+.session-lineage-segments{display:flex;flex-direction:column;gap:3px;margin-top:6px;margin-left:12px;padding-left:8px;border-left:1px dashed rgba(148,163,184,.22);}
+.session-lineage-segment{appearance:none;border:0;background:transparent;color:var(--muted);font:inherit;font-size:11px;text-align:left;padding:3px 4px;border-radius:5px;cursor:pointer;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}
+.session-lineage-segment:hover,.session-lineage-segment.active{background:rgba(148,163,184,.12);color:var(--text);}
 .session-child-count{display:inline-flex;align-items:center;justify-content:center;height:16px;font-size:10px;font-weight:600;padding:0 6px;border-radius:999px;background:rgba(99,179,237,.16);color:#63b3ed;margin-left:6px;flex-shrink:0;user-select:none;cursor:pointer;}
 .session-child-count:hover{background:rgba(99,179,237,.26);color:#90cdf4;}
 .session-child-sessions{display:flex;flex-direction:column;gap:3px;margin-top:6px;margin-left:12px;padding-left:8px;border-left:1px solid var(--border,rgba(255,255,255,.1));}

tests/test_session_lineage_collapse.py

@@ -283,7 +283,7 @@ console.log(JSON.stringify(cases));
     assert json.loads(_run_node(source)) == [3, 25, 3, 0, 0]
 
 
-def test_sidebar_lineage_segment_badge_is_passive_and_localized():
+def test_sidebar_lineage_segment_badge_is_localized():
     js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
     css = (REPO_ROOT / "static" / "style.css").read_text(encoding="utf-8")
     assert "session-lineage-count" in js
@@ -291,8 +291,60 @@ def test_sidebar_lineage_segment_badge_is_passive_and_localized():
     assert "t('session_meta_segments', segmentCount)" in js
     assert "titleRow.appendChild(segmentCountEl);" in js
     assert ".session-lineage-count{" in css
-    assert "cursor:default" in css
-    assert "session-lineage-count,.session-lineage-segments,.session-lineage-segment" not in js
+
+
+def test_lineage_segment_expansion_static_contract():
+    js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
+    css = (REPO_ROOT / "static" / "style.css").read_text(encoding="utf-8")
+    assert "const _expandedLineageKeys = new Set();" in js
+    assert "session-lineage-count,.session-lineage-segments,.session-lineage-segment" in js
+    assert "segmentCountEl.setAttribute('aria-expanded'" in js
+    assert "_expandedLineageKeys.has(lineageKey)" in js
+    assert "_expandedLineageKeys.add(lineageKey)" in js
+    assert "_expandedLineageKeys.delete(lineageKey)" in js
+    assert "className='session-lineage-segments'" in js
+    assert "className='session-lineage-segment'" in js
+    assert "await loadSession(seg.session_id);" in js
+    assert ".session-lineage-count.expandable{" in css
+    assert ".session-lineage-count.expandable:hover" in css
+    assert ".session-lineage-segments{" in css
+    assert ".session-lineage-segment{" in css
+
+
+def test_active_hidden_lineage_segment_auto_expands_parent():
+    js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
+    source = f"""
+const src = {js!r};
+function extractFunc(name) {{
+  const re = new RegExp('function\\\\s+' + name + '\\\\s*\\\\(');
+  const start = src.search(re);
+  if (start < 0) throw new Error(name + ' not found');
+  let i = src.indexOf('{{', start);
+  let depth = 1; i++;
+  while (depth > 0 && i < src.length) {{
+    if (src[i] === '{{') depth++;
+    else if (src[i] === '}}') depth--;
+    i++;
+  }}
+  return src.slice(start, i);
+}}
+const _expandedChildSessionKeys = new Set();
+const _expandedLineageKeys = new Set();
+eval(extractFunc('_sidebarLineageKeyForRow'));
+eval(extractFunc('_syncSidebarExpansionForActiveSession'));
+const rows = [{{
+  session_id:'seg10',
+  _lineage_key:'root',
+  _lineage_segments:[
+    {{session_id:'seg10', updated_at:100}},
+    {{session_id:'seg9', updated_at:90}},
+    {{session_id:'seg8', updated_at:80}},
+  ],
+}}];
+_syncSidebarExpansionForActiveSession(rows, 'seg8');
+console.log(JSON.stringify({{lineage:[..._expandedLineageKeys], child:[..._expandedChildSessionKeys]}}));
+"""
+    assert json.loads(_run_node(source)) == {"lineage": ["root"], "child": []}
 
 
 def test_session_meta_segments_locale_key_is_defined_for_sidebar_locales():