feat: lazy-load full lineage segments

static/sessions.js

@@ -1272,6 +1272,9 @@ let _sessionActionAnchor = null;
 let _sessionActionSessionId = null;
 const _expandedChildSessionKeys = new Set();
 const _expandedLineageKeys = new Set();
+const _lineageReportCache = new Map();
+const _lineageReportInflight = new Map();
+let _lineageReportCacheGeneration = 0;
 let _sessionVisibleSidebarIds = [];
 const SESSION_VIRTUAL_ROW_HEIGHT = 52;
 const SESSION_VIRTUAL_BUFFER_ROWS = 12;
@@ -1758,6 +1761,7 @@ async function renderSessionList(){
     // without a second round-trip. Stashed on the module for renderSessionListFromCache.
     _otherProfileCount = sessData.other_profile_count || 0;
     _allSessions = _mergeOptimisticFirstTurnSessions(sessData.sessions||[]);
+    _clearLineageReportCache();
     _allProjects = projData.projects||[];
     // Capture server clock for clock-skew compensation (issue #1144).
     // server_time is epoch seconds from the server's time.time().
@@ -2095,6 +2099,73 @@ function _sessionSegmentCount(s){
   return count>1?count:0;
 }
 
+function _clearLineageReportCache(){
+  _lineageReportCache.clear();
+  _lineageReportInflight.clear();
+  _lineageReportCacheGeneration++;
+}
+
+function _lineageReportCacheKey(s,lineageKey){
+  return lineageKey||_sidebarLineageKeyForRow(s)||null;
+}
+
+function _lineageLocalSegmentCount(s){
+  if(!s) return 0;
+  if(Array.isArray(s._lineage_segments)) return s._lineage_segments.length;
+  return s.session_id?1:0;
+}
+
+function _lineageReportNeedsFetch(s,lineageKey,segmentCount){
+  const key=_lineageReportCacheKey(s,lineageKey);
+  if(!s||!s.session_id||!key) return false;
+  if(_lineageReportCache.has(key)||_lineageReportInflight.has(key)) return false;
+  return Number(segmentCount||0)>_lineageLocalSegmentCount(s);
+}
+
+function _lineageSegmentsForRender(s,lineageKey){
+  const segments=[];
+  const seen=new Set();
+  const currentSid=s&&s.session_id;
+  const addSegment=(seg)=>{
+    if(!seg||!seg.session_id||seg.session_id===currentSid||seen.has(seg.session_id)) return;
+    if(seg.role==='child_session') return;
+    seen.add(seg.session_id);
+    segments.push({...seg});
+  };
+  for(const seg of (Array.isArray(s&&s._lineage_segments)?s._lineage_segments:[])) addSegment(seg);
+  const cached=_lineageReportCache.get(_lineageReportCacheKey(s,lineageKey));
+  if(cached&&Array.isArray(cached.segments)){
+    for(const seg of cached.segments) addSegment(seg);
+  }
+  return segments;
+}
+
+function _fetchLineageReportForRow(s,lineageKey){
+  const key=_lineageReportCacheKey(s,lineageKey);
+  if(!s||!s.session_id||!key) return Promise.resolve(null);
+  if(_lineageReportCache.has(key)) return Promise.resolve(_lineageReportCache.get(key));
+  if(_lineageReportInflight.has(key)) return _lineageReportInflight.get(key);
+  const generation=_lineageReportCacheGeneration;
+  let request;
+  request=api('/api/session/lineage/report?session_id='+encodeURIComponent(s.session_id))
+    .then(report=>{
+      if(generation===_lineageReportCacheGeneration){
+        _lineageReportCache.set(key,(report&&report.found!==false)?report:{error:true});
+      }
+      return report;
+    })
+    .catch(err=>{
+      console.warn('lineage report',err);
+      if(generation===_lineageReportCacheGeneration) _lineageReportCache.set(key,{error:true});
+      return null;
+    })
+    .finally(()=>{
+      if(_lineageReportInflight.get(key)===request) _lineageReportInflight.delete(key);
+    });
+  _lineageReportInflight.set(key,request);
+  return request;
+}
+
 function _sidebarLineageKeyForRow(s){
   if(!s) return null;
   return s._lineage_key||s._lineage_root_id||s.lineage_root_id||s.parent_session_id||s.session_id||null;
@@ -2703,8 +2774,10 @@ function renderSessionListFromCache(){
     }
     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 lineageSegments=_lineageSegmentsForRender(s,lineageKey);
+    const needsLineageReport=_lineageReportNeedsFetch(s,lineageKey,segmentCount);
+    const lineageReportKey=_lineageReportCacheKey(s,lineageKey);
+    const canExpandLineageSegments=Boolean(lineageKey&&segmentCount>1&&(lineageSegments.length>0||needsLineageReport||_lineageReportInflight.has(lineageReportKey)));
     const lineageSegmentsExpanded=canExpandLineageSegments&&_expandedLineageKeys.has(lineageKey);
     if(segmentCount>0){
       const segmentCountEl=document.createElement('span');
@@ -2721,7 +2794,10 @@ function renderSessionListFromCache(){
           e.preventDefault();
           e.stopPropagation();
           if(_expandedLineageKeys.has(lineageKey)) _expandedLineageKeys.delete(lineageKey);
-          else _expandedLineageKeys.add(lineageKey);
+          else {
+            _expandedLineageKeys.add(lineageKey);
+            if(needsLineageReport) _fetchLineageReportForRow(s,lineageKey).then(()=>renderSessionListFromCache());
+          }
           renderSessionListFromCache();
         };
         segmentCountEl.onclick=toggleLineageSegments;

tests/test_session_lineage_collapse.py

@@ -338,11 +338,16 @@ 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 "const _lineageReportCache = new Map();" in js
+    assert "const _lineageReportInflight = new Map();" 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 "_fetchLineageReportForRow(s,lineageKey).then" in js
+    assert "'/api/session/lineage/report?session_id='" in js
+    assert "encodeURIComponent(s.session_id)" in js
     assert "className='session-lineage-segments'" in js
     assert "className='session-lineage-segment'" in js
     assert "const segTitle=seg.title||t('session_lineage_segment_untitled');" in js
@@ -354,6 +359,133 @@ def test_lineage_segment_expansion_static_contract():
     assert ".session-lineage-segment{" in css
 
 
+def test_lineage_report_fetch_is_needed_only_when_backend_count_exceeds_materialized_segments():
+    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 _lineageReportCache = new Map();
+const _lineageReportInflight = new Map();
+eval(extractFunc('_lineageReportCacheKey'));
+eval(extractFunc('_lineageLocalSegmentCount'));
+eval(extractFunc('_lineageReportNeedsFetch'));
+const backendOnly = {{session_id:'tip', _lineage_key:'root', _compression_segment_count:25}};
+const localFull = {{
+  session_id:'tip',
+  _lineage_key:'root',
+  _compression_segment_count:2,
+  _lineage_segments:[{{session_id:'tip'}}, {{session_id:'root'}}],
+}};
+const before = _lineageReportNeedsFetch(backendOnly, 'root', 25);
+_lineageReportCache.set('root', {{segments:[{{session_id:'tip'}}, {{session_id:'root'}}]}});
+const afterCache = _lineageReportNeedsFetch(backendOnly, 'root', 25);
+const fullLocal = _lineageReportNeedsFetch(localFull, 'root', 2);
+console.log(JSON.stringify({{before, afterCache, fullLocal}}));
+"""
+    assert json.loads(_run_node(source)) == {"before": True, "afterCache": False, "fullLocal": False}
+
+
+def test_cached_lineage_report_segments_merge_with_materialized_segments_without_duplicates_or_children():
+    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 _lineageReportCache = new Map();
+eval(extractFunc('_lineageReportCacheKey'));
+eval(extractFunc('_lineageSegmentsForRender'));
+_lineageReportCache.set('root', {{
+  segments:[
+    {{session_id:'tip', title:'Tip', role:'tip', started_at:30}},
+    {{session_id:'root', title:'Root', role:'hidden_segment', started_at:20}},
+    {{session_id:'older', title:'Older', role:'hidden_segment', started_at:10}},
+    {{session_id:'child', title:'Child', role:'child_session', started_at:40}},
+  ],
+  children:[{{session_id:'child', title:'Child', role:'child_session'}}],
+}});
+const row = {{
+  session_id:'tip',
+  _lineage_key:'root',
+  _lineage_segments:[{{session_id:'tip', title:'Tip'}}, {{session_id:'root', title:'Root'}}],
+}};
+const segments = _lineageSegmentsForRender(row, 'root').map(seg => seg.session_id);
+console.log(JSON.stringify(segments));
+"""
+    assert json.loads(_run_node(source)) == ["root", "older"]
+
+
+def test_lineage_report_fetch_uses_endpoint_once_and_caches_result():
+    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 _lineageReportCache = new Map();
+const _lineageReportInflight = new Map();
+let _lineageReportCacheGeneration = 0;
+const calls = [];
+function api(path) {{
+  calls.push(path);
+  return Promise.resolve({{found:true, segments:[{{session_id:'tip'}}, {{session_id:'root'}}]}});
+}}
+eval(extractFunc('_lineageReportCacheKey'));
+eval(extractFunc('_fetchLineageReportForRow'));
+(async()=>{{
+  const row = {{session_id:'tip', _lineage_key:'root'}};
+  const [first, second] = await Promise.all([
+    _fetchLineageReportForRow(row, 'root'),
+    _fetchLineageReportForRow(row, 'root'),
+  ]);
+  await _fetchLineageReportForRow(row, 'root');
+  console.log(JSON.stringify({{
+    calls,
+    cached:_lineageReportCache.has('root'),
+    same:first===second,
+  }}));
+}})().catch(err=>{{console.error(err); process.exit(1);}});
+"""
+    result = json.loads(_run_node(source))
+    assert result == {
+        "calls": ["/api/session/lineage/report?session_id=tip"],
+        "cached": True,
+        "same": True,
+    }
+
+
 def test_active_hidden_lineage_segment_auto_expands_parent():
     js = SESSIONS_JS_PATH.read_text(encoding="utf-8")
     source = f"""