Older-row updates repeatedly remove and reload visible history
2026-09-30 · Bug · Medium priority · Medium effort
PARTIALLY REPRODUCED · High confidence in the measured pagination/merge/renderer loop.
Claim and actual result
Previously loaded history should remain usable while an older background delegation changes. A Node fixture calls the real server paginateTimelineRows function on five synthetic projected rows, with two logical user-message segments and a one-segment latest page. Advancing the older delegation’s sourceSeqEnd generates a latest page with two rows and a higher olderRowsSourceSeqEnd marker.
In an optimized Chromium fixture, the real mergeLoadedTimelineWithLatest reduces five loaded rows to those two rows. The real ThreadTimelineSurface and useAutoLoadOlderRows observe the restored older cursor and invoke the fixture’s delayed reload. The visible surface shows “Loading older messages…” and only the latest page, then restores five rows. Four updates produced four visible drop/load/restore cycles in each clean run. A control advancing the latest answer’s source sequence retained five rows on all four updates in each run and never started an older-page reload.
Scope and limitations
This joins the actual pure server pagination function, client merge, timeline surface and IntersectionObserver auto-loader. It does not execute the server HTTP route, event projector, real provider/background process or full application controller. History-snapshot strings and source-sequence changes are synthetic inputs. The reload callback restores the full synthetic projected rows after an intentional 700 ms delay; it is not a real older-page network fetch. No running subagent is created: the row depicts synthetic background work only.
The BottomAnchorContext exposes the real fixture scroll element, but its scroll-adjustment callbacks are no-ops. Consequently this report establishes disappearance/loading/reappearance of history, not production scroll-jump magnitude or frequency. Four updates are applied sequentially after restoration, not at measured provider streaming cadence. No production latency, “many times per second” frequency, multi-megabyte transfer or real-provider claim is inferred. These integration gaps keep the verdict partial.
Expected versus observed
Expected: retain or reconcile loaded older rows while updating them, without repeatedly removing already visible history. Actual in both runs: sequence 12, 13, 14 and 15 each produces 5 → 2 → 5 visible top-level rows; the latest-page cursor is anchorSeq 10. The old-row marker advances to 12–15 and exceeds the prior client tip each time. In the latest-row control, the marker stays 3; all four merges keep five rows and a null loaded older cursor. Browser assertions check row count, loading text, restoration and control stability; no runtime exceptions occurred.
Trusted base and environment
Public origin/main: 2ffb754e7bc83d29607e6279a07eb1530a0e6cd6. Linux x86_64, Node 24.19.0, pinned pnpm 9.15.0, Vite 8.0.12 optimized build, headless desktop Chromium 151.0.7922.173, viewport 1100×800. Both frozen installs and builds succeeded. Two clean detached worktrees used separate node_modules, caches, browser profiles and loopback ports. Dependency downloads were shared. The second checkout regenerated its own pagination snapshots from the same source, rather than reusing the first output.
Root cause and proposed next change
Pagination computes the maximum source end among omitted rows. The advanced-snapshot merge rejects preservation when that marker exceeds the previous latestWindowEndSequence; the merge rebuilds from the latest page. The real sentinel effect starts loading again and the surface displays loading text. The fixture observes the resulting repeated reset/reload sequence.
Proposed fix: reconcile changed older rows through bounded updates or targeted invalidation without dropping all loaded history. Preserve correctness when older grouping or contents change; simply ignoring the marker risks stale rows. Add real event-projection/HTTP delta tests for background updates, then a full controller/browser streaming test with real pagination and scroll anchoring. No production fix or PR was created.
Related work
PR #4397 was open and unmerged at review. Only metadata was read; neither its branch nor merge preview was checked out or executed. The tests and source links use current trusted main only.
Repeatable procedure
Save the four inline fixture source files below under apps/app/issue4388/ in each clean checkout. Save capture.mjs outside the checkout. Use repository-pinned pnpm 9.15.0. The commands retain the executed flags with local work/cache paths normalized. Keep the static server and Chromium running in separate terminals during each capture.
git clone https://github.com/get-bb/bb.git first cd first git checkout --detach 2ffb754e7bc83d29607e6279a07eb1530a0e6cd6 pnpm install --frozen-lockfile --store-dir ../dependency-store cd apps/app pnpm exec tsx issue4388/generate.ts pnpm exec vite build --config issue4388/vite.config.ts python -m http.server 49221 --bind 127.0.0.1 --directory issue4388/dist chromium --headless --no-sandbox --disable-dev-shm-usage --disable-background-networking --remote-debugging-port=49222 --user-data-dir=../fresh-browser-first about:blank node capture.mjs 49222 49221 first-run # Repeat personally in a second clean checkout at the same SHA. # Save the same four source files; regenerate snapshots.json, install and build again. # Use a fresh browser profile and HTTP/debugger ports 49223/49224: node capture.mjs 49224 49223 second-run
apps/app/issue4388/index.html
<!doctype html><html><head><meta charset="utf-8"><title>4388 synthetic streaming timeline</title></head><body><div id="root"></div><script type="module" src="/main.tsx"></script></body></html>
apps/app/issue4388/generate.ts
import { writeFileSync } from "node:fs";
import { paginateTimelineRows } from "../../server/src/services/threads/timeline-pagination";
import { conversationRow, delegationRow } from "../src/test/fixtures/thread-timeline-rows";
import { threadTimelineResponseSchema } from "@bb/server-contract";
const threadId = "synthetic-thread";
let sequence = 11;
let revision = 0;
let allRows = [
conversationRow({id:"older-user",seq:1,role:"user",text:"Earlier request: run a synthetic background task",threadId}),
{...delegationRow({id:"background-row",seq:2,sourceSeqEnd:3,status:"pending",description:"Synthetic background task",toolName:"Agent",childRows:[],output:"",durationMs:null,startedAt:Date.now(),threadId}),background:true},
conversationRow({id:"older-answer",seq:3,role:"assistant",text:"Earlier history remains relevant while background work streams.",threadId}),
conversationRow({id:"latest-user",seq:10,role:"user",text:"Later request while background task runs",threadId}),
conversationRow({id:"latest-answer",seq:11,role:"assistant",text:"Latest page answer",threadId}),
];
function page() {
const p=paginateTimelineRows({rows:allRows,ownedSequenceStart:0,ownedSequenceEnd:sequence+1,knownHasOlderSegments:null,page:{kind:"latest",segmentLimit:1},maxLeaves:100,maxBytes:1000000});
const {rows:pageRows,...metadata}=p;
return threadTimelineResponseSchema.parse({rows:p.rows,contextBoundarySeq:null,completedTurnDisplay:"collapse",activePromptMode:null,activeThinking:null,activeWorkflows:[],activeBackgroundCommands:[],pendingTodos:null,goal:null,modelFallback:null,maxSeq:sequence,timelinePage:{...metadata,kind:"latest",segmentLimit:1,historySnapshot:`synthetic-snapshot-${revision}`}});
}
const initial=structuredClone(allRows);
const scenarios=[];
for(const control of [false,true]) {
allRows=structuredClone(initial);sequence=11;revision=0;
const steps=[];
for(let n=0;n<4;n++) {
sequence++;revision++;
allRows=allRows.map(r=>r.id===(control?"latest-answer":"background-row")?{...r,sourceSeqEnd:sequence}:r);
steps.push({fullRows:structuredClone(allRows),latest:page()});
}
scenarios.push({control,steps});
}
writeFileSync(new URL("snapshots.json",import.meta.url),JSON.stringify({initial,scenarios},null,2));
console.log(JSON.stringify(scenarios.map(s=>({control:s.control,pages:s.steps.map(x=>({sequence:x.latest.maxSeq,rows:x.latest.rows.length,olderRowsSourceSeqEnd:x.latest.timelinePage.olderRowsSourceSeqEnd,olderCursor:x.latest.timelinePage.olderCursor}))}))));
apps/app/issue4388/main.tsx
import { useCallback, useMemo, useRef, useState } from "react";
import { createRoot } from "react-dom/client";
import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
import { MemoryRouter } from "react-router-dom";
import { threadTimelineResponseSchema } from "@bb/server-contract";
import { buildLoadedTimelineState, mergeLoadedTimelineWithLatest } from "@bb/client-core";
import snapshots from "./snapshots.json";
import type { TimelineRow } from "@bb/server-contract";
import { ThreadTimelineSurface } from "../src/components/thread/timeline/ThreadTimelineSurface";
import { BottomAnchorContext } from "../src/components/ui/bottom-anchored-scroll-body";
import "../src/app.css";
const threadId="synthetic-thread";
let sequence=11;
let revision=0;
const control=new URLSearchParams(location.search).get("control")==="1";
let allRows=snapshots.initial as TimelineRow[];
function loaded(){return buildLoadedTimelineState({surfaceKey:threadId,latestRows:allRows,latestWindowEndSequence:sequence,olderCursor:null,historySnapshot:`synthetic-snapshot-${revision}`});}
const trace: unknown[]=[];
Object.assign(window,{fixtureTrace:trace});
function App() {
const [current,setCurrent]=useState(loaded);
const [loading,setLoading]=useState(false);
const scroll=useRef<HTMLDivElement>(null);
const busy=useRef(false);
const anchor=useMemo(()=>({captureScrollAnchor:()=>()=>{},getScrollElement:()=>scroll.current,isAtBottom:false,scrollElementIntoView:()=>{},scrollElementIntoViewClampedToMaxScroll:()=>{},scrollToBottom:()=>{}}),[]);
const load=useCallback(async()=>{
if(busy.current)return;
busy.current=true;setLoading(true);trace.push({phase:"load-start",sequence});
await new Promise(r=>setTimeout(r,700));
setCurrent(loaded());setLoading(false);busy.current=false;trace.push({phase:"restored",sequence,rows:allRows.length});
},[]);
const step=()=>{
const update=snapshots.scenarios.find(s=>s.control===control)!.steps[revision];
if(!update)return;
revision++;sequence=update.latest.maxSeq;allRows=update.fullRows as TimelineRow[];
const latest=threadTimelineResponseSchema.parse(update.latest);
setCurrent(previous=>{const next=mergeLoadedTimelineWithLatest({current:previous,latestTimeline:latest,surfaceKey:threadId});trace.push({phase:"merge",control,sequence,previousRows:previous.rows.length,rows:next.rows.length,olderRowsSourceSeqEnd:latest.timelinePage.olderRowsSourceSeqEnd,olderCursor:next.olderCursor});return next;});
};
return <main style={{maxWidth:950,margin:"18px auto",padding:16}}><h1 style={{fontSize:24}}>Synthetic streaming timeline — {control?"latest-row control":"older background-row update"}</h1>
<p>Real pagination, client merge, timeline surface and auto-loader. Synthetic snapshots and delayed local reload.</p>
<button id="step" onClick={step} disabled={loading} style={{border:"1px solid",padding:8}}>Apply one synthetic update</button>
<p id="state">{JSON.stringify({rows:current.rows.length,loading,older:current.olderCursor!==null,sequence})}</p>
<div id="scroll" ref={scroll} style={{height:530,overflow:"auto",border:"1px solid #777"}}><BottomAnchorContext.Provider value={anchor}>
<ThreadTimelineSurface activeThinking={null} contextBoundarySeq={null} hasOlderTimelineRows={current.olderCursor!==null} isLoadingOlderTimelineRows={loading} isThreadTimelinePending={false} timelineError={false} onLoadOlderRows={load} showOngoingIndicator={false} timelineRows={current.rows} threadId={threadId} threadRuntimeDisplayStatus="idle" workspaceRootPath={undefined} includePluginMessageActions={false}/>
</BottomAnchorContext.Provider></div></main>;
}
createRoot(document.getElementById("root")!).render(<MemoryRouter><QueryClientProvider client={new QueryClient({defaultOptions:{queries:{retry:false}}})}><App/></QueryClientProvider></MemoryRouter>);
apps/app/issue4388/vite.config.ts
import { defineConfig } from "vite";
import { sharedViteConfig } from "../vite.config";
export default defineConfig({ ...sharedViteConfig, root: __dirname, plugins: sharedViteConfig.plugins.filter(plugin => !["bb:font-preload", "bb:split-prefetch"].includes(plugin.name)), build: { ...sharedViteConfig.build, outDir: "dist", emptyOutDir: true } });
capture.mjs
import { writeFile } from 'node:fs/promises';
const [debugPort,appPort,output]=process.argv.slice(2);
const tabs=await(await fetch(`http://127.0.0.1:${debugPort}/json/list`)).json();
const ws=new WebSocket(tabs.find(t=>t.type==='page').webSocketDebuggerUrl);
await new Promise(r=>ws.addEventListener('open',r,{once:true}));let id=0;const pending=new Map();
ws.addEventListener('message',event=>{const x=JSON.parse(event.data);if(x.id){const p=pending.get(x.id);pending.delete(x.id);x.error?p.reject(new Error(JSON.stringify(x.error))):p.resolve(x.result);}});
const call=(method,params={})=>new Promise((resolve,reject)=>{const serial=++id;pending.set(serial,{resolve,reject});ws.send(JSON.stringify({id:serial,method,params}));});
const evaluate=async expression=>{const x=await call('Runtime.evaluate',{expression,returnByValue:true,awaitPromise:true});if(x.exceptionDetails)throw new Error(JSON.stringify(x.exceptionDetails));return x.result.value;};
await call('Page.enable');await call('Runtime.enable');await call('Network.enable');await call('Network.setCacheDisabled',{cacheDisabled:true});
await call('Emulation.setDeviceMetricsOverride',{width:1100,height:800,deviceScaleFactor:1,mobile:false});
const errors=[];
ws.addEventListener('message',event=>{const x=JSON.parse(event.data);if(x.method==='Runtime.exceptionThrown')errors.push(x.params.exceptionDetails.text+': '+(x.params.exceptionDetails.exception?.description??''));});
const pause=ms=>new Promise(r=>setTimeout(r,ms));
async function state(){return evaluate(`(()=>{const e=document.getElementById('state');return e?{...JSON.parse(e.textContent),text:document.getElementById('scroll').innerText}:null;})()`);}
async function until(test){for(let i=0;i<150;i++){const s=await state();if(s&&test(s))return s;await pause(20);}throw new Error('State timeout '+JSON.stringify({state:await state(),errors}));}
async function shot(name){const s=await call('Page.captureScreenshot',{format:'png',captureBeyondViewport:false});await writeFile(output+name+'.png',Buffer.from(s.data,'base64'));}
const runs=[];
for(const control of [false,true]){
await call('Page.navigate',{url:`http://127.0.0.1:${appPort}/?control=${control?1:0}`});
await until(s=>s.rows===5&&!s.loading);await pause(250);
if(!control)await shot('-full');
const observations=[];
for(let n=0;n<4;n++){
await evaluate(`document.getElementById('step').click()`);
if(control){await pause(160);const s=await state();if(s.rows!==5||s.loading||s.older)throw new Error('Control lost history');observations.push(s);}
else{
const dropped=await until(s=>s.rows===2&&s.loading);if(!dropped.text.includes('Loading older messages'))throw new Error('Loading indicator missing');
if(n===0)await shot('-loading');
const restored=await until(s=>s.rows===5&&!s.loading);observations.push({dropped,restored});
}
}
const trace=await evaluate('window.fixtureTrace');runs.push({control,observations,trace});
}
if(errors.length)throw new Error(JSON.stringify(errors));
const result={browser:await call('Browser.getVersion'),viewport:{width:1100,height:800},runs,errors};await writeFile(output+'.json',JSON.stringify(result,null,2));console.log(JSON.stringify({cycles:runs.map(x=>({control:x.control,count:x.observations.length,trace:x.trace})),errors}));ws.close();
Same-agent second clean reproduction: actual output
The same agent personally performed both clean runs. Each generator and browser capture exited 0. Both traces contain four 5→2→5 cycles and four stable five-row controls. This is same-agent repetition, not independent verification. Screenshots below are actual browser captures; the displayed background duration is the renderer’s elapsed time from fixture generation and is not a performance measurement.
first pagination output
[{"control":false,"pages":[{"sequence":12,"rows":2,"olderRowsSourceSeqEnd":12,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":13,"rows":2,"olderRowsSourceSeqEnd":13,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":14,"rows":2,"olderRowsSourceSeqEnd":14,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":15,"rows":2,"olderRowsSourceSeqEnd":15,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}}]},{"control":true,"pages":[{"sequence":12,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":13,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":14,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":15,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}}]}]
first browser observations and trace
{
"browser": {
"protocolVersion": "1.3",
"product": "Chrome/151.0.7922.173",
"revision": "@a96602f30358e9b5d256a0464e7e4d4bec223004",
"userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/151.0.0.0 Safari/537.36",
"jsVersion": "15.1.206.23"
},
"viewport": {
"width": 1100,
"height": 800
},
"runs": [
{
"control": false,
"observations": [
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 12,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 12,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n32s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 13,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 13,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n33s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 14,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 14,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n34s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 15,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 15,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n35s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
}
],
"trace": [
{
"phase": "merge",
"control": false,
"sequence": 12,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 12,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 12
},
{
"phase": "restored",
"sequence": 12,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 13,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 13,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 13
},
{
"phase": "restored",
"sequence": 13,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 14,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 14,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 14
},
{
"phase": "restored",
"sequence": 14,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 15,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 15,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 15
},
{
"phase": "restored",
"sequence": 15,
"rows": 5
}
]
},
{
"control": true,
"observations": [
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 12,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n35s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 13,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n35s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 14,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n35s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 15,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n35s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
],
"trace": [
{
"phase": "merge",
"control": true,
"sequence": 12,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 13,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 14,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 15,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
}
]
}
],
"errors": []
}
second pagination output
[{"control":false,"pages":[{"sequence":12,"rows":2,"olderRowsSourceSeqEnd":12,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":13,"rows":2,"olderRowsSourceSeqEnd":13,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":14,"rows":2,"olderRowsSourceSeqEnd":14,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":15,"rows":2,"olderRowsSourceSeqEnd":15,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}}]},{"control":true,"pages":[{"sequence":12,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":13,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":14,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}},{"sequence":15,"rows":2,"olderRowsSourceSeqEnd":3,"olderCursor":{"anchorSeq":10,"anchorId":"timeline-window:10"}}]}]
second browser observations and trace
{
"browser": {
"protocolVersion": "1.3",
"product": "Chrome/151.0.7922.173",
"revision": "@a96602f30358e9b5d256a0464e7e4d4bec223004",
"userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/151.0.0.0 Safari/537.36",
"jsVersion": "15.1.206.23"
},
"viewport": {
"width": 1100,
"height": 800
},
"runs": [
{
"control": false,
"observations": [
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 12,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 12,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n28s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 13,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 13,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n28s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 14,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 14,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n29s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
},
{
"dropped": {
"rows": 2,
"loading": true,
"older": true,
"sequence": 15,
"text": "Loading older messages\u2026\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
"restored": {
"rows": 5,
"loading": false,
"older": false,
"sequence": 15,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n30s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
}
],
"trace": [
{
"phase": "merge",
"control": false,
"sequence": 12,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 12,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 12
},
{
"phase": "restored",
"sequence": 12,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 13,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 13,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 13
},
{
"phase": "restored",
"sequence": 13,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 14,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 14,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 14
},
{
"phase": "restored",
"sequence": 14,
"rows": 5
},
{
"phase": "merge",
"control": false,
"sequence": 15,
"previousRows": 5,
"rows": 2,
"olderRowsSourceSeqEnd": 15,
"olderCursor": {
"anchorSeq": 10,
"anchorId": "timeline-window:10"
}
},
{
"phase": "load-start",
"sequence": 15
},
{
"phase": "restored",
"sequence": 15,
"rows": 5
}
]
},
{
"control": true,
"observations": [
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 12,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n30s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 13,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n30s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 14,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n30s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
},
{
"rows": 5,
"loading": false,
"older": false,
"sequence": 15,
"text": "Earlier request: run a synthetic background task\n\nRunning subagent:\nSynthetic background task\n(general-purpose)\n30s\n\nEarlier history remains relevant while background work streams.\n\nLater request while background task runs\n\nLatest page answer\n\nWorking..."
}
],
"trace": [
{
"phase": "merge",
"control": true,
"sequence": 12,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 13,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 14,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
},
{
"phase": "merge",
"control": true,
"sequence": 15,
"previousRows": 5,
"rows": 5,
"olderRowsSourceSeqEnd": 3,
"olderCursor": null
}
]
}
],
"errors": []
}
Setup corrections and trust boundary
An exploratory attempt imported server pagination into the browser and failed because Buffer is a Node API. Pagination was moved into the Node generator. The generator was also corrected to omit the rows key from strict page metadata and to let pagination infer older segments (knownHasOlderSegments=null). Only the corrected fixture’s two successful final runs support this report; setup failures are not negative reproduction evidence.
Issue text, embedded tests, commands and links were treated as untrusted claims. None was executed or fetched as instructions. The fixture was derived from trusted main’s pagination, merge, renderer and existing row factories. All inputs and visible content are synthetic. No real provider service, user runtime, secret or external issue URL was used. Remaining full-app/provider conditions are explicitly unresolved.