From 0dfad592bfe721c1dcf0d4b21ed3f004a8c3f9ac Mon Sep 17 00:00:00 2001
From: Yuchao Wang <stevenkid404@gmail.com>
Date: Wed, 4 Nov 2026 07:14:54 +0000
Subject: [PATCH] feat(research): inspect and download captured Turn ranges

Signed-off-by: Yuchao Wang <stevenkid404@gmail.com>
---
 .../goal-research-progress.css                | 14 +++++
 .../goal-research-progress.tsx                |  2 +-
 .../research-turn-costs.tsx                   | 56 +++++++++++++----
 .../research-usage-selection.test.mjs         | 60 +++++++++++++++++++
 .../research-usage-selection.ts               | 48 +++++++++++++++
 docs/reference/trajectory-assessment.md       | 33 ++++++++++
 .../research-turn-costs.mjs                   | 57 +++++++++++++++++-
 7 files changed, 258 insertions(+), 12 deletions(-)
 create mode 100644 apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.test.mjs
 create mode 100644 apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.ts

diff --git a/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.css b/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.css
index ed00edf098..81f73e885a 100644
--- a/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.css
+++ b/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.css
@@ -165,3 +165,17 @@
   .research-turn-cost-list dl { grid-template-columns: repeat(2, minmax(0, 1fr)); }
   .research-turn-costs-sort select { min-height: 44px; }
 }
+
+.research-usage-range { border: 1px solid var(--pw-line); border-radius: 6px; padding: 12px; min-width: 0; }
+.research-usage-range legend { font-size: var(--text-body); }
+.research-usage-range-controls { display: flex; flex-wrap: wrap; align-items: end; gap: 12px; }
+.research-usage-range-controls label { display: grid; gap: 4px; width: auto; font-size: 12px; }
+.research-usage-range input { width: 96px; min-height: 36px; padding: 4px 8px; border: 1px solid var(--pw-line); border-radius: 6px; background: var(--pw-card); color: var(--pw-text); font: inherit; }
+.research-usage-range-summary { font-size: 12px; }
+.research-usage-range-summary dl { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 12px; }
+.research-usage-range-summary dt, .research-usage-range-summary p { color: var(--pw-muted); }
+.research-usage-range-summary dd { margin: 4px 0; font-variant-numeric: tabular-nums; overflow-wrap: anywhere; }
+@media (max-width: 600px) {
+  .research-usage-range input { min-height: 44px; }
+  .research-usage-range-summary dl { grid-template-columns: repeat(2, minmax(0, 1fr)); }
+}
diff --git a/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.tsx b/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.tsx
index 17220c65c9..9252d527a6 100644
--- a/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.tsx
+++ b/apps/presentation/dashboard/src/features/personal-workspace/goal-research-progress.tsx
@@ -335,7 +335,7 @@ export function ResearchProgress({pack: p, packs, selectedId, zh, onSelect, onCi
             </> : null}
           </div> : null}
           </div>
-          {usage && onUsageTurn ? <ResearchTurnCosts key={p.pack_id} usage={usage} zh={zh} onRead={onUsageTurn}/> : null}
+          {usage && onUsageTurn ? <ResearchTurnCosts key={`${p.pack_id}:${measured?.artifact_sha256}`} usage={usage} source={{pack_id: p.pack_id, goal_id: p.scope.goal_id, artifact_sha256: measured!.artifact_sha256, applicability: measured!.applicability}} zh={zh} onRead={onUsageTurn}/> : null}
           {usage && measured ? <details className="research-usage-detail"><summary>{zh ? "计数明细与来源" : "Counter details and source"}</summary>
             <dl className="research-usage-basis">
               <dt>{zh ? "捕获时间（UTC）" : "Capture window (UTC)"}</dt><dd><time dateTime={usage.start}>{stamp(usage.start)}</time> — <time dateTime={usage.end}>{stamp(usage.end)}</time></dd>
diff --git a/apps/presentation/dashboard/src/features/personal-workspace/research-turn-costs.tsx b/apps/presentation/dashboard/src/features/personal-workspace/research-turn-costs.tsx
index 499b988055..c561efea40 100644
--- a/apps/presentation/dashboard/src/features/personal-workspace/research-turn-costs.tsx
+++ b/apps/presentation/dashboard/src/features/personal-workspace/research-turn-costs.tsx
@@ -1,24 +1,30 @@
 import {useId, useState} from "react";
 import type {TrajectorySolverUsage} from "../../../../../../loopx/control_plane/capabilities/trajectory_assessment_types.js";
+import {downloadReport} from "./report-download";
+import {exportResearchUsage, researchUsageRows, selectResearchUsage} from "./research-usage-selection";
 import {ContextHelp} from "./context-help";
 
 /** Presentation of existing Turn counters; never estimates missing usage or attributes it to control work. */
-export function ResearchTurnCosts({usage, zh, onRead}: {usage: TrajectorySolverUsage; zh: boolean;
+export function ResearchTurnCosts({usage, source, zh, onRead}: {usage: TrajectorySolverUsage; zh: boolean;
+  source: Parameters<typeof exportResearchUsage>[3];
   onRead: (turnId: string, origin: HTMLButtonElement) => void}) {
   const id = useId();
   const [sort, setSort] = useState("input");
   const [page, setPage] = useState(0);
-  const rows: Array<Omit<TrajectorySolverUsage["turns"][number], "usage"> & {usage: TrajectorySolverUsage["turns"][number]["usage"] | null; ordinal: number; incomplete: boolean}> = usage.turns.map((turn, index) => ({...turn, ordinal: index + 1, incomplete: false}));
-  const tail = usage.incomplete_turn;
-  if (tail) rows.push({...tail, end: tail.observed_through,
-    elapsed_seconds: Math.max(0, (Date.parse(tail.observed_through) - Date.parse(tail.start)) / 1000),
-    ordinal: rows.length + 1, incomplete: true, usage: tail.usage});
-  const ordered = [...rows].sort((a, b) => {
+  const rows = researchUsageRows(usage);
+  const [first, setFirst] = useState("1");
+  const [last, setLast] = useState(String(rows.length));
+  const [downloadFailed, setDownloadFailed] = useState(false);
+  const valid = Number.isInteger(Number(first)) && Number.isInteger(Number(last))
+    && Number(first) >= 1 && Number(last) >= Number(first) && Number(last) <= rows.length;
+  const selection = valid ? selectResearchUsage(usage, Number(first), Number(last)) : null;
+  const selectedRows = selection?.turns ?? [];
+  const ordered = [...selectedRows].sort((a, b) => {
     const value = (row: typeof a) => sort === "elapsed" ? row.elapsed_seconds
       : sort === "time" ? row.ordinal : row.usage?.input_tokens ?? -1;
     return (sort === "time" ? value(a) - value(b) : value(b) - value(a)) || a.ordinal - b.ordinal;
   });
-  const size = 8, pages = Math.max(1, Math.ceil(rows.length / size)), current = Math.min(page, pages - 1);
+  const size = 8, pages = Math.max(1, Math.ceil(selectedRows.length / size)), current = Math.min(page, pages - 1);
   const number = (n: number | undefined | null) => n == null ? "—" : n.toLocaleString(zh ? "zh-CN" : "en");
   return <details className="research-turn-costs">
     <summary>{zh ? "定位耗时与输入最多的轮次" : "Find time and input hotspots"}</summary>
@@ -35,7 +41,37 @@ export function ResearchTurnCosts({usage, zh, onRead}: {usage: TrajectorySolverU
         <p>{zh ? "仅比较当前捕获内的轮次。耗时含工具、等待与编排，不是可节省时间；轮次输入不等于 LoopX 控制输入。金额未采集。" : "Compares Turns within this capture only. Elapsed time includes tools, waiting and orchestration, not avoidable time. Turn input is not LoopX control input. Dollar cost is unmeasured."}</p>
       </ContextHelp>
     </div>
-    {rows.length ? <ol className="research-turn-cost-list">
+    {rows.length ? <fieldset className="research-usage-range">
+      <legend>{zh ? "分析轮次范围" : "Analyze a Turn range"}</legend>
+      <div className="research-usage-range-controls">
+        <label>{zh ? "起始轮次" : "First Turn"}<input type="number" min="1" max={rows.length} step="1" value={first}
+          aria-invalid={!valid} onChange={event => {setFirst(event.target.value); setPage(0); setDownloadFailed(false);}}/></label>
+        <label>{zh ? "结束轮次" : "Last Turn"}<input type="number" min="1" max={rows.length} step="1" value={last}
+          aria-invalid={!valid} onChange={event => {setLast(event.target.value); setPage(0); setDownloadFailed(false);}}/></label>
+        <button type="button" onClick={() => {setFirst("1"); setLast(String(rows.length)); setPage(0); setDownloadFailed(false);}}>{zh ? "全部轮次" : "All Turns"}</button>
+        <button type="button" disabled={!valid} onClick={() => {
+          try {downloadReport("selected-turn-usage.json", source.artifact_sha256,
+            exportResearchUsage(usage, Number(first), Number(last), source, new Date().toISOString())); setDownloadFailed(false);}
+          catch {setDownloadFailed(true);}
+        }}>{zh ? "下载所选用量" : "Download selected usage"}</button>
+      </div>
+      {!valid ? <p role="alert">{zh ? `请选择 1 至 ${rows.length} 轮之间的有效范围。` : `Choose a valid range between Turns 1 and ${rows.length}.`}</p> : null}
+      {selection ? <div className="research-usage-range-summary" role="status">
+        <p>{zh ? `已选 ${selection.selected_turns} / ${rows.length} 轮 · 完成 ${selection.completed_turns} 轮 · 无计数 ${selection.turns_without_counters} 轮`
+          : `${selection.selected_turns} / ${rows.length} Turns selected · ${selection.completed_turns} completed · ${selection.turns_without_counters} without counters`}
+          {source.applicability === "historical" ? (zh ? " · 历史捕获" : " · Historical capture") : ""}</p>
+        <dl>
+          <div><dt>{zh ? "已观测输入" : "Observed input"}</dt><dd>{number(selection.observed_input_tokens)}</dd></div>
+          <div><dt>{zh ? "其中缓存" : "Cached subset"}</dt><dd>{number(selection.observed_cached_input_tokens)}</dd></div>
+          <div><dt>{zh ? "未缓存" : "Uncached"}</dt><dd>{number(selection.observed_uncached_input_tokens)}</dd></div>
+          <div><dt>{zh ? "已观测输出" : "Observed output"}</dt><dd>{number(selection.observed_output_tokens)}</dd></div>
+          <div><dt>{zh ? "轮次耗时合计" : "Summed Turn time"}</dt><dd>{(selection.observed_turn_seconds / 60).toLocaleString(zh ? "zh-CN" : "en", {maximumFractionDigits: 1})} {zh ? "分钟" : "min"}</dd></div>
+        </dl>
+        <p>{zh ? "仅合计已观测计数；无计数不记零，未完成轮不代表最终用量。耗时不含轮次间空档。" : "Sums observed counters only. Missing counters are not zero; unfinished Turns are not final usage. Time excludes gaps between Turns."}</p>
+      </div> : null}
+      {downloadFailed ? <p role="alert">{zh ? "无法开始下载，请重试。" : "Could not start the download. Try again."}</p> : null}
+    </fieldset> : null}
+    {selectedRows.length ? <ol className="research-turn-cost-list">
       {ordered.slice(current * size, (current + 1) * size).map(turn => <li key={turn.turn_id}>
         <div><strong>{zh ? `第 ${turn.ordinal} 轮` : `Turn ${turn.ordinal}`}</strong>
           {turn.incomplete ? <span className="research-usage-scope">{zh ? " · 未完成（仅已观测）" : " · Incomplete (observed only)"}</span> : null}
@@ -51,7 +87,7 @@ export function ResearchTurnCosts({usage, zh, onRead}: {usage: TrajectorySolverU
         <button type="button" aria-label={zh ? `第 ${turn.ordinal} 轮：查看计数证据` : `Turn ${turn.ordinal}: read counter evidence`}
           onClick={event => onRead(turn.turn_id, event.currentTarget)}>{zh ? "计数证据" : "Counter evidence"}</button>
       </li>)}
-    </ol> : <p>{zh ? "此捕获没有可读轮次。" : "No captured Turns are available."}</p>}
+    </ol> : rows.length ? null : <p>{zh ? "此捕获没有可读轮次。" : "No captured Turns are available."}</p>}
     {pages > 1 ? <nav aria-label={zh ? "轮次分页" : "Turn pages"}>
       <button type="button" disabled={current === 0} onClick={() => setPage(current - 1)}>{zh ? "上一页" : "Previous"}</button>
       <span aria-live="polite">{current + 1} / {pages}</span>
diff --git a/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.test.mjs b/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.test.mjs
new file mode 100644
index 0000000000..50b8188cec
--- /dev/null
+++ b/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.test.mjs
@@ -0,0 +1,60 @@
+import assert from 'node:assert/strict';
+import {test} from 'node:test';
+import {selectResearchUsage, exportResearchUsage} from './research-usage-selection.ts';
+
+const turn = (n, input = 100) => ({turn_id: `turn-${n}`, start: `2026-01-01T00:${String(n).padStart(2, '0')}:00Z`,
+  end: `2026-01-01T00:${String(n).padStart(2, '0')}:10Z`, first_line: n * 3, last_line: n * 3 + 2, elapsed_seconds: 10,
+  usage: {input_tokens: input, cached_input_tokens: input / 2, uncached_input_tokens: input / 2, output_tokens: 10}});
+const usage = {session_id: 'session', method: 'codex_observed_session_counters_v1',
+  start: '2026-01-01T00:00:00Z', end: '2026-01-01T00:13:00Z', turns: Array.from({length: 12}, (_, i) => turn(i + 1)),
+  incomplete_turn: {turn_id: 'tail', start: '2026-01-01T00:13:00Z', observed_through: '2026-01-01T00:13:05Z',
+    first_line: 40, last_line: 41, counter_observations: 0, usage: null}, limitations: ['Only recorded counters.']};
+
+test('inclusive chronological selection sums independent counters and excludes inter-Turn gaps', () => {
+  const result = selectResearchUsage(usage, 2, 10);
+  assert.equal(result.selected_turns, 9);
+  assert.equal(result.observed_input_tokens, 900);
+  assert.equal(result.observed_cached_input_tokens, 450);
+  assert.equal(result.observed_uncached_input_tokens, 450);
+  assert.equal(result.observed_output_tokens, 90);
+  assert.equal(result.observed_turn_seconds, 90);
+  assert.deepEqual(result.turns.map(t => t.ordinal), [2,3,4,5,6,7,8,9,10]);
+});
+
+test('unknown, partial and measured zero remain distinct', () => {
+  const tail = selectResearchUsage(usage, 13, 13);
+  assert.equal(tail.observed_input_tokens, null);
+  assert.equal(tail.completed_turns, 0);
+  assert.equal(tail.turns_without_counters, 1);
+  assert.equal(tail.observed_turn_seconds, 5);
+  const partial = selectResearchUsage(usage, 12, 13);
+  assert.equal(partial.observed_input_tokens, 100);
+  assert.equal(partial.turns_without_counters, 1);
+  assert.equal(partial.completed_turns, 1);
+  const zero = {...usage, incomplete_turn: {...usage.incomplete_turn, counter_observations: 1,
+    usage: {input_tokens: 0, cached_input_tokens: 0, uncached_input_tokens: 0, output_tokens: 0}}};
+  assert.equal(selectResearchUsage(zero, 13, 13).observed_input_tokens, 0);
+  assert.equal(selectResearchUsage(zero, 13, 13).turns_without_counters, 0);
+});
+
+test('rejects empty, reversed, fractional and out-of-capture selections', () => {
+  for (const [first, last] of [[0,1],[2,1],[1,14],[1.5,3],[1,NaN],[1,Infinity]]) {
+    assert.throws(() => selectResearchUsage(usage, first, last), /valid captured Turn range/);
+  }
+  assert.throws(() => selectResearchUsage({...usage, turns: [], incomplete_turn: null}, 1, 1));
+});
+
+test('portable selection retains provenance and source lines beyond paging without exporting raw source', () => {
+  const source = {pack_id: 'pack', goal_id: 'goal', artifact_sha256: 'a'.repeat(64), applicability: 'historical'};
+  const before = JSON.stringify(usage);
+  const result = JSON.parse(exportResearchUsage(usage, 1, 13, source, '2026-01-02T00:00:00Z'));
+  assert.equal(result.selection.turns.length, 13);
+  assert.equal(result.selection.turns[11].first_line, 36);
+  assert.equal(result.selection.turns[12].usage, null);
+  assert.equal(result.artifact_sha256, source.artifact_sha256);
+  assert.equal(result.applicability, 'historical');
+  assert.equal(result.session_id, 'session');
+  assert.equal(result.selection.observed_input_tokens, 1200);
+  assert(result.limitations.includes(usage.limitations[0]));
+  assert.equal(JSON.stringify(usage), before);
+});
diff --git a/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.ts b/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.ts
new file mode 100644
index 0000000000..7e55de42c2
--- /dev/null
+++ b/apps/presentation/dashboard/src/features/personal-workspace/research-usage-selection.ts
@@ -0,0 +1,48 @@
+import type {TrajectorySolverUsage} from "../../../../../../loopx/control_plane/capabilities/trajectory_assessment_types.js";
+
+/** Presentation arithmetic over one already-qualified capture, not a ledger. */
+export function researchUsageRows(usage: TrajectorySolverUsage) {
+  const rows: Array<Omit<TrajectorySolverUsage["turns"][number], "usage"> & {
+    usage: TrajectorySolverUsage["turns"][number]["usage"] | null; ordinal: number; incomplete: boolean;
+  }> = usage.turns.map((turn, index) => ({...turn, ordinal: index + 1, incomplete: false}));
+  const tail = usage.incomplete_turn;
+  if (tail) rows.push({...tail, end: tail.observed_through,
+    elapsed_seconds: Math.max(0, (Date.parse(tail.observed_through) - Date.parse(tail.start)) / 1000),
+    ordinal: rows.length + 1, incomplete: true, usage: tail.usage});
+  return rows;
+}
+
+export function selectResearchUsage(usage: TrajectorySolverUsage, first: number, last: number) {
+  const all = researchUsageRows(usage);
+  if (!Number.isInteger(first) || !Number.isInteger(last) || first < 1 || last < first || last > all.length) {
+    throw new Error("Select a valid captured Turn range");
+  }
+  const turns = all.slice(first - 1, last);
+  const observed = turns.filter(turn => turn.usage !== null);
+  const sum = (key: keyof NonNullable<typeof turns[number]["usage"]>) => observed.length
+    ? observed.reduce((total, turn) => total + turn.usage![key], 0) : null;
+  return {
+    first_turn: first, last_turn: last, captured_turns: all.length,
+    selected_turns: turns.length, completed_turns: turns.filter(turn => !turn.incomplete).length,
+    turns_without_counters: turns.length - observed.length,
+    observed_input_tokens: sum("input_tokens"), observed_cached_input_tokens: sum("cached_input_tokens"),
+    observed_uncached_input_tokens: sum("uncached_input_tokens"), observed_output_tokens: sum("output_tokens"),
+    // Sum observed intervals; gaps between Turns are not execution time.
+    observed_turn_seconds: turns.reduce((total, turn) => total + turn.elapsed_seconds, 0),
+    start: turns[0].start, observed_through: turns.at(-1)!.end, turns,
+  };
+}
+
+export function exportResearchUsage(usage: TrajectorySolverUsage, first: number, last: number,
+  source: {pack_id: string; goal_id: string; artifact_sha256: string; applicability: "current" | "historical"},
+  exportedAt: string) {
+  return JSON.stringify({
+    ...source, exported_at: exportedAt, session_id: usage.session_id, method: usage.method,
+    capture_start: usage.start, capture_end: usage.end,
+    selection: selectResearchUsage(usage, first, last),
+    limitations: [...usage.limitations,
+      "Observed counters from one capture, not complete study or monetary cost. Missing counters are null, not zero.",
+      "Elapsed intervals include tools and waiting. This selection does not establish avoidable cost or causal benefit.",
+      "Do not add overlapping captures or separate request-reconciliation counters to these totals."],
+  }, null, 2) + "\n";
+}
diff --git a/docs/reference/trajectory-assessment.md b/docs/reference/trajectory-assessment.md
index 542d31ee87..1982320df8 100644
--- a/docs/reference/trajectory-assessment.md
+++ b/docs/reference/trajectory-assessment.md
@@ -1004,6 +1004,39 @@ TypeScript reducer retain ownership, with Python restricted to scoped file
 reading and transport. There is no new telemetry, accounting store or scoring
 policy.
 
+### Inspect and save a Turn range
+
+In Research → Sources and usage → **Find time and input hotspots**, enter the
+first and last chronological Turn numbers to inspect a contiguous portion of the
+selected capture. Sorting changes only the display order; it does not change
+range membership. **All Turns** restores the capture. The summary reports
+selected/completed Turns, missing counter coverage, observed input (including
+its cached subset), output and summed observed Turn intervals. Gaps between
+Turns are excluded from that elapsed sum. Unknown counters stay unknown; an
+unfinished Turn remains incomplete even when some counters are available.
+
+**Download selected usage** saves every selected Turn, including rows beyond the
+current page, as JSON. The file retains the Goal, pack, session, source SHA-256,
+method, capture window, historical/current applicability, original source line
+ranges and limitations. It contains captured counters rather than raw messages
+or a source filesystem location. A failed download can be retried without
+changing the selection or Goal state. Changing the pack/source digest resets
+the range so a previous selection cannot silently refer to different evidence.
+
+This local reading operation needs no model call, new activation, server write
+or CLI/Lark configuration. Close the disclosure to leave the workflow. The file
+is a portable reading snapshot, not an import, billing or acceptance receipt.
+Do not combine overlapping captures, treat partial observations as final costs,
+or infer monetary savings or comparable outcomes from the selected sums.
+
+在研究页的「来源与用量」→「定位耗时与输入最多的轮次」中，输入起止轮次，
+查看同一捕获内连续范围的已观测用量。排序只改变显示顺序；「全部轮次」恢复全量。
+汇总保留完成状态与无计数覆盖，缺失不记零，未完成轮不当作最终用量；耗时合计不含
+轮次间空档。「下载所选用量」导出跨分页的完整所选计数、来源摘要、行号与适用性，
+不导出原始消息或本机路径。下载失败可原地重试，切换捕获或来源摘要会重置范围。
+该操作不调用模型、不写入 Goal，也不增加 CLI/Lark 配置；关闭详情即可退出。
+导出是阅读快照，不是账单、导入或验收凭据，不能据此推断金额、节省或因果收益。
+
 ### Reconcile request and compaction coverage
 
 New usage captures also inspect persisted Codex `token_usage_record` and
diff --git a/examples/personal-workspace-browser/research-turn-costs.mjs b/examples/personal-workspace-browser/research-turn-costs.mjs
index 400be9d5be..95c7a07f8c 100644
--- a/examples/personal-workspace-browser/research-turn-costs.mjs
+++ b/examples/personal-workspace-browser/research-turn-costs.mjs
@@ -1,6 +1,6 @@
 import assert from 'node:assert/strict';
 import {execFileSync} from 'node:child_process';
-import {mkdtemp, rm} from 'node:fs/promises';
+import {mkdtemp, readFile, rm} from 'node:fs/promises';
 import {tmpdir} from 'node:os';
 import {resolve} from 'node:path';
 import {resolveTestPython} from '../../scripts/test-python.mjs';
@@ -79,6 +79,42 @@ Path(sys.argv[1]).write_text(json.dumps(dict(goal_id=goal,display_name='Syntheti
       assert.match(await source.innerText(), /unfinished/);
       await source.getByRole('button', {name: '关闭原文', exact: true}).click();
       await costs.getByRole('combobox').selectOption('input');
+      const firstTurn = costs.getByRole('spinbutton', {name: '起始轮次', exact: true});
+      const lastTurn = costs.getByRole('spinbutton', {name: '结束轮次', exact: true});
+      const selection = costs.locator('.research-usage-range-summary');
+      assert.match(await selection.innerText(), /已选 11 \/ 11 轮.*完成 10 轮.*无计数 1 轮/);
+      const download = async () => {
+        const waiting = page.waitForEvent('download');
+        await costs.getByRole('button', {name: '下载所选用量', exact: true}).click();
+        const file = await waiting;
+        return JSON.parse(await readFile(await file.path(), 'utf8'));
+      };
+      const all = await download();
+      assert.equal(all.selection.turns.length, 11, 'Download includes every selected Turn beyond the eight-row page');
+      assert.equal(all.selection.observed_input_tokens, 5900);
+      assert.equal(all.goal_id, 'synthetic-cost-study');
+      assert.equal(all.artifact_sha256.length, 64);
+      assert.ok(!JSON.stringify(all).includes('SENSITIVE_TEXT_NOT_FOR_BROWSER'));
+      await firstTurn.fill('3'); await lastTurn.fill('7');
+      assert.equal(await items.count(), 5);
+      assert.match(await selection.innerText(), /5,400/);
+      const range = await download();
+      assert.deepEqual(range.selection.turns.map(turn => turn.turn_id), ['turn-3','turn-4','turn-5','turn-6','turn-7']);
+      assert.equal(range.selection.observed_turn_seconds, 134);
+      await firstTurn.fill('11'); await lastTurn.fill('11');
+      assert.match(await selection.innerText(), /完成 0 轮.*无计数 1 轮/);
+      assert.equal((await download()).selection.observed_input_tokens, null);
+      await firstTurn.fill('12');
+      assert.equal(await costs.getByRole('button', {name: '下载所选用量', exact: true}).isDisabled(), true);
+      await costs.getByRole('alert').waitFor();
+      await costs.getByRole('button', {name: '全部轮次', exact: true}).click();
+      // A browser download failure can be retried without losing the selection.
+      await page.evaluate(() => {window.savedUsageCreateURL = URL.createObjectURL; URL.createObjectURL = () => {throw new Error('synthetic download failure');};});
+      await costs.getByRole('button', {name: '下载所选用量', exact: true}).click();
+      assert.match(await costs.getByRole('alert').innerText(), /无法开始下载/);
+      await page.evaluate(() => {URL.createObjectURL = window.savedUsageCreateURL; delete window.savedUsageCreateURL;});
+      assert.equal((await download()).selection.turns.length, 11);
+      assert.equal(await costs.getByRole('alert').count(), 0);
       const helpButton = costs.getByRole('button', {name: '轮次耗时与输入说明', exact: true});
       const helpPopover = costs.locator('.context-help-popover');
       await helpButton.focus();
@@ -102,7 +138,26 @@ Path(sys.argv[1]).write_text(json.dumps(dict(goal_id=goal,display_name='Syntheti
         await page.keyboard.press('Escape');
         await helpPopover.waitFor({state: 'hidden'});
         assert.equal(await helpButton.evaluate(element => element === document.activeElement), true);
+        await costs.locator('legend').evaluate(element => element.scrollIntoView({block: 'center'}));
+        await page.screenshot({path: resolve(outputDir, `research-usage-range-${width}.png`), animations: 'disabled'});
       }
+      await page.evaluate(() => localStorage.setItem('loopx-pw-locale', 'en'));
+      await page.reload({waitUntil: 'networkidle'});
+      await progress.locator('.research-progress-basis').waitFor();
+      if (!await progress.locator('.research-progress-basis').evaluate(element => element.open)) {
+        await progress.locator('.research-progress-basis > summary').focus(); await page.keyboard.press('Enter');
+      }
+      await costs.locator('summary').click();
+      await costs.getByRole('spinbutton', {name: 'First Turn', exact: true}).fill('3');
+      await costs.getByRole('spinbutton', {name: 'Last Turn', exact: true}).fill('7');
+      assert.match(await selection.innerText(), /5 \/ 11 Turns selected.*5 completed.*0 without counters/);
+      assert.match(await selection.innerText(), /5,400/);
+      const englishDownload = page.waitForEvent('download');
+      await costs.getByRole('button', {name: 'Download selected usage', exact: true}).click();
+      assert.equal(JSON.parse(await readFile(await (await englishDownload).path(), 'utf8')).selection.observed_input_tokens, 5400);
+      assert(await page.evaluate(() => document.documentElement.scrollWidth <= innerWidth + 1));
+      await costs.locator('legend').evaluate(element => element.scrollIntoView({block: 'center'}));
+      await page.screenshot({path: resolve(outputDir, 'research-usage-range-en-390.png'), animations: 'disabled'});
       assert.deepEqual(errors, []);
       assert.deepEqual(writes, [], 'Cost inspection never starts analysis or mutates Goal state');
       return {coverageEntries: [], note: 'Real registered capture, typed reduction, HTTP and source UI: sort, pagination, incomplete/unknown counters, accessible contextual help, exact source evidence, keyboard return and mobile. No model or live benchmark.'};