diff --git a/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.i18n.yaml b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.i18n.yaml
new file mode 100644
index 0000000000..18ed791f68
--- /dev/null
+++ b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.i18n.yaml
@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# side as of the last confirmed-consistent state. Both languages carry equal authority;
+# after editing either side, bring the other along and re-record with:
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.md
+2026-08-12-full-session-turn-step-counts.md: ecfa00dc3e24101953a9d5a724dba17682d839bd
+2026-08-12-full-session-turn-step-counts.zh.md: 85e2a26b5af51296e20f29af49e909c6e182ea05
diff --git a/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.md b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.md
new file mode 100644
index 0000000000..ecfa00dc3e
--- /dev/null
+++ b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.md
@@ -0,0 +1,38 @@
+# Agent Note: Full-session stats-strip figures through a sessionStats projection
+
+Status: implemented
+
+English | [中文](2026-08-12-full-session-turn-step-counts.zh.md)
+
+## Problem
+
+The web chat stats strip folded `StatsLine`'s loaded conversation window (`deriveStats` over `chat.legacy.nodes`) for every non-token figure: the "N turns · M steps" counter, the LLM and tool wall times, and the TTFT/throughput averages. History is paged 50 messages at a time, so each 加载更早 (Load earlier) click grew the window and every figure with it — 7 turns · 44 steps became 10 turns · 89 steps after one page, and the LLM duration climbed the same way. The product expectation is whole-session figures independent of how much history a client has loaded. Token accounting in the same strip already had the correct architecture: the durable `tokenUsage` projection.
+
+## Decision
+
+A new function plugin `@deepseek-ai/dsh-session-stats` registers a `sessionStats` projection unit on `ctx.sessionProjections`, mounted as a web-app bundle row. The value carries the strip's whole non-token figure set — `{ turns, steps, llmMs, toolMs, ttftMs, ttftSteps, decodeMs, decodeTokens }`, field names mirroring the window fold so the two swap wholesale. `steps` counts `step/end` events and `turns` counts distinct turns carrying at least one (turn numbers are monotonic, so one `lastTurn` slot suffices); `llmMs` sums `step/start` → `assistant/message`; TTFT records the first non-empty delta chunk per step (surviving in-step `llm/retry`, the window `resetForRetry` parity); decode spans first token → assembled message on usage-reporting steps; `toolMs` pairs `tool/call` → `tool/result` by callId with unresolved calls dropped at `turn/end`. The first-token predicate `isTokenDelta` moved to `@deepseek-ai/dsh-llm/message` (beside the `StreamChunk` type it discriminates) so the host fold and the client timing index share one implementation; client-runtime re-exports it. Delivery is entirely the existing projection seam — history tail-page block, `session/projection` push frames, list rows — with zero changes to apiproxy, wire schemas, or the client runtime. `StatsLine` reads `useProjection('sessionStats')` and falls back to the window fold when the key is undefined (an assembly without the unit). The client connection fixture mirrors the fold as `sessionStatsOf` under its existing every-composed-key discipline.
+
+`step/end` — not `assistant/message` — is the counted event, for two correctness reasons found while reviewing the obvious message-counting design:
+
+1. A max-tokens step appends an empty-content `assistant/message` that exists only to host usage and never reaches the surface; counting messages would count a step the transcript does not show.
+2. A cancelled step aborts before its message assembles (no `assistant/message` at all), yet the client synthesizes a visible interrupted assistant node; counting messages would silently drop common cancelled steps.
+
+`step/end` is appended exactly once per entered step, in the loop's `finally`, so completed, failed, cancelled, and max-tokens steps all land one — and the counter advances at step settlement, the same moment the window fold advanced, so live behavior does not shift.
+
+## Alternatives considered
+
+**Count `assistant/message` events.** Rejected for the two correctness defects above (overcounts usage-host messages, undercounts cancelled steps).
+
+**Count `step/start` events.** Equivalent coverage (it precedes every `step/end`), but the counter would advance when a step begins instead of when it settles — a visible live-behavior change with no benefit; `step/end`'s `finally` placement gives the same completeness.
+
+**Register the unit in `core/agent-loop` (the event producer).** The loop is the product spine; a UI read model there adds a session-projection dependency to every assembly, against "plugins, not loop changes" and "keep opt-ins out of shipped defaults".
+
+**Register the unit in `token-meter` (an existing fold over the same events).** Turn/step counting is not token measurement; every projection key lives in the package owning its domain.
+
+**Fold the full log client-side.** The client holds only the paged window by design; the projection RFC's no-client-folding rule exists exactly so figures survive paging, compaction, and cold reads.
+
+**Keep wall times, TTFT, and throughput window-scoped, reading them as "what is on screen".** Rejected: the same paging complaint applies to the LLM duration, and a strip mixing whole-log counts with window-scoped times reads as one inconsistent figure set. The projection carries the whole set, with the window fold demoted to the no-unit fallback.
+
+## Consequences
+
+The strip shows whole-log figures from the first tail page; paging leaves every group fixed. Defined edge differences from the old window semantics are documented in the package README: a step that produced no visible output (failed before content) still counts, a step interrupted by a crash counts once recovery closes it with a synthetic `step/end` on reload (`interruptedTurnClosers`), a cancelled step is counted but contributes no wall time (no message assembled), and a max-tokens usage-host message contributes model time the surface does not show. Every web tail page and list row carries one more small key, and the unit's internal state changes on step boundaries and first-token chunks, so the change feed emits a few value-identical frames per step; TUI and headless assemblies serve no `sessionStats` key and any consumer falls back to window folding. Two e2e probes that had parsed the strip as a loaded-window measure (`chat-scroll-contract`, `complex-history.perf`) now count mounted flow rows / turn-tail footers instead. The `stats-paged-history` web scenario seeds a 28-turn log cold and pins that the whole strip reads full totals on a partial tail page and does not move across Load earlier.
diff --git a/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.zh.md b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.zh.md
new file mode 100644
index 0000000000..85e2a26b5a
--- /dev/null
+++ b/.agents/notes/implemented/bug-fix/2026-08-12-full-session-turn-step-counts.zh.md
@@ -0,0 +1,38 @@
+# Agent Note: 通过 sessionStats 投影提供全会话统计条数字
+
+Status: implemented
+
+[English](2026-08-12-full-session-turn-step-counts.md) | 中文
+
+## 问题
+
+Web 聊天统计条的每个非 token 数字都折算自 `StatsLine` 已加载的会话窗口（`deriveStats` 遍历 `chat.legacy.nodes`）：「N 轮 · M 步」计数、LLM 与工具墙钟时间、TTFT／吞吐平均值。历史按每页 50 条消息分页，因此每点一次「加载更早」窗口变大、所有数字随之增长——7 轮 · 44 步在翻一页后变成 10 轮 · 89 步，LLM 时长同样攀升。产品预期是与客户端加载了多少历史无关的全会话数字。同一统计条里的 token 账目早已采用正确架构：持久的 `tokenUsage` 投影。
+
+## 决定
+
+新的函数插件 `@deepseek-ai/dsh-session-stats` 在 `ctx.sessionProjections` 上注册 `sessionStats` 投影单元，作为 web-app bundle 行挂载。值携带统计条完整的非 token 数字集——`{ turns, steps, llmMs, toolMs, ttftMs, ttftSteps, decodeMs, decodeTokens }`，字段名与窗口折叠一一对应以便整体互换。`steps` 统计 `step/end` 事件，`turns` 统计含至少一条该事件的不同 turn（turn 号单调递增，一个 `lastTurn` 槽即可）；`llmMs` 累加 `step/start` → `assistant/message`；TTFT 记录每步首个非空 delta chunk（在步内 `llm/retry` 后保留，与窗口 `resetForRetry` 对齐）；解码时长覆盖首 token → 已组装消息、仅统计上报 usage 的步；`toolMs` 按 callId 配对 `tool/call` → `tool/result`，未解决的调用在 `turn/end` 时丢弃。首 token 谓词 `isTokenDelta` 移入 `@deepseek-ai/dsh-llm/message`（与其判别的 `StreamChunk` 类型同处），Host 折叠与客户端计时索引共用同一实现；client-runtime 转发导出。投递完全复用现有投影缝——history 尾页块、`session/projection` 推送帧、列表行——apiproxy、wire schema 与客户端运行时零改动。`StatsLine` 读取 `useProjection('sessionStats')`，键为 undefined（未组合该单元的装配）时整体回退到窗口折叠。客户端 connection fixture 按其「镜像每个已组合键」的既有纪律以 `sessionStatsOf` 平行实现该折叠。
+
+计数事件选 `step/end` 而非 `assistant/message`，源于评审直觉方案（按消息计数）时发现的两个正确性问题：
+
+1. max-tokens 步会追加一条仅为承载 usage 而存在的空内容 `assistant/message`，它从不进入 surface；按消息计数会把 transcript 上看不到的步计进去。
+2. 被取消的步在消息组装前就中止（完全没有 `assistant/message`），但客户端会合成可见的 interrupted assistant 节点；按消息计数会悄悄丢掉常见的取消步。
+
+`step/end` 对每个进入的步在循环的 `finally` 中恰好追加一次，因此完成、失败、取消、max-tokens 的步都恰好落一条——且计数在步结算时推进，与窗口折算推进的时机相同，直播期行为不发生变化。
+
+## 备选方案
+
+**统计 `assistant/message` 事件。** 因上述两个正确性缺陷否决（多计 usage 宿主消息、少计被取消的步）。
+
+**统计 `step/start` 事件。** 覆盖等价（它先于每条 `step/end`），但计数会在步开始而非结算时推进——一个没有收益的可见直播期行为变化；`step/end` 的 `finally` 位置给出同等完整性。
+
+**把单元注册进 `core/agent-loop`（事件生产方）。** 循环是产品主干；把 UI 读模型放进去会给每个装配加上 session-projection 依赖，违反「用插件而非改循环」与「默认组合不带可选项」。
+
+**把单元注册进 `token-meter`（折叠同批事件的现有单元）。** 轮/步计数不是 token 度量；每个投影键都住在拥有其领域的包里。
+
+**在客户端折叠全量日志。** 客户端按设计只持有分页窗口；投影 RFC 的「不在客户端折叠」规则正是为了让数字在分页、压缩与冷读之间存活。
+
+**墙钟时间、TTFT 与吞吐保持窗口口径，解读为「屏幕上有什么」。** 否决：同样的分页问题一样落在 LLM 时长上，且全量计数与窗口时间混在一条统计条里读起来是一套自相矛盾的数字。投影携带完整集合，窗口折叠降级为无单元时的回退。
+
+## 后果
+
+统计条从第一个尾页起就显示全日志数字；翻页不再改变任何分组。与旧窗口语义的已定义边缘差异记录在包 README 中：未产生可见输出的步（在内容之前失败）仍计入；被崩溃打断的步在重新加载、恢复为其补写合成 `step/end` 后计入（`interruptedTurnClosers`）；被取消的步计数但不计时（没有组装出消息）；max-tokens 的 usage 宿主消息贡献 surface 上看不到的模型时间。每个 web 尾页与列表行多携带一个小键，且单元内部状态在步边界与首 token chunk 处变化，变更流每步会多发几帧值相同的推送；TUI 与 headless 装配不提供 `sessionStats` 键，其消费者回退窗口折叠。两个曾把统计条当作已加载窗口探针解析的 e2e（`chat-scroll-contract`、`complex-history.perf`）改为统计已挂载的消息流行／turn-tail 页脚。`stats-paged-history` web 场景冷种一份 28 轮日志，钉住整条统计条在不完整尾页上即读出全量数字、且「加载更早」前后不变。
diff --git a/apps/web/tests/chat-scroll-contract.e2e.ts b/apps/web/tests/chat-scroll-contract.e2e.ts
index 5274759f47..6ce469a9c0 100644
--- a/apps/web/tests/chat-scroll-contract.e2e.ts
+++ b/apps/web/tests/chat-scroll-contract.e2e.ts
@@ -250,13 +250,16 @@ function scrollGeometry(page: Page): Promise<ScrollGeometry> {
   }))
 }
 
-async function conversationTurns(page: Page): Promise<number> {
-  const stats = page.getByText(/\d+ turns · \d+ steps/, { exact: true }).last()
-  await stats.waitFor({ timeout: 15_000 })
-  const value = await stats.textContent()
-  const match = value?.match(/^(\d+) turns · \d+ steps$/)
-  if (match?.[1] === undefined) throw new Error(`unexpected conversation stats ${JSON.stringify(value)}`)
-  return Number(match[1])
+/**
+ * Rendered transcript rows in the loaded window. The stats strip cannot serve
+ * as this probe: its turn/step counts ride the whole-log sessionStats
+ * projection and stay fixed across paging by design, while the row count is
+ * exactly what grows when an older page prepends or a live turn streams in.
+ * @param page - the scenario page.
+ * @returns the number of mounted chat flow rows.
+ */
+async function loadedFlowRows(page: Page): Promise<number> {
+  return page.locator('[data-chat-flow-key]').count()
 }
 
 async function openSeed(page: Page, fixture: ChatScrollFixture, tailMarker?: string): Promise<void> {
@@ -425,9 +428,9 @@ async function loadEarlierWithAnchor(page: Page): Promise<void> {
   const older = page.getByRole('button', { name: 'Load earlier', exact: true })
   await older.waitFor({ timeout: 10_000 })
   const anchor = await visibleFlowAnchor(page)
-  const before = await conversationTurns(page)
+  const before = await loadedFlowRows(page)
   await older.click()
-  await expect.poll(() => conversationTurns(page), { timeout: 30_000 }).toBeGreaterThan(before)
+  await expect.poll(() => loadedFlowRows(page), { timeout: 30_000 }).toBeGreaterThan(before)
   await nextPaint(page)
   await expectSameFlowTop(page, anchor)
 }
@@ -498,7 +501,7 @@ describe('web e2e: long Chat scroll contract', () => {
         await world.page.getByRole('button', { name: 'Send message', exact: true }).click()
         await world.page.getByText(LIVE_TEXT_FIRST, { exact: false }).last().waitFor({ timeout: 15_000 })
         await wheelToHistoryStart(world.page)
-        const beforeTurns = await conversationTurns(world.page)
+        const beforeRows = await loadedFlowRows(world.page)
         await world.page.getByRole('button', { name: 'Load earlier', exact: true }).click()
         await expect.poll(() => held, { timeout: 10_000 }).toBe(true)
 
@@ -511,7 +514,7 @@ describe('web e2e: long Chat scroll contract', () => {
         ).toBeGreaterThan(chunksAfterAnchor + 5)
 
         releaseHistory()
-        await expect.poll(() => conversationTurns(world.page), { timeout: 30_000 }).toBeGreaterThan(beforeTurns)
+        await expect.poll(() => loadedFlowRows(world.page), { timeout: 30_000 }).toBeGreaterThan(beforeRows)
         await nextPaint(world.page)
         await expectSameFlowTop(world.page, readerAnchor)
       } finally {
@@ -531,7 +534,11 @@ describe('web e2e: long Chat scroll contract', () => {
         additionalPages += 1
       }
       expect(additionalPages).toBeGreaterThan(0)
-      expect(await conversationTurns(world.page)).toBe(HISTORY_FIXTURE.turns + 1)
+      // The whole log is loaded: turn 1's unique marker renders in the
+      // transcript (scoped: the sidebar search row also carries it) and no
+      // page remains.
+      expect(await world.page.locator('[data-conversation-scroll]')
+        .getByText(HISTORY_FIXTURE.markers.user(1), { exact: false }).count()).toBe(1)
       expect(await world.page.getByRole('button', { name: 'Load earlier', exact: true }).count()).toBe(0)
       assertClean(world)
     })
diff --git a/apps/web/tests/complex-history.perf.ts b/apps/web/tests/complex-history.perf.ts
index d3c27f0ce0..eeb9931473 100644
--- a/apps/web/tests/complex-history.perf.ts
+++ b/apps/web/tests/complex-history.perf.ts
@@ -797,12 +797,11 @@ async function stableCount(
 }
 
 async function conversationTurns(page: Page): Promise<number> {
-  const stats = page.getByText(/\d+ turns · \d+ steps/, { exact: true }).last()
-  await stats.waitFor({ timeout: 15_000 })
-  const value = await stats.textContent()
-  const match = value?.match(/^(\d+) turns · \d+ steps$/)
-  if (match?.[1] === undefined) throw new Error(`unexpected conversation stats ${JSON.stringify(value)}`)
-  return Number(match[1])
+  // Loaded-window turn count: one mounted turn-tail footer per settled turn in
+  // the window (context keys are `${kind.length}:${kind}${id}`). The stats
+  // strip cannot serve as this probe: its counts ride the whole-log
+  // sessionStats projection and stay fixed across paging by design.
+  return stableCount(page.locator('[data-chat-flow-key^="9:turn-tail"]'), count => count > 0)
 }
 
 function retainedDelta(
diff --git a/apps/web/tests/math-rendering.e2e.ts b/apps/web/tests/math-rendering.e2e.ts
index de24c1ca76..67af32373c 100644
--- a/apps/web/tests/math-rendering.e2e.ts
+++ b/apps/web/tests/math-rendering.e2e.ts
@@ -120,7 +120,7 @@ describe('web e2e: settled Markdown math rendering', () => {
     await expect.poll(() => page.locator('.katex-display').count(), { timeout: 10_000 }).toBe(2)
     expect(await page.locator('.katex-error').count()).toBe(0)
     await expect.poll(
-      () => page.getByText('Input 0 tok · Output 0 tok', { exact: false }).count(),
+      () => page.getByText('1 turns · 1 steps', { exact: false }).count(),
       { timeout: 10_000 },
     ).toBe(1)
 
diff --git a/apps/web/tests/seeded-history.e2e.ts b/apps/web/tests/seeded-history.e2e.ts
index 9ec978fb97..a385059cf6 100644
--- a/apps/web/tests/seeded-history.e2e.ts
+++ b/apps/web/tests/seeded-history.e2e.ts
@@ -256,6 +256,12 @@ describe('web e2e: seeded history renders through cold resume', () => {
     // client's "omitted key = capability absent → clear the row" rule from
     // wiping preset-owned projections on cold reads.
     expect(projections?.values).toHaveProperty('todos', null)
+    // The session-stats unit is a shipped web-app bundle row: whole-log
+    // turn/step counts ride the same tail block (the stats strip's source).
+    const sessionStats = projections?.values.sessionStats as { turns: number; steps: number } | undefined
+    expect(sessionStats).toBeDefined()
+    expect(sessionStats?.turns).toBeGreaterThanOrEqual(1)
+    expect(sessionStats?.steps).toBeGreaterThanOrEqual(sessionStats?.turns ?? 0)
   })
 
   it.skipIf(MODE === 'record')('lists the seeded session cold and renders its history from the log', async () => {
diff --git a/apps/web/tests/snapshots/live-interactions/cancel.expected.md b/apps/web/tests/snapshots/live-interactions/cancel.expected.md
index 4ea903679c..bafa739a58 100644
--- a/apps/web/tests/snapshots/live-interactions/cancel.expected.md
+++ b/apps/web/tests/snapshots/live-interactions/cancel.expected.md
@@ -31,4 +31,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps
diff --git a/apps/web/tests/snapshots/live-interactions/error-auth.expected.md b/apps/web/tests/snapshots/live-interactions/error-auth.expected.md
index 56f87071a4..341ddf22db 100644
--- a/apps/web/tests/snapshots/live-interactions/error-auth.expected.md
+++ b/apps/web/tests/snapshots/live-interactions/error-auth.expected.md
@@ -27,3 +27,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
+- text: 1 turns · 1 steps
diff --git a/apps/web/tests/snapshots/markdown-cjk-strong/ui.expected.md b/apps/web/tests/snapshots/markdown-cjk-strong/ui.expected.md
index dbaca89b8a..adae2f723e 100644
--- a/apps/web/tests/snapshots/markdown-cjk-strong/ui.expected.md
+++ b/apps/web/tests/snapshots/markdown-cjk-strong/ui.expected.md
@@ -53,4 +53,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps LLM {{duration}} Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps LLM {{duration}}
diff --git a/apps/web/tests/snapshots/markdown-images/ui.expected.md b/apps/web/tests/snapshots/markdown-images/ui.expected.md
index f90d10f616..85c537bb18 100644
--- a/apps/web/tests/snapshots/markdown-images/ui.expected.md
+++ b/apps/web/tests/snapshots/markdown-images/ui.expected.md
@@ -32,4 +32,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps LLM {{duration}} Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps LLM {{duration}}
diff --git a/apps/web/tests/snapshots/markdown-inline-code-links/ui.expected.md b/apps/web/tests/snapshots/markdown-inline-code-links/ui.expected.md
index f345357f1b..d940beabc9 100644
--- a/apps/web/tests/snapshots/markdown-inline-code-links/ui.expected.md
+++ b/apps/web/tests/snapshots/markdown-inline-code-links/ui.expected.md
@@ -44,4 +44,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps LLM {{duration}} Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps LLM {{duration}}
diff --git a/apps/web/tests/snapshots/math-rendering/ui.expected.md b/apps/web/tests/snapshots/math-rendering/ui.expected.md
index 0bb9a9b19b..5561c3574e 100644
--- a/apps/web/tests/snapshots/math-rendering/ui.expected.md
+++ b/apps/web/tests/snapshots/math-rendering/ui.expected.md
@@ -48,4 +48,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps LLM {{duration}} Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps LLM {{duration}}
diff --git a/apps/web/tests/snapshots/queue-actions/preserved.expected.md b/apps/web/tests/snapshots/queue-actions/preserved.expected.md
index 7951af37e4..43c9665ac1 100644
--- a/apps/web/tests/snapshots/queue-actions/preserved.expected.md
+++ b/apps/web/tests/snapshots/queue-actions/preserved.expected.md
@@ -50,4 +50,4 @@
   - text: DeepSeek-V4-Flash
   - img
 - button "Send message" [disabled]
-- text: 1 turns · 1 steps Input 0 tok · Output 0 tok
+- text: 1 turns · 1 steps
diff --git a/apps/web/tests/snapshots/stats-paged-history/ui.expected.md b/apps/web/tests/snapshots/stats-paged-history/ui.expected.md
new file mode 100644
index 0000000000..78d175af5d
--- /dev/null
+++ b/apps/web/tests/snapshots/stats-paged-history/ui.expected.md
@@ -0,0 +1,357 @@
+- banner:
+  - navigation "Session hierarchy":
+    - button "{{workspace}}" [disabled]
+  - button "Session log":
+    - text: Session log
+    - img
+  - tablist:
+    - tab "Chat" [selected]
+    - tab "Trajectory"
+- text: m1 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r1
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m2 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r2
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m3 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r3
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m4 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r4
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m5 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r5
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m6 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r6
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m7 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r7
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m8 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r8
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m9 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r9
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m10 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r10
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m11 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r11
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m12 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r12
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m13 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r13
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m14 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r14
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m15 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r15
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m16 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r16
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m17 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r17
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m18 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r18
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m19 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r19
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m20 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r20
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m21 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r21
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m22 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r22
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m23 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r23
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m24 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r24
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m25 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r25
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m26 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r26
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m27 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r27
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}} m28 7/25 {{clock}}
+- button "Copy":
+  - img
+- paragraph: r28
+- button "Copy":
+  - img
+- button "Good response":
+  - img
+- button "Bad response":
+  - img
+- button "Branch into a new conversation":
+  - img
+- text: 7/25 {{clock}} Ran for {{duration}}
+- button "Back to bottom":
+  - img
+- textbox "Message the agent"
+- button "Commands":
+  - img
+- 'button "Access mode, current: Workspace Write"': Workspace Write
+- button "Select model, current DeepSeek-V4-Flash":
+  - text: DeepSeek-V4-Flash
+  - img
+- button "Send message" [disabled]
+- text: 28 turns · 28 steps LLM {{duration}}
diff --git a/apps/web/tests/stats-paged-history.e2e.ts b/apps/web/tests/stats-paged-history.e2e.ts
new file mode 100644
index 0000000000..e7ce2cdd06
--- /dev/null
+++ b/apps/web/tests/stats-paged-history.e2e.ts
@@ -0,0 +1,136 @@
+// Web e2e scenario: full-session stats over paged history. A deterministic
+// 28-turn log (56 surface messages — more than one 50-message history page)
+// seeded cold through the REAL persistence API must render whole-log turn/step
+// counts from the sessionStats projection on first open, and loading the
+// older page must NOT change them. This pins the bug the projection fixed:
+// the pre-projection window fold recounted per loaded page, so 加载更早 grew
+// the counter. Zero model calls; the seed is generated, not recorded, because
+// no line of it is model output.
+import { fileURLToPath } from 'node:url'
+import type { Browser, Page } from 'playwright'
+import { chromium } from 'playwright'
+import { afterAll, beforeAll, describe, expect, it, onTestFailed } from 'vitest'
+import {
+  assertFixtureInventory, captureStableAria, compareOrRefreshGolden,
+  launchWebScaffold, seedSession, watchConsole, webSnapshotMode, type WebScaffold,
+} from './scaffold.ts'
+import { newEnglishPage, saveFailureShot } from './support.ts'
+
+const SNAPSHOT_DIR = fileURLToPath(new URL('./snapshots/stats-paged-history', import.meta.url))
+const UI_EXPECTED = fileURLToPath(new URL('./snapshots/stats-paged-history/ui.expected.md', import.meta.url))
+const MODE = webSnapshotMode()
+const SEED_ID = 'stats-paged-history-web-e2e'
+
+/** Turn count: 2 surface messages per turn, so 28 turns overflow one 50-message page. */
+const TURNS = 28
+const FULL_COUNTS = `${TURNS} turns · ${TURNS} steps`
+
+/**
+ * Generate the seed: TURNS closed single-step turns of one short user prompt
+ * and one short assistant reply each. Times are fixed so the fixture is
+ * byte-deterministic; message ids are synthetic uuids (aria normalizes them).
+ * @param turns - closed turns to generate.
+ * @returns session.jsonl text for {@link seedSession}.
+ */
+function buildSeed(turns: number): string {
+  const lines = [JSON.stringify({
+    type: 'session', version: 0, id: '{{sessionId}}', createdAt: 1784974100000, cwd: '{{cwd}}/workspace',
+  })]
+  let seq = 0
+  let time = 1784974100000
+  const at = (event: Record<string, unknown>): void => {
+    lines.push(JSON.stringify({ ...event, seq: seq++, time: time++ }))
+  }
+  for (let turn = 1; turn <= turns; turn++) {
+    at({ type: 'turn/start', data: { turn } })
+    at({
+      type: 'user/message',
+      data: { content: [{ type: 'text', text: `m${turn}` }], source: { kind: 'user' } },
+      surfaceOp: 'append',
+    })
+    at({ type: 'step/start', data: { turn, step: 1 } })
+    at({
+      type: 'assistant/message',
+      data: {
+        turn,
+        step: 1,
+        message: {
+          id: `00000000-0000-4000-8000-${String(turn).padStart(12, '0')}`,
+          role: 'assistant',
+          content: [{ type: 'text', text: `r${turn}` }],
+          source: { kind: 'model', provider: 'snapshot', model: 'snapshot-replier' },
+        },
+      },
+      sourceEventSeqs: [],
+      surfaceOp: 'append',
+    })
+    at({ type: 'step/end', data: { turn, step: 1 } })
+    at({ type: 'turn/end', data: { turn, reason: { kind: 'completed' } } })
+  }
+  return `${lines.join('\n')}\n`
+}
+
+describe('web e2e: whole-session stats survive history paging', () => {
+  let scaffold: WebScaffold
+  let browser: Browser
+  let page: Page
+  let tripwire: ReturnType<typeof watchConsole>
+
+  beforeAll(async () => {
+    if (MODE === 'record') throw new Error('stats-paged-history is a keyless assembled snapshot')
+    scaffold = await launchWebScaffold({})
+    await seedSession(scaffold, buildSeed(TURNS), SEED_ID)
+    browser = await chromium.launch()
+    page = await newEnglishPage(browser)
+    tripwire = watchConsole(page)
+    await page.goto(scaffold.baseUrl, { waitUntil: 'load' })
+    await page.waitForSelector('[class*="frame"]', { timeout: 30_000 })
+  }, 120_000)
+
+  afterAll(async () => {
+    await browser?.close()
+    await scaffold?.close()
+  })
+
+  it('renders full-session counts on the partial tail page and keeps them across load-older', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-stats-paged'))
+    const groupRow = page.locator('[role="treeitem"]').first()
+    await groupRow.waitFor({ timeout: 15_000 })
+    await groupRow.click()
+    const sessionRow = page.locator('[role="treeitem"]').nth(1)
+    await sessionRow.waitFor({ timeout: 10_000 })
+    await sessionRow.click()
+    // Settled barrier: the newest recorded reply renders from the tail page.
+    await expect.poll(() => page.getByText(`r${TURNS}`, { exact: true }).count(), { timeout: 15_000 }).toBe(1)
+    // The tail page is partial (56 messages > one 50-message page): the first
+    // turns are NOT loaded, yet the strip already reports the whole log —
+    // the sessionStats projection, not the window fold.
+    expect(await page.getByText('m1', { exact: true }).count()).toBe(0)
+    await expect.poll(() => page.getByText(FULL_COUNTS, { exact: false }).count(), { timeout: 10_000 }).toBe(1)
+    const strip = page.getByText(FULL_COUNTS, { exact: false }).locator('..')
+    const stripBeforePaging = await strip.textContent()
+
+    // 加载更早: prepending the older page must not move ANY strip figure —
+    // counts, wall times, or token groups.
+    await page.getByRole('button', { name: 'Load earlier' }).click()
+    await expect.poll(() => page.getByText('m1', { exact: true }).count(), { timeout: 10_000 }).toBe(1)
+    expect(await strip.textContent()).toBe(stripBeforePaging)
+    // With the whole log loaded, the window mounts one turn-tail footer per
+    // settled turn — the loaded-window probe the scroll/perf lanes count now
+    // that the strip is whole-log-scoped.
+    expect(await page.locator('[data-chat-flow-key^="9:turn-tail"]').count()).toBe(TURNS)
+  }, 60_000)
+
+  it('matches the paged-stats aria golden', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-stats-paged-aria'))
+    const snapshot = (await captureStableAria(page, '[class*="centerCol"]', scaffold.workspaceCwd))
+      .split(SEED_ID).join('{{seededId}}')
+    await compareOrRefreshGolden(UI_EXPECTED, snapshot, MODE)
+  })
+
+  it('issued zero model calls and stayed clean', async () => {
+    expect(tripwire.pageErrors).toEqual([])
+    expect(tripwire.warnings).toEqual([])
+    await assertFixtureInventory(SNAPSHOT_DIR, ['ui.expected.md'])
+  })
+})
diff --git a/apps/web/tsconfig.json b/apps/web/tsconfig.json
index 48a9002c98..8b2ed3d876 100644
--- a/apps/web/tsconfig.json
+++ b/apps/web/tsconfig.json
@@ -48,6 +48,7 @@
     "tests/replay-round-trip.e2e.ts",
     "tests/hmr-live.e2e.ts",
     "tests/seeded-history.e2e.ts",
+    "tests/stats-paged-history.e2e.ts",
     "tests/sidebar-scrollbar.e2e.ts",
     "tests/conversation-column-overflow.e2e.ts",
     "tests/code-mode-round.e2e.ts",
diff --git a/docs/config-catalog.i18n.yaml b/docs/config-catalog.i18n.yaml
index ddcef9c7a4..33fae42ac2 100644
--- a/docs/config-catalog.i18n.yaml
+++ b/docs/config-catalog.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/config-catalog.md
-config-catalog.md: 3eb59072b712c4386072042ba1c6f4f1f54423ca
-config-catalog.zh.md: ad91b5156c6b86225c502abdbdf73fbe1fd23e19
+config-catalog.md: f075a5c22049df1696a1849cd88bd3b783adde21
+config-catalog.zh.md: 952a77df3ba279155b4364a083917f816efd2d63
diff --git a/docs/config-catalog.md b/docs/config-catalog.md
index 3eb59072b7..f075a5c220 100644
--- a/docs/config-catalog.md
+++ b/docs/config-catalog.md
@@ -2848,6 +2848,7 @@ These load from a `cordis.yml` entry with no `config:` block; they declare no co
 - `@deepseek-ai/dsh-session-checkpoint-policy` — requires `llm` · `sessionPersistence` · `sessions` · `tools` ([`packages/session/session-checkpoint-policy/src/index.ts`](../packages/session/session-checkpoint-policy/src/index.ts))
 - `@deepseek-ai/dsh-session-export` — requires `commands` ([`packages/session-query/session-export/src/index.ts`](../packages/session-query/session-export/src/index.ts))
 - `@deepseek-ai/dsh-session-projection` ([`packages/session/session-projection/src/index.ts`](../packages/session/session-projection/src/index.ts))
+- `@deepseek-ai/dsh-session-stats` — requires `sessionProjections` ([`packages/session/session-stats/src/index.ts`](../packages/session/session-stats/src/index.ts))
 - `@deepseek-ai/dsh-skill-badge` — requires `skills` ([`packages/skill/skill-badge/src/index.ts`](../packages/skill/skill-badge/src/index.ts))
 - `@deepseek-ai/dsh-storage` ([`packages/storage/storage/src/index.ts`](../packages/storage/storage/src/index.ts))
 - `@deepseek-ai/dsh-subagent` ([`packages/subagent/subagent/src/index.ts`](../packages/subagent/subagent/src/index.ts))
diff --git a/docs/config-catalog.zh.md b/docs/config-catalog.zh.md
index ad91b5156c..952a77df3b 100644
--- a/docs/config-catalog.zh.md
+++ b/docs/config-catalog.zh.md
@@ -2849,6 +2849,7 @@ export interface Config {
 - `@deepseek-ai/dsh-session-checkpoint-policy` — 需要 `llm` · `sessionPersistence` · `sessions` · `tools`（[`packages/session/session-checkpoint-policy/src/index.ts`](../packages/session/session-checkpoint-policy/src/index.ts)）
 - `@deepseek-ai/dsh-session-export` — 需要 `commands`（[`packages/session-query/session-export/src/index.ts`](../packages/session-query/session-export/src/index.ts)）
 - `@deepseek-ai/dsh-session-projection`（[`packages/session/session-projection/src/index.ts`](../packages/session/session-projection/src/index.ts)）
+- `@deepseek-ai/dsh-session-stats` — 需要 `sessionProjections`（[`packages/session/session-stats/src/index.ts`](../packages/session/session-stats/src/index.ts)）
 - `@deepseek-ai/dsh-skill-badge` — 需要 `skills`（[`packages/skill/skill-badge/src/index.ts`](../packages/skill/skill-badge/src/index.ts)）
 - `@deepseek-ai/dsh-storage`（[`packages/storage/storage/src/index.ts`](../packages/storage/storage/src/index.ts)）
 - `@deepseek-ai/dsh-subagent`（[`packages/subagent/subagent/src/index.ts`](../packages/subagent/subagent/src/index.ts)）
diff --git a/docs/module-graph.i18n.yaml b/docs/module-graph.i18n.yaml
index 980d198c32..b528a4356d 100644
--- a/docs/module-graph.i18n.yaml
+++ b/docs/module-graph.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write docs/module-graph.md
-module-graph.md: 371699d8a4aab83eb8603ce1623373fe56871dd3
-module-graph.zh.md: 381a387ff77ef36dda31655bb9c0e4d5b931e544
+module-graph.md: 5197a184f2be283e3bb57de91d4a4d3cb22e51b2
+module-graph.zh.md: 3b312b731d32ed71674d800c35a5868e0b5d94ee
diff --git a/docs/module-graph.md b/docs/module-graph.md
index 371699d8a4..5197a184f2 100644
--- a/docs/module-graph.md
+++ b/docs/module-graph.md
@@ -274,6 +274,7 @@ flowchart TD
     pkg_session_persistence_sqlite["session-persistence-sqlite"]
     pkg_session_projection["session-projection"]
     pkg_session_projection_cache["session-projection-cache"]
+    pkg_session_stats["session-stats"]
     pkg_session_telemetry["session-telemetry"]
     pkg_session_telemetry_otel["session-telemetry-otel"]
     pkg_session_title["session-title"]
@@ -568,6 +569,10 @@ flowchart TD
   pkg_session_projection_cache --> pkg_session_persistence
   pkg_session_projection_cache --> pkg_session_projection
   pkg_session_projection_cache --> pkg_storage_domain
+  pkg_session_stats --> pkg_invariants
+  pkg_session_stats --> pkg_llm
+  pkg_session_stats --> pkg_session
+  pkg_session_stats --> pkg_session_projection
   pkg_session_telemetry --> pkg_agent
   pkg_session_telemetry --> pkg_invariants
   pkg_session_telemetry --> pkg_session
@@ -1212,6 +1217,7 @@ flowchart TD
   pkg_client_ui_conversation --> pkg_compact
   pkg_client_ui_conversation --> pkg_invariants
   pkg_client_ui_conversation --> pkg_llm_retry
+  pkg_client_ui_conversation --> pkg_session_stats
   pkg_client_ui_conversation --> pkg_token_meter
   pkg_client_ui_conversation --> pkg_tools
   pkg_client_ui_directory_picker --> pkg_client_locale
@@ -1461,6 +1467,7 @@ flowchart TD
 | [`session-persistence-jsonl`](../packages/session/session-persistence-jsonl) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence) |
 | [`session-persistence-sqlite`](../packages/session/session-persistence-sqlite) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence) |
 | [`session-projection-cache`](../packages/session/session-projection-cache) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence), [`session-projection`](../packages/session/session-projection), [`storage-domain`](../packages/storage/storage-domain) |
+| [`session-stats`](../packages/session/session-stats) | `session` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection) |
 | [`session-telemetry`](../packages/session/session-telemetry) | `session` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`session`](../packages/core/session) |
 | [`session-title`](../packages/session/session-title) | `session` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection) |
 | [`tasks`](../packages/tasks/tasks) | `tasks` | [`agent`](../packages/core/agent), [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`session`](../packages/core/session) |
@@ -1565,7 +1572,7 @@ flowchart TD
 | [`client-ui-trajectory`](../packages/client/ui-trajectory) | `client` | [`agent`](../packages/core/agent), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`tools`](../packages/core/tools) |
 | [`client-ui-workspace`](../packages/client/ui-workspace) | `client` | [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`acp-demo`](../packages/examples/acp-demo) | `examples` | [`acp`](../packages/acp/acp), [`agent-spine-demo`](../packages/examples/agent-spine-demo), [`app-boot`](../packages/boot/app-boot), [`invariants`](../packages/support/invariants), [`session-checkpoint-policy`](../packages/session/session-checkpoint-policy), [`session-persistence-jsonl`](../packages/session/session-persistence-jsonl), [`session-query`](../packages/session-query/session-query), [`session-query-sqlite`](../packages/session-query/session-query-sqlite), [`tools`](../packages/core/tools), [`workspace-context`](../packages/context/workspace-context) |
-| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`agent`](../packages/core/agent), [`api-remotes`](../packages/api/remotes), [`attachment`](../packages/attachment/attachment), [`brand`](../packages/util/brand), [`client-connection`](../packages/client/connection), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-attachment`](../packages/client/ui-attachment), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-settings`](../packages/client/ui-settings), [`client-ui-slash`](../packages/client/ui-slash), [`client-ui-slots`](../packages/client/ui-slots), [`commands`](../packages/interaction/commands), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`llm-retry`](../packages/llm/llm-retry), [`token-meter`](../packages/llm/token-meter), [`tools`](../packages/core/tools) |
+| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`agent`](../packages/core/agent), [`api-remotes`](../packages/api/remotes), [`attachment`](../packages/attachment/attachment), [`brand`](../packages/util/brand), [`client-connection`](../packages/client/connection), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-attachment`](../packages/client/ui-attachment), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-settings`](../packages/client/ui-settings), [`client-ui-slash`](../packages/client/ui-slash), [`client-ui-slots`](../packages/client/ui-slots), [`commands`](../packages/interaction/commands), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`llm-retry`](../packages/llm/llm-retry), [`session-stats`](../packages/session/session-stats), [`token-meter`](../packages/llm/token-meter), [`tools`](../packages/core/tools) |
 | [`client-ui-directory-picker`](../packages/client/ui-directory-picker) | `client` | [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-workspace`](../packages/client/ui-workspace), [`invariants`](../packages/support/invariants) |
 | [`client-ui-directory-picker-native`](../packages/client/ui-directory-picker-native) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-workspace`](../packages/client/ui-workspace), [`invariants`](../packages/support/invariants) |
 | [`client-ui-layout`](../packages/client/ui-layout) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-theme`](../packages/client/ui-theme), [`invariants`](../packages/support/invariants) |
diff --git a/docs/module-graph.zh.md b/docs/module-graph.zh.md
index 381a387ff7..3b312b731d 100644
--- a/docs/module-graph.zh.md
+++ b/docs/module-graph.zh.md
@@ -276,6 +276,7 @@ flowchart TD
     pkg_session_persistence_sqlite["session-persistence-sqlite"]
     pkg_session_projection["session-projection"]
     pkg_session_projection_cache["session-projection-cache"]
+    pkg_session_stats["session-stats"]
     pkg_session_telemetry["session-telemetry"]
     pkg_session_telemetry_otel["session-telemetry-otel"]
     pkg_session_title["session-title"]
@@ -570,6 +571,10 @@ flowchart TD
   pkg_session_projection_cache --> pkg_session_persistence
   pkg_session_projection_cache --> pkg_session_projection
   pkg_session_projection_cache --> pkg_storage_domain
+  pkg_session_stats --> pkg_invariants
+  pkg_session_stats --> pkg_llm
+  pkg_session_stats --> pkg_session
+  pkg_session_stats --> pkg_session_projection
   pkg_session_telemetry --> pkg_agent
   pkg_session_telemetry --> pkg_invariants
   pkg_session_telemetry --> pkg_session
@@ -1214,6 +1219,7 @@ flowchart TD
   pkg_client_ui_conversation --> pkg_compact
   pkg_client_ui_conversation --> pkg_invariants
   pkg_client_ui_conversation --> pkg_llm_retry
+  pkg_client_ui_conversation --> pkg_session_stats
   pkg_client_ui_conversation --> pkg_token_meter
   pkg_client_ui_conversation --> pkg_tools
   pkg_client_ui_directory_picker --> pkg_client_locale
@@ -1463,6 +1469,7 @@ flowchart TD
 | [`session-persistence-jsonl`](../packages/session/session-persistence-jsonl) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence) |
 | [`session-persistence-sqlite`](../packages/session/session-persistence-sqlite) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence) |
 | [`session-projection-cache`](../packages/session/session-projection-cache) | `session` | [`invariants`](../packages/support/invariants), [`session`](../packages/core/session), [`session-persistence`](../packages/session/session-persistence), [`session-projection`](../packages/session/session-projection), [`storage-domain`](../packages/storage/storage-domain) |
+| [`session-stats`](../packages/session/session-stats) | `session` | [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection) |
 | [`session-telemetry`](../packages/session/session-telemetry) | `session` | [`agent`](../packages/core/agent), [`invariants`](../packages/support/invariants), [`session`](../packages/core/session) |
 | [`session-title`](../packages/session/session-title) | `session` | [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-projection`](../packages/session/session-projection) |
 | [`tasks`](../packages/tasks/tasks) | `tasks` | [`agent`](../packages/core/agent), [`brand`](../packages/util/brand), [`invariants`](../packages/support/invariants), [`session`](../packages/core/session) |
@@ -1567,7 +1574,7 @@ flowchart TD
 | [`client-ui-trajectory`](../packages/client/ui-trajectory) | `client` | [`agent`](../packages/core/agent), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`tools`](../packages/core/tools) |
 | [`client-ui-workspace`](../packages/client/ui-workspace) | `client` | [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`invariants`](../packages/support/invariants) |
 | [`acp-demo`](../packages/examples/acp-demo) | `examples` | [`acp`](../packages/acp/acp), [`agent-spine-demo`](../packages/examples/agent-spine-demo), [`app-boot`](../packages/boot/app-boot), [`invariants`](../packages/support/invariants), [`session-checkpoint-policy`](../packages/session/session-checkpoint-policy), [`session-persistence-jsonl`](../packages/session/session-persistence-jsonl), [`session-query`](../packages/session-query/session-query), [`session-query-sqlite`](../packages/session-query/session-query-sqlite), [`tools`](../packages/core/tools), [`workspace-context`](../packages/context/workspace-context) |
-| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`agent`](../packages/core/agent), [`api-remotes`](../packages/api/remotes), [`attachment`](../packages/attachment/attachment), [`brand`](../packages/util/brand), [`client-connection`](../packages/client/connection), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-attachment`](../packages/client/ui-attachment), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-settings`](../packages/client/ui-settings), [`client-ui-slash`](../packages/client/ui-slash), [`client-ui-slots`](../packages/client/ui-slots), [`commands`](../packages/interaction/commands), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`llm-retry`](../packages/llm/llm-retry), [`token-meter`](../packages/llm/token-meter), [`tools`](../packages/core/tools) |
+| [`client-ui-conversation`](../packages/client/ui-conversation) | `client` | [`agent`](../packages/core/agent), [`api-remotes`](../packages/api/remotes), [`attachment`](../packages/attachment/attachment), [`brand`](../packages/util/brand), [`client-connection`](../packages/client/connection), [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-attachment`](../packages/client/ui-attachment), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-settings`](../packages/client/ui-settings), [`client-ui-slash`](../packages/client/ui-slash), [`client-ui-slots`](../packages/client/ui-slots), [`commands`](../packages/interaction/commands), [`compact`](../packages/compact/compact), [`invariants`](../packages/support/invariants), [`llm-retry`](../packages/llm/llm-retry), [`session-stats`](../packages/session/session-stats), [`token-meter`](../packages/llm/token-meter), [`tools`](../packages/core/tools) |
 | [`client-ui-directory-picker`](../packages/client/ui-directory-picker) | `client` | [`client-locale`](../packages/client/locale), [`client-runtime`](../packages/client/runtime), [`client-ui-primitives`](../packages/client/ui-primitives), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-workspace`](../packages/client/ui-workspace), [`invariants`](../packages/support/invariants) |
 | [`client-ui-directory-picker-native`](../packages/client/ui-directory-picker-native) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-workspace`](../packages/client/ui-workspace), [`invariants`](../packages/support/invariants) |
 | [`client-ui-layout`](../packages/client/ui-layout) | `client` | [`client-runtime`](../packages/client/runtime), [`client-ui-slots`](../packages/client/ui-slots), [`client-ui-theme`](../packages/client/ui-theme), [`invariants`](../packages/support/invariants) |
diff --git a/packages/bundle/web-app/cordis.patch.yml b/packages/bundle/web-app/cordis.patch.yml
index d7a1a864d5..1bb3bf6610 100644
--- a/packages/bundle/web-app/cordis.patch.yml
+++ b/packages/bundle/web-app/cordis.patch.yml
@@ -78,6 +78,11 @@
         writeEveryEvents: 200
         writeIntervalMs: 5000
 
+    # Whole-log turn/step counts for the chat stats strip (the sessionStats
+    # projection key); the projection registry itself is a base-layer row.
+    - id: session-stats
+      name: '@deepseek-ai/dsh-session-stats'
+
     # Resolve bind host, SSH launch, and display once at boot, then mount the
     # matching dual-face directory picker. Mount -native or -browse directly in
     # an overlay to pin the interaction.
diff --git a/packages/bundle/web-app/package.json b/packages/bundle/web-app/package.json
index 6ef0bdc422..5459c4e14b 100644
--- a/packages/bundle/web-app/package.json
+++ b/packages/bundle/web-app/package.json
@@ -93,6 +93,7 @@
     "@deepseek-ai/dsh-message-feedback": "workspace:^",
     "@deepseek-ai/dsh-session-projection-cache": "workspace:^",
     "@deepseek-ai/dsh-session-export": "workspace:^",
+    "@deepseek-ai/dsh-session-stats": "workspace:^",
     "@deepseek-ai/dsh-storage": "workspace:^",
     "@deepseek-ai/dsh-storage-domain": "workspace:^",
     "@deepseek-ai/dsh-storage-json": "workspace:^",
diff --git a/packages/client/connection/src/client/fixture.ts b/packages/client/connection/src/client/fixture.ts
index a013884492..f09b5d0a58 100644
--- a/packages/client/connection/src/client/fixture.ts
+++ b/packages/client/connection/src/client/fixture.ts
@@ -9,6 +9,7 @@ import {
   createAssistantMessage,
   createToolResultMessage,
   createUserMessage,
+  isTokenDelta,
 } from '@deepseek-ai/dsh-llm/message'
 import { CallId } from '@deepseek-ai/dsh-llm/brand'
 import type {
@@ -876,6 +877,76 @@ function tokenUsageOf(log: readonly SessionEvent[]): FixtureTokenUsageProjection
   return totals
 }
 
+/** Fixture parallel of session-stats' whole-log counting and wall-time fold. */
+function sessionStatsOf(log: readonly SessionEvent[]): {
+  turns: number
+  steps: number
+  llmMs: number
+  toolMs: number
+  ttftMs: number
+  ttftSteps: number
+  decodeMs: number
+  decodeTokens: number
+} {
+  const value = { turns: 0, steps: 0, llmMs: 0, toolMs: 0, ttftMs: 0, ttftSteps: 0, decodeMs: 0, decodeTokens: 0 }
+  let lastTurn: number | null = null
+  let openStep: { turn: number; step: number; startTime: number; firstTokenTime: number | null } | null = null
+  const pendingCalls = new Map<string, number>()
+  for (const event of log) {
+    switch (event.type) {
+      case 'step/start':
+        openStep = { turn: event.data.turn, step: event.data.step, startTime: event.time, firstTokenTime: null }
+        break
+      case 'assistant/chunk':
+        if (openStep !== null && openStep.turn === event.data.turn && openStep.step === event.data.step
+          && openStep.firstTokenTime === null && isTokenDelta(event.data.chunk)) {
+          openStep.firstTokenTime = event.time
+        }
+        break
+      case 'assistant/message': {
+        if (openStep === null || openStep.turn !== event.data.turn || openStep.step !== event.data.step) break
+        value.llmMs += Math.max(0, event.time - openStep.startTime)
+        if (openStep.firstTokenTime !== null) {
+          value.ttftMs += Math.max(0, openStep.firstTokenTime - openStep.startTime)
+          value.ttftSteps += 1
+          const outputTokens = event.data.usage?.outputTokens
+          if (typeof outputTokens === 'number' && Number.isFinite(outputTokens) && outputTokens >= 0) {
+            value.decodeMs += Math.max(0, event.time - openStep.firstTokenTime)
+            value.decodeTokens += outputTokens
+          }
+        }
+        openStep = null
+        break
+      }
+      case 'tool/call':
+        pendingCalls.set(event.data.callId, event.time)
+        break
+      case 'tool/result': {
+        const callId = event.data.message.source.callId
+        const dispatched = pendingCalls.get(callId)
+        if (dispatched === undefined) break
+        pendingCalls.delete(callId)
+        value.toolMs += Math.max(0, event.time - dispatched)
+        break
+      }
+      case 'step/end':
+        if (event.data.turn !== lastTurn) {
+          value.turns += 1
+          lastTurn = event.data.turn
+        }
+        value.steps += 1
+        openStep = null
+        break
+      case 'turn/end':
+        pendingCalls.clear()
+        break
+      default:
+        break
+    }
+  }
+  return value
+}
+
 interface FixtureRequestContext {
   provider: string
   model: string
@@ -994,6 +1065,8 @@ function projectionValuesOf(log: readonly SessionEvent[]): Record<string, unknow
   values['contextPressure'] = contextPressureOf(log)
   // Always present (token-meter composed): heuristic request composition.
   values['contextBreakdown'] = contextBreakdownOf(log)
+  // Always present (session-stats unit composed): whole-log turn/step counts.
+  values['sessionStats'] = sessionStatsOf(log)
   // Always present (attachment service composed): the deployment image
   // limits, constant per boot (mirrors the attachment-local defaults).
   // Deliberate host divergence: the real gateway never pushes an imageLimits
@@ -1041,6 +1114,17 @@ function projectionFramesOf(id: SessionId, log: readonly SessionEvent[], event:
       seq: event.seq,
     })
   }
+  // The stats fold's view advances on message assembly and tool settlement
+  // (wall times) and on step close (counts).
+  if (type === 'assistant/message' || type === 'tool/result' || type === 'step/end') {
+    frames.push({
+      type: 'session/projection',
+      sessionId: id,
+      key: 'sessionStats',
+      value: sessionStatsOf(log),
+      seq: event.seq,
+    })
+  }
   if (frames.length > 0) return frames
   if (type === 'session/title') {
     const values = projectionValuesOf(log)
diff --git a/packages/client/connection/tests/fixture.client.spec.ts b/packages/client/connection/tests/fixture.client.spec.ts
index 5bf2aa4e2e..11c4ddab8a 100644
--- a/packages/client/connection/tests/fixture.client.spec.ts
+++ b/packages/client/connection/tests/fixture.client.spec.ts
@@ -164,6 +164,10 @@ describe('createFixtureApi', () => {
           toolsTokens: 0,
           messageTokens: 0,
         },
+        // Session-stats unit composed: no figure accrues on the empty log.
+        sessionStats: {
+          turns: 0, steps: 0, llmMs: 0, toolMs: 0, ttftMs: 0, ttftSteps: 0, decodeMs: 0, decodeTokens: 0,
+        },
         imageLimits: {
           maxImageBytes: 5 * 1024 * 1024,
           maxImagesPerMessage: 20,
@@ -360,7 +364,7 @@ describe('createFixtureApi', () => {
       const envelopes: RpcRequest<MuxFrame>[] = []
       for await (const envelope of api.events.mux(req({}), abort.signal)) {
         envelopes.push(envelope)
-        if (envelopes.length >= 11) abort.abort()
+        if (envelopes.length >= 13) abort.abort()
       }
       return envelopes
     }
@@ -381,14 +385,16 @@ describe('createFixtureApi', () => {
       value: { systemTokens: 0, toolsTokens: 0 },
     })
     expect((first[8]?.payload as { value: { messageTokens: number } }).value.messageTokens).toBeGreaterThan(0)
-    expect(first[9]?.payload).toMatchObject({
+    expect(first[9]?.payload).toMatchObject({ type: 'session/projection', sessionId: 'fx-alpha', key: 'sessionStats' })
+    expect((first[9]?.payload as { value: { turns: number; steps: number } }).value.steps).toBeGreaterThan(0)
+    expect(first[10]?.payload).toMatchObject({
       type: 'session/projection', sessionId: 'fx-alpha', key: 'imageLimits',
       value: { maxImagesPerMessage: 20, maxImageBytes: 5 * 1024 * 1024 },
     })
-    expect(first[10]?.payload).toMatchObject({ type: 'approval/requested', toolName: 'dangerous_tool' })
-    expect(second[10]?.rpcId).toBe(first[10]?.rpcId) // stable rpcId across replays (host replay semantics)
-    expect(first[11]?.payload).toMatchObject({ type: 'question/requested', sessionId: 'fx-alpha' })
-    expect(second[11]?.rpcId).toBe(first[11]?.rpcId)
+    expect(first[11]?.payload).toMatchObject({ type: 'approval/requested', toolName: 'dangerous_tool' })
+    expect(second[11]?.rpcId).toBe(first[11]?.rpcId) // stable rpcId across replays (host replay semantics)
+    expect(first[12]?.payload).toMatchObject({ type: 'question/requested', sessionId: 'fx-alpha' })
+    expect(second[12]?.rpcId).toBe(first[12]?.rpcId)
   })
 
   it('steer with no replay in flight falls through to a fresh queued turn; non-text blocks stringify empty', async () => {
diff --git a/packages/client/runtime/src/client/sessions/assistant-timing.ts b/packages/client/runtime/src/client/sessions/assistant-timing.ts
index 3c54c9c36d..179f76281d 100644
--- a/packages/client/runtime/src/client/sessions/assistant-timing.ts
+++ b/packages/client/runtime/src/client/sessions/assistant-timing.ts
@@ -2,9 +2,14 @@
 // history fold derive AssistantTiming from the same step/start -> first token
 // delta -> assistant/message sequence.
 
+import { isTokenDelta } from '@deepseek-ai/dsh-llm/message'
 import type { SessionEvent } from '@deepseek-ai/dsh-session/types'
 import type { AssistantTiming } from './conversation.ts'
 
+// The first-token predicate lives beside the StreamChunk type in dsh-llm;
+// re-exported here so Chat Definitions keep their client-runtime import.
+export { isTokenDelta } from '@deepseek-ai/dsh-llm/message'
+
 /** Pre-finalize timing boundaries for one assistant step (start + first token). */
 export interface AssistantStepMetadata {
   stepStartTime: number | null
@@ -21,24 +26,6 @@ export function assistantStepKey(turn: number, step: number): string {
   return `${turn}\u0000${step}`
 }
 
-/**
- * Whether a chunk carries visible model output (first-token boundary). Empty
- * deltas (heartbeats, empty tool-call frames) do not count as a first token.
- * @param chunk - the assistant/chunk payload.
- * @returns true when the chunk contains a non-empty text/reasoning/tool delta.
- */
-export function isTokenDelta(chunk: SessionEvent<'assistant/chunk'>['data']['chunk']): boolean {
-  switch (chunk.type) {
-    case 'text-delta':
-    case 'reasoning-delta':
-      return chunk.text !== ''
-    case 'tool-call-delta':
-      return chunk.argumentsDelta !== '' || chunk.name !== undefined
-    default:
-      return false
-  }
-}
-
 /**
  * Fold one event into the per-step timing index: step/start opens the entry,
  * the first non-empty token delta stamps first-token time once. Other event
diff --git a/packages/client/ui-conversation/README.i18n.yaml b/packages/client/ui-conversation/README.i18n.yaml
index 31b787931d..a49f573fbc 100644
--- a/packages/client/ui-conversation/README.i18n.yaml
+++ b/packages/client/ui-conversation/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/client/ui-conversation/README.md
-README.md: b6a265c9f0a67d31ebeaa88bd59082c4be465983
-README.zh.md: 001e0a58badd6f31875c09a31085277928f1ae22
+README.md: 131f76fc8bc7b63449e022ad91fd8453c10d5f01
+README.zh.md: 8d0cd4e82b8bf4256db9b0f3cb868630f57ce68e
diff --git a/packages/client/ui-conversation/README.md b/packages/client/ui-conversation/README.md
index b6a265c9f0..131f76fc8b 100644
--- a/packages/client/ui-conversation/README.md
+++ b/packages/client/ui-conversation/README.md
@@ -40,7 +40,7 @@ Image intake accepts paste and whole-page drop: the bar binds document-level dra
 
 The composer bar declares session-scoped single seats for `'conversation.input.plan'` (right of the local access-mode control) and `'conversation.input.model'` (immediately before the pending indicator and send/stop controls), plus list slots for overlay, dock, left, and right input extensions. Feature packages own each control and its state; ui-conversation supplies placement, the `locked` owner prop, and the standard slot shares. The leading plus button is a Command launcher, not an attachment surface: it asks the session's `SlashController` to open only the `/` trigger's `command` source over the current textarea selection, while ui-slash's existing `MenuView` remains the sole floating menu and pick path. No file row, file input, upload protocol, or second menu component is introduced. While the `plan` projection's effective target is plan mode, InputBar swaps its textarea placeholder to the plan-task wording, localized through the `conversation` locale namespace this package registers (the `placeholder.plan` / `hint.plan` keys) and shared verbatim with the claimed `/plan` command hint (a host-folded value read through the standard-kit `useProjection`; owner-supplied placeholders win). A pending composer takeover remains mounted when another conversation view is active so the blocked agent can still receive its answer; without a pending interaction, the active-session composer belongs to Chat. The composer-bar slot itself is `session-maybe`: with no current session the same bar keeps message actions inert (machine faces absent, `disabled` owner prop), while the whole dashed card opens the existing Workspace picker by pointer and the read-only textarea opens it through Enter or Space. Disabled controls release pointer events to the card, and the card contains `pointerdown` so the open picker's outside-close cannot race a reopen. The bar never swaps in a parallel tree, so the textarea DOM survives Workspace selection; strict-session control seats stay empty until a session exists.
 
-The chat stats line takes its token accounting from the generic token-meter `tokenUsage` projection read through the standard-kit `useProjection`: billed input is uncached input plus cache reads and writes; cache hit divides cache reads by that total. Visible nodes supply only the turn and step counts plus the LLM and tool wall times, which are window-scoped facts about what is on screen rather than accounting; durable token and context groups remain visible when compaction leaves no assistant node in the loaded window. The same window fold averages each recorded step's TTFT and divides sampled output tokens by their summed decode spans into a latency/throughput group localized through the `conversation` locale namespace (`TTFT avg … · … tok/s` in English); a step missing a timing boundary or a usage sample drops out of those figures instead of skewing them. The turn-count, step-count, duration, cache, and token labels use the same namespace. Each settled turn additionally appends hover-revealed `TTFT {s}s · {tps} tok/s` labels to its assistant footer after the `Ran for` duration — the turn's first-step TTFT and its turn-aggregate decode throughput — gated on the turn's timing being in the loaded window (a contiguous log suffix, so an in-window turn carries every one of its steps) and omitting whichever figure is unrecorded. A deployment without token-meter drops the token groups; when the line overflows, it elides with an ellipsis and a delayed hover tooltip carries the full text only while actually clipped. Context occupancy renders as the composer's trailing ContextMeter: a 14px occupancy ring after the model seat, fed by `contextPressure` and rendered only once both a numerator and a route capacity are known, that click-opens a panel pairing the `percent used` header and `~used / capacity` figures with a color-segmented bar and `~`-prefixed heuristic composition rows (system prompt, tools, messages) from the `contextBreakdown` projection. The ring and header read `projectedTokens` — the provider sample carried forward over the surface's movement since — so a compaction registers immediately instead of after a further turn; the composition rows stay wholly heuristic and therefore still do not sum to the header ([rationale](../../llm/token-meter/README.md)). Occupancy is deliberately an approximation: numerator and capacity are independent last-wins projection fields, not one atomic request observation.
+The chat stats line takes its token accounting from the generic token-meter `tokenUsage` projection read through the standard-kit `useProjection`: billed input is uncached input plus cache reads and writes; cache hit divides cache reads by that total. The turn and step counts, the LLM and tool wall times, and the latency/throughput group all ride the whole-log `sessionStats` projection (host-folded from step boundaries, first-token chunks, tool pairs, and assembled messages), so paging and compaction cannot change any strip figure; an assembly without that unit falls back to the window fold over visible nodes, whose fields mirror the projection's. The strip averages each recorded step's TTFT and divides sampled output tokens by their summed decode spans into a latency/throughput group localized through the `conversation` locale namespace (`TTFT avg … · … tok/s` in English); a step missing a timing boundary or a usage sample drops out of those figures instead of skewing them, and durable count, token, and context groups remain visible when compaction leaves no assistant node in the loaded window. The turn-count, step-count, duration, cache, and token labels use the same namespace. Each settled turn additionally appends hover-revealed `TTFT {s}s · {tps} tok/s` labels to its assistant footer after the `Ran for` duration — the turn's first-step TTFT and its turn-aggregate decode throughput — gated on the turn's timing being in the loaded window (a contiguous log suffix, so an in-window turn carries every one of its steps) and omitting whichever figure is unrecorded. A deployment without token-meter drops the token groups; when the line overflows, it elides with an ellipsis and a delayed hover tooltip carries the full text only while actually clipped. Context occupancy renders as the composer's trailing ContextMeter: a 14px occupancy ring after the model seat, fed by `contextPressure` and rendered only once both a numerator and a route capacity are known, that click-opens a panel pairing the `percent used` header and `~used / capacity` figures with a color-segmented bar and `~`-prefixed heuristic composition rows (system prompt, tools, messages) from the `contextBreakdown` projection. The ring and header read `projectedTokens` — the provider sample carried forward over the surface's movement since — so a compaction registers immediately instead of after a further turn; the composition rows stay wholly heuristic and therefore still do not sum to the header ([rationale](../../llm/token-meter/README.md)). Occupancy is deliberately an approximation: numerator and capacity are independent last-wins projection fields, not one atomic request observation.
 
 `src/client/` is organized by domain. `contract/` is the shared face for slot declarations, composed props, and cross-domain types; `skeleton/`, `chat/`, `input/`, `queue/`, and `settings/` keep their implementations internal, while `apply.ts` is their assembly point. The `/client` exports contain only loader entries, service classes, and contract types; components and store factories reach the page through slot registrations.
 
@@ -56,7 +56,7 @@ None; this package neither assembles nor sends a provider request.
 
 ## Known Limitations and Deferred Work
 
-- **Stats-line durations and speeds cover the in-window flow only** — LLM and tool wall times plus the TTFT and throughput averages fold the snapshot's assistant `timing` and tool call/result pairs, so nodes outside the loaded event window (older history) are not counted.
+- **The stats-line fallback fold covers the in-window flow only** — without the `sessionStats` projection (an assembly that does not mount the unit), every figure folds the snapshot's assistant `timing` and tool call/result pairs, so nodes outside the loaded event window (older history) are not counted and the numbers grow per loaded page.
 - **The details panel has no entry point** — `ChatViewInjected.openDetails` is implemented but uncalled, so the raw selected-call display is unreachable in the assembled application. There is no Input/Output/Metadata switch, Prev/Next stepping, or trajectory deep link.
 - **Assistant per-message paging is a reserved slot** — drawn in the design, not implemented. The finalized content IconActions row (copy / clock / branch) ships under the last content-text assistant of each turn that has ended; mid-turn narration, Think-only nodes, and every node of a turn still producing steps stay chrome-free. Branch stays disabled unless that message is also the last transcript node of a completed turn; when enabled, it forks through that turn, increments the inherited title on the client, and opens the child. A fork or rename failure leaves the source selected ([decision](../../../.agents/notes/implemented/bug-fix/2026-08-02-message-fork-actions-require-completed-turn-tail.md)).
 - **Sent user messages cannot be edited** — user bubbles retain clock and copy; branch lives only under assistant answers ([decision](../../../.agents/notes/implemented/simplification/2026-08-06-user-bubbles-drop-the-branch-action.md)). Editing returns with the capability behind it: a client mutation over a settled user message, plus the host behavior for the turn that already consumed it ([decision](../../../.agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.md)).
diff --git a/packages/client/ui-conversation/README.zh.md b/packages/client/ui-conversation/README.zh.md
index 001e0a58ba..8d0cd4e82b 100644
--- a/packages/client/ui-conversation/README.zh.md
+++ b/packages/client/ui-conversation/README.zh.md
@@ -40,7 +40,7 @@ Host 带 placement 的 `session/queue` 快照也会携带待处理 steering。Qu
 
 输入栏为 `'conversation.input.plan'`（位于本地 access 模式控件右侧）和 `'conversation.input.model'`（渲染在 pending 指示器与发送／停止控件之前）声明会话作用域的单实例 seat，并为 overlay、dock、left 和 right 输入扩展声明列表 slot。各功能包拥有相应控件及其状态；ui-conversation 提供放置位置、`locked` owner prop 和标准 slot share。前置加号按钮是 Command launcher，而非附件入口：它要求当前会话的 `SlashController` 基于 textarea 当前 selection，只打开 `/` trigger 的 `command` source，同时 ui-slash 既有的 `MenuView` 仍是唯一的浮层菜单与 pick 路径。不引入 File 行、file input、上传协议或第二套菜单组件。当 `plan` 投影的有效目标为 plan mode 时，InputBar 将文本框 placeholder 切换为 plan 任务措辞，经本包注册的 `conversation` locale 命名空间（`placeholder.plan` / `hint.plan` 键）本地化，并与已认领 `/plan` 命令的提示逐字共用同一份文案（经标准套件 `useProjection` 读取的 host 折叠值；owner 提供的 placeholder 优先）。另一个会话视图活跃时，待处理的 composer 接管仍保持挂载，使被阻塞的 agent（智能体）仍能收到回答；没有待处理交互时，活跃会话的 composer 归 Chat 所有。composer bar slot 本身为 `session-maybe`：没有当前会话时，同一个 bar 会让消息操作保持不可交互（machine face 均缺席、`disabled` owner prop），整张虚线卡片可经指针打开现有 Workspace picker，只读 textarea 也可通过 Enter 或 Space 打开。禁用控件会把指针事件交给卡片，卡片也会拦下 `pointerdown`，避免已打开 picker 的外点关闭与重新打开发生竞态。它不会换入一棵平行树，因此选择 Workspace 时 textarea DOM 不会被销毁；严格会话作用域的控件 seat 在会话存在之前保持为空。
 
-聊天统计行的 token 账目来自经标准套件 `useProjection` 读取的通用 token-meter 投影 `tokenUsage`：计费输入为未缓存输入、缓存读取与缓存写入之和；缓存命中率以缓存读取除以该总量。可见节点只提供轮次与步骤计数，以及 LLM（大语言模型）和工具的墙钟时间：这些是关于「屏幕上有什么」的窗口作用域事实，而非账目；压缩（compaction）使已加载窗口不再包含 assistant 节点时，持久 token 与上下文分组仍保持可见。同一次窗口折算还会把每个有完整记录的步骤的 TTFT（首 token 延迟）取平均，并用采样到的输出 token 数除以其解码时长之和，得到经 `conversation` locale 命名空间本地化的延迟／吞吐分组（中文为 `首 token 平均 … · … tok/s`）；缺少某个 timing 边界或 usage 采样的步骤会直接退出这些数字，而不是让它们失真。轮次计数、步骤计数、耗时、缓存与 token 各项的标签也使用同一命名空间。每个已结算轮次还会在其 assistant footer 的 `用时` 之后追加 hover 才显示的 `首 token {s}秒 · {tps} tok/s` 标签——即该轮次首个步骤的 TTFT 与轮次聚合的解码吞吐——仅当该轮次的 timing 位于已加载窗口内才显示（窗口是日志的连续后缀，因此窗口内的轮次必然带着它的全部步骤），未记录的数字会各自省略。未组合 token-meter 的部署会整组省略 token 分组；统计行过长时以省略号截断，仅在内容真的被裁切时由延迟 hover tooltip 承载完整文本。上下文占用率渲染为 composer 尾部的 ContextMeter：模型座位之后的一枚 14px 占用圆环，由 `contextPressure` 供数，仅当分子与路由容量都已知时才渲染；点击弹出的面板把「已用百分比」标题与 `~已用 / 容量` 数字，与来自 `contextBreakdown` 投影、带 `~` 前缀的启发式组成明细行（系统提示词、工具、对话消息）及分色分段进度条并列。圆环与标题读取 `projectedTokens`——把提供方样本沿此后表层的增减推进到当下——因此压缩会立刻反映出来，而不必再等一整轮；组成明细行仍是纯启发式，因此加起来依然不等于标题数字（[原理](../../llm/token-meter/README.md)）。占用率是刻意为之的近似值：分子与容量是两个相互独立的「后写覆盖」投影字段，并非同一次请求的原子观测。
+聊天统计行的 token 账目来自经标准套件 `useProjection` 读取的通用 token-meter 投影 `tokenUsage`：计费输入为未缓存输入、缓存读取与缓存写入之和；缓存命中率以缓存读取除以该总量。轮次与步骤计数、LLM（大语言模型）与工具墙钟时间、以及延迟／吞吐分组都来自全日志的 `sessionStats` 投影（Host 端从步边界、首 token chunk、工具配对与已组装消息折算），因此分页与压缩都无法改变统计条的任何数字；未组合该单元的装配回退为对可见节点做窗口折算，其字段与投影一一对应。统计条把每个有完整记录的步骤的 TTFT（首 token 延迟）取平均，并用采样到的输出 token 数除以其解码时长之和，得到经 `conversation` locale 命名空间本地化的延迟／吞吐分组（中文为 `首 token 平均 … · … tok/s`）；缺少某个 timing 边界或 usage 采样的步骤会直接退出这些数字，而不是让它们失真；压缩（compaction）使已加载窗口不再包含 assistant 节点时，持久计数、token 与上下文分组仍保持可见。轮次计数、步骤计数、耗时、缓存与 token 各项的标签也使用同一命名空间。每个已结算轮次还会在其 assistant footer 的 `用时` 之后追加 hover 才显示的 `首 token {s}秒 · {tps} tok/s` 标签——即该轮次首个步骤的 TTFT 与轮次聚合的解码吞吐——仅当该轮次的 timing 位于已加载窗口内才显示（窗口是日志的连续后缀，因此窗口内的轮次必然带着它的全部步骤），未记录的数字会各自省略。未组合 token-meter 的部署会整组省略 token 分组；统计行过长时以省略号截断，仅在内容真的被裁切时由延迟 hover tooltip 承载完整文本。上下文占用率渲染为 composer 尾部的 ContextMeter：模型座位之后的一枚 14px 占用圆环，由 `contextPressure` 供数，仅当分子与路由容量都已知时才渲染；点击弹出的面板把「已用百分比」标题与 `~已用 / 容量` 数字，与来自 `contextBreakdown` 投影、带 `~` 前缀的启发式组成明细行（系统提示词、工具、对话消息）及分色分段进度条并列。圆环与标题读取 `projectedTokens`——把提供方样本沿此后表层的增减推进到当下——因此压缩会立刻反映出来，而不必再等一整轮；组成明细行仍是纯启发式，因此加起来依然不等于标题数字（[原理](../../llm/token-meter/README.md)）。占用率是刻意为之的近似值：分子与容量是两个相互独立的「后写覆盖」投影字段，并非同一次请求的原子观测。
 
 `src/client/` 按领域组织。`contract/` 是 slot 声明、组合 props 与跨领域类型的共享表层；`skeleton/`、`chat/`、`input/`、`queue/` 和 `settings/` 保持内部实现，`apply.ts` 是它们的组装点。`/client` 导出表层只包含 loader entry、service class 和 contract 类型；组件与 store factory 经 slot 注册抵达页面。
 
@@ -56,7 +56,7 @@ Host 带 placement 的 `session/queue` 快照也会携带待处理 steering。Qu
 
 ## 已知限制与暂缓事项
 
-- **统计行的耗时与速率只覆盖窗口内消息流**：LLM 与工具墙钟时间以及 TTFT 与吞吐平均值由快照的 assistant `timing` 与工具调用／工具结果配对折算，落在已加载事件窗口之外的节点（更早的历史）不计入。
+- **统计行的回退折算只覆盖窗口内消息流**：未组合 `sessionStats` 投影单元的装配中，所有数字由快照的 assistant `timing` 与工具 call/result 配对折算，落在已加载事件窗口之外的节点（更早的历史）不计入，数字随加载页数增长。
 - **详情面板没有入口**：`ChatViewInjected.openDetails` 虽已实现却无人调用，因此以原始形式显示已选择调用的那部分在组装后的应用中不可达。没有 Input/Output/Metadata 切换、Prev/Next 步进，也没有 trajectory 深链接。
 - **assistant 逐消息分页是预留 slot**：设计中已有图稿，尚未实现。已定稿的内容 IconActions 行（复制／时钟／分支）只挂在每个已结束轮次中最后一条带 text 内容的 assistant 下；轮次中间的叙述、纯 Think 节点，以及仍在产出步骤的轮次里的所有节点都不带 chrome。除非该消息同时也是已完成轮次的最后一个 transcript 节点，否则分支保持禁用；启用后，它会 fork 到该轮次末尾，在 client 端递增继承标题并打开子会话。fork 或改名失败时源会话保持选中（[决策](../../../.agents/notes/implemented/bug-fix/2026-08-02-message-fork-actions-require-completed-turn-tail.md)）。
 - **已发送的 user 消息无法编辑**：user 气泡保留时钟和复制；分支只存在于 assistant 回答之下（[决策](../../../.agents/notes/implemented/simplification/2026-08-06-user-bubbles-drop-the-branch-action.md)）。编辑功能要与其背后的能力一起回归：既需要针对已定稿 user 消息的 client 变更，也需要 host 侧对已经消费过它的轮次给出行为（[决策](../../../.agents/notes/implemented/simplification/2026-07-31-drop-user-message-edit-stub.md)）。
diff --git a/packages/client/ui-conversation/package.json b/packages/client/ui-conversation/package.json
index a9996ce09a..3fe601174d 100644
--- a/packages/client/ui-conversation/package.json
+++ b/packages/client/ui-conversation/package.json
@@ -70,6 +70,7 @@
     "@deepseek-ai/dsh-compact": "workspace:^",
     "@deepseek-ai/dsh-invariants": "workspace:^",
     "@deepseek-ai/dsh-llm-retry": "workspace:^",
+    "@deepseek-ai/dsh-session-stats": "workspace:^",
     "@deepseek-ai/dsh-token-meter": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "react": "^18.2.0"
@@ -98,6 +99,7 @@
     "@deepseek-ai/dsh-permission": "workspace:^",
     "@deepseek-ai/dsh-plan-mode": "workspace:^",
     "@deepseek-ai/dsh-session-projection": "workspace:^",
+    "@deepseek-ai/dsh-session-stats": "workspace:^",
     "@deepseek-ai/dsh-token-meter": "workspace:^",
     "@deepseek-ai/dsh-tool-todo": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
diff --git a/packages/client/ui-conversation/src/client/chat/StatsLine.tsx b/packages/client/ui-conversation/src/client/chat/StatsLine.tsx
index 8e43f3c0b4..147d2b7c6c 100644
--- a/packages/client/ui-conversation/src/client/chat/StatsLine.tsx
+++ b/packages/client/ui-conversation/src/client/chat/StatsLine.tsx
@@ -6,6 +6,8 @@ import { Fragment, memo, useLayoutEffect, useMemo, useRef, useState } from 'reac
 import { Tooltip } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { ConversationSnapshot, UseProjection } from '@deepseek-ai/dsh-client-runtime/client'
 import type { SnapshotSelectorHook } from '@deepseek-ai/dsh-client-ui-slots'
+// Type-only: merges the sessionStats key into SessionProjectionMap for useProjection.
+import type {} from '@deepseek-ai/dsh-session-stats/client'
 import type { ContextPressureProjection, TokenUsageProjection } from '@deepseek-ai/dsh-token-meter/client'
 import type { ComposerBarProps } from '../contract/slots.ts'
 import { formatTokensPerSecond } from './message-chrome.ts'
@@ -30,14 +32,16 @@ interface WindowStats {
 }
 
 /**
- * Fold assistant and tool-result nodes into the window-scoped display totals.
+ * Fold assistant and tool-result nodes into window-scoped display totals —
+ * the FALLBACK for assemblies without the `sessionStats` projection.
  *
- * Counts and wall times describe the loaded window on purpose — they answer
- * "what is on screen". Token accounting deliberately does NOT come from here:
- * the window is paged and compaction rewrites it, so billing rides the durable
- * `tokenUsage` projection instead.
+ * Every displayed figure rides that durable whole-log projection (and token
+ * accounting rides `tokenUsage`) because the window is paged and compaction
+ * rewrites it; this fold answers "what is on screen" only when no projection
+ * value is served. Its field names deliberately mirror the projection's so
+ * the two swap wholesale.
  * @param nodes - snapshot nodes.
- * @returns visible counts and summed wall times.
+ * @returns fallback counts and summed wall times.
  */
 export function deriveStats(nodes: ConversationSnapshot['nodes']): WindowStats {
   const turns = new Set<number>()
@@ -158,8 +162,13 @@ export interface StatsLineProps {
 
 export const StatsLine = memo(function StatsLine({ useSession, useProjection, t }: StatsLineProps) {
   const settledNodes = useSession(s => s.chat.legacy.nodes)
-  const stats = useMemo(() => deriveStats(settledNodes), [settledNodes])
   const usage = useProjection('tokenUsage')
+  // Every figure rides the durable sessionStats projection, so paging and
+  // compaction cannot change any of them; an assembly without the unit falls
+  // back to the window-scoped fold wholesale (same field names), paid only
+  // while no projection value is served.
+  const projected = useProjection('sessionStats')
+  const stats = useMemo(() => projected ?? deriveStats(settledNodes), [projected, settledNodes])
   // Pipe-separated groups (figma stats strip); a group with no data drops out whole.
   const groups: string[] = []
   if (stats.steps > 0) {
@@ -168,7 +177,6 @@ export const StatsLine = memo(function StatsLine({ useSession, useProjection, t
     if (stats.llmMs > 0) durations.push(t('stats.llm', { duration: formatDuration(stats.llmMs) }))
     if (stats.toolMs > 0) durations.push(t('stats.toolCall', { duration: formatDuration(stats.toolMs) }))
     if (durations.length > 0) groups.push(durations.join(' · '))
-    // Window-scoped like the wall times above: averages describe loaded steps.
     const speeds: string[] = []
     if (stats.ttftSteps > 0) {
       speeds.push(t('stats.ttftAverage', { duration: formatDuration(stats.ttftMs / stats.ttftSteps) }))
@@ -183,9 +191,11 @@ export const StatsLine = memo(function StatsLine({ useSession, useProjection, t
   // Context occupancy deliberately lives on the composer's ContextMeter ring,
   // not here — one home per fact.
   // Billing rides the durable projection, so these survive paging and
-  // compaction. Suppress the empty projection on a brand-new session.
+  // compaction. Gated on actual token activity: a session whose steps all
+  // settled without billing (e.g. every request failed) shows its counts
+  // without a zero-token group.
   if (usage !== undefined
-    && (stats.steps > 0 || billedInputTokens(usage) > 0 || usage.outputTokens > 0)) {
+    && (billedInputTokens(usage) > 0 || usage.outputTokens > 0)) {
     const cacheHit = cacheHitPercent(usage)
     if (cacheHit !== null) groups.push(t('stats.cacheHit', { percent: cacheHit }))
     groups.push(t('stats.tokens', {
diff --git a/packages/client/ui-conversation/tests/chat-stats.client.spec.tsx b/packages/client/ui-conversation/tests/chat-stats.client.spec.tsx
index b53a1aa739..4ace851a66 100644
--- a/packages/client/ui-conversation/tests/chat-stats.client.spec.tsx
+++ b/packages/client/ui-conversation/tests/chat-stats.client.spec.tsx
@@ -98,9 +98,11 @@ describe('deriveStats', () => {
     ])
     expect(stats.turns).toBe(2)
     expect(stats.steps).toBe(3)
-    // Window-scoped by design: the paged window is not an accounting source, so
-    // the fold exposes no billing fields (billing rides the projection);
-    // decodeTokens is a throughput input, not a billed total.
+    // The window fold's counts are only the fallback for assemblies without
+    // the sessionStats projection; the paged window is not an accounting
+    // source either, so the fold exposes no billing fields (billing rides the
+    // tokenUsage projection); decodeTokens is a throughput input, not a
+    // billed total.
     expect(Object.keys(stats).sort()).toEqual(
       ['decodeMs', 'decodeTokens', 'llmMs', 'steps', 'toolMs', 'ttftMs', 'ttftSteps', 'turns'],
     )
@@ -169,6 +171,14 @@ describe('formatters', () => {
 describe('StatsLine', () => {
   const USAGE = { uncachedInputTokens: 10, outputTokens: 5, cacheReadTokens: 90, cacheWriteTokens: 0 }
 
+  /** A whole-log sessionStats value: zeros plus overrides. */
+  function sessionStats(overrides: Record<string, number>): Record<string, number> {
+    return {
+      turns: 0, steps: 0, llmMs: 0, toolMs: 0, ttftMs: 0, ttftSteps: 0, decodeMs: 0, decodeTokens: 0,
+      ...overrides,
+    }
+  }
+
   /** Stub the projection seat: a key-addressed table of whole values. */
   function projections(values: Record<string, unknown>): StatsLineProps['useProjection'] {
     return (key: string) => values[key]
@@ -281,6 +291,69 @@ describe('StatsLine', () => {
     expect(view.container.textContent).toBe('1 turns · 1 steps')
   })
 
+  it('renders whole-session counts from the sessionStats projection over the paged window', () => {
+    // The bug's acceptance at unit level: one loaded page must not scope the
+    // counter — the durable projection's totals win over the window fold.
+    const { source } = makeSource({ nodes: [assistant(1, 1)] })
+    const view = render(<StatsLine {...props(source, {
+      tokenUsage: USAGE,
+      sessionStats: sessionStats({ turns: 10, steps: 89 }),
+    })} />)
+    expect(view.container.textContent)
+      .toBe('10 turns · 89 steps| Cache hit 90%| Input 100 tok · Output 5 tok')
+  })
+
+  it('treats a defined zero-count projection as empty, not as fallback', () => {
+    // A composed unit always serves the key; all-zero genuinely means no
+    // closed step in the whole log, so nothing renders on a brand-new session.
+    const empty = makeSource()
+    const view = render(<StatsLine {...props(empty.source, {
+      tokenUsage: { uncachedInputTokens: 0, outputTokens: 0, cacheReadTokens: 0, cacheWriteTokens: 0 },
+      sessionStats: sessionStats({}),
+    })} />)
+    expect(view.container.textContent).toBe('')
+  })
+
+  it('hides the zero-token group when steps closed without any billed activity', () => {
+    // A session whose only turn failed before billing (e.g. an auth error):
+    // the counts group renders alone, not an uninformative zero-token group.
+    const { source } = makeSource()
+    const view = render(<StatsLine {...props(source, {
+      tokenUsage: { uncachedInputTokens: 0, outputTokens: 0, cacheReadTokens: 0, cacheWriteTokens: 0 },
+      sessionStats: sessionStats({ turns: 1, steps: 1 }),
+    })} />)
+    expect(view.container.textContent).toBe('1 turns · 1 steps')
+  })
+
+  it('keeps the counts group over an empty visible window when the projection carries totals', () => {
+    // Extends the durable-groups guarantee: full-session counts survive a
+    // window that compaction (or paging) left without assistant nodes.
+    const { source } = makeSource()
+    const view = render(<StatsLine {...props(source, {
+      tokenUsage: USAGE,
+      sessionStats: sessionStats({ turns: 7, steps: 44 }),
+    })} />)
+    expect(view.container.textContent)
+      .toBe('7 turns · 44 steps| Cache hit 90%| Input 100 tok · Output 5 tok')
+  })
+
+  it('renders whole-log wall times and speeds from the projection, not the loaded window', () => {
+    // The 加载更早 hazard beyond counts: LLM/tool durations and the TTFT and
+    // throughput figures must not grow per loaded page either. An untimed
+    // 1-node window renders the projection's whole-log figures verbatim.
+    const { source } = makeSource({ nodes: [assistant(1, 1)] })
+    const view = render(<StatsLine {...props(source, {
+      tokenUsage: USAGE,
+      sessionStats: sessionStats({
+        turns: 200, steps: 200, llmMs: 100_000, toolMs: 62_000,
+        ttftMs: 1_600, ttftSteps: 2, decodeMs: 3_000, decodeTokens: 60,
+      }),
+    })} />)
+    expect(view.container.textContent).toBe(
+      '200 turns · 200 steps| LLM 1m40s · Tool call 1m2s| TTFT avg 0.8s · 20 tok/s| Cache hit 90%| Input 100 tok · Output 5 tok',
+    )
+  })
+
   it('omits cache hit when nothing was billed on the input side', () => {
     const { source } = makeSource({ nodes: [assistant(1, 1)] })
     const view = render(<StatsLine {...props(source, {
diff --git a/packages/client/ui-conversation/tests/gate-branch-tails.client.spec.tsx b/packages/client/ui-conversation/tests/gate-branch-tails.client.spec.tsx
index a2af45fbd0..529975cb08 100644
--- a/packages/client/ui-conversation/tests/gate-branch-tails.client.spec.tsx
+++ b/packages/client/ui-conversation/tests/gate-branch-tails.client.spec.tsx
@@ -70,9 +70,11 @@ describe('render branch tails', () => {
     expect(view.container.querySelector('[data-state="ok"]')).not.toBeNull()
   })
 
-  it('StatsLine counts window nodes but drops every token group without a projection', () => {
-    // Node `usage` is deliberately ignored: billing rides the durable
-    // tokenUsage projection, so an absent projection leaves counts only.
+  it('StatsLine falls back to window-node counts and drops every token group without projections', () => {
+    // No sessionStats key → the window fold supplies the counts (the
+    // assembly-without-the-unit fallback). Node `usage` is deliberately
+    // ignored: billing rides the durable tokenUsage projection, so an absent
+    // projection leaves counts only.
     const nodes = [
       { kind: 'assistant', seq: 1, time: 1, turn: 1, step: 1, blocks: [] },
       { kind: 'assistant', seq: 2, time: 2, turn: 1, step: 2, blocks: [], usage: { inputTokens: 4, outputTokens: 6 } },
diff --git a/packages/client/ui-conversation/tsconfig.json b/packages/client/ui-conversation/tsconfig.json
index 0ef0bd8a19..b9ac320842 100644
--- a/packages/client/ui-conversation/tsconfig.json
+++ b/packages/client/ui-conversation/tsconfig.json
@@ -44,6 +44,9 @@
     {
       "path": "../../session/session-projection"
     },
+    {
+      "path": "../../session/session-stats"
+    },
     {
       "path": "../../llm/token-meter"
     },
diff --git a/packages/llm/llm/src/message.ts b/packages/llm/llm/src/message.ts
index 7863e66d58..45c0315a2a 100644
--- a/packages/llm/llm/src/message.ts
+++ b/packages/llm/llm/src/message.ts
@@ -2,7 +2,7 @@
 
 import { MessageId, type CallId } from './brand.ts'
 import { deepFreeze } from './call-config.ts'
-import type { ContentBlock, ToolResultBlock } from './types.ts'
+import type { ContentBlock, StreamChunk, ToolResultBlock } from './types.ts'
 
 /** Provider/model identity and adapter-private replay data for an assistant message. */
 export interface AssistantProvenance {
@@ -239,3 +239,23 @@ export function createToolResultMessage(input: ToolResultMessageInput): ToolResu
     }],
   })
 }
+
+/**
+ * Whether a stream chunk carries visible model output (the first-token
+ * boundary shared by client step timing and the whole-log sessionStats
+ * projection). Empty deltas (heartbeats, empty tool-call frames) do not count
+ * as a first token.
+ * @param chunk - the stream chunk to test.
+ * @returns true when the chunk contains a non-empty text/reasoning/tool delta.
+ */
+export function isTokenDelta(chunk: StreamChunk): boolean {
+  switch (chunk.type) {
+    case 'text-delta':
+    case 'reasoning-delta':
+      return chunk.text !== ''
+    case 'tool-call-delta':
+      return chunk.argumentsDelta !== '' || chunk.name !== undefined
+    default:
+      return false
+  }
+}
diff --git a/packages/session/README.i18n.yaml b/packages/session/README.i18n.yaml
index 13ccbab301..1271af2aa7 100644
--- a/packages/session/README.i18n.yaml
+++ b/packages/session/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/session/README.md
-README.md: 586d1be0286a0de935b0b08313e6965452b85376
-README.zh.md: 7947468ce2107c41134a83c6985108db00edc430
+README.md: 64aa8e4fdf1e85d74dfa0a77803a04e881b547c4
+README.zh.md: 14ff59fa137c74202c31dadc243a5c21fc15ab47
diff --git a/packages/session/README.md b/packages/session/README.md
index 586d1be028..64aa8e4fdf 100644
--- a/packages/session/README.md
+++ b/packages/session/README.md
@@ -25,6 +25,7 @@ Serves current, log-derived per-session state to client carriers.
 |---|---|---|
 | [`session-projection/`](session-projection/README.md) | Defines and drives session projection units | `ctx.sessionProjections` |
 | [`session-projection-cache/`](session-projection-cache/README.md) | Persists and restores projection checkpoints | `ctx.sessionProjectionCache` |
+| [`session-stats/`](session-stats/README.md) | Serves whole-log conversation counts and wall times (`sessionStats` unit) | registers on `ctx.sessionProjections` |
 
 ## Titles
 
diff --git a/packages/session/README.zh.md b/packages/session/README.zh.md
index 7947468ce2..14ff59fa13 100644
--- a/packages/session/README.zh.md
+++ b/packages/session/README.zh.md
@@ -25,6 +25,7 @@
 |---|---|---|
 | [`session-projection/`](session-projection/README.md) | 定义并驱动会话投影单元 | `ctx.sessionProjections` |
 | [`session-projection-cache/`](session-projection-cache/README.md) | 持久化并恢复投影检查点 | `ctx.sessionProjectionCache` |
+| [`session-stats/`](session-stats/README.md) | 提供全日志会话计数与墙钟时间（`sessionStats` 单元） | 注册到 `ctx.sessionProjections` |
 
 ## 标题
 
diff --git a/packages/session/session-stats/README.i18n.yaml b/packages/session/session-stats/README.i18n.yaml
new file mode 100644
index 0000000000..d12db01c69
--- /dev/null
+++ b/packages/session/session-stats/README.i18n.yaml
@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# side as of the last confirmed-consistent state. Both languages carry equal authority;
+# after editing either side, bring the other along and re-record with:
+#   pnpm run verify-translation-pairing --write packages/session/session-stats/README.md
+README.md: 81b0de17e335b67936afd6fb11f15411beee3b76
+README.zh.md: 606628ea09bc34203a5374e49db62c1646293846
diff --git a/packages/session/session-stats/README.md b/packages/session/session-stats/README.md
new file mode 100644
index 0000000000..81b0de17e3
--- /dev/null
+++ b/packages/session/session-stats/README.md
@@ -0,0 +1,39 @@
+# @deepseek-ai/dsh-session-stats
+
+English | [中文](README.zh.md)
+
+Function plugin registering the `sessionStats` projection unit: whole-log conversation figures — turn/step counts and the LLM, tool, first-token, and decode wall times — folded from step boundaries, stream chunks, tool pairs, and assembled assistant messages, and served through the session-projection seam (registry snapshot, change feed, and every projection carrier: history tail page, `session/projection` push frames, session list rows). Clients render full-session figures that paging and compaction cannot change; the reference consumer is the web chat stats strip, whose window fold mirrors these field names as its no-unit fallback.
+
+## Fold semantics
+
+- `steps` counts `step/end` events. The agent loop appends exactly one per entered step, in a `finally`, so completed, failed, cancelled, and max-tokens steps all count. Counting assembled assistant messages instead would overcount max-tokens usage-host messages (empty content, excluded from the surface) and undercount cancelled steps (aborted before the message assembles).
+- `turns` counts distinct turns carrying at least one closed step; rejected or empty turns (closed with no step) are uncounted. Turn numbers are host-assigned and monotonic per session, so the fold keeps only the last counted turn.
+- `llmMs` sums `step/start` → `assistant/message` per step that assembled a message (retry waits inside the step are model time, as in the window fold).
+- `ttftMs`/`ttftSteps` sum and count `step/start` → first non-empty delta chunk; the first attempt's boundary survives an in-step `llm/retry` (window `resetForRetry` parity).
+- `decodeMs`/`decodeTokens` sum first token → assembled message and the provider-reported output tokens, only over steps carrying both.
+- `toolMs` sums `tool/call` → `tool/result` pairs matched by callId; unresolved calls are dropped at `turn/end` (results land within their turn).
+- Every field is 0 until its first contributing event. A composed registry always serves the key, so clients read the value, never key presence.
+
+## Composition
+
+```yaml
+- id: session-stats
+  name: '@deepseek-ai/dsh-session-stats'
+```
+
+Injects `sessionProjections` — the plugin's whole purpose; in assemblies without the registry the fiber stays pending and nothing registers.
+
+## Model Experience
+
+None, as the plugin only computes a client-facing read model of already-logged session events and touches no prompt, message, schema, stream, or tool result.
+
+#### KV Cache effect
+
+None; the plugin never assembles or sends provider requests.
+
+## Known Limitations and Deferred Work
+
+- **Steps count work attempted, not visible output** — a step that failed before producing any visible content still closed with `step/end` and counts; a step interrupted by a crash counts after the session reloads, when crash recovery appends its synthetic `step/end` (`interruptedTurnClosers` in dsh-session).
+- **A cancelled step is counted but untimed** — no assistant message assembles, so its partial stream time enters no wall-time figure, matching the window fold's untimed interrupted node; a max-tokens usage-host message conversely contributes model time the surface does not show.
+- **Counts are log-scoped, not surface-scoped** — steps whose messages were later compacted away stay counted; the figures describe the whole session, not the current model-visible surface.
+- **Mounted only in the web-app bundle** — other assemblies serve no `sessionStats` key, and their consumers fall back to window-scoped counting (the web stats strip's fallback path).
diff --git a/packages/session/session-stats/README.zh.md b/packages/session/session-stats/README.zh.md
new file mode 100644
index 0000000000..606628ea09
--- /dev/null
+++ b/packages/session/session-stats/README.zh.md
@@ -0,0 +1,39 @@
+# @deepseek-ai/dsh-session-stats
+
+[English](README.md) | 中文
+
+注册 `sessionStats` projection 单元的函数插件：从步边界、流式 chunk、工具配对与已组装的 assistant 消息折叠出全日志会话数字——轮/步计数以及 LLM、工具、首 token、解码墙钟时间——经 session-projection 缝对外提供（registry 快照、变更流，以及每一个 projection 载体：history 尾页、`session/projection` 推送帧、会话列表行）。客户端由此渲染分页与压缩都无法改变的全会话数字；参考消费者是 Web 聊天统计条，其窗口折叠以相同字段名充当无单元时的回退。
+
+## 折叠语义
+
+- `steps` 统计 `step/end` 事件。agent loop 对每个进入的步在 `finally` 中恰好追加一条，因此完成、失败、取消、max-tokens 的步全部计入。若改按已组装的 assistant 消息计数，则会多算 max-tokens 的 usage 宿主消息（空内容、被排除在 surface 之外），并少算被取消的步（在消息组装前已中止）。
+- `turns` 统计含至少一个已关闭步的不同 turn；被拒绝或空轮（未进入任何步即关闭）不计。turn 号由宿主分配、按会话单调递增，因此折叠只需保留最近计入的 turn。
+- `llmMs` 按步累加 `step/start` → `assistant/message`（组装出消息的步；步内重试的等待与窗口折叠一样计入模型时间）。
+- `ttftMs`/`ttftSteps` 累加并统计 `step/start` → 首个非空 delta chunk；首次尝试的边界在步内 `llm/retry` 后保留（与窗口 `resetForRetry` 对齐）。
+- `decodeMs`/`decodeTokens` 累加首 token → 已组装消息的时长与提供方上报的输出 token，仅统计两者兼备的步。
+- `toolMs` 按 callId 配对累加 `tool/call` → `tool/result`；未解决的调用在 `turn/end` 时丢弃（结果总在其轮内落地）。
+- 每个字段在首个贡献事件之前均为 0。已装配的 registry 恒提供该键，客户端读取值本身，而非键的存在性。
+
+## 组合
+
+```yaml
+- id: session-stats
+  name: '@deepseek-ai/dsh-session-stats'
+```
+
+注入 `sessionProjections`——这是插件的全部用途；在没有 registry 的装配中 fiber 保持挂起，不注册任何内容。
+
+## 模型体验
+
+无，因为插件只计算面向客户端的、由已写入日志的会话事件派生的读模型，不触碰任何提示词、消息、schema、流或工具结果。
+
+#### KV Cache 影响
+
+无；插件从不组装或发送提供方请求。
+
+## 已知局限与延后工作
+
+- **步数统计的是已发生的工作，而非可见输出**——在产生任何可见内容前就失败的步仍以 `step/end` 关闭并计入；被崩溃打断的步在会话重新加载后计入，届时崩溃恢复为其补写合成的 `step/end`（dsh-session 的 `interruptedTurnClosers`）。
+- **被取消的步计数但不计时**——没有组装出 assistant 消息，其部分流式时间不进入任何墙钟数字，与窗口折叠的无计时 interrupted 节点一致；反之 max-tokens 的 usage 宿主消息贡献 surface 上看不到的模型时间。
+- **计数是日志口径，不是 surface 口径**——消息后来被压缩掉的步仍然计入；数字描述整个会话，而非当前模型可见 surface。
+- **仅挂载于 web-app bundle**——其他装配不提供 `sessionStats` 键，其消费者回退到窗口口径计数（Web 统计条的回退路径）。
diff --git a/packages/session/session-stats/package.json b/packages/session/session-stats/package.json
new file mode 100644
index 0000000000..f029ce83b9
--- /dev/null
+++ b/packages/session/session-stats/package.json
@@ -0,0 +1,62 @@
+{
+  "name": "@deepseek-ai/dsh-session-stats",
+  "description": "Whole-log conversation counts and wall times projection (sessionStats) for the DeepSeek Harness",
+  "version": "0.0.1-rc.2",
+  "publishConfig": {
+    "access": "restricted"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/deepseek-ai/deepseek-harness.git",
+    "directory": "packages/session/session-stats"
+  },
+  "type": "module",
+  "main": "lib/index.js",
+  "types": "lib/types/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./lib/types/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
+    "./types": {
+      "types": "./lib/types/types.d.ts",
+      "default": "./lib/types/types.js"
+    },
+    "./client": {
+      "types": "./lib/types/client.d.ts",
+      "default": "./lib/types/client.js"
+    },
+    "./src/*": "./src/*",
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "lib/index.js",
+    "lib/invariant.js",
+    "lib/types/**/*.js",
+    "lib/types/**/*.d.ts"
+  ],
+  "license": "BSD-3-Clause",
+  "peerDependencies": {
+    "@deepseek-ai/dsh-invariants": "workspace:^",
+    "@deepseek-ai/dsh-llm": "workspace:^",
+    "@deepseek-ai/dsh-session": "workspace:^",
+    "@deepseek-ai/dsh-session-projection": "workspace:^",
+    "@deepseek-ai/cordis": "workspace:^"
+  },
+  "dependencies": {
+    "zod": "^4.4.3"
+  },
+  "devDependencies": {
+    "@deepseek-ai/cordis-plugin-include": "workspace:^",
+    "@deepseek-ai/cordis-plugin-loader": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
+    "@deepseek-ai/dsh-llm": "workspace:^",
+    "@deepseek-ai/dsh-session": "workspace:^",
+    "@deepseek-ai/dsh-session-projection": "workspace:^",
+    "@deepseek-ai/cordis": "workspace:^"
+  }
+}
diff --git a/packages/session/session-stats/src/client.ts b/packages/session/session-stats/src/client.ts
new file mode 100644
index 0000000000..9f6adc5356
--- /dev/null
+++ b/packages/session/session-stats/src/client.ts
@@ -0,0 +1,10 @@
+/**
+ * Client-namespace projection of the session-stats domain: a pure re-export
+ * of the package's types outlet. Client code imports ONLY the client
+ * namespace (repo discipline), so `./client` projects the same single-source
+ * content `./types` serves to host consumers — zero duplication.
+ *
+ * @module @deepseek-ai/dsh-session-stats/client
+ */
+
+export type * from './types.ts'
diff --git a/packages/session/session-stats/src/index.ts b/packages/session/session-stats/src/index.ts
new file mode 100644
index 0000000000..54679b6e78
--- /dev/null
+++ b/packages/session/session-stats/src/index.ts
@@ -0,0 +1,29 @@
+/**
+ * Function plugin registering the `sessionStats` projection unit: whole-log
+ * turn/step counts and LLM/tool/first-token/decode wall times served through
+ * the session-projection seam (registry snapshot, change feed, and every
+ * projection carrier), so clients render full-session figures that paging and
+ * compaction cannot change. The plugin owns only the fold; delivery is the
+ * seam's.
+ *
+ * @module @deepseek-ai/dsh-session-stats
+ */
+
+import type { Context } from '@deepseek-ai/cordis'
+import { sessionStatsProjectionDefinition } from './projection.ts'
+
+export type * from './types.ts'
+
+/** Cordis plugin name. */
+export const name = 'session-stats'
+/** The projection registry is the plugin's whole purpose; without it the fiber stays pending. */
+export const inject = ['sessionProjections']
+
+/**
+ * Register the `sessionStats` unit; the registration is an effect on this
+ * plugin's fiber, so unloading removes the key.
+ * @param ctx - registrant context carrying the projection registry.
+ */
+export function apply(ctx: Context): void {
+  ctx.sessionProjections.register(sessionStatsProjectionDefinition)
+}
diff --git a/packages/session/session-stats/src/invariant.ts b/packages/session/session-stats/src/invariant.ts
new file mode 100644
index 0000000000..582e5dcdb4
--- /dev/null
+++ b/packages/session/session-stats/src/invariant.ts
@@ -0,0 +1,35 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-session-stats`.
+ * @module @deepseek-ai/dsh-session-stats/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from '@deepseek-ai/cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-session-stats'
+
+/** Cordis companion plugin name. */
+export const name = 'session-stats-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: the package owns a single pure projection fold whose
+ * wire payload is schema-validated by the projection registry at every
+ * snapshot and change-feed emission, and the event relations the fold relies
+ * on (`step/end` exactly once per entered step, monotonic host-assigned turn
+ * numbers, chunk and tool events carrying their step coordinates and call
+ * ids) are owned and runtime-checked by dsh-agent-loop and the session
+ * surface, not here.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */
diff --git a/packages/session/session-stats/src/projection.ts b/packages/session/session-stats/src/projection.ts
new file mode 100644
index 0000000000..a000300873
--- /dev/null
+++ b/packages/session/session-stats/src/projection.ts
@@ -0,0 +1,183 @@
+/**
+ * The `sessionStats` projection unit: a pure fold of step boundaries, stream
+ * chunks, tool pairs, and assembled assistant messages into whole-log counts
+ * and wall times.
+ *
+ * `step/end` — not `assistant/message` — is the counted step event because it
+ * is the step lifecycle authority: the loop appends exactly one per entered
+ * step, in a `finally`, so completed, failed, cancelled, and max-tokens steps
+ * all land one. Counting assembled assistant messages instead would overcount
+ * max-tokens usage-host messages (empty content, excluded from the surface)
+ * and undercount cancelled steps (aborted before the message assembles).
+ *
+ * The wall-time folds mirror the client window fold field by field
+ * (`deriveStats` in dsh-client-ui-conversation, that fold's whole-window
+ * fallback role): model time is `step/start` → `assistant/message`, first
+ * token is the first non-empty delta chunk and survives an in-step
+ * `llm/retry`, decode spans first token → assembled message on steps that
+ * also report output tokens, and tool time pairs `tool/call` → `tool/result`
+ * by callId. A cancelled step assembles no message, so its partial stream
+ * time stays uncounted in every time figure — matching the window, which
+ * renders it as an untimed interrupted node.
+ *
+ * @module @deepseek-ai/dsh-session-stats/projection
+ */
+
+import { z } from 'zod'
+import { isTokenDelta } from '@deepseek-ai/dsh-llm/message'
+import type { ProjectionDefinition } from '@deepseek-ai/dsh-session-projection'
+
+/** Accumulated whole-log figures (the view is exactly these totals). */
+interface SessionStatsTotals {
+  /** Distinct turns with at least one closed step so far. */
+  turns: number
+  /** Closed steps so far. */
+  steps: number
+  /** Summed model wall time over message-assembling steps, ms. */
+  llmMs: number
+  /** Summed matched tool call→result wall time, ms. */
+  toolMs: number
+  /** Summed first-token latency over `ttftSteps`, ms. */
+  ttftMs: number
+  /** Steps carrying a recorded first token. */
+  ttftSteps: number
+  /** Summed decode wall time over usage-reporting steps, ms. */
+  decodeMs: number
+  /** Summed provider output tokens over the same steps. */
+  decodeTokens: number
+}
+
+/**
+ * Fold state: the totals plus the in-flight boundaries they accrue from.
+ * Turn numbers are host-assigned and monotonic per session, so a single
+ * `lastTurn` slot decides "first closed step of a new turn"; the state is
+ * plain JSON per the unit contract (persisted-cache precondition).
+ */
+interface SessionStatsState extends SessionStatsTotals {
+  /** Turn of the last counted `step/end`; null before the first. */
+  lastTurn: number | null
+  /** The open step's boundary facts; null outside a step or after its message assembled. */
+  openStep: { turn: number; step: number; startTime: number; firstTokenTime: number | null } | null
+  /** Dispatch times of tool calls whose result has not landed, by callId. */
+  pendingCalls: Record<string, number>
+}
+
+const sessionStatsSchema = z.object({
+  turns: z.number().int().nonnegative(),
+  steps: z.number().int().nonnegative(),
+  llmMs: z.number().nonnegative(),
+  toolMs: z.number().nonnegative(),
+  ttftMs: z.number().nonnegative(),
+  ttftSteps: z.number().int().nonnegative(),
+  decodeMs: z.number().nonnegative(),
+  decodeTokens: z.number().nonnegative(),
+}).strict()
+
+/**
+ * Provider-reported completion tokens, guarded the way the window fold guards
+ * node usage.
+ * @param usage - the assistant/message event's optional usage record.
+ * @returns the output-token count, or null when unreported or invalid.
+ */
+function usageOutputTokens(usage: unknown): number | null {
+  if (typeof usage !== 'object' || usage === null) return null
+  const value = (usage as { outputTokens?: unknown }).outputTokens
+  return typeof value === 'number' && Number.isFinite(value) && value >= 0 ? value : null
+}
+
+/** The `sessionStats` unit registered on `ctx.sessionProjections` (exported for the unit spec). */
+export const sessionStatsProjectionDefinition: ProjectionDefinition<'sessionStats', SessionStatsState> = {
+  key: 'sessionStats',
+  schema: sessionStatsSchema,
+  init: () => ({
+    turns: 0,
+    steps: 0,
+    llmMs: 0,
+    toolMs: 0,
+    ttftMs: 0,
+    ttftSteps: 0,
+    decodeMs: 0,
+    decodeTokens: 0,
+    lastTurn: null,
+    openStep: null,
+    pendingCalls: {},
+  }),
+  apply: (state, event) => {
+    // Every uninteresting event returns the same reference (Object.is gates the change feed).
+    switch (event.type) {
+      case 'step/start':
+        return {
+          ...state,
+          openStep: { turn: event.data.turn, step: event.data.step, startTime: event.time, firstTokenTime: null },
+        }
+      case 'assistant/chunk': {
+        const open = state.openStep
+        if (open === null || open.turn !== event.data.turn || open.step !== event.data.step) return state
+        if (open.firstTokenTime !== null || !isTokenDelta(event.data.chunk)) return state
+        return { ...state, openStep: { ...open, firstTokenTime: event.time } }
+      }
+      case 'assistant/message': {
+        const open = state.openStep
+        if (open === null || open.turn !== event.data.turn || open.step !== event.data.step) return state
+        // One assembled message per step: closing the boundary means a
+        // defensive duplicate cannot accrue twice.
+        const next: SessionStatsState = {
+          ...state,
+          llmMs: state.llmMs + Math.max(0, event.time - open.startTime),
+          openStep: null,
+        }
+        if (open.firstTokenTime !== null) {
+          next.ttftMs += Math.max(0, open.firstTokenTime - open.startTime)
+          next.ttftSteps += 1
+          const outputTokens = usageOutputTokens(event.data.usage)
+          if (outputTokens !== null) {
+            next.decodeMs += Math.max(0, event.time - open.firstTokenTime)
+            next.decodeTokens += outputTokens
+          }
+        }
+        return next
+      }
+      case 'tool/call':
+        return { ...state, pendingCalls: { ...state.pendingCalls, [event.data.callId]: event.time } }
+      case 'tool/result': {
+        // Own-key check: callId is provider-minted (model/tool JSON boundary),
+        // so a prototype property name ('constructor', 'toString') on a result
+        // with no recorded call must read as unmatched, not as an inherited
+        // function that would poison toolMs with NaN.
+        const callId = event.data.message.source.callId
+        const dispatched = Object.hasOwn(state.pendingCalls, callId) ? state.pendingCalls[callId] : undefined
+        if (dispatched === undefined) return state
+        const pendingCalls = Object.fromEntries(
+          Object.entries(state.pendingCalls).filter(([id]) => id !== callId),
+        )
+        return { ...state, toolMs: state.toolMs + Math.max(0, event.time - dispatched), pendingCalls }
+      }
+      case 'step/end':
+        return {
+          ...state,
+          turns: state.lastTurn === event.data.turn ? state.turns : state.turns + 1,
+          steps: state.steps + 1,
+          lastTurn: event.data.turn,
+          openStep: null,
+        }
+      case 'turn/end':
+        // A call whose result never landed belongs to a cancelled or failed
+        // turn; results always land within their turn, so drop the leftovers
+        // instead of growing persisted state forever.
+        return Object.keys(state.pendingCalls).length === 0 ? state : { ...state, pendingCalls: {} }
+      default:
+        return state
+    }
+  },
+  view: state => ({
+    turns: state.turns,
+    steps: state.steps,
+    llmMs: state.llmMs,
+    toolMs: state.toolMs,
+    ttftMs: state.ttftMs,
+    ttftSteps: state.ttftSteps,
+    decodeMs: state.decodeMs,
+    decodeTokens: state.decodeTokens,
+  }),
+  stateVersion: 1,
+}
diff --git a/packages/session/session-stats/src/types.ts b/packages/session/session-stats/src/types.ts
new file mode 100644
index 0000000000..e11a300b19
--- /dev/null
+++ b/packages/session/session-stats/src/types.ts
@@ -0,0 +1,46 @@
+/**
+ * Pure types of the session-stats domain: the ONE home of the `sessionStats`
+ * projection-key declaration, free of this package's host-side value imports
+ * (cordis context, zod, the llm chunk predicate). Two namespace projections
+ * serve it — `./types` for host consumers, `./client` for client aggregates —
+ * with zero content duplication.
+ *
+ * @module @deepseek-ai/dsh-session-stats/types
+ */
+
+// Marks this file a module so the declaration below AUGMENTS the projection
+// table instead of declaring an ambient module.
+export {}
+
+/**
+ * Whole-log conversation figures, independent of how much history a client
+ * has paged in. Counts and wall times all fold from the complete durable log;
+ * every field is 0 until its first contributing event lands. Field names
+ * mirror the client window fold so an assembly without this unit can fall
+ * back to it wholesale.
+ */
+export interface SessionStatsProjection {
+  /** Distinct turns carrying at least one closed step (`step/end`); rejected or empty turns are uncounted. */
+  turns: number
+  /** Closed steps (`step/end` events) — completed, failed, and cancelled steps alike. */
+  steps: number
+  /** Summed model wall time (`step/start` → `assistant/message`) over steps that assembled a message. */
+  llmMs: number
+  /** Summed tool wall time over `tool/call` → `tool/result` pairs matched by callId. */
+  toolMs: number
+  /** Summed first-token latency (`step/start` → first non-empty delta chunk) over `ttftSteps`. */
+  ttftMs: number
+  /** Steps carrying a recorded first token. */
+  ttftSteps: number
+  /** Summed decode wall time (first token → `assistant/message`) over steps that also report output tokens. */
+  decodeMs: number
+  /** Summed provider output tokens over the same decode-timed steps. */
+  decodeTokens: number
+}
+
+declare module '@deepseek-ai/dsh-session-projection/types' {
+  interface SessionProjectionMap {
+    /** Whole-log turn/step counts and wall times; see {@link SessionStatsProjection}. */
+    sessionStats: SessionStatsProjection
+  }
+}
diff --git a/packages/session/session-stats/tests/loader-composition.spec.ts b/packages/session/session-stats/tests/loader-composition.spec.ts
new file mode 100644
index 0000000000..e3889eaeb4
--- /dev/null
+++ b/packages/session/session-stats/tests/loader-composition.spec.ts
@@ -0,0 +1,86 @@
+/**
+ * REAL-composition proof: the shipped YAML shape (session + projection
+ * registry + session-stats) boots through the vendored Loader, the function
+ * plugin's namespace survives (no default export), and a full logged turn
+ * serves `{turns: 1, steps: 1}` through the composed registry.
+ */
+
+import { mkdtemp, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { pathToFileURL } from 'node:url'
+import { afterEach, describe, expect, it } from 'vitest'
+import { Context } from '@deepseek-ai/cordis'
+import Loader from '@deepseek-ai/cordis-plugin-loader'
+import Include from '@deepseek-ai/cordis-plugin-include'
+import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
+import SessionProjectionRegistry from '@deepseek-ai/dsh-session-projection'
+import * as SessionStatsPlugin from '@deepseek-ai/dsh-session-stats'
+
+let root: string | undefined
+let context: Context | undefined
+
+afterEach(async () => {
+  await context?.fiber.dispose()
+  context = undefined
+  if (root !== undefined) await rm(root, { recursive: true, force: true })
+  root = undefined
+})
+
+async function loadYaml(lines: readonly string[]): Promise<Context> {
+  root = await mkdtemp(join(tmpdir(), 'dsh-session-stats-loader-'))
+  const configPath = join(root, 'cordis.yml')
+  await writeFile(configPath, [...lines, ''].join('\n'))
+
+  context = new Context()
+  context.baseUrl = pathToFileURL(root).href + '/'
+  await context.plugin(Loader)
+  context.loader.builtins.include = Include
+  const modules = new Map<string, unknown>([
+    ['@deepseek-ai/dsh-session', SessionStore],
+    ['@deepseek-ai/dsh-session-projection', SessionProjectionRegistry],
+    ['@deepseek-ai/dsh-session-stats', SessionStatsPlugin],
+  ])
+  context.loader.internal = {
+    version: 'v2',
+    async import(specifier: string) {
+      if (!modules.has(specifier)) throw new Error(`unexpected Loader import: ${specifier}`)
+      return modules.get(specifier)
+    },
+  } as unknown as NonNullable<typeof context.loader.internal>
+  await context.loader.create({
+    name: 'cordis:include',
+    config: { path: pathToFileURL(configPath).href },
+  })
+  await context.loader.await()
+  return context
+}
+
+describe('real Loader composition', () => {
+  it('loads the shipped session-stats YAML shape and serves whole-log counts', async () => {
+    const loaded = await loadYaml([
+      "- name: '@deepseek-ai/dsh-session'",
+      "- name: '@deepseek-ai/dsh-session-projection'",
+      "- name: '@deepseek-ai/dsh-session-stats'",
+    ])
+
+    const unloaded = [...loaded.loader.entries()]
+      .filter(entry => entry.fiber === undefined && !entry.disabled)
+      .map(entry => entry.options.name)
+    expect(unloaded).toEqual([])
+
+    const session = loaded.sessions.create(SessionId('composed'))
+    session.append('turn/start', { turn: 1 })
+    session.append('step/start', { turn: 1, step: 1 })
+    session.append('step/end', { turn: 1, step: 1 })
+    session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
+    expect(loaded.sessionProjections.snapshot(session).values.sessionStats)
+      .toMatchObject({ turns: 1, steps: 1 })
+  })
+
+  it('keeps the function-plugin namespace free of a default export', () => {
+    // A default export beside the named form makes the Loader discard the
+    // namespace (postmortem 0001) — pin its absence.
+    expect('default' in SessionStatsPlugin).toBe(false)
+  })
+})
diff --git a/packages/session/session-stats/tests/projection.spec.ts b/packages/session/session-stats/tests/projection.spec.ts
new file mode 100644
index 0000000000..ebe728181b
--- /dev/null
+++ b/packages/session/session-stats/tests/projection.spec.ts
@@ -0,0 +1,292 @@
+/**
+ * The `sessionStats` projection unit: mounting the plugin beside the
+ * projection registry serves whole-log counts and wall times folded from step
+ * boundaries, chunks, tool pairs, and assembled messages; compositions
+ * without the registry are unaffected; unmounting the plugin removes the key
+ * (HMR safety). The two counting regressions pinned here are the reasons the
+ * fold counts step boundaries instead of assistant messages: a cancelled step
+ * never assembles a message but still counts, and a max-tokens usage-host
+ * message (empty content) adds no extra step. Wall-time math runs against the
+ * exported definition directly, where event times are controlled.
+ */
+
+import { describe, expect, it } from 'vitest'
+import { Context } from '@deepseek-ai/cordis'
+import { createMessage } from '@deepseek-ai/dsh-llm'
+import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
+import type { Session, SessionEvent } from '@deepseek-ai/dsh-session'
+import SessionProjectionRegistry from '@deepseek-ai/dsh-session-projection'
+import * as SessionStatsPlugin from '@deepseek-ai/dsh-session-stats'
+import { sessionStatsProjectionDefinition } from '@deepseek-ai/dsh-session-stats/src/projection.ts'
+import type { SessionStatsProjection } from '@deepseek-ai/dsh-session-stats/types'
+
+async function harness(withStatsPlugin: boolean): Promise<{ ctx: Context; session: Session }> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SessionProjectionRegistry)
+  if (withStatsPlugin) await ctx.plugin(SessionStatsPlugin)
+  return { ctx, session: ctx.sessions.create(SessionId('counted')) }
+}
+
+/** Close one step; returns the counted `step/end` seq. */
+function closeStep(session: Session, turn: number, step: number): number {
+  session.append('step/start', { turn, step })
+  return session.append('step/end', { turn, step }).seq
+}
+
+/** Append the max-tokens usage-host shape: an assistant/message with empty content. */
+function appendEmptyAssistantMessage(session: Session, turn: number, step: number): void {
+  session.append('assistant/message', {
+    turn,
+    step,
+    message: createMessage({
+      role: 'assistant',
+      content: [],
+      source: { kind: 'model', provider: 'mock', model: 'mock' },
+    }),
+  }, { surfaceOp: 'append', sourceEventSeqs: [] })
+}
+
+/** The all-zero projection value plus overrides, for exact fold expectations. */
+function totals(overrides: Partial<SessionStatsProjection> = {}): SessionStatsProjection {
+  return {
+    turns: 0, steps: 0, llmMs: 0, toolMs: 0, ttftMs: 0, ttftSteps: 0, decodeMs: 0, decodeTokens: 0,
+    ...overrides,
+  }
+}
+
+describe('sessionStats projection unit (registry drive)', () => {
+  it('serves zero figures on the empty log', async () => {
+    const { ctx, session } = await harness(true)
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats).toEqual(totals())
+  })
+
+  it('counts distinct turns and closed steps and notifies the change feed with the causing seq', async () => {
+    const { ctx, session } = await harness(true)
+    const changes: { key: string; value: unknown; seq: number }[] = []
+    ctx.sessionProjections.onChanged((_session, key, value, seq) => {
+      changes.push({ key, value, seq })
+    })
+    session.append('turn/start', { turn: 1 })
+    const firstSeq = closeStep(session, 1, 1)
+    const secondSeq = closeStep(session, 1, 2)
+    session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
+    session.append('turn/start', { turn: 2 })
+    const thirdSeq = closeStep(session, 2, 1)
+    session.append('turn/end', { turn: 2, reason: { kind: 'completed' } })
+    // Boundary events that carry no figure change (turn/start, empty-prune
+    // turn/end, user input) fold to the same reference and stay silent;
+    // step/start opens a boundary (internal state) and step/end commits the
+    // counts, so each closed step notifies twice with the step/end value last.
+    const counted = changes.filter(change => (change.value as SessionStatsProjection).steps > 0
+      || change.seq === firstSeq)
+    expect(changes.every(change => change.key === 'sessionStats')).toBe(true)
+    expect(counted.map(change => ({ seq: change.seq, value: change.value }))).toContainEqual(
+      { seq: firstSeq, value: totals({ turns: 1, steps: 1 }) },
+    )
+    expect(changes.at(-1)).toEqual({ key: 'sessionStats', value: totals({ turns: 2, steps: 3 }), seq: thirdSeq })
+    const snapshot = ctx.sessionProjections.snapshot(session)
+    expect(snapshot.values.sessionStats).toEqual(totals({ turns: 2, steps: 3 }))
+    expect(snapshot.asOfSeq).toBe(session.seq - 1)
+    expect(changes.map(change => change.seq)).toContain(secondSeq)
+  })
+
+  it('does not count a rejected or empty turn that closes with no step', async () => {
+    const { ctx, session } = await harness(true)
+    session.append('turn/start', { turn: 1 })
+    session.append('turn/end', { turn: 1, reason: { kind: 'blocked' } })
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats).toEqual(totals())
+  })
+
+  it('counts a cancelled step that closed without an assistant message', async () => {
+    // Regression: an aborted stream never assembles assistant/message, but the
+    // loop's finally still appends step/end — the step happened and counts.
+    const { ctx, session } = await harness(true)
+    session.append('turn/start', { turn: 1 })
+    closeStep(session, 1, 1)
+    session.append('turn/end', { turn: 1, reason: { kind: 'aborted', reason: { kind: 'legacy' } } })
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats)
+      .toMatchObject({ turns: 1, steps: 1 })
+  })
+
+  it('adds no extra step for a max-tokens usage-host assistant message', async () => {
+    // Regression: the empty-content assistant/message exists only to host
+    // usage and is excluded from the surface; the step counts once, from its
+    // step/end, while the message contributes only its model wall time.
+    const { ctx, session } = await harness(true)
+    session.append('turn/start', { turn: 1 })
+    session.append('step/start', { turn: 1, step: 1 })
+    appendEmptyAssistantMessage(session, 1, 1)
+    session.append('step/end', { turn: 1, step: 1 })
+    session.append('turn/end', { turn: 1, reason: { kind: 'max-tokens' } })
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats)
+      .toMatchObject({ turns: 1, steps: 1, ttftSteps: 0, decodeTokens: 0 })
+  })
+
+  it('folds steps already in the log when the plugin mounts late (lazy cell build)', async () => {
+    const { ctx, session } = await harness(false)
+    session.append('turn/start', { turn: 1 })
+    closeStep(session, 1, 1)
+    closeStep(session, 1, 2)
+    session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
+    await ctx.plugin(SessionStatsPlugin)
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats)
+      .toMatchObject({ turns: 1, steps: 2 })
+  })
+
+  it('has no sessionStats key without the plugin, and drops it when the plugin unloads (HMR safety)', async () => {
+    const { ctx, session } = await harness(false)
+    expect('sessionStats' in ctx.sessionProjections.snapshot(session).values).toBe(false)
+    const fiber = await ctx.plugin(SessionStatsPlugin)
+    session.append('turn/start', { turn: 1 })
+    closeStep(session, 1, 1)
+    expect(ctx.sessionProjections.snapshot(session).values.sessionStats)
+      .toMatchObject({ turns: 1, steps: 1 })
+    await fiber.dispose()
+    expect('sessionStats' in ctx.sessionProjections.snapshot(session).values).toBe(false)
+  })
+})
+
+/** Build one synthetic committed event with a controlled timestamp. */
+function at(time: number, type: string, data: unknown): SessionEvent {
+  return { type, seq: time, time, data } as unknown as SessionEvent
+}
+
+/** Fold a synthetic event list through the definition and view the result. */
+function fold(events: readonly SessionEvent[]): SessionStatsProjection {
+  const state = events.reduce(
+    (folded, event) => sessionStatsProjectionDefinition.apply(folded, event),
+    sessionStatsProjectionDefinition.init(),
+  )
+  return sessionStatsProjectionDefinition.view(state)
+}
+
+describe('sessionStats wall-time fold (controlled timestamps)', () => {
+  const message = createMessage({
+    role: 'assistant',
+    content: [{ type: 'text', text: 'answer' }],
+    source: { kind: 'model', provider: 'mock', model: 'mock' },
+  })
+
+  it('accrues model, first-token, and decode time from one fully recorded step', () => {
+    expect(fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_800, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'a' } }),
+      at(4_800, 'assistant/message', { turn: 1, step: 1, message, usage: { inputTokens: 10, outputTokens: 60 } }),
+      at(4_900, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({
+      turns: 1, steps: 1, llmMs: 3_800, ttftMs: 800, ttftSteps: 1, decodeMs: 3_000, decodeTokens: 60,
+    }))
+  })
+
+  it('keeps the first attempt token boundary across an in-step retry (window resetForRetry parity)', () => {
+    expect(fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_200, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'reasoning-delta', index: 0, text: 'x' } }),
+      at(2_000, 'llm/retry', { turn: 1, step: 1 }),
+      at(3_000, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'y' } }),
+      at(5_000, 'assistant/message', { turn: 1, step: 1, message }),
+      at(5_100, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1, llmMs: 4_000, ttftMs: 200, ttftSteps: 1 }))
+  })
+
+  it('ignores empty deltas, non-token chunks, and chunks outside the open step', () => {
+    expect(fold([
+      // Chunk before any step/start: no open boundary.
+      at(500, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'stray' } }),
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_100, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'block-start', index: 0, blockType: 'text' } }),
+      at(1_200, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: '' } }),
+      at(1_300, 'assistant/chunk', { turn: 2, step: 9, chunk: { type: 'text-delta', index: 0, text: 'other' } }),
+      at(1_400, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'first' } }),
+      at(2_000, 'assistant/message', { turn: 1, step: 1, message }),
+      at(2_100, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1, llmMs: 1_000, ttftMs: 400, ttftSteps: 1 }))
+  })
+
+  it('leaves a cancelled step untimed: counted by step/end, no assembled message to accrue from', () => {
+    expect(fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_500, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'partial' } }),
+      at(2_000, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1 }))
+  })
+
+  it('pairs tool wall time by callId, ignores orphan results, and prunes leftovers at turn/end', () => {
+    const result = (callId: string): unknown =>
+      ({ turn: 1, step: 1, message: { source: { kind: 'tool', callId } } })
+    const paired = fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_100, 'tool/call', { turn: 1, step: 1, callId: 'a', name: 'read', arguments: '{}' }),
+      at(1_200, 'tool/call', { turn: 1, step: 1, callId: 'b', name: 'read', arguments: '{}' }),
+      // Out-of-order settlement pairs by id, not adjacency.
+      at(4_200, 'tool/result', result('b')),
+      at(1_600, 'tool/result', result('a')),
+      at(5_000, 'tool/result', result('ghost')),
+      at(5_100, 'step/end', { turn: 1, step: 1 }),
+    ])
+    expect(paired).toEqual(totals({ turns: 1, steps: 1, toolMs: 3_500 }))
+    // An unresolved call is dropped at turn/end; a later result cannot pair.
+    const pruned = fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_100, 'tool/call', { turn: 1, step: 1, callId: 'orphan', name: 'read', arguments: '{}' }),
+      at(2_000, 'step/end', { turn: 1, step: 1 }),
+      at(2_100, 'turn/end', { turn: 1, reason: { kind: 'aborted', reason: { kind: 'legacy' } } }),
+      at(9_000, 'tool/result', result('orphan')),
+    ])
+    expect(pruned).toEqual(totals({ turns: 1, steps: 1 }))
+  })
+
+  it('pairs only own pendingCalls keys: a prototype-name callId without a recorded call stays unmatched', () => {
+    const result = (callId: string): unknown =>
+      ({ turn: 1, step: 1, message: { source: { kind: 'tool', callId } } })
+    // Crash recovery (TOOL_NOT_STARTED) emits results with no preceding
+    // tool/call; a provider-minted callId colliding with an Object prototype
+    // property must read as absent, not as an inherited function that would
+    // fold toolMs to NaN and fail the value schema.
+    expect(fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_500, 'tool/result', result('toString')),
+      at(2_000, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1 }))
+    // The same name pairs normally once its call is recorded.
+    expect(fold([
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_100, 'tool/call', { turn: 1, step: 1, callId: 'constructor', name: 'read', arguments: '{}' }),
+      at(1_600, 'tool/result', result('constructor')),
+      at(2_000, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1, toolMs: 500 }))
+  })
+
+  it('skips decode for an invalid usage report and ignores a duplicate assembled message', () => {
+    const events = [
+      at(1_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_400, 'assistant/chunk', { turn: 1, step: 1, chunk: { type: 'text-delta', index: 0, text: 'a' } }),
+      // A malformed provider report: guarded like the window fold guards node usage.
+      at(2_000, 'assistant/message', { turn: 1, step: 1, message, usage: { inputTokens: 1, outputTokens: -5 } }),
+    ]
+    expect(fold([...events, at(2_100, 'step/end', { turn: 1, step: 1 })]))
+      .toEqual(totals({ turns: 1, steps: 1, llmMs: 1_000, ttftMs: 400, ttftSteps: 1 }))
+    // The first message closed the step boundary; a defensive duplicate finds
+    // no open step and folds to the same reference.
+    const state = events.reduce(
+      (folded, event) => sessionStatsProjectionDefinition.apply(folded, event),
+      sessionStatsProjectionDefinition.init(),
+    )
+    expect(sessionStatsProjectionDefinition.apply(
+      state,
+      at(2_050, 'assistant/message', { turn: 1, step: 1, message }),
+    )).toBe(state)
+  })
+
+  it('accrues nothing for unrelated events and clamps negative clock skew to zero', () => {
+    const state = sessionStatsProjectionDefinition.init()
+    const untouched = sessionStatsProjectionDefinition.apply(state, at(1, 'user/message', { content: [] }))
+    expect(untouched).toBe(state)
+    expect(fold([
+      at(2_000, 'step/start', { turn: 1, step: 1 }),
+      at(1_000, 'assistant/message', { turn: 1, step: 1, message }),
+      at(2_100, 'step/end', { turn: 1, step: 1 }),
+    ])).toEqual(totals({ turns: 1, steps: 1 }))
+  })
+})
diff --git a/packages/session/session-stats/tsconfig.json b/packages/session/session-stats/tsconfig.json
new file mode 100644
index 0000000000..a6ed34022e
--- /dev/null
+++ b/packages/session/session-stats/tsconfig.json
@@ -0,0 +1,30 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cosmokit"
+    },
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../support/invariants"
+    },
+    {
+      "path": "../../llm/llm"
+    },
+    {
+      "path": "../../core/session"
+    },
+    {
+      "path": "../session-projection"
+    }
+  ]
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 364a560e38..7cfa693783 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1683,6 +1683,9 @@ importers:
       '@deepseek-ai/dsh-session-projection-cache':
         specifier: workspace:^
         version: link:../../session/session-projection-cache
+      '@deepseek-ai/dsh-session-stats':
+        specifier: workspace:^
+        version: link:../../session/session-stats
       '@deepseek-ai/dsh-storage':
         specifier: workspace:^
         version: link:../../storage/storage
@@ -2167,6 +2170,9 @@ importers:
       '@deepseek-ai/dsh-session-projection':
         specifier: workspace:^
         version: link:../../session/session-projection
+      '@deepseek-ai/dsh-session-stats':
+        specifier: workspace:^
+        version: link:../../session/session-stats
       '@deepseek-ai/dsh-token-meter':
         specifier: workspace:^
         version: link:../../llm/token-meter
@@ -6373,6 +6379,34 @@ importers:
         specifier: workspace:^
         version: link:../../storage/storage-domain
 
+  packages/session/session-stats:
+    dependencies:
+      zod:
+        specifier: ^4.4.3
+        version: 4.4.3
+    devDependencies:
+      '@deepseek-ai/cordis':
+        specifier: workspace:^
+        version: link:../../../vendor/cordis
+      '@deepseek-ai/cordis-plugin-include':
+        specifier: workspace:^
+        version: link:../../../vendor/include
+      '@deepseek-ai/cordis-plugin-loader':
+        specifier: workspace:^
+        version: link:../../../vendor/loader
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      '@deepseek-ai/dsh-llm':
+        specifier: workspace:^
+        version: link:../../llm/llm
+      '@deepseek-ai/dsh-session':
+        specifier: workspace:^
+        version: link:../../core/session
+      '@deepseek-ai/dsh-session-projection':
+        specifier: workspace:^
+        version: link:../session-projection
+
   packages/session/session-telemetry:
     devDependencies:
       '@deepseek-ai/cordis':
diff --git a/scripts/verify-package-readme-model-experience.ts b/scripts/verify-package-readme-model-experience.ts
index 813175b307..df6d1f44bd 100644
--- a/scripts/verify-package-readme-model-experience.ts
+++ b/scripts/verify-package-readme-model-experience.ts
@@ -123,6 +123,7 @@ const SENTENCE_MODEL_EXPERIENCE: Readonly<Record<string, SentenceContract>> = {
   'packages/sdk/protocol': { kind: 'none', reason: 'Client-facing wire library; the runtime plugins behind the serving entry own model-facing behavior.' },
   'packages/session/session-projection': { kind: 'none', reason: 'The projection registry serves client-facing read models of already-logged session state and registers nothing model-facing.' },
   'packages/session/session-projection-cache': { kind: 'none', reason: 'The persisted cache accelerates host-side cold reads of projection state and registers nothing model-facing.' },
+  'packages/session/session-stats': { kind: 'none', reason: 'The sessionStats unit folds already-logged step boundaries into a client-facing read model and registers nothing model-facing.' },
   'packages/session-query/session-query': { kind: 'none', reason: 'The trusted query service exposes cloned records only to callers and registers nothing model-facing.' },
   'packages/session-query/session-query-sqlite': { kind: 'none', reason: 'The search backend returns hits only to callers and registers nothing model-facing.' },
   'packages/settings/settings': { kind: 'indirect', reason: 'The seam stores and resolves user settings; consumer plugins own any model-facing content fed by a value.' },
diff --git a/tsconfig.base.json b/tsconfig.base.json
index 9f1b3f99f8..24cab53654 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -58,6 +58,8 @@
       "@deepseek-ai/dsh-tool-todo/client": ["./packages/todo/tool-todo/src/client.ts"],
       "@deepseek-ai/dsh-session-title/types": ["./packages/session/session-title/src/types.ts"],
       "@deepseek-ai/dsh-session-title/client": ["./packages/session/session-title/src/client.ts"],
+      "@deepseek-ai/dsh-session-stats/types": ["./packages/session/session-stats/src/types.ts"],
+      "@deepseek-ai/dsh-session-stats/client": ["./packages/session/session-stats/src/client.ts"],
       "@deepseek-ai/dsh-plan-mode/types": ["./packages/plan/plan-mode/src/types.ts"],
       "@deepseek-ai/dsh-plan-mode/client": ["./packages/plan/plan-mode/src/client.ts"],
       "@deepseek-ai/dsh-agent-presets/types": ["./packages/preset/agent-presets/src/types.ts"],
diff --git a/tsconfig.host.json b/tsconfig.host.json
index 3e25c9c510..b34cfd956a 100644
--- a/tsconfig.host.json
+++ b/tsconfig.host.json
@@ -35,6 +35,7 @@
     "apps/web/tests/replay-round-trip.e2e.ts",
     "apps/web/tests/hmr-live.e2e.ts",
     "apps/web/tests/seeded-history.e2e.ts",
+    "apps/web/tests/stats-paged-history.e2e.ts",
     "apps/web/tests/sidebar-scrollbar.e2e.ts",
     "apps/web/tests/conversation-column-overflow.e2e.ts",
     "apps/web/tests/code-mode-round.e2e.ts",
@@ -138,6 +139,7 @@
     { "path": "./packages/session/session-persistence-sqlite" },
     { "path": "./packages/session/session-projection" },
     { "path": "./packages/session/session-projection-cache" },
+    { "path": "./packages/session/session-stats" },
     { "path": "./packages/session-query/session-query" },
     { "path": "./packages/session-query/session-query-sqlite" },
     { "path": "./packages/settings/settings" },