feat(admin): 流程图方向——Flow 页自下而上（最新在上），Backthink/Agents 图块最新在左

主人要求：① 全链路流程页从下往上渲染（时序自下而上 ⇒ 最新一定在最上）+ 容器高度自动拓高；② 主动思考页保持原渲染方式但最新放最左（容器默认露最左）；③ 追加：改布局后多路渲染仍要合适。

- 共享布局唯一入口 flow/layout.ts：新增枚举 FlowOrientation(newest-top|newest-left) + layoutFlow(graph, orientation)；排布拆成「抽象网格→像素」两步，方向开关只在 toPixelNode/toPixelBand；泳道成道逻辑零改动
- 边几何抽到新文件 flow/edges.ts：只按方向选锚点，带回 fromId/toId（不重排图数据），悬空边如实丢弃
- FlowGraphView 的 orientation 是**必填** prop（漏传=编译错误）；画布不限高、无 overflow-y（不内部裁切，纵向随图生长）；图例加方向小字
- 三处调用同一套布局：Flow=newest-top、Backthink=newest-left、Agents=newest-left（后者是我按同一档裁定，一行可改）
- 顺带修复：画布最大列现在把「刚开出、还没跑出步骤的泳道」最小宽度算进去（否则泳道框被裁到画布外）
- 测试 593 checks（orientation 逻辑 131 + 渲染 338 + lanes 40 + 既有回归）；变异 7 条全红，含「边端点连到错节点」「容器限高裁切」「空泳道被裁」
- 多路：lanes.test 期望随新方向镜像更新，泳道仍成道；并行路数据互相覆盖的已知问题归后续分桶切片

frontend/web/src/admin/modules/Agents.tsx

@@ -172,7 +172,9 @@ export function AgentsFlowBlock({
   }
   return (
     <Surface gap="sm">
-      <FlowGraphView graph={graph} />
+      {/* 与后台思考的图块同一档：横向渲染 + 最新在最左（FV0），
+          容器默认露出最左边 ⇒ 打开就先看到最新那拍。 */}
+      <FlowGraphView graph={graph} orientation="newest-left" />
       <FlowSnapshotHint sessionId={graph.sessionId ?? sessionId} source={source ?? "live"} />
     </Surface>
   );

frontend/web/src/admin/modules/Backthink.tsx

@@ -115,7 +115,9 @@ export function BackthinkGraphBlock({
   }
   return (
     <>
-      <FlowGraphView graph={graph} />
+      {/* 页面区域有限、容器默认只露出最左边 ⇒ 保持横向渲染，但把最新放在最左
+          （FV0；时序自右向左，箭头随之指向左边）。 */}
+      <FlowGraphView graph={graph} orientation="newest-left" />
       <FlowSnapshotHint sessionId={sessionId} source={source ?? "live"} />
     </>
   );

frontend/web/src/admin/modules/Flow.tsx

@@ -146,6 +146,7 @@ export function FlowBody({
             <StatusStrip graph={shown} />
             <FlowGraphView
               graph={shown}
+              orientation="newest-top"
               selectedId={selectedId}
               onNodeClick={(n) => setSelectedId(n.id)}
             />

frontend/web/src/admin/modules/FlowGraph.tsx

@@ -6,34 +6,53 @@ import {
   STATUS_ORDER,
   statusOf,
 } from "./flow/tone";
-import { layoutFlow, NODE_W, NODE_H, type PlacedBand, type PlacedEdge, type PlacedNode } from "./flow/layout";
+import { layoutFlow, NODE_W, NODE_H, type FlowOrientation, type PlacedBand } from "./flow/layout";
+import { edgeShapes, type EdgeShape } from "./flow/edges";
 
 /** Lightweight SVG directed-graph renderer for a FlowGraph (no graph deps).
- *  Left-to-right layered layout: a node's column is its longest-path depth from
+ *  A node's step is its longest-path depth from a root; the steps advance along the
- *  a root, and the rows of one column stack top-down. Sub-agent branches are
+ *  **time axis** and the newest one always sits at the canvas origin (top or left, see
- *  drawn in their own framed lanes below the trunk (design/19 §2), so parallel
+ *  `FlowOrientation` in flow/layout.ts). Sub-agent branches are drawn in their own framed
- *  branches read as separate swimlanes instead of interleaving. Edges are cubic
+ *  lanes beside the trunk (design/19 §2), so parallel branches read as separate swimlanes
- *  beziers with an arrowhead; node stroke/fill is coded by status and a running
+ *  instead of interleaving. Edges are cubic beziers with an arrowhead anchored on the
- *  node pulses with the panel's existing `.mu-blink` (no new animation dep). */
+ *  border the direction dictates (flow/edges.ts); node stroke/fill is coded by status and
+ *  a running node pulses with the panel's existing `.mu-blink` (no new animation dep).
+ *
+ *  容器**不限高**：图多高就多高（主人要求「容器高度自动拓高」，不在内部裁切）；横向仅在
+ *  泳道把画布撑宽时滚动（`newest-top` 下就是这种情形），纵向永远随图生长。 */
+
+/** 方向提示（画在图例里）：让「哪端是最新」写在脸上，不靠用户自己猜。 */
+const DIRECTION_HINT: Record<FlowOrientation, string> = {
+  "newest-top": "时序自下而上 ↑ · 最新在最上",
+  "newest-left": "时序自右向左 ← · 最新在最左",
+};
 
 export function FlowGraphView({
   graph,
+  orientation,
   onNodeClick,
   selectedId,
 }: {
   graph: FlowGraph;
+  /** 渲染方向（flow/layout.ts）：`newest-top` = 时序自下而上（整页 Flow）；
+   *  `newest-left` = 时序自右向左（嵌在页面里的图块，容器默认露出最左边）。 */
+  orientation: FlowOrientation;
   onNodeClick?: (node: FlowNode) => void;
   selectedId?: string | null;
 }): ReactNode {
   const markerId = useId().replace(/[^a-zA-Z0-9]/g, "");
   const laneMarkerId = `${markerId}L`;
-  const { nodes, edges, bands, lanes, width, height } = layoutFlow(graph);
+  const layout = layoutFlow(graph, orientation);
-  const placedOf = new Map(nodes.map((p) => [p.node.id, p]));
+  const { nodes, bands, lanes, width, height } = layout;
+  const shapes = edgeShapes(layout);
   const laneRoots = new Set(lanes.map((l) => l.id));
 
   return (
     <div className="space-y-2">
-      <div className="overflow-x-auto rounded-[var(--mu-radius)] border border-[var(--mu-glass-border)] bg-[var(--mu-surface-2)] p-3">
+      <div
+        data-flow-canvas="1"
+        className="overflow-x-auto rounded-[var(--mu-radius)] border border-[var(--mu-glass-border)] bg-[var(--mu-surface-2)] p-3"
+      >
         <svg width={width} height={height} viewBox={`0 0 ${width} ${height}`} className="block">
           <defs>
             <marker
@@ -64,12 +83,10 @@ export function FlowGraphView({
             <LaneFrame key={band.id} band={band} />
           ))}
 
-          {edges.map((e, i) => (
+          {shapes.map((shape, i) => (
             <EdgePath
-              key={`${e.edge.from}-${e.edge.to}-${i}`}
+              key={`${shape.fromId}-${shape.toId}-${i}`}
-              edge={e}
+              shape={shape}
-              from={placedOf.get(e.edge.from)}
-              to={placedOf.get(e.edge.to)}
               markerId={markerId}
               laneMarkerId={laneMarkerId}
             />
@@ -88,42 +105,32 @@ export function FlowGraphView({
           ))}
         </svg>
       </div>
-      <Legend hasLanes={lanes.length > 0} />
+      <Legend hasLanes={lanes.length > 0} orientation={orientation} />
     </div>
   );
 }
 
-/** EdgePath draws one cubic bezier between two placed nodes; edges that run into
+/** EdgePath draws one cubic bezier between the two placed nodes; edges that run into
- *  a lane are dashed and accent-colored so the trunk stays readable. */
+ *  a lane are dashed and accent-colored so the trunk stays readable. The endpoints come
+ *  from `edgeShapes` — the component never recomputes (nor guesses) them. */
 function EdgePath({
-  edge,
+  shape,
-  from,
-  to,
   markerId,
   laneMarkerId,
 }: {
-  edge: PlacedEdge;
+  shape: EdgeShape;
-  from?: PlacedNode;
-  to?: PlacedNode;
   markerId: string;
   laneMarkerId: string;
 }): ReactNode {
-  if (!from || !to) return null;
-  const sx = from.x + NODE_W;
-  const sy = from.y + NODE_H / 2;
-  const tx = to.x;
-  const ty = to.y + NODE_H / 2;
-  const dx = Math.max(24, Math.abs(tx - sx) / 2);
-  const inLane = edge.lane !== undefined;
   return (
     <path
-      d={`M ${sx} ${sy} C ${sx + dx} ${sy}, ${tx - dx} ${ty}, ${tx} ${ty}`}
+      d={shape.d}
       fill="none"
-      stroke={inLane ? "var(--mu-accent)" : "var(--mu-text-lo)"}
+      stroke={shape.inLane ? "var(--mu-accent)" : "var(--mu-text-lo)"}
-      strokeOpacity={inLane ? 0.7 : 1}
+      strokeOpacity={shape.inLane ? 0.7 : 1}
       strokeWidth="1.5"
-      strokeDasharray={inLane ? "5 3" : undefined}
+      strokeDasharray={shape.inLane ? "5 3" : undefined}
-      markerEnd={`url(#${inLane ? laneMarkerId : markerId})`}
+      markerEnd={`url(#${shape.inLane ? laneMarkerId : markerId})`}
     />
   );
 }
@@ -245,8 +252,15 @@ function NodeGroup({
   );
 }
 
-/** Legend explains the status colors and the lane edge style. */
+/** Legend explains the status colors, the lane edge style, and which end of the time
-function Legend({ hasLanes }: { hasLanes: boolean }): ReactNode {
+ *  axis is the newest one (the direction is reversed for the whole-page view). */
+function Legend({
+  hasLanes,
+  orientation,
+}: {
+  hasLanes: boolean;
+  orientation: FlowOrientation;
+}): ReactNode {
   return (
     <div className="flex flex-wrap items-center gap-3 px-1">
       {STATUS_ORDER.map((s) => (
@@ -274,6 +288,9 @@ function Legend({ hasLanes }: { hasLanes: boolean }): ReactNode {
           泳道内步骤
         </span>
       ) : null}
+      <span className="inline-flex items-center gap-1.5 text-[10px] text-[var(--mu-text-lo)]">
+        {DIRECTION_HINT[orientation]}
+      </span>
     </div>
   );
 }

frontend/web/src/admin/modules/flow/edges.ts

@@ -0,0 +1,70 @@
+import { NODE_H, NODE_W, type FlowLayout, type FlowOrientation, type PlacedNode } from "./layout";
+
+/** 一条边的像素几何（FV0）：锚点贴在**节点边框**上，方向由布局方向决定 ——
+ *  最新在上 ⇒ 从更早那拍的上边出去、从更新那拍的下边进来；最新在左 ⇒ 左出右进。
+ *  `fromId` / `toId` 原样带回图数据的 id，便于逐边核对「这条线确实连在正确的两个节点之间」。 */
+export interface EdgeShape {
+  /** 图数据里的起点 id（绝不改写、绝不重排）。 */
+  fromId: string;
+  /** 图数据里的终点 id（时序上更新的那一端）。 */
+  toId: string;
+  /** 该边所属泳道（undefined = 主干）。 */
+  lane?: string;
+  sx: number;
+  sy: number;
+  tx: number;
+  ty: number;
+  /** SVG path 的 d 属性。 */
+  d: string;
+  inLane: boolean;
+}
+
+/** edgeShapes resolves every placed edge into a pixel path. 端点缺一的边整条丢弃
+ *  （如实丢，不伪造节点）—— layout 已先按「两个端点都在图里」过滤过，这里是第二道闸。 */
+export function edgeShapes(layout: FlowLayout): EdgeShape[] {
+  const placedOf = new Map(layout.nodes.map((p) => [p.node.id, p]));
+  const shapes: EdgeShape[] = [];
+  layout.edges.forEach((e) => {
+    const from = placedOf.get(e.edge.from);
+    const to = placedOf.get(e.edge.to);
+    if (!from || !to) return;
+    const a = anchors(from, to, layout.orientation);
+    shapes.push({
+      fromId: e.edge.from,
+      toId: e.edge.to,
+      lane: e.lane,
+      sx: a.sx,
+      sy: a.sy,
+      tx: a.tx,
+      ty: a.ty,
+      d: a.d,
+      inLane: e.lane !== undefined,
+    });
+  });
+  return shapes;
+}
+
+/** anchors picks the border anchor of both nodes plus the cubic control points, so the
+ *  arrowhead always points along the time axis of the current orientation. */
+function anchors(
+  from: PlacedNode,
+  to: PlacedNode,
+  orientation: FlowOrientation,
+): { sx: number; sy: number; tx: number; ty: number; d: string } {
+  if (orientation === "newest-top") {
+    // 时序自下而上：从更早那拍的上边出发，进更新那拍的下边。
+    const sx = from.x + NODE_W / 2;
+    const sy = from.y;
+    const tx = to.x + NODE_W / 2;
+    const ty = to.y + NODE_H;
+    const dy = Math.max(24, Math.abs(sy - ty) / 2);
+    return { sx, sy, tx, ty, d: `M ${sx} ${sy} C ${sx} ${sy - dy}, ${tx} ${ty + dy}, ${tx} ${ty}` };
+  }
+  // 时序自右向左：从更早那拍的左边出发，进更新那拍的右边。
+  const sx = from.x;
+  const sy = from.y + NODE_H / 2;
+  const tx = to.x + NODE_W;
+  const ty = to.y + NODE_H / 2;
+  const dx = Math.max(24, Math.abs(sx - tx) / 2);
+  return { sx, sy, tx, ty, d: `M ${sx} ${sy} C ${sx - dx} ${sy}, ${tx + dx} ${ty}, ${tx} ${ty}` };
+}

frontend/web/src/admin/modules/flow/lanes.test.ts

@@ -87,7 +87,7 @@ function parallel(): FlowGraph {
   );
 }
 
-// --- trunk only: no lane, columns unchanged (no P1 regression) ---------------
+// --- trunk only: no lane, one column grid (no P1 regression) ----------------
 
 {
   const g = trunkOnly();
@@ -99,29 +99,29 @@ function parallel(): FlowGraph {
   const at = new Map(nodes.map((p) => [p.node.id, p]));
   same(bands.length, 1, "trunk graph has exactly one band");
   same(bands[0].framed, false, "the trunk band is not framed");
-  same(at.get("input")!.x, PAD, "input sits in the first column");
+  // FV0：默认方向 newest-left ⇒ 时序自右向左，最新的一拍（output）落在最左。
+  same(at.get("output")!.x, PAD, "the newest step sits leftmost");
   ok(
-    at.get("output")!.x > at.get("tool1")!.x &&
+    at.get("input")!.x > at.get("llm1")!.x &&
-      at.get("tool1")!.x > at.get("llm1")!.x &&
+      at.get("llm1")!.x > at.get("tool1")!.x &&
-      at.get("llm1")!.x > at.get("input")!.x,
+      at.get("tool1")!.x > at.get("output")!.x,
-    "trunk columns grow left to right",
+    "the time axis runs right to left (newest on the left)",
   );
   same(
     [at.get("input")!.y, at.get("llm1")!.y, at.get("tool1")!.y, at.get("output")!.y],
     [PAD, PAD, PAD, PAD],
     "a single-row trunk keeps one row",
   );
-  // P1 pixel parity: with no lane in play the geometry is exactly the old
+  // 同一块最长路径列网格的**镜像**：方向只决定「哪端是最新」，列距/行距分毫不动。
-  // longest-path column grid, so P2 cannot regress the trunk view.
   same(
     nodes.map((p) => [p.node.id, p.x, p.y]),
     [
-      ["input", PAD, PAD],
+      ["input", PAD + 3 * (NODE_W + GAP_X), PAD],
-      ["llm1", PAD + (NODE_W + GAP_X), PAD],
+      ["llm1", PAD + 2 * (NODE_W + GAP_X), PAD],
-      ["tool1", PAD + 2 * (NODE_W + GAP_X), PAD],
+      ["tool1", PAD + (NODE_W + GAP_X), PAD],
-      ["output", PAD + 3 * (NODE_W + GAP_X), PAD],
+      ["output", PAD, PAD],
     ],
-    "trunk-only layout matches the P1 column grid",
+    "trunk-only layout is the same column grid, mirrored (newest-left)",
   );
 }
 
@@ -187,21 +187,22 @@ function parallel(): FlowGraph {
   const framed = bands.filter((b) => b.framed);
   same(framed.length, 2, "each lane gets its own framed band");
 
-  // Lane steps start one column right of their sub-agent root.
+  // Lane steps start one column to the *newer* side of their sub-agent root — in
+  // newest-left that side is the left one (smaller x).
   same(
-    at.get("llmA")!.x - at.get("subA")!.x,
+    at.get("subA")!.x - at.get("llmA")!.x,
     NODE_W + GAP_X,
-    "lane A's first step starts one column right of its root",
+    "lane A's first step starts one column left (newer) of its root",
   );
   same(
-    at.get("toolA")!.x,
+    at.get("llmA")!.x,
-    at.get("llmA")!.x + NODE_W + GAP_X,
+    at.get("toolA")!.x + NODE_W + GAP_X,
-    "lane A chains toolA after llmA",
+    "lane A chains toolA after llmA (toolA is newer ⇒ further left)",
   );
   same(
-    at.get("llmB")!.x - at.get("subB")!.x,
+    at.get("subB")!.x - at.get("llmB")!.x,
     NODE_W + GAP_X,
-    "lane B's step starts one column right of its root",
+    "lane B's step starts one column left (newer) of its root",
   );
 
   // Lanes are stacked below the trunk and never share rows with each other.

frontend/web/src/admin/modules/flow/layout.ts

@@ -1,18 +1,24 @@
 import type { AgentStatus, FlowEdge, FlowGraph, FlowNode } from "../../../lib/types";
 import { groupFlowLanes, type FlowGrouping, type FlowLane } from "./lanes";
 
-/** Lane-aware left-to-right layout for the flow graph (design/19 §2). The trunk
+/** 渲染方向（FV0）：时序沿哪条轴、朝哪边推进 —— 「最新的一拍」永远落在画布坐标**最小**的一侧，
- *  keeps the P1 "longest path depth" columns; every sub-agent lane gets its own
+ *  于是容器默认露出的那一角就是最新的时刻。
- *  horizontal band below the trunk, its steps starting one column right of the
+ *  - `newest-top`：时序**自下而上**，泳道沿垂直方向（向右）并排 —— 整页 Flow 用；
- *  sub-agent root and chaining rightwards. Bands never share rows, so parallel
+ *    画布纵向自动拓高（向下滚动看历史，向上看最新）。
- *  branches cannot overlap — the canvas just grows (and scrolls) instead. */
+ *  - `newest-left`：时序**自右向左**，泳道向下叠加 —— 嵌在页面里的图块（Backthink / Agents）
+ *    用；横向滚动容器的可视区默认露出最左边，因此最新在最左。
+ *
+ *  两种方向**共用同一套排布**：先按「时序轴（step）× 堆叠轴（stack）」算抽象网格，
+ *  再由 `toPixelNode` / `toPixelBand` 一次性映射成像素（`newest-top` 把两轴对调）。
+ *  方向只影响这一处映射与边的锚点（见 flow/edges.ts），**不复制第二套布局**。 */
+export type FlowOrientation = "newest-top" | "newest-left";
 
 export const NODE_W = 148;
 export const NODE_H = 52;
 export const GAP_X = 64;
 export const GAP_Y = 30;
 export const PAD = 20;
-/** Vertical gap between two bands. */
+/** Gap between two bands, along the stack axis. */
 export const BAND_GAP = 26;
 /** Padding between a lane frame and the nodes it holds. */
 export const FRAME_PAD = 10;
@@ -51,8 +57,11 @@ export interface FlowLayout {
   edges: PlacedEdge[];
   bands: PlacedBand[];
   lanes: FlowLane[];
+  /** 画布像素尺寸：`newest-left` 是「宽 × 高」，`newest-top` 是同一块网格转置后的「宽 × 高」。 */
   width: number;
   height: number;
+  /** 本次布局用的方向（边的锚点由渲染层按它决定，回传以避免两处口径不一致）。 */
+  orientation: FlowOrientation;
 }
 
 interface BandPlan {
@@ -68,22 +77,89 @@ interface BandPlan {
   toCol: number;
 }
 
-/** layoutFlow computes the lane-banded geometry of a graph. */
+/** 轴度量：时序轴（step）与堆叠轴（stack）各用哪套尺寸/间隙。
-export function layoutFlow(graph: FlowGraph): FlowLayout {
+ *  `newest-top` 把两轴对调 ⇒ 节点在时序轴上占的是**高度**，在堆叠轴上占的是**宽度**。 */
+interface AxisMetric {
+  stepLen: number;
+  stepGap: number;
+  stackLen: number;
+  stackGap: number;
+}
+
+/** 抽象网格坐标（尚未决定横竖），像素化在 toPixelNode / toPixelBand 里做。 */
+interface GridNode {
+  node: FlowNode;
+  step: number;
+  stack: number;
+}
+
+interface GridBox {
+  id?: string;
+  label: string;
+  status: AgentStatus;
+  stepStart: number;
+  stepSize: number;
+  stackStart: number;
+  stackSize: number;
+  framed: boolean;
+}
+
+interface FlowGrid {
+  nodes: GridNode[];
+  boxes: GridBox[];
+  stackExtent: number;
+}
+
+/** layoutFlow computes the lane-banded geometry of a graph in the given direction.
+ *  默认 `newest-left`：嵌在页面里的图块（Backthink / Agents）用横向、最新在左；
+ *  整页 Flow 显式传 `newest-top`（时序自下而上、容器纵向自动拓高）。 */
+export function layoutFlow(
+  graph: FlowGraph,
+  orientation: FlowOrientation = "newest-left",
+): FlowLayout {
   const grouping = groupFlowLanes(graph);
   if (grouping.byId.size === 0) {
-    return { nodes: [], edges: [], bands: [], lanes: [], width: PAD * 2, height: PAD * 2 };
+    return { nodes: [], edges: [], bands: [], lanes: [], width: PAD * 2, height: PAD * 2, orientation };
   }
 
+  const metric = axisMetric(orientation);
   const index = orderIndex(grouping.nodes);
   const plans = planBands(grouping);
-  const { nodes, bands, width, height } = placeBands(plans, index);
+  const maxCol = canvasMaxCol(plans);
+  const grid = buildGrid(plans, index, metric, maxCol);
+  const nodes = grid.nodes.map((n) => toPixelNode(n, orientation));
+  const bands = grid.boxes.map((b) => toPixelBand(b, orientation));
   const placed = new Set(nodes.map((p) => p.node.id));
   const edges: PlacedEdge[] = grouping.edges
     .filter((e) => placed.has(e.from) && placed.has(e.to))
     .map((edge) => ({ edge, lane: grouping.bandOf.get(edge.to) }));
 
-  return { nodes, edges, bands, lanes: grouping.lanes, width, height };
+  const stepExtent = axisExtent(maxCol, metric.stepLen, metric.stepGap);
+  const size =
+    orientation === "newest-top"
+      ? { width: grid.stackExtent, height: stepExtent }
+      : { width: stepExtent, height: grid.stackExtent };
+
+  return { nodes, edges, bands, lanes: grouping.lanes, ...size, orientation };
+}
+
+/** axisMetric picks which pixel size / gap each axis uses for the direction. */
+function axisMetric(orientation: FlowOrientation): AxisMetric {
+  return orientation === "newest-top"
+    ? { stepLen: NODE_H, stepGap: GAP_Y, stackLen: NODE_W, stackGap: GAP_X }
+    : { stepLen: NODE_W, stepGap: GAP_X, stackLen: NODE_H, stackGap: GAP_Y };
+}
+
+/** axisExtent is the total pixel length of one axis (PAD on both ends). */
+function axisExtent(maxCol: number, len: number, gap: number): number {
+  return PAD * 2 + (maxCol + 1) * len + maxCol * gap;
+}
+
+/** canvasMaxCol is the last column the canvas must cover: the widest band, including the
+ *  minimum span of an idle lane — otherwise a lane frame that just opened (no step yet)
+ *  would be drawn outside the canvas and clipped. */
+function canvasMaxCol(plans: BandPlan[]): number {
+  return plans.reduce((max, p) => Math.max(max, p.toCol), 0);
 }
 
 /** orderIndex maps every node id to its graph-order position. */
@@ -138,25 +214,25 @@ function planBands(grouping: FlowGrouping): BandPlan[] {
   return plans;
 }
 
-/** placeBands turns the plans into pixel geometry: bands stack top-down (lanes
+/** buildGrid lays the planned bands onto the abstract step × stack grid: bands are
- *  framed, with a header row for their label) and every node gets its own slot. */
+ *  placed one after another along the stack axis (lane frames carry a label row), and
-function placeBands(
+ *  the siblings of one step occupy successive slots along that same axis. */
+function buildGrid(
   plans: BandPlan[],
   index: Map<string, number>,
-): { nodes: PlacedNode[]; bands: PlacedBand[]; width: number; height: number } {
+  metric: AxisMetric,
-  const pos = new Map<string, PlacedNode>();
+  maxCol: number,
-  const bands: PlacedBand[] = [];
+): FlowGrid {
-  /** Top of the next band (its frame top, header included). */
+  const nodes: GridNode[] = [];
-  let limitY = PAD;
+  const boxes: GridBox[] = [];
-  let contentBottom = PAD;
+  const stepPitch = metric.stepLen + metric.stepGap;
-  let maxCol = 0;
+  const stackPitch = metric.stackLen + metric.stackGap;
+  let stackCursor = PAD;
 
   plans.forEach((plan) => {
     const framed = plan.id !== undefined;
-    const frameY = limitY;
+    const stackSize = bandStackSize(plan.rows, metric, framed);
-    const contentY = framed ? frameY + LANE_HEADER + FRAME_PAD : frameY;
+    const contentStack = stackCursor + (framed ? LANE_HEADER + FRAME_PAD : 0);
-    const bandHeight = rowsHeight(plan.rows);
-    const frameHeight = framed ? bandHeight + LANE_HEADER + FRAME_PAD * 2 : bandHeight;
 
     const byCol = new Map<number, FlowNode[]>();
     plan.members.forEach((n) => {
@@ -164,41 +240,64 @@ function placeBands(
       const arr = byCol.get(col) ?? [];
       arr.push(n);
       byCol.set(col, arr);
-      maxCol = Math.max(maxCol, col);
     });
     byCol.forEach((arr, col) => {
       arr
         .sort((a, b) => index.get(a.id)! - index.get(b.id)!)
         .forEach((n, row) => {
-          pos.set(n.id, {
+          nodes.push({
             node: n,
-            x: PAD + col * (NODE_W + GAP_X),
+            step: stepPos(col, maxCol, stepPitch),
-            y: contentY + row * (NODE_H + GAP_Y),
+            stack: contentStack + row * stackPitch,
           });
         });
     });
 
-    bands.push({
+    boxes.push({
       id: plan.id,
       label: plan.lane ? plan.lane.root.label : "主干",
       status: plan.lane ? plan.lane.status : "idle",
-      x: PAD + plan.fromCol * (NODE_W + GAP_X) - (framed ? FRAME_PAD : 0),
+      stepStart: stepPos(plan.toCol, maxCol, stepPitch) - (framed ? FRAME_PAD : 0),
-      y: frameY,
+      stepSize: (plan.toCol - plan.fromCol) * stepPitch + metric.stepLen + (framed ? FRAME_PAD * 2 : 0),
-      width: (plan.toCol - plan.fromCol + 1) * (NODE_W + GAP_X) - GAP_X + (framed ? FRAME_PAD * 2 : 0),
+      stackStart: stackCursor,
-      height: frameHeight,
+      stackSize,
       framed,
     });
 
-    contentBottom = frameY + frameHeight;
+    stackCursor += stackSize + BAND_GAP;
-    limitY = contentBottom + BAND_GAP;
   });
 
-  return {
+  nodes.sort((a, b) => index.get(a.node.id)! - index.get(b.node.id)!);
-    nodes: [...pos.values()].sort((a, b) => index.get(a.node.id)! - index.get(b.node.id)!),
+  return { nodes, boxes, stackExtent: stackCursor - BAND_GAP + PAD };
-    bands,
+}
-    width: PAD * 2 + (maxCol + 1) * NODE_W + maxCol * GAP_X,
+
-    height: Math.max(contentBottom + PAD, PAD * 2),
+/** stepPos projects a step (column) onto the step axis: the bigger the column, the newer
-  };
+ *  the moment, the **smaller** the coordinate — newest ends up at the top / on the left. */
+function stepPos(col: number, maxCol: number, stepPitch: number): number {
+  return PAD + (maxCol - col) * stepPitch;
+}
+
+/** bandStackSize is the size a band takes on the stack axis (a lane frame also carries
+ *  its label row and the inner padding). */
+function bandStackSize(rows: number, metric: AxisMetric, framed: boolean): number {
+  const content = rows * metric.stackLen + (rows - 1) * metric.stackGap;
+  return framed ? content + LANE_HEADER + FRAME_PAD * 2 : content;
+}
+
+/** toPixelNode is the only direction switch for nodes: `newest-top` swaps both axes. */
+function toPixelNode(grid: GridNode, orientation: FlowOrientation): PlacedNode {
+  return orientation === "newest-top"
+    ? { node: grid.node, x: grid.stack, y: grid.step }
+    : { node: grid.node, x: grid.step, y: grid.stack };
+}
+
+/** toPixelBand is the same direction switch for band frames. */
+function toPixelBand(box: GridBox, orientation: FlowOrientation): PlacedBand {
+  const rect =
+    orientation === "newest-top"
+      ? { x: box.stackStart, y: box.stepStart, width: box.stackSize, height: box.stepSize }
+      : { x: box.stepStart, y: box.stackStart, width: box.stepSize, height: box.stackSize };
+  return { id: box.id, label: box.label, status: box.status, framed: box.framed, ...rect };
 }
 
 /** computeBandColumns fills a band's per-node depth (longest path inside the
@@ -235,8 +334,3 @@ function computeBandColumns(plan: BandPlan, edges: FlowEdge[]): void {
   });
   plan.rows = perCol.size > 0 ? Math.max(...perCol.values()) : 1;
 }
-
-/** rowsHeight is the pixel height of rows stacked node cards. */
-function rowsHeight(rows: number): number {
-  return rows * NODE_H + (rows - 1) * GAP_Y;
-}

frontend/web/src/admin/modules/flow/orientation.render.test.ts

@@ -0,0 +1,332 @@
+// 方向（FV0）的**真实渲染**测试：主人报的是「看得见」的体验（最新的必须在最上 / 最左、
+// 容器高度要跟着图长），所以这里不信逻辑返回值 —— 直接从 SSR 出来的 SVG 里把**节点矩形**
+// 与**边路径**解析出来，核对：
+//  ① Flow 页（整页）最新的一拍在**最上**（时序自下而上）；
+//  ② 主动思考 / Agents 的图块保持横向渲染，但最新的一拍在**最左**；
+//  ③ 每条边都连在**正确的两个节点**之间（端点贴在正确节点的正确边框中点，箭头指向更新的那端）；
+//  ④ 画布高度随图生长、容器不限高（不内部裁切）。
+//
+// 本项目没有 jsdom ⇒ 用 react-dom/server 渲染 **props 驱动**的组件（同
+// flowSnapshot.render.test.ts 头注释的理由）。
+//
+// 跑法：
+//
+//   cd frontend/web \
+//     && ./node_modules/.bin/esbuild src/admin/modules/flow/orientation.render.test.ts \
+//          --bundle --platform=node --format=cjs \
+//          --outfile=/tmp/cyrene-flow-orientation-model.test.cjs \
+//     && node /tmp/cyrene-flow-orientation-model.test.cjs
+//
+// `tsc --noEmit` 会对本文件做类型检查，因此它只从项目内导入、不 import node:*。
+
+import { createElement } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+import type { FlowEdge, FlowGraph, FlowNode } from "../../../lib/types";
+import { BACKTHINK_SESSION_ID, MAIN_SESSION_ID } from "../../../store/sessionCache";
+import { AgentsFlowBlock } from "../Agents";
+import { BackthinkGraphBlock } from "../Backthink";
+import { FlowBody } from "../Flow";
+import { NODE_H, NODE_W, layoutFlow } from "./layout";
+
+let checks = 0;
+
+function ok(cond: boolean, what: string): void {
+  checks += 1;
+  if (!cond) throw new Error(`FAILED: ${what}`);
+}
+
+function has(haystack: string, needle: string): boolean {
+  return haystack.includes(needle);
+}
+
+function node(id: string, label: string, kind: string): FlowNode {
+  return { id, label, kind, status: "done" };
+}
+
+function graph(nodes: FlowNode[], edges: FlowEdge[]): FlowGraph {
+  return { id: "web-fv0", sessionId: MAIN_SESSION_ID, nodes, edges };
+}
+
+/** 「输入 → 思考 → 工具 → 回复」主干；追加一拍用来验证画布继续长高。 */
+function chain(extra = 0): FlowGraph {
+  const nodes = [
+    node("input", "哨兵输入", "input"),
+    node("llm1", "哨兵思考", "llm"),
+    node("tool1", "哨兵工具", "tool"),
+    node("output", "哨兵回复", "output"),
+  ];
+  const edges: FlowEdge[] = [
+    { from: "input", to: "llm1" },
+    { from: "llm1", to: "tool1" },
+    { from: "tool1", to: "output" },
+  ];
+  for (let i = 0; i < extra; i += 1) {
+    const prev = nodes[nodes.length - 1].id;
+    nodes.push(node(`output${i + 2}`, `哨兵追加${i + 1}`, "output"));
+    edges.push({ from: prev, to: `output${i + 2}` });
+  }
+  return graph(nodes, edges);
+}
+
+/** 主干 + 一条并行子代理泳道。 */
+function withLane(): FlowGraph {
+  return graph(
+    [
+      node("input", "哨兵输入", "input"),
+      node("t1", "哨兵工具", "tool"),
+      node("subA", "哨兵子代理", "subagent"),
+      node("llmA", "哨兵子思考", "llm"),
+      node("toolA", "哨兵子工具", "tool"),
+      node("output", "哨兵回复", "output"),
+    ],
+    [
+      { from: "input", to: "t1" },
+      { from: "t1", to: "subA" },
+      { from: "subA", to: "llmA" },
+      { from: "llmA", to: "toolA" },
+      { from: "t1", to: "output" },
+    ],
+  );
+}
+
+/** canvasOf slices out just the graph canvas: the page markup also carries Icon <svg>s
+ *  whose paths would otherwise be mistaken for graph edges. */
+function canvasOf(markup: string): string {
+  const start = markup.indexOf("data-flow-canvas");
+  ok(start >= 0, "必须渲染出图布容器");
+  const end = markup.indexOf("</svg>", start);
+  ok(end > start, "画布必须含 svg");
+  return markup.slice(start, end);
+}
+
+/** rectOf reads the坐标 of the card of the node whose label is `label`
+ *  (the title line precedes the card rect in the markup). */
+function rectOf(markup: string, label: string): { x: number; y: number } {
+  const canvas = canvasOf(markup);
+  const anchor = canvas.indexOf(`<title>${label} · `);
+  ok(anchor >= 0, `节点 ${label} 必须被画出来`);
+  const m = /<rect x="(-?[\d.]+)" y="(-?[\d.]+)"/.exec(canvas.slice(anchor));
+  ok(m !== null, `节点 ${label} 必须有坐标`);
+  return { x: Number(m![1]), y: Number(m![2]) };
+}
+
+/** edgePaths returns the rendered cubic edge paths, in draw order (marker shapes
+ *  use a straight "L" path and are therefore skipped). */
+function edgePaths(markup: string): string[] {
+  const canvas = canvasOf(markup);
+  const out: string[] = [];
+  const re = /d="(M -?[\d.]+ -?[\d.]+ C [^"]+)"/g;
+  let m = re.exec(canvas);
+  while (m !== null) {
+    out.push(m[1]);
+    m = re.exec(canvas);
+  }
+  return out;
+}
+
+/** curve parses a cubic path into anchors + control points. */
+function curve(d: string): {
+  sx: number;
+  sy: number;
+  c1x: number;
+  c1y: number;
+  c2x: number;
+  c2y: number;
+  tx: number;
+  ty: number;
+} {
+  const [head, rest] = d.replace("M ", "").split(" C ");
+  const [sx, sy] = head.split(" ").map(Number);
+  const [c1, c2, tail] = rest.split(", ");
+  const [c1x, c1y] = c1.split(" ").map(Number);
+  const [c2x, c2y] = c2.split(" ").map(Number);
+  const [tx, ty] = tail.split(" ").map(Number);
+  return { sx, sy, c1x, c1y, c2x, c2y, tx, ty };
+}
+
+/** tagAt returns the whole opening tag that carries `needle` (for class inspection). */
+function tagAt(markup: string, needle: string): string {
+  const at = markup.indexOf(needle);
+  ok(at >= 0, `必须存在带 ${needle} 的容器`);
+  const start = markup.lastIndexOf("<", at);
+  const end = markup.indexOf(">", at);
+  return markup.slice(start, end + 1);
+}
+
+/** svgSize reads the rendered canvas size (of the graph canvas, not an Icon). */
+function svgSize(markup: string): { width: number; height: number } {
+  const m = /<svg width="(-?[\d.]+)" height="(-?[\d.]+)"/.exec(canvasOf(markup));
+  ok(m !== null, "必须画出 svg 画布");
+  return { width: Number(m![1]), height: Number(m![2]) };
+}
+
+/** checkContainer asserts the canvas grows with the graph and never clips vertically. */
+function checkContainer(markup: string, orientation: "newest-top" | "newest-left", what: string): void {
+  const tag = tagAt(markup, "data-flow-canvas");
+  ok(has(tag, "overflow-x-auto"), `${what}：画布只在横向需要时滚动`);
+  ok(!has(tag, "max-h") && !has(tag, "overflow-hidden"), `${what}：容器不得限高/裁切`);
+  ok(!has(tag, "overflow-y"), `${what}：容器纵向随图生长（不内部滚动截断）`);
+  ok(tag.indexOf("<svg") < 0, `${what}：画布容器是外层 div，不把限高带进 svg`);
+  void orientation;
+}
+
+/** checkEdges asserts每一条边都画在正确的两个节点之间（逐边核对端点 id 对应的矩形）。 */
+function checkEdges(
+  markup: string,
+  g: FlowGraph,
+  orientation: "newest-top" | "newest-left",
+  what: string,
+): void {
+  const paths = edgePaths(markup);
+  ok(
+    paths.length === g.edges.length,
+    `${what}：${g.edges.length} 条边必须全部画出来（实际 ${paths.length}）`,
+  );
+  const labelOf = new Map(g.nodes.map((n) => [n.id, n.label]));
+  g.edges.forEach((e, i) => {
+    const from = rectOf(markup, labelOf.get(e.from)!);
+    const to = rectOf(markup, labelOf.get(e.to)!);
+    const c = curve(paths[i]);
+    if (orientation === "newest-top") {
+      ok(
+        c.sx === from.x + NODE_W / 2 && c.sy === from.y,
+        `${what}：边 ${i}（${e.from}→${e.to}）起点贴在 ${e.from} 的上边中点`,
+      );
+      ok(
+        c.tx === to.x + NODE_W / 2 && c.ty === to.y + NODE_H,
+        `${what}：边 ${i}（${e.from}→${e.to}）终点贴在 ${e.to} 的下边中点`,
+      );
+      ok(c.c1y < c.sy && c.c2y > c.ty, `${what}：边 ${i} 箭头自下而上，指向更新的节点`);
+    } else {
+      ok(
+        c.sx === from.x && c.sy === from.y + NODE_H / 2,
+        `${what}：边 ${i}（${e.from}→${e.to}）起点贴在 ${e.from} 的左边中点`,
+      );
+      ok(
+        c.tx === to.x + NODE_W && c.ty === to.y + NODE_H / 2,
+        `${what}：边 ${i}（${e.from}→${e.to}）终点贴在 ${e.to} 的右边中点`,
+      );
+      ok(c.c1x < c.sx && c.c2x > c.tx, `${what}：边 ${i} 箭头自右向左，指向更新的节点`);
+    }
+  });
+}
+
+// ── ① 全链路流程页：时序自下而上，最新在最上，容器只向高处生长 ────────────────
+
+{
+  const g = chain();
+  const html = renderToStaticMarkup(
+    createElement(FlowBody, { graph: g, sessionId: MAIN_SESSION_ID, source: "live" }),
+  );
+  ok(has(html, "哨兵回复") && has(html, "哨兵输入"), "Flow 页把该轮的节点都画出来");
+
+  const yInput = rectOf(html, "哨兵输入").y;
+  const yLlm = rectOf(html, "哨兵思考").y;
+  const yTool = rectOf(html, "哨兵工具").y;
+  const yOut = rectOf(html, "哨兵回复").y;
+  ok(yOut < yTool && yTool < yLlm && yLlm < yInput, "Flow 页：最新的一拍在最上，旧的在下面");
+  ok(
+    rectOf(html, "哨兵输入").x === rectOf(html, "哨兵回复").x,
+    "Flow 页：时序沿纵向推进（同一拍不横向铺开）",
+  );
+  ok(has(html, "最新在最上"), "Flow 页必须写明「最新在最上」（方向反了要让人看得懂）");
+  ok(has(html, "时序自下而上"), "Flow 页必须写明时序自下而上");
+
+  const size = svgSize(html);
+  const layout = layoutFlow(g, "newest-top");
+  ok(size.height === layout.height, "Flow 页画布高度 = 布局高度（图多高就多高）");
+  ok(size.width === layout.width, "Flow 页画布宽度 = 布局宽度");
+  ok(yOut === layout.nodes.find((n) => n.node.id === "output")!.y, "Flow 页最新节点的 y 就是布局给的上沿");
+  ok(yInput + NODE_H <= size.height, "Flow 页最旧节点的下沿仍在画布内（没有裁掉历史）");
+  checkContainer(html, "newest-top", "Flow 页");
+  checkEdges(html, g, "newest-top", "Flow 页");
+
+  const taller = renderToStaticMarkup(
+    createElement(FlowBody, { graph: chain(1), sessionId: MAIN_SESSION_ID, source: "live" }),
+  );
+  ok(
+    svgSize(taller).height > size.height,
+    "Flow 页：多一拍 ⇒ 容器更高（高度自动拓高，不是固定框内裁切）",
+  );
+}
+
+// ── ② 主动思考页的图块：保持横向渲染，但最新在最左 ───────────────────────────
+
+{
+  const g = chain();
+  const html = renderToStaticMarkup(
+    createElement(BackthinkGraphBlock, {
+      graph: g,
+      sessionId: BACKTHINK_SESSION_ID,
+      source: "snapshot",
+      wsStatus: "connected",
+    }),
+  );
+  const xInput = rectOf(html, "哨兵输入").x;
+  const xLlm = rectOf(html, "哨兵思考").x;
+  const xTool = rectOf(html, "哨兵工具").x;
+  const xOut = rectOf(html, "哨兵回复").x;
+  ok(xOut < xTool && xTool < xLlm && xLlm < xInput, "后台思考图块：最新的一拍在最左，旧的在右边");
+  ok(
+    rectOf(html, "哨兵输入").y === rectOf(html, "哨兵回复").y,
+    "后台思考图块：仍是横向渲染（同一拍同一行），没有改成竖版",
+  );
+  ok(has(html, "最新在最左"), "后台思考图块必须写明「最新在最左」");
+  ok(has(html, "时序自右向左"), "后台思考图块必须写明时序自右向左");
+
+  const layout = layoutFlow(g, "newest-left");
+  ok(rectOf(html, "哨兵回复").x === layout.nodes.find((n) => n.node.id === "output")!.x, "图块最新节点的 x 就是布局给的最左端");
+  checkContainer(html, "newest-left", "后台思考图块");
+  checkEdges(html, g, "newest-left", "后台思考图块");
+
+  // Agents 页的图块同一档（同一套布局代码、同一个方向值）。
+  const agents = renderToStaticMarkup(
+    createElement(AgentsFlowBlock, { graph: g, sessionId: MAIN_SESSION_ID, source: "live" }),
+  );
+  ok(has(agents, "最新在最左"), "Agents 页图块与后台思考图块同一方向（最新在最左）");
+  checkEdges(agents, g, "newest-left", "Agents 页图块");
+}
+
+// ── ③ 有泳道时：方向仍成立、泳道仍成道、边仍连对 ─────────────────────────────
+
+{
+  const g = withLane();
+  const top = renderToStaticMarkup(
+    createElement(FlowBody, { graph: g, sessionId: MAIN_SESSION_ID, source: "live" }),
+  );
+  ok(has(top, "泳道 · 哨兵子代理"), "Flow 页必须把子代理画成独立泳道");
+  const frame = /<rect x="(-?[\d.]+)" y="(-?[\d.]+)" width="([\d.]+)" height="([\d.]+)"[^>]*stroke-dasharray="6 4"/.exec(top);
+  ok(frame !== null, "泳道必须有框");
+  const fx = Number(frame![1]);
+  const fy = Number(frame![2]);
+  const fw = Number(frame![3]);
+  const fh = Number(frame![4]);
+  ["哨兵子思考", "哨兵子工具"].forEach((label) => {
+    const r = rectOf(top, label);
+    ok(
+      r.x >= fx && r.x + NODE_W <= fx + fw && r.y >= fy && r.y + NODE_H <= fy + fh,
+      `Flow 页：${label} 落在自己的泳道框内（方向反转后仍成道）`,
+    );
+  });
+  ok(
+    rectOf(top, "哨兵子思考").y < rectOf(top, "哨兵子代理").y,
+    "Flow 页：泳道内的步骤比泳道根更新（更靠上）",
+  );
+  checkEdges(top, g, "newest-top", "Flow 页（带泳道）");
+
+  const left = renderToStaticMarkup(
+    createElement(BackthinkGraphBlock, {
+      graph: g,
+      sessionId: BACKTHINK_SESSION_ID,
+      source: "live",
+      wsStatus: "connected",
+    }),
+  );
+  ok(
+    rectOf(left, "哨兵子思考").x < rectOf(left, "哨兵子代理").x,
+    "后台思考图块：泳道内的步骤比泳道根更新（更靠左）",
+  );
+  checkEdges(left, g, "newest-left", "后台思考图块（带泳道）");
+}
+
+console.log(`flow orientation render test: ${checks} checks passed`);

frontend/web/src/admin/modules/flow/orientation.test.ts

@@ -0,0 +1,337 @@
+// 方向（FV0）逻辑测试：两种方向**共用同一套布局代码**（flow/layout.ts 的 `FlowOrientation`），
+// 这里钉住四条不能退让的事实：
+//  ① 时序朝向 —— `newest-top` 最新的节点在**最上**，`newest-left` 最新的在**最左**；
+//  ② 画布随图生长且**不裁切** —— 每个节点、每个泳道框都落在画布尺寸内；
+//  ③ 连线正确性 —— 每条边仍连在**正确的两个节点**之间（逐边核对端点 id 与像素锚点），
+//     端点缺一的边如实丢弃、不伪造；
+//  ④ 泳道仍成道 —— 泳道框罩住自己的成员，且落在主干**更新的一侧**。
+//
+// 跑法（同 lanes.test.ts，用 vite 自带的 esbuild，不加依赖）：
+//
+//   cd frontend/web \
+//     && ./node_modules/.bin/esbuild src/admin/modules/flow/orientation.test.ts \
+//          --bundle --platform=node --format=esm \
+//          --outfile=/tmp/cyrene-flow-orientation.test.mjs \
+//     && node /tmp/cyrene-flow-orientation.test.mjs
+//
+// `tsc --noEmit` 会对本文件做类型检查，因此它只从项目内导入、不 import node:*。
+
+import { GAP_X, GAP_Y, NODE_H, NODE_W, PAD, layoutFlow, type FlowLayout } from "./layout";
+import { edgeShapes } from "./edges";
+import type { FlowEdge, FlowGraph, FlowNode } from "../../../lib/types";
+
+let checks = 0;
+
+function ok(cond: boolean, what: string): void {
+  checks += 1;
+  if (!cond) throw new Error(`FAILED: ${what}`);
+}
+
+function same<T>(got: T, want: T, what: string): void {
+  const g = JSON.stringify(got);
+  const w = JSON.stringify(want);
+  ok(g === w, `${what} — got ${g}, want ${w}`);
+}
+
+function node(id: string, kind: string, status?: FlowNode["status"]): FlowNode {
+  return { id, label: `节点-${id}`, kind, status };
+}
+
+function graph(nodes: FlowNode[], edges: FlowEdge[]): FlowGraph {
+  return { id: "web-fv0", nodes, edges, sessionId: "web" };
+}
+
+/** 一条「输入 → 思考 → 工具 → 回复」的主干链（4 拍，无泳道）。 */
+function chain(extra = 0): FlowGraph {
+  const nodes = [
+    node("input", "input", "done"),
+    node("llm1", "llm", "done"),
+    node("tool1", "tool", "done"),
+    node("output", "output", "done"),
+  ];
+  const edges: FlowEdge[] = [
+    { from: "input", to: "llm1" },
+    { from: "llm1", to: "tool1" },
+    { from: "tool1", to: "output" },
+  ];
+  for (let i = 0; i < extra; i += 1) {
+    const prev = nodes[nodes.length - 1].id;
+    const id = `output${i + 2}`;
+    nodes.push(node(id, "output", "done"));
+    edges.push({ from: prev, to: id });
+  }
+  return graph(nodes, edges);
+}
+
+/** 主干 + 一条并行子代理泳道（泳道的每一步都连在泳道根之后）。 */
+function withLane(): FlowGraph {
+  return graph(
+    [
+      node("input", "input", "done"),
+      node("t1", "tool", "done"),
+      node("subA", "subagent", "running"),
+      node("llmA", "llm", "running"),
+      node("toolA", "tool", "done"),
+      node("output", "output", "done"),
+    ],
+    [
+      { from: "input", to: "t1" },
+      { from: "t1", to: "subA" },
+      { from: "subA", to: "llmA" },
+      { from: "llmA", to: "toolA" },
+      { from: "t1", to: "output" },
+    ],
+  );
+}
+
+/** 泳道只开了头、还没有步骤（实时图上很常见）——泳道框不能被画到画布外。 */
+function idleLane(): FlowGraph {
+  return graph(
+    [node("input", "input", "done"), node("subA", "subagent", "running")],
+    [{ from: "input", to: "subA" }],
+  );
+}
+
+function at(layout: FlowLayout): Map<string, { x: number; y: number }> {
+  return new Map(layout.nodes.map((p) => [p.node.id, { x: p.x, y: p.y }]));
+}
+
+/** fits asserts every card / band frame lies inside the canvas (nothing is clipped). */
+function fits(layout: FlowLayout, what: string): void {
+  layout.nodes.forEach((p) => {
+    ok(
+      p.x >= 0 && p.y >= 0 && p.x + NODE_W <= layout.width && p.y + NODE_H <= layout.height,
+      `${what}: 节点 ${p.node.id} 必须整块落在画布内（不裁切）`,
+    );
+  });
+  layout.bands.forEach((b) => {
+    ok(
+      b.x >= 0 && b.y >= 0 && b.x + b.width <= layout.width && b.y + b.height <= layout.height,
+      `${what}: 泳道框 ${b.id ?? "主干"} 必须整块落在画布内（不裁切）`,
+    );
+  });
+}
+
+/** curve parses a cubic path back into its two anchors and two control points. */
+function curve(d: string): {
+  sx: number;
+  sy: number;
+  c1x: number;
+  c1y: number;
+  c2x: number;
+  c2y: number;
+  tx: number;
+  ty: number;
+} {
+  const [head, rest] = d.replace("M ", "").split(" C ");
+  const [sx, sy] = head.split(" ").map(Number);
+  const [c1, c2, tail] = rest.split(", ");
+  const [c1x, c1y] = c1.split(" ").map(Number);
+  const [c2x, c2y] = c2.split(" ").map(Number);
+  const [tx, ty] = tail.split(" ").map(Number);
+  return { sx, sy, c1x, c1y, c2x, c2y, tx, ty };
+}
+
+// ── ① 时序方向：newest-top 最新在上；newest-left 最新在左 ──────────────────────
+
+{
+  const g = chain();
+  const top = layoutFlow(g, "newest-top");
+  const left = layoutFlow(g, "newest-left");
+  same(top.orientation, "newest-top", "newest-top 布局回传自己的方向");
+  same(left.orientation, "newest-left", "newest-left 布局回传自己的方向");
+
+  // 两种方向画的是同一张图：节点集合/数量/顺序分毫不差（不丢节点、不造节点）。
+  same(
+    top.nodes.map((p) => p.node.id),
+    left.nodes.map((p) => p.node.id),
+    "方向不改变节点集合与顺序",
+  );
+  same(top.nodes.length, g.nodes.length, "方向不丢节点");
+  same(left.bands.length, top.bands.length, "方向不改变泳道/主干的分带");
+
+  const t = at(top);
+  same(
+    [t.get("input")!.y, t.get("llm1")!.y, t.get("tool1")!.y, t.get("output")!.y],
+    [PAD + 3 * (NODE_H + GAP_Y), PAD + 2 * (NODE_H + GAP_Y), PAD + (NODE_H + GAP_Y), PAD],
+    "newest-top：时序自下而上，最新的一拍贴画布上沿",
+  );
+  ok(
+    t.get("input")!.y > t.get("llm1")!.y &&
+      t.get("llm1")!.y > t.get("tool1")!.y &&
+      t.get("tool1")!.y > t.get("output")!.y,
+    "newest-top：越新越靠上（最新一定在最上方）",
+  );
+  same(
+    [t.get("input")!.x, t.get("llm1")!.x, t.get("tool1")!.x, t.get("output")!.x],
+    [PAD, PAD, PAD, PAD],
+    "newest-top：单拍主干占一列（横向不铺开）",
+  );
+  same(
+    [top.width, top.height],
+    [PAD * 2 + NODE_W, PAD * 2 + 4 * NODE_H + 3 * GAP_Y],
+    "newest-top：画布 = 单列宽 × 四拍高（容器纵向自动拓高）",
+  );
+
+  const l = at(left);
+  same(
+    [l.get("input")!.x, l.get("llm1")!.x, l.get("tool1")!.x, l.get("output")!.x],
+    [PAD + 3 * (NODE_W + GAP_X), PAD + 2 * (NODE_W + GAP_X), PAD + (NODE_W + GAP_X), PAD],
+    "newest-left：时序自右向左，最新的一拍贴画布左沿",
+  );
+  ok(
+    l.get("input")!.x > l.get("llm1")!.x &&
+      l.get("llm1")!.x > l.get("tool1")!.x &&
+      l.get("tool1")!.x > l.get("output")!.x,
+    "newest-left：越新越靠左（容器默认露出最左边 ⇒ 先看到最新）",
+  );
+  same(
+    [l.get("input")!.y, l.get("llm1")!.y, l.get("tool1")!.y, l.get("output")!.y],
+    [PAD, PAD, PAD, PAD],
+    "newest-left：单拍主干占一行（保持横向渲染方式）",
+  );
+  same(
+    [left.width, left.height],
+    [PAD * 2 + 4 * NODE_W + 3 * GAP_X, PAD * 2 + NODE_H],
+    "newest-left：画布 = 四拍宽 × 单行高",
+  );
+
+  fits(top, "newest-top 主干");
+  fits(left, "newest-left 主干");
+}
+
+// ── ② 容器随图生长：多一拍就多一段高度，且永远装得下 ─────────────────────────
+
+{
+  const four = layoutFlow(chain(), "newest-top");
+  const five = layoutFlow(chain(1), "newest-top");
+  same(
+    five.height - four.height,
+    NODE_H + GAP_Y,
+    "newest-top：多一拍 ⇒ 画布高一个「节点高 + 行距」，不挤在固定框里",
+  );
+  same(five.width, four.width, "newest-top：多一拍不改变横向尺寸（主干是一条竖列）");
+  fits(five, "newest-top 五拍");
+  fits(layoutFlow(chain(1), "newest-left"), "newest-left 五拍");
+
+  // 只开了头、还没有步骤的泳道：框也必须落在画布内（旧代码会把它画出画布右沿）。
+  fits(layoutFlow(idleLane(), "newest-top"), "newest-top 空泳道");
+  fits(layoutFlow(idleLane(), "newest-left"), "newest-left 空泳道");
+}
+
+// ── ③ 连线正确性：逐边核对端点 id 与像素锚点（两个方向都核对） ───────────────
+
+{
+  const g = withLane();
+  (["newest-top", "newest-left"] as const).forEach((orientation) => {
+    const layout = layoutFlow(g, orientation);
+    const placed = at(layout);
+    const shapes = edgeShapes(layout);
+
+    same(
+      shapes.map((s) => `${s.fromId}>${s.toId}`),
+      g.edges.map((e) => `${e.from}>${e.to}`),
+      `${orientation}：每条边都画出来，且顺序与图数据一致（不丢边、不重排）`,
+    );
+
+    shapes.forEach((s) => {
+      const from = placed.get(s.fromId);
+      const to = placed.get(s.toId);
+      ok(from !== undefined && to !== undefined, `${orientation}：边 ${s.fromId}>${s.toId} 的端点都在图里`);
+      const c = curve(s.d);
+      same([c.sx, c.sy], [s.sx, s.sy], `${orientation}：path 起点 = 声明起点`);
+      if (orientation === "newest-top") {
+        // 更早那拍在上方节点的**下沿**，更新那拍从**下沿**进 —— 箭头指向时间前进的方向。
+        same(
+          [c.sx, c.sy],
+          [from!.x + NODE_W / 2, from!.y],
+          `${orientation}：边 ${s.fromId}>${s.toId} 起点贴在 ${s.fromId}（更早那拍）的上边中点`,
+        );
+        same(
+          [c.tx, c.ty],
+          [to!.x + NODE_W / 2, to!.y + NODE_H],
+          `${orientation}：边 ${s.fromId}>${s.toId} 终点贴在 ${s.toId}（更新那拍）的下边中点`,
+        );
+        ok(c.c1y < c.sy && c.c2y > c.ty, `${orientation}：箭头自下而上，指向更新的节点`);
+      } else {
+        same(
+          [c.sx, c.sy],
+          [from!.x, from!.y + NODE_H / 2],
+          `${orientation}：边 ${s.fromId}>${s.toId} 起点贴在 ${s.fromId}（更早那拍）的左边中点`,
+        );
+        same(
+          [c.tx, c.ty],
+          [to!.x + NODE_W, to!.y + NODE_H / 2],
+          `${orientation}：边 ${s.fromId}>${s.toId} 终点贴在 ${s.toId}（更新那拍）的右边中点`,
+        );
+        ok(c.c1x < c.sx && c.c2x > c.tx, `${orientation}：箭头自右向左，指向更新的节点`);
+      }
+    });
+
+    // 泳道内的边仍然标成泳道边（虚线 + accent），主干边仍是实线。
+    const byKey = new Map(shapes.map((s) => [`${s.fromId}>${s.toId}`, s.inLane]));
+    same(byKey.get("subA>llmA"), true, `${orientation}：泳道内步骤仍是泳道边`);
+    same(byKey.get("t1>output"), false, `${orientation}：主干续接仍是主干边`);
+  });
+
+  // 端点缺失的边如实丢弃：3 条边里 1 条悬空 ⇒ 只画 2 条（不伪造节点补上）。
+  const dangling = graph(
+    [node("a", "llm", "done"), node("b", "output", "done")],
+    [
+      { from: "a", to: "ghost" },
+      { from: "a", to: "b" },
+    ],
+  );
+  same(
+    edgeShapes(layoutFlow(dangling, "newest-top")).map((s) => `${s.fromId}>${s.toId}`),
+    ["a>b"],
+    "端点缺失的边被丢掉，不伪造",
+  );
+}
+
+// ── ④ 泳道仍成道：泳道框罩住自己的成员，且落在主干更新的一侧 ─────────────────
+
+{
+  const g = withLane();
+  const top = layoutFlow(g, "newest-top");
+  same(top.lanes.map((l) => l.id), ["subA"], "子代理各自成道");
+  const framed = top.bands.filter((b) => b.framed);
+  same(framed.length, 1, "泳道有独立的框");
+  const t = at(top);
+  const frame = framed[0];
+  ok(frame.x > t.get("input")!.x, "newest-top：泳道在主干右侧（时序轴之外并排），不挤占时序轴");
+  ["llmA", "toolA"].forEach((id) => {
+    const p = t.get(id)!;
+    ok(
+      p.x >= frame.x && p.x + NODE_W <= frame.x + frame.width &&
+        p.y >= frame.y && p.y + NODE_H <= frame.y + frame.height,
+      `newest-top：${id} 落在自己的泳道框内（仍成道）`,
+    );
+  });
+  ok(t.get("llmA")!.y < t.get("subA")!.y, "newest-top：泳道第一步比泳道根更新（更靠上）");
+  ok(t.get("toolA")!.y < t.get("llmA")!.y, "newest-top：泳道内链路继续向新的一端推进");
+  fits(top, "newest-top 带泳道");
+
+  const left = layoutFlow(g, "newest-left");
+  const l = at(left);
+  const lane = left.bands.filter((b) => b.framed)[0];
+  ok(lane.y > l.get("input")!.y + NODE_H, "newest-left：泳道叠在主干下方，不与主干同拍混排");
+  ["llmA", "toolA"].forEach((id) => {
+    const p = l.get(id)!;
+    ok(
+      p.x >= lane.x && p.x + NODE_W <= lane.x + lane.width &&
+        p.y >= lane.y && p.y + NODE_H <= lane.y + lane.height,
+      `newest-left：${id} 落在自己的泳道框内（仍成道）`,
+    );
+  });
+  ok(l.get("llmA")!.x < l.get("subA")!.x, "newest-left：泳道第一步比泳道根更新（更靠左）");
+  fits(left, "newest-left 带泳道");
+
+  // 没有两个节点落在同一个格子上（方向镜像不能让卡片重叠）。
+  ([top, left] as const).forEach((layout) => {
+    const slots = new Set(layout.nodes.map((p) => `${p.x},${p.y}`));
+    same(slots.size, layout.nodes.length, "每个节点都有自己的格子（不重叠）");
+  });
+}
+
+console.log(`flow/orientation.test.ts OK — ${checks} checks`);