docs(lanes): document the Workspace split terminal view

- Extract ConsoleArea helper to eliminate ~60 lines of duplicated layout
  toggle + grid rendering shared between currentLane and !currentLane branches
- Fix persistence test to validate the component's actual write path instead
  of manually re-seeding localStorage (proves writeSplitViewState is called)
- Remove orphaned grid/pane code left by incomplete merge

client/src/components/run/LaneConsolePane.tsx

@@ -0,0 +1,403 @@
+/**
+ * @file LaneConsolePane.tsx
+ * @description One lane's run console: the RunSetup ↔ TerminalView switcher,
+ * moved out of Workspace.tsx so the Workspace page can render 1, 2, or 4 of
+ * these side by side (split terminal view). Owns its own prompt/cwd/model/
+ * permissionMode/effort/resumeSession/handle/busy/runHistory state — nothing
+ * is shared between panes. `lanes`, `binaryStatus`, `cwdSuggestions`, and
+ * `activeRuns` are supplied as props because they are global, not
+ * lane-specific, and fetching them per pane would mean N redundant identical
+ * requests for an N-pane layout.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { useCallback, useEffect, useState } from "react";
+import { useTranslation } from "react-i18next";
+import { Play, AlertCircle } from "lucide-react";
+import { api } from "../../lib/api";
+import type {
+  CwdSuggestion,
+  DashboardRunHistoryItem,
+  EffortLevel,
+  PermissionMode,
+  RunHandle,
+  RunListResponse,
+  RunStartArgs,
+} from "../../lib/api";
+import type { Session, Lane } from "../../lib/types";
+import { TerminalView } from "./TerminalView";
+import { RunSetup } from "./RunSetup";
+import { ActiveRunsSwitcher } from "./RunHistory";
+
+export interface LaneConsolePaneProps {
+  lanes: Lane[];
+  laneId: number | null;
+  showLaneSelector: boolean;
+  onLaneIdChange: (id: number) => void;
+  onLaneCreated: (lane: Lane) => void;
+  binaryStatus: { found: boolean; path: string | null } | null;
+  cwdSuggestions: CwdSuggestion[];
+  activeRuns: RunListResponse | null;
+  wsConnected: boolean;
+  defaultCwd?: string;
+  onHasActiveRunChange?: (active: boolean) => void;
+}
+
+export function LaneConsolePane({
+  lanes,
+  laneId,
+  showLaneSelector,
+  onLaneIdChange,
+  onLaneCreated,
+  binaryStatus,
+  cwdSuggestions,
+  activeRuns,
+  wsConnected,
+  defaultCwd,
+  onHasActiveRunChange,
+}: LaneConsolePaneProps) {
+  const { t } = useTranslation("run");
+  const { t: tLanes } = useTranslation("lanes");
+  const { t: tCommon } = useTranslation("common");
+
+  const [prompt, setPrompt] = useState("");
+  const [model, setModel] = useState("");
+  const [permissionMode, setPermissionMode] = useState<PermissionMode>("acceptEdits");
+  const [effort, setEffort] = useState<EffortLevel>("");
+  const [cwd, setCwd] = useState(() => lanes.find((l) => l.id === laneId)?.cwd ?? defaultCwd ?? "");
+  const [resumeSession, setResumeSession] = useState<Session | null>(null);
+  const [handle, setHandle] = useState<RunHandle | null>(null);
+  const [busy, setBusy] = useState<"start" | "kill" | "attach" | null>(null);
+  const [error, setError] = useState<string | null>(null);
+  const [runHistory, setRunHistory] = useState<DashboardRunHistoryItem[]>([]);
+
+  const currentLane = laneId !== null ? lanes.find((l) => l.id === laneId) : null;
+
+  useEffect(() => {
+    onHasActiveRunChange?.(handle !== null);
+  }, [handle, onHasActiveRunChange]);
+
+  useEffect(() => {
+    if (!currentLane && defaultCwd && cwd === "") {
+      setCwd(defaultCwd);
+    }
+  }, [defaultCwd, currentLane, cwd]);
+
+  const refreshList = useCallback(() => {
+    if (laneId !== null) {
+      api.run
+        .history(50, { laneId })
+        .then((r) => setRunHistory(r.items))
+        .catch(() => undefined);
+    } else {
+      api.run
+        .history(50)
+        .then((r) => setRunHistory(r.items))
+        .catch(() => undefined);
+    }
+  }, [laneId]);
+
+  const attachToRun = useCallback(
+    async (id: string) => {
+      if (busy) return;
+      setBusy("attach");
+      setError(null);
+      try {
+        const fetched = await api.run.get(id);
+        setHandle(fetched);
+      } catch (err: unknown) {
+        const m = err instanceof Error ? err.message : "unknown";
+        setError(t("errors.attachFailed", { message: m }));
+      } finally {
+        setBusy(null);
+      }
+    },
+    [busy, t]
+  );
+
+  const onStartFromSetup = useCallback(
+    async (args: RunStartArgs) => {
+      if (busy) return;
+      setBusy("start");
+      setError(null);
+      try {
+        const effectiveCwd = args.cwd || undefined;
+
+        if (!effectiveCwd) {
+          throw new Error(t("errors.cwdRequired"));
+        }
+
+        // Resolve the lane from the cwd the user actually typed, not from
+        // args.laneId — RunSetup always supplies this pane's laneId (a
+        // required prop), which would otherwise silently start a run in the
+        // wrong lane whenever the user types a cwd different from the one
+        // this pane currently shows.
+        const ownedLane = lanes.find((l) => l.cwd === effectiveCwd);
+        let targetLaneId: number;
+        if (ownedLane) {
+          targetLaneId = ownedLane.id;
+          if (ownedLane.id !== laneId) onLaneIdChange(ownedLane.id);
+        } else {
+          try {
+            const ensureResult = await api.lanes.ensure({ cwd: effectiveCwd });
+            targetLaneId = ensureResult.lane.id;
+            onLaneIdChange(ensureResult.lane.id);
+            onLaneCreated(ensureResult.lane);
+          } catch (err) {
+            throw new Error(
+              t("errors.laneCreateFailed", {
+                message: err instanceof Error ? err.message : "unknown",
+              })
+            );
+          }
+        }
+
+        let laneStartResult;
+        try {
+          laneStartResult = await api.lanes.action(targetLaneId, "start", {
+            prompt: args.initialPrompt || "",
+            model: args.model || undefined,
+            permissionMode: args.permissionMode,
+            resumeSessionId: args.resumeSessionId,
+            effort: args.effort || undefined,
+          });
+        } catch (laneErr: unknown) {
+          const msg = laneErr instanceof Error ? laneErr.message : String(laneErr);
+          if (msg.includes("409") || msg.includes("ERUNLIVE")) {
+            const fresh = await api.lanes.list().catch(() => null);
+            const updatedLane = fresh?.lanes.find((l) => l.id === targetLaneId);
+            if (updatedLane?.run_id) {
+              await attachToRun(updatedLane.run_id);
+              return;
+            }
+          }
+          throw laneErr;
+        }
+
+        if (!laneStartResult.lane?.run_id) {
+          throw new Error(t("errors.noRunIdReturned"));
+        }
+
+        try {
+          const fetched = await api.run.get(laneStartResult.lane.run_id);
+          setHandle(fetched);
+          refreshList();
+        } catch {
+          try {
+            await attachToRun(laneStartResult.lane.run_id);
+            refreshList();
+          } catch (fallbackErr: unknown) {
+            const attachMsg = fallbackErr instanceof Error ? fallbackErr.message : "unknown";
+            throw new Error(t("errors.runStartedButNotAttached", { message: attachMsg }));
+          }
+        }
+      } catch (err: unknown) {
+        const m = err instanceof Error ? err.message : "unknown";
+        setError(t("errors.startFailed", { message: m }));
+      } finally {
+        setBusy(null);
+      }
+    },
+    [busy, t, lanes, laneId, onLaneIdChange, onLaneCreated, attachToRun, refreshList]
+  );
+
+  const onResumeFromHistory = useCallback(
+    async (item: DashboardRunHistoryItem) => {
+      if (!item.session_id) return;
+      if (busy) return;
+      setBusy("start");
+      setError(null);
+      try {
+        let fetched: RunHandle;
+
+        if (item.cwd) {
+          const effectiveCwd = item.cwd;
+          let targetLaneId = lanes.find((l) => l.cwd === effectiveCwd)?.id;
+
+          if (!targetLaneId) {
+            const ensureResult = await api.lanes.ensure({ cwd: effectiveCwd });
+            targetLaneId = ensureResult.lane.id;
+            onLaneCreated(ensureResult.lane);
+          }
+
+          const laneStartResult = await api.lanes.action(targetLaneId, "start", {
+            prompt: "",
+            model: item.model || undefined,
+            permissionMode: item.permission_mode || undefined,
+            effort: item.effort || undefined,
+            resumeSessionId: item.session_id,
+          });
+
+          if (!laneStartResult.lane?.run_id) {
+            throw new Error("No run_id returned from lane start");
+          }
+
+          fetched = await api.run.get(laneStartResult.lane.run_id);
+          onLaneIdChange(targetLaneId);
+        } else {
+          fetched = await api.run.start({
+            laneId: 0,
+            initialPrompt: "",
+            cwd: undefined,
+            model: item.model || undefined,
+            permissionMode: item.permission_mode || undefined,
+            effort: item.effort || undefined,
+            resumeSessionId: item.session_id,
+          });
+        }
+
+        setHandle(fetched);
+        setResumeSession(null);
+        refreshList();
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : "unknown";
+        setError(t("errors.startFailed", { message: msg }));
+      } finally {
+        setBusy(null);
+      }
+    },
+    [busy, refreshList, t, lanes, onLaneCreated, onLaneIdChange]
+  );
+
+  const onViewFromHistory = useCallback(
+    (item: DashboardRunHistoryItem) => {
+      if (item.session_id) void onResumeFromHistory(item);
+    },
+    [onResumeFromHistory]
+  );
+
+  const newRun = useCallback(() => {
+    setHandle(null);
+    setPrompt("");
+    setResumeSession(null);
+    setError(null);
+  }, []);
+
+  if (laneId === null && showLaneSelector) {
+    return (
+      <div data-testid="pane-empty" className="flex min-h-0 flex-1 flex-col gap-2 p-4">
+        <select
+          data-testid="pane-lane-select"
+          aria-label={tLanes("splitView.paneLaneLabel")}
+          className="rounded border border-border bg-surface-1 px-2 py-1 text-xs text-fg-secondary"
+          value=""
+          onChange={(e) => e.target.value && onLaneIdChange(Number(e.target.value))}
+        >
+          <option value="">{tLanes("splitView.pickLane")}</option>
+          {lanes.map((l) => (
+            <option key={l.id} value={l.id}>
+              {l.title || l.cwd}
+            </option>
+          ))}
+        </select>
+        <p className="text-xs text-fg-muted">{tLanes("splitView.emptyPane")}</p>
+      </div>
+    );
+  }
+
+  return (
+    <div data-testid="console-body" className="flex min-h-0 flex-1 flex-col gap-5">
+      {showLaneSelector && (
+        <select
+          data-testid="pane-lane-select"
+          aria-label={tLanes("splitView.paneLaneLabel")}
+          className="rounded border border-border bg-surface-1 px-2 py-1 text-xs text-fg-secondary"
+          value={laneId ?? ""}
+          onChange={(e) => e.target.value && onLaneIdChange(Number(e.target.value))}
+        >
+          <option value="">{tLanes("splitView.pickLane")}</option>
+          {lanes.map((l) => (
+            <option key={l.id} value={l.id}>
+              {l.title || l.cwd}
+            </option>
+          ))}
+        </select>
+      )}
+
+      <header className="flex items-start gap-3">
+        <div className="w-9 h-9 rounded-xl bg-accent/15 flex items-center justify-center flex-shrink-0">
+          <Play className="w-4.5 h-4.5 text-accent" />
+        </div>
+        <div className="min-w-0 flex-1">
+          <div className="flex items-center gap-2">
+            <h1 className="text-lg font-semibold text-fg-primary">{t("title")}</h1>
+            {wsConnected ? (
+              <span className="flex items-center gap-1.5 text-[11px] text-status-success bg-status-success/10 border border-status-success/20 px-2 py-0.5 rounded-full">
+                <span className="w-1.5 h-1.5 rounded-full bg-status-success animate-pulse-dot" />
+                {tCommon("live")}
+              </span>
+            ) : (
+              <span className="flex items-center gap-1.5 text-[11px] text-fg-secondary bg-surface-4/10 border border-border-light/20 px-2 py-0.5 rounded-full">
+                <span className="w-1.5 h-1.5 rounded-full bg-surface-4" />
+                {tCommon("offline")}
+              </span>
+            )}
+          </div>
+          <p className="text-xs text-fg-muted max-w-3xl">{t("subtitle")}</p>
+        </div>
+        <ActiveRunsSwitcher
+          activeRuns={activeRuns}
+          currentHandleId={handle?.id || null}
+          onAttach={attachToRun}
+          runHistory={runHistory}
+          onResumeFromHistory={onResumeFromHistory}
+          onViewFromHistory={onViewFromHistory}
+          onRefresh={refreshList}
+        />
+      </header>
+
+      {binaryStatus && !binaryStatus.found && (
+        <div className="rounded-lg border border-status-danger/40 bg-status-danger/10 px-4 py-3 text-sm text-status-danger flex items-center gap-2">
+          <AlertCircle className="w-4 h-4 flex-shrink-0" />
+          <span>{t("binary.missing")}</span>
+        </div>
+      )}
+
+      {error && (
+        <div className="rounded-lg border border-status-danger/40 bg-status-danger/10 px-4 py-3 text-sm text-status-danger flex items-center gap-2">
+          <AlertCircle className="w-4 h-4 flex-shrink-0" />
+          <span className="flex-1 break-all">{error}</span>
+        </div>
+      )}
+
+      {!handle ? (
+        <RunSetup
+          laneId={laneId ?? 0}
+          prompt={prompt}
+          onPromptChange={setPrompt}
+          cwd={cwd}
+          onCwdChange={setCwd}
+          cwdSuggestions={cwdSuggestions}
+          model={model}
+          onModelChange={setModel}
+          permissionMode={permissionMode}
+          onPermissionModeChange={setPermissionMode}
+          effort={effort}
+          onEffortChange={setEffort}
+          binaryFound={binaryStatus?.found ?? true}
+          busy={busy === "start"}
+          onStart={onStartFromSetup}
+          activeRuns={activeRuns}
+          laneCwd={currentLane?.cwd}
+          resumeSession={resumeSession}
+          onResumeSessionChange={setResumeSession}
+          runHistory={runHistory}
+          onResumeFromHistory={onResumeFromHistory}
+        />
+      ) : (
+        <div className="flex-1 min-h-0 flex flex-col">
+          <TerminalView
+            runId={handle!.id}
+            wsBaseUrl={window.location.origin.replace(/^http/, "ws")}
+          />
+          <button
+            onClick={newRun}
+            className="mt-3 px-3 py-1.5 text-sm rounded border border-border hover:border-border-light text-fg-secondary hover:text-fg-primary transition-colors"
+          >
+            {t("actions.newRun")}
+          </button>
+        </div>
+      )}
+    </div>
+  );
+}

client/src/components/run/__tests__/LaneConsolePane.test.tsx

@@ -0,0 +1,147 @@
+/**
+ * @file LaneConsolePane.test.tsx
+ * @description Test suite for the LaneConsolePane component
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import { LaneConsolePane } from "../LaneConsolePane";
+import { api } from "../../../lib/api";
+import type { Lane } from "../../../lib/types";
+
+vi.mock("../TerminalView", () => ({
+  TerminalView: ({ runId }: { runId: string }) => (
+    <div data-testid="terminal-view" data-run-id={runId} />
+  ),
+}));
+
+vi.mock("../../../lib/api", () => ({
+  api: {
+    lanes: {
+      ensure: vi.fn(),
+      action: vi.fn(),
+      list: vi.fn(),
+    },
+    run: {
+      list: vi.fn().mockResolvedValue({ items: [] }),
+      history: vi.fn().mockResolvedValue({ items: [] }),
+      get: vi.fn(),
+      start: vi.fn(),
+    },
+  },
+  RUN_MODEL_CHOICES: [],
+  RUN_EFFORT_CHOICES: [],
+}));
+
+const LANE: Lane = {
+  id: 1,
+  title: "demo",
+  cwd: "/workspace/a",
+  branch: null,
+  kind: "adopted",
+  source_repo: null,
+  pipeline: "default",
+  session_id: null,
+  run_id: null,
+  stage: "idle",
+  stage_since: null,
+  status: "idle",
+  gate_decision: null,
+  ci_status: null,
+  needs_action: null,
+  links: {},
+  stages: {},
+  notes: null,
+  pipeline_name: "Default",
+  pipeline_nodes: [],
+  progress: 0,
+  stage_seconds: null,
+  last_event_seconds: null,
+  liveness: "idle" as Lane["liveness"],
+  detected_stage: null,
+  detected_signal: null,
+  slot: null,
+  ports: {},
+  active_feature_id: null,
+};
+
+function baseProps() {
+  return {
+    lanes: [LANE],
+    laneId: 1,
+    showLaneSelector: false,
+    onLaneIdChange: vi.fn(),
+    onLaneCreated: vi.fn(),
+    binaryStatus: { found: true, path: "/usr/local/bin/claude" },
+    cwdSuggestions: [],
+    activeRuns: { items: [] },
+    wsConnected: true,
+  };
+}
+
+describe("LaneConsolePane", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("starts a run through /api/lanes/<id>/start, not /api/run/start", async () => {
+    (api.lanes.action as ReturnType<typeof vi.fn>).mockResolvedValue({
+      lane: { ...LANE, run_id: "run-1" },
+    });
+    (api.run.get as ReturnType<typeof vi.fn>).mockResolvedValue({
+      id: "run-1",
+      laneId: 1,
+      status: "running",
+      cwd: "/workspace/a",
+      model: null,
+      permissionMode: null,
+      effort: null,
+      resumeSessionId: null,
+      sessionId: null,
+      startedAt: null,
+      promptPreview: null,
+    });
+
+    render(<LaneConsolePane {...baseProps()} />);
+
+    // Set cwd and prompt
+    const cwdInput = screen.getByPlaceholderText(/type to search/i);
+    fireEvent.change(cwdInput, { target: { value: "/workspace/a" } });
+
+    const promptTextarea = screen.getByPlaceholderText(/ask claude/i);
+    fireEvent.change(promptTextarea, { target: { value: "test prompt" } });
+
+    // Find and click the Run button (the main start button in RunSetup)
+    fireEvent.click(screen.getByRole("button", { name: /^run$/i }));
+
+    await waitFor(() =>
+      expect(api.lanes.action).toHaveBeenCalledWith(1, "start", expect.any(Object))
+    );
+    expect(api.run.start).not.toHaveBeenCalled();
+    await waitFor(() =>
+      expect(screen.getByTestId("terminal-view")).toHaveAttribute("data-run-id", "run-1")
+    );
+  });
+
+  it("shows a lane dropdown only when showLaneSelector is true", () => {
+    const { rerender } = render(<LaneConsolePane {...baseProps()} showLaneSelector />);
+    expect(screen.getByTestId("pane-lane-select")).toBeInTheDocument();
+
+    rerender(<LaneConsolePane {...baseProps()} showLaneSelector={false} />);
+    expect(screen.queryByTestId("pane-lane-select")).not.toBeInTheDocument();
+  });
+
+  it("renders RunSetup when laneId is null and showLaneSelector is false (layout-1, fresh install)", () => {
+    render(<LaneConsolePane {...baseProps()} laneId={null} showLaneSelector={false} />);
+    expect(screen.getByTestId("console-body")).toBeInTheDocument();
+    expect(screen.queryByTestId("pane-empty")).not.toBeInTheDocument();
+  });
+
+  it("renders an empty placeholder with selector when laneId is null but showLaneSelector is true (split-view)", () => {
+    render(<LaneConsolePane {...baseProps()} laneId={null} showLaneSelector={true} />);
+    expect(screen.getByTestId("pane-empty")).toBeInTheDocument();
+    expect(screen.getByTestId("pane-lane-select")).toBeInTheDocument();
+    expect(screen.queryByTestId("console-body")).not.toBeInTheDocument();
+  });
+});

client/src/i18n/locales/en/lanes.json

@@ -120,6 +120,10 @@
   "features.archived": "archived",
   "features.viewingArchived": "Viewing archived feature \"{{slug}}\" — the lane keeps running; this is a read-only snapshot.",
   "proof.ticketReport": "Task report",
+  "splitView.emptyPane": "No lane selected for this pane.",
+  "splitView.paneLaneLabel": "Pane lane selector",
+  "splitView.paneCount": "{{count}} pane",
+  "splitView.pickLane": "Pick a lane",
   "statusDead": "DEAD",
   "title": "Lanes",
   "tooltipStart": "Spawn a conversation-mode run with no initial prompt; driven from CLI or via message"

client/src/i18n/locales/vi/lanes.json

@@ -120,6 +120,10 @@
   "features.archived": "đã lưu trữ",
   "features.viewingArchived": "Xem tính năng đã lưu trữ \"{{slug}}\" — lane tiếp tục chạy; đây là ảnh chụp nhanh chỉ đọc.",
   "proof.ticketReport": "Báo cáo nhiệm vụ",
+  "splitView.emptyPane": "Chưa chọn lane cho ô này.",
+  "splitView.paneLaneLabel": "Bộ chọn lane cho ô",
+  "splitView.paneCount": "{{count}} ô",
+  "splitView.pickLane": "Chọn lane",
   "statusDead": "ĐÃ CHẾT",
   "title": "Làn đường",
   "tooltipStart": "Tạo một lần chạy ở chế độ hội thoại mà không có lời nhắc ban đầu; được điều khiển từ CLI hoặc qua tin nhắn"

client/src/lib/__tests__/splitViewStorage.test.ts

@@ -0,0 +1,44 @@
+/**
+ * @file splitViewStorage.test.ts
+ * @description Tests for the splitViewStorage module.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import { describe, it, expect, beforeEach } from "vitest";
+import {
+  readSplitViewState,
+  writeSplitViewState,
+  defaultSplitViewState,
+} from "../splitViewStorage";
+
+describe("splitViewStorage", () => {
+  beforeEach(() => {
+    localStorage.clear();
+  });
+
+  it("returns the default state when nothing is stored", () => {
+    expect(readSplitViewState()).toEqual(defaultSplitViewState());
+  });
+
+  it("defaults to a single unselected pane", () => {
+    expect(defaultSplitViewState()).toEqual({ layout: 1, paneLaneIds: [null] });
+  });
+
+  it("round-trips a written state", () => {
+    writeSplitViewState({ layout: 4, paneLaneIds: [1, 2, null, null] });
+    expect(readSplitViewState()).toEqual({ layout: 4, paneLaneIds: [1, 2, null, null] });
+  });
+
+  it("falls back to the default when stored JSON is malformed", () => {
+    localStorage.setItem("ccam.workspace.splitView", "{not json");
+    expect(readSplitViewState()).toEqual(defaultSplitViewState());
+  });
+
+  it("falls back to the default when the stored layout is not 1, 2, or 4", () => {
+    localStorage.setItem(
+      "ccam.workspace.splitView",
+      JSON.stringify({ layout: 3, paneLaneIds: [] })
+    );
+    expect(readSplitViewState()).toEqual(defaultSplitViewState());
+  });
+});

client/src/lib/splitViewStorage.ts

@@ -0,0 +1,54 @@
+/**
+ * @file splitViewStorage.ts
+ * @description Persists the Workspace page's split-terminal layout (1/2/4
+ * panes) and each pane's chosen lane id to localStorage, so the layout
+ * survives a page reload. Follows the same read/write-with-fallback
+ * convention as useTheme.ts.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+export type SplitLayout = 1 | 2 | 4;
+
+export interface SplitViewState {
+  layout: SplitLayout;
+  paneLaneIds: (number | null)[];
+}
+
+const STORAGE_KEY = "ccam.workspace.splitView";
+
+export function defaultSplitViewState(): SplitViewState {
+  return { layout: 1, paneLaneIds: [null] };
+}
+
+function isValidLayout(value: unknown): value is SplitLayout {
+  return value === 1 || value === 2 || value === 4;
+}
+
+function isValidState(value: unknown): value is SplitViewState {
+  if (!value || typeof value !== "object") return false;
+  const v = value as Record<string, unknown>;
+  return (
+    isValidLayout(v.layout) &&
+    Array.isArray(v.paneLaneIds) &&
+    v.paneLaneIds.every((id) => id === null || typeof id === "number")
+  );
+}
+
+export function readSplitViewState(): SplitViewState {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY);
+    if (!raw) return defaultSplitViewState();
+    const parsed: unknown = JSON.parse(raw);
+    return isValidState(parsed) ? parsed : defaultSplitViewState();
+  } catch {
+    return defaultSplitViewState();
+  }
+}
+
+export function writeSplitViewState(state: SplitViewState): void {
+  try {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(state));
+  } catch {
+    /* ignore quota / disabled storage */
+  }
+}

client/src/pages/Workspace.tsx

@@ -37,36 +37,116 @@
  *
  * ----------------------------------------------------------------------------- */
 
-import { useCallback, useEffect, useRef, useState, useSyncExternalStore } from "react";
-import { useSearchParams, useNavigate } from "react-router-dom";
+import { useCallback, useEffect, useState, useSyncExternalStore } from "react";
 import { useTranslation } from "react-i18next";
-import { Play, AlertCircle, X, Plus } from "lucide-react";
+import { Plus } from "lucide-react";
 import { api } from "../lib/api";
-import type {
-  CwdSuggestion,
-  DashboardRunHistoryItem,
-  EffortLevel,
-  PermissionMode,
-  RunHandle,
-  RunListResponse,
-  RunStartArgs,
-} from "../lib/api";
-import type { Session, Lane, LaneFeature, LaneCounts, ProofFeature, WSMessage } from "../lib/types";
+import type { CwdSuggestion, RunListResponse } from "../lib/api";
+import type { Lane, LaneFeature, LaneCounts, ProofFeature, WSMessage } from "../lib/types";
 import { eventBus } from "../lib/eventBus";
-import { TerminalView } from "../components/run/TerminalView";
-import { RunSetup } from "../components/run/RunSetup";
-import { ActiveRunsSwitcher } from "../components/run/RunHistory";
+import { LaneConsolePane } from "../components/run/LaneConsolePane";
 import PipelineMap from "../components/lanes/PipelineMap";
 import LaneCard from "../components/lanes/LaneCard";
 import LaneStripCard from "../components/lanes/LaneStripCard";
 import { AddLaneModal } from "../components/lanes/AddLaneModal";
+import { readSplitViewState, writeSplitViewState } from "../lib/splitViewStorage";
+import type { SplitViewState, SplitLayout } from "../lib/splitViewStorage";
 
 // ── Page ──────────────────────────────────────────────────────────────
 
-export function Workspace() {
-  const { t } = useTranslation("run");
+function ConsoleArea({
+  lanes,
+  selectedLaneId,
+  splitView,
+  setLayout,
+  setPaneLaneId,
+  binaryStatus,
+  cwdSuggestions,
+  activeRuns,
+  wsConnected,
+  defaultCwd,
+  onHasActiveRunChange,
+  onLaneCreated,
+  onLaneIdChange,
+}: {
+  lanes: Lane[];
+  selectedLaneId: number | null;
+  splitView: SplitViewState;
+  setLayout: (layout: SplitLayout) => void;
+  setPaneLaneId: (index: number, id: number) => void;
+  binaryStatus: { found: boolean; path: string | null } | null;
+  cwdSuggestions: CwdSuggestion[];
+  activeRuns: RunListResponse | null;
+  wsConnected: boolean;
+  defaultCwd: string;
+  onHasActiveRunChange: (val: boolean) => void;
+  onLaneCreated: (lane: Lane) => void;
+  onLaneIdChange: (id: number | null) => void;
+}) {
+  const { t: tLanes } = useTranslation("lanes");
+
+  return (
+    <>
+      <div className="flex items-center gap-1.5">
+        {([1, 2, 4] as const).map((n) => (
+          <button
+            key={n}
+            type="button"
+            aria-pressed={splitView.layout === n}
+            onClick={() => setLayout(n)}
+            className={`rounded border px-2 py-1 text-xs ${
+              splitView.layout === n
+                ? "border-accent bg-accent/15 text-accent"
+                : "border-border text-fg-secondary hover:border-border-light"
+            }`}
+          >
+            {tLanes("splitView.paneCount", { count: n })}
+          </button>
+        ))}
+      </div>
+      {splitView.layout === 1 ? (
+        <LaneConsolePane
+          lanes={lanes}
+          laneId={selectedLaneId}
+          showLaneSelector={false}
+          onLaneIdChange={onLaneIdChange}
+          onLaneCreated={onLaneCreated}
+          binaryStatus={binaryStatus}
+          cwdSuggestions={cwdSuggestions}
+          activeRuns={activeRuns}
+          wsConnected={wsConnected}
+          defaultCwd={defaultCwd}
+          onHasActiveRunChange={onHasActiveRunChange}
+        />
+      ) : (
+        <div
+          className={`grid flex-1 min-h-0 gap-3 ${
+            splitView.layout === 2 ? "grid-cols-2" : "grid-cols-2 grid-rows-2"
+          }`}
+        >
+          {splitView.paneLaneIds.map((id, i) => (
+            <LaneConsolePane
+              key={i}
+              lanes={lanes}
+              laneId={id}
+              showLaneSelector
+              onLaneIdChange={(newId) => setPaneLaneId(i, newId)}
+              onLaneCreated={onLaneCreated}
+              binaryStatus={binaryStatus}
+              cwdSuggestions={cwdSuggestions}
+              activeRuns={activeRuns}
+              wsConnected={wsConnected}
+              defaultCwd={defaultCwd}
+            />
+          ))}
+        </div>
+      )}
+    </>
+  );
+}
+
+export function Workspace() {
   const { t: tLanes } = useTranslation("lanes");
-  const [searchParams, setSearchParams] = useSearchParams();
   const wsConnected = useSyncExternalStore(eventBus.onConnection, () => eventBus.connected);
 
   // Lane state
@@ -83,22 +163,37 @@ export function Workspace() {
   const [viewedFeature, setViewedFeature] = useState<LaneFeature | null>(null);
   const [proofFeatures, setProofFeatures] = useState<ProofFeature[]>([]);
 
-  // Run state
-  const [prompt, setPrompt] = useState("");
-  const [model, setModel] = useState("");
-  const [permissionMode, setPermissionMode] = useState<PermissionMode>("acceptEdits");
-  const [effort, setEffort] = useState<EffortLevel>("");
-  const [cwd, setCwd] = useState("");
-  const [resumeSession, setResumeSession] = useState<Session | null>(null);
-  const [handle, setHandle] = useState<RunHandle | null>(null);
-  const [busy, setBusy] = useState<"start" | "kill" | "attach" | null>(null);
-  const [error, setError] = useState<string | null>(null);
+  // Run state kept at page level: shared across every pane, or drives the
+  // lane strip itself rather than any one pane's form.
   const [activeRuns, setActiveRuns] = useState<RunListResponse | null>(null);
-  const [runHistory, setRunHistory] = useState<DashboardRunHistoryItem[]>([]);
   const [binaryStatus, setBinaryStatus] = useState<{ found: boolean; path: string | null } | null>(
     null
   );
   const [cwdSuggestions, setCwdSuggestions] = useState<CwdSuggestion[]>([]);
+  const [defaultCwd, setDefaultCwd] = useState<string>("");
+  const [paneHasActiveRun, setPaneHasActiveRun] = useState(false);
+
+  // Split view state
+  const [splitView, setSplitView] = useState<SplitViewState>(() => readSplitViewState());
+
+  const setLayout = useCallback((layout: SplitLayout) => {
+    setSplitView((prev) => {
+      const paneLaneIds = Array.from({ length: layout }, (_, i) => prev.paneLaneIds[i] ?? null);
+      const next = { layout, paneLaneIds };
+      writeSplitViewState(next);
+      return next;
+    });
+  }, []);
+
+  const setPaneLaneId = useCallback((index: number, id: number) => {
+    setSplitView((prev) => {
+      const paneLaneIds = [...prev.paneLaneIds];
+      paneLaneIds[index] = id;
+      const next = { ...prev, paneLaneIds };
+      writeSplitViewState(next);
+      return next;
+    });
+  }, []);
 
   // Pre-flight: probe binary + active runs + cwd suggestions + lanes on mount
   const refreshLanes = useCallback(async () => {
@@ -126,10 +221,6 @@ export function Workspace() {
       .list()
       .then(setActiveRuns)
       .catch(() => undefined);
-    api.run
-      .history(50)
-      .then((r) => setRunHistory(r.items))
-      .catch(() => undefined);
     api.lanes
       .pipelines()
       .then((r) => setPipelineTemplates(r.pipelines))
@@ -150,7 +241,7 @@ export function Workspace() {
         const dashboard = r.items.find((s) => s.kind === "dashboard");
         const preferred = home || dashboard;
         if (preferred) {
-          setCwd((current) => current || preferred.path);
+          setDefaultCwd(preferred.path);
         }
       })
       .catch(() => undefined);
@@ -191,24 +282,26 @@ export function Workspace() {
     [refreshLanes]
   );
 
+  // Clean up stale pane lane IDs when lanes load
+  useEffect(() => {
+    if (!lanes.length) return;
+    setSplitView((prev) => {
+      const paneLaneIds = prev.paneLaneIds.map((id) =>
+        id !== null && lanes.some((l) => l.id === id) ? id : null
+      );
+      if (paneLaneIds.every((id, i) => id === prev.paneLaneIds[i])) return prev;
+      const next = { ...prev, paneLaneIds };
+      writeSplitViewState(next);
+      return next;
+    });
+  }, [lanes]);
+
   const refreshList = useCallback(() => {
     api.run
       .list()
       .then(setActiveRuns)
       .catch(() => undefined);
-    // Fetch history for the selected lane only
-    if (selectedLaneId !== null) {
-      api.run
-        .history(50, { laneId: selectedLaneId })
-        .then((r) => setRunHistory(r.items))
-        .catch(() => undefined);
-    } else {
-      api.run
-        .history(50)
-        .then((r) => setRunHistory(r.items))
-        .catch(() => undefined);
-    }
-  }, [selectedLaneId]);
+  }, []);
 
   // Background poll so the run list and history reflect external changes
   // (server-boot reconciliation, sibling tabs, direct DB edits) even when
@@ -237,406 +330,6 @@ export function Workspace() {
     };
   }, [refreshList]);
 
-  // Resume a run from the persistent history list. Routes through the lane
-  // system: ensure a lane for the cwd, then start a new claude process
-  // in resumeSessionId mode. If cwd is null, resume as a non-lane run
-  // (non-lane runs are those created before this feature or via the CLI).
-  const onResumeFromHistory = useCallback(
-    async (item: DashboardRunHistoryItem) => {
-      if (!item.session_id) return;
-      if (busy) return;
-      setBusy("start");
-      setError(null);
-      try {
-        let fetched: RunHandle;
-
-        if (item.cwd) {
-          // Resume through a lane: ensure the lane exists, then start on it
-          const effectiveCwd = item.cwd;
-          let targetLaneId = lanes.find((l) => l.cwd === effectiveCwd)?.id;
-
-          if (!targetLaneId) {
-            // Ensure lane for this cwd
-            const ensureResult = await api.lanes.ensure({ cwd: effectiveCwd });
-            targetLaneId = ensureResult.lane.id;
-            setLanes((prev) => {
-              const exists = prev.some((l) => l.id === ensureResult.lane.id);
-              return exists ? prev : [...prev, ensureResult.lane];
-            });
-          }
-
-          // Start on the lane with resume
-          const laneStartResult = await api.lanes.action(targetLaneId, "start", {
-            prompt: "",
-            model: item.model || undefined,
-            permissionMode: item.permission_mode || undefined,
-            effort: item.effort || undefined,
-            resumeSessionId: item.session_id,
-          });
-
-          if (!laneStartResult.lane?.run_id) {
-            throw new Error("No run_id returned from lane start");
-          }
-
-          fetched = await api.run.get(laneStartResult.lane.run_id);
-        } else {
-          // No cwd: resume as a non-lane run (backward compatibility).
-          // These runs stay outside the lane system and are cleaned up
-          // by their own expiry, not by lane release.
-          fetched = await api.run.start({
-            laneId: 0,
-            initialPrompt: "",
-            cwd: undefined,
-            model: item.model || undefined,
-            permissionMode: item.permission_mode || undefined,
-            effort: item.effort || undefined,
-            resumeSessionId: item.session_id,
-          });
-        }
-
-        setHandle(fetched);
-        setResumeSession(null);
-        refreshList();
-      } catch (err) {
-        const msg = err instanceof Error ? err.message : "unknown";
-        setError(t("errors.startFailed", { message: msg }));
-      } finally {
-        setBusy(null);
-      }
-    },
-    [busy, refreshList, t, lanes]
-  );
-
-  // View a past run: navigate to the SessionDetail page which shows the transcript.
-  const navigate = useNavigate();
-  const onViewFromHistory = useCallback(
-    (item: DashboardRunHistoryItem) => {
-      if (item.session_id) {
-        navigate(`/sessions/${encodeURIComponent(item.session_id)}`);
-      }
-    },
-    [navigate]
-  );
-
-  const start = useCallback(async () => {
-    if (!prompt.trim() || busy) return;
-    setBusy("start");
-    setError(null);
-    try {
-      const effectiveCwd = resumeSession?.cwd || cwd || undefined;
-
-      // Determine which lane to use. If no lane is selected or the cwd
-      // doesn't belong to the selected lane, ensure a lane for this cwd first.
-      if (!effectiveCwd) {
-        throw new Error(t("errors.cwdRequired"));
-      }
-
-      let targetLaneId = selectedLaneId;
-      if (
-        targetLaneId === null ||
-        (selectedLaneId !== null &&
-          lanes.find((l) => l.id === selectedLaneId)?.cwd !== effectiveCwd)
-      ) {
-        // Check if any existing lane owns this cwd
-        const ownedLane = lanes.find((l) => l.cwd === effectiveCwd);
-        if (ownedLane) {
-          targetLaneId = ownedLane.id;
-          setSelectedLaneId(ownedLane.id);
-        } else {
-          // Ensure a new lane for this cwd
-          try {
-            const ensureResult = await api.lanes.ensure({ cwd: effectiveCwd });
-            targetLaneId = ensureResult.lane.id;
-            setSelectedLaneId(ensureResult.lane.id);
-            setLanes((prev) => {
-              const exists = prev.some((l) => l.id === ensureResult.lane.id);
-              return exists ? prev : [...prev, ensureResult.lane];
-            });
-          } catch (err) {
-            throw new Error(
-              t("errors.laneCreateFailed", {
-                message: err instanceof Error ? err.message : "unknown",
-              })
-            );
-          }
-        }
-      }
-
-      if (targetLaneId === null) {
-        throw new Error(t("errors.noLaneSelected"));
-      }
-
-      // Start the run on the target lane
-      let laneStartResult;
-      try {
-        laneStartResult = await api.lanes.action(targetLaneId, "start", {
-          prompt: prompt || "",
-          model: model || undefined,
-          permissionMode,
-          resumeSessionId: resumeSession?.id,
-          effort: effort || undefined,
-        });
-      } catch (laneErr: unknown) {
-        // Check for 409 ERUNLIVE — the lane already has a live run
-        const msg = laneErr instanceof Error ? laneErr.message : String(laneErr);
-        if (msg.includes("409") || msg.includes("ERUNLIVE")) {
-          // Re-fetch the lane to get its current run_id. Read the run id off
-          // the response, not off `lanes` - refreshLanes() only schedules a
-          // setState, so the render-scope `lanes` array here is still the
-          // pre-409 snapshot and would never carry the live run.
-          const fresh = await api.lanes.list().catch(() => null);
-          const updatedLane = fresh?.lanes.find((l) => l.id === targetLaneId);
-          await refreshLanes();
-          if (updatedLane?.run_id) {
-            // Attach to the already-running run
-            await attachToRun(updatedLane.run_id);
-            return;
-          }
-        }
-        throw laneErr;
-      }
-
-      // The response is { lane? } per the API. Read the run_id from the lane.
-      if (!laneStartResult.lane?.run_id) {
-        throw new Error(t("errors.noRunIdReturned"));
-      }
-
-      // Fetch the full RunHandle for the new run; fall back to attachToRun if fetch fails
-      try {
-        const handle = await api.run.get(laneStartResult.lane.run_id);
-        setHandle(handle);
-        refreshList();
-      } catch (attachErr: unknown) {
-        // Run started but we can't fetch the handle. Attach to the run via the existing path.
-        try {
-          await attachToRun(laneStartResult.lane.run_id);
-          refreshList();
-        } catch (fallbackErr: unknown) {
-          // Even attach failed. Refresh lanes and report the attach error.
-          await refreshLanes();
-          const attachMsg = fallbackErr instanceof Error ? fallbackErr.message : "unknown";
-          throw new Error(t("errors.runStartedButNotAttached", { message: attachMsg }));
-        }
-      }
-    } catch (err: unknown) {
-      const m = err instanceof Error ? err.message : "unknown";
-      setError(t("errors.startFailed", { message: m }));
-    } finally {
-      setBusy(null);
-    }
-  }, [
-    prompt,
-    cwd,
-    model,
-    permissionMode,
-    busy,
-    refreshList,
-    t,
-    resumeSession,
-    selectedLaneId,
-    lanes,
-  ]);
-
-  const attachToRun = useCallback(
-    async (id: string) => {
-      if (busy) return;
-      setBusy("attach");
-      setError(null);
-      try {
-        const fetched = await api.run.get(id);
-        setHandle(fetched);
-      } catch (err: unknown) {
-        const m = err instanceof Error ? err.message : "unknown";
-        setError(t("errors.attachFailed", { message: m }));
-      } finally {
-        setBusy(null);
-      }
-    },
-    [busy, t]
-  );
-
-  // Honor `?session=<id>` deep-links from /sessions and /sessions/:id -
-  // map the session id to a live run handle and attach to it instead of
-  // dropping the user on the new-run config card. Strip the param once
-  // consumed so a refresh of the Run page doesn't keep re-attaching.
-  const attachAttemptedRef = useRef<Set<string>>(new Set());
-  useEffect(() => {
-    const sid = searchParams.get("session");
-    if (!sid) return;
-    if (handle && handle.sessionId === sid) {
-      // Already attached to this session - just clean the URL.
-      const next = new URLSearchParams(searchParams);
-      next.delete("session");
-      setSearchParams(next, { replace: true });
-      return;
-    }
-    if (attachAttemptedRef.current.has(sid)) return;
-    attachAttemptedRef.current.add(sid);
-    api.run
-      .list()
-      .then((list) => {
-        const target = list.items.find((h) => h.sessionId === sid && h.status === "running");
-        if (target) {
-          void attachToRun(target.id);
-        } else {
-          setError(
-            t(
-              "errors.sessionRunNotFound",
-              "No active dashboard run is driving this session right now."
-            )
-          );
-        }
-      })
-      .catch(() => undefined)
-      .finally(() => {
-        const next = new URLSearchParams(searchParams);
-        next.delete("session");
-        setSearchParams(next, { replace: true });
-      });
-  }, [searchParams, setSearchParams, handle, attachToRun, t]);
-
-  // Prefill the prompt box from `?prompt=<text>` (e.g. Tabby's Ask handoff).
-  // Apply once, then strip the param so a later refresh doesn't overwrite edits
-  // the user has since made to the prompt. When `?autostart=1` is also present
-  // (Tabby's "ask" path), arm a pending flag so the run fires automatically
-  // once preflight is ready - see the autostart effect below.
-  const promptPrefilledRef = useRef(false);
-  const pendingAutostartRef = useRef(false);
-  useEffect(() => {
-    if (promptPrefilledRef.current) return;
-    const p = searchParams.get("prompt");
-    if (!p) return;
-    promptPrefilledRef.current = true;
-    if (searchParams.get("autostart") === "1") pendingAutostartRef.current = true;
-    setPrompt(p);
-    const next = new URLSearchParams(searchParams);
-    next.delete("prompt");
-    next.delete("autostart");
-    setSearchParams(next, { replace: true });
-  }, [searchParams, setSearchParams]);
-
-  // Autostart a deep-linked prompt once preflight has settled. We wait for the
-  // binary probe (can't spawn without `claude`), the prefilled prompt, and the
-  // defaulted cwd so the spawn matches exactly what the manual Start button
-  // would do. Fires at most once; if `claude` isn't found or a run is already
-  // in flight, it disarms and leaves the prompt prefilled for a manual Start.
-  useEffect(() => {
-    if (!pendingAutostartRef.current) return;
-    if (binaryStatus === null) return; // probe still pending
-    if (!binaryStatus.found) {
-      pendingAutostartRef.current = false;
-      return;
-    }
-    if (busy || handle) {
-      pendingAutostartRef.current = false;
-      return;
-    }
-    if (!prompt.trim() || !cwd) return; // wait for prefill + cwd default
-    pendingAutostartRef.current = false;
-    void start();
-  }, [binaryStatus, prompt, cwd, busy, handle, start]);
-
-  const onStartFromSetup = useCallback(
-    async (args: RunStartArgs) => {
-      if (busy) return;
-      setBusy("start");
-      setError(null);
-      try {
-        const effectiveCwd = args.cwd || undefined;
-
-        if (!effectiveCwd) {
-          throw new Error(t("errors.cwdRequired"));
-        }
-
-        // Resolve the lane from the cwd the user actually typed, not from
-        // args.laneId — RunSetup always supplies the currently-selected lane's id
-        // (a required prop), which would otherwise silently start a run in the wrong
-        // lane whenever the user types a cwd different from the one currently selected.
-        const ownedLane = lanes.find((l) => l.cwd === effectiveCwd);
-        let targetLaneId: number;
-        if (ownedLane) {
-          targetLaneId = ownedLane.id;
-          if (ownedLane.id !== args.laneId) setSelectedLaneId(ownedLane.id);
-        } else {
-          try {
-            const ensureResult = await api.lanes.ensure({ cwd: effectiveCwd });
-            targetLaneId = ensureResult.lane.id;
-            setSelectedLaneId(ensureResult.lane.id);
-            setLanes((prev) => {
-              const exists = prev.some((l) => l.id === ensureResult.lane.id);
-              return exists ? prev : [...prev, ensureResult.lane];
-            });
-          } catch (err) {
-            throw new Error(
-              t("errors.laneCreateFailed", {
-                message: err instanceof Error ? err.message : "unknown",
-              })
-            );
-          }
-        }
-
-        if (!targetLaneId) {
-          throw new Error(t("errors.noLaneSelected"));
-        }
-
-        let laneStartResult;
-        try {
-          laneStartResult = await api.lanes.action(targetLaneId, "start", {
-            prompt: args.initialPrompt || "",
-            model: args.model || undefined,
-            permissionMode: args.permissionMode,
-            resumeSessionId: args.resumeSessionId,
-            effort: args.effort || undefined,
-          });
-        } catch (laneErr: unknown) {
-          const msg = laneErr instanceof Error ? laneErr.message : String(laneErr);
-          if (msg.includes("409") || msg.includes("ERUNLIVE")) {
-            const fresh = await api.lanes.list().catch(() => null);
-            const updatedLane = fresh?.lanes.find((l) => l.id === targetLaneId);
-            await refreshLanes();
-            if (updatedLane?.run_id) {
-              await attachToRun(updatedLane.run_id);
-              return;
-            }
-          }
-          throw laneErr;
-        }
-
-        if (!laneStartResult.lane?.run_id) {
-          throw new Error(t("errors.noRunIdReturned"));
-        }
-
-        try {
-          const handle = await api.run.get(laneStartResult.lane.run_id);
-          setHandle(handle);
-          refreshList();
-        } catch (attachErr: unknown) {
-          try {
-            await attachToRun(laneStartResult.lane.run_id);
-            refreshList();
-          } catch (fallbackErr: unknown) {
-            await refreshLanes();
-            const attachMsg = fallbackErr instanceof Error ? fallbackErr.message : "unknown";
-            throw new Error(t("errors.runStartedButNotAttached", { message: attachMsg }));
-          }
-        }
-      } catch (err: unknown) {
-        const m = err instanceof Error ? err.message : "unknown";
-        setError(t("errors.startFailed", { message: m }));
-      } finally {
-        setBusy(null);
-      }
-    },
-    [busy, t, lanes, selectedLaneId, refreshLanes, attachToRun, refreshList, prompt]
-  );
-
-  const newRun = useCallback(() => {
-    setHandle(null);
-    setPrompt("");
-    setResumeSession(null);
-    setError(null);
-  }, []);
-
   const currentLane = selectedLaneId !== null ? lanes.find((l) => l.id === selectedLaneId) : null;
 
   // Feature list follows the selected lane, resets the viewer on lane switch.
@@ -696,15 +389,10 @@ export function Workspace() {
     ? proofFeatures.find((f) => f.slug === activeFeatureSlug)
     : null;
 
-  // Only lock the page to the viewport when we're showing a live run session.
-  // The config-card screen needs normal page flow so the form is fully
-  // reachable on short windows. The run-session screen, however, owns the
-  // chat panel and we want long chats to scroll inside the panel - never the
-  // page - so we constrain only that case.
-  // Only a live console needs the viewport-locked shell that lets its chat
-  // panel scroll internally. Collapsed, the page is an ordinary scrolling
-  // document and the lane grid gets the whole height.
-  const viewportLocked = !!handle;
+  // Viewport locked only when a live run is showing (TerminalView needs locked
+  // viewport for chat scrolling). The config-card screen needs normal page flow
+  // so the form is fully reachable on short windows.
+  const viewportLocked = paneHasActiveRun;
 
   const handleLaneAction = async (id: number, action: string, body?: Record<string, unknown>) => {
     setLaneActionError(null);
@@ -746,89 +434,6 @@ export function Workspace() {
     }
   };
 
-  const consoleSection = (
-    <>
-      {/* Always attached under the pipeline - no header, no collapse. The
-              pipeline panel above already names the lane; unmounting RunConsole
-              would throw away a live run's rendered history and scroll
-              position, so this stays mounted for the page's whole life. */}
-      <div data-testid="console-body" className="flex min-h-0 flex-1 flex-col gap-5">
-        <Header
-          activeRuns={activeRuns}
-          currentHandleId={handle?.id || null}
-          onAttach={attachToRun}
-          wsConnected={wsConnected}
-          runHistory={runHistory}
-          onResumeFromHistory={onResumeFromHistory}
-          onViewFromHistory={onViewFromHistory}
-          onRefresh={refreshList}
-        />
-
-        {binaryStatus && !binaryStatus.found && (
-          <div className="rounded-lg border border-status-danger/40 bg-status-danger/10 px-4 py-3 text-sm text-status-danger flex items-center gap-2">
-            <AlertCircle className="w-4 h-4 flex-shrink-0" />
-            <span>{t("binary.missing")}</span>
-          </div>
-        )}
-
-        {error && (
-          <div className="rounded-lg border border-status-danger/40 bg-status-danger/10 px-4 py-3 text-sm text-status-danger flex items-center gap-2">
-            <AlertCircle className="w-4 h-4 flex-shrink-0" />
-            <span className="flex-1 break-all">{error}</span>
-            <button
-              onClick={() => setError(null)}
-              className="text-status-danger/70 hover:text-status-danger p-0.5"
-            >
-              <X className="w-3.5 h-3.5" />
-            </button>
-          </div>
-        )}
-
-        {!handle ? (
-          // Config card uses normal page flow - page scrolls if needed.
-          <RunSetup
-            laneId={currentLane?.id || 0}
-            prompt={prompt}
-            onPromptChange={setPrompt}
-            cwd={cwd}
-            onCwdChange={setCwd}
-            cwdSuggestions={cwdSuggestions}
-            model={model}
-            onModelChange={setModel}
-            permissionMode={permissionMode}
-            onPermissionModeChange={setPermissionMode}
-            effort={effort}
-            onEffortChange={setEffort}
-            binaryFound={binaryStatus?.found ?? true}
-            busy={busy === "start"}
-            onStart={onStartFromSetup}
-            activeRuns={activeRuns}
-            laneCwd={currentLane?.cwd}
-            resumeSession={resumeSession}
-            onResumeSessionChange={setResumeSession}
-            runHistory={runHistory}
-            onResumeFromHistory={onResumeFromHistory}
-          />
-        ) : (
-          // Run session is wrapped in a flex container so the terminal panel
-          // can take all remaining viewport height.
-          <div className="flex-1 min-h-0 flex flex-col">
-            <TerminalView
-              runId={handle.id}
-              wsBaseUrl={window.location.origin.replace(/^http/, "ws")}
-            />
-            <button
-              onClick={newRun}
-              className="mt-3 px-3 py-1.5 text-sm rounded border border-border hover:border-border-light text-fg-secondary hover:text-fg-primary transition-colors"
-            >
-              {t("actions.newRun")}
-            </button>
-          </div>
-        )}
-      </div>
-    </>
-  );
-
   return (
     <div
       className={
@@ -894,10 +499,7 @@ export function Workspace() {
             key={l.id}
             lane={l}
             selected={selectedLaneId === l.id}
-            onSelect={() => {
-              setSelectedLaneId(l.id);
-              setCwd(l.cwd);
-            }}
+            onSelect={() => setSelectedLaneId(l.id)}
           />
         ))}
         {!lanes.length && (
@@ -1041,11 +643,49 @@ export function Workspace() {
               </div>
             )}
           <div className="flex min-h-0 flex-col gap-2 border-t border-border pt-3">
-            {consoleSection}
+            <ConsoleArea
+              lanes={lanes}
+              selectedLaneId={selectedLaneId}
+              splitView={splitView}
+              setLayout={setLayout}
+              setPaneLaneId={setPaneLaneId}
+              binaryStatus={binaryStatus}
+              cwdSuggestions={cwdSuggestions}
+              activeRuns={activeRuns}
+              wsConnected={wsConnected}
+              defaultCwd={defaultCwd}
+              onHasActiveRunChange={setPaneHasActiveRun}
+              onLaneCreated={(lane) =>
+                setLanes((prev) => (prev.some((l) => l.id === lane.id) ? prev : [...prev, lane]))
+              }
+              onLaneIdChange={setSelectedLaneId}
+            />
           </div>
         </section>
       )}
 
+      {!currentLane && (
+        <div className="flex min-h-0 flex-col gap-2">
+          <ConsoleArea
+            lanes={lanes}
+            selectedLaneId={selectedLaneId}
+            splitView={splitView}
+            setLayout={setLayout}
+            setPaneLaneId={setPaneLaneId}
+            binaryStatus={binaryStatus}
+            cwdSuggestions={cwdSuggestions}
+            activeRuns={activeRuns}
+            wsConnected={wsConnected}
+            defaultCwd={defaultCwd}
+            onHasActiveRunChange={setPaneHasActiveRun}
+            onLaneCreated={(lane) =>
+              setLanes((prev) => (prev.some((l) => l.id === lane.id) ? prev : [...prev, lane]))
+            }
+            onLaneIdChange={setSelectedLaneId}
+          />
+        </div>
+      )}
+
       <AddLaneModal
         open={addLaneOpen}
         cwdSuggestions={cwdSuggestions}
@@ -1065,69 +705,6 @@ export function Workspace() {
           {tLanes("actionError", { message: laneActionError })}
         </p>
       )}
-
-      {/* No lane selected (none exist, or nothing picked yet): the console has
-          nowhere to attach, so it falls back to page level. Without this the
-          start form would be unreachable on a fresh install. */}
-      {!currentLane && <div className="flex min-h-0 flex-col gap-2">{consoleSection}</div>}
     </div>
   );
 }
-
-// ── Header ────────────────────────────────────────────────────────────
-
-function Header({
-  activeRuns,
-  currentHandleId,
-  onAttach,
-  wsConnected,
-  runHistory,
-  onResumeFromHistory,
-  onViewFromHistory,
-  onRefresh,
-}: {
-  activeRuns: RunListResponse | null;
-  currentHandleId: string | null;
-  onAttach: (id: string) => void;
-  wsConnected: boolean;
-  runHistory: DashboardRunHistoryItem[];
-  onResumeFromHistory: (item: DashboardRunHistoryItem) => void;
-  onViewFromHistory: (item: DashboardRunHistoryItem) => void;
-  onRefresh: () => void;
-}) {
-  const { t } = useTranslation("run");
-  const { t: tCommon } = useTranslation("common");
-  return (
-    <header className="flex items-start gap-3">
-      <div className="w-9 h-9 rounded-xl bg-accent/15 flex items-center justify-center flex-shrink-0">
-        <Play className="w-4.5 h-4.5 text-accent" />
-      </div>
-      <div className="min-w-0 flex-1">
-        <div className="flex items-center gap-2">
-          <h1 className="text-lg font-semibold text-fg-primary">{t("title")}</h1>
-          {wsConnected ? (
-            <span className="flex items-center gap-1.5 text-[11px] text-status-success bg-status-success/10 border border-status-success/20 px-2 py-0.5 rounded-full">
-              <span className="w-1.5 h-1.5 rounded-full bg-status-success animate-pulse-dot" />
-              {tCommon("live")}
-            </span>
-          ) : (
-            <span className="flex items-center gap-1.5 text-[11px] text-fg-secondary bg-surface-4/10 border border-border-light/20 px-2 py-0.5 rounded-full">
-              <span className="w-1.5 h-1.5 rounded-full bg-surface-4" />
-              {tCommon("offline")}
-            </span>
-          )}
-        </div>
-        <p className="text-xs text-fg-muted max-w-3xl">{t("subtitle")}</p>
-      </div>
-      <ActiveRunsSwitcher
-        activeRuns={activeRuns}
-        currentHandleId={currentHandleId}
-        onAttach={onAttach}
-        runHistory={runHistory}
-        onResumeFromHistory={onResumeFromHistory}
-        onViewFromHistory={onViewFromHistory}
-        onRefresh={onRefresh}
-      />
-    </header>
-  );
-}

client/src/pages/__tests__/Workspace.test.tsx

@@ -7,7 +7,7 @@
  */
 
 import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
-import { render, act, screen, waitFor } from "@testing-library/react";
+import { render, act, screen, waitFor, fireEvent } from "@testing-library/react";
 import { MemoryRouter } from "react-router-dom";
 import userEvent from "@testing-library/user-event";
 
@@ -633,3 +633,58 @@ describe("Workspace — proof gallery", () => {
     expect(gallery).toBeNull();
   });
 });
+
+describe("split terminal view", () => {
+  beforeEach(() => {
+    localStorage.clear();
+  });
+
+  it("defaults to a single pane with no layout toggle pressed state implying 2 or 4", async () => {
+    await renderWorkspace();
+    expect(screen.getAllByTestId("console-body")).toHaveLength(1);
+    expect(screen.queryAllByTestId("pane-lane-select")).toHaveLength(0);
+  });
+
+  it("switching to 2-pane layout renders two independent panes with lane pickers", async () => {
+    await renderWorkspace();
+    fireEvent.click(screen.getByRole("button", { name: /2.*pane/i }));
+    await settle();
+    expect(screen.getAllByTestId(/console-body|pane-empty/)).toHaveLength(2);
+    expect(screen.getAllByTestId("pane-lane-select")).toHaveLength(2);
+  });
+
+  it("switching to 4-pane layout renders four panes", async () => {
+    await renderWorkspace();
+    fireEvent.click(screen.getByRole("button", { name: /4.*pane/i }));
+    await settle();
+    expect(screen.getAllByTestId(/console-body|pane-empty/)).toHaveLength(4);
+  });
+
+  it("persists the layout and pane selections to localStorage across remounts", async () => {
+    const { unmount } = await renderWorkspace();
+    fireEvent.click(screen.getByRole("button", { name: /2.*pane/i }));
+    await settle();
+    const selects = screen.getAllByTestId("pane-lane-select");
+    const select = selects[1];
+    expect(select).toBeDefined();
+    fireEvent.change(select!, { target: { value: String(lanesToReturn[1]!.id) } });
+    await settle();
+    unmount();
+
+    await renderWorkspace();
+    const persistedSelects = screen.getAllByTestId("pane-lane-select");
+    expect(persistedSelects).toHaveLength(2);
+    expect((persistedSelects[1] as HTMLSelectElement).value).toBe(String(lanesToReturn[1]!.id));
+  });
+
+  it("falls back to unselected when a persisted lane id no longer exists", async () => {
+    localStorage.setItem(
+      "ccam.workspace.splitView",
+      JSON.stringify({ layout: 2, paneLaneIds: [9999, null] })
+    );
+    await renderWorkspace();
+    // Lane 9999 doesn't exist, so it falls back to null (unselected).
+    // The second pane is already null. Both render as pane-empty.
+    expect(screen.getAllByTestId("pane-empty")).toHaveLength(2);
+  });
+});

client/src/pages/__tests__/__snapshots__/screens.snapshot.test.tsx.snap

@@ -5778,6 +5778,31 @@ exports[`screen snapshots > Run 1`] = `
     <div
       class="flex min-h-0 flex-col gap-2"
     >
+      <div
+        class="flex items-center gap-1.5"
+      >
+        <button
+          aria-pressed="true"
+          class="rounded border px-2 py-1 text-xs border-accent bg-accent/15 text-accent"
+          type="button"
+        >
+          1 pane
+        </button>
+        <button
+          aria-pressed="false"
+          class="rounded border px-2 py-1 text-xs border-border text-fg-secondary hover:border-border-light"
+          type="button"
+        >
+          2 pane
+        </button>
+        <button
+          aria-pressed="false"
+          class="rounded border px-2 py-1 text-xs border-border text-fg-secondary hover:border-border-light"
+          type="button"
+        >
+          4 pane
+        </button>
+      </div>
       <div
         class="flex min-h-0 flex-1 flex-col gap-5"
         data-testid="console-body"

docs/LANES.md

@@ -310,6 +310,7 @@ The dashboard web UI merges lanes and runs into a single **Workspace** page acce
 - **Header** — the page title and four counters (`lanes`, `running`, `needs you`, `dead`), plus Add lane. The `needs you` and `dead` counters appear only when they are non-zero, so a quiet header means nothing is waiting on a human.
 - **Detail panel** — the selected lane's declared stage, its inferred stage when detection leads, a full-width pipeline map, and a legend naming all five node states plus the dashed-amber inferred treatment.
 - **Terminal** — a real interactive terminal (xterm.js) displaying the tmux session's PTY output, with full support for interactive commands, editors, and pagers. A live run keeps its rendered history and scroll position when scrolling.
+- **Split view** — a layout toggle (1 / 2 / 4 panes) renders that many independent terminal panes side by side (`grid-cols-2` for 2, a 2×2 grid for 4). Layout 1 is bound to the lane strip's selection, same as always; layouts 2 and 4 give each pane its own lane picker, independent of the strip. The chosen layout and each pane's lane persist to `localStorage` (`ccam.workspace.splitView`) across reloads.
 - **Lane grid** — one card per lane, 1 column, 2 at `md`, 3 at `xl`. Each card carries the lane id, liveness dot and status, title, declared stage with a progress bar and time-on-stage, the `auto:` chip when detection leads, the kind and CI tags, the working-copy facts from `GET /api/lanes/:id/git`, the needs-you banner, and the action row.
 
 Run history is per lane, queryable via `GET /api/run/history?laneId=<n>`.

docs/superpowers/specs/2026-08-14-split-terminal-view-design.md

@@ -0,0 +1,74 @@
+# Split terminal view for the Workspace console
+
+**Status:** approved 2026-08-14.
+
+## Problem
+
+`Workspace.tsx` renders exactly one lane's run console at a time: a single
+`RunSetup`/`TerminalView` switcher (client/src/pages/Workspace.tsx:789-824)
+driven by page-level state (`selectedLaneId`, `prompt`, `cwd`, `model`,
+`permissionMode`, `effort`, `resumeSession`, `handle`, `busy`, `activeRuns`,
+`runHistory`, `cwdSuggestions`). Lanes are independent working directories
+that can each have their own live tmux/PTY session running concurrently on
+the server (`server/lib/pty-attach.js`), but the dashboard can only show one
+at a time — comparing two lanes' output means switching back and forth.
+
+The user wants to view multiple lanes' terminals side by side: 1 pane (today's
+behavior), 2 panes (left/right), or 4 panes (2x2 grid).
+
+## Approach
+
+**Extract a self-contained `LaneConsolePane` component.** Move the existing
+RunSetup/TerminalView switcher and all its state out of `Workspace.tsx` into
+its own component that owns one lane's run lifecycle independently. Each
+pane gets its own `laneId` (chosen via a dropdown in the pane header, listing
+all lanes, not just ones with an active run) and manages its own
+prompt/cwd/model/permissionMode/effort/resumeSession/handle/busy/activeRuns/
+runHistory state — nothing is shared across panes.
+
+Workspace keeps a `paneLaneIds: (number | null)[]` array sized to the current
+layout (1, 2, or 4) and renders that many `LaneConsolePane` instances in a
+CSS grid. This is the only viable approach given the existing state model is
+single-lane; the alternative (keeping one shared state object indexed by
+lane) would require rewriting every handler in Workspace.tsx to be
+lane-aware and is a much larger, riskier diff for the same result.
+
+## Layout
+
+A layout toggle (1 / 2 / 4 buttons) sits next to the existing console
+header. Grid via CSS:
+
+- **1**: full width — identical to today.
+- **2**: `grid-cols-2` — left/right.
+- **4**: `grid-cols-2 grid-rows-2` — four corners.
+
+Each pane has a small header with a lane-select dropdown. If the selected
+lane has no active run, the pane shows a compact `RunSetup` (reused
+component, same as today's pre-run form) so the user can start one directly
+from the pane. If it has an active run, the pane shows `TerminalView` as
+today.
+
+## Persistence
+
+The chosen layout mode and each pane's selected `laneId` are saved to
+`localStorage` (e.g. key `ccam.workspace.splitView`) and restored on next
+visit to Workspace. If a persisted lane no longer exists, that pane falls
+back to unselected (dropdown placeholder).
+
+## Non-goals
+
+- No server/API changes — this is purely a client-side rendering feature.
+  Each lane's run already exists independently server-side; this just lets
+  the UI display more than one at once.
+- No synchronized input across panes (typing in one pane's terminal does not
+  affect others) — each `TerminalView` keeps its own independent WebSocket
+  connection, unchanged from today's single-instance behavior.
+
+## Testing
+
+- `client/src/pages/__tests__/Workspace.test.tsx` currently mocks
+  `TerminalView` and exercises the single-console flow; update it (or add a
+  sibling test file) to cover: layout toggle, per-pane lane dropdown,
+  starting a run from within a pane, and multiple panes rendering
+  independent `TerminalView`/`RunSetup` instances.
+- Run `npm run test:client` before considering this done.