/**
 * @file Workspace.tsx
 * @description Merged workspace page combining lanes (agent work units) and runs
 * (CLI spawns: Claude Code or Codex, determined per lane). The workspace shown
 * is picked in the sidebar's project tree and named by `?lane=<id>` (mirrored to
 * `agenthub.workspace.selected`, so a bare /workspace reopens the last one).
 * Shows the selected lane's pipeline map (when a template is installed) and run console (a
 * tab per group of up to four split panes over the live tmux slots 0–9, with a
 * `+` menu — `ConsoleTabs.tsx`), and the
 * right panel —
 * Files · Changes · Sessions. Runs are tied to lanes: starting a run
 * posts to POST /api/lanes/:id/start with tool-appropriate fields. When a cwd
 * isn't owned by any lane, calls POST /api/lanes/ensure first.
 * Tabs and pane headers name each live session (`runName`) and show its state;
 * a tab click replaces the history entry (Back leaves the session view, not
 * the last tab). Keyboard, outside a terminal: Alt+1–4 focus a pane, Alt+\\
 * splits the focused one right with a new terminal, Alt+W hides it. The
 * Changes panel resizes by its button's presets or by dragging (or arrow keys
 * on) its splitter; an unsaved edit in it is asked about before the panel
 * closes, switches tab, or moves to another workspace or session (it stays on
 * the old one until saved or discarded). Errors are toasts.
 *
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */
/* =============================================================================
 * MODULE_GUIDE — extended in-file reference (comments only; safe to read, never executed)
 * =============================================================================
 * ## Design constraints
 * - Local-first: no telemetry leaves the machine unless the user configures webhooks.
 * - Fail-safe hooks path on the server must never block Claude Code; UI mirrors that
 *   philosophy by degrading gracefully (empty states, stale badges, reconnect loops).
 * - Destructive flows stay behind explicit confirmation modals and server-side gates.
 * - Internationalization: user-visible strings belong in i18n JSON, not literals here.
 * - The console never writes a lane's stage: no POST /api/lanes/:id/stage calls.
 *
 * ## Internal dependencies
 * - `../lib/api` — REST client including lanes and run endpoints.
 * - `../lib/types` — Lane, Lane Counts, run handles, etc.
 * - `../components/lanes/` — LaneCard, PipelineMap, DestructiveLaneModal.
 * - `../components/run/` — ConsoleTabs, LaneConsolePane.
 *
 * ## Public surface
 * - `Workspace` — merged page; see TSDoc on the symbol for behavior.
 *
 * ============================================================================= */
/* -----------------------------------------------------------------------------
 * EXPORT CATALOG
 * **Workspace**
 *   The main exported page component. Merges lanes and runs into one workspace.
 *
 * ----------------------------------------------------------------------------- */

import { runWorktreeSession, type RunWorktree } from "../lib/runWorktree";
import { useCallback, useEffect, useMemo, useRef, useState } from "react";
import { useLocation, useNavigate, useSearchParams } from "react-router-dom";
import { useTranslation } from "react-i18next";
import {
  Plus,
  Columns2,
  Layers,
  PanelLeftClose,
  PanelRightClose,
  Maximize2,
  ChartColumn,
} from "lucide-react";
import { api } from "../lib/api";
import type { CwdSuggestion, RunHandle, RunListResponse } from "../lib/api";
import type { Lane, LaneFeature, ProofFeature, Session } from "../lib/types";
import { toast } from "../lib/toast";
import { confirmDialog, confirmDiscard } from "../lib/confirm";
import { keepIfSame } from "../lib/keepIfSame";
import { useWorkLanes } from "../hooks/useLanes";
import { LaneConsolePane } from "../components/run/LaneConsolePane";
import {
  ConsoleTabs,
  newTabBody,
  newTabTools,
  runName,
  runState,
} from "../components/run/ConsoleTabs";
import {
  Divider,
  type LayoutUpdate,
  PaneGrid,
  SplitMenus,
  usePaneGroups,
} from "../components/run/PaneGrid";
import {
  type Edge,
  type PaneGroups,
  type PaneLayout,
  MAX_PANES,
  activeLayout,
  closeInLayout,
  groupOf,
  leaves,
  moveInLayout,
  openInGroups,
  pane,
  pruneGroups,
  removeSlot,
  updateActive,
} from "../lib/paneLayout";
import { useAiTools } from "../hooks/useAiTools";
import { freeSlot, startInFreeTab } from "../components/lanes/startSession";
import { sessionWorktreeName } from "../components/lanes/WorkspaceSessionList";
import { LIVE_RUNS_EVENT } from "../components/WorkspaceTree";
import PipelineMap from "../components/lanes/PipelineMap";
import LaneCard, { since } from "../components/lanes/LaneCard";
import { AddLaneModal } from "../components/lanes/AddLaneModal";
import { LaneChangesPanel } from "../components/lanes/LaneChangesPanel";
import { LaneGitRailCounts } from "../components/lanes/LaneGitHeader";
import { WorkspaceHome } from "../components/lanes/WorkspaceHome";
import { SessionReplay } from "../components/lanes/SessionReplay";
import { DestructiveLaneModal } from "../components/lanes/DestructiveLaneModal";

/** localStorage key for the Changes panel's open/closed state. */
const CHANGES_OPEN_KEY = "agenthub.workspace.changesOpen";
/** localStorage key for how wide the Changes panel is. */
const CHANGES_SIZE_KEY = "agenthub.workspace.changesSize";
/** localStorage key for the last workspace shown, restored on a bare /workspace. */
const SELECTED_KEY = "agenthub.workspace.selected";

/** The three widths the Changes panel cycles through, then closed. Reading a
 *  diff and watching a console want opposite amounts of room, and which one is
 *  "work" changes several times an hour — hence ONE control that steps
 *  30/70 → 50/50 → full → closed, rather than a width button beside a
 *  collapse button that both live in the panel's tightest corner. */
const CHANGES_SIZES = ["compact", "half", "full"] as const;
type ChangesPreset = (typeof CHANGES_SIZES)[number];
/** A preset, or a width (panel fraction 0.15–0.85) the splitter was dragged to. */
type ChangesSize = ChangesPreset | number;
const CHANGES_WIDTH: Record<ChangesPreset, string> = {
  compact: "w-[30%]",
  half: "w-1/2",
  // The console beside it is HIDDEN, not unmounted: a live run's terminal
  // and a half-typed prompt must survive a round trip through full width.
  full: "w-full",
};
/** The icon the one resize control shows AT each size: what the next click
 *  gives you — an even split, the full width, then closed. */
const CHANGES_NEXT_ICON: Record<ChangesPreset, typeof Columns2> = {
  compact: Columns2,
  half: Maximize2,
  full: PanelRightClose,
};
/** The panel's share of the row, for the splitter. */
const changesRatio = (s: ChangesSize) =>
  typeof s === "number" ? s : s === "compact" ? 0.3 : s === "half" ? 0.5 : 1;
/** The preset a size counts as for the button: under ~45% is narrow. */
const changesStep = (s: ChangesSize): ChangesPreset =>
  s === "full" ? "full" : changesRatio(s) < 0.45 ? "compact" : "half";
const clampChanges = (r: number) => Math.min(0.85, Math.max(0.15, r));
/** The panel's own minimum (`min-w-[18rem]`), in px. */
const CHANGES_MIN_PX = 288;

// ── Page ──────────────────────────────────────────────────────────────

/** The pane slot a run id names (`agenthub-lane-<id>[-<slot>]`). */
function slotOf(runId: string | null | undefined): number {
  const m = runId?.match(/^agenthub-lane-\d+(?:-([1-9]))?$/);
  return m ? Number(m[1] || 0) : 0;
}

/** The session view's console: a tab bar whose every tab is a group of up to
 *  four split panes (`PaneGrid`; model in `lib/paneLayout.ts`), one
 *  `LaneConsolePane` per slot 0–9, each its own tmux session on the selected
 *  lane. The focused pane of the tab on screen is the URL's `?run=`: a plain
 *  open (a tab, a sidebar row) shows the tab holding that run — a session in
 *  no tab gets one of its own — and a split open (Ctrl/Cmd+click) brings it
 *  into the tab on screen, at the 2×2 grid's next place. Every live run
 *  stays MOUNTED, hidden with CSS while its tab is not shown, so neither
 *  switching tabs nor reshaping the panes ever drops a terminal. A pane whose
 *  run ends closes; the last tab gone leaves for the home. */
function ConsoleArea({
  lanes,
  selectedLaneId,
  binaryStatus,
  activeRuns,
  onHasActiveRunChange,
  attachRequest,
  onNewSession,
  onOpenRun,
  onRunsChanged,
}: {
  lanes: Lane[];
  selectedLaneId: number | null;
  binaryStatus: Record<string, { found: boolean; path: string | null }> | null;
  activeRuns: RunListResponse | null;
  onHasActiveRunChange: (val: boolean) => void;
  /** The opened run (`?run=`): its pane is the focused one. `split` opens it
   *  in a split (the grid's next place) instead; `focusOnly` (the URL following a
   *  focus change made here) never opens anything. */
  attachRequest: { runId: string; nonce: string; split?: boolean; focusOnly?: boolean } | null;
  /** Back to the workspace home, where a new session is started. */
  onNewSession?: () => void;
  /** Opens a run (`?run=`); `split` splits, `focusOnly` only follows the focus,
   *  `replace` adds no history entry (a tab click). */
  onOpenRun: (
    runId: string,
    opts?: { split?: boolean; focusOnly?: boolean; replace?: boolean }
  ) => void;
  /** A tab was opened or closed: re-read the run list now. */
  onRunsChanged: () => void;
}) {
  const { t } = useTranslation("lanes");
  const aiTools = useAiTools();
  const lane = lanes.find((l) => l.id === selectedLaneId) ?? null;
  const tabs = useMemo(
    () =>
      (activeRuns?.items ?? [])
        .filter((r) => r.laneId === selectedLaneId && r.status === "running")
        .sort((a, b) => (a.slot ?? 0) - (b.slot ?? 0)),
    [activeRuns, selectedLaneId]
  );
  const [groups, setGroups] = usePaneGroups(selectedLaneId);
  // The latest tabs, updated the moment a change is made: two changes in one
  // commit (an open request and a prune) must build on each other.
  const groupsRef = useRef(groups);
  groupsRef.current = groups;
  const layout = activeLayout(groups);
  // Slots opened here whose run the polled list has not caught up with yet,
  // each with the list it was opened against: pruning spares one until a
  // NEWER list still lacks it (a run that died before it was ever listed).
  const pending = useRef(new Map<number, RunListResponse | null>());
  // The workspace whose first run list was read. That first read prunes, so a
  // remembered layout loses its dead panes on arrival; after it a shown pane
  // closes on its terminal's exit, not on the polled list — one bad read (the
  // server answers an empty list on any tmux error) must not wipe a split.
  const listed = useRef<number | null>(null);
  // Runs seen ending here (`id@startedAt`): a list not yet refreshed must not
  // send the last pane to one of them.
  const exited = useRef(new Set<string>());
  const laneRef = useRef(selectedLaneId);
  laneRef.current = selectedLaneId;
  // The sessions the tabs hold — their names and states — re-read when a tab
  // opens or learns its session, when the lane's status moves, or on a rename.
  const [tabSessions, setTabSessions] = useState<Map<string, Session>>(new Map());
  const [sessionsVersion, setSessionsVersion] = useState(0);
  const tabSessionIds = tabs.map((r) => r.sessionId ?? "").join(",");
  useEffect(() => {
    if (selectedLaneId === null || !tabSessionIds.replace(/,/g, "")) return;
    let live = true;
    api.sessions
      .list({ lane: selectedLaneId, limit: 50 })
      .then((r) => live && setTabSessions(new Map(r.sessions.map((x) => [x.id, x]))))
      .catch(() => undefined);
    return () => {
      live = false;
    };
  }, [selectedLaneId, tabSessionIds, lane?.status, lane?.needs_action, sessionsVersion]);
  const sessionOf = (r: RunHandle) => (r.sessionId ? tabSessions.get(r.sessionId) : undefined);
  const label = (r: RunHandle) =>
    runName(r, sessionOf(r), aiTools.label(r.tool), t("tabs.terminal"));
  const stateOf = (r: RunHandle) => (r.tool === "shell" ? null : runState(sessionOf(r)));
  const runOf = (slot: number | null) => tabs.find((r) => (r.slot ?? 0) === slot);
  const runKey = (r: RunHandle) => `${r.id}@${r.startedAt}`;

  // The URL's `?run=` names the focused pane, so the right panel and the
  // sidebar read it. A change made HERE that moves the focus pushes it; there
  // is no effect watching the focus — an open request and that effect would
  // keep overriding each other. Session view only: the home and a replay
  // keep their URL.
  const followFocus = (next: PaneGroups) => {
    if (!attachRequest) return;
    const run = runOf(activeLayout(next).focus);
    if (run && run.id !== attachRequest.runId) onOpenRun(run.id, { focusOnly: true });
  };
  const changeGroups = (fn: (g: PaneGroups) => PaneGroups) => {
    const next = fn(groupsRef.current);
    if (next === groupsRef.current) return;
    groupsRef.current = next;
    setGroups(() => next);
    followFocus(next);
  };

  // Another workspace: nothing pending or exited carries over.
  useEffect(() => {
    pending.current.clear();
    exited.current.clear();
  }, [selectedLaneId]);

  // An open request (a new nonce): focus, replace or split. Re-run when the
  // lane arrives on a cold load; only this lane's own tabs.
  useEffect(() => {
    if (!attachRequest || selectedLaneId === null) return;
    if (!new RegExp(`^agenthub-lane-${selectedLaneId}(-[1-9])?$`).test(attachRequest.runId)) return;
    const slot = slotOf(attachRequest.runId);
    // The URL catching up with a focus change: by now that pane may be closed
    // or swapped, and re-opening it would undo what the user just did. Back/
    // Forward onto such an entry puts the real focus back in the URL instead.
    if (attachRequest.focusOnly) {
      const g = groupsRef.current;
      const at = groupOf(g, slot);
      if (at >= 0)
        changeGroups(() =>
          at === g.active && g.groups[at]?.focus === slot ? g : openInGroups(g, slot, false)
        );
      else followFocus(g);
      return;
    }
    if (!tabs.some((r) => (r.slot ?? 0) === slot)) pending.current.set(slot, activeRuns);
    changeGroups((g) => openInGroups(g, slot, attachRequest.split === true));
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [attachRequest?.nonce, selectedLaneId]);

  // The run list caught up: on a workspace's first read every pane whose run
  // is gone closes; after that only a pane opened here whose run never got
  // listed (a newer list still lacks it) does. A pane opened here whose run
  // just got listed takes the URL if it holds the focus.
  useEffect(() => {
    if (!activeRuns || selectedLaneId === null) return;
    const live = new Set(tabs.map((r) => r.slot ?? 0));
    const arrived: number[] = [];
    const expired = new Set<number>();
    for (const [s, list] of pending.current) {
      if (live.has(s)) arrived.push(s);
      else if (list !== activeRuns) expired.add(s);
      if (live.has(s) || list !== activeRuns) pending.current.delete(s);
    }
    const first = listed.current !== selectedLaneId;
    listed.current = selectedLaneId;
    const tabbed = groupsRef.current.groups.flatMap((l) => leaves(l.root));
    const keep = first
      ? new Set(pending.current.keys())
      : new Set(tabbed.filter((s) => !expired.has(s)));
    const before = groupsRef.current;
    changeGroups((g) => pruneGroups(g, live, keep));
    const focus = activeLayout(before).focus;
    if (groupsRef.current === before && focus !== null && arrived.includes(focus))
      followFocus(before);
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [activeRuns, tabs, selectedLaneId]);

  // A pane's run ended (it exited, or its tab was closed): its pane closes,
  // and in the session view the last one leaves for another tab, else the
  // home — the home and a replay only lose the pane, never their URL.
  const ended = (slot: number) => {
    onRunsChanged();
    const dead = runOf(slot);
    if (dead) exited.current.add(runKey(dead));
    if (groupOf(groupsRef.current, slot) < 0) return;
    changeGroups((g) => removeSlot(g, slot));
    if (groupsRef.current.groups.length || !attachRequest) return;
    const other = tabs.find((r) => (r.slot ?? 0) !== slot && !exited.current.has(runKey(r)));
    if (other) onOpenRun(other.id);
    else onNewSession?.();
  };

  // A pane header's X: stops that one session, as a one-pane tab's X does —
  // an AI session may be mid-turn, so it asks first; a shell holds no agent.
  const stopPane = async (slot: number) => {
    const run = runOf(slot);
    if (!run) return;
    if (
      run.tool !== "shell" &&
      !(await confirmDialog({
        title: t("tabs.stopTitle", { name: label(run) }),
        message: t("tabs.stopBody"),
        confirmLabel: t("tabs.stopConfirm"),
        destructive: true,
      }))
    )
      return;
    try {
      await api.run.kill(run.id);
      ended(slot);
    } catch (err) {
      toast.error(err);
    }
  };

  // A split menu's "New terminal" or AI tool (bare, as the tab bar's `+`
  // starts it) in the first free slot, placed on that side of the pane —
  // unless the workspace changed while it started.
  const free = lane ? freeSlot(lane.id, tabs) : null;
  const splitTools = lane ? newTabTools(lane, aiTools) : [];
  const newSplit = async (target: number, edge: Edge, tool?: string) => {
    if (!lane || free === null) return;
    const laneId = lane.id;
    try {
      const body = tool ? newTabBody(tool, lane, aiTools) : { shell: true };
      // The server picks the slot: the list `free` came from may be stale.
      const slot = slotOf(await startInFreeTab(laneId, body));
      onRunsChanged();
      if (laneRef.current !== laneId) return;
      pending.current.set(slot, activeRuns);
      change((l) => moveInLayout(l, slot, target, edge));
    } catch (err) {
      toast.error(err);
    }
  };

  const requested = attachRequest ? [slotOf(attachRequest.runId)] : [];
  // No layout yet (a first visit, a request not yet applied, or no run at
  // all): one pane, so the console always has its single render site.
  const fallback = requested[0] ?? 0;
  const view: PaneLayout = layout.root ? layout : { root: pane(fallback), focus: fallback };
  const viewGroups: PaneGroups = groups.groups.length ? groups : { groups: [view], active: 0 };
  // A change to the tab on screen (`PaneGrid`, the split menus). Tabs never
  // saved are the one-pane `view`: change that.
  const change: LayoutUpdate = (fn) =>
    changeGroups((g) => updateActive(g.groups.length ? g : viewGroups, fn));
  const shown = leaves(view.root);
  const mounted = [...new Set([...shown, ...tabs.map((r) => r.slot ?? 0)])].sort((a, b) => a - b);
  const focusSlot = view.focus;

  // Alt+1–4 focus a pane, Alt+\ splits the focused one right with a new
  // terminal, Alt+W takes it out into a tab of its own. Session view only, and never from inside a
  // terminal or a field, whose keys are their own (Ctrl+M lets Tab out of a
  // terminal first). Read through a ref: one listener, always current.
  const onKeys = useRef<(e: KeyboardEvent) => void>(() => undefined);
  const areaRef = useRef<HTMLDivElement>(null);
  onKeys.current = (e) => {
    if (!attachRequest || !e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) return;
    // Not under a dialog, and not while the console is hidden (the Changes
    // panel at full width, a replay, the home) — CSS-hidden, so by class.
    if (document.querySelector('[role="dialog"]')) return;
    if (!areaRef.current || areaRef.current.closest(".hidden")) return;
    const el = e.target as HTMLElement | null;
    if (el?.closest?.(".xterm")) return;
    if (el && (el.isContentEditable || /^(INPUT|TEXTAREA|SELECT)$/.test(el.tagName))) return;
    const digit = /^Digit([1-4])$/.exec(e.code);
    if (digit) {
      const s = shown[Number(digit[1]) - 1];
      if (s === undefined) return;
      e.preventDefault();
      change((l) => (l.root && l.focus !== s ? { ...l, focus: s } : l));
    } else if (e.code === "Backslash" && focusSlot !== null) {
      e.preventDefault();
      if (free !== null && shown.length < MAX_PANES) void newSplit(focusSlot, "right");
    } else if (e.code === "KeyW" && focusSlot !== null && shown.length > 1) {
      e.preventDefault();
      change((l) => closeInLayout(l, focusSlot));
    }
  };
  useEffect(() => {
    const on = (e: KeyboardEvent) => onKeys.current(e);
    document.addEventListener("keydown", on);
    return () => document.removeEventListener("keydown", on);
  }, []);

  return (
    <div ref={areaRef} className="flex min-h-0 flex-1 flex-col">
      {lane && (
        <ConsoleTabs
          lane={lane}
          tabs={tabs}
          groups={viewGroups}
          onGroupsChange={changeGroups}
          onOpen={(runId, split) => {
            onRunsChanged();
            // A tab click is not a new history entry: Back leaves the
            // session view instead of walking back through every tab.
            onOpenRun(runId, { split, replace: true });
          }}
          sessions={tabSessions}
          onRenamed={() => setSessionsVersion((v) => v + 1)}
          onClosed={(runId) => ended(slotOf(runId))}
          onHome={onNewSession}
          // While one pane is shown, its split menus (a split pane has its own).
          actions={
            shown.length === 1 && shown[0] !== undefined ? (
              <div className="flex items-center gap-1">
                <SplitMenus
                  slot={shown[0]}
                  shown={shown}
                  runs={tabs}
                  label={label}
                  onChange={change}
                  canStart={free !== null}
                  tools={splitTools}
                  toolLabel={aiTools.label}
                  onNewSplit={(target, edge, tool) => void newSplit(target, edge, tool)}
                />
              </div>
            ) : undefined
          }
        />
      )}
      <PaneGrid
        layout={view}
        mounted={mounted}
        runs={tabs}
        label={label}
        onChange={change}
        canStart={free !== null}
        tools={splitTools}
        toolLabel={aiTools.label}
        onNewSplit={(target, edge, tool) => void newSplit(target, edge, tool)}
        stateOf={stateOf}
        onStop={(slot) => void stopPane(slot)}
        renderPane={(slot) => (
          <LaneConsolePane
            lanes={lanes}
            laneId={selectedLaneId}
            slot={slot}
            binaryStatus={binaryStatus}
            activeRuns={activeRuns}
            onHasActiveRunChange={slot === focusSlot ? onHasActiveRunChange : undefined}
            onNewSession={onNewSession}
            onRunExit={() => ended(slot)}
            // Only the focused pane takes the keyboard when it appears.
            autoFocus={slot === focusSlot}
            attachRequest={
              attachRequest && slotOf(attachRequest.runId) === slot ? attachRequest : null
            }
          />
        )}
      />
    </div>
  );
}

export function Workspace() {
  const { t: tLanes } = useTranslation("lanes");
  const [searchParams, setSearchParams] = useSearchParams();

  // Lane state: the list is the shared store the sidebar reads too; the
  // selection is the URL's `?lane=` (the sidebar sets it, so does a
  // notification click), falling back to the last one shown, then the first.
  const { lanes, loaded: lanesLoaded, refresh: refreshLanes } = useWorkLanes();
  const laneParam = searchParams.get("lane");
  // `?run=` — a live session picked in the sidebar; the location key makes a
  // second pick of the same session a new request.
  const location = useLocation();
  const runParam = searchParams.get("run");
  // `?session=` — an ENDED session picked in the sidebar or Recents: its
  // conversation, with a prompt box whose message resumes it (SessionReplay).
  const sessionParam = runParam ? null : searchParams.get("session");
  const navigate = useNavigate();
  // A Ctrl/Cmd+click (tab or sidebar) opens the run in a split;
  // it rides on the navigation's state, never in the URL.
  const navState = location.state as { split?: unknown; focusOnly?: unknown } | null;
  const splitOpen = navState?.split === true;
  const focusOnly = navState?.focusOnly === true;
  const attachRequest = useMemo(
    () => (runParam ? { runId: runParam, nonce: location.key, split: splitOpen, focusOnly } : null),
    [runParam, location.key, splitOpen, focusOnly]
  );
  const paramId = laneParam === null ? null : Number(laneParam);
  const fallbackId = (() => {
    if (!lanesLoaded) return null;
    let stored: number | null = null;
    try {
      stored = Number(window.localStorage.getItem(SELECTED_KEY));
    } catch {
      /* disabled storage */
    }
    return lanes.find((l) => l.id === stored)?.id ?? lanes[0]?.id ?? null;
  })();
  const selectedLaneId =
    paramId !== null && lanes.some((l) => l.id === paramId) ? paramId : fallbackId;
  const setSelectedLaneId = useCallback(
    (id: number | null) =>
      setSearchParams(
        (prev) => {
          const next = new URLSearchParams(prev);
          // A run belongs to its lane: another lane opens on its home.
          if (next.get("lane") !== String(id)) {
            next.delete("run");
            next.delete("session");
          }
          if (id === null) next.delete("lane");
          else next.set("lane", String(id));
          return next;
        },
        { replace: true }
      ),
    [setSearchParams]
  );
  // Name the fallback in the URL, so the sidebar highlights it and F5 keeps it.
  // Only a URL naming NO lane is rewritten: one naming a lane the list has not
  // caught up with yet (just created) must survive until the refetch lands.
  useEffect(() => {
    if (!lanesLoaded || selectedLaneId === null) return;
    try {
      window.localStorage.setItem(SELECTED_KEY, String(selectedLaneId));
    } catch {
      /* disabled storage */
    }
    if (paramId === null) setSelectedLaneId(selectedLaneId);
  }, [lanesLoaded, selectedLaneId, paramId, setSelectedLaneId]);
  // A lane action's failure, as a toast (it stays until dismissed).
  const setLaneActionError = (message: string | null) => {
    if (message) toast.error(tLanes("actionError", { message }));
  };
  const [destructive, setDestructive] = useState<{
    lane: Lane;
    action: "reset" | "remove";
  } | null>(null);
  const [addLaneOpen, setAddLaneOpen] = useState(false);
  // Fields the Add-lane modal opens with when it was opened from a lane's git
  // bar ("new lane here"): one provisioning path for every lane, prefilled.
  const [addLanePrefill, setAddLanePrefill] = useState<{
    sourceRepo?: string;
    branch?: string;
  } | null>(null);
  const [viewedFeatureSlug, setViewedFeatureSlug] = useState<string | null>(null);
  const [features, setFeatures] = useState<LaneFeature[]>([]);
  const [pipelineTemplates, setPipelineTemplates] = useState<
    { id: string; name: string; nodes: { id: string }[] }[]
  >([]);
  const [viewedFeature, setViewedFeature] = useState<LaneFeature | null>(null);
  const [proofFeatures, setProofFeatures] = useState<ProofFeature[]>([]);

  // 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 [binaryStatus, setBinaryStatus] = useState<Record<
    string,
    { found: boolean; path: string | null }
  > | null>(null);
  const [cwdSuggestions, setCwdSuggestions] = useState<CwdSuggestion[]>([]);
  const [paneHasActiveRun, setPaneHasActiveRun] = useState(false);

  // Whether the Changes panel is open. A viewer preference, so it lives in
  // localStorage and never reaches the server — same rule as the lane strip's
  // order (client/src/lib/laneOrderStorage.ts).
  const [changesOpen, setChangesOpen] = useState(() => {
    try {
      return window.localStorage.getItem(CHANGES_OPEN_KEY) === "1";
    } catch {
      return false;
    }
  });
  useEffect(() => {
    try {
      window.localStorage.setItem(CHANGES_OPEN_KEY, changesOpen ? "1" : "0");
    } catch {
      /* private mode / disabled storage: the panel just forgets between visits */
    }
  }, [changesOpen]);
  // A preset name, or the fraction a splitter drag left (stored as a number).
  const [changesSize, setChangesSize] = useState<ChangesSize>(() => {
    try {
      const saved = window.localStorage.getItem(CHANGES_SIZE_KEY);
      if (saved && (CHANGES_SIZES as readonly string[]).includes(saved))
        return saved as ChangesPreset;
      const n = Number(saved);
      return saved && Number.isFinite(n) ? clampChanges(n) : "compact";
    } catch {
      return "compact";
    }
  });
  useEffect(() => {
    try {
      window.localStorage.setItem(CHANGES_SIZE_KEY, String(changesSize));
    } catch {
      /* same as above: a forgotten width, not an error */
    }
  }, [changesSize]);
  const changesFull = changesSize === "full";
  const changesPreset = changesStep(changesSize);
  const nextChangesSize =
    CHANGES_SIZES[(CHANGES_SIZES.indexOf(changesPreset) + 1) % CHANGES_SIZES.length]!;
  const changesNextLabel = changesFull
    ? tLanes("changes.collapse")
    : tLanes("changes.resize", { size: tLanes(`changes.size.${nextChangesSize}`) });
  const changesRowRef = useRef<HTMLDivElement>(null);
  // The row's width: the panel never gets narrower than its 18rem minimum,
  // so the splitter is drawn — and dragged — no further than that edge.
  const [rowWidth, setRowWidth] = useState(0);
  useEffect(() => {
    const el = changesRowRef.current;
    if (!el || typeof ResizeObserver === "undefined") return;
    const ro = new ResizeObserver(() => setRowWidth(el.clientWidth));
    ro.observe(el);
    setRowWidth(el.clientWidth);
    return () => ro.disconnect();
  }, []);
  const minChanges = rowWidth ? Math.min(0.85, CHANGES_MIN_PX / rowWidth) : 0.15;

  // The session the opened run holds, when that run works in a worktree of
  // its own (`claude --worktree`): the Changes panel shows that tree. A
  // replayed session (`?session=`) shows its own worktree the same way.
  const openedRun = runParam ? activeRuns?.items.find((r) => r.id === runParam) : undefined;
  // Its worktree is checked once (`GET …/git?session=`): an ended session's
  // worktree Claude already removed answers ENOWORKTREE, and the panel then
  // shows the workspace's own folder instead of an error.
  const [replayed, setReplayed] = useState<{ id: string; worktree: boolean } | null>(null);
  const replayLane = lanes.find((l) => l.id === selectedLaneId);
  useEffect(() => {
    setReplayed(null);
    if (!sessionParam || !replayLane) return;
    let live = true;
    void (async () => {
      try {
        const { session } = await api.sessions.get(sessionParam, { events: false });
        if (!sessionWorktreeName(replayLane, session)) {
          if (live) setReplayed({ id: sessionParam, worktree: false });
          return;
        }
        const ok = await api.lanes
          .git({ lane: replayLane.id, session: sessionParam })
          .then(() => true)
          .catch((err: { code?: string }) => err?.code !== "ENOWORKTREE");
        if (live) setReplayed({ id: sessionParam, worktree: ok });
      } catch {
        /* no row: the workspace's folder */
      }
    })();
    return () => {
      live = false;
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps -- the lane by id
  }, [sessionParam, replayLane?.id]);
  const runWorktree = useRef<RunWorktree | null>(null);
  runWorktree.current = runWorktreeSession(runWorktree.current, runParam, openedRun);
  const gitSession = runWorktree.current
    ? runWorktree.current.session
    : sessionParam && replayed?.id === sessionParam && replayed.worktree
      ? sessionParam
      : undefined;

  // An unsaved whole-file edit in the Changes panel. While it is open the
  // panel stays on the tree it was opened in — moving it (another workspace,
  // session or worktree) would remount it and drop the edit — until the user
  // says to discard it, or saves.
  const [changesDirty, setChangesDirty] = useState(false);
  const wantPanel =
    selectedLaneId === null ? null : { laneId: selectedLaneId, session: gitSession };
  const wantPanelKey = wantPanel ? `${wantPanel.laneId}:${wantPanel.session ?? ""}` : "";
  const [panelAt, setPanelAt] = useState(wantPanel);
  const panelKey = panelAt ? `${panelAt.laneId}:${panelAt.session ?? ""}` : "";
  const asking = useRef(false);
  useEffect(() => {
    if (wantPanelKey === panelKey) return;
    if (!changesDirty) {
      setPanelAt(wantPanel);
      return;
    }
    if (asking.current) return;
    asking.current = true;
    void confirmDiscard().then((ok) => {
      asking.current = false;
      if (!ok) return;
      setChangesDirty(false);
      setPanelAt(wantPanel);
    });
    // eslint-disable-next-line react-hooks/exhaustive-deps -- keyed on the keys
  }, [wantPanelKey, panelKey, changesDirty]);
  /** Runs `fn` once an unsaved edit (if any) may be dropped. */
  const afterDrop = (fn: () => void) => {
    if (!changesDirty) return fn();
    void confirmDiscard().then((ok) => ok && fn());
  };

  // Probe the CLI of every tool a lane uses — fresh on the server, so a CLI
  // installed since the page loaded clears its missing-binary banner. Claude is
  // always probed: the console's no-lane state runs it.
  const laneToolsKey = Array.from(new Set(["claude", ...lanes.map((l) => l.tool || "claude")]))
    .sort()
    .join(",");
  useEffect(() => {
    const tools = laneToolsKey.split(",");
    Promise.all(tools.map((tool) => api.run.binary(tool)))
      .then((found) =>
        setBinaryStatus(Object.fromEntries(tools.map((tool, i) => [tool, found[i]!])))
      )
      // Fetch failure (server unreachable, proxy misrouted, etc.) isn't proof
      // a CLI is missing from PATH — leave the probe unresolved rather than
      // showing a misleading "binary missing" banner for an unrelated fault.
      .catch(() => undefined);
  }, [laneToolsKey]);

  useEffect(() => {
    api.lanes
      .pipelines()
      .then((r) => setPipelineTemplates(r.pipelines))
      .catch(() => undefined);
    api.run
      .cwds()
      .then((r) => setCwdSuggestions(r.items))
      .catch(() => undefined);
  }, []);

  // Goes through `keepIfSame`: this fires every 5 s below, and a
  // fresh-but-identical payload would otherwise re-render the lane strip, the
  // lane card and the whole console area on every tick for nothing.
  const refreshList = useCallback(() => {
    api.run
      .list()
      .then((r) => setActiveRuns(keepIfSame(r)))
      .catch(() => undefined);
  }, []);

  // The sidebar's live panes follow this page's poll: a tab in slots 1–3
  // moves no lane column, so the sidebar would not re-read on its own.
  useEffect(() => {
    if (activeRuns)
      window.dispatchEvent(new CustomEvent(LIVE_RUNS_EVENT, { detail: activeRuns.items }));
  }, [activeRuns]);

  // Background poll so the run list and history reflect external changes
  // (server-boot reconciliation, sibling tabs, direct DB edits) even when
  // no WS event fires. Lighter than typical WS gaps; aggressive enough that
  // status flips appear within seconds without needing a manual refresh.
  useEffect(() => {
    refreshList();
    const tick = setInterval(() => {
      // Hidden tab: skip; the visibility handler below re-reads on show.
      if (document.visibilityState === "visible") refreshList();
    }, 5000);
    return () => clearInterval(tick);
  }, [refreshList]);

  // Refresh whenever the tab regains focus / visibility - typical when the
  // user comes back from running `claude` in a terminal and wants to see the
  // current state of every run without waiting for the next poll.
  useEffect(() => {
    const onFocus = () => refreshList();
    const onVis = () => {
      if (document.visibilityState === "visible") refreshList();
    };
    window.addEventListener("focus", onFocus);
    document.addEventListener("visibilitychange", onVis);
    return () => {
      window.removeEventListener("focus", onFocus);
      document.removeEventListener("visibilitychange", onVis);
    };
  }, [refreshList]);

  const currentLane = selectedLaneId !== null ? lanes.find((l) => l.id === selectedLaneId) : null;
  // Only claude lanes carry a pipeline (codex and antigravity emit no hooks),
  // and only while a template is installed — none ships, so it is dormant.
  const noPipeline =
    !!currentLane && (currentLane.tool !== "claude" || currentLane.pipeline_nodes.length === 0);

  // Feature list follows the selected lane, resets the viewer on lane switch.
  useEffect(() => {
    setViewedFeatureSlug(null);
    setViewedFeature(null);
    if (currentLane === null || currentLane === undefined) {
      setFeatures([]);
      return;
    }
    api.lanes.features
      .list(currentLane.id)
      .then((data) => setFeatures(data.features))
      .catch(() => setFeatures([]));
  }, [currentLane?.id]);

  // Fetch the archived snapshot when the picker selects one — read-only, never
  // touches the live lane.
  useEffect(() => {
    if (!currentLane || !viewedFeatureSlug) {
      setViewedFeature(null);
      return;
    }
    let cancelled = false;
    api.lanes.features
      .show(currentLane.id, viewedFeatureSlug)
      .then((data) => {
        if (!cancelled) setViewedFeature(data.feature);
      })
      .catch(() => {
        if (!cancelled) setViewedFeature(null);
      });
    return () => {
      cancelled = true;
    };
  }, [currentLane?.id, viewedFeatureSlug]);

  // Proof gallery follows the selected lane.
  useEffect(() => {
    if (!currentLane) {
      setProofFeatures([]);
      return;
    }
    api.lanes.proof
      .list(currentLane.id)
      .then((data) => setProofFeatures(data.features))
      .catch(() => setProofFeatures([]));
  }, [currentLane?.id, viewedFeatureSlug]);

  // Resolve the active feature slug: either the user-selected one, or the lane's active_feature_id
  const activeFeatureSlug =
    viewedFeatureSlug ??
    (currentLane?.active_feature_id
      ? features.find((f) => f.id === currentLane?.active_feature_id)?.slug
      : null);
  const proofFeature = activeFeatureSlug
    ? proofFeatures.find((f) => f.slug === activeFeatureSlug)
    : null;

  // 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. A full-width Changes panel
  // hides that form anyway, and without a locked height it shrinks to its
  // content — the editor inside it collapsed to a few lines (no live run).
  // A workspace opens on its HOME (WorkspaceHome); `?run=` opens a session —
  // the console, panes and Changes panel, which the home only hides (CSS), so
  // a live terminal never unmounts behind it.
  const home = !!currentLane && !runParam && !sessionParam;
  const replaying = !!currentLane && !!sessionParam;
  // The session the Analyst button opens (`/sessions/:id`): the replayed one,
  // or the one the opened pane holds.
  const analystSessionId = sessionParam ?? openedRun?.sessionId ?? null;
  // The session view (console or replay) fills the page edge to edge, like an
  // editor: no page padding, no cards, dividers between its regions.
  const sessionView = !!currentLane && !home;
  const viewportLocked =
    sessionView || (!home && (paneHasActiveRun || (!!currentLane && changesOpen && changesFull)));

  const handleLaneAction = async (id: number, action: string, body?: Record<string, unknown>) => {
    setLaneActionError(null);
    try {
      if (action === "reset" || action === "remove" || action === "purge") {
        await api.lanes.action(id, action, {
          confirm: true,
          expect: body?.expect,
          ...(body?.force === true ? { force: true } : {}),
        });
      } else {
        await api.lanes.action(id, action, body);
      }
      if (action === "remove") await refreshLanes();
    } catch (err) {
      setLaneActionError(err instanceof Error ? err.message : tLanes("actionErrorUnknown"));
    }
  };

  // Mirrors `agenthub lanes pipeline <template> <id>`: same PATCH, same
  // stage-mismatch warning when the current declared stage matches no node
  // in the newly chosen template.
  const handlePipelineChange = async (id: number, pipeline: string) => {
    setLaneActionError(null);
    try {
      const { lane } = await api.lanes.update(id, { pipeline });
      await refreshLanes();
      // `stage` defaults to the DB sentinel "idle" until a driving session ever
      // calls `agenthub stage` — that's the normal state for most lanes and never
      // matches a real pipeline node, so it isn't a mismatch worth surfacing.
      if (lane.stage !== "idle" && !lane.pipeline_nodes.some((n) => n.state === "current")) {
        setLaneActionError(
          tLanes("pipelinePicker.stageMismatch", {
            stage: lane.stage,
            pipeline: lane.pipeline,
            nodes: lane.pipeline_nodes.map((n) => n.id).join(", "),
          })
        );
      }
    } catch (err) {
      setLaneActionError(err instanceof Error ? err.message : tLanes("actionErrorUnknown"));
    }
  };

  return (
    <div
      className={
        sessionView
          ? // Cancels Layout's page padding; the 1.5rem left is the status bar's,
            // plus the drawer's 2.75rem menu bar below `md` (issue #61).
            "-m-5 flex h-[calc(100vh-1.5rem)] flex-col max-md:h-[calc(100vh-4.25rem)] lg:-m-6"
          : viewportLocked
            ? "h-[calc(100vh-4rem)] max-md:h-[calc(100vh-6.75rem)] lg:h-[calc(100vh-4.5rem)] flex flex-col gap-5"
            : "space-y-5"
      }
    >
      {/* Workspaces are picked in the sidebar's project tree; this page shows
          the selected one. With none at all, one banner offers to create it. */}
      <div className="flex min-h-0 flex-1 flex-col gap-4">
        {lanesLoaded && lanes.length === 0 && (
          /* With no lanes the strip was a dashed tile beside a stray sentence,
             which reads as a half-rendered row rather than a state. One banner
             instead — and a compact one on purpose: the run setup form below
             is what the user actually needs the height for. */
          <button
            type="button"
            data-testid="lane-empty"
            onClick={() => setAddLaneOpen(true)}
            className="card flex w-full shrink-0 flex-wrap items-center gap-4 border-dashed px-5 py-4 text-left transition-colors hover:border-accent/50 hover:bg-surface-2"
          >
            <span className="flex h-10 w-10 shrink-0 items-center justify-center rounded-xl bg-surface-4 text-fg-muted">
              <Layers className="h-5 w-5" />
            </span>
            <div className="min-w-0 flex-1">
              <span className="block text-sm font-medium text-fg-primary">
                {tLanes("empty.title")}
              </span>
              <p className="mt-0.5 text-xs text-fg-muted">
                {tLanes("empty.body")}{" "}
                <code className="rounded bg-surface-2 px-1.5 py-0.5 text-[11px] text-fg-secondary">
                  agenthub workspace add --cwd $(pwd)
                </code>
              </p>
            </div>
            <span className="flex shrink-0 items-center gap-1.5 text-xs font-medium text-accent">
              <Plus className="h-4 w-4" />
              {tLanes("add")}
            </span>
          </button>
        )}

        {/* The selected lane's pipeline — the thing you actually come to this
            page to read, beside the list rather than stacked under it.
            The section itself is ALWAYS rendered, even with no lane selected:
            `ConsoleArea` lives inside it, and a conditional wrapper would give
            the console two render sites, so every flip of `currentLane` (lanes
            arriving on mount, a lane removed, a refetch re-picking the
            selection) unmounted the terminal and wiped a half-typed prompt.
            Same rule as RunConsole's own collapse — hide with CSS, never by
            unmounting. */}
        {/* Detail and the Changes panel share one row: the panel is a reading
            surface for the same lane the console is driving, so it sits beside
            it rather than under it. It collapses to a rail instead of
            unmounting nothing — there is no live subscription inside it, so
            unmounting is safe and keeps a closed panel from polling. */}
        {home && currentLane && (
          <WorkspaceHome
            lane={currentLane}
            onRenamed={() => void refreshLanes()}
            onMenuAction={(action) => {
              if (action === "new-here") {
                setAddLanePrefill({ sourceRepo: currentLane.source_repo || currentLane.cwd });
                setAddLaneOpen(true);
              } else if (action === "reset" || action === "remove") {
                setDestructive({ lane: currentLane, action });
              }
            }}
          />
        )}
        <div ref={changesRowRef} className={`relative flex min-h-0 flex-1${home ? " hidden" : ""}`}>
          <section
            data-testid="lane-detail"
            className={`flex min-h-0 min-w-0 flex-1 flex-col${
              currentLane && changesOpen && changesFull ? " hidden" : ""
            }`}
          >
            {/* No header row: the console's tab bar is the header. Only a
              workspace with a pipeline template (dormant: none ships) keeps
              its time-at-stage, pipeline and feature pickers here. */}
            {currentLane && !noPipeline && (
              <div className="mb-3 flex flex-wrap items-center gap-2">
                <span className="shrink-0 tabular-nums text-xs text-fg-muted">
                  {since(currentLane.stage_seconds)}
                </span>
                <select
                  data-testid="pipeline-picker"
                  aria-label={tLanes("pipelinePicker.label")}
                  className="select !w-auto !rounded !py-0.5 !pl-2 !pr-6 !text-xs text-fg-secondary"
                  value={currentLane.pipeline}
                  disabled={!!viewedFeature}
                  title={
                    viewedFeature
                      ? tLanes("features.viewingArchived", { slug: viewedFeature.slug })
                      : undefined
                  }
                  onChange={(e) => void handlePipelineChange(currentLane.id, e.target.value)}
                >
                  {(pipelineTemplates.length
                    ? pipelineTemplates
                    : [
                        {
                          id: currentLane.pipeline,
                          name: currentLane.pipeline_name,
                          nodes: [],
                        },
                      ]
                  ).map((p) => (
                    <option key={p.id} value={p.id}>
                      {p.nodes.length ? `${p.name} (${p.nodes.length})` : p.name}
                    </option>
                  ))}
                </select>
                {/* No stage chip and no "auto: <stage>" chip here: the
                        PipelineMap right below this header already draws both
                        — the declared node as the current ring, the detected
                        one as its amber badge — so the chips were a second,
                        smaller copy of the same two facts. */}
                {features.length > 0 && (
                  <select
                    data-testid="feature-picker"
                    className="select !w-auto !rounded !py-0.5 !pl-2 !pr-6 !text-xs"
                    value={viewedFeatureSlug ?? ""}
                    onChange={(e) => setViewedFeatureSlug(e.target.value || null)}
                  >
                    <option value="">{tLanes("features.live")}</option>
                    {features.map((f) => (
                      <option key={f.slug} value={f.slug}>
                        {f.slug}
                        {f.archived_at ? ` (${tLanes("features.archived")})` : ""}
                      </option>
                    ))}
                  </select>
                )}
              </div>
            )}
            {currentLane && (
              <div className="max-h-[45vh] shrink-0 overflow-y-auto px-3">
                {/* No margin when the card rendered nothing (see LaneCard). */}
                <div className="mb-3 has-[>div:empty]:mb-0">
                  <LaneCard
                    lane={currentLane}
                    onAction={(a, b) => handleLaneAction(currentLane.id, a, b)}
                    childWorktrees={lanes.filter(
                      (l) => l.source_repo === currentLane.cwd && l.id !== currentLane.id
                    )}
                    onSelectLane={setSelectedLaneId}
                  />
                </div>
                {!noPipeline && (
                  <div className="mb-3">
                    <PipelineMap
                      nodes={
                        viewedFeature ? viewedFeature.pipeline_nodes : currentLane.pipeline_nodes
                      }
                      detectedSignal={viewedFeature ? undefined : currentLane.detected_signal}
                    />
                    {viewedFeature && (
                      <p data-testid="feature-viewer-banner" className="mb-2 text-xs text-fg-muted">
                        {tLanes("features.viewingArchived", { slug: viewedFeature.slug })}
                      </p>
                    )}
                  </div>
                )}
                {proofFeature &&
                  (Object.keys(proofFeature.groups).length > 0 || proofFeature.ticket_report) && (
                    <div data-testid="proof-gallery" className="mt-2">
                      {proofFeature.ticket_report && (
                        <a
                          href={`/api/lanes/${currentLane.id}/proof/${proofFeature.ticket_report}`}
                          target="_blank"
                          rel="noreferrer"
                          className="text-xs text-fg-muted"
                        >
                          {tLanes("proof.ticketReport")}
                        </a>
                      )}
                      {Object.entries(proofFeature.groups).map(([group, images]) => (
                        <div key={group} className="mt-1">
                          <span className="text-xs text-fg-muted">
                            {group} · {images.length}
                          </span>
                          <div className="flex flex-wrap gap-1">
                            {images.slice(0, 8).map((img) => (
                              <img
                                key={img}
                                loading="lazy"
                                className="h-16 w-16 rounded object-cover"
                                src={api.lanes.proof.imageUrl(
                                  currentLane.id,
                                  proofFeature.slug,
                                  group,
                                  img
                                )}
                                alt={img}
                              />
                            ))}
                            {images.length > 8 && (
                              <span className="text-xs text-fg-muted">+{images.length - 8}</span>
                            )}
                          </div>
                        </div>
                      ))}
                    </div>
                  )}
              </div>
            )}
            <div className="flex min-h-0 flex-1 flex-col">
              {replaying && (
                <div className="flex min-h-0 flex-1 flex-col px-4 pb-3 pt-3">
                  <SessionReplay
                    lane={currentLane}
                    sessionId={sessionParam}
                    liveRuns={activeRuns?.items ?? []}
                    onResumed={(runId, laneId) =>
                      setSearchParams({ lane: String(laneId ?? currentLane.id), run: runId })
                    }
                  />
                </div>
              )}
              {/* A replay only HIDES the console: it has one render site and a
                live terminal must never unmount. */}
              <div className={replaying ? "hidden" : "contents"}>
                <ConsoleArea
                  lanes={lanes}
                  selectedLaneId={selectedLaneId}
                  binaryStatus={binaryStatus}
                  activeRuns={activeRuns}
                  onHasActiveRunChange={setPaneHasActiveRun}
                  attachRequest={attachRequest}
                  onNewSession={
                    currentLane
                      ? () => setSearchParams({ lane: String(currentLane.id) })
                      : undefined
                  }
                  onOpenRun={(runId, opts) =>
                    currentLane &&
                    setSearchParams(
                      { lane: String(currentLane.id), run: runId },
                      {
                        // Following the focus, or a tab click, is not a new
                        // history entry.
                        replace: opts?.focusOnly || opts?.replace,
                        state: opts?.split
                          ? { split: true }
                          : opts?.focusOnly
                            ? { focusOnly: true }
                            : undefined,
                      }
                    )
                  }
                  onRunsChanged={refreshList}
                />
              </div>
            </div>
          </section>

          {currentLane && changesOpen && !changesFull && (
            // Drag (or arrow keys) to any width; the button keeps its presets.
            <Divider
              gridRef={changesRowRef}
              dir="row"
              at={1 - Math.max(changesRatio(changesSize), minChanges)}
              box={{ x: 0, y: 0, w: 1, h: 1 }}
              label={tLanes("changes.splitter")}
              onRatio={(r) => setChangesSize(clampChanges(Math.max(1 - r, minChanges)))}
            />
          )}
          {currentLane &&
            (changesOpen ? (
              <aside
                id="lane-changes-panel"
                data-testid="lane-changes-card"
                aria-label={tLanes("changes.title")}
                style={
                  typeof changesSize === "number" ? { width: `${changesSize * 100}%` } : undefined
                }
                className={`flex shrink-0 flex-col bg-surface-1 ${
                  typeof changesSize === "number" ? "" : CHANGES_WIDTH[changesSize]
                }${changesFull ? "" : " min-w-[18rem] border-l border-border"}`}
              >
                {/* Header: the title, Analyst, then the resize control — the
                    same height as the console's tab bar, so the two read as
                    one header strip. Files and Changes are ONE panel now; its
                    own mode switcher moves between them. */}
                <div
                  className="flex h-10 shrink-0 items-center gap-1 border-b border-border px-2"
                  role="toolbar"
                >
                  <span className="px-1 text-xs font-medium text-fg-secondary">
                    {tLanes("panel.changes")}
                  </span>
                  {/* The opened session's analysis page — a page of its own. */}
                  <button
                    type="button"
                    data-testid="panel-analyst"
                    disabled={!analystSessionId}
                    onClick={() =>
                      analystSessionId &&
                      navigate(`/sessions/${encodeURIComponent(analystSessionId)}`)
                    }
                    title={tLanes("panel.analyst")}
                    aria-label={tLanes("panel.analyst")}
                    className="flex h-7 w-7 items-center justify-center rounded-md text-fg-muted transition-colors hover:bg-surface-4 hover:text-fg-primary disabled:opacity-40 disabled:hover:bg-transparent"
                  >
                    <ChartColumn className="h-4 w-4" />
                  </button>
                  <button
                    type="button"
                    data-testid="lane-changes-resize"
                    onClick={() => {
                      // Past the widest step the next state is "gone", which
                      // is what the rail button reopens at `compact` — and
                      // what drops an unsaved edit, so that asks first.
                      if (changesFull) {
                        afterDrop(() => {
                          setChangesOpen(false);
                          setChangesSize("compact");
                        });
                      } else {
                        setChangesSize(nextChangesSize);
                      }
                    }}
                    // The control names the same region the rail button does,
                    // so a screen reader reads one panel that is open or
                    // closed rather than two unrelated buttons.
                    aria-expanded
                    aria-controls="lane-changes-panel"
                    aria-label={changesNextLabel}
                    title={changesNextLabel}
                    className="ml-auto flex h-6 w-6 items-center justify-center rounded-md text-fg-muted transition-colors hover:bg-surface-4 hover:text-fg-primary"
                  >
                    {/* Icon-only, and it draws the width the click LANDS on,
                        not the current one — the label the tooltip carries. */}
                    {(() => {
                      const Next = CHANGES_NEXT_ICON[changesPreset];
                      return <Next className="h-4 w-4" />;
                    })()}
                  </button>
                </div>
                <div className="flex min-h-0 flex-1 flex-col px-3 pt-2">
                  {panelAt && (
                    <LaneChangesPanel
                      // A new tree is a new panel: no read for the previous one
                      // can land in it. `panelAt` holds still while an edit is
                      // unsaved (see above).
                      key={panelKey}
                      laneId={panelAt.laneId}
                      session={panelAt.session}
                      full={changesFull}
                      wide={changesPreset !== "compact"}
                      onDirtyChange={setChangesDirty}
                      // A sibling worktree forks from the lane's SOURCE repo when
                      // it has one (this lane is itself a worktree of it); an
                      // adopted lane is its own repo.
                      onNewLane={(branch) => {
                        setAddLanePrefill({
                          sourceRepo: currentLane.source_repo || currentLane.cwd,
                          branch,
                        });
                        setAddLaneOpen(true);
                      }}
                    />
                  )}
                </div>
              </aside>
            ) : (
              // The rail also carries the uncommitted counts, vertical, with
              // the per-file list on hover — a sibling of the expand button,
              // since a button may not hold another.
              <div className="flex w-9 shrink-0 flex-col items-center gap-3 border-l border-border bg-surface-1 py-3">
                <button
                  type="button"
                  data-testid="lane-changes-expand"
                  onClick={() => setChangesOpen(true)}
                  aria-expanded={false}
                  aria-controls="lane-changes-panel"
                  aria-label={tLanes("changes.expand")}
                  title={tLanes("changes.expand")}
                  className="flex flex-col items-center gap-2 text-fg-muted transition-colors hover:text-fg-primary"
                >
                  <PanelLeftClose className="h-4 w-4" />
                  <span className="text-[10px] uppercase tracking-wide [writing-mode:vertical-rl]">
                    {tLanes("changes.title")}
                  </span>
                </button>
                {panelAt && (
                  <LaneGitRailCounts
                    laneId={panelAt.laneId}
                    session={panelAt.session}
                    onShowAll={() => setChangesOpen(true)}
                  />
                )}
              </div>
            ))}
        </div>
      </div>

      <AddLaneModal
        open={addLaneOpen}
        cwdSuggestions={cwdSuggestions}
        prefill={addLanePrefill}
        onClose={() => {
          setAddLaneOpen(false);
          setAddLanePrefill(null);
        }}
        onAdded={(lane) => {
          void refreshLanes();
          setSelectedLaneId(lane.id);
        }}
      />

      {destructive && (
        <DestructiveLaneModal
          lane={destructive.lane}
          action={destructive.action}
          open
          onClose={() => setDestructive(null)}
          onConfirm={async (body) => {
            const { lane, action } = destructive;
            setDestructive(null);
            setLaneActionError(null);
            try {
              await api.lanes.action(lane.id, action, {
                confirm: true,
                expect: body.expect,
                ...(body.force === true ? { force: true } : {}),
              });
              await refreshLanes();
              if (action === "remove") setSearchParams({});
            } catch (err) {
              setLaneActionError(err instanceof Error ? err.message : String(err));
            }
          }}
        />
      )}
    </div>
  );
}