diff --git a/app/src/features/crews/Sidebar.tsx b/app/src/features/crews/Sidebar.tsx
index c5a8535..711cc81 100644
--- a/app/src/features/crews/Sidebar.tsx
+++ b/app/src/features/crews/Sidebar.tsx
@@ -24,6 +24,7 @@ import { useCrewActions } from "./crewActions";
 import { moveBy, orderedCrews, setCrewOrder, useCrewOrder } from "./crewOrder";
 import { Conversation } from "./SidebarConversation";
 import { row } from "./SidebarPages";
+import { SidebarResizer } from "./SidebarResizer";
 import { StateFilters } from "./StateFilters";
 import { filteredBots, useStateFilter } from "./stateFilter";
 import { useCrewDrag } from "./useCrewDrag";
@@ -43,7 +44,8 @@ export function Sidebar() {
   const allFolded = crews.length > 0 && crews.every((crew) => collapsed.has(crew.id));
   const [creating, setCreating] = useState(false);
   return (
-    <div className="flex w-72 shrink-0 flex-col border-line border-r bg-panel">
+    <div className="relative flex w-[var(--sidebar-width,18rem)] shrink-0 flex-col border-line border-r bg-panel">
+      <SidebarResizer />
       <nav aria-label={words.label} className="flex min-h-0 flex-1 flex-col">
         <div className="flex h-10 shrink-0 items-center gap-0.5 pr-1.5 pl-2">
           <h2 className="min-w-0 flex-1">
diff --git a/app/src/features/crews/SidebarResizer.tsx b/app/src/features/crews/SidebarResizer.tsx
new file mode 100644
index 0000000..b78b2c5
--- /dev/null
+++ b/app/src/features/crews/SidebarResizer.tsx
@@ -0,0 +1,77 @@
+import { type KeyboardEvent, type PointerEvent, useRef } from "react";
+import { useT } from "../../i18n";
+import {
+  SIDEBAR_MAX_PX,
+  SIDEBAR_MIN_PX,
+  sidebarWidth,
+  useSidebarWidth,
+} from "../../shell/sidebarWidth";
+
+const KEY_STEP_PX = 24;
+
+/**
+ * The right edge of the crews list: drag it, or use the arrow keys, to make
+ * the list wider or narrower; double click goes back to the usual width. The
+ * parent is `relative`.
+ */
+export function SidebarResizer() {
+  const t = useT();
+  const width = useSidebarWidth();
+  const drag = useRef<{ x: number; width: number; scale: number } | null>(null);
+
+  const start = (event: PointerEvent<HTMLDivElement>) => {
+    const list = event.currentTarget.parentElement;
+    if (!list) {
+      return;
+    }
+    event.currentTarget.setPointerCapture(event.pointerId);
+    // The window may be drawn larger than its layout units (zoom).
+    const scale = list.offsetWidth ? list.getBoundingClientRect().width / list.offsetWidth : 1;
+    drag.current = { x: event.clientX, width: sidebarWidth.get(), scale: scale || 1 };
+  };
+  const move = (event: PointerEvent<HTMLDivElement>) => {
+    const from = drag.current;
+    if (from) {
+      sidebarWidth.set(from.width + (event.clientX - from.x) / from.scale);
+    }
+  };
+  const end = () => {
+    if (drag.current) {
+      drag.current = null;
+      sidebarWidth.set(sidebarWidth.get(), true);
+    }
+  };
+  const onKey = (event: KeyboardEvent<HTMLDivElement>) => {
+    const step = event.shiftKey ? KEY_STEP_PX * 4 : KEY_STEP_PX;
+    if (event.key === "ArrowRight") {
+      sidebarWidth.set(sidebarWidth.get() + step, true);
+    } else if (event.key === "ArrowLeft") {
+      sidebarWidth.set(sidebarWidth.get() - step, true);
+    } else {
+      return;
+    }
+    event.preventDefault();
+  };
+
+  return (
+    // biome-ignore lint/a11y/useSemanticElements: a separator that can be dragged and focused is a widget, not an <hr>
+    <div
+      role="separator"
+      aria-orientation="vertical"
+      aria-label={t.common.resize}
+      aria-valuemin={SIDEBAR_MIN_PX}
+      aria-valuemax={SIDEBAR_MAX_PX}
+      aria-valuenow={width}
+      tabIndex={0}
+      onPointerDown={start}
+      onPointerMove={move}
+      onPointerUp={end}
+      onPointerCancel={end}
+      onDoubleClick={() => sidebarWidth.reset()}
+      onKeyDown={onKey}
+      className="group absolute inset-y-0 -right-1 z-30 w-2 cursor-col-resize touch-none focus-visible:outline-none"
+    >
+      <span className="absolute inset-y-0 right-[3px] w-0.5 bg-transparent transition-colors group-hover:bg-line-strong group-focus-visible:bg-work group-active:bg-work" />
+    </div>
+  );
+}
diff --git a/app/src/features/crews/sidebarWidth.test.tsx b/app/src/features/crews/sidebarWidth.test.tsx
new file mode 100644
index 0000000..2714905
--- /dev/null
+++ b/app/src/features/crews/sidebarWidth.test.tsx
@@ -0,0 +1,42 @@
+import { cleanup, fireEvent, screen } from "@testing-library/react";
+import { afterEach, describe, expect, test } from "vitest";
+import { FakeBotloft } from "../../lib/fake";
+import { SIDEBAR_DEFAULT_PX, SIDEBAR_MAX_PX, sidebarWidth } from "../../shell/sidebarWidth";
+import { crewOpened, renderApp } from "../../test/app";
+
+afterEach(() => {
+  cleanup();
+  sidebarWidth.reset();
+});
+
+const rootWidth = () => document.documentElement.style.getPropertyValue("--sidebar-width");
+
+describe("the width of the crews list", () => {
+  test("the arrow keys widen and narrow it, and a double click goes back", async () => {
+    const fake = new FakeBotloft();
+    fake.addCrew("Ops");
+    renderApp(fake);
+    await crewOpened("Ops");
+
+    const handle = screen.getByRole("separator", { name: "Resize panel" });
+    expect(handle.getAttribute("aria-valuenow")).toBe(String(SIDEBAR_DEFAULT_PX));
+
+    fireEvent.keyDown(handle, { key: "ArrowRight" });
+    expect(handle.getAttribute("aria-valuenow")).toBe(String(SIDEBAR_DEFAULT_PX + 24));
+    expect(rootWidth()).toBe(`${SIDEBAR_DEFAULT_PX + 24}px`);
+    expect(localStorage.getItem("botloft.panel.sidebar")).toBe(String(SIDEBAR_DEFAULT_PX + 24));
+
+    fireEvent.keyDown(handle, { key: "ArrowLeft" });
+    expect(handle.getAttribute("aria-valuenow")).toBe(String(SIDEBAR_DEFAULT_PX));
+
+    fireEvent.doubleClick(handle);
+    expect(handle.getAttribute("aria-valuenow")).toBe(String(SIDEBAR_DEFAULT_PX));
+  });
+
+  test("it never goes past its limits", () => {
+    sidebarWidth.set(5000, true);
+    expect(sidebarWidth.get()).toBe(SIDEBAR_MAX_PX);
+    sidebarWidth.set(10, true);
+    expect(sidebarWidth.get()).toBeGreaterThanOrEqual(200);
+  });
+});
diff --git a/app/src/shell/sidebarWidth.ts b/app/src/shell/sidebarWidth.ts
new file mode 100644
index 0000000..6d74cd3
--- /dev/null
+++ b/app/src/shell/sidebarWidth.ts
@@ -0,0 +1,65 @@
+// How wide the crews list on the left is: the owner drags its right edge
+// (features/crews/SidebarResizer.tsx). The width lives in a CSS variable on
+// the root, so dragging only changes a style and the list, the slot that
+// holds it and the chat all follow. It is remembered like the width of the
+// panels on the right (ui/SidePanel.tsx).
+
+import { useSyncExternalStore } from "react";
+
+export const SIDEBAR_DEFAULT_PX = 288;
+export const SIDEBAR_MIN_PX = 224;
+export const SIDEBAR_MAX_PX = 560;
+
+const KEY = "botloft.panel.sidebar";
+const listeners = new Set<() => void>();
+
+const clamp = (width: number) =>
+  Math.round(Math.min(SIDEBAR_MAX_PX, Math.max(SIDEBAR_MIN_PX, width)));
+
+function read(): number {
+  try {
+    const value = Number(localStorage.getItem(KEY));
+    return Number.isFinite(value) && value > 0 ? clamp(value) : SIDEBAR_DEFAULT_PX;
+  } catch {
+    return SIDEBAR_DEFAULT_PX;
+  }
+}
+
+let width = read();
+
+function apply(): void {
+  if (typeof document !== "undefined") {
+    document.documentElement.style.setProperty("--sidebar-width", `${width}px`);
+  }
+}
+apply();
+
+export const sidebarWidth = {
+  get: () => width,
+  /** `keep` also remembers it; while dragging only the screen follows. */
+  set(next: number, keep = false): void {
+    width = clamp(next);
+    apply();
+    if (keep) {
+      try {
+        localStorage.setItem(KEY, String(width));
+      } catch {
+        // A convenience: the width just is not kept.
+      }
+    }
+    for (const listener of listeners) {
+      listener();
+    }
+  },
+  reset(): void {
+    this.set(SIDEBAR_DEFAULT_PX, true);
+  },
+  subscribe(listener: () => void): () => void {
+    listeners.add(listener);
+    return () => listeners.delete(listener);
+  },
+};
+
+export function useSidebarWidth(): number {
+  return useSyncExternalStore(sidebarWidth.subscribe, sidebarWidth.get, sidebarWidth.get);
+}
diff --git a/app/src/sidebar.css b/app/src/sidebar.css
index 656624f..33cf982 100644
--- a/app/src/sidebar.css
+++ b/app/src/sidebar.css
@@ -6,7 +6,7 @@
 
 .sidebar-slot {
   position: relative;
-  width: 18rem;
+  width: var(--sidebar-width, 18rem);
 }
 
 .sidebar-slot[data-open="false"] {