Fix composer focus when selecting channels and DMs

src/bundled/channels/ChannelsPage.tsx

@@ -1004,6 +1004,9 @@ function ChannelWorkspace({
                     scope={scope}
                     channelId={current.id}
                     channelName={current.name}
+                    autoFocus={
+                      !current.readOnly && !requestedMessage && !requestedThread
+                    }
                     onOpenLink={openLink}
                     canOpenLink={canOpenLink}
                     label={

src/features/messages/MessageComposer.test.tsx

@@ -379,6 +379,64 @@ function mount(
   };
 }
 
+it("autofocuses each selected conversation once without stealing focus on updates", () => {
+  const h = mount({ autoFocus: true });
+  expect(h.input()).toHaveFocus();
+  const other = document.createElement("button");
+  document.body.append(other);
+  try {
+    other.focus();
+    h.retarget({ channelName: "Renamed", autoFocus: false });
+    h.retarget({ autoFocus: true });
+    expect(other).toHaveFocus();
+    h.retarget({ channelId: "another-channel" });
+    expect(h.input()).toHaveFocus();
+    h.retarget({ channelId: "keyboard-navigation" });
+    expect(h.input()).toHaveFocus();
+  } finally {
+    other.remove();
+  }
+});
+
+it("lets an explicit focus restoration in the mount commit win", () => {
+  const h = mount();
+  h.unmount();
+  const target = document.createElement("button");
+  document.body.append(target);
+  function RestoreFocus() {
+    useLayoutEffect(() => target.focus(), []);
+    return null;
+  }
+  try {
+    render(
+      <>
+        <MessageComposer
+          session={h.session}
+          scope="scope"
+          channelId="channel"
+          channelName="General"
+          autoFocus
+        />
+        <RestoreFocus />
+      </>,
+    );
+    expect(target).toHaveFocus();
+  } finally {
+    target.remove();
+  }
+});
+
+it("leaves focus alone unless an enabled composer opts into mount focus", () => {
+  const h = mount();
+  expect(h.input()).not.toHaveFocus();
+  h.retarget({
+    channelId: "disabled-channel",
+    disabled: true,
+    autoFocus: true,
+  });
+  expect(h.input()).not.toHaveFocus();
+});
+
 it("keeps unpublished completions invisible but lets Escape revoke pending work", () => {
   const h = mount();
   const input = h.input();

src/features/messages/MessageComposer.tsx

@@ -92,6 +92,8 @@ export type MessageComposerProps = {
   replyContext?: ReactNode;
   mediaTimeSeconds?: number;
   clearMediaTime?(): void;
+  /** Focus once when this conversation mounts, not when overlays close. */
+  autoFocus?: boolean;
   focusRequest?: number;
   hideMediaTimeIndicator?: boolean;
   disabled?: boolean;
@@ -138,6 +140,7 @@ function Composer({
   replyContext,
   mediaTimeSeconds,
   clearMediaTime,
+  autoFocus = false,
   focusRequest,
   hideMediaTimeIndicator = false,
   disabled: requestedDisabled = false,
@@ -202,6 +205,27 @@ function Composer({
   const valueRef = useRef(value);
   const caret = useRef<number | undefined>(undefined);
   const input = useRef<ComposerInputElement>(null);
+  const focusOnMount = useRef(
+    autoFocus && !disabled && typeof document !== "undefined"
+      ? document.activeElement
+      : undefined,
+  );
+  useEffect(() => {
+    // A navigation/dialog owner may restore focus during this commit. Let that
+    // explicit handoff win over the conversation's default initial focus.
+    const previous = focusOnMount.current;
+    if (
+      previous &&
+      (previous === document.activeElement ||
+        (!previous.isConnected && document.activeElement === document.body))
+    ) {
+      const editor = input.current;
+      if (!editor) return;
+      const end = editor.value.length;
+      editor.setSelectionRange(end, end);
+      editor.focus();
+    }
+  }, []);
   const nonmembers = useNonmemberMentions(session, channelId, () =>
     input.current?.focus(),
   );

tests/browser/composer-focus.spec.mjs

@@ -0,0 +1,41 @@
+import { test, expect } from "./fixture.mjs";
+import { open } from "./timeline.mjs";
+
+test.use({ productionBroker: true, dmLabels: true });
+
+// Browser boundary: real sidebar navigation must hand focus to the mounted
+// ProseMirror editor, including after a warm return; typing must need no click.
+test("selecting a channel or DM focuses its composer and retains drafts", async ({
+  page,
+  app,
+}) => {
+  await open(page, app);
+  const sidebar = page.getByRole("navigation", { name: "Subscribed channels" });
+  const conversation = page.getByRole("article", { name: "Conversation" });
+  const input = conversation.getByRole("textbox");
+  for (const [index, name] of [
+    "Beta",
+    "Alice Fixture",
+    "Beta",
+    "Alice Fixture",
+  ].entries()) {
+    await sidebar.getByRole("button", { name, exact: true }).click();
+    await expect(input).toBeFocused();
+    if (index < 2) {
+      await page.keyboard.type(`Draft for ${name}`);
+      await expect(input).toHaveText(`Draft for ${name}`);
+    } else {
+      await expect(input).toHaveText(`Draft for ${name}`);
+      await page.keyboard.type(" continued");
+      await expect(input).toHaveText(`Draft for ${name} continued`);
+    }
+  }
+  const settings = page.getByRole("button", {
+    name: "Channel settings",
+    exact: true,
+  });
+  await settings.click();
+  await expect(
+    page.getByRole("button", { name: "Close channel settings" }),
+  ).toBeFocused();
+});