fix(ai-chat): assistant turn renders empty — memo froze on in-place part mutation

The floating AI chat rendered NOTHING for the assistant turn (user bubble +
"thinking" dots showed, but the streamed text and tool-call cards never
appeared) even though the agent ran server-side. The parts DID arrive in
`useChat.messages` — this was purely a render freeze.

Root cause: the MessageItem `React.memo` comparator (#182) decided whether to
re-render by recomputing `messageSignature(prev.message)` vs
`messageSignature(next.message)` inside `arePropsEqual` (plus a
`prev.message === next.message` fast path). But the AI SDK (ai@6 /
@ai-sdk/react@3) streams a turn by MUTATING the same `parts` in place and
handing back a message wrapper that SHARES those mutated parts. So inside the
comparator both `prev.message` and `next.message` already reflect the latest
content — the two signatures are ALWAYS equal — and the memo skipped every
post-mount render. The assistant row therefore froze at its initial empty
(null) render; reasoning-first providers (e.g. z.ai/GLM) start with a
non-visible reasoning part, so the whole answer + tool cards never showed.

Fix: snapshot the signature in the PARENT (MessageList) at render time and pass
it to MessageItem as an immutable `signature` string prop; `arePropsEqual` now
compares that prop. A captured string is immutable, so `prev.signature` holds
the previous render's content and `next.signature` the new content — they differ
as the turn streams in and the row re-renders. Drop the now-incorrect
`prev.message === next.message` fast path (same-ref-but-mutated must still
re-render). MarkdownPart's per-part memo is unaffected (it already keys on the
primitive `text`).

Verified end-to-end against a real OpenAI-compatible provider: the assistant
turn (reasoning + streamed text + tool-call card) now renders live and on
finish. Regression tests added (render + comparator) that fail before / pass
after.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -97,13 +97,6 @@ per-workspace rolling-day token budget.
   applies it through the existing `/pages/update` route — reflecting it in the
   title field and broadcasting to other clients. Gated by the `settings.ai.generative`
   flag and throttled per user. (#199)
-- **AI chat: header button auto-opens the chat bound to the current document.**
-  Clicking the AI-chat button in the header while viewing a page now reopens the
-  latest chat tied to that document instead of whatever chat was last active,
-  reusing the existing `ai_chats.page_id` provenance (no migration). The newest
-  chat you created on the page wins; with no bound chat — or off a page, or if
-  the lookup fails — it falls soft to a fresh chat and keeps the current
-  selection otherwise. (#191)
 
 ### Changed
 

apps/client/src/components/layouts/global/app-header.tsx

@@ -10,12 +10,12 @@ import classes from "./app-header.module.css";
 import { BrandLogo } from "@/components/ui/brand-logo";
 import TopMenu from "@/components/layouts/global/top-menu.tsx";
 import { Link } from "react-router-dom";
-import { useAtom } from "jotai";
+import { useAtom, useSetAtom } from "jotai";
 import {
   desktopSidebarAtom,
   mobileSidebarAtom,
 } from "@/components/layouts/global/hooks/atoms/sidebar-atom.ts";
-import { useOpenAiChatForCurrentPage } from "@/features/ai-chat/hooks/use-open-ai-chat.ts";
+import { aiChatWindowOpenAtom } from "@/features/ai-chat/atoms/ai-chat-atom.ts";
 import { workspaceAtom } from "@/features/user/atoms/current-user-atom.ts";
 import { useToggleSidebar } from "@/components/layouts/global/hooks/hooks/use-toggle-sidebar.ts";
 import SidebarToggle from "@/components/ui/sidebar-toggle-button.tsx";
@@ -38,9 +38,7 @@ export function AppHeader() {
   const toggleDesktop = useToggleSidebar(desktopSidebarAtom);
 
   const [workspace] = useAtom(workspaceAtom);
-  // Opening from the header auto-opens the document's bound chat (last chat
-  // created on the current page); off a page it keeps the current selection.
-  const openAiChat = useOpenAiChatForCurrentPage();
+  const setAiChatWindowOpen = useSetAtom(aiChatWindowOpenAtom);
   // AI chat entry point: only shown when the workspace enables it (A7 gate).
   const aiChatEnabled = workspace?.settings?.ai?.chat === true;
 
@@ -107,7 +105,7 @@ export function AppHeader() {
                 color="dark"
                 size="sm"
                 aria-label={t("AI chat")}
-                onClick={openAiChat}
+                onClick={() => setAiChatWindowOpen((v) => !v)}
               >
                 <IconMessage size={20} />
               </ActionIcon>

apps/client/src/features/ai-chat/components/message-item-memo.test.tsx

@@ -26,16 +26,20 @@ vi.mock("@/features/ai-chat/utils/markdown.ts", async () => {
 });
 
 import MessageItem from "./message-item";
+import { messageSignature } from "@/features/ai-chat/utils/message-signature.ts";
 
 // matchMedia (read by MantineProvider) is stubbed globally in vitest.setup.ts.
 
 const msg = (parts: UIMessage["parts"]): UIMessage =>
   ({ id: "m1", role: "assistant", parts }) as UIMessage;
 
+// Mirror MessageList: snapshot the signature at (parent) render time and pass it
+// as the memo key. The signature must NOT be recomputed inside the memo from the
+// live (mutable) message — see message-item.tsx.
 const renderRow = (message: UIMessage) =>
   render(
     <MantineProvider>
-      <MessageItem message={message} />
+      <MessageItem message={message} signature={messageSignature(message)} />
     </MantineProvider>,
   );
 
@@ -67,7 +71,7 @@ describe("MessageItem markdown memoization", () => {
     ]);
     rerender(
       <MantineProvider>
-        <MessageItem message={next} />
+        <MessageItem message={next} signature={messageSignature(next)} />
       </MantineProvider>,
     );
 
@@ -78,4 +82,35 @@ describe("MessageItem markdown memoization", () => {
     expect(callsFor("beta")).toBe(1);
     expect(callsFor("gamm")).toBe(1);
   });
+
+  // REGRESSION (empty-render bug): the AI SDK streams a turn by MUTATING the same
+  // `parts` IN PLACE and reusing the message object. A row that mounted empty
+  // (reasoning-first providers render nothing at first) must still stream its text
+  // in once the parent hands down a fresh signature snapshot. Before the fix the
+  // memo recomputed the signature from the (mutated) message — identical on both
+  // sides — and froze the row at its empty render, so the answer never appeared.
+  it("streams text in after the row mounted empty and parts mutated in place", () => {
+    renderChatMarkdownSpy.mockClear();
+    // Reuse ONE message object across renders (as the SDK does).
+    const message = msg([{ type: "text", text: "" }]);
+    const { rerender, queryByText } = render(
+      <MantineProvider>
+        <MessageItem message={message} signature={messageSignature(message)} />
+      </MantineProvider>,
+    );
+    // Empty text part: nothing visible rendered yet.
+    expect(queryByText("streamed answer")).toBeNull();
+
+    // SDK delta: mutate the SAME part in place, then re-render with a NEW snapshot.
+    (message.parts[0] as { text: string }).text = "streamed answer";
+    rerender(
+      <MantineProvider>
+        <MessageItem message={message} signature={messageSignature(message)} />
+      </MantineProvider>,
+    );
+
+    // The grown text now renders (the memo did NOT freeze the empty mount).
+    expect(callsFor("streamed answer")).toBe(1);
+    expect(queryByText("streamed answer")).not.toBeNull();
+  });
 });

apps/client/src/features/ai-chat/components/message-item.test.ts

@@ -10,21 +10,28 @@ vi.mock("react-i18next", () => ({
 }));
 
 import { arePropsEqual } from "./message-item";
+import { messageSignature } from "@/features/ai-chat/utils/message-signature.ts";
 
 /**
  * Tests for `arePropsEqual`, the `React.memo` comparator for MessageItem. It must
  * return false on any visible prop/content change (so the row re-renders) and
- * true when nothing visible changed (so a finalized row is skipped). A FIXED
- * message id is used so a content-identical clone yields an equal signature.
+ * true when nothing visible changed (so a finalized row is skipped). The memo key
+ * is the `signature` PROP — an immutable snapshot the PARENT (MessageList) takes
+ * per render via `messageSignature(message)`. A FIXED message id is used so a
+ * content-identical clone yields an equal signature.
  */
 const msg = (parts: UIMessage["parts"]): UIMessage =>
   ({ id: "m1", role: "assistant", parts }) as UIMessage;
 
+// Build the props the parent would pass, INCLUDING the snapshot signature it
+// computes during its own render (the load-bearing part — see message-item.tsx:
+// the signature must never be recomputed inside arePropsEqual).
 const props = (
   message: UIMessage,
   over: Record<string, unknown> = {},
 ) => ({
   message,
+  signature: messageSignature(message),
   showCitations: true,
   neutralizeInternalLinks: false,
   assistantName: "AI",
@@ -53,7 +60,7 @@ describe("arePropsEqual", () => {
     ).toBe(false);
   });
 
-  it("returns true on the identity fast path (same message object, equal props)", () => {
+  it("returns true for equal snapshot + equal props (finalized row skipped)", () => {
     const m = msg([{ type: "text", text: "answer" }]);
     expect(arePropsEqual(props(m), props(m))).toBe(true);
   });
@@ -70,4 +77,36 @@ describe("arePropsEqual", () => {
     const b = msg([{ type: "text", text: "answer grown" }]);
     expect(arePropsEqual(props(a), props(b))).toBe(false);
   });
+
+  // REGRESSION (empty-render bug): the AI SDK streams deltas by mutating the SAME
+  // `parts` in place and handing back a message wrapper that SHARES them. So the
+  // PREVIOUS and NEXT props can carry the SAME (mutated) message object, and
+  // recomputing `messageSignature(message)` inside the comparator would read
+  // identical (latest) content on BOTH sides → always "equal" → the memo skips
+  // every streamed update and the assistant row freezes at its initial empty
+  // render. The comparator MUST instead trust the immutable `signature` SNAPSHOT
+  // the parent captured at each render. This fails against the old implementation
+  // (a `prev.message === next.message` fast path + a signature recomputed from the
+  // live objects).
+  it("re-renders when parts were mutated in place but the snapshot changed", () => {
+    const message = msg([{ type: "text", text: "" }]); // empty (renders null)
+    const prevSig = messageSignature(message); // snapshot BEFORE the delta
+    // SDK streams a delta by mutating the shared part IN PLACE:
+    (message.parts[0] as { text: string }).text = "hello world";
+    const nextSig = messageSignature(message); // snapshot AFTER the delta
+    expect(prevSig).not.toBe(nextSig);
+    // Same object reference on both sides (the SDK reuses it), differing snapshots.
+    const base = {
+      message,
+      showCitations: true,
+      neutralizeInternalLinks: false,
+      assistantName: "AI",
+    };
+    expect(
+      arePropsEqual(
+        { ...base, signature: prevSig },
+        { ...base, signature: nextSig },
+      ),
+    ).toBe(false);
+  });
 });

apps/client/src/features/ai-chat/components/message-item.tsx

@@ -11,12 +11,30 @@ import { assistantMessageHasVisibleContent } from "@/features/ai-chat/utils/mess
 import { renderChatMarkdown } from "@/features/ai-chat/utils/markdown.ts";
 import { resolveAssistantName } from "@/features/ai-chat/utils/assistant-name.ts";
 import { reasoningTokensForPart } from "@/features/ai-chat/utils/reasoning-tokens.ts";
-import { messageSignature } from "@/features/ai-chat/utils/message-signature.ts";
 import { describeChatError } from "@/features/ai-chat/utils/error-message.ts";
 import classes from "@/features/ai-chat/components/ai-chat.module.css";
 
 interface MessageItemProps {
   message: UIMessage;
+  /**
+   * Immutable content signature for `message`, computed by the PARENT
+   * (MessageList) during its render via `messageSignature(message)`. This is the
+   * memo key (see `arePropsEqual`): it MUST be a snapshot captured at render time,
+   * NOT recomputed from `message` inside `arePropsEqual`.
+   *
+   * WHY (load-bearing): the AI SDK streams deltas by mutating the SAME `parts`
+   * array/objects in place and handing back a message wrapper that SHARES those
+   * mutated parts. So inside `arePropsEqual`, `prev.message` and `next.message`
+   * both reflect the CURRENT (latest) parts — `messageSignature(prev.message) ===
+   * messageSignature(next.message)` is therefore ALWAYS true, the memo skips every
+   * post-mount render, and the assistant row freezes at its initial empty (null)
+   * render — i.e. the streamed answer + tool cards never appear (reasoning-first
+   * providers start empty, so NOTHING shows). Snapshotting the signature into this
+   * immutable string prop in the parent fixes that: `prev.signature` holds the
+   * value from the previous render (old content) and `next.signature` the new
+   * content, so they differ as the turn streams in and the row re-renders.
+   */
+  signature: string;
   /**
    * Forwarded to ToolCallCard: whether tool cards render page citation links.
    * Defaults to true (internal chat). The public share passes false.
@@ -88,6 +106,8 @@ function MessageItem({
   neutralizeInternalLinks = false,
   assistantName,
 }: MessageItemProps) {
+  // `signature` is intentionally not read in the body — it exists solely as the
+  // memo key (see arePropsEqual). The render reads `message` directly.
   const { t } = useTranslation();
   const isUser = message.role === "user";
 
@@ -203,24 +223,30 @@ function MessageItem({
 }
 
 /** Skip re-rendering a message whose visible content is unchanged. The streaming
- *  TAIL message gets a fresh object whose signature changes each delta, so it
- *  still re-renders and streams in; every FINALIZED message is skipped, turning a
- *  per-token whole-transcript re-render into a tail-only one. */
+ *  TAIL message gets a fresh `signature` snapshot each delta (computed by the
+ *  parent), so it still re-renders and streams in; every FINALIZED message keeps
+ *  the same signature and is skipped, turning a per-token whole-transcript
+ *  re-render into a tail-only one.
+ *
+ *  CRITICAL: compare the `signature` PROP (an immutable snapshot the parent took
+ *  at its own render), NEVER `messageSignature(prev.message)` vs
+ *  `messageSignature(next.message)`. The AI SDK mutates the shared `parts` in
+ *  place, so both `prev.message` and `next.message` reflect the latest content
+ *  here — recomputing the signature from them yields equal strings every time and
+ *  freezes the row at its initial empty render (the bug this guards against). See
+ *  the `signature` prop doc. Likewise there is NO `prev.message === next.message`
+ *  fast path: same-reference-but-mutated must still re-render when the snapshot
+ *  signature changed. */
 export function arePropsEqual(
   prev: MessageItemProps,
   next: MessageItemProps,
 ): boolean {
-  if (
-    prev.showCitations !== next.showCitations ||
-    prev.neutralizeInternalLinks !== next.neutralizeInternalLinks ||
-    prev.assistantName !== next.assistantName
-  ) {
-    return false;
-  }
-  // Fast path: identical message object (finalized rows keep their identity
-  // across deltas) — skip without building signatures.
-  if (prev.message === next.message) return true;
-  return messageSignature(prev.message) === messageSignature(next.message);
+  return (
+    prev.signature === next.signature &&
+    prev.showCitations === next.showCitations &&
+    prev.neutralizeInternalLinks === next.neutralizeInternalLinks &&
+    prev.assistantName === next.assistantName
+  );
 }
 
 export default memo(MessageItem, arePropsEqual);

apps/client/src/features/ai-chat/components/message-list.tsx

@@ -6,6 +6,7 @@ import MessageItem from "@/features/ai-chat/components/message-item.tsx";
 import TypingIndicator from "@/features/ai-chat/components/typing-indicator.tsx";
 import { isToolPart, toolRunState, ToolUiPart } from "@/features/ai-chat/utils/tool-parts.tsx";
 import { assistantMessageHasVisibleContent } from "@/features/ai-chat/utils/message-content.ts";
+import { messageSignature } from "@/features/ai-chat/utils/message-signature.ts";
 import classes from "@/features/ai-chat/components/ai-chat.module.css";
 
 interface MessageListProps {
@@ -196,9 +197,16 @@ export default function MessageList({
     <ScrollArea className={classes.messages} viewportRef={viewportRef} scrollbarSize={6} type="scroll">
       <Stack gap={0} pr="xs">
         {messages.map((message) => (
+          // `signature` is snapshotted HERE (parent render) into an immutable
+          // string and handed to MessageItem as its memo key. It must NOT be
+          // recomputed inside MessageItem's arePropsEqual: the AI SDK mutates the
+          // shared `parts` in place, so prev/next message objects both read the
+          // latest content there and the memo would skip every streamed update
+          // (freezing the row at its empty render). See message-item.tsx.
           <MessageItem
             key={message.id}
             message={message}
+            signature={messageSignature(message)}
             showCitations={showCitations}
             neutralizeInternalLinks={neutralizeInternalLinks}
             assistantName={assistantName}

apps/client/src/features/ai-chat/hooks/use-open-ai-chat.test.tsx

@@ -1,135 +0,0 @@
-import { describe, it, expect, vi, beforeEach } from "vitest";
-import { renderHook, act } from "@testing-library/react";
-import { Provider, createStore } from "jotai";
-import type { ReactNode } from "react";
-import { useOpenAiChatForCurrentPage } from "./use-open-ai-chat";
-import {
-  activeAiChatIdAtom,
-  aiChatWindowOpenAtom,
-  aiChatDraftAtom,
-  selectedAiRoleIdAtom,
-} from "@/features/ai-chat/atoms/ai-chat-atom.ts";
-
-// useMatch is the only react-router-dom export the hook uses; drive its return
-// per test to simulate "on a page" vs "off a page".
-const useMatchMock = vi.fn();
-vi.mock("react-router-dom", () => ({
-  useMatch: () => useMatchMock(),
-}));
-
-// The bound-chat resolver is the network boundary; stub it per test.
-const getBoundChatMock = vi.fn();
-vi.mock("@/features/ai-chat/services/ai-chat-service.ts", () => ({
-  getBoundChat: (pageId: string) => getBoundChatMock(pageId),
-}));
-
-// Put the hook on a page route by default ("doc-p1" -> page id "p1"); individual
-// tests override useMatch to go off-page.
-function onPage(pageSlug = "doc-p1") {
-  useMatchMock.mockReturnValue({ params: { pageSlug } });
-}
-function offPage() {
-  useMatchMock.mockReturnValue(null);
-}
-
-// Render the hook inside an explicit jotai store so atom side effects are
-// assertable; the store is returned for setup + assertions.
-function setup(seed?: (store: ReturnType<typeof createStore>) => void) {
-  const store = createStore();
-  seed?.(store);
-  const wrapper = ({ children }: { children: ReactNode }) => (
-    <Provider store={store}>{children}</Provider>
-  );
-  const { result } = renderHook(() => useOpenAiChatForCurrentPage(), { wrapper });
-  return { store, open: () => act(() => result.current()) };
-}
-
-describe("useOpenAiChatForCurrentPage", () => {
-  beforeEach(() => {
-    vi.clearAllMocks();
-    onPage();
-  });
-
-  it("on a page: resolves the bound chat, selects it, and opens the window", async () => {
-    getBoundChatMock.mockResolvedValue("bound-chat-1");
-    const { store, open } = setup((s) => s.set(aiChatDraftAtom, "stale draft"));
-
-    await open();
-
-    expect(getBoundChatMock).toHaveBeenCalledWith("p1");
-    expect(store.get(activeAiChatIdAtom)).toBe("bound-chat-1");
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-    expect(store.get(aiChatDraftAtom)).toBe(""); // cleared on a real switch
-  });
-
-  it("on a page with no bound chat: opens a fresh chat (null)", async () => {
-    getBoundChatMock.mockResolvedValue(null);
-    const { store, open } = setup((s) => s.set(activeAiChatIdAtom, "previous"));
-
-    await open();
-
-    expect(store.get(activeAiChatIdAtom)).toBeNull();
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-  });
-
-  it("off a page: keeps the current selection and does NOT resolve", async () => {
-    offPage();
-    const { store, open } = setup((s) => {
-      s.set(activeAiChatIdAtom, "keep-me");
-      s.set(aiChatDraftAtom, "untouched");
-    });
-
-    await open();
-
-    expect(getBoundChatMock).not.toHaveBeenCalled();
-    expect(store.get(activeAiChatIdAtom)).toBe("keep-me");
-    expect(store.get(aiChatDraftAtom)).toBe("untouched"); // no switch -> kept
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-  });
-
-  it("window already open: re-click does NOT re-resolve or switch chats", async () => {
-    getBoundChatMock.mockResolvedValue("would-switch");
-    const { store, open } = setup((s) => {
-      s.set(aiChatWindowOpenAtom, true);
-      s.set(activeAiChatIdAtom, "current");
-    });
-
-    await open();
-
-    expect(getBoundChatMock).not.toHaveBeenCalled();
-    expect(store.get(activeAiChatIdAtom)).toBe("current");
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-  });
-
-  it("does NOT clear the draft when the resolved chat equals the current one", async () => {
-    getBoundChatMock.mockResolvedValue("same");
-    const { store, open } = setup((s) => {
-      s.set(activeAiChatIdAtom, "same");
-      s.set(aiChatDraftAtom, "in-progress");
-    });
-
-    await open();
-
-    expect(store.get(aiChatDraftAtom)).toBe("in-progress"); // no switch
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-  });
-
-  it("fail-soft: a resolve error opens a fresh chat (null)", async () => {
-    getBoundChatMock.mockRejectedValue(new Error("network"));
-    const { store, open } = setup((s) => s.set(activeAiChatIdAtom, "previous"));
-
-    await open();
-
-    expect(store.get(activeAiChatIdAtom)).toBeNull();
-    expect(store.get(aiChatWindowOpenAtom)).toBe(true);
-  });
-
-  it("clears the picked role on a real switch", async () => {
-    getBoundChatMock.mockResolvedValue("bound");
-    const { store, open } = setup((s) => s.set(selectedAiRoleIdAtom, "role-1"));
-
-    await open();
-
-    expect(store.get(selectedAiRoleIdAtom)).toBeNull();
-  });
-});

apps/client/src/features/ai-chat/hooks/use-open-ai-chat.ts

@@ -1,67 +0,0 @@
-import { useCallback } from "react";
-import { useAtom, useSetAtom } from "jotai";
-import { useMatch } from "react-router-dom";
-import {
-  aiChatWindowOpenAtom,
-  activeAiChatIdAtom,
-  aiChatDraftAtom,
-  selectedAiRoleIdAtom,
-} from "@/features/ai-chat/atoms/ai-chat-atom.ts";
-import { getBoundChat } from "@/features/ai-chat/services/ai-chat-service.ts";
-import { extractPageSlugId } from "@/lib";
-
-/**
- * The generic "open the AI chat" action, WITH document binding: when invoked
- * while viewing a page, it resolves that page's bound chat and selects it before
- * opening — so the last chat for this document re-opens by itself. With no bound
- * chat (or off a page) it keeps the current selection / opens a fresh chat. Used
- * by the app-header entry point; NOT by the provenance badge (which deep-links).
- */
-export function useOpenAiChatForCurrentPage() {
-  const [windowOpen, setWindowOpen] = useAtom(aiChatWindowOpenAtom);
-  const [activeChatId, setActiveChatId] = useAtom(activeAiChatIdAtom);
-  const setDraft = useSetAtom(aiChatDraftAtom);
-  const setSelectedRoleId = useSetAtom(selectedAiRoleIdAtom);
-
-  // Same route-match trick the window uses: read :pageSlug from the pathname.
-  // AiChatWindow lives in a pathless parent layout route, so useParams() can't
-  // see :pageSlug — match the full path against the authenticated page route.
-  const match = useMatch("/s/:spaceSlug/p/:pageSlug");
-  const pageId = extractPageSlugId(match?.params?.pageSlug);
-
-  return useCallback(async () => {
-    // Re-clicks while the window is already open (incl. minimized) must NOT
-    // re-resolve and yank the user to another chat: resolve only on a genuine
-    // closed -> open transition. (`windowOpen` is already true here, so there
-    // is nothing to set — just bail.)
-    if (windowOpen) return;
-    // Open the window FIRST so the control feels instant: the bound-chat
-    // round-trip below must never gate the window appearing, or on a slow
-    // connection the first click reads as a hung control until the POST returns.
-    setWindowOpen(true);
-    let resolved: string | null = activeChatId; // off-a-page: keep current
-    if (pageId) {
-      try {
-        resolved = await getBoundChat(pageId); // null => fresh chat
-      } catch {
-        resolved = null; // fail-soft: a fresh chat is always a safe fallback
-      }
-    }
-    // Clear the composer draft / picked role ONLY on an actual switch, so
-    // reopening the same chat does not wipe an in-progress draft. Applied after
-    // the resolve so the window is already visible while the switch settles.
-    if (resolved !== activeChatId) {
-      setActiveChatId(resolved);
-      setDraft("");
-      setSelectedRoleId(null);
-    }
-  }, [
-    windowOpen,
-    activeChatId,
-    pageId,
-    setWindowOpen,
-    setActiveChatId,
-    setDraft,
-    setSelectedRoleId,
-  ]);
-}

apps/client/src/features/ai-chat/services/ai-chat-service.ts

@@ -37,17 +37,6 @@ export async function getAiChatMessages(
   return req.data;
 }
 
-/**
- * Resolve the chat bound to a document (the current user's most-recent chat
- * created on that page), or null when there is none. Drives auto-open-on-page.
- */
-export async function getBoundChat(pageId: string): Promise<string | null> {
-  const req = await api.post<{ chatId: string | null }>("/ai-chat/bound-chat", {
-    pageId,
-  });
-  return req.data.chatId;
-}
-
 /** Rename a chat. */
 export async function renameAiChat(data: {
   chatId: string;

apps/client/src/features/share/components/share-alias-section.tsx

@@ -1,5 +1,6 @@
 import {
   ActionIcon,
+  Box,
   Button,
   Group,
   Modal,
@@ -7,7 +8,7 @@ import {
   TextInput,
 } from "@mantine/core";
 import { IconExternalLink } from "@tabler/icons-react";
-import { useEffect, useMemo, useRef, useState } from "react";
+import { useEffect, useLayoutEffect, useMemo, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import CopyTextButton from "@/components/common/copy.tsx";
 import { getAppUrl } from "@/lib/config.ts";
@@ -122,12 +123,25 @@ export default function ShareAliasSection({
   const showTaken =
     isValid && !unchanged && availability && !availability.available;
 
+  // The slug prefix (e.g. "docs.example.com/l/") is static for the session.
+  const prefixLabel = aliasPrefixLabel();
+  const prefixRef = useRef<HTMLDivElement>(null);
+  const [prefixWidth, setPrefixWidth] = useState(0);
+
+  // Measure the real rendered width of the prefix so the slug input sits flush
+  // next to it, instead of after an over-estimated character-counted gap.
+  useLayoutEffect(() => {
+    if (prefixRef.current) {
+      setPrefixWidth(Math.ceil(prefixRef.current.scrollWidth) + 1);
+    }
+  }, [prefixLabel]);
+
   return (
     <>
       <Text size="sm" fw={500} mt="md">
         {t("Custom address")}
       </Text>
-      <Text size="xs" c="dimmed" mb={4}>
+      <Text size="xs" c="dimmed" mb={6}>
         {t("A short, memorable link you can point at any shared page.")}
       </Text>
 
@@ -159,11 +173,27 @@ export default function ShareAliasSection({
         // visibly to what gets stored.
         onBlur={() => setValue(normalized)}
         leftSection={
-          <Text size="xs" c="dimmed" pl={4} style={{ whiteSpace: "nowrap" }}>
-            {aliasPrefixLabel()}
-          </Text>
+          <Box
+            ref={prefixRef}
+            style={{
+              display: "flex",
+              alignItems: "center",
+              width: "100%",
+              height: "100%",
+              paddingInline: "var(--mantine-spacing-xs)",
+              whiteSpace: "nowrap",
+              fontSize: "var(--mantine-font-size-xs)",
+              color: "var(--mantine-color-dimmed)",
+              backgroundColor: "var(--mantine-color-default-hover)",
+              borderRight: "1px solid var(--mantine-color-default-border)",
+              borderTopLeftRadius: "var(--input-radius)",
+              borderBottomLeftRadius: "var(--input-radius)",
+            }}
+          >
+            {prefixLabel}
+          </Box>
         }
-        leftSectionWidth={Math.min(aliasPrefixLabel().length * 7 + 12, 180)}
+        leftSectionWidth={prefixWidth || undefined}
         placeholder={t("my-page")}
         disabled={readOnly}
         error={
@@ -175,7 +205,7 @@ export default function ShareAliasSection({
         }
       />
 
-      <Group mt="xs" gap="xs">
+      <Group mt="sm" gap="xs">
         <Button
           size="compact-sm"
           onClick={() => handleSave(false)}

apps/server/src/core/ai-chat/ai-chat.controller.bound-chat.spec.ts

@@ -1,44 +0,0 @@
-import { AiChatController } from './ai-chat.controller';
-import type { User, Workspace } from '@docmost/db/types/entity.types';
-
-/**
- * Wiring spec for the #191 `POST /ai-chat/bound-chat` endpoint. It must forward
- * the requesting user + workspace + pageId to findLatestByPage and return the
- * matched chat's id, or `{ chatId: null }` when there is none. The repo already
- * scopes to the caller's OWN chats, so a foreign pageId simply yields no match
- * (null) — no extra page-access check is needed. Exercised with hand-rolled
- * mocks, no Nest graph and no DB.
- */
-describe('AiChatController.boundChat', () => {
-  const user = { id: 'u1' } as User;
-  const workspace = { id: 'ws1' } as Workspace;
-
-  function makeController(chat: unknown) {
-    const aiChatRepo = {
-      findLatestByPage: jest.fn().mockResolvedValue(chat),
-    };
-    const controller = new AiChatController(
-      {} as never,
-      aiChatRepo as never,
-      {} as never,
-      {} as never,
-    );
-    return { controller, aiChatRepo };
-  }
-
-  it('returns the owned chat id and scopes the lookup to user + workspace + page', async () => {
-    const { controller, aiChatRepo } = makeController({
-      id: 'c1',
-      creatorId: 'u1',
-    });
-    const res = await controller.boundChat({ pageId: 'p1' }, user, workspace);
-    expect(aiChatRepo.findLatestByPage).toHaveBeenCalledWith('u1', 'ws1', 'p1');
-    expect(res).toEqual({ chatId: 'c1' });
-  });
-
-  it('returns { chatId: null } for a page with no owned chat (incl. foreign pageId)', async () => {
-    const { controller } = makeController(undefined);
-    const res = await controller.boundChat({ pageId: 'foreign' }, user, workspace);
-    expect(res).toEqual({ chatId: null });
-  });
-});

apps/server/src/core/ai-chat/ai-chat.controller.ts

@@ -30,7 +30,6 @@ import { FileInterceptor } from '../../common/interceptors/file.interceptor';
 import { AiChatService, AiChatStreamBody } from './ai-chat.service';
 import { AiTranscriptionService } from './ai-transcription.service';
 import {
-  BoundChatDto,
   ChatIdDto,
   ExportChatDto,
   GeneratePageTitleDto,
@@ -68,28 +67,6 @@ export class AiChatController {
     return this.aiChatRepo.findByCreator(user.id, workspace.id, pagination);
   }
 
-  /**
-   * Resolve the chat bound to a document for the requesting user: the most-recent
-   * non-deleted chat created on that page (ai_chats.page_id). Returns
-   * { chatId: null } when the page has no owned chat (-> a fresh chat). No page
-   * access check needed: only the caller's OWN chats are matched, so a foreign
-   * pageId reveals nothing.
-   */
-  @HttpCode(HttpStatus.OK)
-  @Post('bound-chat')
-  async boundChat(
-    @Body() dto: BoundChatDto,
-    @AuthUser() user: User,
-    @AuthWorkspace() workspace: Workspace,
-  ): Promise<{ chatId: string | null }> {
-    const chat = await this.aiChatRepo.findLatestByPage(
-      user.id,
-      workspace.id,
-      dto.pageId,
-    );
-    return { chatId: chat?.id ?? null };
-  }
-
   /** Fetch the messages of a chat (oldest first, paginated). */
   @HttpCode(HttpStatus.OK)
   @Post('messages')

apps/server/src/core/ai-chat/dto/ai-chat.dto.ts

@@ -37,12 +37,6 @@ export class GetChatMessagesDto {
   cursor?: string;
 }
 
-/** Resolve the chat bound to a document (the page's most-recent owned chat). */
-export class BoundChatDto {
-  @IsString()
-  pageId: string;
-}
-
 /** Export a chat to Markdown (#183). `lang` localizes the few fixed
  *  role/tool-action labels; defaults to English server-side. */
 export class ExportChatDto {

apps/server/src/database/repos/ai-chat/ai-chat.repo.spec.ts

@@ -1,85 +0,0 @@
-import { AiChatRepo } from './ai-chat.repo';
-import type { KyselyDB } from '../../types/kysely.types';
-
-/**
- * Unit test for AiChatRepo.findLatestByPage — the "bound chat" resolver behind
- * #191 (auto-open the last chat created on a document). It builds the scoping
- * query, so we assert the EXACT predicates/ordering the spec mandates over a
- * chainable builder mock (no live DB): user + workspace + page scope, the
- * deletedAt filter, newest-by-createdAt with an id tiebreaker, limit 1. A
- * live-Postgres ordering test is out of scope for this pure unit test.
- */
-describe('AiChatRepo.findLatestByPage', () => {
-  type Recorded = {
-    table?: string;
-    wheres: Array<[string, string, unknown]>;
-    orderBys: Array<[string, string]>;
-    limit?: number;
-  };
-
-  function makeDb(result: unknown): { db: KyselyDB; rec: Recorded } {
-    const rec: Recorded = { wheres: [], orderBys: [] };
-    const builder: Record<string, unknown> = {};
-    const chain = () => builder;
-    builder.selectAll = chain;
-    builder.where = (col: string, op: string, val: unknown) => {
-      rec.wheres.push([col, op, val]);
-      return builder;
-    };
-    builder.orderBy = (col: string, dir: string) => {
-      rec.orderBys.push([col, dir]);
-      return builder;
-    };
-    builder.limit = (n: number) => {
-      rec.limit = n;
-      return builder;
-    };
-    builder.executeTakeFirst = () => Promise.resolve(result);
-    const db = {
-      selectFrom: (table: string) => {
-        rec.table = table;
-        return builder;
-      },
-    } as unknown as KyselyDB;
-    return { db, rec };
-  }
-
-  it('returns the matched chat and scopes by user + workspace + page (deletedAt null)', async () => {
-    const chat = { id: 'c1', creatorId: 'u1', workspaceId: 'ws1', pageId: 'p1' };
-    const { db, rec } = makeDb(chat);
-    const repo = new AiChatRepo(db);
-
-    const res = await repo.findLatestByPage('u1', 'ws1', 'p1');
-
-    expect(res).toBe(chat);
-    expect(rec.table).toBe('aiChats');
-    expect(rec.wheres).toEqual(
-      expect.arrayContaining([
-        ['creatorId', '=', 'u1'],
-        ['workspaceId', '=', 'ws1'],
-        ['pageId', '=', 'p1'],
-        ['deletedAt', 'is', null],
-      ]),
-    );
-  });
-
-  it('orders newest-first by createdAt then id, limit 1', async () => {
-    const { db, rec } = makeDb(undefined);
-    const repo = new AiChatRepo(db);
-
-    await repo.findLatestByPage('u1', 'ws1', 'p1');
-
-    expect(rec.orderBys).toEqual([
-      ['createdAt', 'desc'],
-      ['id', 'desc'],
-    ]);
-    expect(rec.limit).toBe(1);
-  });
-
-  it('returns undefined when the page has no owned chat', async () => {
-    const { db } = makeDb(undefined);
-    const repo = new AiChatRepo(db);
-
-    await expect(repo.findLatestByPage('u1', 'ws1', 'p1')).resolves.toBeUndefined();
-  });
-});

apps/server/src/database/repos/ai-chat/ai-chat.repo.ts

@@ -80,32 +80,6 @@ export class AiChatRepo {
     });
   }
 
-  /**
-   * The "bound chat" for a document: the requesting user's most recently
-   * created, non-deleted chat whose origin page is `pageId`. Auto-opened when
-   * the AI chat window is opened on that page. Newest-by-createdAt wins, so a
-   * chat created later on the same page supersedes earlier ones — exactly how
-   * "new chat -> becomes the bound one" falls out for free. Scoped to the user +
-   * workspace, so a foreign pageId can only ever match the caller's own chats.
-   */
-  async findLatestByPage(
-    creatorId: string,
-    workspaceId: string,
-    pageId: string,
-  ): Promise<AiChat | undefined> {
-    return this.db
-      .selectFrom('aiChats')
-      .selectAll('aiChats')
-      .where('creatorId', '=', creatorId)
-      .where('workspaceId', '=', workspaceId)
-      .where('pageId', '=', pageId)
-      .where('deletedAt', 'is', null)
-      .orderBy('createdAt', 'desc')
-      .orderBy('id', 'desc') // stable tiebreaker, mirrors findByCreator's cursor
-      .limit(1)
-      .executeTakeFirst();
-  }
-
   async insert(
     insertable: InsertableAiChat,
     trx?: KyselyTransaction,