diff --git a/e2e/documents-chat.spec.ts b/e2e/documents-chat.spec.ts
index 75987d1a6..ce76987aa 100644
--- a/e2e/documents-chat.spec.ts
+++ b/e2e/documents-chat.spec.ts
@@ -123,25 +123,29 @@ test.describe("document vault — chat about a document", () => {
     );
 
     await page.goto(`/documents?doc=${CONTENT_DOC_ID}`);
-    const sheet = page.getByRole("dialog");
+    const sheet = page.locator('[data-slot="responsive-sheet-content"]');
     await expect(sheet).toBeVisible();
 
+    // The neutral Coach icon lives in the detail-sheet header; tapping it
+    // opens the doc-scoped chat drawer (a sibling overlay).
     const open = sheet.locator('[data-slot="document-chat-open"]');
     await expect(open).toBeVisible();
     await open.click();
 
+    const drawer = page.locator('[data-slot="document-chat-drawer"]');
+    await expect(drawer).toBeVisible();
     await expect(
-      sheet.locator('[data-slot="document-chat-log"]'),
+      drawer.locator('[data-slot="document-chat-log"]'),
     ).toBeVisible();
     await expect(
-      sheet.locator('[data-slot="document-chat-empty"]'),
+      drawer.locator('[data-slot="document-chat-empty"]'),
     ).toBeVisible();
     await expect(
-      sheet.locator('[data-slot="document-chat-input"]'),
+      drawer.locator('[data-slot="document-chat-input"]'),
     ).toBeVisible();
     // The always-on safety note is present.
     await expect(
-      sheet.locator('[data-slot="document-chat-safety"]'),
+      drawer.locator('[data-slot="document-chat-safety"]'),
     ).toContainText("not medical advice");
   });
 
@@ -238,16 +242,18 @@ test.describe("document vault — chat about a document", () => {
     );
 
     await page.goto(`/documents?doc=${CONTENT_DOC_ID}`);
-    const sheet = page.getByRole("dialog");
+    const sheet = page.locator('[data-slot="responsive-sheet-content"]');
     await expect(sheet).toBeVisible();
 
     await sheet.locator('[data-slot="document-chat-open"]').click();
-    const input = sheet.locator('[data-slot="document-chat-input"]');
+    const drawer = page.locator('[data-slot="document-chat-drawer"]');
+    await expect(drawer).toBeVisible();
+    const input = drawer.locator('[data-slot="document-chat-input"]');
     await input.fill(QUESTION);
-    await sheet.locator('[data-slot="document-chat-send"]').click();
+    await drawer.locator('[data-slot="document-chat-send"]').click();
 
     // The user's question and the streamed/settled reply both land in the log.
-    const log = sheet.locator('[data-slot="document-chat-log"]');
+    const log = drawer.locator('[data-slot="document-chat-log"]');
     await expect(log.getByText(QUESTION)).toBeVisible();
     await expect(log.getByText(/findings are unremarkable/)).toBeVisible();
     // The reply settled to a single assistant bubble (no duplicate).
@@ -354,15 +360,17 @@ test.describe("document vault — chat about a document", () => {
     );
 
     await page.goto(`/documents?doc=${CONTENT_DOC_ID}`);
-    const sheet = page.getByRole("dialog");
+    const sheet = page.locator('[data-slot="responsive-sheet-content"]');
     await expect(sheet).toBeVisible();
 
     await sheet.locator('[data-slot="document-chat-open"]').click();
-    const input = sheet.locator('[data-slot="document-chat-input"]');
+    const drawer = page.locator('[data-slot="document-chat-drawer"]');
+    await expect(drawer).toBeVisible();
+    const input = drawer.locator('[data-slot="document-chat-input"]');
     await input.fill(QUESTION);
-    await sheet.locator('[data-slot="document-chat-send"]').click();
+    await drawer.locator('[data-slot="document-chat-send"]').click();
 
-    const log = sheet.locator('[data-slot="document-chat-log"]');
+    const log = drawer.locator('[data-slot="document-chat-log"]');
     // The describe-only answer lands; the panel renders the model's <script>
     // payload as literal text (proof it is a React text child, not HTML).
     await expect(log.getByText(/treat it as document content/)).toBeVisible();
@@ -387,18 +395,27 @@ test.describe("document vault — chat about a document", () => {
     // AI_PROBE_DOC_ID carries no content index (hasContentIndex === false).
     await mockAiEnabled(page);
     await page.goto(`/documents?doc=${AI_PROBE_DOC_ID}`);
-    const sheet = page.getByRole("dialog");
+    const sheet = page.locator('[data-slot="responsive-sheet-content"]');
     await expect(sheet).toBeVisible();
 
+    // A provider is available, so the Coach entry still shows — it opens the
+    // drawer, whose body carries the calm read-it-first hint (never an error)
+    // and no composer, because there is nothing indexed to ground on yet.
+    const open = sheet.locator('[data-slot="document-chat-open"]');
+    await expect(open).toBeVisible();
+    await open.click();
+
+    const drawer = page.locator('[data-slot="document-chat-drawer"]');
+    await expect(drawer).toBeVisible();
     await expect(
-      sheet.locator('[data-slot="document-chat-not-indexed"]'),
+      drawer.locator('[data-slot="document-chat-not-indexed"]'),
     ).toBeVisible();
-    // No chat entry, and no error styling.
-    await expect(sheet.locator('[data-slot="document-chat-open"]')).toHaveCount(
-      0,
-    );
+    // No composer, and no error styling.
     await expect(
-      sheet.locator('[data-slot="document-chat"] [role="alert"]'),
+      drawer.locator('[data-slot="document-chat-input"]'),
+    ).toHaveCount(0);
+    await expect(
+      drawer.locator('[data-slot="document-chat"] [role="alert"]'),
     ).toHaveCount(0);
   });
 
@@ -410,7 +427,7 @@ test.describe("document vault — chat about a document", () => {
     // No mocks — the seeded demo user has no AI provider configured, so the AI
     // area collapses to the calm pointer and the chat slot never renders.
     await page.goto(`/documents?doc=${CONTENT_DOC_ID}`);
-    const sheet = page.getByRole("dialog");
+    const sheet = page.locator('[data-slot="responsive-sheet-content"]');
     await expect(sheet).toBeVisible();
 
     await expect(
@@ -419,6 +436,13 @@ test.describe("document vault — chat about a document", () => {
     await expect(
       sheet.getByRole("link", { name: "Open AI settings" }),
     ).toBeVisible();
-    await expect(sheet.locator('[data-slot="document-chat"]')).toHaveCount(0);
+    // No provider → no Coach entry in the header and no chat drawer mounted.
+    await expect(sheet.locator('[data-slot="document-chat-open"]')).toHaveCount(
+      0,
+    );
+    await expect(
+      page.locator('[data-slot="document-chat-drawer"]'),
+    ).toHaveCount(0);
+    await expect(page.locator('[data-slot="document-chat"]')).toHaveCount(0);
   });
 });
diff --git a/messages/de.json b/messages/de.json
index cc0acbaaf..097bc51db 100644
--- a/messages/de.json
+++ b/messages/de.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Über dieses Dokument chatten",
-      "open": "Über dieses Dokument chatten",
       "notIndexed": "Lies das Dokument zuerst mit KI, um darüber zu chatten.",
       "empty": "Stelle eine Frage zu diesem Dokument, um zu beginnen.",
       "placeholder": "Frage zu diesem Dokument…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "Das tägliche KI-Limit ist erreicht. Bitte morgen erneut versuchen.",
       "errorCredential": "Der KI-Anbieter muss in den Einstellungen neu verbunden werden.",
       "errorConsent": "Aktiviere die KI-Zustimmung in den Einstellungen, um über dieses Dokument zu chatten.",
-      "errorNetwork": "Du scheinst offline zu sein. Prüfe deine Verbindung und versuche es erneut."
+      "errorNetwork": "Du scheinst offline zu sein. Prüfe deine Verbindung und versuche es erneut.",
+      "openAria": "Über dieses Dokument chatten",
+      "scopeBadge": "Chat über: {title}"
     }
   },
   "selfDescription": {
diff --git a/messages/en.json b/messages/en.json
index 7f1d98165..bd988529d 100644
--- a/messages/en.json
+++ b/messages/en.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Chat about this document",
-      "open": "Chat about this document",
       "notIndexed": "Read this document with AI first to chat about it.",
       "empty": "Ask a question about this document to get started.",
       "placeholder": "Ask about this document…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "The daily AI limit has been reached. Try again tomorrow.",
       "errorCredential": "The AI provider needs reconnecting in settings.",
       "errorConsent": "Turn on AI consent in settings to chat about this document.",
-      "errorNetwork": "You appear to be offline. Check your connection and try again."
+      "errorNetwork": "You appear to be offline. Check your connection and try again.",
+      "openAria": "Chat about this document",
+      "scopeBadge": "Chatting about: {title}"
     }
   },
   "selfDescription": {
diff --git a/messages/es.json b/messages/es.json
index b57d835bb..b38a7e064 100644
--- a/messages/es.json
+++ b/messages/es.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Chatea sobre este documento",
-      "open": "Chatea sobre este documento",
       "notIndexed": "Primero lee este documento con IA para poder chatear sobre él.",
       "empty": "Haz una pregunta sobre este documento para empezar.",
       "placeholder": "Pregunta sobre este documento…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "Se alcanzó el límite diario de IA. Inténtalo de nuevo mañana.",
       "errorCredential": "Hay que volver a conectar el proveedor de IA en los ajustes.",
       "errorConsent": "Activa el consentimiento de IA en los ajustes para chatear sobre este documento.",
-      "errorNetwork": "Parece que no tienes conexión. Comprueba tu red e inténtalo de nuevo."
+      "errorNetwork": "Parece que no tienes conexión. Comprueba tu red e inténtalo de nuevo.",
+      "openAria": "Chatea sobre este documento",
+      "scopeBadge": "Chateando sobre: {title}"
     }
   },
   "selfDescription": {
diff --git a/messages/fr.json b/messages/fr.json
index 019f2e55b..806eb8370 100644
--- a/messages/fr.json
+++ b/messages/fr.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Discuter de ce document",
-      "open": "Discuter de ce document",
       "notIndexed": "Lisez d'abord ce document avec l'IA pour pouvoir en discuter.",
       "empty": "Posez une question sur ce document pour commencer.",
       "placeholder": "Une question sur ce document…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "La limite quotidienne d'IA est atteinte. Réessayez demain.",
       "errorCredential": "Le fournisseur d'IA doit être reconnecté dans les paramètres.",
       "errorConsent": "Activez le consentement à l'IA dans les paramètres pour discuter de ce document.",
-      "errorNetwork": "Vous semblez hors ligne. Vérifiez votre connexion et réessayez."
+      "errorNetwork": "Vous semblez hors ligne. Vérifiez votre connexion et réessayez.",
+      "openAria": "Discuter de ce document",
+      "scopeBadge": "Discussion sur : {title}"
     }
   },
   "selfDescription": {
diff --git a/messages/it.json b/messages/it.json
index 63168d001..5af82562b 100644
--- a/messages/it.json
+++ b/messages/it.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Chatta su questo documento",
-      "open": "Chatta su questo documento",
       "notIndexed": "Leggi prima questo documento con l'IA per poterne parlare.",
       "empty": "Fai una domanda su questo documento per iniziare.",
       "placeholder": "Una domanda su questo documento…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "Limite giornaliero di IA raggiunto. Riprova domani.",
       "errorCredential": "Il provider IA va ricollegato nelle impostazioni.",
       "errorConsent": "Attiva il consenso all'IA nelle impostazioni per chattare su questo documento.",
-      "errorNetwork": "Sembri offline. Controlla la connessione e riprova."
+      "errorNetwork": "Sembri offline. Controlla la connessione e riprova.",
+      "openAria": "Chatta su questo documento",
+      "scopeBadge": "Stai chattando su: {title}"
     }
   },
   "selfDescription": {
diff --git a/messages/pl.json b/messages/pl.json
index 72e409730..a4fca6cf0 100644
--- a/messages/pl.json
+++ b/messages/pl.json
@@ -8283,7 +8283,6 @@
     },
     "chat": {
       "title": "Porozmawiaj o tym dokumencie",
-      "open": "Porozmawiaj o tym dokumencie",
       "notIndexed": "Najpierw przeczytaj ten dokument z pomocą AI, aby o nim porozmawiać.",
       "empty": "Zadaj pytanie o ten dokument, aby zacząć.",
       "placeholder": "Zapytaj o ten dokument…",
@@ -8298,7 +8297,9 @@
       "errorBudget": "Osiągnięto dzienny limit AI. Spróbuj ponownie jutro.",
       "errorCredential": "Dostawcę AI trzeba ponownie połączyć w ustawieniach.",
       "errorConsent": "Włącz zgodę na AI w ustawieniach, aby porozmawiać o tym dokumencie.",
-      "errorNetwork": "Wygląda na to, że jesteś offline. Sprawdź połączenie i spróbuj ponownie."
+      "errorNetwork": "Wygląda na to, że jesteś offline. Sprawdź połączenie i spróbuj ponownie.",
+      "openAria": "Porozmawiaj o tym dokumencie",
+      "scopeBadge": "Rozmowa o: {title}"
     }
   },
   "selfDescription": {
diff --git a/src/components/documents/__tests__/document-ai-section.test.tsx b/src/components/documents/__tests__/document-ai-section.test.tsx
index aedba8dc2..87955d85c 100644
--- a/src/components/documents/__tests__/document-ai-section.test.tsx
+++ b/src/components/documents/__tests__/document-ai-section.test.tsx
@@ -156,20 +156,18 @@ describe("<DocumentAiSection>", () => {
     expect(html).not.toContain('data-slot="document-read-ai"');
   });
 
-  it("hides the manual AI action row when auto-read is on, keeping status + chat", () => {
-    const chat = <div data-slot="chat-probe">chat here</div>;
-    const html = render(
-      base({ aiEnabled: true, autoReadEnabled: true, chatSlot: chat }),
-    );
+  it("hides the manual AI action row when auto-read is on, keeping status", () => {
+    const html = render(base({ aiEnabled: true, autoReadEnabled: true }));
     // Auto-read reads on upload — the manual per-document actions are gone.
     expect(html).not.toContain('data-slot="document-read-ai"');
     expect(html).not.toContain('data-slot="assist-suggest"');
     expect(html).not.toContain("Summarise");
     expect(html).not.toContain("Show extracted text");
-    // The header, the searchable status pill, and content-search chat stay.
+    // The header and the searchable status pill stay. The scoped chat entry
+    // now lives in the detail-sheet header (a neutral Coach icon), not in this
+    // section, so this block no longer owns a chat slot.
     expect(html).toContain('data-slot="document-ai-section"');
     expect(html).toContain('data-slot="content-search-status"');
-    expect(html).toContain('data-slot="chat-probe"');
   });
 
   it("shows the manual AI action row when auto-read is off", () => {
@@ -178,23 +176,4 @@ describe("<DocumentAiSection>", () => {
     expect(html).toContain('data-slot="assist-suggest"');
     expect(html).toContain("Summarise");
   });
-
-  it("renders the chat slot inside the AI area only when a provider is available", () => {
-    const chat = <div data-slot="chat-probe">chat here</div>;
-    const enabled = render(base({ aiEnabled: true, chatSlot: chat }));
-    expect(enabled).toContain('data-slot="chat-probe"');
-
-    // No provider → the whole block collapses to the calm pointer; the chat
-    // slot (provider-only affordance) must not render.
-    const disabled = render(
-      base({
-        aiEnabled: false,
-        indexEnabled: false,
-        unavailableReason: "no-provider",
-        chatSlot: chat,
-      }),
-    );
-    expect(disabled).not.toContain('data-slot="chat-probe"');
-    expect(disabled).toContain('data-slot="assist-unavailable"');
-  });
 });
diff --git a/src/components/documents/__tests__/document-chat-panel.test.tsx b/src/components/documents/__tests__/document-chat-panel.test.tsx
index c43ced04d..7ea182826 100644
--- a/src/components/documents/__tests__/document-chat-panel.test.tsx
+++ b/src/components/documents/__tests__/document-chat-panel.test.tsx
@@ -1,24 +1,24 @@
 import { describe, expect, it } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
-import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 
 import { I18nProvider } from "@/lib/i18n/context";
 import {
   DocumentChatConversation,
-  DocumentChatPanel,
   documentChatErrorKey,
 } from "../document-chat-panel";
 import type { DocumentChatMessage } from "../use-document-chat";
 
 /**
- * The scoped "chat about this document" panel:
+ * The scoped "chat about this document" surface:
  *   - the OPEN conversation body renders a plain-text message log + composer +
  *     an always-on safety note; assistant/user prose is XSS-safe React text
  *     (raw HTML in a turn is escaped, never injected);
- *   - the container gates on indexing: a content-indexed document offers the
- *     chat entry, a non-indexed one shows a calm read-it-first hint (never an
- *     error);
  *   - error codes map to calm translation keys, never a raw provider string.
+ *
+ * The stateful container + indexing gate live in `document-chat-drawer.tsx`
+ * (Coach-drawer chrome scoped to one document); its open/not-indexed branches
+ * ride the Radix Sheet portal, so they are pinned by the e2e suite rather than
+ * a static render here.
  */
 
 function renderPure(node: React.ReactNode) {
@@ -27,17 +27,6 @@ function renderPure(node: React.ReactNode) {
   );
 }
 
-function renderContainer(node: React.ReactNode) {
-  const queryClient = new QueryClient({
-    defaultOptions: { queries: { retry: false } },
-  });
-  return renderToStaticMarkup(
-    <QueryClientProvider client={queryClient}>
-      <I18nProvider initialLocale="en">{node}</I18nProvider>
-    </QueryClientProvider>,
-  );
-}
-
 const noop = () => {};
 
 function conversation(
@@ -154,27 +143,6 @@ describe("<DocumentChatConversation> (open body)", () => {
   });
 });
 
-describe("<DocumentChatPanel> (gating)", () => {
-  it("offers the chat entry when the document is content-indexed", () => {
-    const html = renderContainer(
-      <DocumentChatPanel documentId="doc1" indexed />,
-    );
-    expect(html).toContain('data-slot="document-chat-open"');
-    expect(html).toContain("Chat about this document");
-    // Not the not-indexed hint.
-    expect(html).not.toContain('data-slot="document-chat-not-indexed"');
-  });
-
-  it("shows a calm read-it-first hint (never an error) when not indexed", () => {
-    const html = renderContainer(
-      <DocumentChatPanel documentId="doc1" indexed={false} />,
-    );
-    expect(html).toContain('data-slot="document-chat-not-indexed"');
-    expect(html).not.toContain('data-slot="document-chat-open"');
-    expect(html).not.toContain('role="alert"');
-  });
-});
-
 describe("documentChatErrorKey", () => {
   it("maps provider + client codes to calm keys, defaulting to generic", () => {
     expect(documentChatErrorKey("documents.chat.budget.exceeded")).toBe(
diff --git a/src/components/documents/document-ai-section.tsx b/src/components/documents/document-ai-section.tsx
index 314745c2d..da39c1341 100644
--- a/src/components/documents/document-ai-section.tsx
+++ b/src/components/documents/document-ai-section.tsx
@@ -23,7 +23,6 @@
  * form below stays fully usable.
  */
 import { FileText, ScanText, WandSparkles } from "lucide-react";
-import type { ReactNode } from "react";
 
 import { Button } from "@/components/ui/button";
 import { useTranslations } from "@/lib/i18n/context";
@@ -70,7 +69,6 @@ export function DocumentAiSection({
   contentIndexSource,
   indexPending,
   onIndex,
-  chatSlot,
 }: {
   aiEnabled: boolean;
   /**
@@ -106,14 +104,6 @@ export function DocumentAiSection({
   contentIndexSource: DocumentContentIndexSourceValue | null;
   indexPending: boolean;
   onIndex: () => void;
-  /**
-   * The scoped "chat about this document" panel, rendered inside the AI area
-   * beneath the reading actions. Only supplied (and only meaningful) when a
-   * provider is available — the panel itself gates on whether the document is
-   * indexed. A pure slot so this section stays presentational + statically
-   * renderable (the stateful, query-driven panel lives in the sheet).
-   */
-  chatSlot?: ReactNode;
 }) {
   const { t } = useTranslations();
   const aiRead = hasContentIndex && isAiReadSource(contentIndexSource);
@@ -231,8 +221,6 @@ export function DocumentAiSection({
               onClose={onCloseSummary}
             />
           ) : null}
-
-          {chatSlot}
         </>
       ) : (
         <AiUnavailableHint reason={unavailableReason} />
diff --git a/src/components/documents/document-chat-drawer.tsx b/src/components/documents/document-chat-drawer.tsx
new file mode 100644
index 000000000..359ce27af
--- /dev/null
+++ b/src/components/documents/document-chat-drawer.tsx
@@ -0,0 +1,211 @@
+"use client";
+
+/**
+ * The scoped "chat about this document" surface, presented in the Coach chat
+ * drawer chrome (right-side `<Sheet>` on desktop, bottom sheet on phones — the
+ * same width caps and slide behaviour as the general Coach drawer). It is
+ * CHROME reuse only: the conversation body, the client hooks, and the endpoint
+ * stay the document-scoped ones, so the v1.27.33 posture is untouched — the
+ * drawer POSTs `/api/documents/inbound/[id]/chat` (no tools, no health
+ * snapshot, fenced document, inbound/replay refusal, outbound screen, numeric
+ * grounding, consent + budget + per-user rate bucket, indexed-only), and the
+ * assistant prose renders as PLAIN React text (no markdown library, no
+ * `dangerouslySetInnerHTML`).
+ *
+ * Unlike the general Coach drawer this one has NO maximize and NO
+ * conversations rail — both hand off to `/coach`, which does not apply to a
+ * single document thread. It carries a quiet scope badge ("Chatting about:
+ * <document>") so the user always sees the conversation is fenced to this one
+ * document, and a single close control.
+ *
+ * Open/close is owned by the detail sheet (the top-right neutral Coach icon
+ * toggles it); this component is fully controlled. When the document is not
+ * content-indexed the body shows the calm read-it-first hint (never an error),
+ * matching the former inline panel.
+ */
+import { FileText, X } from "lucide-react";
+import { useEffect, useRef, useState } from "react";
+
+import { Button } from "@/components/ui/button";
+import {
+  Sheet,
+  SheetClose,
+  SheetContent,
+  SheetDescription,
+  SheetTitle,
+} from "@/components/ui/sheet";
+import { useIsMobile } from "@/hooks/use-is-mobile";
+import { useTranslations } from "@/lib/i18n/context";
+import { cn } from "@/lib/utils";
+
+import {
+  DocumentChatConversation,
+  documentChatErrorKey,
+} from "./document-chat-panel";
+import {
+  useDocumentChatThread,
+  useSendDocumentChatMessage,
+} from "./use-document-chat";
+
+export function DocumentChatDrawer({
+  open,
+  onOpenChange,
+  documentId,
+  indexed,
+  documentTitle,
+}: {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  documentId: string;
+  /** True when the document has a content index (its text grounds the chat). */
+  indexed: boolean;
+  /** Resolved document title for the scope badge. */
+  documentTitle: string;
+}) {
+  const { t, locale } = useTranslations();
+  // Below `sm` (640 px) the drawer slides up from the bottom edge so the
+  // header chrome stays near the user's thumb; above it keeps the right-side
+  // slide + width cap — the same behaviour as the general Coach drawer.
+  const isPhoneViewport = useIsMobile("sm");
+
+  const [draft, setDraft] = useState("");
+  const logRef = useRef<HTMLDivElement | null>(null);
+
+  const thread = useDocumentChatThread(documentId, open && indexed);
+  const { streaming, isStreaming, optimisticUser, send, reset } =
+    useSendDocumentChatMessage(documentId);
+
+  const messages = thread.data?.messages ?? [];
+  const conversationId = thread.data?.conversationId ?? undefined;
+
+  // The optimistic bubble is dropped once its persisted twin lands (matched by
+  // content on the freshest user turn), so the user never sees it twice.
+  const lastUser = [...messages].reverse().find((m) => m.role === "user");
+  const showOptimistic =
+    optimisticUser !== null && lastUser?.content !== optimisticUser;
+
+  // Keep the newest turn in view as messages / tokens land.
+  useEffect(() => {
+    const el = logRef.current;
+    if (el) el.scrollTop = el.scrollHeight;
+  }, [messages.length, streaming.content, showOptimistic, isStreaming]);
+
+  const chatLocale = locale === "de" ? "de" : "en";
+
+  const submit = () => {
+    const message = draft.trim();
+    if (!message || isStreaming) return;
+    setDraft("");
+    void send({ conversationId, message, locale: chatLocale });
+  };
+
+  const handleOpenChange = (next: boolean) => {
+    // Closing discards the live stream state (the persisted history stays on
+    // disk and reloads next open) — mirrors the Coach drawer's reset-on-close.
+    if (!next) reset();
+    onOpenChange(next);
+  };
+
+  return (
+    <Sheet open={open} onOpenChange={handleOpenChange}>
+      <SheetContent
+        side={isPhoneViewport ? "bottom" : "right"}
+        showCloseButton={false}
+        data-slot="document-chat-drawer"
+        data-variant={isPhoneViewport ? "bottom-sheet" : "side-sheet"}
+        className={cn(
+          "w-full p-0 sm:max-w-[720px]",
+          "lg:!max-w-[min(960px,75vw)] xl:!max-w-[1080px]",
+          isPhoneViewport
+            ? "flex h-[90dvh] max-h-[90dvh] flex-col gap-0 rounded-t-2xl"
+            : "flex h-[100dvh] flex-col gap-0",
+        )}
+      >
+        {/* Header: the accessible name + description stay mounted for Radix; the
+            visible line is the quiet scope badge + the close control. */}
+        <div className="border-border/70 flex items-start justify-between gap-3 border-b p-4">
+          <div className="min-w-0 flex-1">
+            <SheetTitle className="sr-only">
+              {t("documents.chat.title")}
+            </SheetTitle>
+            <SheetDescription className="sr-only">
+              {t("documents.chat.safety")}
+            </SheetDescription>
+            <span
+              data-slot="document-chat-scope"
+              className={cn(
+                "border-border/60 bg-muted/40 text-muted-foreground",
+                "inline-flex max-w-full items-center gap-1.5 rounded-full border px-3 py-1",
+                "text-xs font-medium",
+              )}
+            >
+              <FileText
+                className="text-muted-foreground size-3.5 shrink-0"
+                aria-hidden="true"
+              />
+              <span className="truncate">
+                {t("documents.chat.scopeBadge", { title: documentTitle })}
+              </span>
+            </span>
+          </div>
+          <SheetClose asChild>
+            <Button
+              type="button"
+              variant="ghost"
+              size="icon-lg"
+              data-slot="document-chat-drawer-close"
+              aria-label={t("common.close")}
+              title={t("common.close")}
+              className="text-muted-foreground hover:text-foreground shrink-0"
+            >
+              <X className="size-4" aria-hidden="true" />
+            </Button>
+          </SheetClose>
+        </div>
+
+        <div
+          data-slot="document-chat-body"
+          className="flex min-h-0 flex-1 flex-col overflow-y-auto p-4"
+        >
+          {indexed ? (
+            <DocumentChatConversation
+              messages={messages}
+              optimisticContent={showOptimistic ? optimisticUser : null}
+              streamingContent={streaming.content}
+              isStreaming={isStreaming}
+              streamErrorKey={
+                streaming.errorCode
+                  ? documentChatErrorKey(streaming.errorCode)
+                  : null
+              }
+              historyPending={thread.isPending}
+              historyError={thread.isError}
+              draft={draft}
+              onDraftChange={setDraft}
+              onSubmit={submit}
+              onClose={() => handleOpenChange(false)}
+              logRef={logRef}
+            />
+          ) : (
+            // Not indexed: a calm pointer to read it with AI first (never an
+            // error) — the drawer opens, it just has nothing to ground on yet.
+            <div
+              data-slot="document-chat"
+              className="border-border/60 space-y-2 border-t pt-3"
+            >
+              <p className="text-sm font-semibold">
+                {t("documents.chat.title")}
+              </p>
+              <p
+                data-slot="document-chat-not-indexed"
+                className="text-muted-foreground text-xs"
+              >
+                {t("documents.chat.notIndexed")}
+              </p>
+            </div>
+          )}
+        </div>
+      </SheetContent>
+    </Sheet>
+  );
+}
diff --git a/src/components/documents/document-chat-panel.tsx b/src/components/documents/document-chat-panel.tsx
index afe59f7a0..828ce72ee 100644
--- a/src/components/documents/document-chat-panel.tsx
+++ b/src/components/documents/document-chat-panel.tsx
@@ -20,13 +20,16 @@
  * safety note states answers describe the document and are not medical advice,
  * consistent with the summary panel's "not a diagnosis".
  *
- * Split: a stateful container (`DocumentChatPanel`) owns the hooks + open/gate
- * state; the pure `DocumentChatConversation` renders the open body (log + input
- * + safety note) from props, so the conversation surface is statically
- * renderable and pinned by tests without a query client.
+ * This module owns the PURE surface: `DocumentChatConversation` renders the
+ * open body (log + input + safety note) from props, so the conversation is
+ * statically renderable and pinned by tests without a query client, and
+ * `documentChatErrorKey` maps a server / client code to a calm copy key. The
+ * stateful container (hooks + open/gate state) lives in
+ * `document-chat-drawer.tsx`, which presents this body in the Coach drawer
+ * chrome scoped to a single document.
  */
 import { MessageSquare, Send } from "lucide-react";
-import { useEffect, useRef, useState, type RefObject } from "react";
+import { type RefObject } from "react";
 
 import { StreamedProse } from "@/components/insights/coach-panel/streamed-prose";
 import { ProseBlocks } from "@/components/insights/prose-blocks";
@@ -36,11 +39,7 @@ import { Skeleton } from "@/components/ui/skeleton";
 import { useTranslations } from "@/lib/i18n/context";
 import { cn } from "@/lib/utils";
 
-import {
-  useDocumentChatThread,
-  useSendDocumentChatMessage,
-  type DocumentChatMessage,
-} from "./use-document-chat";
+import { type DocumentChatMessage } from "./use-document-chat";
 
 /** Map a server / client error code to a calm translation key. */
 export function documentChatErrorKey(code: string | null): string {
@@ -277,116 +276,3 @@ export function DocumentChatConversation({
     </div>
   );
 }
-
-/**
- * The stateful container: owns the open/gate state + the history / streaming
- * hooks, and delegates the open body to `DocumentChatConversation`.
- */
-export function DocumentChatPanel({
-  documentId,
-  indexed,
-}: {
-  documentId: string;
-  /** True when the document has a content index (its text grounds the chat). */
-  indexed: boolean;
-}) {
-  const { t, locale } = useTranslations();
-  const [open, setOpen] = useState(false);
-  const [draft, setDraft] = useState("");
-  const logRef = useRef<HTMLDivElement | null>(null);
-
-  const thread = useDocumentChatThread(documentId, open && indexed);
-  const { streaming, isStreaming, optimisticUser, send, reset } =
-    useSendDocumentChatMessage(documentId);
-
-  const messages = thread.data?.messages ?? [];
-  const conversationId = thread.data?.conversationId ?? undefined;
-
-  // The optimistic bubble is dropped once its persisted twin lands (matched by
-  // content on the freshest user turn), so the user never sees it twice.
-  const lastUser = [...messages].reverse().find((m) => m.role === "user");
-  const showOptimistic =
-    optimisticUser !== null && lastUser?.content !== optimisticUser;
-
-  // Keep the newest turn in view as messages / tokens land.
-  useEffect(() => {
-    const el = logRef.current;
-    if (el) el.scrollTop = el.scrollHeight;
-  }, [messages.length, streaming.content, showOptimistic, isStreaming]);
-
-  const chatLocale = locale === "de" ? "de" : "en";
-
-  const submit = () => {
-    const message = draft.trim();
-    if (!message || isStreaming) return;
-    setDraft("");
-    void send({ conversationId, message, locale: chatLocale });
-  };
-
-  // ── Not indexed: calm pointer to the read action above (never an error) ──
-  if (!indexed) {
-    return (
-      <div
-        data-slot="document-chat"
-        className="border-border/60 space-y-2 border-t pt-3"
-      >
-        <div className="flex items-center gap-2">
-          <MessageSquare
-            className="text-foreground size-4 shrink-0"
-            aria-hidden
-          />
-          <p className="text-sm font-semibold">{t("documents.chat.title")}</p>
-        </div>
-        <p
-          data-slot="document-chat-not-indexed"
-          className="text-muted-foreground text-xs"
-        >
-          {t("documents.chat.notIndexed")}
-        </p>
-      </div>
-    );
-  }
-
-  // ── Collapsed entry: available, opens the scoped chat on tap ──
-  if (!open) {
-    return (
-      <div
-        data-slot="document-chat"
-        className="border-border/60 space-y-2 border-t pt-3"
-      >
-        <Button
-          type="button"
-          variant="outline"
-          size="sm"
-          data-slot="document-chat-open"
-          onClick={() => setOpen(true)}
-        >
-          <MessageSquare className="size-4" aria-hidden />
-          {t("documents.chat.open")}
-        </Button>
-      </div>
-    );
-  }
-
-  return (
-    <DocumentChatConversation
-      messages={messages}
-      optimisticContent={showOptimistic ? optimisticUser : null}
-      streamingContent={streaming.content}
-      isStreaming={isStreaming}
-      streamErrorKey={
-        streaming.errorCode ? documentChatErrorKey(streaming.errorCode) : null
-      }
-      historyPending={thread.isPending}
-      historyError={thread.isError}
-      draft={draft}
-      onDraftChange={setDraft}
-      onSubmit={submit}
-      onClose={() => {
-        reset();
-        setOpen(false);
-      }}
-      logRef={logRef}
-    />
-  );
-}
diff --git a/src/components/documents/document-detail-sheet.tsx b/src/components/documents/document-detail-sheet.tsx
index 559954de2..8959688b0 100644
--- a/src/components/documents/document-detail-sheet.tsx
+++ b/src/components/documents/document-detail-sheet.tsx
@@ -17,7 +17,15 @@
  * flow (shared `ShareLinkCreateForm`) with this document pre-attached.
  */
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
-import { Check, Download, Pencil, Plus, Share2, Trash2 } from "lucide-react";
+import {
+  Check,
+  Download,
+  Pencil,
+  Plus,
+  Share2,
+  Sparkles,
+  Trash2,
+} from "lucide-react";
 import Link from "next/link";
 import { useEffect, useRef, useState } from "react";
 import { toast } from "sonner";
@@ -41,6 +49,12 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 import { Skeleton } from "@/components/ui/skeleton";
+import {
+  Tooltip,
+  TooltipContent,
+  TooltipProvider,
+  TooltipTrigger,
+} from "@/components/ui/tooltip";
 import {
   apiDelete,
   ApiError,
@@ -59,7 +73,7 @@ import {
   type InboundDocumentKindValue,
 } from "@/lib/validations/inbound-documents";
 import { DocumentAiSection } from "./document-ai-section";
-import { DocumentChatPanel } from "./document-chat-panel";
+import { DocumentChatDrawer } from "./document-chat-drawer";
 import type { DocumentAiTarget } from "./document-ai-transport";
 import { DocumentShareSheet } from "./document-share-sheet";
 import { DOCUMENT_KIND_ICONS } from "./document-kind-meta";
@@ -231,6 +245,9 @@ export function DocumentDetailSheet({
 
   const [mutationError, setMutationError] = useState<string | null>(null);
   const [shareOpen, setShareOpen] = useState(false);
+  // The doc-scoped Coach chat drawer — opened by the neutral top-right icon in
+  // the sheet header, mounted as a sibling overlay of this detail sheet.
+  const [docChatOpen, setDocChatOpen] = useState(false);
   const [editingTitle, setEditingTitle] = useState(false);
   const [titleDraft, setTitleDraft] = useState("");
   const [suggestion, setSuggestion] = useState<DocumentSuggestionDto | null>(
@@ -251,6 +268,7 @@ export function DocumentDetailSheet({
     setLastDocumentId(documentId);
     setEditingTitle(false);
     setShareOpen(false);
+    setDocChatOpen(false);
     setMutationError(null);
     setSuggestion(null);
     setAppliedFields({ title: false, kind: false, date: false });
@@ -416,6 +434,33 @@ export function DocumentDetailSheet({
         title={title}
         description={t("documents.detail.title")}
         contentWidth="3xl"
+        headerAction={
+          doc && aiEnabled ? (
+            // Neutral, ghost Coach entry pinned top-right of the document —
+            // mirrors the Insights `AskCoachIconButton`. Deliberately NOT the
+            // purple FAB styling: `text-muted-foreground` only. Opens the
+            // doc-scoped chat drawer; the drawer body shows the calm
+            // read-it-first hint when the document is not yet indexed.
+            <TooltipProvider>
+              <Tooltip>
+                <TooltipTrigger asChild>
+                  <Button
+                    type="button"
+                    variant="ghost"
+                    size="icon"
+                    data-slot="document-chat-open"
+                    aria-label={t("documents.chat.openAria")}
+                    onClick={() => setDocChatOpen(true)}
+                    className="text-muted-foreground hover:text-foreground min-h-11 min-w-11 sm:size-8"
+                  >
+                    <Sparkles className="size-4" aria-hidden="true" />
+                  </Button>
+                </TooltipTrigger>
+                <TooltipContent>{t("documents.chat.openAria")}</TooltipContent>
+              </Tooltip>
+            </TooltipProvider>
+          ) : undefined
+        }
         footer={
           doc ? (
             // Delete sits bottom-LEFT, quieted to a text button: the
@@ -541,12 +586,6 @@ export function DocumentDetailSheet({
               contentIndexSource={doc.contentIndexSource}
               indexPending={indexDoc.isPending}
               onIndex={runIndex}
-              chatSlot={
-                <DocumentChatPanel
-                  documentId={doc.id}
-                  indexed={doc.hasContentIndex}
-                />
-              }
             />
 
             {mutationError ? (
@@ -726,6 +765,16 @@ export function DocumentDetailSheet({
           documentTitle={title}
         />
       ) : null}
+
+      {doc && aiEnabled ? (
+        <DocumentChatDrawer
+          open={docChatOpen}
+          onOpenChange={setDocChatOpen}
+          documentId={doc.id}
+          indexed={doc.hasContentIndex}
+          documentTitle={title}
+        />
+      ) : null}
     </>
   );
 }
diff --git a/src/components/ui/responsive-sheet.tsx b/src/components/ui/responsive-sheet.tsx
index d302c99af..19967b9de 100644
--- a/src/components/ui/responsive-sheet.tsx
+++ b/src/components/ui/responsive-sheet.tsx
@@ -34,6 +34,15 @@ export interface ResponsiveSheetProps {
   title: React.ReactNode;
   /** Optional short description rendered beneath the title. */
   description?: React.ReactNode;
+  /**
+   * Optional action rendered `shrink-0` at the trailing edge of the visible
+   * header row (§11 inline-action-row: title `min-w-0 flex-1`, action
+   * `shrink-0`). Use for a single quiet header control — e.g. the neutral
+   * Coach icon on the document detail sheet. Ignored when `hideHeader` is set
+   * (there is no visible header to hang it on). Sits left of the primitive's
+   * absolute close button, whose space the header already reserves.
+   */
+  headerAction?: React.ReactNode;
   /**
    * Hide the visual header (title + description). The title remains
    * mounted in an `sr-only` block so the accessible name is still
@@ -119,6 +128,7 @@ export function ResponsiveSheet({
   onOpenChange,
   title,
   description,
+  headerAction,
   hideHeader = false,
   footer,
   className,
@@ -156,16 +166,37 @@ export function ResponsiveSheet({
           ) : (
             <SheetHeader
               data-slot="responsive-sheet-header"
-              className="border-border/70 gap-1.5 border-b p-4 pr-12"
+              className={cn(
+                "border-border/70 gap-1.5 border-b p-4 pr-12",
+                headerAction && "flex-row items-start justify-between gap-3",
+              )}
             >
-              <SheetTitle className="text-base font-semibold">
-                {title}
-              </SheetTitle>
-              {description ? (
-                <SheetDescription className="text-muted-foreground text-xs">
-                  {description}
-                </SheetDescription>
-              ) : null}
+              {headerAction ? (
+                <>
+                  <div className="flex min-w-0 flex-1 flex-col gap-1.5">
+                    <SheetTitle className="text-base font-semibold">
+                      {title}
+                    </SheetTitle>
+                    {description ? (
+                      <SheetDescription className="text-muted-foreground text-xs">
+                        {description}
+                      </SheetDescription>
+                    ) : null}
+                  </div>
+                  <div className="shrink-0">{headerAction}</div>
+                </>
+              ) : (
+                <>
+                  <SheetTitle className="text-base font-semibold">
+                    {title}
+                  </SheetTitle>
+                  {description ? (
+                    <SheetDescription className="text-muted-foreground text-xs">
+                      {description}
+                    </SheetDescription>
+                  ) : null}
+                </>
+              )}
             </SheetHeader>
           )}
           <div
@@ -222,12 +253,29 @@ export function ResponsiveSheet({
         ) : (
           <DialogHeader
             data-slot="responsive-sheet-header"
-            className="shrink-0"
+            className={cn(
+              "shrink-0",
+              headerAction && "flex-row items-start justify-between gap-3 pr-9",
+            )}
           >
-            <DialogTitle>{title}</DialogTitle>
-            {description ? (
-              <DialogDescription>{description}</DialogDescription>
-            ) : null}
+            {headerAction ? (
+              <>
+                <div className="flex min-w-0 flex-1 flex-col gap-2">
+                  <DialogTitle>{title}</DialogTitle>
+                  {description ? (
+                    <DialogDescription>{description}</DialogDescription>
+                  ) : null}
+                </div>
+                <div className="shrink-0">{headerAction}</div>
+              </>
+            ) : (
+              <>
+                <DialogTitle>{title}</DialogTitle>
+                {description ? (
+                  <DialogDescription>{description}</DialogDescription>
+                ) : null}
+              </>
+            )}
           </DialogHeader>
         )}
         <div