diff --git a/apps/client/src/features/ai-chat/components/ai-chat-window.tsx b/apps/client/src/features/ai-chat/components/ai-chat-window.tsx
index 7fb90456..28b42d76 100644
--- a/apps/client/src/features/ai-chat/components/ai-chat-window.tsx
+++ b/apps/client/src/features/ai-chat/components/ai-chat-window.tsx
@@ -50,7 +50,10 @@ import { shouldObserveRun } from "@/features/ai-chat/utils/run-polling.ts";
 import { workspaceAtom } from "@/features/user/atoms/current-user-atom";
 import ConversationList from "@/features/ai-chat/components/conversation-list.tsx";
 import ChatThread from "@/features/ai-chat/components/chat-thread.tsx";
-import { exportAiChat } from "@/features/ai-chat/services/ai-chat-service.ts";
+import {
+  exportAiChat,
+  stopRun,
+} from "@/features/ai-chat/services/ai-chat-service.ts";
 import { useChatSession } from "@/features/ai-chat/hooks/use-chat-session.ts";
 import {
   shouldCollapseOnOutsidePointer,
@@ -256,6 +259,39 @@ export default function AiChatWindow() {
     setLocalStreaming(streaming);
   }, []);
 
+  // #184 Stop wiring. While a detached run is being stopped we SUPPRESS the
+  // observer merge so the stopping run's still-persisting output does not
+  // re-stream back into view between the moment the user pressed Stop and the run
+  // actually settling as 'aborted' server-side. Polling itself keeps running (so
+  // the terminal transition is still detected) — only the visual merge is gated.
+  // Cleared when the run is observed terminal (below) or the chat is switched.
+  const [stoppingRun, setStoppingRun] = useState(false);
+  // Reset the stopping latch whenever the open chat changes: it is scoped to the
+  // run of the previously-open chat.
+  useEffect(() => {
+    setStoppingRun(false);
+  }, [activeChatId]);
+
+  // Authoritative stop of the open chat's detached run (the Stop button in
+  // autonomous mode). Latch "stopping" first (suppresses the re-stream flash),
+  // then request the server stop — the ONLY thing that ends a detached run; a mere
+  // local SSE abort is a client disconnect the server ignores. On failure we
+  // release the latch so the observer resumes (better to show the live run than to
+  // freeze the view) and surface the error.
+  const handleServerStop = useCallback(
+    (chatId: string): void => {
+      setStoppingRun(true);
+      void stopRun(chatId).catch(() => {
+        setStoppingRun(false);
+        notifications.show({
+          message: t("Failed to stop the run"),
+          color: "red",
+        });
+      });
+    },
+    [t],
+  );
+
   // Poll the latest run of the open chat ONLY when we are a passive observer:
   // feature on, a chat is open, and we are NOT the local streamer (the streamer
   // already has the live SSE — polling/merging too would double-render). The
@@ -269,9 +305,10 @@ export default function AiChatWindow() {
   // but only while we are an observer (never when we are the streamer — guards
   // against a stale poll fighting the live stream). Includes a terminal run so the
   // final persisted output is shown on reopen.
-  const observedRow = shouldObserveRun(run, localStreaming)
-    ? (runData?.message ?? null)
-    : null;
+  const observedRow =
+    shouldObserveRun(run, localStreaming) && !stoppingRun
+      ? (runData?.message ?? null)
+      : null;
 
   // When the observed run reaches a terminal status, do a final messages refetch
   // so the persisted final state (token/context badge, export source) is shown,
@@ -285,12 +322,24 @@ export default function AiChatWindow() {
       finalizedRunIdRef.current = null;
       return;
     }
+    // Terminal: a stop we requested has landed (or the run finished on its own),
+    // so release the stopping latch — the observer merge can now show the final
+    // persisted (aborted/finished) output without any live re-stream.
+    //
+    // But ONLY release once this tab is no longer the streamer. While
+    // `localStreaming` is true the run query is disabled, so `run` may be the
+    // PREVIOUS turn's terminal run held in the react-query cache, not the run we
+    // just asked to stop. Releasing the latch against that stale run would re-open
+    // the re-stream flash for the current turn the instant we switch to observer
+    // role. Gating on `!localStreaming` means the latch only clears against a run
+    // we are actually observing (the current turn's).
+    if (stoppingRun && !localStreaming) setStoppingRun(false);
     if (finalizedRunIdRef.current === run.id) return;
     finalizedRunIdRef.current = run.id;
     queryClient.invalidateQueries({
       queryKey: AI_CHAT_MESSAGES_RQ_KEY(activeChatId),
     });
-  }, [run, activeChatId, queryClient]);
+  }, [run, activeChatId, queryClient, stoppingRun, localStreaming]);
 
   // The page the user is currently viewing. AiChatWindow lives in a pathless
   // parent layout route, so useParams() can't see :pageSlug. Match the full
@@ -946,6 +995,12 @@ export default function AiChatWindow() {
               // while we are the streamer.
               observedRow={observedRow}
               onStreamingChange={onStreamingChange}
+              // #184: in autonomous mode the Stop button must hit the authoritative
+              // server stop (a local SSE abort is a client disconnect the server
+              // ignores). onServerStop also arms the "stopping" latch above so the
+              // stopped run's output does not re-stream via the observer merge.
+              autonomousRunsEnabled={autonomousRunsEnabled}
+              onServerStop={handleServerStop}
             />
           )}
         </div>
diff --git a/apps/client/src/features/ai-chat/components/chat-thread.tsx b/apps/client/src/features/ai-chat/components/chat-thread.tsx
index c9a0de20..c0fbbad9 100644
--- a/apps/client/src/features/ai-chat/components/chat-thread.tsx
+++ b/apps/client/src/features/ai-chat/components/chat-thread.tsx
@@ -100,6 +100,16 @@ interface ChatThreadProps {
    *  polling the run while WE are the active streamer (the SSE owns the view) and
    *  resume once we go idle. Called from an effect on every transition. */
   onStreamingChange?: (streaming: boolean) => void;
+  /** #184: whether detached/autonomous agent runs are enabled for this workspace.
+   *  When true the Stop button must additionally hit the AUTHORITATIVE server stop
+   *  (via onServerStop) — aborting only the local SSE is just a client disconnect,
+   *  which the server deliberately ignores, so the detached run would keep going. */
+  autonomousRunsEnabled?: boolean;
+  /** #184: request the server-side stop of this chat's active run (the parent owns
+   *  the endpoint call + the "stopping" latch that keeps observer-polling from
+   *  immediately re-streaming the stopping run's output). Called with the resolved
+   *  chat id when the user presses Stop in autonomous mode. */
+  onServerStop?: (chatId: string) => void;
 }
 
 /**
@@ -147,6 +157,8 @@ export default function ChatThread({
   onServerChatId,
   observedRow,
   onStreamingChange,
+  autonomousRunsEnabled,
+  onServerStop,
 }: ChatThreadProps) {
   const { t } = useTranslation();
 
@@ -446,6 +458,22 @@ export default function ChatThread({
     [setQueue, stop],
   );
 
+  // Stop the current turn. ALWAYS abort the local SSE (`stop()`) so the composer
+  // returns to idle immediately. In AUTONOMOUS mode the turn is a DETACHED run:
+  // aborting the local SSE is only a client disconnect, which the server ignores,
+  // so the run would keep executing — we ADDITIONALLY request the authoritative
+  // server-side stop (the parent owns that call + the "stopping" latch that keeps
+  // observer-polling from re-streaming the stopping run's output). The chat id is
+  // read live from chatIdRef (adopted early at the stream's `start` chunk); if it
+  // is not known yet — a brand-new chat in the first moment of its first turn —
+  // only the local abort happens (there is no server-side run handle to stop yet).
+  const handleStop = useCallback(() => {
+    stop();
+    if (autonomousRunsEnabled && chatIdRef.current) {
+      onServerStop?.(chatIdRef.current);
+    }
+  }, [stop, autonomousRunsEnabled, onServerStop]);
+
   // Clear the stopped marker as soon as a new turn begins streaming, and drop any
   // stale "Send now" interrupt flags. On the legit interrupt path both refs are
   // already consumed synchronously (onFinish + prepareSendMessagesRequest) before
@@ -576,7 +604,7 @@ export default function ChatThread({
         <ChatInput
           onSend={(text) => sendMessage({ text })}
           onQueue={enqueue}
-          onStop={stop}
+          onStop={handleStop}
           isStreaming={isStreaming}
         />
       </Stack>
diff --git a/apps/client/src/features/ai-chat/services/ai-chat-service.ts b/apps/client/src/features/ai-chat/services/ai-chat-service.ts
index fba0dfad..7dcf8b42 100644
--- a/apps/client/src/features/ai-chat/services/ai-chat-service.ts
+++ b/apps/client/src/features/ai-chat/services/ai-chat-service.ts
@@ -60,6 +60,21 @@ export async function getAiChatRun(
   return req.data;
 }
 
+/**
+ * Explicitly STOP the active agent run of a chat (#184). This is the ONLY thing
+ * that ends a DETACHED run — a mere browser disconnect (aborting the local SSE)
+ * is deliberately ignored server-side, so the client must call this to actually
+ * stop an autonomous run. Targeted by `chatId` (the server resolves whatever run
+ * is active on it); owner-gated server-side. Returns `{ stopped }` — false when
+ * there was nothing active to stop.
+ */
+export async function stopRun(
+  chatId: string,
+): Promise<{ stopped: boolean }> {
+  const req = await api.post<{ stopped: boolean }>("/ai-chat/stop", { chatId });
+  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.
diff --git a/apps/client/src/features/workspace/components/settings/components/ai-provider-settings.tsx b/apps/client/src/features/workspace/components/settings/components/ai-provider-settings.tsx
index 6e7cb185..1a0024ac 100644
--- a/apps/client/src/features/workspace/components/settings/components/ai-provider-settings.tsx
+++ b/apps/client/src/features/workspace/components/settings/components/ai-provider-settings.tsx
@@ -394,6 +394,10 @@ export default function AiProviderSettings() {
     useState<boolean>(
       workspace?.settings?.ai?.publicShareAssistant ?? false,
     );
+  // #184: detached/autonomous agent runs (settings.ai.autonomousRuns).
+  const [autonomousRunsEnabled, setAutonomousRunsEnabled] = useState<boolean>(
+    workspace?.settings?.ai?.autonomousRuns ?? false,
+  );
   const [chatToggleLoading, setChatToggleLoading] = useState(false);
   const [searchToggleLoading, setSearchToggleLoading] = useState(false);
   const [dictationToggleLoading, setDictationToggleLoading] = useState(false);
@@ -403,6 +407,8 @@ export default function AiProviderSettings() {
     publicShareAssistantToggleLoading,
     setPublicShareAssistantToggleLoading,
   ] = useState(false);
+  const [autonomousRunsToggleLoading, setAutonomousRunsToggleLoading] =
+    useState(false);
 
   // Whether a key is currently stored server-side (drives the placeholder).
   const [hasApiKey, setHasApiKey] = useState(false);
@@ -730,6 +736,37 @@ export default function AiProviderSettings() {
     }
   }
 
+  // Optimistic toggle for detached/autonomous agent runs
+  // (settings.ai.autonomousRuns). When on, a chat turn becomes a server-side run
+  // that survives a browser disconnect and can be reconnected to / live-followed;
+  // only an explicit Stop ends it. Off by default; single-instance-only in phase 1.
+  async function handleToggleAutonomousRuns(value: boolean) {
+    setAutonomousRunsToggleLoading(true);
+    const previous = autonomousRunsEnabled;
+    setAutonomousRunsEnabled(value);
+    try {
+      const updated = await updateWorkspace({ autonomousRuns: value });
+      setWorkspace({
+        ...updated,
+        settings: {
+          ...updated.settings,
+          ai: { ...updated.settings?.ai, autonomousRuns: value },
+        },
+      });
+      notifications.show({ message: t("Updated successfully") });
+    } catch (err) {
+      setAutonomousRunsEnabled(previous);
+      const message = (err as { response?: { data?: { message?: string } } })
+        ?.response?.data?.message;
+      notifications.show({
+        message: message ?? t("Failed to update data"),
+        color: "red",
+      });
+    } finally {
+      setAutonomousRunsToggleLoading(false);
+    }
+  }
+
   // Admins only — match the previous behavior.
   if (!isAdmin) {
     return (
@@ -960,6 +997,31 @@ export default function AiProviderSettings() {
           {...form.getInputProps("publicShareAssistantRoleId")}
         />
 
+        {/* Detached/autonomous agent runs: a chat turn becomes a server-side run
+            that survives a browser disconnect; only an explicit Stop ends it.
+            Single-instance-only in phase 1. */}
+        <Group justify="space-between" align="center" wrap="nowrap" mt="md">
+          <Stack gap={0}>
+            <Text fw={600} size="sm">
+              {t("Autonomous agent runs")}
+            </Text>
+            <Text size="xs" c="dimmed">
+              {t(
+                "Keep an agent turn running server-side even if the browser disconnects; reconnect and follow it on reopen. Single-instance deployments only.",
+              )}
+            </Text>
+          </Stack>
+          <Switch
+            label={t("Enabled")}
+            labelPosition="left"
+            checked={autonomousRunsEnabled}
+            disabled={autonomousRunsToggleLoading}
+            onChange={(e) =>
+              handleToggleAutonomousRuns(e.currentTarget.checked)
+            }
+          />
+        </Group>
+
         <Group mt="md" align="center">
           <Button
             variant="default"
diff --git a/apps/client/src/features/workspace/types/workspace.types.ts b/apps/client/src/features/workspace/types/workspace.types.ts
index f84eb550..b6881bd1 100644
--- a/apps/client/src/features/workspace/types/workspace.types.ts
+++ b/apps/client/src/features/workspace/types/workspace.types.ts
@@ -26,6 +26,9 @@ export interface IWorkspace {
   aiDictation?: boolean;
   aiDictationStreaming?: boolean;
   aiPublicShareAssistant?: boolean;
+  // Write-only field for updateWorkspace({ autonomousRuns }). Read state lives at
+  // settings.ai.autonomousRuns.
+  autonomousRuns?: boolean;
   trashRetentionDays?: number;
   // Default lifetime (HOURS) for new temporary notes; frozen per-note at creation.
   temporaryNoteHours?: number;
diff --git a/apps/server/src/core/ai-chat/ai-chat-run.service.ts b/apps/server/src/core/ai-chat/ai-chat-run.service.ts
index 5d11b202..b2e0d393 100644
--- a/apps/server/src/core/ai-chat/ai-chat-run.service.ts
+++ b/apps/server/src/core/ai-chat/ai-chat-run.service.ts
@@ -69,8 +69,10 @@ export interface RunHandle {
  * server-side lifecycle object detached from the HTTP request / browser window.
  *
  * Responsibilities:
- *  - create a run row when a turn starts (pending -> running) and register an
- *    in-memory AbortController for it (the explicit-stop lever);
+ *  - create a run row when a turn starts (inserted directly as 'running'; the
+ *    'pending' status is only the column default + a reserved value, never
+ *    written by code in phase 1) and register an in-memory AbortController for it
+ *    (the explicit-stop lever);
  *  - finalize the run row (succeeded / failed / aborted) and unregister it;
  *  - service an EXPLICIT user stop (`requestStop`) — the ONLY thing that aborts a
  *    run; a browser disconnect deliberately does NOT;
diff --git a/apps/server/src/core/workspace/dto/update-workspace.dto.ts b/apps/server/src/core/workspace/dto/update-workspace.dto.ts
index a7d91ca4..7e4989a7 100644
--- a/apps/server/src/core/workspace/dto/update-workspace.dto.ts
+++ b/apps/server/src/core/workspace/dto/update-workspace.dto.ts
@@ -55,6 +55,14 @@ export class UpdateWorkspaceDto extends PartialType(CreateWorkspaceDto) {
   @IsBoolean()
   aiDictationStreaming: boolean;
 
+  // #184: detached/autonomous agent runs (settings.ai.autonomousRuns). When on, a
+  // chat turn becomes a server-side RUN that survives a browser disconnect; only
+  // an explicit /ai-chat/stop ends it. Off by default; single-instance-only in
+  // phase 1 (see AiChatRunService.warnIfMultiInstance / AGENTS.md).
+  @IsOptional()
+  @IsBoolean()
+  autonomousRuns: boolean;
+
   // Workspace master toggle that enables/disables the HTML embed block type.
   // Persisted at settings.htmlEmbed. ABSENT/false => OFF (default). The block
   // itself renders in a sandboxed iframe, so this is a feature switch, not a
diff --git a/apps/server/src/core/workspace/services/workspace.service.ts b/apps/server/src/core/workspace/services/workspace.service.ts
index 14c1ea88..e217ee74 100644
--- a/apps/server/src/core/workspace/services/workspace.service.ts
+++ b/apps/server/src/core/workspace/services/workspace.service.ts
@@ -526,6 +526,20 @@ export class WorkspaceService {
         );
       }
 
+      if (typeof updateWorkspaceDto.autonomousRuns !== 'undefined') {
+        const prev = settingsBefore?.ai?.autonomousRuns ?? false;
+        if (prev !== updateWorkspaceDto.autonomousRuns) {
+          before.autonomousRuns = prev;
+          after.autonomousRuns = updateWorkspaceDto.autonomousRuns;
+        }
+        await this.workspaceRepo.updateAiSettings(
+          workspaceId,
+          'autonomousRuns',
+          updateWorkspaceDto.autonomousRuns,
+          trx,
+        );
+      }
+
       if (typeof updateWorkspaceDto.htmlEmbed !== 'undefined') {
         const prev = settingsBefore?.htmlEmbed ?? false;
         if (prev !== updateWorkspaceDto.htmlEmbed) {
@@ -579,6 +593,7 @@ export class WorkspaceService {
       delete updateWorkspaceDto.aiChat;
       delete updateWorkspaceDto.aiDictation;
       delete updateWorkspaceDto.aiDictationStreaming;
+      delete updateWorkspaceDto.autonomousRuns;
       delete updateWorkspaceDto.htmlEmbed;
       delete updateWorkspaceDto.trackerHead;
       delete updateWorkspaceDto.aiPublicShareAssistant;
diff --git a/apps/server/src/database/migrations/20260627T130000-ai-chat-runs.ts b/apps/server/src/database/migrations/20260627T130000-ai-chat-runs.ts
index 78b1c178..94888c42 100644
--- a/apps/server/src/database/migrations/20260627T130000-ai-chat-runs.ts
+++ b/apps/server/src/database/migrations/20260627T130000-ai-chat-runs.ts
@@ -7,8 +7,10 @@ import { type Kysely, sql } from 'kysely';
  * Until now an agent turn lived ONLY as long as the HTTP request was open
  * (`res.hijack()` in ai-chat.controller.ts); a browser disconnect aborted it.
  * This table makes a turn a persistent object the server owns: it is created
- * when a run starts, transitions pending -> running -> succeeded|failed|aborted,
- * and survives the subscriber (browser) going away. The DB is the source of
+ * when a run starts (inserted directly as 'running' in phase 1 — 'pending' is
+ * only this column's default + a reserved value, never written by code yet) and
+ * advances to succeeded|failed|aborted, surviving the subscriber (browser) going
+ * away when it settles. The DB is the source of
  * truth — a later client reconnects/sees the result by reading this row plus the
  * assistant message it projects (`assistant_message_id`).
  *