fix(app): keep chat scrollable during streaming

Continuous Android stream updates kept bottom-anchor verification pending, so genuine finger drags were mistaken for programmatic corrections. Preserve explicit drag ownership so user scrolling can detach immediately.

packages/app/src/agent-stream/bottom-anchor-controller.test.ts

@@ -774,4 +774,18 @@ describe("controller helper predicates", () => {
       }),
     ).toBe(true);
   });
+
+  it("lets an active user drag override pending sticky verification", () => {
+    expect(
+      __private__.shouldDetachFromScrollAway({
+        mode: "sticky-bottom",
+        nextIsNearBottom: false,
+        scrollDelta: 48,
+        hasPendingRequest: false,
+        hasPendingVerification: true,
+        hasUnverifiedStickyMeasurementChange: true,
+        isUserScroll: true,
+      }),
+    ).toBe(true);
+  });
 });

packages/app/src/agent-stream/bottom-anchor-controller.ts

@@ -84,6 +84,7 @@ interface BottomAnchorControllerDriver {
   handleScrollNearBottomChange: (params: {
     nextIsNearBottom: boolean;
     scrollDelta: number;
+    isUserScroll?: boolean;
   }) => void;
   notifyAuthoritativeHistoryMaybeChanged: () => void;
   reevaluate: (animated?: boolean) => void;
@@ -570,7 +571,7 @@ function createBottomAnchorControllerDriver(
       evaluate(false, "content_size_change");
     },
     handleScrollNearBottomChange(params) {
-      const { nextIsNearBottom, scrollDelta } = params;
+      const { nextIsNearBottom, scrollDelta, isUserScroll = false } = params;
       if (
         nextIsNearBottom &&
         mode === "sticky-bottom" &&
@@ -588,6 +589,7 @@ function createBottomAnchorControllerDriver(
           hasPendingRequest: pendingRequest !== null,
           hasPendingVerification: pendingVerification !== null,
           hasUnverifiedStickyMeasurementChange,
+          isUserScroll,
         })
       ) {
         this.detachByUser();
@@ -657,14 +659,16 @@ export const __private__ = {
     hasPendingRequest: boolean;
     hasPendingVerification: boolean;
     hasUnverifiedStickyMeasurementChange: boolean;
+    isUserScroll?: boolean;
   }): boolean {
     const scrolledAwayIntentionally = Math.abs(input.scrollDelta) >= USER_SCROLL_AWAY_DELTA_PX;
     return (
       input.mode === "sticky-bottom" &&
       !input.nextIsNearBottom &&
-      !input.hasPendingRequest &&
-      !input.hasPendingVerification &&
-      (!input.hasUnverifiedStickyMeasurementChange || scrolledAwayIntentionally)
+      (input.isUserScroll ||
+        (!input.hasPendingRequest &&
+          !input.hasPendingVerification &&
+          (!input.hasUnverifiedStickyMeasurementChange || scrolledAwayIntentionally)))
     );
   },
 };
@@ -758,7 +762,11 @@ export function useBottomAnchorController(input: {
     prepareForStickyContentChange() {
       driverRef.current?.prepareForStickyContentChange();
     },
-    handleScrollNearBottomChange(params: { nextIsNearBottom: boolean; scrollDelta: number }) {
+    handleScrollNearBottomChange(params: {
+      nextIsNearBottom: boolean;
+      scrollDelta: number;
+      isUserScroll?: boolean;
+    }) {
       driverRef.current?.handleScrollNearBottomChange(params);
     },
     reevaluate(animated = false) {

packages/app/src/agent-stream/strategy-native.tsx

@@ -89,6 +89,7 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     contentMeasuredForKey: null as string | null,
   });
   const scrollOffsetYRef = useRef(0);
+  const isUserScrollActiveRef = useRef(false);
   const programmaticScrollEventBudgetRef = useRef(0);
   const [isNativeViewportSettling, setIsNativeViewportSettling] = useState(false);
   const nativeViewportSettlingFrameIdRef = useRef<number | null>(null);
@@ -208,6 +209,7 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
       contentMeasuredForKey: null,
     };
     scrollOffsetYRef.current = 0;
+    isUserScrollActiveRef.current = false;
     clearNativeViewportSettling();
     setIsNativeViewportSettling(false);
     historyStartReadyRef.current = false;
@@ -308,10 +310,27 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
       bottomAnchorController.handleScrollNearBottomChange({
         nextIsNearBottom: nearBottom,
         scrollDelta: contentOffset.y - previousOffsetY,
+        isUserScroll: isUserScrollActiveRef.current,
       });
     }
   });
 
+  const handleScrollBeginDrag = useStableEvent(() => {
+    isUserScrollActiveRef.current = true;
+  });
+
+  const handleScrollEndDrag = useStableEvent(() => {
+    isUserScrollActiveRef.current = false;
+  });
+
+  const handleMomentumScrollBegin = useStableEvent(() => {
+    isUserScrollActiveRef.current = true;
+  });
+
+  const handleMomentumScrollEnd = useStableEvent(() => {
+    isUserScrollActiveRef.current = false;
+  });
+
   const handleListLayout = useStableEvent((event: LayoutChangeEvent) => {
     const previousViewportWidth = streamViewportMetricsRef.current.viewportWidth;
     const previousViewportHeight = streamViewportMetricsRef.current.viewportHeight;
@@ -419,6 +438,10 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
       style={listStyle}
       onLayout={handleListLayout}
       onScroll={handleScroll}
+      onScrollBeginDrag={handleScrollBeginDrag}
+      onScrollEndDrag={handleScrollEndDrag}
+      onMomentumScrollBegin={handleMomentumScrollBegin}
+      onMomentumScrollEnd={handleMomentumScrollEnd}
       scrollEventThrottle={16}
       onContentSizeChange={handleContentSizeChange}
       maintainVisibleContentPosition={maintainVisibleContentPosition}