Fix native chat anchoring while streaming

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

@@ -608,6 +608,47 @@ describe("bottom anchor controller driver", () => {
 
     expect(harness.driver.getSnapshot().mode).toBe("sticky-bottom");
   });
+
+  it("keeps native sticky content changes anchored when measured height is unchanged", () => {
+    const harness = createDriverHarness({
+      transportBehavior: {
+        verificationDelayFrames: 2,
+        verificationRetryMode: "recheck",
+      },
+      measurementState: createMeasurementState({
+        containerKey: "native-virtualized",
+        viewportWidth: 390,
+        viewportHeight: 546,
+        contentHeight: 546,
+        offsetY: 0,
+        viewportMeasuredForKey: "native-virtualized",
+        contentMeasuredForKey: "native-virtualized",
+      }),
+    });
+    harness.scrollToBottom.mockImplementation(() => {
+      harness.context.measurementState.offsetY = 0;
+      harness.context.nearBottom = true;
+    });
+
+    harness.driver.prepareForStickyContentChange();
+
+    expect(harness.scrollToBottom).toHaveBeenCalledTimes(1);
+    expect(harness.driver.getSnapshot()).toMatchObject({
+      mode: "sticky-bottom",
+      pendingVerification: {
+        requestId: null,
+      },
+    });
+
+    harness.context.measurementState.offsetY = 50;
+    harness.context.nearBottom = false;
+    harness.driver.handleScrollNearBottomChange({
+      nextIsNearBottom: false,
+      scrollDelta: 50,
+    });
+
+    expect(harness.driver.getSnapshot().mode).toBe("sticky-bottom");
+  });
 });
 
 describe("controller helper predicates", () => {

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

@@ -244,29 +244,6 @@ function createBottomAnchorControllerDriver(
   let stickyMeasurementRevision = 0;
   let lastVerifiedStickyMeasurementRevision = 0;
 
-  const _getLogContext = (extra?: Record<string, unknown>) => {
-    const measurementState = input.getMeasurementState();
-    const distanceFromBottom = Math.max(
-      0,
-      measurementState.contentHeight - (measurementState.offsetY + measurementState.viewportHeight),
-    );
-    return {
-      agentId: input.getAgentId(),
-      requestReason: pendingRequest?.reason ?? null,
-      authoritativeHistoryReady: input.getIsAuthoritativeHistoryReady(),
-      contentHeight: measurementState.contentHeight,
-      viewportHeight: measurementState.viewportHeight,
-      offset: measurementState.offsetY,
-      distanceFromBottom,
-      renderStrategy: input.getRenderStrategy(),
-      blockedReason,
-      mode,
-      containerKey: measurementState.containerKey,
-      transportBehavior: input.getTransportBehavior(),
-      ...extra,
-    };
-  };
-
   const setBlockedReason = (nextBlockedReason: BottomAnchorBlockedReason | null) => {
     if (blockedReason === nextBlockedReason) {
       return;
@@ -327,7 +304,6 @@ function createBottomAnchorControllerDriver(
     });
 
   const scheduleVerification = (attemptContext: AttemptContext, delayFramesOverride?: number) => {
-    const _scheduledMeasurementState = input.getMeasurementState();
     if (verificationHandle) {
       input.cancelFrame(verificationHandle);
     }
@@ -582,6 +558,16 @@ function createBottomAnchorControllerDriver(
         return;
       }
       markStickyMeasurementChanged();
+      if (!pendingRequest) {
+        pendingVerification = { requestId: null, retries: 0 };
+        if (attemptHandle) {
+          input.cancelFrame(attemptHandle);
+          attemptHandle = null;
+        }
+        runAttempt(false);
+        return;
+      }
+      evaluate(false, "content_size_change");
     },
     handleScrollNearBottomChange(params) {
       const { nextIsNearBottom, scrollDelta } = params;