diff --git a/src/app/chat/hooks/__tests__/chat-keyboard-geometry.test.ts b/src/app/chat/hooks/__tests__/chat-keyboard-geometry.test.ts
index cc746e55..99e82a28 100644
--- a/src/app/chat/hooks/__tests__/chat-keyboard-geometry.test.ts
+++ b/src/app/chat/hooks/__tests__/chat-keyboard-geometry.test.ts
@@ -84,27 +84,36 @@ describe("resolveChatKeyboardInset", () => {
 
 describe("resolveChatKeyboardFallbackInset", () => {
   it.each([
-    [{ layoutWidth: 320, layoutHeight: 568 }, 256],
-    [{ layoutWidth: 360, layoutHeight: 640 }, 285],
-    [{ layoutWidth: 390, layoutHeight: 844 }, 316],
-    [{ layoutWidth: 430, layoutHeight: 932 }, 347],
+    [{ layoutWidth: 320, layoutHeight: 568 }, 260],
+    [{ layoutWidth: 360, layoutHeight: 640 }, 291],
+    [{ layoutWidth: 390, layoutHeight: 844 }, 344],
+    [{ layoutWidth: 430, layoutHeight: 932 }, 356],
   ])("fits common viewport %o", (viewport, expectedInset) => {
     expect(resolveChatKeyboardFallbackInset(viewport)).toBe(expectedInset);
   });
 
+  it("covers the reported 392 by 760 Facebook viewport", () => {
+    expect(
+      resolveChatKeyboardFallbackInset({
+        layoutWidth: 392,
+        layoutHeight: 760,
+      }),
+    ).toBe(343);
+  });
+
   it("stays stable across tall viewports with the same width", () => {
     expect(
       resolveChatKeyboardFallbackInset({
         layoutWidth: 390,
         layoutHeight: 760,
       }),
-    ).toBe(316);
+    ).toBe(343);
     expect(
       resolveChatKeyboardFallbackInset({
         layoutWidth: 390,
         layoutHeight: 900,
       }),
-    ).toBe(316);
+    ).toBe(344);
   });
 
   it("keeps the keyboard estimate within its bounds", () => {
diff --git a/src/app/chat/hooks/__tests__/use-chat-keyboard-avoidance.test.tsx b/src/app/chat/hooks/__tests__/use-chat-keyboard-avoidance.test.tsx
index 89603f8c..7fbce4f7 100644
--- a/src/app/chat/hooks/__tests__/use-chat-keyboard-avoidance.test.tsx
+++ b/src/app/chat/hooks/__tests__/use-chat-keyboard-avoidance.test.tsx
@@ -104,7 +104,7 @@ describe("useChatKeyboardAvoidance", () => {
     expect(getBottomInset(container)).toBe("");
 
     act(() => vi.advanceTimersByTime(1));
-    expect(getBottomInset(container)).toBe("316px");
+    expect(getBottomInset(container)).toBe("344px");
     expect(intervalSpy).not.toHaveBeenCalled();
   });
 
@@ -188,7 +188,7 @@ describe("useChatKeyboardAvoidance", () => {
     renderHarness(root, false);
     renderHarness(root, true);
     act(() => vi.advanceTimersByTime(150));
-    expect(getBottomInset(container)).toBe("316px");
+    expect(getBottomInset(container)).toBe("344px");
 
     visualViewport.height = 500;
     act(() => {
@@ -203,7 +203,7 @@ describe("useChatKeyboardAvoidance", () => {
     renderHarness(root, false);
     renderHarness(root, true);
     act(() => vi.advanceTimersByTime(150));
-    expect(getBottomInset(container)).toBe("316px");
+    expect(getBottomInset(container)).toBe("344px");
 
     renderHarness(root, false);
 
diff --git a/src/app/chat/hooks/chat-keyboard-geometry.ts b/src/app/chat/hooks/chat-keyboard-geometry.ts
index e3dd4c3a..5a980b26 100644
--- a/src/app/chat/hooks/chat-keyboard-geometry.ts
+++ b/src/app/chat/hooks/chat-keyboard-geometry.ts
@@ -1,8 +1,8 @@
 export const CHAT_KEYBOARD_VISIBLE_THRESHOLD_PX = 80;
 export const CHAT_KEYBOARD_ZOOM_THRESHOLD = 1.05;
 export const CHAT_KEYBOARD_TARGET_GAP_PX = 16;
-export const CHAT_KEYBOARD_FALLBACK_WIDTH_RATIO = 0.77;
-export const CHAT_KEYBOARD_FALLBACK_HEIGHT_RATIO = 0.42;
+export const CHAT_KEYBOARD_FALLBACK_WIDTH_RATIO = 0.84;
+export const CHAT_KEYBOARD_FALLBACK_HEIGHT_RATIO = 0.43;
 export const CHAT_KEYBOARD_FALLBACK_MIN_PX = 240;
 export const CHAT_KEYBOARD_FALLBACK_MAX_PX = 340;