diff --git a/src/components/ClinicalDashboard.tsx b/src/components/ClinicalDashboard.tsx
index 49ba42517..e5b3e2118 100644
--- a/src/components/ClinicalDashboard.tsx
+++ b/src/components/ClinicalDashboard.tsx
@@ -5546,6 +5546,9 @@ export function ClinicalDashboard({
           mobileSearchPlacement={hasMobileBottomSearch ? "bottom" : "default"}
           desktopHomeComposerSlotId={desktopHomeComposerSlotId}
           heroComposerFromTablet={Boolean(desktopHomeComposerSlotId)}
+          // Phone-only: the header sits above the internally scrolling <main>,
+          // so hiding must collapse its layout space to hand it to content.
+          hideOnScroll={{ strategy: "collapse", containerRef: mainRef }}
         />
 
         <main
diff --git a/src/components/clinical-dashboard/global-mockup-search-shell.tsx b/src/components/clinical-dashboard/global-mockup-search-shell.tsx
index 98edfc237..9ef81b5ea 100644
--- a/src/components/clinical-dashboard/global-mockup-search-shell.tsx
+++ b/src/components/clinical-dashboard/global-mockup-search-shell.tsx
@@ -329,7 +329,11 @@ function GlobalMockupSearchShellClient({
       ) : null}
 
       <div className="flex min-h-dvh min-w-0 flex-col">
-        <div className={cn(!mobileChromeVisible && "hidden lg:block")}>
+        {/* max-sm:contents lets the header's own `sticky top-0` engage against
+            the document scroll on phones (a plain wrapper div otherwise caps
+            its sticking range at its own height), which the phone
+            hide-on-scroll overlay relies on. */}
+        <div className={mobileChromeVisible ? "max-sm:contents" : "hidden lg:block"}>
           <MasterSearchHeader
             documents={[]}
             documentTotal={0}
@@ -369,6 +373,9 @@ function GlobalMockupSearchShellClient({
             searchComposerVisible={shouldShowSearchComposer}
             desktopHomeComposerSlotId={isStandaloneModeHome ? modeHomeDesktopComposerSlotId : undefined}
             heroComposerFromTablet={isStandaloneModeHome}
+            // Phone-only: the document scrolls here and the header is sticky,
+            // so a translate overlay hides it with zero layout shift.
+            hideOnScroll={{ strategy: "overlay" }}
           />
         </div>
 
diff --git a/src/components/clinical-dashboard/master-search-header.tsx b/src/components/clinical-dashboard/master-search-header.tsx
index 99cbde6b4..4041e4254 100644
--- a/src/components/clinical-dashboard/master-search-header.tsx
+++ b/src/components/clinical-dashboard/master-search-header.tsx
@@ -7,8 +7,10 @@ import {
   useMemo,
   useRef,
   useState,
+  type FocusEvent as ReactFocusEvent,
   type KeyboardEvent as ReactKeyboardEvent,
   type Ref,
+  type RefObject,
 } from "react";
 import { createPortal } from "react-dom";
 
@@ -45,6 +47,7 @@ import {
 
 import { DocumentTagCloud } from "@/components/DocumentTagCloud";
 import { useDismissableLayer } from "@/components/use-dismissable-layer";
+import { useHideOnScroll } from "@/components/clinical-dashboard/use-hide-on-scroll";
 import {
   ModeActionPopup,
   modeActionItemsFor,
@@ -208,6 +211,7 @@ export function MasterSearchHeader({
   heroComposerFromTablet = false,
   mobileLeadingAction = "menu",
   onMobileBack,
+  hideOnScroll,
 }: {
   documents: ClinicalDocument[];
   documentTotal?: number;
@@ -247,6 +251,12 @@ export function MasterSearchHeader({
   heroComposerFromTablet?: boolean;
   mobileLeadingAction?: "menu" | "back";
   onMobileBack?: () => void;
+  /** Phone-only hide-on-scroll for the universal header. "overlay" translates
+   *  the sticky header away (host scrolls the document, content already flows
+   *  beneath); "collapse" also releases the header's layout space (host keeps
+   *  the header above an internally scrolling element). `containerRef` points
+   *  at the scrolling element; omit it to observe window scroll. */
+  hideOnScroll?: { strategy: "overlay" | "collapse"; containerRef?: RefObject<HTMLElement | null> };
 }) {
   const visibleAppModeOptions = defaultVisibleAppModeOptions;
   const trimmedQuery = query.trim();
@@ -279,6 +289,16 @@ export function MasterSearchHeader({
   const [usesScopeSheet, setUsesScopeSheet] = useState(false);
   const [usesPhoneSearchLayout, setUsesPhoneSearchLayout] = useState(false);
   const [desktopHomeComposerActive, setDesktopHomeComposerActive] = useState(false);
+  // Phone-only hide-on-scroll: never hide while a header-owned surface is open
+  // or while focus sits inside the header chrome (keyboard users must not tab
+  // into invisible controls).
+  const [headerChromeFocused, setHeaderChromeFocused] = useState(false);
+  const scrollHidden = useHideOnScroll({
+    containerRef: hideOnScroll?.containerRef,
+    disabled: !hideOnScroll,
+  });
+  const headerChromeHidden =
+    scrollHidden && !modeMenuOpen && !actionMenuOpen && !scopeOpen && !scopeSheetOpen && !headerChromeFocused;
   // Stable, header-owned element the composer is portaled into; we move it in and
   // out of the page-owned slot rather than portaling into the slot directly.
   const [desktopHomeComposerHost, setDesktopHomeComposerHost] = useState<HTMLDivElement | null>(null);
@@ -1361,13 +1381,32 @@ export function MasterSearchHeader({
     );
   }
 
-  return (
+  const hideStrategy = hideOnScroll?.strategy;
+  const chromeFocusProps = hideOnScroll
+    ? {
+        onFocusCapture: () => setHeaderChromeFocused(true),
+        onBlurCapture: (event: ReactFocusEvent<HTMLElement>) => {
+          if (!event.currentTarget.contains(event.relatedTarget as Node | null)) setHeaderChromeFocused(false);
+        },
+      }
+    : undefined;
+
+  const headerAndComposer = (
     <>
       <header
         id="search"
         className={cn(
           "edge-glass-header universal-header sticky top-0 z-30 border-b border-[color:var(--border)] py-2 pt-[max(0.5rem,env(safe-area-inset-top))] text-[color:var(--text)] backdrop-blur-xl",
+          // Overlay hide-on-scroll (phones): the header is sticky over document
+          // scroll, so a plain translate reveals the content already flowing
+          // beneath it with zero layout shift. No transform is applied while
+          // visible so the fixed-position mobile mode menu keeps the viewport
+          // as its containing block.
+          hideStrategy === "overlay" &&
+            "max-sm:transition-transform max-sm:duration-200 max-sm:ease-out motion-reduce:transition-none",
+          hideStrategy === "overlay" && headerChromeHidden && "max-sm:-translate-y-full",
         )}
+        {...(hideStrategy === "overlay" ? chromeFocusProps : undefined)}
       >
         <div
           className={cn(
@@ -1552,4 +1591,36 @@ export function MasterSearchHeader({
       ) : null}
     </>
   );
+
+  if (hideStrategy === "collapse") {
+    // Collapse hide-on-scroll (phones): the host renders the header above an
+    // internally scrolling element, so hiding must also release the header's
+    // layout space. A 1fr -> 0fr grid row animates the collapse without any
+    // height measurement; the bottom-anchored inner track makes the chrome
+    // slide up out of the viewport top. Fixed-position composers (answer
+    // footer, mobile bottom search) escape the wrapper naturally because it
+    // never carries a transform, and everything is inert from sm up.
+    return (
+      <div
+        className={cn(
+          "max-sm:grid max-sm:transition-[grid-template-rows] max-sm:duration-200 max-sm:ease-out motion-reduce:transition-none",
+          headerChromeHidden ? "max-sm:[grid-template-rows:0fr]" : "max-sm:[grid-template-rows:1fr]",
+        )}
+        {...chromeFocusProps}
+      >
+        <div
+          className={cn(
+            "max-sm:flex max-sm:min-h-0 max-sm:flex-col max-sm:justify-end",
+            // Clip only while hiding so the edge-glass-header gradient that
+            // extends below the header keeps painting when the chrome is shown.
+            headerChromeHidden && "max-sm:overflow-hidden",
+          )}
+        >
+          {headerAndComposer}
+        </div>
+      </div>
+    );
+  }
+
+  return headerAndComposer;
 }
diff --git a/src/components/clinical-dashboard/use-hide-on-scroll.ts b/src/components/clinical-dashboard/use-hide-on-scroll.ts
new file mode 100644
index 000000000..90549e40e
--- /dev/null
+++ b/src/components/clinical-dashboard/use-hide-on-scroll.ts
@@ -0,0 +1,98 @@
+"use client";
+
+import { useEffect, useState, useSyncExternalStore, type RefObject } from "react";
+
+// Matches phoneSearchLayoutMediaQuery in master-search-header.tsx — the repo's
+// phone/tablet seam. Hide-on-scroll only ever runs below the sm breakpoint.
+const phoneMediaQuery = "(max-width: 639px)";
+
+// Scroll offset (px) that must be passed before the chrome may hide; roughly
+// the header's own height so it never vanishes while still fully in view.
+const hideActivationOffset = 56;
+// Offset (px) at or below which the chrome is always shown.
+const topRevealOffset = 8;
+// Minimum per-event delta (px) before we treat movement as intentional, to
+// avoid jitter from momentum settling and fractional scroll positions.
+const minimumDelta = 4;
+
+function subscribeToPhoneMedia(onChange: () => void) {
+  const media = window.matchMedia(phoneMediaQuery);
+  media.addEventListener("change", onChange);
+  return () => media.removeEventListener("change", onChange);
+}
+
+function readPhoneMedia() {
+  return window.matchMedia(phoneMediaQuery).matches;
+}
+
+function readPhoneMediaServer() {
+  return false;
+}
+
+interface UseHideOnScrollOptions {
+  /**
+   * Element that owns the scrolling. When omitted the window/document scroll
+   * position is observed instead.
+   */
+  containerRef?: RefObject<HTMLElement | null>;
+  /** Disables the behavior entirely (state resets to visible). */
+  disabled?: boolean;
+}
+
+/**
+ * Tracks scroll direction on phones and reports when top chrome (the
+ * universal header) should hide to maximise content space. Hidden while
+ * scrolling down past the header, shown again on any deliberate scroll up or
+ * when near the top. Inert (always visible) above the phone breakpoint.
+ */
+export function useHideOnScroll({ containerRef, disabled = false }: UseHideOnScrollOptions): boolean {
+  const [hidden, setHidden] = useState(false);
+  const isPhone = useSyncExternalStore(subscribeToPhoneMedia, readPhoneMedia, readPhoneMediaServer);
+  const active = isPhone && !disabled;
+
+  useEffect(() => {
+    if (!active) return;
+
+    const container = containerRef?.current ?? null;
+    const target: HTMLElement | Window = container ?? window;
+    const readOffset = () => (container ? container.scrollTop : window.scrollY);
+
+    let lastOffset = readOffset();
+    let frame = 0;
+
+    const evaluate = () => {
+      frame = 0;
+      const offset = readOffset();
+      // Ignore iOS rubber-band overscroll at the top.
+      if (offset < 0) return;
+      const delta = offset - lastOffset;
+      if (offset <= topRevealOffset) {
+        lastOffset = offset;
+        setHidden(false);
+        return;
+      }
+      if (Math.abs(delta) < minimumDelta) return;
+      lastOffset = offset;
+      if (delta > 0) {
+        if (offset > hideActivationOffset) setHidden(true);
+      } else {
+        setHidden(false);
+      }
+    };
+
+    const onScroll = () => {
+      if (frame) return;
+      frame = window.requestAnimationFrame(evaluate);
+    };
+
+    target.addEventListener("scroll", onScroll, { passive: true });
+    return () => {
+      target.removeEventListener("scroll", onScroll);
+      if (frame) window.cancelAnimationFrame(frame);
+      // Leaving the phone breakpoint (or unmounting) always restores the chrome.
+      setHidden(false);
+    };
+  }, [active, containerRef]);
+
+  return active && hidden;
+}