diff --git a/apps/web/src/domains/chat/inspector/components/call-rail.tsx b/apps/web/src/domains/chat/inspector/components/call-rail.tsx
index b9fa7579e09..d030d6848ad 100644
--- a/apps/web/src/domains/chat/inspector/components/call-rail.tsx
+++ b/apps/web/src/domains/chat/inspector/components/call-rail.tsx
@@ -17,6 +17,16 @@ interface CallRailProps {
   logs: LLMRequestLogEntry[];
   selectedLogId: string | undefined;
   buildCallHref: (logId: string) => string;
+  /**
+   * Fires when a row is tapped, *before* `Link` navigation kicks in.
+   *
+   * The desktop rail lives in a persistent `<aside>` so it never needs
+   * to know when a selection was made. The mobile bottom-sheet wrapper
+   * (`mobile-call-selector.tsx`) hooks this to close itself once the
+   * user picks a call — the URL update alone wouldn't reset the sheet's
+   * local `open` state.
+   */
+  onSelect?: () => void;
 }
 
 /**
@@ -30,6 +40,7 @@ export function CallRail({
   logs,
   selectedLogId,
   buildCallHref,
+  onSelect,
 }: CallRailProps): ReactNode {
   if (!logs.length) {
     return (
@@ -60,6 +71,7 @@ export function CallRail({
           isSelected={entry.id === selectedLogId}
           isLatest={displayIndex === 0}
           href={buildCallHref(entry.id)}
+          onSelect={onSelect}
         />
       ))}
     </nav>
@@ -72,6 +84,7 @@ interface CallRowProps {
   isSelected: boolean;
   isLatest: boolean;
   href: string;
+  onSelect?: () => void;
 }
 
 function CallRow({
@@ -80,6 +93,7 @@ function CallRow({
   isSelected,
   isLatest,
   href,
+  onSelect,
 }: CallRowProps): ReactNode {
   const isSynthetic = isSyntheticAgentErrorMessage(entry);
   const subtitle = buildCallSubtitle(entry) ?? "Unrecognized call";
@@ -98,6 +112,7 @@ function CallRow({
   return (
     <Link
       to={href}
+      onClick={onSelect}
       aria-current={isSelected ? "page" : undefined}
       className="flex flex-col gap-1 rounded-md p-3 text-left no-underline transition-colors hover:opacity-90"
       style={{
diff --git a/apps/web/src/domains/chat/inspector/components/mobile-call-selector.test.tsx b/apps/web/src/domains/chat/inspector/components/mobile-call-selector.test.tsx
new file mode 100644
index 00000000000..507e4f262ae
--- /dev/null
+++ b/apps/web/src/domains/chat/inspector/components/mobile-call-selector.test.tsx
@@ -0,0 +1,108 @@
+/**
+ * Tests for the mobile-only call selector that replaces the desktop
+ * `<aside>` rail on narrow viewports.
+ *
+ * The selector wraps `CallRail` in a `BottomSheet`. In its closed state
+ * (the initial render) only the trigger button is in the markup; the
+ * sheet's content is portalled and only mounts when the user taps the
+ * trigger, so static-markup tests focus on the trigger's display
+ * contract.
+ *
+ * Strategy mirrors `call-rail.test.tsx`: `renderToStaticMarkup` with a
+ * `react-router` `Link` stub so the wrapped rail doesn't trip on a
+ * missing router context if/when it ends up in the tree.
+ */
+
+import { describe, expect, mock, test } from "bun:test";
+import { renderToStaticMarkup } from "react-dom/server";
+import type { ReactNode } from "react";
+
+import type { LLMRequestLogEntry } from "@vellumai/assistant-api";
+
+mock.module("react-router", () => ({
+  Link: ({
+    to,
+    children,
+    ...rest
+  }: {
+    to: string;
+    children: ReactNode;
+    [key: string]: unknown;
+  }) => (
+    <a href={to} {...rest}>
+      {children}
+    </a>
+  ),
+}));
+
+// Imported AFTER the mock so the component picks up the stub.
+import { MobileCallSelector } from "./mobile-call-selector";
+
+function makeEntry(
+  id: string,
+  createdAt: number,
+  overrides: Partial<LLMRequestLogEntry> = {},
+): LLMRequestLogEntry {
+  return {
+    id,
+    createdAt,
+    requestPayload: null,
+    responsePayload: null,
+    callSite: "mainAgent",
+    summary: {
+      provider: "anthropic",
+      model: "claude-sonnet-4",
+    },
+    ...overrides,
+  };
+}
+
+function render(
+  logs: LLMRequestLogEntry[],
+  selectedLogId: string | undefined,
+): string {
+  return renderToStaticMarkup(
+    <MobileCallSelector
+      logs={logs}
+      selectedLogId={selectedLogId}
+      buildCallHref={(id) => `/conv/test?callId=${id}`}
+    />,
+  );
+}
+
+describe("MobileCallSelector — trigger label", () => {
+  test("renders 'Call N of M' when a known call id is selected", () => {
+    // `logs` is oldest-first, so the call at index 1 is "Call 2 of 3".
+    const html = render(
+      [makeEntry("a", 1), makeEntry("b", 2), makeEntry("c", 3)],
+      "b",
+    );
+    expect(html).toContain("Call 2 of 3");
+  });
+
+  test("renders the latest call's position when no id is provided", () => {
+    // No selection means the inspector page will fall back to the
+    // newest call; the selector mirrors that by reporting `Call N of N`
+    // only when its `selectedLogId` prop actually matches a log. With
+    // an unknown id we expect the total-only fallback so the user is
+    // never lied to about which call is selected.
+    const html = render([makeEntry("a", 1), makeEntry("b", 2)], undefined);
+    expect(html).toContain("2 LLM calls");
+    expect(html).not.toContain("Call 0");
+  });
+
+  test("falls back to the total-only label when the selected id is stale", () => {
+    // Defensive: a `?callId=` in the URL that no longer matches any log
+    // shouldn't surface as "Call -1 of N" or similar nonsense.
+    const html = render([makeEntry("a", 1)], "missing");
+    expect(html).toContain("1 LLM call");
+    expect(html).not.toContain("Call ");
+  });
+
+  test("renders an accessible name on the trigger button", () => {
+    // Screen-reader users need a label that explains the surface this
+    // button opens — the visible text alone ("Call 1 of 1") doesn't.
+    const html = render([makeEntry("a", 1)], "a");
+    expect(html).toContain('aria-label="Select an LLM call to inspect"');
+  });
+});
diff --git a/apps/web/src/domains/chat/inspector/components/mobile-call-selector.tsx b/apps/web/src/domains/chat/inspector/components/mobile-call-selector.tsx
new file mode 100644
index 00000000000..ffb10e012d3
--- /dev/null
+++ b/apps/web/src/domains/chat/inspector/components/mobile-call-selector.tsx
@@ -0,0 +1,90 @@
+import { ChevronDown } from "lucide-react";
+import { useState, type ReactNode } from "react";
+
+import { BottomSheet } from "@vellum/design-library";
+import type { LLMRequestLogEntry } from "@vellumai/assistant-api";
+
+import { CallRail } from "./call-rail";
+
+interface MobileCallSelectorProps {
+  logs: LLMRequestLogEntry[];
+  selectedLogId: string | undefined;
+  buildCallHref: (logId: string) => string;
+}
+
+/**
+ * Mobile-only trigger + bottom sheet for selecting an LLM call.
+ *
+ * The desktop layout keeps the rail visible as a permanent `<aside>` next
+ * to the tab content. Mobile is too narrow to spare a column, so we
+ * surface a full-width pill at the top of the content area that shows
+ * the currently selected call and opens an overlay sheet listing every
+ * call in the conversation.
+ *
+ * The sheet closes itself after a row is tapped via `CallRail`'s
+ * `onSelect` callback — `?callId` URL changes alone don't reset the
+ * sheet's local `open` state.
+ */
+export function MobileCallSelector({
+  logs,
+  selectedLogId,
+  buildCallHref,
+}: MobileCallSelectorProps): ReactNode {
+  const [open, setOpen] = useState(false);
+
+  const total = logs.length;
+  // Identify the selected call's chronological position so the trigger
+  // can show "Call N of M" — the same numbering the rail uses. `logs`
+  // is ordered oldest-first; `callNumber = index + 1`.
+  const selectedIndex = selectedLogId
+    ? logs.findIndex((l) => l.id === selectedLogId)
+    : -1;
+  const callNumber = selectedIndex >= 0 ? selectedIndex + 1 : null;
+
+  const triggerLabel =
+    callNumber != null
+      ? `Call ${callNumber} of ${total}`
+      : total === 1
+        ? "1 LLM call"
+        : `${total} LLM calls`;
+
+  return (
+    <BottomSheet.Root open={open} onOpenChange={setOpen}>
+      <BottomSheet.Trigger asChild>
+        <button
+          type="button"
+          aria-label="Select an LLM call to inspect"
+          className="flex w-full shrink-0 items-center justify-between gap-2 px-4 py-2.5 text-left"
+          style={{
+            background: "var(--surface-base)",
+            borderBottom: "1px solid var(--border-base)",
+            color: "var(--content-default)",
+          }}
+        >
+          <span className="text-label-medium-default">{triggerLabel}</span>
+          <ChevronDown
+            size={16}
+            aria-hidden
+            style={{ color: "var(--content-secondary)" }}
+          />
+        </button>
+      </BottomSheet.Trigger>
+      <BottomSheet.Content className="max-h-[80dvh]">
+        <BottomSheet.Header>
+          <BottomSheet.Title>Select a call</BottomSheet.Title>
+        </BottomSheet.Header>
+        {/* Reset the sheet body's horizontal padding so the rail's own
+            row padding (`p-3` on each `CallRow`) matches the desktop
+            aside instead of double-padding on the left/right. */}
+        <BottomSheet.Body className="-mx-4 px-0">
+          <CallRail
+            logs={logs}
+            selectedLogId={selectedLogId}
+            buildCallHref={buildCallHref}
+            onSelect={() => setOpen(false)}
+          />
+        </BottomSheet.Body>
+      </BottomSheet.Content>
+    </BottomSheet.Root>
+  );
+}
diff --git a/apps/web/src/domains/chat/inspector/components/tab-bar.tsx b/apps/web/src/domains/chat/inspector/components/tab-bar.tsx
index c3af1e50562..353d960ab49 100644
--- a/apps/web/src/domains/chat/inspector/components/tab-bar.tsx
+++ b/apps/web/src/domains/chat/inspector/components/tab-bar.tsx
@@ -28,17 +28,23 @@ interface TabBarProps {
 
 export function TabBar({ selected, onSelect }: TabBarProps): ReactNode {
   return (
+    // Seven tabs overflow most phone viewports, so the row scrolls
+    // horizontally instead of getting clipped at the right edge. Each
+    // button keeps its label on one line via `whitespace-nowrap`.
     <div
-      className="flex shrink-0 px-4"
+      className="flex shrink-0 overflow-x-auto px-4"
       style={{ borderBottom: "1px solid var(--border-base)" }}
+      role="tablist"
     >
       {TABS.map((tab) => (
         <button
           key={tab.id}
           type="button"
+          role="tab"
+          aria-selected={selected === tab.id}
           onClick={() => onSelect(tab.id)}
           className={cn(
-            "-mb-px border-b-2 px-3 py-2 text-label-medium-default transition-colors",
+            "-mb-px shrink-0 whitespace-nowrap border-b-2 px-3 py-2 text-label-medium-default transition-colors",
             selected === tab.id
               ? "border-[var(--primary-base)] text-[var(--content-default)]"
               : "border-transparent text-[var(--content-secondary)] hover:text-[var(--content-default)]",
diff --git a/apps/web/src/domains/chat/inspector/inspect-page.test.tsx b/apps/web/src/domains/chat/inspector/inspect-page.test.tsx
index c70a9d6cdb4..70ec7832b48 100644
--- a/apps/web/src/domains/chat/inspector/inspect-page.test.tsx
+++ b/apps/web/src/domains/chat/inspector/inspect-page.test.tsx
@@ -304,6 +304,12 @@ describe("InspectPage — data-loading branches", () => {
     // Tab bar from the loaded path
     expect(html).toContain("Overview");
     expect(html).toContain("Prompt");
+    // The mobile call-selector trigger is mounted alongside the
+    // desktop aside (CSS hides whichever doesn't match the viewport).
+    // We rely on its trigger so phone users can pick a call when the
+    // aside is collapsed; the label shape is `Call N of M`.
+    expect(html).toContain("Call 2 of 2");
+    expect(html).toContain('aria-label="Select an LLM call to inspect"');
   });
 
   test("renders the error state when the context query errors out", () => {
diff --git a/apps/web/src/domains/chat/inspector/inspect-page.tsx b/apps/web/src/domains/chat/inspector/inspect-page.tsx
index 14902646282..6a33e6bb696 100644
--- a/apps/web/src/domains/chat/inspector/inspect-page.tsx
+++ b/apps/web/src/domains/chat/inspector/inspect-page.tsx
@@ -26,6 +26,7 @@ import { useAuthStore } from "@/stores/auth-store";
 import { routes } from "@/utils/routes";
 
 import { CallRail } from "./components/call-rail";
+import { MobileCallSelector } from "./components/mobile-call-selector";
 import { TabBar, type InspectorTab } from "./components/tab-bar";
 import { CompactionTab } from "./components/tabs/compaction-tab";
 import { MemoryTab } from "./components/tabs/memory-tab";
@@ -219,9 +220,16 @@ function Header({
     }
   }
 
+  // Mobile-responsive layout:
+  // - Desktop (≥md): Back · Title block · Export+count on one row.
+  // - Mobile (<md): Back · Export collapse to row 1; Title block wraps
+  //   to its own row via `order-3 w-full`. Avoids the title squeeze that
+  //   forced "LLM Context Inspector" to wrap inside ~120px on phones.
+  // The redundant call-count label is hidden on mobile — the
+  // `MobileCallSelector` pill in the content area already shows it.
   return (
     <div className="flex flex-col gap-2 px-4 py-3">
-      <div className="flex items-center gap-3">
+      <div className="flex flex-wrap items-center gap-3">
         <Button
           asChild
           variant="ghost"
@@ -235,9 +243,9 @@ function Header({
             Back
           </Link>
         </Button>
-        <div className="flex flex-1 flex-col">
+        <div className="order-3 flex w-full min-w-0 flex-col md:order-2 md:w-auto md:flex-1">
           <h1
-            className="text-title-medium"
+            className="truncate text-body-large-bold md:text-title-medium"
             style={{ color: "var(--content-default)" }}
           >
             LLM Context Inspector
@@ -247,7 +255,7 @@ function Header({
             messageId={messageId}
           />
         </div>
-        <div className="flex items-center gap-3">
+        <div className="order-2 ml-auto flex items-center gap-3 md:order-3 md:ml-0">
           <Button
             variant="outlined"
             size="compact"
@@ -258,7 +266,7 @@ function Header({
           >
             {isExporting ? "Exporting…" : "Export ZIP"}
           </Button>
-          <div className="flex flex-col items-end gap-0.5">
+          <div className="hidden flex-col items-end gap-0.5 md:flex">
             {callCount != null ? (
               <span
                 className="text-label-default"
@@ -278,6 +286,17 @@ function Header({
             ) : null}
           </div>
         </div>
+        {/* Mobile fallback for export errors — the desktop slot above is
+            hidden on narrow viewports so the error needs its own row. */}
+        {exportError ? (
+          <span
+            className="order-4 w-full text-body-small-default md:hidden"
+            role="alert"
+            style={{ color: "var(--system-negative-strong)" }}
+          >
+            {exportError}
+          </span>
+        ) : null}
       </div>
       <ScopeControls
         assistantId={assistantId}
@@ -478,6 +497,16 @@ function Loaded({
         />
       </aside>
       <main className="flex min-h-0 min-w-0 flex-1 flex-col">
+        {/* Mobile counterpart to the desktop aside. The wrapper hides
+            both the trigger button and the BottomSheet portal mount on
+            ≥md viewports — the aside above takes over there. */}
+        <div className="md:hidden">
+          <MobileCallSelector
+            logs={logs}
+            selectedLogId={selectedLogId}
+            buildCallHref={buildCallHref}
+          />
+        </div>
         <TabBar selected={tab} onSelect={setTab} />
         <div className="min-h-0 min-w-0 flex-1 overflow-y-auto">
           {selectedLog ? (