diff --git a/src/app/(repairs-app)/repairs-app/layout.tsx b/src/app/(repairs-app)/repairs-app/layout.tsx
index 579cb5f..f628158 100644
--- a/src/app/(repairs-app)/repairs-app/layout.tsx
+++ b/src/app/(repairs-app)/repairs-app/layout.tsx
@@ -6,11 +6,13 @@ import { RepairsTabBar } from "./tab-bar";
 /**
  * Repairs phone-app shell.
  *
- * The fourth instance of the per-route-group PWA pattern already running
- * here (`/m` boss phone, `/counter` till, `/rep` rep visits), so it
- * reuses `MobileAuthGate` and gets its own manifest + service worker.
+ * The fifth instance of the per-route-group PWA pattern already running
+ * here (`/m` boss phone, `/counter` till, `/manager` orders, `/rep` rep
+ * visits), so it reuses `MobileAuthGate` and gets its own manifest +
+ * service worker.
  *
- * Deliberately not in the sidebar — matching `/m`, `/counter` and `/rep`.
+ * Deliberately not in the sidebar — matching `/m`, `/counter`, `/manager`
+ * and `/rep`.
  * The repairs person installs this on their home screen and never
  * navigates to it from a menu.
  */
diff --git a/src/app/(repairs-app)/repairs-app/tab-bar.test.tsx b/src/app/(repairs-app)/repairs-app/tab-bar.test.tsx
index 9acdd04..6b5517c 100644
--- a/src/app/(repairs-app)/repairs-app/tab-bar.test.tsx
+++ b/src/app/(repairs-app)/repairs-app/tab-bar.test.tsx
@@ -1,6 +1,6 @@
 import { describe, it, expect, vi } from "vitest";
 import { render, screen } from "@testing-library/react";
-import { RepairsTabBar } from "./tab-bar";
+import { RepairsTabBar, pickActiveTabHref } from "./tab-bar";
 
 vi.mock("next/navigation", () => ({
   usePathname: () => "/repairs-app",
@@ -13,8 +13,33 @@ describe("RepairsTabBar", () => {
     expect(link).toHaveAttribute("href", "/repairs-app");
   });
 
-  it("has no dead controls — every element is a link", () => {
+  it("has no dead controls — every control is a link with a real destination", () => {
     render(<RepairsTabBar />);
     expect(screen.queryAllByRole("button")).toHaveLength(0);
+    const links = screen.getAllByRole("link");
+    expect(links.length).toBeGreaterThan(0);
+    for (const link of links) {
+      const href = link.getAttribute("href");
+      expect(href).toBeTruthy();
+      expect(href).not.toBe("#");
+    }
+  });
+
+  it("marks only the most specific tab as the current page", () => {
+    // The Phase-4 shape, proven without shipping the Phase-4 tab.
+    const tabs = [
+      { href: "/repairs-app", label: "Repairs" },
+      { href: "/repairs-app/giellie", label: "Ask Giellie" },
+    ];
+    expect(pickActiveTabHref("/repairs-app", tabs)).toBe("/repairs-app");
+    expect(pickActiveTabHref("/repairs-app/book-in", tabs)).toBe("/repairs-app");
+    expect(pickActiveTabHref("/repairs-app/giellie", tabs)).toBe("/repairs-app/giellie");
+    expect(pickActiveTabHref("/repairs-app/giellie/chat", tabs)).toBe("/repairs-app/giellie");
+  });
+
+  it("does not claim a lookalike route as the Repairs tab", () => {
+    const tabs = [{ href: "/repairs-app" }];
+    expect(pickActiveTabHref("/repairs-approval", tabs)).toBeUndefined();
+    expect(pickActiveTabHref("/repairs", tabs)).toBeUndefined();
   });
 });
diff --git a/src/app/(repairs-app)/repairs-app/tab-bar.tsx b/src/app/(repairs-app)/repairs-app/tab-bar.tsx
index 2f2dfcc..47a1c6a 100644
--- a/src/app/(repairs-app)/repairs-app/tab-bar.tsx
+++ b/src/app/(repairs-app)/repairs-app/tab-bar.tsx
@@ -14,8 +14,36 @@ import { usePathname } from "next/navigation";
  */
 const TABS = [{ href: "/repairs-app", label: "Repairs" }];
 
+/**
+ * The active tab is the one whose href is the LONGEST match for the
+ * current path.
+ *
+ * Phase 4 puts the chat tab at `/repairs-app/giellie`, which also starts
+ * with `/repairs-app` — so a plain `startsWith` would let both tabs claim to be
+ * the current page. Two elements carrying `aria-current="page"` is a broken
+ * state, and colour would be the only thing telling them apart, which
+ * this app must never rely on.
+ *
+ * A path matches a tab when it is the tab's href exactly, or when it
+ * continues past that href on a segment boundary: `/repairs-app/book-in` matches
+ * `/repairs-app`, `/repairs-approval` does not.
+ */
+export function pickActiveTabHref(
+  pathname: string,
+  tabs: { href: string }[] = TABS
+): string | undefined {
+  let best: string | undefined;
+  for (const tab of tabs) {
+    const { href } = tab;
+    if (pathname !== href && !pathname.startsWith(href + "/")) continue;
+    if (best === undefined || href.length > best.length) best = href;
+  }
+  return best;
+}
+
 export function RepairsTabBar() {
   const pathname = usePathname();
+  const activeHref = pickActiveTabHref(pathname, TABS);
   return (
     <nav
       aria-label="Sections"
@@ -24,7 +52,7 @@ export function RepairsTabBar() {
     >
       <ul className="flex">
         {TABS.map((tab) => {
-          const active = pathname.startsWith(tab.href);
+          const active = activeHref === tab.href;
           return (
             <li key={tab.href} className="flex-1">
               <Link
diff --git a/src/app/offline.tsx b/src/app/offline/page.tsx
similarity index 100%
rename from src/app/offline.tsx
rename to src/app/offline/page.tsx
diff --git a/src/components/service-worker-registration.test.ts b/src/components/service-worker-registration.test.ts
new file mode 100644
index 0000000..444c8de
--- /dev/null
+++ b/src/components/service-worker-registration.test.ts
@@ -0,0 +1,49 @@
+import { describe, it, expect } from "vitest";
+import { pickSwPath } from "./service-worker-registration";
+
+/**
+ * The picker decides which worker a phone installs for a given route.
+ * The risk it must never have is one route shadowing another —
+ * `/repairs-app` and `/rep` share their first four characters — so the
+ * mapping is pinned here rather than left to a comment.
+ */
+function swFor(pathname: string): string {
+  window.history.pushState({}, "", pathname);
+  return pickSwPath();
+}
+
+describe("pickSwPath", () => {
+  it("picks the repairs-app worker for every route inside /repairs-app", () => {
+    for (const path of [
+      "/repairs-app",
+      "/repairs-app/",
+      "/repairs-app/book-in",
+      "/repairs-app/giellie",
+    ]) {
+      expect(swFor(path)).toBe("/sw-repairs-app.js");
+    }
+  });
+
+  it("picks the rep worker for /rep and its sub-routes", () => {
+    expect(swFor("/rep")).toBe("/sw-rep.js");
+    expect(swFor("/rep/visits")).toBe("/sw-rep.js");
+  });
+
+  it("never lets one of the two shadow the other", () => {
+    expect(swFor("/rep")).not.toBe("/sw-repairs-app.js");
+    expect(swFor("/repairs-app")).not.toBe("/sw-rep.js");
+    expect(swFor("/repairs")).toBe("/sw.js");
+  });
+
+  it("leaves the other PWA routes on their own workers", () => {
+    expect(swFor("/m")).toBe("/sw-mobile.js");
+    expect(swFor("/counter")).toBe("/sw-counter.js");
+    expect(swFor("/new-order")).toBe("/sw-counter.js");
+    expect(swFor("/manager")).toBe("/sw-manager.js");
+  });
+
+  it("falls back to the main app worker everywhere else", () => {
+    expect(swFor("/")).toBe("/sw.js");
+    expect(swFor("/quotes")).toBe("/sw.js");
+  });
+});
diff --git a/src/components/service-worker-registration.tsx b/src/components/service-worker-registration.tsx
index 2c901f9..3b8c026 100644
--- a/src/components/service-worker-registration.tsx
+++ b/src/components/service-worker-registration.tsx
@@ -15,7 +15,7 @@ import { useEffect } from "react";
  * All SWs are scoped to `/` so co-existence is fine — they each
  * cache their own URLs and ignore `/api/`.
  */
-function pickSwPath(): string {
+export function pickSwPath(): string {
   if (typeof window === "undefined") return "/sw.js";
   const path = window.location.pathname;
   if (path === "/m" || path.startsWith("/m/")) {