diff --git a/apps/web/src/app/accounts/[id]/page.tsx b/apps/web/src/app/accounts/[id]/page.tsx
index 7f211ef..966a0f9 100644
--- a/apps/web/src/app/accounts/[id]/page.tsx
+++ b/apps/web/src/app/accounts/[id]/page.tsx
@@ -131,31 +131,34 @@ export default async function AccountDetailPage({ params }: AccountDetailPagePro
               </Card>
             </Link>
 
-            {/* Unpair — entire card opens the confirm dialog */}
+            {/* Unpair — transparent <button> overlay opens the dialog
+                so we don't pass button-specific props onto the Card div
+                (Radix asChild does that and it produces a hydration
+                mismatch on a div). */}
             <Dialog>
-              <DialogTrigger asChild>
-                <Card
-                  role="button"
-                  tabIndex={0}
-                  aria-label="Unpair WhatsApp"
-                  className="transition-all hover:shadow-md hover:ring-amber-500/30 cursor-pointer focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2"
-                >
-                  <CardContent className="flex items-center justify-between gap-4 py-4">
-                    <div className="flex items-center gap-3">
-                      <div className="flex size-9 items-center justify-center rounded-lg bg-amber-500/10">
-                        <PowerOffIcon className="size-4 text-amber-600 dark:text-amber-400" />
-                      </div>
-                      <div>
-                        <p className="text-sm font-medium">Unpair</p>
-                        <p className="text-xs text-muted-foreground">
-                          Disconnect from WhatsApp; keep the account so you can re-pair later
-                        </p>
-                      </div>
+              <Card className="relative transition-all hover:shadow-md hover:ring-amber-500/30 cursor-pointer">
+                <CardContent className="flex items-center justify-between gap-4 py-4">
+                  <div className="flex items-center gap-3">
+                    <div className="flex size-9 items-center justify-center rounded-lg bg-amber-500/10">
+                      <PowerOffIcon className="size-4 text-amber-600 dark:text-amber-400" />
                     </div>
-                    <ChevronRightIcon className="size-4 text-muted-foreground/60" />
-                  </CardContent>
-                </Card>
-              </DialogTrigger>
+                    <div>
+                      <p className="text-sm font-medium">Unpair</p>
+                      <p className="text-xs text-muted-foreground">
+                        Disconnect from WhatsApp; keep the account so you can re-pair later
+                      </p>
+                    </div>
+                  </div>
+                  <ChevronRightIcon className="size-4 text-muted-foreground/60" />
+                </CardContent>
+                <DialogTrigger asChild>
+                  <button
+                    type="button"
+                    aria-label="Unpair WhatsApp"
+                    className="absolute inset-0 w-full rounded-xl bg-transparent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2"
+                  />
+                </DialogTrigger>
+              </Card>
               <DialogContent>
                 <DialogHeader>
                   <DialogTitle>Unpair this account?</DialogTitle>
@@ -179,31 +182,31 @@ export default async function AccountDetailPage({ params }: AccountDetailPagePro
           </>
         )}
 
-        {/* Delete — entire card opens the confirm dialog */}
+        {/* Delete — transparent <button> overlay opens the dialog. */}
         <Dialog>
-          <DialogTrigger asChild>
-            <Card
-              role="button"
-              tabIndex={0}
-              aria-label="Delete account"
-              className="transition-all hover:shadow-md hover:ring-destructive/30 cursor-pointer focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-destructive focus-visible:ring-offset-2"
-            >
-              <CardContent className="flex items-center justify-between gap-4 py-4">
-                <div className="flex items-center gap-3">
-                  <div className="flex size-9 items-center justify-center rounded-lg bg-destructive/10">
-                    <Trash2Icon className="size-4 text-destructive" />
-                  </div>
-                  <div>
-                    <p className="text-sm font-medium text-destructive">Delete Account</p>
-                    <p className="text-xs text-muted-foreground">
-                      Remove the account and all its reminders, groups, and history
-                    </p>
-                  </div>
+          <Card className="relative transition-all hover:shadow-md hover:ring-destructive/30 cursor-pointer">
+            <CardContent className="flex items-center justify-between gap-4 py-4">
+              <div className="flex items-center gap-3">
+                <div className="flex size-9 items-center justify-center rounded-lg bg-destructive/10">
+                  <Trash2Icon className="size-4 text-destructive" />
                 </div>
-                <ChevronRightIcon className="size-4 text-muted-foreground/60" />
-              </CardContent>
-            </Card>
-          </DialogTrigger>
+                <div>
+                  <p className="text-sm font-medium text-destructive">Delete Account</p>
+                  <p className="text-xs text-muted-foreground">
+                    Remove the account and all its reminders, groups, and history
+                  </p>
+                </div>
+              </div>
+              <ChevronRightIcon className="size-4 text-muted-foreground/60" />
+            </CardContent>
+            <DialogTrigger asChild>
+              <button
+                type="button"
+                aria-label="Delete account"
+                className="absolute inset-0 w-full rounded-xl bg-transparent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-destructive focus-visible:ring-offset-2"
+              />
+            </DialogTrigger>
+          </Card>
           <DialogContent>
             <DialogHeader>
               <DialogTitle>Delete this account permanently?</DialogTitle>
diff --git a/apps/web/src/components/accounts-list-view.test.tsx b/apps/web/src/components/accounts-list-view.test.tsx
index a3174f4..415234b 100644
--- a/apps/web/src/components/accounts-list-view.test.tsx
+++ b/apps/web/src/components/accounts-list-view.test.tsx
@@ -109,20 +109,21 @@ describe("AccountsListView", () => {
       expect(html).toMatch(/<strong>MyBiz<\/strong>/);
     });
 
-    it("delete card is a focusable trigger element with the destructive aria-label", () => {
+    it("delete card uses a real <button> overlay (not a div with role=button)", () => {
       const html = renderToStaticMarkup(
         <AccountsListView
           accounts={[mkAccount({ label: "Sales" })]}
           deleteFormAction={noopAction}
         />,
       );
-      // The trigger is a Card (rendered as <div>) acting as a button via
-      // role+tabIndex. Wrapping a <div> in a real <button> would be
-      // invalid HTML and trigger a hydration mismatch.
-      expect(html).toMatch(/role="button"/);
-      expect(html).toMatch(/tabIndex="0"|tabindex="0"/);
+      // The visible Card stays a <div>; a real <button type="button">
+      // overlays it. Putting a <div> inside a <button> would be invalid
+      // HTML, and Radix's `asChild` injecting button props onto a <div>
+      // would mismatch SSR vs client. The overlay sidesteps both.
+      expect(html).toMatch(
+        /<button[^>]*type="button"[^>]*data-testid="account-delete-card"|<button[^>]*data-testid="account-delete-card"[^>]*type="button"/,
+      );
       expect(html).toMatch(/aria-label="Delete Sales"/);
-      expect(html).toMatch(/data-testid="account-delete-card"/);
       // `Delete account` heading copy lives inside the card
       expect(html).toContain("Delete account");
     });
diff --git a/apps/web/src/components/accounts-list-view.tsx b/apps/web/src/components/accounts-list-view.tsx
index 952d993..295cd03 100644
--- a/apps/web/src/components/accounts-list-view.tsx
+++ b/apps/web/src/components/accounts-list-view.tsx
@@ -107,34 +107,34 @@ export function AccountsListView({ accounts, deleteFormAction }: AccountsListVie
               </Link>
 
               {/* Dedicated Delete card — entire card is the dialog trigger.
-                  We avoid wrapping the Card (a <div>) in a <button> because
-                  div-inside-button is invalid HTML and the browser auto-
-                  closes the button, breaking SSR hydration. Radix's
-                  DialogTrigger asChild forwards the click handler to the
-                  Card element directly; role="button"+tabIndex makes it
-                  keyboard-focusable. */}
+                  We use a transparent <button> overlay instead of passing
+                  the Card as `asChild` to DialogTrigger: Radix injects
+                  `type="button"` and other button-specific props onto its
+                  child, which on a <div> mismatches between SSR and the
+                  client tree. Putting a real <button> over the card keeps
+                  the visible Card as a <div> with valid attributes. */}
               <Dialog>
-                <DialogTrigger asChild>
-                  <Card
-                    role="button"
-                    tabIndex={0}
-                    data-testid="account-delete-card"
-                    aria-label={`Delete ${account.label}`}
-                    className="transition-all hover:shadow-md hover:ring-destructive/30 cursor-pointer focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-destructive focus-visible:ring-offset-2"
-                  >
-                    <CardContent className="flex items-center gap-3 py-3 px-4">
-                      <div className="flex size-8 shrink-0 items-center justify-center rounded-lg bg-destructive/10">
-                        <Trash2Icon className="size-4 text-destructive" />
-                      </div>
-                      <div className="min-w-0 flex-1">
-                        <p className="text-sm font-medium text-destructive">Delete account</p>
-                        <p className="text-xs text-muted-foreground truncate">
-                          Remove {account.label} and its reminders & groups
-                        </p>
-                      </div>
-                    </CardContent>
-                  </Card>
-                </DialogTrigger>
+                <Card className="relative transition-all hover:shadow-md hover:ring-destructive/30 cursor-pointer">
+                  <CardContent className="flex items-center gap-3 py-3 px-4">
+                    <div className="flex size-8 shrink-0 items-center justify-center rounded-lg bg-destructive/10">
+                      <Trash2Icon className="size-4 text-destructive" />
+                    </div>
+                    <div className="min-w-0 flex-1">
+                      <p className="text-sm font-medium text-destructive">Delete account</p>
+                      <p className="text-xs text-muted-foreground truncate">
+                        Remove {account.label} and its reminders & groups
+                      </p>
+                    </div>
+                  </CardContent>
+                  <DialogTrigger asChild>
+                    <button
+                      type="button"
+                      data-testid="account-delete-card"
+                      aria-label={`Delete ${account.label}`}
+                      className="absolute inset-0 w-full rounded-xl bg-transparent focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-destructive focus-visible:ring-offset-2"
+                    />
+                  </DialogTrigger>
+                </Card>
                 <DialogContent>
                   <DialogHeader>
                     <DialogTitle>Delete this account?</DialogTitle>
diff --git a/apps/web/src/components/reminder-edit/edit-account-form.tsx b/apps/web/src/components/reminder-edit/edit-account-form.tsx
index 354d752..77e0ec8 100644
--- a/apps/web/src/components/reminder-edit/edit-account-form.tsx
+++ b/apps/web/src/components/reminder-edit/edit-account-form.tsx
@@ -95,51 +95,53 @@ export function EditAccountForm({
             const active = account.id === selected;
             const connected = account.status === "connected";
             return (
-              <button
+              <Card
                 key={account.id}
-                type="button"
-                onClick={() => setSelected(account.id)}
+                role="button"
+                tabIndex={0}
                 aria-pressed={active}
+                aria-label={`Use ${account.label}`}
+                onClick={() => setSelected(account.id)}
+                onKeyDown={(e) => {
+                  if (e.key === "Enter" || e.key === " ") {
+                    e.preventDefault();
+                    setSelected(account.id);
+                  }
+                }}
                 className={cn(
-                  "block w-full text-left rounded-xl focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2",
+                  "transition-all rounded-xl focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2",
+                  active
+                    ? "ring-2 ring-primary/60"
+                    : "hover:shadow-md hover:ring-primary/30 cursor-pointer",
+                  !connected && "opacity-70",
                 )}
               >
-                <Card
-                  className={cn(
-                    "transition-all",
-                    active
-                      ? "ring-2 ring-primary/60"
-                      : "hover:shadow-md hover:ring-primary/30 cursor-pointer",
-                    !connected && "opacity-70",
-                  )}
-                >
-                  <CardContent className="flex items-center gap-3 py-3 px-4">
-                    <div
-                      className={cn(
-                        "flex size-9 shrink-0 items-center justify-center rounded-lg",
-                        connected
-                          ? "bg-emerald-500/10 text-emerald-600 dark:text-emerald-400"
-                          : "bg-muted text-muted-foreground",
-                      )}
-                    >
-                      <SmartphoneIcon className="size-4" />
-                    </div>
-                    <div className="min-w-0 flex-1">
-                      <p className="text-sm font-medium leading-snug truncate">
-                        {account.label}
-                      </p>
-                      <p className="text-xs text-muted-foreground truncate">
-                        {account.phoneNumber ?? "Not paired"}
-                      </p>
-                    </div>
-                    {connected ? (
-                      <WifiIcon className="size-4 text-emerald-500 shrink-0" />
-                    ) : (
-                      <WifiOffIcon className="size-4 text-muted-foreground/50 shrink-0" />
+                <CardContent className="flex items-center gap-3 py-3 px-4">
+                  <div
+                    className={cn(
+                      "flex size-9 shrink-0 items-center justify-center rounded-lg",
+                      connected
+                        ? "bg-emerald-500/10 text-emerald-600 dark:text-emerald-400"
+                        : "bg-muted text-muted-foreground",
                     )}
-                  </CardContent>
-                </Card>
-              </button>
+                  >
+                    <SmartphoneIcon className="size-4" />
+                  </div>
+                  <div className="min-w-0 flex-1">
+                    <p className="text-sm font-medium leading-snug truncate">
+                      {account.label}
+                    </p>
+                    <p className="text-xs text-muted-foreground truncate">
+                      {account.phoneNumber ?? "Not paired"}
+                    </p>
+                  </div>
+                  {connected ? (
+                    <WifiIcon className="size-4 text-emerald-500 shrink-0" />
+                  ) : (
+                    <WifiOffIcon className="size-4 text-muted-foreground/50 shrink-0" />
+                  )}
+                </CardContent>
+              </Card>
             );
           })}
         </div>
diff --git a/apps/web/src/test/no-button-wrapping-card.test.ts b/apps/web/src/test/no-button-wrapping-card.test.ts
new file mode 100644
index 0000000..eb48f83
--- /dev/null
+++ b/apps/web/src/test/no-button-wrapping-card.test.ts
@@ -0,0 +1,103 @@
+import { describe, it, expect } from "vitest";
+import { readdirSync, readFileSync, statSync } from "node:fs";
+import { join, relative } from "node:path";
+
+/**
+ * Static guard: no `.tsx` file may contain a literal `<button` element
+ * wrapping a `<Card`, `<CardContent`, or `<CardHeader` (the shadcn
+ * primitives that render `<div>`).
+ *
+ * That nesting is invalid HTML — `<button>`'s content model is phrasing
+ * content, and `<div>` is flow content. Browsers auto-close the button
+ * when they hit the inner div; React 19 SSR doesn't, and the resulting
+ * tree mismatch raised "Hydration failed" in production. We use Card
+ * directly as the trigger now (DialogTrigger asChild forwards the
+ * click) or place a transparent submit button as a sibling.
+ *
+ * We scan for the lowercase `<button` only — `<Button>` (shadcn's
+ * styled component) is fine; it just renders a real `<button>` with no
+ * children. `<button>` followed by `<Card>` within a few hundred
+ * characters is the smell.
+ */
+
+const SRC_ROOT = join(__dirname, "..");
+
+function listTsxFiles(dir: string): string[] {
+  const out: string[] = [];
+  for (const entry of readdirSync(dir)) {
+    const full = join(dir, entry);
+    const st = statSync(full);
+    if (st.isDirectory()) {
+      out.push(...listTsxFiles(full));
+    } else if (entry.endsWith(".tsx")) {
+      out.push(full);
+    }
+  }
+  return out;
+}
+
+interface Hit {
+  file: string;
+  line: number;
+  excerpt: string;
+}
+
+function findHits(content: string): Array<{ line: number; excerpt: string }> {
+  const hits: Array<{ line: number; excerpt: string }> = [];
+  // For every opening `<button` (lowercase), grab everything up to its
+  // matching `</button>` and look for a Card primitive opener inside.
+  const cardOpener = /<(?:Card|CardContent|CardHeader)\b/;
+  let cursor = 0;
+  while (cursor < content.length) {
+    const open = content.indexOf("<button", cursor);
+    if (open === -1) break;
+    // Skip JSX comments, attribute-substring matches like `<buttonish`, etc.
+    const next = content.charAt(open + "<button".length);
+    if (next && /[a-zA-Z0-9]/.test(next)) {
+      cursor = open + 1;
+      continue;
+    }
+    const close = content.indexOf("</button>", open);
+    if (close === -1) break;
+    const segment = content.slice(open, close);
+    if (cardOpener.test(segment)) {
+      const line = content.slice(0, open).split("\n").length;
+      hits.push({ line, excerpt: segment.slice(0, 160).replace(/\s+/g, " ") });
+    }
+    cursor = close + "</button>".length;
+  }
+  return hits;
+}
+
+describe("static guard: no <button> wrapping a Card primitive", () => {
+  const files = listTsxFiles(SRC_ROOT)
+    // Test files describe and document patterns; they may legitimately
+    // contain regex strings that mention `<button>` and `<Card>` together.
+    .filter((f) => !/\.test\.tsx?$/.test(f));
+
+  it("scans at least one source file (sanity)", () => {
+    expect(files.length).toBeGreaterThan(0);
+  });
+
+  it("finds no <button>…<Card> nesting in any production .tsx file", () => {
+    const allHits: Hit[] = [];
+    for (const file of files) {
+      const content = readFileSync(file, "utf8");
+      for (const h of findHits(content)) {
+        allHits.push({ file: relative(SRC_ROOT, file), ...h });
+      }
+    }
+    if (allHits.length > 0) {
+      const message = allHits
+        .map((h) => `  ${h.file}:${h.line} → ${h.excerpt}`)
+        .join("\n");
+      throw new Error(
+        `Invalid HTML nesting detected — <button> wraps a Card primitive:\n${message}\n` +
+          `Card renders a <div>, which is flow content and not allowed inside <button>.\n` +
+          `Use Card directly as DialogTrigger asChild's child, or place a transparent\n` +
+          `<button type="submit"> as a sibling that overlays the card.`,
+      );
+    }
+    expect(allHits).toEqual([]);
+  });
+});
diff --git a/apps/web/src/test/no-render-warnings.test.tsx b/apps/web/src/test/no-render-warnings.test.tsx
new file mode 100644
index 0000000..36c67cf
--- /dev/null
+++ b/apps/web/src/test/no-render-warnings.test.tsx
@@ -0,0 +1,192 @@
+import { describe, it, expect, vi } from "vitest";
+import { renderToString } from "react-dom/server";
+import type { ReactNode, ReactElement } from "react";
+
+/**
+ * Guard: server-rendering critical surfaces must not produce ANY
+ * console.error or console.warn from React. The most common sources are:
+ *
+ *  - Invalid HTML nesting (e.g. <div> inside <button>) — this is exactly
+ *    what produced the recent "Hydration failed" runtime error.
+ *  - Two children with the same `key`.
+ *  - "Encountered a script tag while rendering React component" — a
+ *    React 19 warning when a `<script>` appears inside the React tree
+ *    rather than `<head>`.
+ *
+ * We can't fully reproduce *runtime* hydration in a Node test, but
+ * `renderToString` runs React's SSR-time validation, which catches
+ * these structural issues during the same render that would later
+ * mismatch in the browser.
+ */
+
+// --- Mocks for next/link + the radix primitives we use --------------------
+// These are deliberately TRANSPARENT (render children) so the underlying
+// element tree we care about (button vs div nesting, etc.) reaches React's
+// validator unchanged.
+
+vi.mock("next/link", () => ({
+  default: ({ href, children, ...rest }: { href: string; children: ReactNode } & Record<string, unknown>) => (
+    <a href={href} {...rest}>
+      {children}
+    </a>
+  ),
+}));
+
+vi.mock("@/components/ui/dialog", () => ({
+  Dialog: ({ children }: { children: ReactNode }) => <>{children}</>,
+  DialogTrigger: ({ children }: { children: ReactNode; asChild?: boolean }) => <>{children}</>,
+  DialogContent: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  DialogHeader: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  DialogTitle: ({ children }: { children: ReactNode }) => <h2>{children}</h2>,
+  DialogDescription: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  DialogFooter: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+}));
+
+import { AccountsListView, type AccountsListAccount } from "@/components/accounts-list-view";
+import { EditMessageForm } from "@/components/reminder-edit/edit-message-form";
+
+// next-themes / radix dropdown mocks for ThemeToggle.
+const useThemeReturn: { theme: string | undefined; setTheme: () => void } = {
+  theme: "system",
+  setTheme: () => {},
+};
+vi.mock("next-themes", () => ({
+  useTheme: () => useThemeReturn,
+}));
+vi.mock("@/components/ui/dropdown-menu", () => ({
+  DropdownMenu: ({ children }: { children: ReactNode }) => <>{children}</>,
+  DropdownMenuTrigger: ({ children }: { children: ReactNode; asChild?: boolean }) => <>{children}</>,
+  DropdownMenuContent: ({ children }: { children: ReactNode }) => <div>{children}</div>,
+  DropdownMenuItem: ({ children }: { children: ReactNode }) => (
+    <div role="menuitem">{children}</div>
+  ),
+}));
+
+// next/navigation is touched by the edit form's useRouter().
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({ push: () => {} }),
+}));
+
+// Mock the server action import inside EditMessageForm so importing it
+// doesn't try to wire up the real action machinery.
+vi.mock("@/actions/reminders", () => ({
+  updateReminderAction: () => Promise.resolve({ ok: true, reminderId: "r-1" }),
+}));
+
+import { ThemeToggle } from "@/components/theme-toggle";
+
+// Helper: render with console.error / console.warn captured. Restores the
+// originals via vi.restoreAllMocks at end of each test.
+function renderQuiet(node: ReactElement): { html: string; errors: unknown[][]; warns: unknown[][] } {
+  const errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+  const warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+  const html = renderToString(node);
+  const errors = errorSpy.mock.calls;
+  const warns = warnSpy.mock.calls;
+  errorSpy.mockRestore();
+  warnSpy.mockRestore();
+  return { html, errors, warns };
+}
+
+const account: AccountsListAccount = {
+  id: "a-1",
+  label: "Personal",
+  status: "connected",
+  phoneNumber: "+60123456789",
+  lastConnectedAt: new Date("2026-05-01T10:00:00Z"),
+};
+
+describe("SSR render — no React errors or warnings", () => {
+  it("AccountsListView (populated) renders cleanly", () => {
+    const { errors, warns } = renderQuiet(
+      <AccountsListView accounts={[account]} deleteFormAction={() => {}} />,
+    );
+    expect(errors).toEqual([]);
+    expect(warns).toEqual([]);
+  });
+
+  it("AccountsListView (empty) renders cleanly", () => {
+    const { errors, warns } = renderQuiet(
+      <AccountsListView accounts={[]} deleteFormAction={() => {}} />,
+    );
+    expect(errors).toEqual([]);
+    expect(warns).toEqual([]);
+  });
+
+  it("ThemeToggle renders cleanly across all theme values", () => {
+    for (const t of ["light", "dark", "system", undefined]) {
+      useThemeReturn.theme = t;
+      const { errors, warns } = renderQuiet(<ThemeToggle />);
+      expect(errors, `console.error during theme=${t}`).toEqual([]);
+      expect(warns, `console.warn during theme=${t}`).toEqual([]);
+    }
+  });
+
+  it("EditMessageForm renders cleanly (text-only and media-attached)", () => {
+    const baseProps = {
+      reminderId: "r-1",
+      accountId: "acc-1",
+      groupIds: ["g-1"],
+      scheduledAtIso: "2026-05-13T09:00:00.000+08:00",
+      rrule: "FREQ=DAILY",
+      timezone: "Asia/Kuala_Lumpur",
+      initialText: "Hello",
+      initialMediaId: null as string | null,
+      initialCaption: "",
+    };
+    const a = renderQuiet(<EditMessageForm {...baseProps} />);
+    expect(a.errors).toEqual([]);
+    expect(a.warns).toEqual([]);
+
+    const b = renderQuiet(
+      <EditMessageForm
+        {...baseProps}
+        initialMediaId="m-1"
+        initialCaption="caption text"
+      />,
+    );
+    expect(b.errors).toEqual([]);
+    expect(b.warns).toEqual([]);
+  });
+});
+
+describe("SSR markup — no <div> inside <button> (the bug we just fixed)", () => {
+  it("AccountsListView never nests a div inside a button", () => {
+    const { html } = renderQuiet(
+      <AccountsListView accounts={[account]} deleteFormAction={() => {}} />,
+    );
+    // Naive but effective: scan each <button>...</button> region for any
+    // <div, <p, or <h-tag inside. Those are flow content and not allowed
+    // inside a button per the HTML spec — browsers auto-close the button
+    // and the SSR/client trees diverge.
+    const buttons = [...html.matchAll(/<button\b[^>]*>([\s\S]*?)<\/button>/g)];
+    for (const m of buttons) {
+      const inner = m[1] ?? "";
+      expect(
+        /<(?:div|p|h[1-6])\b/.test(inner),
+        `Invalid nesting inside <button>: ${inner.slice(0, 200)}`,
+      ).toBe(false);
+    }
+  });
+
+  it("EditMessageForm never nests a div inside a button", () => {
+    const { html } = renderQuiet(
+      <EditMessageForm
+        reminderId="r-1"
+        accountId="acc-1"
+        groupIds={["g-1"]}
+        scheduledAtIso="2026-05-13T09:00:00.000+08:00"
+        rrule={null}
+        timezone="Asia/Kuala_Lumpur"
+        initialText="Hello"
+        initialMediaId={null}
+        initialCaption=""
+      />,
+    );
+    const buttons = [...html.matchAll(/<button\b[^>]*>([\s\S]*?)<\/button>/g)];
+    for (const m of buttons) {
+      const inner = m[1] ?? "";
+      expect(/<(?:div|p|h[1-6])\b/.test(inner)).toBe(false);
+    }
+  });
+});